lodel Propeller NOISE three preceding articles discussing findings ex haustive prop noise study conducted North Carolina State University sponsored AMA has demonstrated average commercial propeller inefficient major source model airplane noise engine properly muf fled What can done solve problem discussed concluding segment ER Vess D Heathcoat R Nagel THE PREVIOUS articles four-part series have shown propellers main source model aircraft noise ex plained various sources propeller noise further shown noise due torque loading dominant different sources Last months article con cluded following comments propellers available generally very inefficient inefficiency leads high torque loads relative thrust produced path model aircraft noise reduc tion therefore clear although perhaps easy Making propellers efficient would reduce noise levels compro mising aircraft performance Simply stated means too much work engine spent turning propeller enough used pulling aircraft through air demonstrate fact consider following thought ex periment propeller model aircraft replaced circular rod clear aircraft would able fly motor would work rod would spin great deal noise would generatedbut no thrust would produced round rod terrible propeller noise generated rod propeller would due thick ness cross-sectional diameter torque torque supplied en gine turn quasi propeller order compare noise gen erated particular propeller rod se lected would have size such engine full throttle would turn either rod propeller same rpm means engine would doing same amount work case may surprised learn rod propeller produce similar noise levels similar operating conditions However noise radiating rod has nothing propelling aircraft fore noise due thrust Unfortunately propellers available model ers little too much like rodthey generate large amount torque noise given amount thrust question concerning what can done solve problem depends upon cares responsible Cer tainly people live near flying sites disturbed noise can counted among care local residents often solve problem pro testing such way create new different problem pilotsloss flying site responsibility model aircraft noise does indeed lie fliers manufacturers What can groups combination widespread ed ucation modelers conscientious flying field practices state-of-the-art equip ment will required reach appropri ate workable solution hoped information series articles will pro vide some necessary education Surely manufacturers will continue recognize severity noise issue direct efforts accordingly However its actions individual modelers March 1990 39 Left Argentinean Quique Somenzini displays business end aircraft FAI World Aerobatics Championships Chesapeake VA FutabalYS 12 four-stroke engine turns APC 14 x 14 pro peller muffler Hatori pipe unit added exhaust exten sion Above Somenzinis aircraft held taxiway manda tory static noise readings made measured SPL 855 dBA recorded lowest contest However text re veals limitations applying static readings flight conditions Lower Pitch/Diameter Higher Pitch/Diameter Increoming Airupeed re 1 eller/ Aircraft Matching 120110100-J 0 n C 3 900 C8070 0 Best Fit Line 0 0 08 o -2dBA 0 o0 8090 Predicted SPL dBA will influence continued growth hobby After theyre ones determine what fly isnt difficult understand just sin gle inconsiderate misinformed pilot can create trouble entire club So formation follows will useful accompanied little common sense What t Its model aircraft flying high speeds far runway possibly nearer dis tant houses likely annoy living within proximity flying site typical flight noise runway generally short duration compared time model air noise associated preparation takeoff landing may reaching neighbors Therefore seems obvious strictest noise control efforts should di rected toward high-speed flight condi tion explained first article flying aircraft differs greatly both propel ler performance radiated noise restrained craft ie having no ward motion due differences flow fields around prop case Thus current practice measur ing noise level aircraft being held rest ground fact dealing wrong noise wrong condition wrong place 1989 F3A World Aerobatics Champi onships held Chesapeake VA provided case point FAI competition SPL sound pressure level measured dis tance three meters sideline aircraft must exceed 98 dB quite loud Interestingly enough although aircraft met requirement varying degrees very quiet flighta few point being barely audible fact qualitative stand point planes much quieter air static readings would have suggested can explained examining high-pitch propellers have become pop ular among Pattern fliers prime example particular competition APC 14 x 14 prop Argentinean Quique Somen zinis aircraft measured quietest model meet has proven such propellers perform very well significantly decreasing over noise High-pitch props reach peak efficiency higher flight speeds therefore generate less noise relative other props such speeds However excessive angle tack propeller blades model restrained ground promotes flow separation resulting completely differ ent acoustic signature represent ative case aircraft flight true Somenzinis air craft produced noise level reading 855 dB three meters measured statically must realized low level result flow phenomena dont occur under normal flight conditions fore notably quiet in-flight operation aircraft cannot attributed same factors produced static noise read40 Model Aviation U C U ILl a L a -S 01 S L U 1o1o Figure 2 e Prediction Evaluation PointPropPID 111x764 211x655 311x545 410x770 510x660 610x550 710x550 89x71/283 99x778 109x867 119x556 11 0 N 198dBA 115110m 0 105I oi 100-J estFitLine 0 XMuffler 90-0 Standard 0 High Performance 859095100105110115 Max OASPL Equation 1 dBA Figure 3 e Prediction Evaluation Maximum Airspeed gs What tells us way properly attack model aircraft noise roblem develop some means mea uring sound generated airlane flightwhich its per eived bothersome round course suggesting model aircraft oise should measured flight intro Luces variety logistical problems act just about conceivable method Las practical limitations Fortunately ver possible develop method iredicting model aircraft noise flight rom experimental data acquired under trictly controlled conditions Thus ac ual in-flight measurements could made y qualified individuals proper quipment resulting data could ised create noise prediction method everyday modeler fact same lata could also used predict aircraft erformance would possible Jevelop propeller selection method Nould address both performance noise onsiderations Until recently modelers simply icked two three props listed y engine manufacturer satisfactory engine particular displacement rhis poor way choose propeller rhe proper choice can made neeting specific requirements par icular aircraft/engine combination de ired flight condition good way illus rate point comparing typical rainer powered 40-cu-in engine iigher performance sport aircraft utilizing same engine trainer designed fly low air peeds easily managed begin iers proper propeller case should efficient quiet slow tpeeds depicted Figure 1 Such prop would generally characterized having moderate blade pitch sufficient diame er absorb power generated en gine specified limit airspeed comparison high-performance sport aircraft designed fly much faster Pro pellers best suited such craft ones should reach peak efficiency higher airspeeds indicated sec ond curve figure might achieved increasing pitch-to-diam eter ratio important note since dealing fixed-pitch propellers range high efficiency limited fore propeller selected should peak efficiency occurs likely airspeed particular plane Some compromise performance pos sibly noise will evident other air speeds flight envelope extent performance degradation off de sign conditions has significant effect suitability particular prop given aircraft As preceding example has shown pro peller selection driven aerody namic characteristics aircraft ever great diversity types models flown considerably complicates pro cedure developing single propeller se lection method would applicable model airplanes Dividing model aircraft groups similar aerody namic characteristics would reduce num ber variables Data obtained flight tests aircraft typical certain group could used derive performance acoustic prediction methods would applicable other aircraft group An appropriate prop selection criter ion would based prediction infor mation Consider preliminary example following broad categorization trainers sport aircraft high-performance air craft Since divisions based12 typical maxi mum flight speeds some overlapping11 among categories would expected10 Miss Martha aircraft whtch utilized collect9 flight test data dur- ing course of8 research servesas example advanced sport7 aircraft Thus prediction method6 resulting manipulation research data might5 expected ap ply similar sport aircraft6 Data limitations performance data acquired dur ing tests included airspeed propeller rotational speed down-linked telemetry system acoustic data corres ponding performance readings con sisted OASPL overall sound pressure level values recorded air craft passed over microphone visually interpreted separation distance approxi mately two meters should noted data acquired under less ideal circumstances therefore subject error due following difficulties 1 proper engine needle valve set ting difficult maintain throughout entire series runs resulting inconsist encies available power contribute sim ilar inconsistencies both performance March 1990 41 200PoIntPropP/fl 111x764 211x655 311x545 410x770 c 190510x660 a6lOxS506 E7lOxS50 69x753 99x778 l80109x667 119x55685kmph 0 170Best Fit Line 6 S uffler 2 x 150 0 2 0 140 140150160170180190200 Max flight Speed Equation 2 krtiph Figure 4 ormance Prediction Evaluation Full Throttle o Standard High Performance Noise Constraint C 0 C 0 C 0 C Practical Use Range 0 Airspeed Constraint 9 101112 Diameter inches Figure 5 eller Selection Map acoustic data 2 The simplicity airborne teleme try system limited achievable accuracy performance data recorded ground 3 Varying wind conditions drasti cally different aircraft test speeds contrib uted difficulties consistently flying di rectly over sound-level meter 4 The flyover distances simply judged visual comparison nearby ref erence point therefore subject hu man error should noted however data recorded after re peated within acceptable limits three good passes over microphone list error sources introduced discredit data realistically qual ify extent its accuracy famil iarize reader problem areas need addressed prior performing extensive flight tests Any conclu sions drawn carefully scrutinized potential error mind adjusted accordingly conclu sions derived lab experiments favorably supported flight test data Noise prediction Correlation acous tic data flight tests desired geometric parameters measured propellers data base provided foundation development noise prediction method involved rather tedious task mathematically weighing within single equation contribution individual parameter made overall noise level determining well resulting equation predicted ex perimental values repeating entire process until error minimized result effort following equation actually less threatening appears OASPLpred 110 log D15 log P 40 log NllO log [175 logl JIit]f 10 log 1 8Mt4I [32 log {D-93±15}1151 6429 variables expression describe propeller terms particu lar interest investigation de fined follows D diameter inches P h inches N tional speed rpm o dity outer half prop J nce ratio prop tip Mach number plotting predicted noise against measured noise Figure 2 quality prediction equation can visualized perfect prediction equation would repro duce experimental data exactly means point would collapse onto line unit slope two plotted example slope best fit line through data has value 097 indicates prediction repre sents available data quite well data scatter primarily due exper imental measurement error has calcu lated mean value approximately 2 dBA compares favorably noise prediction equations developed aero space industry Remember though usefulness prediction method deter mined both quality data quality equation equation have given however can predict propeller noise listed variables known Obviously severely limits practical use equation since few modelers have means measuring airspeed engine rpm flight Flying clubs need something simpler work witha method uses easily measured parameters development another equation applies maximum flight speed speed interest way allows significant simplification resulting equation 1 indeed practical since based entirely propeller geome try ruler pocket calculator tools required 1 Max OASPL og [D48 x P/Di x C7SR/R66 x CSOR/C7SRS6S x 625] 4 input variables equation D eller diameter measured inches P/D h-to-diameter ratio CxR eller blade chord measured inches stated location exam ple C5R chord length halfradius position midspan blade R Propeller radius half diameter measured inches Power parameter 10 for standard stock mufflers 105 high-performance mufflers last parameter H serves adjust performance aircraft ex haust system has found socalled high-performance mufflers available modeler today tend increase maximum flight speed general re sult noise speed However model equipped highperformance muffler tested same flight speeds attainable ad vanced muffler noise level remains roughly unchanged comparison results predic tion equation measured results ob 42 Model Aviation Left Several new APC propellers displayed front Miss Martha test aircraft exampies depicted nave diameters rangin nine 11 inches pitches six seven eight 10 inches 9 x 10 propeller mounted 0S Max 46SF engine providec startling flight speeds extremely low noise levels Right John Herbert Raleigh Aeromasters RC Club returns pits after flight An APC 9 x 6 propeller used Goldberg Eaglet powered OS Max 25 engine Although resulting increase max imum flight speed suits style flying proper propeller class aircraft would probably have lower pitch/diameter ratio tc shift peak prop efficiency lower airspeed APC propellers Landing Products distributed through Horizon Distributors SAFE FLYING IS NO ACCIDENT THE BEST FUSELAGE JIG EVER PERIOD Provides Solid Support Accurate Building Rugged Construction 7 Ply Aircraft Plywood Provides Lifetime Use Two Sizes Available Regular Fuselages Up 6 Wide Jumbo Fuselages Up 9 Wide Use Own Building Buard Work Bench Base Mount Jig Station Uni-Strut Guide Rails Most Versatile Set-Up Contains Complete Hardware Instructions Including Uni-Strut Information Buxof4StandardJigStatioflsS1795 Boxof4JumboJigStations1995 Two 5 ft long Guide Rails including mounting nuts 2195 ained Miss Martha aircraft full hrottle given Figure 3 noise pro luced different propellers figire ranges about 87 dBA over 110 dBA Propeller selection made differ ence between quiet aircraft ex tremely noisy However because aforementioned measurement error dif ficult obtain definite conclusions di rectly figure Nevertheless general trends support claim props higher pitch-todiameter ratios produce less noise flight Furthermore examples high-performance muffler used indi cate increased noise levels because engine performing better significance comparison shown Figure 3 demonstrates first possi ble obtain prediction equation ex perimental data second accu racy data controls usefulness such equation Performance prediction As discussed pre viously goal exercise pro duce example propeller selection method addresses both noise per formance performance data acquired flight tests manipulated same manner derive equation would predict maximum flight speed model within same general category sport aircraft ie aerodynamic characteristics similar Miss Martha IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure aileron elevator rudder throw Takes guess work out trimming out airplane quality tool conspiete instructions log book carrying case5795 U PLUG-IN ADJUSTABLE STAB KIT last tan optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matthing phenolic socket 5695 Include 52 SOlItem UPS esidents Add 6% Sales Tax GATOR RIC PRODUCTS 3713 Pompano Dr acola FL 32514 476-8639 test aircraft Equation 2 result such effort Note variables same defined Equation 1 2 Vmax predicted x [DO x PID015 x C7SRIR9 x CSoRIC7SR65 X C9oR/C7SR055 x PH4] Figure 4 presents graphic comparison measured predicted flight velocity error approximately 5% mean flight velocity translates about 85 kmph Comparison figure Fig ure 3 reveals general trend props higher pitch-to-diameter ra tios data base produced highest maximum flight speed lowest noise Once again consistent labo ratory results Propeller selection method further uti lizing prediction equations 1 2 practical method selecting propeller satisfies reasonable noise per formance constraints can developed aircraft categoryie sport air craft. Consider task selecting pro peller meets following criteria Aircraft Miss Martha Advanced level sport Engine 05 Max 46 SF Muffler PLUG-IN WING ADJUSTER KIT Four glass filled nylon brackets included key wing panels front rear allow accurately adjust panel straight flight Complete hardware & InstructIons 5995 WING TUBE & SOCKETS Aluminum alloy tubing plug-in wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2S 895 1diax2S 995 1dias351495 Davis Diesel Soundmaster high perform ance Desired maximum flight speed 175 kmph 109 mph Flying site noise regulation 880 dBA @ two meters flyover ap prox 853 dBA @ three meters Reference should made equations 1 2 Since high-performance muf fler used H Furthermore mea surements taken propellers data base produce following average blade chord distribution C7SR/R C5oR/C75R C9oRIC75R0725 will assumed propeller ques tion has expected blade chord distribu tion substituting known values equations following mathemati cal inequalities may written terms blade pitch diameter both inches 1 P155 x l05 x Noise Constraint 2aP 1 295 X Speed Constraint Plotting both same figure Figure 5 produces finite boundary above pitch/diameter combinations sat isfy constraints can found Examina RDABLE AL POWER INTRODUCTORY 849 SPECIAL SEND 5100 TECHNICAL DATA THE MIKE GR6- 120 2-CYCLE POWERPLANT 6 CYLINDER RADIAL ANTY LBSOFTHRuST * 25 SHP IDYNO TESTEDI * NO VIBRATION III * SINGLE NEEDLE VALVE * 8 STAINLESS BALL BROS * IDLES AT 1800 RPM * OIL LUBRICATED GEARS * 3/8 HARDENED SE SHAFT * FULLY FLIGHT TESTED * DIAMETER 8 TO PLUG TIPS * WEIGHT 4 LEE INCLuDING INTEGRAL MOUNT AND MUFFLER * SWINGS 18/8 PROF /8 8880 RPM * EXCEEDS QuADRA 35 IN POWER AND ZENOAH G38 IN THRUST * GLOW FUEL USED-1S% * GLOW PLUG LEADS INCLUDED * READY TO FLY NOT KITI 33 DEALER INQUIRIESs-% INVITEDp TECHNOLOGIES INC 7 Greenwood Lane VaiSsIla New YorE lOSES 1914 888-9373 FAT PENDING TEST FLOWN IN 72 GM PLASTICS F4U CORSAIR 72 BOB DIVELYS SU-2 BIPLANE 88 PROCTOR NIEUPORT 28 BIPLANE 58 MONOCOUPE EISA March 1990 43 $1695 LIST THE PIPER BRAVE 1/4 scale model Pipers latest Ag plane t wing span 30-33 lbs 5 cc power lb payload ational flaps hopper door onal Spreader Kit formed aluminum landing gear rglass cowls um-formed canopy tucted extruded foam ply hardwood r -Model actually dustingBRKE $269~ OPTIONAL995 SPREADER SEND siee FOR CATALOG OFC/IRT 1 NEODESHA KS 66757 SAC KITS AND ACCESSORIES316 325-2821 Free Shipping Kit OrdersScott Airplane CompanyVISA MASTERCARD tion figure leads obvious con- distribution assumed could have ious props yielded some important observa clusion propellers re- resulted slight shift noise boun- tions Since explained previously thc gion bounded curves either dont dary necessary exclude 9 x 75 prop goal match peak propeller effi exist simply aren t practical use important thing recognize ciency airspeed model i specified engine desirable propeller pitch/diameter ratio often flown performance othex ranges pitch diameter occur near least 083 would required meet se- speeds does suffer consequence Examrange represented data base propel- lection criteria pitch/diameter ratio pIes noticeable performance degradation lers both because prediction increased further might possible op- off design conditions follow equations derived data acquired erate required airspeed less first thing modelers will notice thil such propellers because props out- noise the static rpm will much lower highside range tend subject prob- recent introduction new line pitch props However expected lems area practicality props allows further investigation result flow separation blades Functional propellers must able ab- hypothesis Known APC Advanced Pre- aircraft i5 restrained theres no sorb power available engine cision Composite props line manu- reason discouraged fact follow reasonable rpm must also perform ad- factured California Landing Products rule thumb prop screaminl equately off design situations distributed hobby dealers through ground engine sufficientl rules out propellers too little diameter Horizon Distributors Several examples loadedwhich means flight perform too much pitch example ad- props flown Miss Martha ance will compromised noise ditional boundary sets lower diam- test aircraft evaluated qualitatively creased course direct opposi eter limit 9 might appropriately instrumentation several tion way modelers choose prop inserted Figure 5 Doing con- produced excellent results 9 present fines realistic choices narrow x 10 P/D 111 A second observation takeofi shaded region figure The APC 9 x 10 propeller produced level acceleration will reduced increas time flight testing per- flight speeds never previously attained es takeoff length small amount Du formed highest pitch/diameter ratio other prop aircraft as- excessive thrust-to-weight ratio 01 prop available use type engine tounding observation however model airplanes however 9 x 75 P/DO83 Notice quietness APC prop propeller major problem Figure 5 prop should theoretically quiet airflow around Finally thrust low flight speeds i satisfy constraints example How- plane audible no data has reduced resulting degraded maneuvet ever inspection data propel- acquired props quite obvi- performance Note aircraft fly ler Figure 3 reveals noise con- ous exhibit increased levels effi- ing fast climb rate excellent its straint would met Remember ciency due increased performance model slows down powet though boundaries Figure 5 decreased noise levels is increased nose raised ef derived imperfect experi- Qualitative comparisons takeoff fect becomes apparent mental data average blade chord lengths climb performance var- Continued page 140 PRACTICAL SIZED GIANT SCALE MODEL PLANS Fiberg/ass Cowlings Canopies Available N1 311/2 1140Span54200 F4u CORSAiR2 1/4 193Span$3000 ASMS ZERO2 1/2 Span $3000Plans RK-20 cuRTiS P40 2 1/2 Span $3000 RK-740 Oucted Fans AT-6 TEXAN 24 1 Span $3000 Phaniom 35 Span $1000 FSF BEARCAT 2 1/2 Span $3000 FQKKER OR127163 Viggen32 Span SiO00 Tripe $2700p36 Span $1000 Pian nd canopy$1500 Order FromCredited First Order $25 Nick Ziroli29 Edgar Dr Smithtown NY 11787 USA516-234-5038 44 Model Aviation Mere Fun SPECIFICATIONS Wing Span62'2 inches Wing Area770 square inches Engine Size 10 cc 90 129 four stroke Designed AMA FAI Turn-around pattern Foam wing stab 3-32 Balsa sheet covering Tricycle conven tional gear fixed retracts Rear side exhaust fiber glass canopy Very positive maneuverable XLT SPECIFIC Wing Span65 inches Length65 inches Wing Area845 square inches Recommended Engine Size 10 cc 90 120 four stroke XLT designed tuned pipe re tract landing gears Capable AMA Turn-around pattern Rear side ex haust SPECIFICATIONS Wing Span Wing Area Engine Size 63'4 inches 700 square inches 50-60 Glow 90 four stroke fun sport pattern turn-around can done Utter Chaos completely built up Balsa construction Canopy engine mount included years proven flying reliablity BRIDI AIRCRAFT DESIGNS INC 23625 Pineforest Lane Harbor City California 90710 213 549-8264 326-5013 SEE YOUR FAVORITE HOBBY SHOP OR RETAIL OUTLET Dealer Inquries Invited PRODUCTS Complete Line Exheust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers Expansion Mufflers copter Ball Mufflers ialized Exhaust Systems Unsurpassed Workmaashin & Padormance Inc Chicago IL 60651 Stay-Brite silver solder Stay Clean flux 1W Harris Co 10930 Deerfield Rd Cincinnati OH 45242 Tools SR batteries tool kit contains SAE metric hex wrenches well crosspoint regular screwdriver bits nifty box ratchet drive screwdriver-type handle very handy use love bits fit electric screwdriver should grab interest somewhat greater interest fact can buy single replacement bits should damaged lost Think sel dom can thing like days SR Batteries Inc Box 287 Bellport NY 11713 tel 1-516/286-0079 Wen portable tool kit #2336 has de scribed previous column contains drill motor Dremel-type grinder saber saw sol dering iron plug cigarette lighter 12-VDC receptacle car have kit find uses dont have people snicker idea toy tools look like toys worked like 110VAC tools no trouble cutting A-in ply wood drilling 4-in holes Ford van body parts Portasol butane-fueled soldering iron also described earlier Suffice say worked fine Camera bought Minolta Weather matic Dual 35 main thought might travel salt air splashes possibility being dropped overboard rule Out use expensive cameras lenses camera 0-ring-sealed against dust moisture has corrosion-resistant yellow plastic exterior will float water accepts DXcoded ASA 100 1000 35mm color print film has pushbutton-selected internal 35mm 50mm lenses features automatic film advance/rewind well autofocus nearest focus point two feet 50mm lens focus-hold feature built shutter button just big cameras tiny built-in flash much better no flash 26 x 31 x 58 less pound camera relatively small light nice hiking must carry everything body much dust Alaska stayed outside camera bought camera its weather resistance learned enjoy fact can worked hand ap preciate its durability favorite lens 35mm-to-tOSmm macro zoom can understand felt limited BATT- CHEKEX Saves Time . Saves Models Install RO Models 3-Level indication receiver battery status press button Precise Rugged Small Light /2 oz Made SA Also custom units other applications Order Today si 495 trom dealer send check money order topostpaid Protune Corp 914 462-6452 PO Box 1808 Poughkeepal NY 12601 NY State residents add sales tax non-macro 35/50mm lens selection use found could get about 85% pic tures wanted Thats pretty good compro mise Any camera just tool good general-purpose tool think would look good field kit perhaps could send some pictures column Minolta Weathermatic Dual 35 local camera store Light 12-VDC fluorescent light plugs automobile cigar lighter very handy put couple strips VelcroTM hooks back permit stick light prati cally anywhere cloth interior van sticks very neatly head-liner seat backs comes off easily need another po sition unit draws 06 amps opposed vans interior lights draw 24 amps provides plenty light reading working whatever have separate deep-cycle RV recreational vehicleEd battery van operate re frigerator lights whatever other items might need total capacity RV battery 70 amp-hours refrigerator alone can exhaust about 17 hours Ito fall asleep refrigerator interior lights battery would exhausted 11 hours Sub stituting fluorescent light vans stan dard interior lights will let battery last 15 hours think extra four hours operating time very valuable RV battery course independent battery starts van wont give manufacturer light because have seen similar units K-Mart Radio Shack etc Prop Noise Continued page 44 last factor controlled fi nal choice prop test aircraft An APC 10 x 8 determined best compromise fact maximum flight speed noise level appear similar 9 x 10 prop low-speed thrust greatly improved As airplane/prop combination demon strates now possible operate model aircraft reduced noise levels little no compromise performance hoped propeller manufacturers will follow APC lead developing introducing new lines will benefit aircraft sizes would major step toward preserving community relations ensur ing continued growth hobby 140 Model Aviation Radio Technique/Myers Continued page 107 Celebrating 10 years producing largest selection giant scale kits available today Design building integrity scale fidelity scale flight characteristics standard IKON NWST 22 kits choose Conclusions research program sponsored AMA order gain better understanding propeller noise major objectives determine con tribution propeller makes over aircraft noise isolate main source prop noise latter proved significant establish guidelines would ulti mately lead quieter model aircraft opera tion combination propeller theory experimental data wind tun nel flight tests provided some definitive conclusions 1 In order reduce noise generated model aircraft dominant source must reduced Provided reasonable muffler used propeller domi nant noise source 2 The dominant source propeller noise torque noise Since efficient propellers generate thrust given amount required torque use will re sult less noise given airspeed 3 Propellers currently available mod elers general quite inefficient use such propellers leads less ideal performance acoustic characteris tics 4 Modelers should select propeller peak efficiency occurs near range airspeeds aircraft will usually operated general props increased pitch/diameter ratios must made available allow such integration wide variety aircraft 5 Noise reduction efforts should directed maximum flight speed condi tion way truly quantify noise attempt reduce mea sure flight 6 It possible develop propeller se lection method based in-flight experimental data addresses both noise performance would give aver age modeler means selecting prop would meet noise regulations performing satisfaction 7 This information will useful applied universally will job ganized groups such AMA clubs hobby dealers manufacturers edu cate individuals enforce proper pro cedures research study described series articles has disclosed nature prob lem propeller noise introduced some solutions Using efficient propellers will reduce model aircraft noise However continued research should directed toward studying effect propeller ge ometry overall efficiency should lead optimal blade designs ulti mately minimal propeller noise Finally carefully organized flight test program would provide data base developing standardized propeller selection criterion SAFE FLYING IS NO ACCIDENT Keithsgo latters numbers some known experimental error associated ex act measurement wire length involved physical portion wire near connector itself cases actual length somewhat intended six inches voltage drops would higher expected Whatever wary installation losses plane Use quality wire quality connectorsbut use sparingly Two new speed controls shown photos month First Jomars latesta large control big systems SC 6 mentioned upcoming new product December 1989 column now closer reality control pictured prototype designed operate 22- 34cell systems features new Signetics chip thats designed drive MOSFET metal-oxide semiconductor field-effect rransistorRMcM gates efficiently course its high-frame-rate design optically coupled Tentative list price $130 Joe Utazi tells product line will soon carried distributors across country competitive pricing will drive price other products down Another new control least new writer Horak imported Canada As understand controls handmade Jiri Horak 3403 Fellmore Drive Mississauga Ontar io Canada L5C 2E1 arc scarce supply Jiri makes several versions including ones brakesContinued page 144 March 1990 141 MOIIUUOUP VUA 114 SCALE 96 STITS PLAYBOYWACO UII-7 113 SCALE 88115 SCALE 72 RC Electrics/Kopski Continued page 47
Edition: Model Aviation - 1990/03
Page Numbers: 39, 40, 41, 42, 43, 44, 140, 141
lodel Propeller NOISE three preceding articles discussing findings ex haustive prop noise study conducted North Carolina State University sponsored AMA has demonstrated average commercial propeller inefficient major source model airplane noise engine properly muf fled What can done solve problem discussed concluding segment ER Vess D Heathcoat R Nagel THE PREVIOUS articles four-part series have shown propellers main source model aircraft noise ex plained various sources propeller noise further shown noise due torque loading dominant different sources Last months article con cluded following comments propellers available generally very inefficient inefficiency leads high torque loads relative thrust produced path model aircraft noise reduc tion therefore clear although perhaps easy Making propellers efficient would reduce noise levels compro mising aircraft performance Simply stated means too much work engine spent turning propeller enough used pulling aircraft through air demonstrate fact consider following thought ex periment propeller model aircraft replaced circular rod clear aircraft would able fly motor would work rod would spin great deal noise would generatedbut no thrust would produced round rod terrible propeller noise generated rod propeller would due thick ness cross-sectional diameter torque torque supplied en gine turn quasi propeller order compare noise gen erated particular propeller rod se lected would have size such engine full throttle would turn either rod propeller same rpm means engine would doing same amount work case may surprised learn rod propeller produce similar noise levels similar operating conditions However noise radiating rod has nothing propelling aircraft fore noise due thrust Unfortunately propellers available model ers little too much like rodthey generate large amount torque noise given amount thrust question concerning what can done solve problem depends upon cares responsible Cer tainly people live near flying sites disturbed noise can counted among care local residents often solve problem pro testing such way create new different problem pilotsloss flying site responsibility model aircraft noise does indeed lie fliers manufacturers What can groups combination widespread ed ucation modelers conscientious flying field practices state-of-the-art equip ment will required reach appropri ate workable solution hoped information series articles will pro vide some necessary education Surely manufacturers will continue recognize severity noise issue direct efforts accordingly However its actions individual modelers March 1990 39 Left Argentinean Quique Somenzini displays business end aircraft FAI World Aerobatics Championships Chesapeake VA FutabalYS 12 four-stroke engine turns APC 14 x 14 pro peller muffler Hatori pipe unit added exhaust exten sion Above Somenzinis aircraft held taxiway manda tory static noise readings made measured SPL 855 dBA recorded lowest contest However text re veals limitations applying static readings flight conditions Lower Pitch/Diameter Higher Pitch/Diameter Increoming Airupeed re 1 eller/ Aircraft Matching 120110100-J 0 n C 3 900 C8070 0 Best Fit Line 0 0 08 o -2dBA 0 o0 8090 Predicted SPL dBA will influence continued growth hobby After theyre ones determine what fly isnt difficult understand just sin gle inconsiderate misinformed pilot can create trouble entire club So formation follows will useful accompanied little common sense What t Its model aircraft flying high speeds far runway possibly nearer dis tant houses likely annoy living within proximity flying site typical flight noise runway generally short duration compared time model air noise associated preparation takeoff landing may reaching neighbors Therefore seems obvious strictest noise control efforts should di rected toward high-speed flight condi tion explained first article flying aircraft differs greatly both propel ler performance radiated noise restrained craft ie having no ward motion due differences flow fields around prop case Thus current practice measur ing noise level aircraft being held rest ground fact dealing wrong noise wrong condition wrong place 1989 F3A World Aerobatics Champi onships held Chesapeake VA provided case point FAI competition SPL sound pressure level measured dis tance three meters sideline aircraft must exceed 98 dB quite loud Interestingly enough although aircraft met requirement varying degrees very quiet flighta few point being barely audible fact qualitative stand point planes much quieter air static readings would have suggested can explained examining high-pitch propellers have become pop ular among Pattern fliers prime example particular competition APC 14 x 14 prop Argentinean Quique Somen zinis aircraft measured quietest model meet has proven such propellers perform very well significantly decreasing over noise High-pitch props reach peak efficiency higher flight speeds therefore generate less noise relative other props such speeds However excessive angle tack propeller blades model restrained ground promotes flow separation resulting completely differ ent acoustic signature represent ative case aircraft flight true Somenzinis air craft produced noise level reading 855 dB three meters measured statically must realized low level result flow phenomena dont occur under normal flight conditions fore notably quiet in-flight operation aircraft cannot attributed same factors produced static noise read40 Model Aviation U C U ILl a L a -S 01 S L U 1o1o Figure 2 e Prediction Evaluation PointPropPID 111x764 211x655 311x545 410x770 510x660 610x550 710x550 89x71/283 99x778 109x867 119x556 11 0 N 198dBA 115110m 0 105I oi 100-J estFitLine 0 XMuffler 90-0 Standard 0 High Performance 859095100105110115 Max OASPL Equation 1 dBA Figure 3 e Prediction Evaluation Maximum Airspeed gs What tells us way properly attack model aircraft noise roblem develop some means mea uring sound generated airlane flightwhich its per eived bothersome round course suggesting model aircraft oise should measured flight intro Luces variety logistical problems act just about conceivable method Las practical limitations Fortunately ver possible develop method iredicting model aircraft noise flight rom experimental data acquired under trictly controlled conditions Thus ac ual in-flight measurements could made y qualified individuals proper quipment resulting data could ised create noise prediction method everyday modeler fact same lata could also used predict aircraft erformance would possible Jevelop propeller selection method Nould address both performance noise onsiderations Until recently modelers simply icked two three props listed y engine manufacturer satisfactory engine particular displacement rhis poor way choose propeller rhe proper choice can made neeting specific requirements par icular aircraft/engine combination de ired flight condition good way illus rate point comparing typical rainer powered 40-cu-in engine iigher performance sport aircraft utilizing same engine trainer designed fly low air peeds easily managed begin iers proper propeller case should efficient quiet slow tpeeds depicted Figure 1 Such prop would generally characterized having moderate blade pitch sufficient diame er absorb power generated en gine specified limit airspeed comparison high-performance sport aircraft designed fly much faster Pro pellers best suited such craft ones should reach peak efficiency higher airspeeds indicated sec ond curve figure might achieved increasing pitch-to-diam eter ratio important note since dealing fixed-pitch propellers range high efficiency limited fore propeller selected should peak efficiency occurs likely airspeed particular plane Some compromise performance pos sibly noise will evident other air speeds flight envelope extent performance degradation off de sign conditions has significant effect suitability particular prop given aircraft As preceding example has shown pro peller selection driven aerody namic characteristics aircraft ever great diversity types models flown considerably complicates pro cedure developing single propeller se lection method would applicable model airplanes Dividing model aircraft groups similar aerody namic characteristics would reduce num ber variables Data obtained flight tests aircraft typical certain group could used derive performance acoustic prediction methods would applicable other aircraft group An appropriate prop selection criter ion would based prediction infor mation Consider preliminary example following broad categorization trainers sport aircraft high-performance air craft Since divisions based12 typical maxi mum flight speeds some overlapping11 among categories would expected10 Miss Martha aircraft whtch utilized collect9 flight test data dur- ing course of8 research servesas example advanced sport7 aircraft Thus prediction method6 resulting manipulation research data might5 expected ap ply similar sport aircraft6 Data limitations performance data acquired dur ing tests included airspeed propeller rotational speed down-linked telemetry system acoustic data corres ponding performance readings con sisted OASPL overall sound pressure level values recorded air craft passed over microphone visually interpreted separation distance approxi mately two meters should noted data acquired under less ideal circumstances therefore subject error due following difficulties 1 proper engine needle valve set ting difficult maintain throughout entire series runs resulting inconsist encies available power contribute sim ilar inconsistencies both performance March 1990 41 200PoIntPropP/fl 111x764 211x655 311x545 410x770 c 190510x660 a6lOxS506 E7lOxS50 69x753 99x778 l80109x667 119x55685kmph 0 170Best Fit Line 6 S uffler 2 x 150 0 2 0 140 140150160170180190200 Max flight Speed Equation 2 krtiph Figure 4 ormance Prediction Evaluation Full Throttle o Standard High Performance Noise Constraint C 0 C 0 C 0 C Practical Use Range 0 Airspeed Constraint 9 101112 Diameter inches Figure 5 eller Selection Map acoustic data 2 The simplicity airborne teleme try system limited achievable accuracy performance data recorded ground 3 Varying wind conditions drasti cally different aircraft test speeds contrib uted difficulties consistently flying di rectly over sound-level meter 4 The flyover distances simply judged visual comparison nearby ref erence point therefore subject hu man error should noted however data recorded after re peated within acceptable limits three good passes over microphone list error sources introduced discredit data realistically qual ify extent its accuracy famil iarize reader problem areas need addressed prior performing extensive flight tests Any conclu sions drawn carefully scrutinized potential error mind adjusted accordingly conclu sions derived lab experiments favorably supported flight test data Noise prediction Correlation acous tic data flight tests desired geometric parameters measured propellers data base provided foundation development noise prediction method involved rather tedious task mathematically weighing within single equation contribution individual parameter made overall noise level determining well resulting equation predicted ex perimental values repeating entire process until error minimized result effort following equation actually less threatening appears OASPLpred 110 log D15 log P 40 log NllO log [175 logl JIit]f 10 log 1 8Mt4I [32 log {D-93±15}1151 6429 variables expression describe propeller terms particu lar interest investigation de fined follows D diameter inches P h inches N tional speed rpm o dity outer half prop J nce ratio prop tip Mach number plotting predicted noise against measured noise Figure 2 quality prediction equation can visualized perfect prediction equation would repro duce experimental data exactly means point would collapse onto line unit slope two plotted example slope best fit line through data has value 097 indicates prediction repre sents available data quite well data scatter primarily due exper imental measurement error has calcu lated mean value approximately 2 dBA compares favorably noise prediction equations developed aero space industry Remember though usefulness prediction method deter mined both quality data quality equation equation have given however can predict propeller noise listed variables known Obviously severely limits practical use equation since few modelers have means measuring airspeed engine rpm flight Flying clubs need something simpler work witha method uses easily measured parameters development another equation applies maximum flight speed speed interest way allows significant simplification resulting equation 1 indeed practical since based entirely propeller geome try ruler pocket calculator tools required 1 Max OASPL og [D48 x P/Di x C7SR/R66 x CSOR/C7SRS6S x 625] 4 input variables equation D eller diameter measured inches P/D h-to-diameter ratio CxR eller blade chord measured inches stated location exam ple C5R chord length halfradius position midspan blade R Propeller radius half diameter measured inches Power parameter 10 for standard stock mufflers 105 high-performance mufflers last parameter H serves adjust performance aircraft ex haust system has found socalled high-performance mufflers available modeler today tend increase maximum flight speed general re sult noise speed However model equipped highperformance muffler tested same flight speeds attainable ad vanced muffler noise level remains roughly unchanged comparison results predic tion equation measured results ob 42 Model Aviation Left Several new APC propellers displayed front Miss Martha test aircraft exampies depicted nave diameters rangin nine 11 inches pitches six seven eight 10 inches 9 x 10 propeller mounted 0S Max 46SF engine providec startling flight speeds extremely low noise levels Right John Herbert Raleigh Aeromasters RC Club returns pits after flight An APC 9 x 6 propeller used Goldberg Eaglet powered OS Max 25 engine Although resulting increase max imum flight speed suits style flying proper propeller class aircraft would probably have lower pitch/diameter ratio tc shift peak prop efficiency lower airspeed APC propellers Landing Products distributed through Horizon Distributors SAFE FLYING IS NO ACCIDENT THE BEST FUSELAGE JIG EVER PERIOD Provides Solid Support Accurate Building Rugged Construction 7 Ply Aircraft Plywood Provides Lifetime Use Two Sizes Available Regular Fuselages Up 6 Wide Jumbo Fuselages Up 9 Wide Use Own Building Buard Work Bench Base Mount Jig Station Uni-Strut Guide Rails Most Versatile Set-Up Contains Complete Hardware Instructions Including Uni-Strut Information Buxof4StandardJigStatioflsS1795 Boxof4JumboJigStations1995 Two 5 ft long Guide Rails including mounting nuts 2195 ained Miss Martha aircraft full hrottle given Figure 3 noise pro luced different propellers figire ranges about 87 dBA over 110 dBA Propeller selection made differ ence between quiet aircraft ex tremely noisy However because aforementioned measurement error dif ficult obtain definite conclusions di rectly figure Nevertheless general trends support claim props higher pitch-todiameter ratios produce less noise flight Furthermore examples high-performance muffler used indi cate increased noise levels because engine performing better significance comparison shown Figure 3 demonstrates first possi ble obtain prediction equation ex perimental data second accu racy data controls usefulness such equation Performance prediction As discussed pre viously goal exercise pro duce example propeller selection method addresses both noise per formance performance data acquired flight tests manipulated same manner derive equation would predict maximum flight speed model within same general category sport aircraft ie aerodynamic characteristics similar Miss Martha IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure aileron elevator rudder throw Takes guess work out trimming out airplane quality tool conspiete instructions log book carrying case5795 U PLUG-IN ADJUSTABLE STAB KIT last tan optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matthing phenolic socket 5695 Include 52 SOlItem UPS esidents Add 6% Sales Tax GATOR RIC PRODUCTS 3713 Pompano Dr acola FL 32514 476-8639 test aircraft Equation 2 result such effort Note variables same defined Equation 1 2 Vmax predicted x [DO x PID015 x C7SRIR9 x CSoRIC7SR65 X C9oR/C7SR055 x PH4] Figure 4 presents graphic comparison measured predicted flight velocity error approximately 5% mean flight velocity translates about 85 kmph Comparison figure Fig ure 3 reveals general trend props higher pitch-to-diameter ra tios data base produced highest maximum flight speed lowest noise Once again consistent labo ratory results Propeller selection method further uti lizing prediction equations 1 2 practical method selecting propeller satisfies reasonable noise per formance constraints can developed aircraft categoryie sport air craft. Consider task selecting pro peller meets following criteria Aircraft Miss Martha Advanced level sport Engine 05 Max 46 SF Muffler PLUG-IN WING ADJUSTER KIT Four glass filled nylon brackets included key wing panels front rear allow accurately adjust panel straight flight Complete hardware & InstructIons 5995 WING TUBE & SOCKETS Aluminum alloy tubing plug-in wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2S 895 1diax2S 995 1dias351495 Davis Diesel Soundmaster high perform ance Desired maximum flight speed 175 kmph 109 mph Flying site noise regulation 880 dBA @ two meters flyover ap prox 853 dBA @ three meters Reference should made equations 1 2 Since high-performance muf fler used H Furthermore mea surements taken propellers data base produce following average blade chord distribution C7SR/R C5oR/C75R C9oRIC75R0725 will assumed propeller ques tion has expected blade chord distribu tion substituting known values equations following mathemati cal inequalities may written terms blade pitch diameter both inches 1 P155 x l05 x Noise Constraint 2aP 1 295 X Speed Constraint Plotting both same figure Figure 5 produces finite boundary above pitch/diameter combinations sat isfy constraints can found Examina RDABLE AL POWER INTRODUCTORY 849 SPECIAL SEND 5100 TECHNICAL DATA THE MIKE GR6- 120 2-CYCLE POWERPLANT 6 CYLINDER RADIAL ANTY LBSOFTHRuST * 25 SHP IDYNO TESTEDI * NO VIBRATION III * SINGLE NEEDLE VALVE * 8 STAINLESS BALL BROS * IDLES AT 1800 RPM * OIL LUBRICATED GEARS * 3/8 HARDENED SE SHAFT * FULLY FLIGHT TESTED * DIAMETER 8 TO PLUG TIPS * WEIGHT 4 LEE INCLuDING INTEGRAL MOUNT AND MUFFLER * SWINGS 18/8 PROF /8 8880 RPM * EXCEEDS QuADRA 35 IN POWER AND ZENOAH G38 IN THRUST * GLOW FUEL USED-1S% * GLOW PLUG LEADS INCLUDED * READY TO FLY NOT KITI 33 DEALER INQUIRIESs-% INVITEDp TECHNOLOGIES INC 7 Greenwood Lane VaiSsIla New YorE lOSES 1914 888-9373 FAT PENDING TEST FLOWN IN 72 GM PLASTICS F4U CORSAIR 72 BOB DIVELYS SU-2 BIPLANE 88 PROCTOR NIEUPORT 28 BIPLANE 58 MONOCOUPE EISA March 1990 43 $1695 LIST THE PIPER BRAVE 1/4 scale model Pipers latest Ag plane t wing span 30-33 lbs 5 cc power lb payload ational flaps hopper door onal Spreader Kit formed aluminum landing gear rglass cowls um-formed canopy tucted extruded foam ply hardwood r -Model actually dustingBRKE $269~ OPTIONAL995 SPREADER SEND siee FOR CATALOG OFC/IRT 1 NEODESHA KS 66757 SAC KITS AND ACCESSORIES316 325-2821 Free Shipping Kit OrdersScott Airplane CompanyVISA MASTERCARD tion figure leads obvious con- distribution assumed could have ious props yielded some important observa clusion propellers re- resulted slight shift noise boun- tions Since explained previously thc gion bounded curves either dont dary necessary exclude 9 x 75 prop goal match peak propeller effi exist simply aren t practical use important thing recognize ciency airspeed model i specified engine desirable propeller pitch/diameter ratio often flown performance othex ranges pitch diameter occur near least 083 would required meet se- speeds does suffer consequence Examrange represented data base propel- lection criteria pitch/diameter ratio pIes noticeable performance degradation lers both because prediction increased further might possible op- off design conditions follow equations derived data acquired erate required airspeed less first thing modelers will notice thil such propellers because props out- noise the static rpm will much lower highside range tend subject prob- recent introduction new line pitch props However expected lems area practicality props allows further investigation result flow separation blades Functional propellers must able ab- hypothesis Known APC Advanced Pre- aircraft i5 restrained theres no sorb power available engine cision Composite props line manu- reason discouraged fact follow reasonable rpm must also perform ad- factured California Landing Products rule thumb prop screaminl equately off design situations distributed hobby dealers through ground engine sufficientl rules out propellers too little diameter Horizon Distributors Several examples loadedwhich means flight perform too much pitch example ad- props flown Miss Martha ance will compromised noise ditional boundary sets lower diam- test aircraft evaluated qualitatively creased course direct opposi eter limit 9 might appropriately instrumentation several tion way modelers choose prop inserted Figure 5 Doing con- produced excellent results 9 present fines realistic choices narrow x 10 P/D 111 A second observation takeofi shaded region figure The APC 9 x 10 propeller produced level acceleration will reduced increas time flight testing per- flight speeds never previously attained es takeoff length small amount Du formed highest pitch/diameter ratio other prop aircraft as- excessive thrust-to-weight ratio 01 prop available use type engine tounding observation however model airplanes however 9 x 75 P/DO83 Notice quietness APC prop propeller major problem Figure 5 prop should theoretically quiet airflow around Finally thrust low flight speeds i satisfy constraints example How- plane audible no data has reduced resulting degraded maneuvet ever inspection data propel- acquired props quite obvi- performance Note aircraft fly ler Figure 3 reveals noise con- ous exhibit increased levels effi- ing fast climb rate excellent its straint would met Remember ciency due increased performance model slows down powet though boundaries Figure 5 decreased noise levels is increased nose raised ef derived imperfect experi- Qualitative comparisons takeoff fect becomes apparent mental data average blade chord lengths climb performance var- Continued page 140 PRACTICAL SIZED GIANT SCALE MODEL PLANS Fiberg/ass Cowlings Canopies Available N1 311/2 1140Span54200 F4u CORSAiR2 1/4 193Span$3000 ASMS ZERO2 1/2 Span $3000Plans RK-20 cuRTiS P40 2 1/2 Span $3000 RK-740 Oucted Fans AT-6 TEXAN 24 1 Span $3000 Phaniom 35 Span $1000 FSF BEARCAT 2 1/2 Span $3000 FQKKER OR127163 Viggen32 Span SiO00 Tripe $2700p36 Span $1000 Pian nd canopy$1500 Order FromCredited First Order $25 Nick Ziroli29 Edgar Dr Smithtown NY 11787 USA516-234-5038 44 Model Aviation Mere Fun SPECIFICATIONS Wing Span62'2 inches Wing Area770 square inches Engine Size 10 cc 90 129 four stroke Designed AMA FAI Turn-around pattern Foam wing stab 3-32 Balsa sheet covering Tricycle conven tional gear fixed retracts Rear side exhaust fiber glass canopy Very positive maneuverable XLT SPECIFIC Wing Span65 inches Length65 inches Wing Area845 square inches Recommended Engine Size 10 cc 90 120 four stroke XLT designed tuned pipe re tract landing gears Capable AMA Turn-around pattern Rear side ex haust SPECIFICATIONS Wing Span Wing Area Engine Size 63'4 inches 700 square inches 50-60 Glow 90 four stroke fun sport pattern turn-around can done Utter Chaos completely built up Balsa construction Canopy engine mount included years proven flying reliablity BRIDI AIRCRAFT DESIGNS INC 23625 Pineforest Lane Harbor City California 90710 213 549-8264 326-5013 SEE YOUR FAVORITE HOBBY SHOP OR RETAIL OUTLET Dealer Inquries Invited PRODUCTS Complete Line Exheust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers Expansion Mufflers copter Ball Mufflers ialized Exhaust Systems Unsurpassed Workmaashin & Padormance Inc Chicago IL 60651 Stay-Brite silver solder Stay Clean flux 1W Harris Co 10930 Deerfield Rd Cincinnati OH 45242 Tools SR batteries tool kit contains SAE metric hex wrenches well crosspoint regular screwdriver bits nifty box ratchet drive screwdriver-type handle very handy use love bits fit electric screwdriver should grab interest somewhat greater interest fact can buy single replacement bits should damaged lost Think sel dom can thing like days SR Batteries Inc Box 287 Bellport NY 11713 tel 1-516/286-0079 Wen portable tool kit #2336 has de scribed previous column contains drill motor Dremel-type grinder saber saw sol dering iron plug cigarette lighter 12-VDC receptacle car have kit find uses dont have people snicker idea toy tools look like toys worked like 110VAC tools no trouble cutting A-in ply wood drilling 4-in holes Ford van body parts Portasol butane-fueled soldering iron also described earlier Suffice say worked fine Camera bought Minolta Weather matic Dual 35 main thought might travel salt air splashes possibility being dropped overboard rule Out use expensive cameras lenses camera 0-ring-sealed against dust moisture has corrosion-resistant yellow plastic exterior will float water accepts DXcoded ASA 100 1000 35mm color print film has pushbutton-selected internal 35mm 50mm lenses features automatic film advance/rewind well autofocus nearest focus point two feet 50mm lens focus-hold feature built shutter button just big cameras tiny built-in flash much better no flash 26 x 31 x 58 less pound camera relatively small light nice hiking must carry everything body much dust Alaska stayed outside camera bought camera its weather resistance learned enjoy fact can worked hand ap preciate its durability favorite lens 35mm-to-tOSmm macro zoom can understand felt limited BATT- CHEKEX Saves Time . Saves Models Install RO Models 3-Level indication receiver battery status press button Precise Rugged Small Light /2 oz Made SA Also custom units other applications Order Today si 495 trom dealer send check money order topostpaid Protune Corp 914 462-6452 PO Box 1808 Poughkeepal NY 12601 NY State residents add sales tax non-macro 35/50mm lens selection use found could get about 85% pic tures wanted Thats pretty good compro mise Any camera just tool good general-purpose tool think would look good field kit perhaps could send some pictures column Minolta Weathermatic Dual 35 local camera store Light 12-VDC fluorescent light plugs automobile cigar lighter very handy put couple strips VelcroTM hooks back permit stick light prati cally anywhere cloth interior van sticks very neatly head-liner seat backs comes off easily need another po sition unit draws 06 amps opposed vans interior lights draw 24 amps provides plenty light reading working whatever have separate deep-cycle RV recreational vehicleEd battery van operate re frigerator lights whatever other items might need total capacity RV battery 70 amp-hours refrigerator alone can exhaust about 17 hours Ito fall asleep refrigerator interior lights battery would exhausted 11 hours Sub stituting fluorescent light vans stan dard interior lights will let battery last 15 hours think extra four hours operating time very valuable RV battery course independent battery starts van wont give manufacturer light because have seen similar units K-Mart Radio Shack etc Prop Noise Continued page 44 last factor controlled fi nal choice prop test aircraft An APC 10 x 8 determined best compromise fact maximum flight speed noise level appear similar 9 x 10 prop low-speed thrust greatly improved As airplane/prop combination demon strates now possible operate model aircraft reduced noise levels little no compromise performance hoped propeller manufacturers will follow APC lead developing introducing new lines will benefit aircraft sizes would major step toward preserving community relations ensur ing continued growth hobby 140 Model Aviation Radio Technique/Myers Continued page 107 Celebrating 10 years producing largest selection giant scale kits available today Design building integrity scale fidelity scale flight characteristics standard IKON NWST 22 kits choose Conclusions research program sponsored AMA order gain better understanding propeller noise major objectives determine con tribution propeller makes over aircraft noise isolate main source prop noise latter proved significant establish guidelines would ulti mately lead quieter model aircraft opera tion combination propeller theory experimental data wind tun nel flight tests provided some definitive conclusions 1 In order reduce noise generated model aircraft dominant source must reduced Provided reasonable muffler used propeller domi nant noise source 2 The dominant source propeller noise torque noise Since efficient propellers generate thrust given amount required torque use will re sult less noise given airspeed 3 Propellers currently available mod elers general quite inefficient use such propellers leads less ideal performance acoustic characteris tics 4 Modelers should select propeller peak efficiency occurs near range airspeeds aircraft will usually operated general props increased pitch/diameter ratios must made available allow such integration wide variety aircraft 5 Noise reduction efforts should directed maximum flight speed condi tion way truly quantify noise attempt reduce mea sure flight 6 It possible develop propeller se lection method based in-flight experimental data addresses both noise performance would give aver age modeler means selecting prop would meet noise regulations performing satisfaction 7 This information will useful applied universally will job ganized groups such AMA clubs hobby dealers manufacturers edu cate individuals enforce proper pro cedures research study described series articles has disclosed nature prob lem propeller noise introduced some solutions Using efficient propellers will reduce model aircraft noise However continued research should directed toward studying effect propeller ge ometry overall efficiency should lead optimal blade designs ulti mately minimal propeller noise Finally carefully organized flight test program would provide data base developing standardized propeller selection criterion SAFE FLYING IS NO ACCIDENT Keithsgo latters numbers some known experimental error associated ex act measurement wire length involved physical portion wire near connector itself cases actual length somewhat intended six inches voltage drops would higher expected Whatever wary installation losses plane Use quality wire quality connectorsbut use sparingly Two new speed controls shown photos month First Jomars latesta large control big systems SC 6 mentioned upcoming new product December 1989 column now closer reality control pictured prototype designed operate 22- 34cell systems features new Signetics chip thats designed drive MOSFET metal-oxide semiconductor field-effect rransistorRMcM gates efficiently course its high-frame-rate design optically coupled Tentative list price $130 Joe Utazi tells product line will soon carried distributors across country competitive pricing will drive price other products down Another new control least new writer Horak imported Canada As understand controls handmade Jiri Horak 3403 Fellmore Drive Mississauga Ontar io Canada L5C 2E1 arc scarce supply Jiri makes several versions including ones brakesContinued page 144 March 1990 141 MOIIUUOUP VUA 114 SCALE 96 STITS PLAYBOYWACO UII-7 113 SCALE 88115 SCALE 72 RC Electrics/Kopski Continued page 47
Edition: Model Aviation - 1990/03
Page Numbers: 39, 40, 41, 42, 43, 44, 140, 141
lodel Propeller NOISE three preceding articles discussing findings ex haustive prop noise study conducted North Carolina State University sponsored AMA has demonstrated average commercial propeller inefficient major source model airplane noise engine properly muf fled What can done solve problem discussed concluding segment ER Vess D Heathcoat R Nagel THE PREVIOUS articles four-part series have shown propellers main source model aircraft noise ex plained various sources propeller noise further shown noise due torque loading dominant different sources Last months article con cluded following comments propellers available generally very inefficient inefficiency leads high torque loads relative thrust produced path model aircraft noise reduc tion therefore clear although perhaps easy Making propellers efficient would reduce noise levels compro mising aircraft performance Simply stated means too much work engine spent turning propeller enough used pulling aircraft through air demonstrate fact consider following thought ex periment propeller model aircraft replaced circular rod clear aircraft would able fly motor would work rod would spin great deal noise would generatedbut no thrust would produced round rod terrible propeller noise generated rod propeller would due thick ness cross-sectional diameter torque torque supplied en gine turn quasi propeller order compare noise gen erated particular propeller rod se lected would have size such engine full throttle would turn either rod propeller same rpm means engine would doing same amount work case may surprised learn rod propeller produce similar noise levels similar operating conditions However noise radiating rod has nothing propelling aircraft fore noise due thrust Unfortunately propellers available model ers little too much like rodthey generate large amount torque noise given amount thrust question concerning what can done solve problem depends upon cares responsible Cer tainly people live near flying sites disturbed noise can counted among care local residents often solve problem pro testing such way create new different problem pilotsloss flying site responsibility model aircraft noise does indeed lie fliers manufacturers What can groups combination widespread ed ucation modelers conscientious flying field practices state-of-the-art equip ment will required reach appropri ate workable solution hoped information series articles will pro vide some necessary education Surely manufacturers will continue recognize severity noise issue direct efforts accordingly However its actions individual modelers March 1990 39 Left Argentinean Quique Somenzini displays business end aircraft FAI World Aerobatics Championships Chesapeake VA FutabalYS 12 four-stroke engine turns APC 14 x 14 pro peller muffler Hatori pipe unit added exhaust exten sion Above Somenzinis aircraft held taxiway manda tory static noise readings made measured SPL 855 dBA recorded lowest contest However text re veals limitations applying static readings flight conditions Lower Pitch/Diameter Higher Pitch/Diameter Increoming Airupeed re 1 eller/ Aircraft Matching 120110100-J 0 n C 3 900 C8070 0 Best Fit Line 0 0 08 o -2dBA 0 o0 8090 Predicted SPL dBA will influence continued growth hobby After theyre ones determine what fly isnt difficult understand just sin gle inconsiderate misinformed pilot can create trouble entire club So formation follows will useful accompanied little common sense What t Its model aircraft flying high speeds far runway possibly nearer dis tant houses likely annoy living within proximity flying site typical flight noise runway generally short duration compared time model air noise associated preparation takeoff landing may reaching neighbors Therefore seems obvious strictest noise control efforts should di rected toward high-speed flight condi tion explained first article flying aircraft differs greatly both propel ler performance radiated noise restrained craft ie having no ward motion due differences flow fields around prop case Thus current practice measur ing noise level aircraft being held rest ground fact dealing wrong noise wrong condition wrong place 1989 F3A World Aerobatics Champi onships held Chesapeake VA provided case point FAI competition SPL sound pressure level measured dis tance three meters sideline aircraft must exceed 98 dB quite loud Interestingly enough although aircraft met requirement varying degrees very quiet flighta few point being barely audible fact qualitative stand point planes much quieter air static readings would have suggested can explained examining high-pitch propellers have become pop ular among Pattern fliers prime example particular competition APC 14 x 14 prop Argentinean Quique Somen zinis aircraft measured quietest model meet has proven such propellers perform very well significantly decreasing over noise High-pitch props reach peak efficiency higher flight speeds therefore generate less noise relative other props such speeds However excessive angle tack propeller blades model restrained ground promotes flow separation resulting completely differ ent acoustic signature represent ative case aircraft flight true Somenzinis air craft produced noise level reading 855 dB three meters measured statically must realized low level result flow phenomena dont occur under normal flight conditions fore notably quiet in-flight operation aircraft cannot attributed same factors produced static noise read40 Model Aviation U C U ILl a L a -S 01 S L U 1o1o Figure 2 e Prediction Evaluation PointPropPID 111x764 211x655 311x545 410x770 510x660 610x550 710x550 89x71/283 99x778 109x867 119x556 11 0 N 198dBA 115110m 0 105I oi 100-J estFitLine 0 XMuffler 90-0 Standard 0 High Performance 859095100105110115 Max OASPL Equation 1 dBA Figure 3 e Prediction Evaluation Maximum Airspeed gs What tells us way properly attack model aircraft noise roblem develop some means mea uring sound generated airlane flightwhich its per eived bothersome round course suggesting model aircraft oise should measured flight intro Luces variety logistical problems act just about conceivable method Las practical limitations Fortunately ver possible develop method iredicting model aircraft noise flight rom experimental data acquired under trictly controlled conditions Thus ac ual in-flight measurements could made y qualified individuals proper quipment resulting data could ised create noise prediction method everyday modeler fact same lata could also used predict aircraft erformance would possible Jevelop propeller selection method Nould address both performance noise onsiderations Until recently modelers simply icked two three props listed y engine manufacturer satisfactory engine particular displacement rhis poor way choose propeller rhe proper choice can made neeting specific requirements par icular aircraft/engine combination de ired flight condition good way illus rate point comparing typical rainer powered 40-cu-in engine iigher performance sport aircraft utilizing same engine trainer designed fly low air peeds easily managed begin iers proper propeller case should efficient quiet slow tpeeds depicted Figure 1 Such prop would generally characterized having moderate blade pitch sufficient diame er absorb power generated en gine specified limit airspeed comparison high-performance sport aircraft designed fly much faster Pro pellers best suited such craft ones should reach peak efficiency higher airspeeds indicated sec ond curve figure might achieved increasing pitch-to-diam eter ratio important note since dealing fixed-pitch propellers range high efficiency limited fore propeller selected should peak efficiency occurs likely airspeed particular plane Some compromise performance pos sibly noise will evident other air speeds flight envelope extent performance degradation off de sign conditions has significant effect suitability particular prop given aircraft As preceding example has shown pro peller selection driven aerody namic characteristics aircraft ever great diversity types models flown considerably complicates pro cedure developing single propeller se lection method would applicable model airplanes Dividing model aircraft groups similar aerody namic characteristics would reduce num ber variables Data obtained flight tests aircraft typical certain group could used derive performance acoustic prediction methods would applicable other aircraft group An appropriate prop selection criter ion would based prediction infor mation Consider preliminary example following broad categorization trainers sport aircraft high-performance air craft Since divisions based12 typical maxi mum flight speeds some overlapping11 among categories would expected10 Miss Martha aircraft whtch utilized collect9 flight test data dur- ing course of8 research servesas example advanced sport7 aircraft Thus prediction method6 resulting manipulation research data might5 expected ap ply similar sport aircraft6 Data limitations performance data acquired dur ing tests included airspeed propeller rotational speed down-linked telemetry system acoustic data corres ponding performance readings con sisted OASPL overall sound pressure level values recorded air craft passed over microphone visually interpreted separation distance approxi mately two meters should noted data acquired under less ideal circumstances therefore subject error due following difficulties 1 proper engine needle valve set ting difficult maintain throughout entire series runs resulting inconsist encies available power contribute sim ilar inconsistencies both performance March 1990 41 200PoIntPropP/fl 111x764 211x655 311x545 410x770 c 190510x660 a6lOxS506 E7lOxS50 69x753 99x778 l80109x667 119x55685kmph 0 170Best Fit Line 6 S uffler 2 x 150 0 2 0 140 140150160170180190200 Max flight Speed Equation 2 krtiph Figure 4 ormance Prediction Evaluation Full Throttle o Standard High Performance Noise Constraint C 0 C 0 C 0 C Practical Use Range 0 Airspeed Constraint 9 101112 Diameter inches Figure 5 eller Selection Map acoustic data 2 The simplicity airborne teleme try system limited achievable accuracy performance data recorded ground 3 Varying wind conditions drasti cally different aircraft test speeds contrib uted difficulties consistently flying di rectly over sound-level meter 4 The flyover distances simply judged visual comparison nearby ref erence point therefore subject hu man error should noted however data recorded after re peated within acceptable limits three good passes over microphone list error sources introduced discredit data realistically qual ify extent its accuracy famil iarize reader problem areas need addressed prior performing extensive flight tests Any conclu sions drawn carefully scrutinized potential error mind adjusted accordingly conclu sions derived lab experiments favorably supported flight test data Noise prediction Correlation acous tic data flight tests desired geometric parameters measured propellers data base provided foundation development noise prediction method involved rather tedious task mathematically weighing within single equation contribution individual parameter made overall noise level determining well resulting equation predicted ex perimental values repeating entire process until error minimized result effort following equation actually less threatening appears OASPLpred 110 log D15 log P 40 log NllO log [175 logl JIit]f 10 log 1 8Mt4I [32 log {D-93±15}1151 6429 variables expression describe propeller terms particu lar interest investigation de fined follows D diameter inches P h inches N tional speed rpm o dity outer half prop J nce ratio prop tip Mach number plotting predicted noise against measured noise Figure 2 quality prediction equation can visualized perfect prediction equation would repro duce experimental data exactly means point would collapse onto line unit slope two plotted example slope best fit line through data has value 097 indicates prediction repre sents available data quite well data scatter primarily due exper imental measurement error has calcu lated mean value approximately 2 dBA compares favorably noise prediction equations developed aero space industry Remember though usefulness prediction method deter mined both quality data quality equation equation have given however can predict propeller noise listed variables known Obviously severely limits practical use equation since few modelers have means measuring airspeed engine rpm flight Flying clubs need something simpler work witha method uses easily measured parameters development another equation applies maximum flight speed speed interest way allows significant simplification resulting equation 1 indeed practical since based entirely propeller geome try ruler pocket calculator tools required 1 Max OASPL og [D48 x P/Di x C7SR/R66 x CSOR/C7SRS6S x 625] 4 input variables equation D eller diameter measured inches P/D h-to-diameter ratio CxR eller blade chord measured inches stated location exam ple C5R chord length halfradius position midspan blade R Propeller radius half diameter measured inches Power parameter 10 for standard stock mufflers 105 high-performance mufflers last parameter H serves adjust performance aircraft ex haust system has found socalled high-performance mufflers available modeler today tend increase maximum flight speed general re sult noise speed However model equipped highperformance muffler tested same flight speeds attainable ad vanced muffler noise level remains roughly unchanged comparison results predic tion equation measured results ob 42 Model Aviation Left Several new APC propellers displayed front Miss Martha test aircraft exampies depicted nave diameters rangin nine 11 inches pitches six seven eight 10 inches 9 x 10 propeller mounted 0S Max 46SF engine providec startling flight speeds extremely low noise levels Right John Herbert Raleigh Aeromasters RC Club returns pits after flight An APC 9 x 6 propeller used Goldberg Eaglet powered OS Max 25 engine Although resulting increase max imum flight speed suits style flying proper propeller class aircraft would probably have lower pitch/diameter ratio tc shift peak prop efficiency lower airspeed APC propellers Landing Products distributed through Horizon Distributors SAFE FLYING IS NO ACCIDENT THE BEST FUSELAGE JIG EVER PERIOD Provides Solid Support Accurate Building Rugged Construction 7 Ply Aircraft Plywood Provides Lifetime Use Two Sizes Available Regular Fuselages Up 6 Wide Jumbo Fuselages Up 9 Wide Use Own Building Buard Work Bench Base Mount Jig Station Uni-Strut Guide Rails Most Versatile Set-Up Contains Complete Hardware Instructions Including Uni-Strut Information Buxof4StandardJigStatioflsS1795 Boxof4JumboJigStations1995 Two 5 ft long Guide Rails including mounting nuts 2195 ained Miss Martha aircraft full hrottle given Figure 3 noise pro luced different propellers figire ranges about 87 dBA over 110 dBA Propeller selection made differ ence between quiet aircraft ex tremely noisy However because aforementioned measurement error dif ficult obtain definite conclusions di rectly figure Nevertheless general trends support claim props higher pitch-todiameter ratios produce less noise flight Furthermore examples high-performance muffler used indi cate increased noise levels because engine performing better significance comparison shown Figure 3 demonstrates first possi ble obtain prediction equation ex perimental data second accu racy data controls usefulness such equation Performance prediction As discussed pre viously goal exercise pro duce example propeller selection method addresses both noise per formance performance data acquired flight tests manipulated same manner derive equation would predict maximum flight speed model within same general category sport aircraft ie aerodynamic characteristics similar Miss Martha IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure aileron elevator rudder throw Takes guess work out trimming out airplane quality tool conspiete instructions log book carrying case5795 U PLUG-IN ADJUSTABLE STAB KIT last tan optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matthing phenolic socket 5695 Include 52 SOlItem UPS esidents Add 6% Sales Tax GATOR RIC PRODUCTS 3713 Pompano Dr acola FL 32514 476-8639 test aircraft Equation 2 result such effort Note variables same defined Equation 1 2 Vmax predicted x [DO x PID015 x C7SRIR9 x CSoRIC7SR65 X C9oR/C7SR055 x PH4] Figure 4 presents graphic comparison measured predicted flight velocity error approximately 5% mean flight velocity translates about 85 kmph Comparison figure Fig ure 3 reveals general trend props higher pitch-to-diameter ra tios data base produced highest maximum flight speed lowest noise Once again consistent labo ratory results Propeller selection method further uti lizing prediction equations 1 2 practical method selecting propeller satisfies reasonable noise per formance constraints can developed aircraft categoryie sport air craft. Consider task selecting pro peller meets following criteria Aircraft Miss Martha Advanced level sport Engine 05 Max 46 SF Muffler PLUG-IN WING ADJUSTER KIT Four glass filled nylon brackets included key wing panels front rear allow accurately adjust panel straight flight Complete hardware & InstructIons 5995 WING TUBE & SOCKETS Aluminum alloy tubing plug-in wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2S 895 1diax2S 995 1dias351495 Davis Diesel Soundmaster high perform ance Desired maximum flight speed 175 kmph 109 mph Flying site noise regulation 880 dBA @ two meters flyover ap prox 853 dBA @ three meters Reference should made equations 1 2 Since high-performance muf fler used H Furthermore mea surements taken propellers data base produce following average blade chord distribution C7SR/R C5oR/C75R C9oRIC75R0725 will assumed propeller ques tion has expected blade chord distribu tion substituting known values equations following mathemati cal inequalities may written terms blade pitch diameter both inches 1 P155 x l05 x Noise Constraint 2aP 1 295 X Speed Constraint Plotting both same figure Figure 5 produces finite boundary above pitch/diameter combinations sat isfy constraints can found Examina RDABLE AL POWER INTRODUCTORY 849 SPECIAL SEND 5100 TECHNICAL DATA THE MIKE GR6- 120 2-CYCLE POWERPLANT 6 CYLINDER RADIAL ANTY LBSOFTHRuST * 25 SHP IDYNO TESTEDI * NO VIBRATION III * SINGLE NEEDLE VALVE * 8 STAINLESS BALL BROS * IDLES AT 1800 RPM * OIL LUBRICATED GEARS * 3/8 HARDENED SE SHAFT * FULLY FLIGHT TESTED * DIAMETER 8 TO PLUG TIPS * WEIGHT 4 LEE INCLuDING INTEGRAL MOUNT AND MUFFLER * SWINGS 18/8 PROF /8 8880 RPM * EXCEEDS QuADRA 35 IN POWER AND ZENOAH G38 IN THRUST * GLOW FUEL USED-1S% * GLOW PLUG LEADS INCLUDED * READY TO FLY NOT KITI 33 DEALER INQUIRIESs-% INVITEDp TECHNOLOGIES INC 7 Greenwood Lane VaiSsIla New YorE lOSES 1914 888-9373 FAT PENDING TEST FLOWN IN 72 GM PLASTICS F4U CORSAIR 72 BOB DIVELYS SU-2 BIPLANE 88 PROCTOR NIEUPORT 28 BIPLANE 58 MONOCOUPE EISA March 1990 43 $1695 LIST THE PIPER BRAVE 1/4 scale model Pipers latest Ag plane t wing span 30-33 lbs 5 cc power lb payload ational flaps hopper door onal Spreader Kit formed aluminum landing gear rglass cowls um-formed canopy tucted extruded foam ply hardwood r -Model actually dustingBRKE $269~ OPTIONAL995 SPREADER SEND siee FOR CATALOG OFC/IRT 1 NEODESHA KS 66757 SAC KITS AND ACCESSORIES316 325-2821 Free Shipping Kit OrdersScott Airplane CompanyVISA MASTERCARD tion figure leads obvious con- distribution assumed could have ious props yielded some important observa clusion propellers re- resulted slight shift noise boun- tions Since explained previously thc gion bounded curves either dont dary necessary exclude 9 x 75 prop goal match peak propeller effi exist simply aren t practical use important thing recognize ciency airspeed model i specified engine desirable propeller pitch/diameter ratio often flown performance othex ranges pitch diameter occur near least 083 would required meet se- speeds does suffer consequence Examrange represented data base propel- lection criteria pitch/diameter ratio pIes noticeable performance degradation lers both because prediction increased further might possible op- off design conditions follow equations derived data acquired erate required airspeed less first thing modelers will notice thil such propellers because props out- noise the static rpm will much lower highside range tend subject prob- recent introduction new line pitch props However expected lems area practicality props allows further investigation result flow separation blades Functional propellers must able ab- hypothesis Known APC Advanced Pre- aircraft i5 restrained theres no sorb power available engine cision Composite props line manu- reason discouraged fact follow reasonable rpm must also perform ad- factured California Landing Products rule thumb prop screaminl equately off design situations distributed hobby dealers through ground engine sufficientl rules out propellers too little diameter Horizon Distributors Several examples loadedwhich means flight perform too much pitch example ad- props flown Miss Martha ance will compromised noise ditional boundary sets lower diam- test aircraft evaluated qualitatively creased course direct opposi eter limit 9 might appropriately instrumentation several tion way modelers choose prop inserted Figure 5 Doing con- produced excellent results 9 present fines realistic choices narrow x 10 P/D 111 A second observation takeofi shaded region figure The APC 9 x 10 propeller produced level acceleration will reduced increas time flight testing per- flight speeds never previously attained es takeoff length small amount Du formed highest pitch/diameter ratio other prop aircraft as- excessive thrust-to-weight ratio 01 prop available use type engine tounding observation however model airplanes however 9 x 75 P/DO83 Notice quietness APC prop propeller major problem Figure 5 prop should theoretically quiet airflow around Finally thrust low flight speeds i satisfy constraints example How- plane audible no data has reduced resulting degraded maneuvet ever inspection data propel- acquired props quite obvi- performance Note aircraft fly ler Figure 3 reveals noise con- ous exhibit increased levels effi- ing fast climb rate excellent its straint would met Remember ciency due increased performance model slows down powet though boundaries Figure 5 decreased noise levels is increased nose raised ef derived imperfect experi- Qualitative comparisons takeoff fect becomes apparent mental data average blade chord lengths climb performance var- Continued page 140 PRACTICAL SIZED GIANT SCALE MODEL PLANS Fiberg/ass Cowlings Canopies Available N1 311/2 1140Span54200 F4u CORSAiR2 1/4 193Span$3000 ASMS ZERO2 1/2 Span $3000Plans RK-20 cuRTiS P40 2 1/2 Span $3000 RK-740 Oucted Fans AT-6 TEXAN 24 1 Span $3000 Phaniom 35 Span $1000 FSF BEARCAT 2 1/2 Span $3000 FQKKER OR127163 Viggen32 Span SiO00 Tripe $2700p36 Span $1000 Pian nd canopy$1500 Order FromCredited First Order $25 Nick Ziroli29 Edgar Dr Smithtown NY 11787 USA516-234-5038 44 Model Aviation Mere Fun SPECIFICATIONS Wing Span62'2 inches Wing Area770 square inches Engine Size 10 cc 90 129 four stroke Designed AMA FAI Turn-around pattern Foam wing stab 3-32 Balsa sheet covering Tricycle conven tional gear fixed retracts Rear side exhaust fiber glass canopy Very positive maneuverable XLT SPECIFIC Wing Span65 inches Length65 inches Wing Area845 square inches Recommended Engine Size 10 cc 90 120 four stroke XLT designed tuned pipe re tract landing gears Capable AMA Turn-around pattern Rear side ex haust SPECIFICATIONS Wing Span Wing Area Engine Size 63'4 inches 700 square inches 50-60 Glow 90 four stroke fun sport pattern turn-around can done Utter Chaos completely built up Balsa construction Canopy engine mount included years proven flying reliablity BRIDI AIRCRAFT DESIGNS INC 23625 Pineforest Lane Harbor City California 90710 213 549-8264 326-5013 SEE YOUR FAVORITE HOBBY SHOP OR RETAIL OUTLET Dealer Inquries Invited PRODUCTS Complete Line Exheust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers Expansion Mufflers copter Ball Mufflers ialized Exhaust Systems Unsurpassed Workmaashin & Padormance Inc Chicago IL 60651 Stay-Brite silver solder Stay Clean flux 1W Harris Co 10930 Deerfield Rd Cincinnati OH 45242 Tools SR batteries tool kit contains SAE metric hex wrenches well crosspoint regular screwdriver bits nifty box ratchet drive screwdriver-type handle very handy use love bits fit electric screwdriver should grab interest somewhat greater interest fact can buy single replacement bits should damaged lost Think sel dom can thing like days SR Batteries Inc Box 287 Bellport NY 11713 tel 1-516/286-0079 Wen portable tool kit #2336 has de scribed previous column contains drill motor Dremel-type grinder saber saw sol dering iron plug cigarette lighter 12-VDC receptacle car have kit find uses dont have people snicker idea toy tools look like toys worked like 110VAC tools no trouble cutting A-in ply wood drilling 4-in holes Ford van body parts Portasol butane-fueled soldering iron also described earlier Suffice say worked fine Camera bought Minolta Weather matic Dual 35 main thought might travel salt air splashes possibility being dropped overboard rule Out use expensive cameras lenses camera 0-ring-sealed against dust moisture has corrosion-resistant yellow plastic exterior will float water accepts DXcoded ASA 100 1000 35mm color print film has pushbutton-selected internal 35mm 50mm lenses features automatic film advance/rewind well autofocus nearest focus point two feet 50mm lens focus-hold feature built shutter button just big cameras tiny built-in flash much better no flash 26 x 31 x 58 less pound camera relatively small light nice hiking must carry everything body much dust Alaska stayed outside camera bought camera its weather resistance learned enjoy fact can worked hand ap preciate its durability favorite lens 35mm-to-tOSmm macro zoom can understand felt limited BATT- CHEKEX Saves Time . Saves Models Install RO Models 3-Level indication receiver battery status press button Precise Rugged Small Light /2 oz Made SA Also custom units other applications Order Today si 495 trom dealer send check money order topostpaid Protune Corp 914 462-6452 PO Box 1808 Poughkeepal NY 12601 NY State residents add sales tax non-macro 35/50mm lens selection use found could get about 85% pic tures wanted Thats pretty good compro mise Any camera just tool good general-purpose tool think would look good field kit perhaps could send some pictures column Minolta Weathermatic Dual 35 local camera store Light 12-VDC fluorescent light plugs automobile cigar lighter very handy put couple strips VelcroTM hooks back permit stick light prati cally anywhere cloth interior van sticks very neatly head-liner seat backs comes off easily need another po sition unit draws 06 amps opposed vans interior lights draw 24 amps provides plenty light reading working whatever have separate deep-cycle RV recreational vehicleEd battery van operate re frigerator lights whatever other items might need total capacity RV battery 70 amp-hours refrigerator alone can exhaust about 17 hours Ito fall asleep refrigerator interior lights battery would exhausted 11 hours Sub stituting fluorescent light vans stan dard interior lights will let battery last 15 hours think extra four hours operating time very valuable RV battery course independent battery starts van wont give manufacturer light because have seen similar units K-Mart Radio Shack etc Prop Noise Continued page 44 last factor controlled fi nal choice prop test aircraft An APC 10 x 8 determined best compromise fact maximum flight speed noise level appear similar 9 x 10 prop low-speed thrust greatly improved As airplane/prop combination demon strates now possible operate model aircraft reduced noise levels little no compromise performance hoped propeller manufacturers will follow APC lead developing introducing new lines will benefit aircraft sizes would major step toward preserving community relations ensur ing continued growth hobby 140 Model Aviation Radio Technique/Myers Continued page 107 Celebrating 10 years producing largest selection giant scale kits available today Design building integrity scale fidelity scale flight characteristics standard IKON NWST 22 kits choose Conclusions research program sponsored AMA order gain better understanding propeller noise major objectives determine con tribution propeller makes over aircraft noise isolate main source prop noise latter proved significant establish guidelines would ulti mately lead quieter model aircraft opera tion combination propeller theory experimental data wind tun nel flight tests provided some definitive conclusions 1 In order reduce noise generated model aircraft dominant source must reduced Provided reasonable muffler used propeller domi nant noise source 2 The dominant source propeller noise torque noise Since efficient propellers generate thrust given amount required torque use will re sult less noise given airspeed 3 Propellers currently available mod elers general quite inefficient use such propellers leads less ideal performance acoustic characteris tics 4 Modelers should select propeller peak efficiency occurs near range airspeeds aircraft will usually operated general props increased pitch/diameter ratios must made available allow such integration wide variety aircraft 5 Noise reduction efforts should directed maximum flight speed condi tion way truly quantify noise attempt reduce mea sure flight 6 It possible develop propeller se lection method based in-flight experimental data addresses both noise performance would give aver age modeler means selecting prop would meet noise regulations performing satisfaction 7 This information will useful applied universally will job ganized groups such AMA clubs hobby dealers manufacturers edu cate individuals enforce proper pro cedures research study described series articles has disclosed nature prob lem propeller noise introduced some solutions Using efficient propellers will reduce model aircraft noise However continued research should directed toward studying effect propeller ge ometry overall efficiency should lead optimal blade designs ulti mately minimal propeller noise Finally carefully organized flight test program would provide data base developing standardized propeller selection criterion SAFE FLYING IS NO ACCIDENT Keithsgo latters numbers some known experimental error associated ex act measurement wire length involved physical portion wire near connector itself cases actual length somewhat intended six inches voltage drops would higher expected Whatever wary installation losses plane Use quality wire quality connectorsbut use sparingly Two new speed controls shown photos month First Jomars latesta large control big systems SC 6 mentioned upcoming new product December 1989 column now closer reality control pictured prototype designed operate 22- 34cell systems features new Signetics chip thats designed drive MOSFET metal-oxide semiconductor field-effect rransistorRMcM gates efficiently course its high-frame-rate design optically coupled Tentative list price $130 Joe Utazi tells product line will soon carried distributors across country competitive pricing will drive price other products down Another new control least new writer Horak imported Canada As understand controls handmade Jiri Horak 3403 Fellmore Drive Mississauga Ontar io Canada L5C 2E1 arc scarce supply Jiri makes several versions including ones brakesContinued page 144 March 1990 141 MOIIUUOUP VUA 114 SCALE 96 STITS PLAYBOYWACO UII-7 113 SCALE 88115 SCALE 72 RC Electrics/Kopski Continued page 47
Edition: Model Aviation - 1990/03
Page Numbers: 39, 40, 41, 42, 43, 44, 140, 141
lodel Propeller NOISE three preceding articles discussing findings ex haustive prop noise study conducted North Carolina State University sponsored AMA has demonstrated average commercial propeller inefficient major source model airplane noise engine properly muf fled What can done solve problem discussed concluding segment ER Vess D Heathcoat R Nagel THE PREVIOUS articles four-part series have shown propellers main source model aircraft noise ex plained various sources propeller noise further shown noise due torque loading dominant different sources Last months article con cluded following comments propellers available generally very inefficient inefficiency leads high torque loads relative thrust produced path model aircraft noise reduc tion therefore clear although perhaps easy Making propellers efficient would reduce noise levels compro mising aircraft performance Simply stated means too much work engine spent turning propeller enough used pulling aircraft through air demonstrate fact consider following thought ex periment propeller model aircraft replaced circular rod clear aircraft would able fly motor would work rod would spin great deal noise would generatedbut no thrust would produced round rod terrible propeller noise generated rod propeller would due thick ness cross-sectional diameter torque torque supplied en gine turn quasi propeller order compare noise gen erated particular propeller rod se lected would have size such engine full throttle would turn either rod propeller same rpm means engine would doing same amount work case may surprised learn rod propeller produce similar noise levels similar operating conditions However noise radiating rod has nothing propelling aircraft fore noise due thrust Unfortunately propellers available model ers little too much like rodthey generate large amount torque noise given amount thrust question concerning what can done solve problem depends upon cares responsible Cer tainly people live near flying sites disturbed noise can counted among care local residents often solve problem pro testing such way create new different problem pilotsloss flying site responsibility model aircraft noise does indeed lie fliers manufacturers What can groups combination widespread ed ucation modelers conscientious flying field practices state-of-the-art equip ment will required reach appropri ate workable solution hoped information series articles will pro vide some necessary education Surely manufacturers will continue recognize severity noise issue direct efforts accordingly However its actions individual modelers March 1990 39 Left Argentinean Quique Somenzini displays business end aircraft FAI World Aerobatics Championships Chesapeake VA FutabalYS 12 four-stroke engine turns APC 14 x 14 pro peller muffler Hatori pipe unit added exhaust exten sion Above Somenzinis aircraft held taxiway manda tory static noise readings made measured SPL 855 dBA recorded lowest contest However text re veals limitations applying static readings flight conditions Lower Pitch/Diameter Higher Pitch/Diameter Increoming Airupeed re 1 eller/ Aircraft Matching 120110100-J 0 n C 3 900 C8070 0 Best Fit Line 0 0 08 o -2dBA 0 o0 8090 Predicted SPL dBA will influence continued growth hobby After theyre ones determine what fly isnt difficult understand just sin gle inconsiderate misinformed pilot can create trouble entire club So formation follows will useful accompanied little common sense What t Its model aircraft flying high speeds far runway possibly nearer dis tant houses likely annoy living within proximity flying site typical flight noise runway generally short duration compared time model air noise associated preparation takeoff landing may reaching neighbors Therefore seems obvious strictest noise control efforts should di rected toward high-speed flight condi tion explained first article flying aircraft differs greatly both propel ler performance radiated noise restrained craft ie having no ward motion due differences flow fields around prop case Thus current practice measur ing noise level aircraft being held rest ground fact dealing wrong noise wrong condition wrong place 1989 F3A World Aerobatics Champi onships held Chesapeake VA provided case point FAI competition SPL sound pressure level measured dis tance three meters sideline aircraft must exceed 98 dB quite loud Interestingly enough although aircraft met requirement varying degrees very quiet flighta few point being barely audible fact qualitative stand point planes much quieter air static readings would have suggested can explained examining high-pitch propellers have become pop ular among Pattern fliers prime example particular competition APC 14 x 14 prop Argentinean Quique Somen zinis aircraft measured quietest model meet has proven such propellers perform very well significantly decreasing over noise High-pitch props reach peak efficiency higher flight speeds therefore generate less noise relative other props such speeds However excessive angle tack propeller blades model restrained ground promotes flow separation resulting completely differ ent acoustic signature represent ative case aircraft flight true Somenzinis air craft produced noise level reading 855 dB three meters measured statically must realized low level result flow phenomena dont occur under normal flight conditions fore notably quiet in-flight operation aircraft cannot attributed same factors produced static noise read40 Model Aviation U C U ILl a L a -S 01 S L U 1o1o Figure 2 e Prediction Evaluation PointPropPID 111x764 211x655 311x545 410x770 510x660 610x550 710x550 89x71/283 99x778 109x867 119x556 11 0 N 198dBA 115110m 0 105I oi 100-J estFitLine 0 XMuffler 90-0 Standard 0 High Performance 859095100105110115 Max OASPL Equation 1 dBA Figure 3 e Prediction Evaluation Maximum Airspeed gs What tells us way properly attack model aircraft noise roblem develop some means mea uring sound generated airlane flightwhich its per eived bothersome round course suggesting model aircraft oise should measured flight intro Luces variety logistical problems act just about conceivable method Las practical limitations Fortunately ver possible develop method iredicting model aircraft noise flight rom experimental data acquired under trictly controlled conditions Thus ac ual in-flight measurements could made y qualified individuals proper quipment resulting data could ised create noise prediction method everyday modeler fact same lata could also used predict aircraft erformance would possible Jevelop propeller selection method Nould address both performance noise onsiderations Until recently modelers simply icked two three props listed y engine manufacturer satisfactory engine particular displacement rhis poor way choose propeller rhe proper choice can made neeting specific requirements par icular aircraft/engine combination de ired flight condition good way illus rate point comparing typical rainer powered 40-cu-in engine iigher performance sport aircraft utilizing same engine trainer designed fly low air peeds easily managed begin iers proper propeller case should efficient quiet slow tpeeds depicted Figure 1 Such prop would generally characterized having moderate blade pitch sufficient diame er absorb power generated en gine specified limit airspeed comparison high-performance sport aircraft designed fly much faster Pro pellers best suited such craft ones should reach peak efficiency higher airspeeds indicated sec ond curve figure might achieved increasing pitch-to-diam eter ratio important note since dealing fixed-pitch propellers range high efficiency limited fore propeller selected should peak efficiency occurs likely airspeed particular plane Some compromise performance pos sibly noise will evident other air speeds flight envelope extent performance degradation off de sign conditions has significant effect suitability particular prop given aircraft As preceding example has shown pro peller selection driven aerody namic characteristics aircraft ever great diversity types models flown considerably complicates pro cedure developing single propeller se lection method would applicable model airplanes Dividing model aircraft groups similar aerody namic characteristics would reduce num ber variables Data obtained flight tests aircraft typical certain group could used derive performance acoustic prediction methods would applicable other aircraft group An appropriate prop selection criter ion would based prediction infor mation Consider preliminary example following broad categorization trainers sport aircraft high-performance air craft Since divisions based12 typical maxi mum flight speeds some overlapping11 among categories would expected10 Miss Martha aircraft whtch utilized collect9 flight test data dur- ing course of8 research servesas example advanced sport7 aircraft Thus prediction method6 resulting manipulation research data might5 expected ap ply similar sport aircraft6 Data limitations performance data acquired dur ing tests included airspeed propeller rotational speed down-linked telemetry system acoustic data corres ponding performance readings con sisted OASPL overall sound pressure level values recorded air craft passed over microphone visually interpreted separation distance approxi mately two meters should noted data acquired under less ideal circumstances therefore subject error due following difficulties 1 proper engine needle valve set ting difficult maintain throughout entire series runs resulting inconsist encies available power contribute sim ilar inconsistencies both performance March 1990 41 200PoIntPropP/fl 111x764 211x655 311x545 410x770 c 190510x660 a6lOxS506 E7lOxS50 69x753 99x778 l80109x667 119x55685kmph 0 170Best Fit Line 6 S uffler 2 x 150 0 2 0 140 140150160170180190200 Max flight Speed Equation 2 krtiph Figure 4 ormance Prediction Evaluation Full Throttle o Standard High Performance Noise Constraint C 0 C 0 C 0 C Practical Use Range 0 Airspeed Constraint 9 101112 Diameter inches Figure 5 eller Selection Map acoustic data 2 The simplicity airborne teleme try system limited achievable accuracy performance data recorded ground 3 Varying wind conditions drasti cally different aircraft test speeds contrib uted difficulties consistently flying di rectly over sound-level meter 4 The flyover distances simply judged visual comparison nearby ref erence point therefore subject hu man error should noted however data recorded after re peated within acceptable limits three good passes over microphone list error sources introduced discredit data realistically qual ify extent its accuracy famil iarize reader problem areas need addressed prior performing extensive flight tests Any conclu sions drawn carefully scrutinized potential error mind adjusted accordingly conclu sions derived lab experiments favorably supported flight test data Noise prediction Correlation acous tic data flight tests desired geometric parameters measured propellers data base provided foundation development noise prediction method involved rather tedious task mathematically weighing within single equation contribution individual parameter made overall noise level determining well resulting equation predicted ex perimental values repeating entire process until error minimized result effort following equation actually less threatening appears OASPLpred 110 log D15 log P 40 log NllO log [175 logl JIit]f 10 log 1 8Mt4I [32 log {D-93±15}1151 6429 variables expression describe propeller terms particu lar interest investigation de fined follows D diameter inches P h inches N tional speed rpm o dity outer half prop J nce ratio prop tip Mach number plotting predicted noise against measured noise Figure 2 quality prediction equation can visualized perfect prediction equation would repro duce experimental data exactly means point would collapse onto line unit slope two plotted example slope best fit line through data has value 097 indicates prediction repre sents available data quite well data scatter primarily due exper imental measurement error has calcu lated mean value approximately 2 dBA compares favorably noise prediction equations developed aero space industry Remember though usefulness prediction method deter mined both quality data quality equation equation have given however can predict propeller noise listed variables known Obviously severely limits practical use equation since few modelers have means measuring airspeed engine rpm flight Flying clubs need something simpler work witha method uses easily measured parameters development another equation applies maximum flight speed speed interest way allows significant simplification resulting equation 1 indeed practical since based entirely propeller geome try ruler pocket calculator tools required 1 Max OASPL og [D48 x P/Di x C7SR/R66 x CSOR/C7SRS6S x 625] 4 input variables equation D eller diameter measured inches P/D h-to-diameter ratio CxR eller blade chord measured inches stated location exam ple C5R chord length halfradius position midspan blade R Propeller radius half diameter measured inches Power parameter 10 for standard stock mufflers 105 high-performance mufflers last parameter H serves adjust performance aircraft ex haust system has found socalled high-performance mufflers available modeler today tend increase maximum flight speed general re sult noise speed However model equipped highperformance muffler tested same flight speeds attainable ad vanced muffler noise level remains roughly unchanged comparison results predic tion equation measured results ob 42 Model Aviation Left Several new APC propellers displayed front Miss Martha test aircraft exampies depicted nave diameters rangin nine 11 inches pitches six seven eight 10 inches 9 x 10 propeller mounted 0S Max 46SF engine providec startling flight speeds extremely low noise levels Right John Herbert Raleigh Aeromasters RC Club returns pits after flight An APC 9 x 6 propeller used Goldberg Eaglet powered OS Max 25 engine Although resulting increase max imum flight speed suits style flying proper propeller class aircraft would probably have lower pitch/diameter ratio tc shift peak prop efficiency lower airspeed APC propellers Landing Products distributed through Horizon Distributors SAFE FLYING IS NO ACCIDENT THE BEST FUSELAGE JIG EVER PERIOD Provides Solid Support Accurate Building Rugged Construction 7 Ply Aircraft Plywood Provides Lifetime Use Two Sizes Available Regular Fuselages Up 6 Wide Jumbo Fuselages Up 9 Wide Use Own Building Buard Work Bench Base Mount Jig Station Uni-Strut Guide Rails Most Versatile Set-Up Contains Complete Hardware Instructions Including Uni-Strut Information Buxof4StandardJigStatioflsS1795 Boxof4JumboJigStations1995 Two 5 ft long Guide Rails including mounting nuts 2195 ained Miss Martha aircraft full hrottle given Figure 3 noise pro luced different propellers figire ranges about 87 dBA over 110 dBA Propeller selection made differ ence between quiet aircraft ex tremely noisy However because aforementioned measurement error dif ficult obtain definite conclusions di rectly figure Nevertheless general trends support claim props higher pitch-todiameter ratios produce less noise flight Furthermore examples high-performance muffler used indi cate increased noise levels because engine performing better significance comparison shown Figure 3 demonstrates first possi ble obtain prediction equation ex perimental data second accu racy data controls usefulness such equation Performance prediction As discussed pre viously goal exercise pro duce example propeller selection method addresses both noise per formance performance data acquired flight tests manipulated same manner derive equation would predict maximum flight speed model within same general category sport aircraft ie aerodynamic characteristics similar Miss Martha IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure aileron elevator rudder throw Takes guess work out trimming out airplane quality tool conspiete instructions log book carrying case5795 U PLUG-IN ADJUSTABLE STAB KIT last tan optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matthing phenolic socket 5695 Include 52 SOlItem UPS esidents Add 6% Sales Tax GATOR RIC PRODUCTS 3713 Pompano Dr acola FL 32514 476-8639 test aircraft Equation 2 result such effort Note variables same defined Equation 1 2 Vmax predicted x [DO x PID015 x C7SRIR9 x CSoRIC7SR65 X C9oR/C7SR055 x PH4] Figure 4 presents graphic comparison measured predicted flight velocity error approximately 5% mean flight velocity translates about 85 kmph Comparison figure Fig ure 3 reveals general trend props higher pitch-to-diameter ra tios data base produced highest maximum flight speed lowest noise Once again consistent labo ratory results Propeller selection method further uti lizing prediction equations 1 2 practical method selecting propeller satisfies reasonable noise per formance constraints can developed aircraft categoryie sport air craft. Consider task selecting pro peller meets following criteria Aircraft Miss Martha Advanced level sport Engine 05 Max 46 SF Muffler PLUG-IN WING ADJUSTER KIT Four glass filled nylon brackets included key wing panels front rear allow accurately adjust panel straight flight Complete hardware & InstructIons 5995 WING TUBE & SOCKETS Aluminum alloy tubing plug-in wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2S 895 1diax2S 995 1dias351495 Davis Diesel Soundmaster high perform ance Desired maximum flight speed 175 kmph 109 mph Flying site noise regulation 880 dBA @ two meters flyover ap prox 853 dBA @ three meters Reference should made equations 1 2 Since high-performance muf fler used H Furthermore mea surements taken propellers data base produce following average blade chord distribution C7SR/R C5oR/C75R C9oRIC75R0725 will assumed propeller ques tion has expected blade chord distribu tion substituting known values equations following mathemati cal inequalities may written terms blade pitch diameter both inches 1 P155 x l05 x Noise Constraint 2aP 1 295 X Speed Constraint Plotting both same figure Figure 5 produces finite boundary above pitch/diameter combinations sat isfy constraints can found Examina RDABLE AL POWER INTRODUCTORY 849 SPECIAL SEND 5100 TECHNICAL DATA THE MIKE GR6- 120 2-CYCLE POWERPLANT 6 CYLINDER RADIAL ANTY LBSOFTHRuST * 25 SHP IDYNO TESTEDI * NO VIBRATION III * SINGLE NEEDLE VALVE * 8 STAINLESS BALL BROS * IDLES AT 1800 RPM * OIL LUBRICATED GEARS * 3/8 HARDENED SE SHAFT * FULLY FLIGHT TESTED * DIAMETER 8 TO PLUG TIPS * WEIGHT 4 LEE INCLuDING INTEGRAL MOUNT AND MUFFLER * SWINGS 18/8 PROF /8 8880 RPM * EXCEEDS QuADRA 35 IN POWER AND ZENOAH G38 IN THRUST * GLOW FUEL USED-1S% * GLOW PLUG LEADS INCLUDED * READY TO FLY NOT KITI 33 DEALER INQUIRIESs-% INVITEDp TECHNOLOGIES INC 7 Greenwood Lane VaiSsIla New YorE lOSES 1914 888-9373 FAT PENDING TEST FLOWN IN 72 GM PLASTICS F4U CORSAIR 72 BOB DIVELYS SU-2 BIPLANE 88 PROCTOR NIEUPORT 28 BIPLANE 58 MONOCOUPE EISA March 1990 43 $1695 LIST THE PIPER BRAVE 1/4 scale model Pipers latest Ag plane t wing span 30-33 lbs 5 cc power lb payload ational flaps hopper door onal Spreader Kit formed aluminum landing gear rglass cowls um-formed canopy tucted extruded foam ply hardwood r -Model actually dustingBRKE $269~ OPTIONAL995 SPREADER SEND siee FOR CATALOG OFC/IRT 1 NEODESHA KS 66757 SAC KITS AND ACCESSORIES316 325-2821 Free Shipping Kit OrdersScott Airplane CompanyVISA MASTERCARD tion figure leads obvious con- distribution assumed could have ious props yielded some important observa clusion propellers re- resulted slight shift noise boun- tions Since explained previously thc gion bounded curves either dont dary necessary exclude 9 x 75 prop goal match peak propeller effi exist simply aren t practical use important thing recognize ciency airspeed model i specified engine desirable propeller pitch/diameter ratio often flown performance othex ranges pitch diameter occur near least 083 would required meet se- speeds does suffer consequence Examrange represented data base propel- lection criteria pitch/diameter ratio pIes noticeable performance degradation lers both because prediction increased further might possible op- off design conditions follow equations derived data acquired erate required airspeed less first thing modelers will notice thil such propellers because props out- noise the static rpm will much lower highside range tend subject prob- recent introduction new line pitch props However expected lems area practicality props allows further investigation result flow separation blades Functional propellers must able ab- hypothesis Known APC Advanced Pre- aircraft i5 restrained theres no sorb power available engine cision Composite props line manu- reason discouraged fact follow reasonable rpm must also perform ad- factured California Landing Products rule thumb prop screaminl equately off design situations distributed hobby dealers through ground engine sufficientl rules out propellers too little diameter Horizon Distributors Several examples loadedwhich means flight perform too much pitch example ad- props flown Miss Martha ance will compromised noise ditional boundary sets lower diam- test aircraft evaluated qualitatively creased course direct opposi eter limit 9 might appropriately instrumentation several tion way modelers choose prop inserted Figure 5 Doing con- produced excellent results 9 present fines realistic choices narrow x 10 P/D 111 A second observation takeofi shaded region figure The APC 9 x 10 propeller produced level acceleration will reduced increas time flight testing per- flight speeds never previously attained es takeoff length small amount Du formed highest pitch/diameter ratio other prop aircraft as- excessive thrust-to-weight ratio 01 prop available use type engine tounding observation however model airplanes however 9 x 75 P/DO83 Notice quietness APC prop propeller major problem Figure 5 prop should theoretically quiet airflow around Finally thrust low flight speeds i satisfy constraints example How- plane audible no data has reduced resulting degraded maneuvet ever inspection data propel- acquired props quite obvi- performance Note aircraft fly ler Figure 3 reveals noise con- ous exhibit increased levels effi- ing fast climb rate excellent its straint would met Remember ciency due increased performance model slows down powet though boundaries Figure 5 decreased noise levels is increased nose raised ef derived imperfect experi- Qualitative comparisons takeoff fect becomes apparent mental data average blade chord lengths climb performance var- Continued page 140 PRACTICAL SIZED GIANT SCALE MODEL PLANS Fiberg/ass Cowlings Canopies Available N1 311/2 1140Span54200 F4u CORSAiR2 1/4 193Span$3000 ASMS ZERO2 1/2 Span $3000Plans RK-20 cuRTiS P40 2 1/2 Span $3000 RK-740 Oucted Fans AT-6 TEXAN 24 1 Span $3000 Phaniom 35 Span $1000 FSF BEARCAT 2 1/2 Span $3000 FQKKER OR127163 Viggen32 Span SiO00 Tripe $2700p36 Span $1000 Pian nd canopy$1500 Order FromCredited First Order $25 Nick Ziroli29 Edgar Dr Smithtown NY 11787 USA516-234-5038 44 Model Aviation Mere Fun SPECIFICATIONS Wing Span62'2 inches Wing Area770 square inches Engine Size 10 cc 90 129 four stroke Designed AMA FAI Turn-around pattern Foam wing stab 3-32 Balsa sheet covering Tricycle conven tional gear fixed retracts Rear side exhaust fiber glass canopy Very positive maneuverable XLT SPECIFIC Wing Span65 inches Length65 inches Wing Area845 square inches Recommended Engine Size 10 cc 90 120 four stroke XLT designed tuned pipe re tract landing gears Capable AMA Turn-around pattern Rear side ex haust SPECIFICATIONS Wing Span Wing Area Engine Size 63'4 inches 700 square inches 50-60 Glow 90 four stroke fun sport pattern turn-around can done Utter Chaos completely built up Balsa construction Canopy engine mount included years proven flying reliablity BRIDI AIRCRAFT DESIGNS INC 23625 Pineforest Lane Harbor City California 90710 213 549-8264 326-5013 SEE YOUR FAVORITE HOBBY SHOP OR RETAIL OUTLET Dealer Inquries Invited PRODUCTS Complete Line Exheust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers Expansion Mufflers copter Ball Mufflers ialized Exhaust Systems Unsurpassed Workmaashin & Padormance Inc Chicago IL 60651 Stay-Brite silver solder Stay Clean flux 1W Harris Co 10930 Deerfield Rd Cincinnati OH 45242 Tools SR batteries tool kit contains SAE metric hex wrenches well crosspoint regular screwdriver bits nifty box ratchet drive screwdriver-type handle very handy use love bits fit electric screwdriver should grab interest somewhat greater interest fact can buy single replacement bits should damaged lost Think sel dom can thing like days SR Batteries Inc Box 287 Bellport NY 11713 tel 1-516/286-0079 Wen portable tool kit #2336 has de scribed previous column contains drill motor Dremel-type grinder saber saw sol dering iron plug cigarette lighter 12-VDC receptacle car have kit find uses dont have people snicker idea toy tools look like toys worked like 110VAC tools no trouble cutting A-in ply wood drilling 4-in holes Ford van body parts Portasol butane-fueled soldering iron also described earlier Suffice say worked fine Camera bought Minolta Weather matic Dual 35 main thought might travel salt air splashes possibility being dropped overboard rule Out use expensive cameras lenses camera 0-ring-sealed against dust moisture has corrosion-resistant yellow plastic exterior will float water accepts DXcoded ASA 100 1000 35mm color print film has pushbutton-selected internal 35mm 50mm lenses features automatic film advance/rewind well autofocus nearest focus point two feet 50mm lens focus-hold feature built shutter button just big cameras tiny built-in flash much better no flash 26 x 31 x 58 less pound camera relatively small light nice hiking must carry everything body much dust Alaska stayed outside camera bought camera its weather resistance learned enjoy fact can worked hand ap preciate its durability favorite lens 35mm-to-tOSmm macro zoom can understand felt limited BATT- CHEKEX Saves Time . Saves Models Install RO Models 3-Level indication receiver battery status press button Precise Rugged Small Light /2 oz Made SA Also custom units other applications Order Today si 495 trom dealer send check money order topostpaid Protune Corp 914 462-6452 PO Box 1808 Poughkeepal NY 12601 NY State residents add sales tax non-macro 35/50mm lens selection use found could get about 85% pic tures wanted Thats pretty good compro mise Any camera just tool good general-purpose tool think would look good field kit perhaps could send some pictures column Minolta Weathermatic Dual 35 local camera store Light 12-VDC fluorescent light plugs automobile cigar lighter very handy put couple strips VelcroTM hooks back permit stick light prati cally anywhere cloth interior van sticks very neatly head-liner seat backs comes off easily need another po sition unit draws 06 amps opposed vans interior lights draw 24 amps provides plenty light reading working whatever have separate deep-cycle RV recreational vehicleEd battery van operate re frigerator lights whatever other items might need total capacity RV battery 70 amp-hours refrigerator alone can exhaust about 17 hours Ito fall asleep refrigerator interior lights battery would exhausted 11 hours Sub stituting fluorescent light vans stan dard interior lights will let battery last 15 hours think extra four hours operating time very valuable RV battery course independent battery starts van wont give manufacturer light because have seen similar units K-Mart Radio Shack etc Prop Noise Continued page 44 last factor controlled fi nal choice prop test aircraft An APC 10 x 8 determined best compromise fact maximum flight speed noise level appear similar 9 x 10 prop low-speed thrust greatly improved As airplane/prop combination demon strates now possible operate model aircraft reduced noise levels little no compromise performance hoped propeller manufacturers will follow APC lead developing introducing new lines will benefit aircraft sizes would major step toward preserving community relations ensur ing continued growth hobby 140 Model Aviation Radio Technique/Myers Continued page 107 Celebrating 10 years producing largest selection giant scale kits available today Design building integrity scale fidelity scale flight characteristics standard IKON NWST 22 kits choose Conclusions research program sponsored AMA order gain better understanding propeller noise major objectives determine con tribution propeller makes over aircraft noise isolate main source prop noise latter proved significant establish guidelines would ulti mately lead quieter model aircraft opera tion combination propeller theory experimental data wind tun nel flight tests provided some definitive conclusions 1 In order reduce noise generated model aircraft dominant source must reduced Provided reasonable muffler used propeller domi nant noise source 2 The dominant source propeller noise torque noise Since efficient propellers generate thrust given amount required torque use will re sult less noise given airspeed 3 Propellers currently available mod elers general quite inefficient use such propellers leads less ideal performance acoustic characteris tics 4 Modelers should select propeller peak efficiency occurs near range airspeeds aircraft will usually operated general props increased pitch/diameter ratios must made available allow such integration wide variety aircraft 5 Noise reduction efforts should directed maximum flight speed condi tion way truly quantify noise attempt reduce mea sure flight 6 It possible develop propeller se lection method based in-flight experimental data addresses both noise performance would give aver age modeler means selecting prop would meet noise regulations performing satisfaction 7 This information will useful applied universally will job ganized groups such AMA clubs hobby dealers manufacturers edu cate individuals enforce proper pro cedures research study described series articles has disclosed nature prob lem propeller noise introduced some solutions Using efficient propellers will reduce model aircraft noise However continued research should directed toward studying effect propeller ge ometry overall efficiency should lead optimal blade designs ulti mately minimal propeller noise Finally carefully organized flight test program would provide data base developing standardized propeller selection criterion SAFE FLYING IS NO ACCIDENT Keithsgo latters numbers some known experimental error associated ex act measurement wire length involved physical portion wire near connector itself cases actual length somewhat intended six inches voltage drops would higher expected Whatever wary installation losses plane Use quality wire quality connectorsbut use sparingly Two new speed controls shown photos month First Jomars latesta large control big systems SC 6 mentioned upcoming new product December 1989 column now closer reality control pictured prototype designed operate 22- 34cell systems features new Signetics chip thats designed drive MOSFET metal-oxide semiconductor field-effect rransistorRMcM gates efficiently course its high-frame-rate design optically coupled Tentative list price $130 Joe Utazi tells product line will soon carried distributors across country competitive pricing will drive price other products down Another new control least new writer Horak imported Canada As understand controls handmade Jiri Horak 3403 Fellmore Drive Mississauga Ontar io Canada L5C 2E1 arc scarce supply Jiri makes several versions including ones brakesContinued page 144 March 1990 141 MOIIUUOUP VUA 114 SCALE 96 STITS PLAYBOYWACO UII-7 113 SCALE 88115 SCALE 72 RC Electrics/Kopski Continued page 47
Edition: Model Aviation - 1990/03
Page Numbers: 39, 40, 41, 42, 43, 44, 140, 141
lodel Propeller NOISE three preceding articles discussing findings ex haustive prop noise study conducted North Carolina State University sponsored AMA has demonstrated average commercial propeller inefficient major source model airplane noise engine properly muf fled What can done solve problem discussed concluding segment ER Vess D Heathcoat R Nagel THE PREVIOUS articles four-part series have shown propellers main source model aircraft noise ex plained various sources propeller noise further shown noise due torque loading dominant different sources Last months article con cluded following comments propellers available generally very inefficient inefficiency leads high torque loads relative thrust produced path model aircraft noise reduc tion therefore clear although perhaps easy Making propellers efficient would reduce noise levels compro mising aircraft performance Simply stated means too much work engine spent turning propeller enough used pulling aircraft through air demonstrate fact consider following thought ex periment propeller model aircraft replaced circular rod clear aircraft would able fly motor would work rod would spin great deal noise would generatedbut no thrust would produced round rod terrible propeller noise generated rod propeller would due thick ness cross-sectional diameter torque torque supplied en gine turn quasi propeller order compare noise gen erated particular propeller rod se lected would have size such engine full throttle would turn either rod propeller same rpm means engine would doing same amount work case may surprised learn rod propeller produce similar noise levels similar operating conditions However noise radiating rod has nothing propelling aircraft fore noise due thrust Unfortunately propellers available model ers little too much like rodthey generate large amount torque noise given amount thrust question concerning what can done solve problem depends upon cares responsible Cer tainly people live near flying sites disturbed noise can counted among care local residents often solve problem pro testing such way create new different problem pilotsloss flying site responsibility model aircraft noise does indeed lie fliers manufacturers What can groups combination widespread ed ucation modelers conscientious flying field practices state-of-the-art equip ment will required reach appropri ate workable solution hoped information series articles will pro vide some necessary education Surely manufacturers will continue recognize severity noise issue direct efforts accordingly However its actions individual modelers March 1990 39 Left Argentinean Quique Somenzini displays business end aircraft FAI World Aerobatics Championships Chesapeake VA FutabalYS 12 four-stroke engine turns APC 14 x 14 pro peller muffler Hatori pipe unit added exhaust exten sion Above Somenzinis aircraft held taxiway manda tory static noise readings made measured SPL 855 dBA recorded lowest contest However text re veals limitations applying static readings flight conditions Lower Pitch/Diameter Higher Pitch/Diameter Increoming Airupeed re 1 eller/ Aircraft Matching 120110100-J 0 n C 3 900 C8070 0 Best Fit Line 0 0 08 o -2dBA 0 o0 8090 Predicted SPL dBA will influence continued growth hobby After theyre ones determine what fly isnt difficult understand just sin gle inconsiderate misinformed pilot can create trouble entire club So formation follows will useful accompanied little common sense What t Its model aircraft flying high speeds far runway possibly nearer dis tant houses likely annoy living within proximity flying site typical flight noise runway generally short duration compared time model air noise associated preparation takeoff landing may reaching neighbors Therefore seems obvious strictest noise control efforts should di rected toward high-speed flight condi tion explained first article flying aircraft differs greatly both propel ler performance radiated noise restrained craft ie having no ward motion due differences flow fields around prop case Thus current practice measur ing noise level aircraft being held rest ground fact dealing wrong noise wrong condition wrong place 1989 F3A World Aerobatics Champi onships held Chesapeake VA provided case point FAI competition SPL sound pressure level measured dis tance three meters sideline aircraft must exceed 98 dB quite loud Interestingly enough although aircraft met requirement varying degrees very quiet flighta few point being barely audible fact qualitative stand point planes much quieter air static readings would have suggested can explained examining high-pitch propellers have become pop ular among Pattern fliers prime example particular competition APC 14 x 14 prop Argentinean Quique Somen zinis aircraft measured quietest model meet has proven such propellers perform very well significantly decreasing over noise High-pitch props reach peak efficiency higher flight speeds therefore generate less noise relative other props such speeds However excessive angle tack propeller blades model restrained ground promotes flow separation resulting completely differ ent acoustic signature represent ative case aircraft flight true Somenzinis air craft produced noise level reading 855 dB three meters measured statically must realized low level result flow phenomena dont occur under normal flight conditions fore notably quiet in-flight operation aircraft cannot attributed same factors produced static noise read40 Model Aviation U C U ILl a L a -S 01 S L U 1o1o Figure 2 e Prediction Evaluation PointPropPID 111x764 211x655 311x545 410x770 510x660 610x550 710x550 89x71/283 99x778 109x867 119x556 11 0 N 198dBA 115110m 0 105I oi 100-J estFitLine 0 XMuffler 90-0 Standard 0 High Performance 859095100105110115 Max OASPL Equation 1 dBA Figure 3 e Prediction Evaluation Maximum Airspeed gs What tells us way properly attack model aircraft noise roblem develop some means mea uring sound generated airlane flightwhich its per eived bothersome round course suggesting model aircraft oise should measured flight intro Luces variety logistical problems act just about conceivable method Las practical limitations Fortunately ver possible develop method iredicting model aircraft noise flight rom experimental data acquired under trictly controlled conditions Thus ac ual in-flight measurements could made y qualified individuals proper quipment resulting data could ised create noise prediction method everyday modeler fact same lata could also used predict aircraft erformance would possible Jevelop propeller selection method Nould address both performance noise onsiderations Until recently modelers simply icked two three props listed y engine manufacturer satisfactory engine particular displacement rhis poor way choose propeller rhe proper choice can made neeting specific requirements par icular aircraft/engine combination de ired flight condition good way illus rate point comparing typical rainer powered 40-cu-in engine iigher performance sport aircraft utilizing same engine trainer designed fly low air peeds easily managed begin iers proper propeller case should efficient quiet slow tpeeds depicted Figure 1 Such prop would generally characterized having moderate blade pitch sufficient diame er absorb power generated en gine specified limit airspeed comparison high-performance sport aircraft designed fly much faster Pro pellers best suited such craft ones should reach peak efficiency higher airspeeds indicated sec ond curve figure might achieved increasing pitch-to-diam eter ratio important note since dealing fixed-pitch propellers range high efficiency limited fore propeller selected should peak efficiency occurs likely airspeed particular plane Some compromise performance pos sibly noise will evident other air speeds flight envelope extent performance degradation off de sign conditions has significant effect suitability particular prop given aircraft As preceding example has shown pro peller selection driven aerody namic characteristics aircraft ever great diversity types models flown considerably complicates pro cedure developing single propeller se lection method would applicable model airplanes Dividing model aircraft groups similar aerody namic characteristics would reduce num ber variables Data obtained flight tests aircraft typical certain group could used derive performance acoustic prediction methods would applicable other aircraft group An appropriate prop selection criter ion would based prediction infor mation Consider preliminary example following broad categorization trainers sport aircraft high-performance air craft Since divisions based12 typical maxi mum flight speeds some overlapping11 among categories would expected10 Miss Martha aircraft whtch utilized collect9 flight test data dur- ing course of8 research servesas example advanced sport7 aircraft Thus prediction method6 resulting manipulation research data might5 expected ap ply similar sport aircraft6 Data limitations performance data acquired dur ing tests included airspeed propeller rotational speed down-linked telemetry system acoustic data corres ponding performance readings con sisted OASPL overall sound pressure level values recorded air craft passed over microphone visually interpreted separation distance approxi mately two meters should noted data acquired under less ideal circumstances therefore subject error due following difficulties 1 proper engine needle valve set ting difficult maintain throughout entire series runs resulting inconsist encies available power contribute sim ilar inconsistencies both performance March 1990 41 200PoIntPropP/fl 111x764 211x655 311x545 410x770 c 190510x660 a6lOxS506 E7lOxS50 69x753 99x778 l80109x667 119x55685kmph 0 170Best Fit Line 6 S uffler 2 x 150 0 2 0 140 140150160170180190200 Max flight Speed Equation 2 krtiph Figure 4 ormance Prediction Evaluation Full Throttle o Standard High Performance Noise Constraint C 0 C 0 C 0 C Practical Use Range 0 Airspeed Constraint 9 101112 Diameter inches Figure 5 eller Selection Map acoustic data 2 The simplicity airborne teleme try system limited achievable accuracy performance data recorded ground 3 Varying wind conditions drasti cally different aircraft test speeds contrib uted difficulties consistently flying di rectly over sound-level meter 4 The flyover distances simply judged visual comparison nearby ref erence point therefore subject hu man error should noted however data recorded after re peated within acceptable limits three good passes over microphone list error sources introduced discredit data realistically qual ify extent its accuracy famil iarize reader problem areas need addressed prior performing extensive flight tests Any conclu sions drawn carefully scrutinized potential error mind adjusted accordingly conclu sions derived lab experiments favorably supported flight test data Noise prediction Correlation acous tic data flight tests desired geometric parameters measured propellers data base provided foundation development noise prediction method involved rather tedious task mathematically weighing within single equation contribution individual parameter made overall noise level determining well resulting equation predicted ex perimental values repeating entire process until error minimized result effort following equation actually less threatening appears OASPLpred 110 log D15 log P 40 log NllO log [175 logl JIit]f 10 log 1 8Mt4I [32 log {D-93±15}1151 6429 variables expression describe propeller terms particu lar interest investigation de fined follows D diameter inches P h inches N tional speed rpm o dity outer half prop J nce ratio prop tip Mach number plotting predicted noise against measured noise Figure 2 quality prediction equation can visualized perfect prediction equation would repro duce experimental data exactly means point would collapse onto line unit slope two plotted example slope best fit line through data has value 097 indicates prediction repre sents available data quite well data scatter primarily due exper imental measurement error has calcu lated mean value approximately 2 dBA compares favorably noise prediction equations developed aero space industry Remember though usefulness prediction method deter mined both quality data quality equation equation have given however can predict propeller noise listed variables known Obviously severely limits practical use equation since few modelers have means measuring airspeed engine rpm flight Flying clubs need something simpler work witha method uses easily measured parameters development another equation applies maximum flight speed speed interest way allows significant simplification resulting equation 1 indeed practical since based entirely propeller geome try ruler pocket calculator tools required 1 Max OASPL og [D48 x P/Di x C7SR/R66 x CSOR/C7SRS6S x 625] 4 input variables equation D eller diameter measured inches P/D h-to-diameter ratio CxR eller blade chord measured inches stated location exam ple C5R chord length halfradius position midspan blade R Propeller radius half diameter measured inches Power parameter 10 for standard stock mufflers 105 high-performance mufflers last parameter H serves adjust performance aircraft ex haust system has found socalled high-performance mufflers available modeler today tend increase maximum flight speed general re sult noise speed However model equipped highperformance muffler tested same flight speeds attainable ad vanced muffler noise level remains roughly unchanged comparison results predic tion equation measured results ob 42 Model Aviation Left Several new APC propellers displayed front Miss Martha test aircraft exampies depicted nave diameters rangin nine 11 inches pitches six seven eight 10 inches 9 x 10 propeller mounted 0S Max 46SF engine providec startling flight speeds extremely low noise levels Right John Herbert Raleigh Aeromasters RC Club returns pits after flight An APC 9 x 6 propeller used Goldberg Eaglet powered OS Max 25 engine Although resulting increase max imum flight speed suits style flying proper propeller class aircraft would probably have lower pitch/diameter ratio tc shift peak prop efficiency lower airspeed APC propellers Landing Products distributed through Horizon Distributors SAFE FLYING IS NO ACCIDENT THE BEST FUSELAGE JIG EVER PERIOD Provides Solid Support Accurate Building Rugged Construction 7 Ply Aircraft Plywood Provides Lifetime Use Two Sizes Available Regular Fuselages Up 6 Wide Jumbo Fuselages Up 9 Wide Use Own Building Buard Work Bench Base Mount Jig Station Uni-Strut Guide Rails Most Versatile Set-Up Contains Complete Hardware Instructions Including Uni-Strut Information Buxof4StandardJigStatioflsS1795 Boxof4JumboJigStations1995 Two 5 ft long Guide Rails including mounting nuts 2195 ained Miss Martha aircraft full hrottle given Figure 3 noise pro luced different propellers figire ranges about 87 dBA over 110 dBA Propeller selection made differ ence between quiet aircraft ex tremely noisy However because aforementioned measurement error dif ficult obtain definite conclusions di rectly figure Nevertheless general trends support claim props higher pitch-todiameter ratios produce less noise flight Furthermore examples high-performance muffler used indi cate increased noise levels because engine performing better significance comparison shown Figure 3 demonstrates first possi ble obtain prediction equation ex perimental data second accu racy data controls usefulness such equation Performance prediction As discussed pre viously goal exercise pro duce example propeller selection method addresses both noise per formance performance data acquired flight tests manipulated same manner derive equation would predict maximum flight speed model within same general category sport aircraft ie aerodynamic characteristics similar Miss Martha IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure aileron elevator rudder throw Takes guess work out trimming out airplane quality tool conspiete instructions log book carrying case5795 U PLUG-IN ADJUSTABLE STAB KIT last tan optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matthing phenolic socket 5695 Include 52 SOlItem UPS esidents Add 6% Sales Tax GATOR RIC PRODUCTS 3713 Pompano Dr acola FL 32514 476-8639 test aircraft Equation 2 result such effort Note variables same defined Equation 1 2 Vmax predicted x [DO x PID015 x C7SRIR9 x CSoRIC7SR65 X C9oR/C7SR055 x PH4] Figure 4 presents graphic comparison measured predicted flight velocity error approximately 5% mean flight velocity translates about 85 kmph Comparison figure Fig ure 3 reveals general trend props higher pitch-to-diameter ra tios data base produced highest maximum flight speed lowest noise Once again consistent labo ratory results Propeller selection method further uti lizing prediction equations 1 2 practical method selecting propeller satisfies reasonable noise per formance constraints can developed aircraft categoryie sport air craft. Consider task selecting pro peller meets following criteria Aircraft Miss Martha Advanced level sport Engine 05 Max 46 SF Muffler PLUG-IN WING ADJUSTER KIT Four glass filled nylon brackets included key wing panels front rear allow accurately adjust panel straight flight Complete hardware & InstructIons 5995 WING TUBE & SOCKETS Aluminum alloy tubing plug-in wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2S 895 1diax2S 995 1dias351495 Davis Diesel Soundmaster high perform ance Desired maximum flight speed 175 kmph 109 mph Flying site noise regulation 880 dBA @ two meters flyover ap prox 853 dBA @ three meters Reference should made equations 1 2 Since high-performance muf fler used H Furthermore mea surements taken propellers data base produce following average blade chord distribution C7SR/R C5oR/C75R C9oRIC75R0725 will assumed propeller ques tion has expected blade chord distribu tion substituting known values equations following mathemati cal inequalities may written terms blade pitch diameter both inches 1 P155 x l05 x Noise Constraint 2aP 1 295 X Speed Constraint Plotting both same figure Figure 5 produces finite boundary above pitch/diameter combinations sat isfy constraints can found Examina RDABLE AL POWER INTRODUCTORY 849 SPECIAL SEND 5100 TECHNICAL DATA THE MIKE GR6- 120 2-CYCLE POWERPLANT 6 CYLINDER RADIAL ANTY LBSOFTHRuST * 25 SHP IDYNO TESTEDI * NO VIBRATION III * SINGLE NEEDLE VALVE * 8 STAINLESS BALL BROS * IDLES AT 1800 RPM * OIL LUBRICATED GEARS * 3/8 HARDENED SE SHAFT * FULLY FLIGHT TESTED * DIAMETER 8 TO PLUG TIPS * WEIGHT 4 LEE INCLuDING INTEGRAL MOUNT AND MUFFLER * SWINGS 18/8 PROF /8 8880 RPM * EXCEEDS QuADRA 35 IN POWER AND ZENOAH G38 IN THRUST * GLOW FUEL USED-1S% * GLOW PLUG LEADS INCLUDED * READY TO FLY NOT KITI 33 DEALER INQUIRIESs-% INVITEDp TECHNOLOGIES INC 7 Greenwood Lane VaiSsIla New YorE lOSES 1914 888-9373 FAT PENDING TEST FLOWN IN 72 GM PLASTICS F4U CORSAIR 72 BOB DIVELYS SU-2 BIPLANE 88 PROCTOR NIEUPORT 28 BIPLANE 58 MONOCOUPE EISA March 1990 43 $1695 LIST THE PIPER BRAVE 1/4 scale model Pipers latest Ag plane t wing span 30-33 lbs 5 cc power lb payload ational flaps hopper door onal Spreader Kit formed aluminum landing gear rglass cowls um-formed canopy tucted extruded foam ply hardwood r -Model actually dustingBRKE $269~ OPTIONAL995 SPREADER SEND siee FOR CATALOG OFC/IRT 1 NEODESHA KS 66757 SAC KITS AND ACCESSORIES316 325-2821 Free Shipping Kit OrdersScott Airplane CompanyVISA MASTERCARD tion figure leads obvious con- distribution assumed could have ious props yielded some important observa clusion propellers re- resulted slight shift noise boun- tions Since explained previously thc gion bounded curves either dont dary necessary exclude 9 x 75 prop goal match peak propeller effi exist simply aren t practical use important thing recognize ciency airspeed model i specified engine desirable propeller pitch/diameter ratio often flown performance othex ranges pitch diameter occur near least 083 would required meet se- speeds does suffer consequence Examrange represented data base propel- lection criteria pitch/diameter ratio pIes noticeable performance degradation lers both because prediction increased further might possible op- off design conditions follow equations derived data acquired erate required airspeed less first thing modelers will notice thil such propellers because props out- noise the static rpm will much lower highside range tend subject prob- recent introduction new line pitch props However expected lems area practicality props allows further investigation result flow separation blades Functional propellers must able ab- hypothesis Known APC Advanced Pre- aircraft i5 restrained theres no sorb power available engine cision Composite props line manu- reason discouraged fact follow reasonable rpm must also perform ad- factured California Landing Products rule thumb prop screaminl equately off design situations distributed hobby dealers through ground engine sufficientl rules out propellers too little diameter Horizon Distributors Several examples loadedwhich means flight perform too much pitch example ad- props flown Miss Martha ance will compromised noise ditional boundary sets lower diam- test aircraft evaluated qualitatively creased course direct opposi eter limit 9 might appropriately instrumentation several tion way modelers choose prop inserted Figure 5 Doing con- produced excellent results 9 present fines realistic choices narrow x 10 P/D 111 A second observation takeofi shaded region figure The APC 9 x 10 propeller produced level acceleration will reduced increas time flight testing per- flight speeds never previously attained es takeoff length small amount Du formed highest pitch/diameter ratio other prop aircraft as- excessive thrust-to-weight ratio 01 prop available use type engine tounding observation however model airplanes however 9 x 75 P/DO83 Notice quietness APC prop propeller major problem Figure 5 prop should theoretically quiet airflow around Finally thrust low flight speeds i satisfy constraints example How- plane audible no data has reduced resulting degraded maneuvet ever inspection data propel- acquired props quite obvi- performance Note aircraft fly ler Figure 3 reveals noise con- ous exhibit increased levels effi- ing fast climb rate excellent its straint would met Remember ciency due increased performance model slows down powet though boundaries Figure 5 decreased noise levels is increased nose raised ef derived imperfect experi- Qualitative comparisons takeoff fect becomes apparent mental data average blade chord lengths climb performance var- Continued page 140 PRACTICAL SIZED GIANT SCALE MODEL PLANS Fiberg/ass Cowlings Canopies Available N1 311/2 1140Span54200 F4u CORSAiR2 1/4 193Span$3000 ASMS ZERO2 1/2 Span $3000Plans RK-20 cuRTiS P40 2 1/2 Span $3000 RK-740 Oucted Fans AT-6 TEXAN 24 1 Span $3000 Phaniom 35 Span $1000 FSF BEARCAT 2 1/2 Span $3000 FQKKER OR127163 Viggen32 Span SiO00 Tripe $2700p36 Span $1000 Pian nd canopy$1500 Order FromCredited First Order $25 Nick Ziroli29 Edgar Dr Smithtown NY 11787 USA516-234-5038 44 Model Aviation Mere Fun SPECIFICATIONS Wing Span62'2 inches Wing Area770 square inches Engine Size 10 cc 90 129 four stroke Designed AMA FAI Turn-around pattern Foam wing stab 3-32 Balsa sheet covering Tricycle conven tional gear fixed retracts Rear side exhaust fiber glass canopy Very positive maneuverable XLT SPECIFIC Wing Span65 inches Length65 inches Wing Area845 square inches Recommended Engine Size 10 cc 90 120 four stroke XLT designed tuned pipe re tract landing gears Capable AMA Turn-around pattern Rear side ex haust SPECIFICATIONS Wing Span Wing Area Engine Size 63'4 inches 700 square inches 50-60 Glow 90 four stroke fun sport pattern turn-around can done Utter Chaos completely built up Balsa construction Canopy engine mount included years proven flying reliablity BRIDI AIRCRAFT DESIGNS INC 23625 Pineforest Lane Harbor City California 90710 213 549-8264 326-5013 SEE YOUR FAVORITE HOBBY SHOP OR RETAIL OUTLET Dealer Inquries Invited PRODUCTS Complete Line Exheust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers Expansion Mufflers copter Ball Mufflers ialized Exhaust Systems Unsurpassed Workmaashin & Padormance Inc Chicago IL 60651 Stay-Brite silver solder Stay Clean flux 1W Harris Co 10930 Deerfield Rd Cincinnati OH 45242 Tools SR batteries tool kit contains SAE metric hex wrenches well crosspoint regular screwdriver bits nifty box ratchet drive screwdriver-type handle very handy use love bits fit electric screwdriver should grab interest somewhat greater interest fact can buy single replacement bits should damaged lost Think sel dom can thing like days SR Batteries Inc Box 287 Bellport NY 11713 tel 1-516/286-0079 Wen portable tool kit #2336 has de scribed previous column contains drill motor Dremel-type grinder saber saw sol dering iron plug cigarette lighter 12-VDC receptacle car have kit find uses dont have people snicker idea toy tools look like toys worked like 110VAC tools no trouble cutting A-in ply wood drilling 4-in holes Ford van body parts Portasol butane-fueled soldering iron also described earlier Suffice say worked fine Camera bought Minolta Weather matic Dual 35 main thought might travel salt air splashes possibility being dropped overboard rule Out use expensive cameras lenses camera 0-ring-sealed against dust moisture has corrosion-resistant yellow plastic exterior will float water accepts DXcoded ASA 100 1000 35mm color print film has pushbutton-selected internal 35mm 50mm lenses features automatic film advance/rewind well autofocus nearest focus point two feet 50mm lens focus-hold feature built shutter button just big cameras tiny built-in flash much better no flash 26 x 31 x 58 less pound camera relatively small light nice hiking must carry everything body much dust Alaska stayed outside camera bought camera its weather resistance learned enjoy fact can worked hand ap preciate its durability favorite lens 35mm-to-tOSmm macro zoom can understand felt limited BATT- CHEKEX Saves Time . Saves Models Install RO Models 3-Level indication receiver battery status press button Precise Rugged Small Light /2 oz Made SA Also custom units other applications Order Today si 495 trom dealer send check money order topostpaid Protune Corp 914 462-6452 PO Box 1808 Poughkeepal NY 12601 NY State residents add sales tax non-macro 35/50mm lens selection use found could get about 85% pic tures wanted Thats pretty good compro mise Any camera just tool good general-purpose tool think would look good field kit perhaps could send some pictures column Minolta Weathermatic Dual 35 local camera store Light 12-VDC fluorescent light plugs automobile cigar lighter very handy put couple strips VelcroTM hooks back permit stick light prati cally anywhere cloth interior van sticks very neatly head-liner seat backs comes off easily need another po sition unit draws 06 amps opposed vans interior lights draw 24 amps provides plenty light reading working whatever have separate deep-cycle RV recreational vehicleEd battery van operate re frigerator lights whatever other items might need total capacity RV battery 70 amp-hours refrigerator alone can exhaust about 17 hours Ito fall asleep refrigerator interior lights battery would exhausted 11 hours Sub stituting fluorescent light vans stan dard interior lights will let battery last 15 hours think extra four hours operating time very valuable RV battery course independent battery starts van wont give manufacturer light because have seen similar units K-Mart Radio Shack etc Prop Noise Continued page 44 last factor controlled fi nal choice prop test aircraft An APC 10 x 8 determined best compromise fact maximum flight speed noise level appear similar 9 x 10 prop low-speed thrust greatly improved As airplane/prop combination demon strates now possible operate model aircraft reduced noise levels little no compromise performance hoped propeller manufacturers will follow APC lead developing introducing new lines will benefit aircraft sizes would major step toward preserving community relations ensur ing continued growth hobby 140 Model Aviation Radio Technique/Myers Continued page 107 Celebrating 10 years producing largest selection giant scale kits available today Design building integrity scale fidelity scale flight characteristics standard IKON NWST 22 kits choose Conclusions research program sponsored AMA order gain better understanding propeller noise major objectives determine con tribution propeller makes over aircraft noise isolate main source prop noise latter proved significant establish guidelines would ulti mately lead quieter model aircraft opera tion combination propeller theory experimental data wind tun nel flight tests provided some definitive conclusions 1 In order reduce noise generated model aircraft dominant source must reduced Provided reasonable muffler used propeller domi nant noise source 2 The dominant source propeller noise torque noise Since efficient propellers generate thrust given amount required torque use will re sult less noise given airspeed 3 Propellers currently available mod elers general quite inefficient use such propellers leads less ideal performance acoustic characteris tics 4 Modelers should select propeller peak efficiency occurs near range airspeeds aircraft will usually operated general props increased pitch/diameter ratios must made available allow such integration wide variety aircraft 5 Noise reduction efforts should directed maximum flight speed condi tion way truly quantify noise attempt reduce mea sure flight 6 It possible develop propeller se lection method based in-flight experimental data addresses both noise performance would give aver age modeler means selecting prop would meet noise regulations performing satisfaction 7 This information will useful applied universally will job ganized groups such AMA clubs hobby dealers manufacturers edu cate individuals enforce proper pro cedures research study described series articles has disclosed nature prob lem propeller noise introduced some solutions Using efficient propellers will reduce model aircraft noise However continued research should directed toward studying effect propeller ge ometry overall efficiency should lead optimal blade designs ulti mately minimal propeller noise Finally carefully organized flight test program would provide data base developing standardized propeller selection criterion SAFE FLYING IS NO ACCIDENT Keithsgo latters numbers some known experimental error associated ex act measurement wire length involved physical portion wire near connector itself cases actual length somewhat intended six inches voltage drops would higher expected Whatever wary installation losses plane Use quality wire quality connectorsbut use sparingly Two new speed controls shown photos month First Jomars latesta large control big systems SC 6 mentioned upcoming new product December 1989 column now closer reality control pictured prototype designed operate 22- 34cell systems features new Signetics chip thats designed drive MOSFET metal-oxide semiconductor field-effect rransistorRMcM gates efficiently course its high-frame-rate design optically coupled Tentative list price $130 Joe Utazi tells product line will soon carried distributors across country competitive pricing will drive price other products down Another new control least new writer Horak imported Canada As understand controls handmade Jiri Horak 3403 Fellmore Drive Mississauga Ontar io Canada L5C 2E1 arc scarce supply Jiri makes several versions including ones brakesContinued page 144 March 1990 141 MOIIUUOUP VUA 114 SCALE 96 STITS PLAYBOYWACO UII-7 113 SCALE 88115 SCALE 72 RC Electrics/Kopski Continued page 47
Edition: Model Aviation - 1990/03
Page Numbers: 39, 40, 41, 42, 43, 44, 140, 141
lodel Propeller NOISE three preceding articles discussing findings ex haustive prop noise study conducted North Carolina State University sponsored AMA has demonstrated average commercial propeller inefficient major source model airplane noise engine properly muf fled What can done solve problem discussed concluding segment ER Vess D Heathcoat R Nagel THE PREVIOUS articles four-part series have shown propellers main source model aircraft noise ex plained various sources propeller noise further shown noise due torque loading dominant different sources Last months article con cluded following comments propellers available generally very inefficient inefficiency leads high torque loads relative thrust produced path model aircraft noise reduc tion therefore clear although perhaps easy Making propellers efficient would reduce noise levels compro mising aircraft performance Simply stated means too much work engine spent turning propeller enough used pulling aircraft through air demonstrate fact consider following thought ex periment propeller model aircraft replaced circular rod clear aircraft would able fly motor would work rod would spin great deal noise would generatedbut no thrust would produced round rod terrible propeller noise generated rod propeller would due thick ness cross-sectional diameter torque torque supplied en gine turn quasi propeller order compare noise gen erated particular propeller rod se lected would have size such engine full throttle would turn either rod propeller same rpm means engine would doing same amount work case may surprised learn rod propeller produce similar noise levels similar operating conditions However noise radiating rod has nothing propelling aircraft fore noise due thrust Unfortunately propellers available model ers little too much like rodthey generate large amount torque noise given amount thrust question concerning what can done solve problem depends upon cares responsible Cer tainly people live near flying sites disturbed noise can counted among care local residents often solve problem pro testing such way create new different problem pilotsloss flying site responsibility model aircraft noise does indeed lie fliers manufacturers What can groups combination widespread ed ucation modelers conscientious flying field practices state-of-the-art equip ment will required reach appropri ate workable solution hoped information series articles will pro vide some necessary education Surely manufacturers will continue recognize severity noise issue direct efforts accordingly However its actions individual modelers March 1990 39 Left Argentinean Quique Somenzini displays business end aircraft FAI World Aerobatics Championships Chesapeake VA FutabalYS 12 four-stroke engine turns APC 14 x 14 pro peller muffler Hatori pipe unit added exhaust exten sion Above Somenzinis aircraft held taxiway manda tory static noise readings made measured SPL 855 dBA recorded lowest contest However text re veals limitations applying static readings flight conditions Lower Pitch/Diameter Higher Pitch/Diameter Increoming Airupeed re 1 eller/ Aircraft Matching 120110100-J 0 n C 3 900 C8070 0 Best Fit Line 0 0 08 o -2dBA 0 o0 8090 Predicted SPL dBA will influence continued growth hobby After theyre ones determine what fly isnt difficult understand just sin gle inconsiderate misinformed pilot can create trouble entire club So formation follows will useful accompanied little common sense What t Its model aircraft flying high speeds far runway possibly nearer dis tant houses likely annoy living within proximity flying site typical flight noise runway generally short duration compared time model air noise associated preparation takeoff landing may reaching neighbors Therefore seems obvious strictest noise control efforts should di rected toward high-speed flight condi tion explained first article flying aircraft differs greatly both propel ler performance radiated noise restrained craft ie having no ward motion due differences flow fields around prop case Thus current practice measur ing noise level aircraft being held rest ground fact dealing wrong noise wrong condition wrong place 1989 F3A World Aerobatics Champi onships held Chesapeake VA provided case point FAI competition SPL sound pressure level measured dis tance three meters sideline aircraft must exceed 98 dB quite loud Interestingly enough although aircraft met requirement varying degrees very quiet flighta few point being barely audible fact qualitative stand point planes much quieter air static readings would have suggested can explained examining high-pitch propellers have become pop ular among Pattern fliers prime example particular competition APC 14 x 14 prop Argentinean Quique Somen zinis aircraft measured quietest model meet has proven such propellers perform very well significantly decreasing over noise High-pitch props reach peak efficiency higher flight speeds therefore generate less noise relative other props such speeds However excessive angle tack propeller blades model restrained ground promotes flow separation resulting completely differ ent acoustic signature represent ative case aircraft flight true Somenzinis air craft produced noise level reading 855 dB three meters measured statically must realized low level result flow phenomena dont occur under normal flight conditions fore notably quiet in-flight operation aircraft cannot attributed same factors produced static noise read40 Model Aviation U C U ILl a L a -S 01 S L U 1o1o Figure 2 e Prediction Evaluation PointPropPID 111x764 211x655 311x545 410x770 510x660 610x550 710x550 89x71/283 99x778 109x867 119x556 11 0 N 198dBA 115110m 0 105I oi 100-J estFitLine 0 XMuffler 90-0 Standard 0 High Performance 859095100105110115 Max OASPL Equation 1 dBA Figure 3 e Prediction Evaluation Maximum Airspeed gs What tells us way properly attack model aircraft noise roblem develop some means mea uring sound generated airlane flightwhich its per eived bothersome round course suggesting model aircraft oise should measured flight intro Luces variety logistical problems act just about conceivable method Las practical limitations Fortunately ver possible develop method iredicting model aircraft noise flight rom experimental data acquired under trictly controlled conditions Thus ac ual in-flight measurements could made y qualified individuals proper quipment resulting data could ised create noise prediction method everyday modeler fact same lata could also used predict aircraft erformance would possible Jevelop propeller selection method Nould address both performance noise onsiderations Until recently modelers simply icked two three props listed y engine manufacturer satisfactory engine particular displacement rhis poor way choose propeller rhe proper choice can made neeting specific requirements par icular aircraft/engine combination de ired flight condition good way illus rate point comparing typical rainer powered 40-cu-in engine iigher performance sport aircraft utilizing same engine trainer designed fly low air peeds easily managed begin iers proper propeller case should efficient quiet slow tpeeds depicted Figure 1 Such prop would generally characterized having moderate blade pitch sufficient diame er absorb power generated en gine specified limit airspeed comparison high-performance sport aircraft designed fly much faster Pro pellers best suited such craft ones should reach peak efficiency higher airspeeds indicated sec ond curve figure might achieved increasing pitch-to-diam eter ratio important note since dealing fixed-pitch propellers range high efficiency limited fore propeller selected should peak efficiency occurs likely airspeed particular plane Some compromise performance pos sibly noise will evident other air speeds flight envelope extent performance degradation off de sign conditions has significant effect suitability particular prop given aircraft As preceding example has shown pro peller selection driven aerody namic characteristics aircraft ever great diversity types models flown considerably complicates pro cedure developing single propeller se lection method would applicable model airplanes Dividing model aircraft groups similar aerody namic characteristics would reduce num ber variables Data obtained flight tests aircraft typical certain group could used derive performance acoustic prediction methods would applicable other aircraft group An appropriate prop selection criter ion would based prediction infor mation Consider preliminary example following broad categorization trainers sport aircraft high-performance air craft Since divisions based12 typical maxi mum flight speeds some overlapping11 among categories would expected10 Miss Martha aircraft whtch utilized collect9 flight test data dur- ing course of8 research servesas example advanced sport7 aircraft Thus prediction method6 resulting manipulation research data might5 expected ap ply similar sport aircraft6 Data limitations performance data acquired dur ing tests included airspeed propeller rotational speed down-linked telemetry system acoustic data corres ponding performance readings con sisted OASPL overall sound pressure level values recorded air craft passed over microphone visually interpreted separation distance approxi mately two meters should noted data acquired under less ideal circumstances therefore subject error due following difficulties 1 proper engine needle valve set ting difficult maintain throughout entire series runs resulting inconsist encies available power contribute sim ilar inconsistencies both performance March 1990 41 200PoIntPropP/fl 111x764 211x655 311x545 410x770 c 190510x660 a6lOxS506 E7lOxS50 69x753 99x778 l80109x667 119x55685kmph 0 170Best Fit Line 6 S uffler 2 x 150 0 2 0 140 140150160170180190200 Max flight Speed Equation 2 krtiph Figure 4 ormance Prediction Evaluation Full Throttle o Standard High Performance Noise Constraint C 0 C 0 C 0 C Practical Use Range 0 Airspeed Constraint 9 101112 Diameter inches Figure 5 eller Selection Map acoustic data 2 The simplicity airborne teleme try system limited achievable accuracy performance data recorded ground 3 Varying wind conditions drasti cally different aircraft test speeds contrib uted difficulties consistently flying di rectly over sound-level meter 4 The flyover distances simply judged visual comparison nearby ref erence point therefore subject hu man error should noted however data recorded after re peated within acceptable limits three good passes over microphone list error sources introduced discredit data realistically qual ify extent its accuracy famil iarize reader problem areas need addressed prior performing extensive flight tests Any conclu sions drawn carefully scrutinized potential error mind adjusted accordingly conclu sions derived lab experiments favorably supported flight test data Noise prediction Correlation acous tic data flight tests desired geometric parameters measured propellers data base provided foundation development noise prediction method involved rather tedious task mathematically weighing within single equation contribution individual parameter made overall noise level determining well resulting equation predicted ex perimental values repeating entire process until error minimized result effort following equation actually less threatening appears OASPLpred 110 log D15 log P 40 log NllO log [175 logl JIit]f 10 log 1 8Mt4I [32 log {D-93±15}1151 6429 variables expression describe propeller terms particu lar interest investigation de fined follows D diameter inches P h inches N tional speed rpm o dity outer half prop J nce ratio prop tip Mach number plotting predicted noise against measured noise Figure 2 quality prediction equation can visualized perfect prediction equation would repro duce experimental data exactly means point would collapse onto line unit slope two plotted example slope best fit line through data has value 097 indicates prediction repre sents available data quite well data scatter primarily due exper imental measurement error has calcu lated mean value approximately 2 dBA compares favorably noise prediction equations developed aero space industry Remember though usefulness prediction method deter mined both quality data quality equation equation have given however can predict propeller noise listed variables known Obviously severely limits practical use equation since few modelers have means measuring airspeed engine rpm flight Flying clubs need something simpler work witha method uses easily measured parameters development another equation applies maximum flight speed speed interest way allows significant simplification resulting equation 1 indeed practical since based entirely propeller geome try ruler pocket calculator tools required 1 Max OASPL og [D48 x P/Di x C7SR/R66 x CSOR/C7SRS6S x 625] 4 input variables equation D eller diameter measured inches P/D h-to-diameter ratio CxR eller blade chord measured inches stated location exam ple C5R chord length halfradius position midspan blade R Propeller radius half diameter measured inches Power parameter 10 for standard stock mufflers 105 high-performance mufflers last parameter H serves adjust performance aircraft ex haust system has found socalled high-performance mufflers available modeler today tend increase maximum flight speed general re sult noise speed However model equipped highperformance muffler tested same flight speeds attainable ad vanced muffler noise level remains roughly unchanged comparison results predic tion equation measured results ob 42 Model Aviation Left Several new APC propellers displayed front Miss Martha test aircraft exampies depicted nave diameters rangin nine 11 inches pitches six seven eight 10 inches 9 x 10 propeller mounted 0S Max 46SF engine providec startling flight speeds extremely low noise levels Right John Herbert Raleigh Aeromasters RC Club returns pits after flight An APC 9 x 6 propeller used Goldberg Eaglet powered OS Max 25 engine Although resulting increase max imum flight speed suits style flying proper propeller class aircraft would probably have lower pitch/diameter ratio tc shift peak prop efficiency lower airspeed APC propellers Landing Products distributed through Horizon Distributors SAFE FLYING IS NO ACCIDENT THE BEST FUSELAGE JIG EVER PERIOD Provides Solid Support Accurate Building Rugged Construction 7 Ply Aircraft Plywood Provides Lifetime Use Two Sizes Available Regular Fuselages Up 6 Wide Jumbo Fuselages Up 9 Wide Use Own Building Buard Work Bench Base Mount Jig Station Uni-Strut Guide Rails Most Versatile Set-Up Contains Complete Hardware Instructions Including Uni-Strut Information Buxof4StandardJigStatioflsS1795 Boxof4JumboJigStations1995 Two 5 ft long Guide Rails including mounting nuts 2195 ained Miss Martha aircraft full hrottle given Figure 3 noise pro luced different propellers figire ranges about 87 dBA over 110 dBA Propeller selection made differ ence between quiet aircraft ex tremely noisy However because aforementioned measurement error dif ficult obtain definite conclusions di rectly figure Nevertheless general trends support claim props higher pitch-todiameter ratios produce less noise flight Furthermore examples high-performance muffler used indi cate increased noise levels because engine performing better significance comparison shown Figure 3 demonstrates first possi ble obtain prediction equation ex perimental data second accu racy data controls usefulness such equation Performance prediction As discussed pre viously goal exercise pro duce example propeller selection method addresses both noise per formance performance data acquired flight tests manipulated same manner derive equation would predict maximum flight speed model within same general category sport aircraft ie aerodynamic characteristics similar Miss Martha IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure aileron elevator rudder throw Takes guess work out trimming out airplane quality tool conspiete instructions log book carrying case5795 U PLUG-IN ADJUSTABLE STAB KIT last tan optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matthing phenolic socket 5695 Include 52 SOlItem UPS esidents Add 6% Sales Tax GATOR RIC PRODUCTS 3713 Pompano Dr acola FL 32514 476-8639 test aircraft Equation 2 result such effort Note variables same defined Equation 1 2 Vmax predicted x [DO x PID015 x C7SRIR9 x CSoRIC7SR65 X C9oR/C7SR055 x PH4] Figure 4 presents graphic comparison measured predicted flight velocity error approximately 5% mean flight velocity translates about 85 kmph Comparison figure Fig ure 3 reveals general trend props higher pitch-to-diameter ra tios data base produced highest maximum flight speed lowest noise Once again consistent labo ratory results Propeller selection method further uti lizing prediction equations 1 2 practical method selecting propeller satisfies reasonable noise per formance constraints can developed aircraft categoryie sport air craft. Consider task selecting pro peller meets following criteria Aircraft Miss Martha Advanced level sport Engine 05 Max 46 SF Muffler PLUG-IN WING ADJUSTER KIT Four glass filled nylon brackets included key wing panels front rear allow accurately adjust panel straight flight Complete hardware & InstructIons 5995 WING TUBE & SOCKETS Aluminum alloy tubing plug-in wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2S 895 1diax2S 995 1dias351495 Davis Diesel Soundmaster high perform ance Desired maximum flight speed 175 kmph 109 mph Flying site noise regulation 880 dBA @ two meters flyover ap prox 853 dBA @ three meters Reference should made equations 1 2 Since high-performance muf fler used H Furthermore mea surements taken propellers data base produce following average blade chord distribution C7SR/R C5oR/C75R C9oRIC75R0725 will assumed propeller ques tion has expected blade chord distribu tion substituting known values equations following mathemati cal inequalities may written terms blade pitch diameter both inches 1 P155 x l05 x Noise Constraint 2aP 1 295 X Speed Constraint Plotting both same figure Figure 5 produces finite boundary above pitch/diameter combinations sat isfy constraints can found Examina RDABLE AL POWER INTRODUCTORY 849 SPECIAL SEND 5100 TECHNICAL DATA THE MIKE GR6- 120 2-CYCLE POWERPLANT 6 CYLINDER RADIAL ANTY LBSOFTHRuST * 25 SHP IDYNO TESTEDI * NO VIBRATION III * SINGLE NEEDLE VALVE * 8 STAINLESS BALL BROS * IDLES AT 1800 RPM * OIL LUBRICATED GEARS * 3/8 HARDENED SE SHAFT * FULLY FLIGHT TESTED * DIAMETER 8 TO PLUG TIPS * WEIGHT 4 LEE INCLuDING INTEGRAL MOUNT AND MUFFLER * SWINGS 18/8 PROF /8 8880 RPM * EXCEEDS QuADRA 35 IN POWER AND ZENOAH G38 IN THRUST * GLOW FUEL USED-1S% * GLOW PLUG LEADS INCLUDED * READY TO FLY NOT KITI 33 DEALER INQUIRIESs-% INVITEDp TECHNOLOGIES INC 7 Greenwood Lane VaiSsIla New YorE lOSES 1914 888-9373 FAT PENDING TEST FLOWN IN 72 GM PLASTICS F4U CORSAIR 72 BOB DIVELYS SU-2 BIPLANE 88 PROCTOR NIEUPORT 28 BIPLANE 58 MONOCOUPE EISA March 1990 43 $1695 LIST THE PIPER BRAVE 1/4 scale model Pipers latest Ag plane t wing span 30-33 lbs 5 cc power lb payload ational flaps hopper door onal Spreader Kit formed aluminum landing gear rglass cowls um-formed canopy tucted extruded foam ply hardwood r -Model actually dustingBRKE $269~ OPTIONAL995 SPREADER SEND siee FOR CATALOG OFC/IRT 1 NEODESHA KS 66757 SAC KITS AND ACCESSORIES316 325-2821 Free Shipping Kit OrdersScott Airplane CompanyVISA MASTERCARD tion figure leads obvious con- distribution assumed could have ious props yielded some important observa clusion propellers re- resulted slight shift noise boun- tions Since explained previously thc gion bounded curves either dont dary necessary exclude 9 x 75 prop goal match peak propeller effi exist simply aren t practical use important thing recognize ciency airspeed model i specified engine desirable propeller pitch/diameter ratio often flown performance othex ranges pitch diameter occur near least 083 would required meet se- speeds does suffer consequence Examrange represented data base propel- lection criteria pitch/diameter ratio pIes noticeable performance degradation lers both because prediction increased further might possible op- off design conditions follow equations derived data acquired erate required airspeed less first thing modelers will notice thil such propellers because props out- noise the static rpm will much lower highside range tend subject prob- recent introduction new line pitch props However expected lems area practicality props allows further investigation result flow separation blades Functional propellers must able ab- hypothesis Known APC Advanced Pre- aircraft i5 restrained theres no sorb power available engine cision Composite props line manu- reason discouraged fact follow reasonable rpm must also perform ad- factured California Landing Products rule thumb prop screaminl equately off design situations distributed hobby dealers through ground engine sufficientl rules out propellers too little diameter Horizon Distributors Several examples loadedwhich means flight perform too much pitch example ad- props flown Miss Martha ance will compromised noise ditional boundary sets lower diam- test aircraft evaluated qualitatively creased course direct opposi eter limit 9 might appropriately instrumentation several tion way modelers choose prop inserted Figure 5 Doing con- produced excellent results 9 present fines realistic choices narrow x 10 P/D 111 A second observation takeofi shaded region figure The APC 9 x 10 propeller produced level acceleration will reduced increas time flight testing per- flight speeds never previously attained es takeoff length small amount Du formed highest pitch/diameter ratio other prop aircraft as- excessive thrust-to-weight ratio 01 prop available use type engine tounding observation however model airplanes however 9 x 75 P/DO83 Notice quietness APC prop propeller major problem Figure 5 prop should theoretically quiet airflow around Finally thrust low flight speeds i satisfy constraints example How- plane audible no data has reduced resulting degraded maneuvet ever inspection data propel- acquired props quite obvi- performance Note aircraft fly ler Figure 3 reveals noise con- ous exhibit increased levels effi- ing fast climb rate excellent its straint would met Remember ciency due increased performance model slows down powet though boundaries Figure 5 decreased noise levels is increased nose raised ef derived imperfect experi- Qualitative comparisons takeoff fect becomes apparent mental data average blade chord lengths climb performance var- Continued page 140 PRACTICAL SIZED GIANT SCALE MODEL PLANS Fiberg/ass Cowlings Canopies Available N1 311/2 1140Span54200 F4u CORSAiR2 1/4 193Span$3000 ASMS ZERO2 1/2 Span $3000Plans RK-20 cuRTiS P40 2 1/2 Span $3000 RK-740 Oucted Fans AT-6 TEXAN 24 1 Span $3000 Phaniom 35 Span $1000 FSF BEARCAT 2 1/2 Span $3000 FQKKER OR127163 Viggen32 Span SiO00 Tripe $2700p36 Span $1000 Pian nd canopy$1500 Order FromCredited First Order $25 Nick Ziroli29 Edgar Dr Smithtown NY 11787 USA516-234-5038 44 Model Aviation Mere Fun SPECIFICATIONS Wing Span62'2 inches Wing Area770 square inches Engine Size 10 cc 90 129 four stroke Designed AMA FAI Turn-around pattern Foam wing stab 3-32 Balsa sheet covering Tricycle conven tional gear fixed retracts Rear side exhaust fiber glass canopy Very positive maneuverable XLT SPECIFIC Wing Span65 inches Length65 inches Wing Area845 square inches Recommended Engine Size 10 cc 90 120 four stroke XLT designed tuned pipe re tract landing gears Capable AMA Turn-around pattern Rear side ex haust SPECIFICATIONS Wing Span Wing Area Engine Size 63'4 inches 700 square inches 50-60 Glow 90 four stroke fun sport pattern turn-around can done Utter Chaos completely built up Balsa construction Canopy engine mount included years proven flying reliablity BRIDI AIRCRAFT DESIGNS INC 23625 Pineforest Lane Harbor City California 90710 213 549-8264 326-5013 SEE YOUR FAVORITE HOBBY SHOP OR RETAIL OUTLET Dealer Inquries Invited PRODUCTS Complete Line Exheust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers Expansion Mufflers copter Ball Mufflers ialized Exhaust Systems Unsurpassed Workmaashin & Padormance Inc Chicago IL 60651 Stay-Brite silver solder Stay Clean flux 1W Harris Co 10930 Deerfield Rd Cincinnati OH 45242 Tools SR batteries tool kit contains SAE metric hex wrenches well crosspoint regular screwdriver bits nifty box ratchet drive screwdriver-type handle very handy use love bits fit electric screwdriver should grab interest somewhat greater interest fact can buy single replacement bits should damaged lost Think sel dom can thing like days SR Batteries Inc Box 287 Bellport NY 11713 tel 1-516/286-0079 Wen portable tool kit #2336 has de scribed previous column contains drill motor Dremel-type grinder saber saw sol dering iron plug cigarette lighter 12-VDC receptacle car have kit find uses dont have people snicker idea toy tools look like toys worked like 110VAC tools no trouble cutting A-in ply wood drilling 4-in holes Ford van body parts Portasol butane-fueled soldering iron also described earlier Suffice say worked fine Camera bought Minolta Weather matic Dual 35 main thought might travel salt air splashes possibility being dropped overboard rule Out use expensive cameras lenses camera 0-ring-sealed against dust moisture has corrosion-resistant yellow plastic exterior will float water accepts DXcoded ASA 100 1000 35mm color print film has pushbutton-selected internal 35mm 50mm lenses features automatic film advance/rewind well autofocus nearest focus point two feet 50mm lens focus-hold feature built shutter button just big cameras tiny built-in flash much better no flash 26 x 31 x 58 less pound camera relatively small light nice hiking must carry everything body much dust Alaska stayed outside camera bought camera its weather resistance learned enjoy fact can worked hand ap preciate its durability favorite lens 35mm-to-tOSmm macro zoom can understand felt limited BATT- CHEKEX Saves Time . Saves Models Install RO Models 3-Level indication receiver battery status press button Precise Rugged Small Light /2 oz Made SA Also custom units other applications Order Today si 495 trom dealer send check money order topostpaid Protune Corp 914 462-6452 PO Box 1808 Poughkeepal NY 12601 NY State residents add sales tax non-macro 35/50mm lens selection use found could get about 85% pic tures wanted Thats pretty good compro mise Any camera just tool good general-purpose tool think would look good field kit perhaps could send some pictures column Minolta Weathermatic Dual 35 local camera store Light 12-VDC fluorescent light plugs automobile cigar lighter very handy put couple strips VelcroTM hooks back permit stick light prati cally anywhere cloth interior van sticks very neatly head-liner seat backs comes off easily need another po sition unit draws 06 amps opposed vans interior lights draw 24 amps provides plenty light reading working whatever have separate deep-cycle RV recreational vehicleEd battery van operate re frigerator lights whatever other items might need total capacity RV battery 70 amp-hours refrigerator alone can exhaust about 17 hours Ito fall asleep refrigerator interior lights battery would exhausted 11 hours Sub stituting fluorescent light vans stan dard interior lights will let battery last 15 hours think extra four hours operating time very valuable RV battery course independent battery starts van wont give manufacturer light because have seen similar units K-Mart Radio Shack etc Prop Noise Continued page 44 last factor controlled fi nal choice prop test aircraft An APC 10 x 8 determined best compromise fact maximum flight speed noise level appear similar 9 x 10 prop low-speed thrust greatly improved As airplane/prop combination demon strates now possible operate model aircraft reduced noise levels little no compromise performance hoped propeller manufacturers will follow APC lead developing introducing new lines will benefit aircraft sizes would major step toward preserving community relations ensur ing continued growth hobby 140 Model Aviation Radio Technique/Myers Continued page 107 Celebrating 10 years producing largest selection giant scale kits available today Design building integrity scale fidelity scale flight characteristics standard IKON NWST 22 kits choose Conclusions research program sponsored AMA order gain better understanding propeller noise major objectives determine con tribution propeller makes over aircraft noise isolate main source prop noise latter proved significant establish guidelines would ulti mately lead quieter model aircraft opera tion combination propeller theory experimental data wind tun nel flight tests provided some definitive conclusions 1 In order reduce noise generated model aircraft dominant source must reduced Provided reasonable muffler used propeller domi nant noise source 2 The dominant source propeller noise torque noise Since efficient propellers generate thrust given amount required torque use will re sult less noise given airspeed 3 Propellers currently available mod elers general quite inefficient use such propellers leads less ideal performance acoustic characteris tics 4 Modelers should select propeller peak efficiency occurs near range airspeeds aircraft will usually operated general props increased pitch/diameter ratios must made available allow such integration wide variety aircraft 5 Noise reduction efforts should directed maximum flight speed condi tion way truly quantify noise attempt reduce mea sure flight 6 It possible develop propeller se lection method based in-flight experimental data addresses both noise performance would give aver age modeler means selecting prop would meet noise regulations performing satisfaction 7 This information will useful applied universally will job ganized groups such AMA clubs hobby dealers manufacturers edu cate individuals enforce proper pro cedures research study described series articles has disclosed nature prob lem propeller noise introduced some solutions Using efficient propellers will reduce model aircraft noise However continued research should directed toward studying effect propeller ge ometry overall efficiency should lead optimal blade designs ulti mately minimal propeller noise Finally carefully organized flight test program would provide data base developing standardized propeller selection criterion SAFE FLYING IS NO ACCIDENT Keithsgo latters numbers some known experimental error associated ex act measurement wire length involved physical portion wire near connector itself cases actual length somewhat intended six inches voltage drops would higher expected Whatever wary installation losses plane Use quality wire quality connectorsbut use sparingly Two new speed controls shown photos month First Jomars latesta large control big systems SC 6 mentioned upcoming new product December 1989 column now closer reality control pictured prototype designed operate 22- 34cell systems features new Signetics chip thats designed drive MOSFET metal-oxide semiconductor field-effect rransistorRMcM gates efficiently course its high-frame-rate design optically coupled Tentative list price $130 Joe Utazi tells product line will soon carried distributors across country competitive pricing will drive price other products down Another new control least new writer Horak imported Canada As understand controls handmade Jiri Horak 3403 Fellmore Drive Mississauga Ontar io Canada L5C 2E1 arc scarce supply Jiri makes several versions including ones brakesContinued page 144 March 1990 141 MOIIUUOUP VUA 114 SCALE 96 STITS PLAYBOYWACO UII-7 113 SCALE 88115 SCALE 72 RC Electrics/Kopski Continued page 47
Edition: Model Aviation - 1990/03
Page Numbers: 39, 40, 41, 42, 43, 44, 140, 141
lodel Propeller NOISE three preceding articles discussing findings ex haustive prop noise study conducted North Carolina State University sponsored AMA has demonstrated average commercial propeller inefficient major source model airplane noise engine properly muf fled What can done solve problem discussed concluding segment ER Vess D Heathcoat R Nagel THE PREVIOUS articles four-part series have shown propellers main source model aircraft noise ex plained various sources propeller noise further shown noise due torque loading dominant different sources Last months article con cluded following comments propellers available generally very inefficient inefficiency leads high torque loads relative thrust produced path model aircraft noise reduc tion therefore clear although perhaps easy Making propellers efficient would reduce noise levels compro mising aircraft performance Simply stated means too much work engine spent turning propeller enough used pulling aircraft through air demonstrate fact consider following thought ex periment propeller model aircraft replaced circular rod clear aircraft would able fly motor would work rod would spin great deal noise would generatedbut no thrust would produced round rod terrible propeller noise generated rod propeller would due thick ness cross-sectional diameter torque torque supplied en gine turn quasi propeller order compare noise gen erated particular propeller rod se lected would have size such engine full throttle would turn either rod propeller same rpm means engine would doing same amount work case may surprised learn rod propeller produce similar noise levels similar operating conditions However noise radiating rod has nothing propelling aircraft fore noise due thrust Unfortunately propellers available model ers little too much like rodthey generate large amount torque noise given amount thrust question concerning what can done solve problem depends upon cares responsible Cer tainly people live near flying sites disturbed noise can counted among care local residents often solve problem pro testing such way create new different problem pilotsloss flying site responsibility model aircraft noise does indeed lie fliers manufacturers What can groups combination widespread ed ucation modelers conscientious flying field practices state-of-the-art equip ment will required reach appropri ate workable solution hoped information series articles will pro vide some necessary education Surely manufacturers will continue recognize severity noise issue direct efforts accordingly However its actions individual modelers March 1990 39 Left Argentinean Quique Somenzini displays business end aircraft FAI World Aerobatics Championships Chesapeake VA FutabalYS 12 four-stroke engine turns APC 14 x 14 pro peller muffler Hatori pipe unit added exhaust exten sion Above Somenzinis aircraft held taxiway manda tory static noise readings made measured SPL 855 dBA recorded lowest contest However text re veals limitations applying static readings flight conditions Lower Pitch/Diameter Higher Pitch/Diameter Increoming Airupeed re 1 eller/ Aircraft Matching 120110100-J 0 n C 3 900 C8070 0 Best Fit Line 0 0 08 o -2dBA 0 o0 8090 Predicted SPL dBA will influence continued growth hobby After theyre ones determine what fly isnt difficult understand just sin gle inconsiderate misinformed pilot can create trouble entire club So formation follows will useful accompanied little common sense What t Its model aircraft flying high speeds far runway possibly nearer dis tant houses likely annoy living within proximity flying site typical flight noise runway generally short duration compared time model air noise associated preparation takeoff landing may reaching neighbors Therefore seems obvious strictest noise control efforts should di rected toward high-speed flight condi tion explained first article flying aircraft differs greatly both propel ler performance radiated noise restrained craft ie having no ward motion due differences flow fields around prop case Thus current practice measur ing noise level aircraft being held rest ground fact dealing wrong noise wrong condition wrong place 1989 F3A World Aerobatics Champi onships held Chesapeake VA provided case point FAI competition SPL sound pressure level measured dis tance three meters sideline aircraft must exceed 98 dB quite loud Interestingly enough although aircraft met requirement varying degrees very quiet flighta few point being barely audible fact qualitative stand point planes much quieter air static readings would have suggested can explained examining high-pitch propellers have become pop ular among Pattern fliers prime example particular competition APC 14 x 14 prop Argentinean Quique Somen zinis aircraft measured quietest model meet has proven such propellers perform very well significantly decreasing over noise High-pitch props reach peak efficiency higher flight speeds therefore generate less noise relative other props such speeds However excessive angle tack propeller blades model restrained ground promotes flow separation resulting completely differ ent acoustic signature represent ative case aircraft flight true Somenzinis air craft produced noise level reading 855 dB three meters measured statically must realized low level result flow phenomena dont occur under normal flight conditions fore notably quiet in-flight operation aircraft cannot attributed same factors produced static noise read40 Model Aviation U C U ILl a L a -S 01 S L U 1o1o Figure 2 e Prediction Evaluation PointPropPID 111x764 211x655 311x545 410x770 510x660 610x550 710x550 89x71/283 99x778 109x867 119x556 11 0 N 198dBA 115110m 0 105I oi 100-J estFitLine 0 XMuffler 90-0 Standard 0 High Performance 859095100105110115 Max OASPL Equation 1 dBA Figure 3 e Prediction Evaluation Maximum Airspeed gs What tells us way properly attack model aircraft noise roblem develop some means mea uring sound generated airlane flightwhich its per eived bothersome round course suggesting model aircraft oise should measured flight intro Luces variety logistical problems act just about conceivable method Las practical limitations Fortunately ver possible develop method iredicting model aircraft noise flight rom experimental data acquired under trictly controlled conditions Thus ac ual in-flight measurements could made y qualified individuals proper quipment resulting data could ised create noise prediction method everyday modeler fact same lata could also used predict aircraft erformance would possible Jevelop propeller selection method Nould address both performance noise onsiderations Until recently modelers simply icked two three props listed y engine manufacturer satisfactory engine particular displacement rhis poor way choose propeller rhe proper choice can made neeting specific requirements par icular aircraft/engine combination de ired flight condition good way illus rate point comparing typical rainer powered 40-cu-in engine iigher performance sport aircraft utilizing same engine trainer designed fly low air peeds easily managed begin iers proper propeller case should efficient quiet slow tpeeds depicted Figure 1 Such prop would generally characterized having moderate blade pitch sufficient diame er absorb power generated en gine specified limit airspeed comparison high-performance sport aircraft designed fly much faster Pro pellers best suited such craft ones should reach peak efficiency higher airspeeds indicated sec ond curve figure might achieved increasing pitch-to-diam eter ratio important note since dealing fixed-pitch propellers range high efficiency limited fore propeller selected should peak efficiency occurs likely airspeed particular plane Some compromise performance pos sibly noise will evident other air speeds flight envelope extent performance degradation off de sign conditions has significant effect suitability particular prop given aircraft As preceding example has shown pro peller selection driven aerody namic characteristics aircraft ever great diversity types models flown considerably complicates pro cedure developing single propeller se lection method would applicable model airplanes Dividing model aircraft groups similar aerody namic characteristics would reduce num ber variables Data obtained flight tests aircraft typical certain group could used derive performance acoustic prediction methods would applicable other aircraft group An appropriate prop selection criter ion would based prediction infor mation Consider preliminary example following broad categorization trainers sport aircraft high-performance air craft Since divisions based12 typical maxi mum flight speeds some overlapping11 among categories would expected10 Miss Martha aircraft whtch utilized collect9 flight test data dur- ing course of8 research servesas example advanced sport7 aircraft Thus prediction method6 resulting manipulation research data might5 expected ap ply similar sport aircraft6 Data limitations performance data acquired dur ing tests included airspeed propeller rotational speed down-linked telemetry system acoustic data corres ponding performance readings con sisted OASPL overall sound pressure level values recorded air craft passed over microphone visually interpreted separation distance approxi mately two meters should noted data acquired under less ideal circumstances therefore subject error due following difficulties 1 proper engine needle valve set ting difficult maintain throughout entire series runs resulting inconsist encies available power contribute sim ilar inconsistencies both performance March 1990 41 200PoIntPropP/fl 111x764 211x655 311x545 410x770 c 190510x660 a6lOxS506 E7lOxS50 69x753 99x778 l80109x667 119x55685kmph 0 170Best Fit Line 6 S uffler 2 x 150 0 2 0 140 140150160170180190200 Max flight Speed Equation 2 krtiph Figure 4 ormance Prediction Evaluation Full Throttle o Standard High Performance Noise Constraint C 0 C 0 C 0 C Practical Use Range 0 Airspeed Constraint 9 101112 Diameter inches Figure 5 eller Selection Map acoustic data 2 The simplicity airborne teleme try system limited achievable accuracy performance data recorded ground 3 Varying wind conditions drasti cally different aircraft test speeds contrib uted difficulties consistently flying di rectly over sound-level meter 4 The flyover distances simply judged visual comparison nearby ref erence point therefore subject hu man error should noted however data recorded after re peated within acceptable limits three good passes over microphone list error sources introduced discredit data realistically qual ify extent its accuracy famil iarize reader problem areas need addressed prior performing extensive flight tests Any conclu sions drawn carefully scrutinized potential error mind adjusted accordingly conclu sions derived lab experiments favorably supported flight test data Noise prediction Correlation acous tic data flight tests desired geometric parameters measured propellers data base provided foundation development noise prediction method involved rather tedious task mathematically weighing within single equation contribution individual parameter made overall noise level determining well resulting equation predicted ex perimental values repeating entire process until error minimized result effort following equation actually less threatening appears OASPLpred 110 log D15 log P 40 log NllO log [175 logl JIit]f 10 log 1 8Mt4I [32 log {D-93±15}1151 6429 variables expression describe propeller terms particu lar interest investigation de fined follows D diameter inches P h inches N tional speed rpm o dity outer half prop J nce ratio prop tip Mach number plotting predicted noise against measured noise Figure 2 quality prediction equation can visualized perfect prediction equation would repro duce experimental data exactly means point would collapse onto line unit slope two plotted example slope best fit line through data has value 097 indicates prediction repre sents available data quite well data scatter primarily due exper imental measurement error has calcu lated mean value approximately 2 dBA compares favorably noise prediction equations developed aero space industry Remember though usefulness prediction method deter mined both quality data quality equation equation have given however can predict propeller noise listed variables known Obviously severely limits practical use equation since few modelers have means measuring airspeed engine rpm flight Flying clubs need something simpler work witha method uses easily measured parameters development another equation applies maximum flight speed speed interest way allows significant simplification resulting equation 1 indeed practical since based entirely propeller geome try ruler pocket calculator tools required 1 Max OASPL og [D48 x P/Di x C7SR/R66 x CSOR/C7SRS6S x 625] 4 input variables equation D eller diameter measured inches P/D h-to-diameter ratio CxR eller blade chord measured inches stated location exam ple C5R chord length halfradius position midspan blade R Propeller radius half diameter measured inches Power parameter 10 for standard stock mufflers 105 high-performance mufflers last parameter H serves adjust performance aircraft ex haust system has found socalled high-performance mufflers available modeler today tend increase maximum flight speed general re sult noise speed However model equipped highperformance muffler tested same flight speeds attainable ad vanced muffler noise level remains roughly unchanged comparison results predic tion equation measured results ob 42 Model Aviation Left Several new APC propellers displayed front Miss Martha test aircraft exampies depicted nave diameters rangin nine 11 inches pitches six seven eight 10 inches 9 x 10 propeller mounted 0S Max 46SF engine providec startling flight speeds extremely low noise levels Right John Herbert Raleigh Aeromasters RC Club returns pits after flight An APC 9 x 6 propeller used Goldberg Eaglet powered OS Max 25 engine Although resulting increase max imum flight speed suits style flying proper propeller class aircraft would probably have lower pitch/diameter ratio tc shift peak prop efficiency lower airspeed APC propellers Landing Products distributed through Horizon Distributors SAFE FLYING IS NO ACCIDENT THE BEST FUSELAGE JIG EVER PERIOD Provides Solid Support Accurate Building Rugged Construction 7 Ply Aircraft Plywood Provides Lifetime Use Two Sizes Available Regular Fuselages Up 6 Wide Jumbo Fuselages Up 9 Wide Use Own Building Buard Work Bench Base Mount Jig Station Uni-Strut Guide Rails Most Versatile Set-Up Contains Complete Hardware Instructions Including Uni-Strut Information Buxof4StandardJigStatioflsS1795 Boxof4JumboJigStations1995 Two 5 ft long Guide Rails including mounting nuts 2195 ained Miss Martha aircraft full hrottle given Figure 3 noise pro luced different propellers figire ranges about 87 dBA over 110 dBA Propeller selection made differ ence between quiet aircraft ex tremely noisy However because aforementioned measurement error dif ficult obtain definite conclusions di rectly figure Nevertheless general trends support claim props higher pitch-todiameter ratios produce less noise flight Furthermore examples high-performance muffler used indi cate increased noise levels because engine performing better significance comparison shown Figure 3 demonstrates first possi ble obtain prediction equation ex perimental data second accu racy data controls usefulness such equation Performance prediction As discussed pre viously goal exercise pro duce example propeller selection method addresses both noise per formance performance data acquired flight tests manipulated same manner derive equation would predict maximum flight speed model within same general category sport aircraft ie aerodynamic characteristics similar Miss Martha IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure aileron elevator rudder throw Takes guess work out trimming out airplane quality tool conspiete instructions log book carrying case5795 U PLUG-IN ADJUSTABLE STAB KIT last tan optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matthing phenolic socket 5695 Include 52 SOlItem UPS esidents Add 6% Sales Tax GATOR RIC PRODUCTS 3713 Pompano Dr acola FL 32514 476-8639 test aircraft Equation 2 result such effort Note variables same defined Equation 1 2 Vmax predicted x [DO x PID015 x C7SRIR9 x CSoRIC7SR65 X C9oR/C7SR055 x PH4] Figure 4 presents graphic comparison measured predicted flight velocity error approximately 5% mean flight velocity translates about 85 kmph Comparison figure Fig ure 3 reveals general trend props higher pitch-to-diameter ra tios data base produced highest maximum flight speed lowest noise Once again consistent labo ratory results Propeller selection method further uti lizing prediction equations 1 2 practical method selecting propeller satisfies reasonable noise per formance constraints can developed aircraft categoryie sport air craft. Consider task selecting pro peller meets following criteria Aircraft Miss Martha Advanced level sport Engine 05 Max 46 SF Muffler PLUG-IN WING ADJUSTER KIT Four glass filled nylon brackets included key wing panels front rear allow accurately adjust panel straight flight Complete hardware & InstructIons 5995 WING TUBE & SOCKETS Aluminum alloy tubing plug-in wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2S 895 1diax2S 995 1dias351495 Davis Diesel Soundmaster high perform ance Desired maximum flight speed 175 kmph 109 mph Flying site noise regulation 880 dBA @ two meters flyover ap prox 853 dBA @ three meters Reference should made equations 1 2 Since high-performance muf fler used H Furthermore mea surements taken propellers data base produce following average blade chord distribution C7SR/R C5oR/C75R C9oRIC75R0725 will assumed propeller ques tion has expected blade chord distribu tion substituting known values equations following mathemati cal inequalities may written terms blade pitch diameter both inches 1 P155 x l05 x Noise Constraint 2aP 1 295 X Speed Constraint Plotting both same figure Figure 5 produces finite boundary above pitch/diameter combinations sat isfy constraints can found Examina RDABLE AL POWER INTRODUCTORY 849 SPECIAL SEND 5100 TECHNICAL DATA THE MIKE GR6- 120 2-CYCLE POWERPLANT 6 CYLINDER RADIAL ANTY LBSOFTHRuST * 25 SHP IDYNO TESTEDI * NO VIBRATION III * SINGLE NEEDLE VALVE * 8 STAINLESS BALL BROS * IDLES AT 1800 RPM * OIL LUBRICATED GEARS * 3/8 HARDENED SE SHAFT * FULLY FLIGHT TESTED * DIAMETER 8 TO PLUG TIPS * WEIGHT 4 LEE INCLuDING INTEGRAL MOUNT AND MUFFLER * SWINGS 18/8 PROF /8 8880 RPM * EXCEEDS QuADRA 35 IN POWER AND ZENOAH G38 IN THRUST * GLOW FUEL USED-1S% * GLOW PLUG LEADS INCLUDED * READY TO FLY NOT KITI 33 DEALER INQUIRIESs-% INVITEDp TECHNOLOGIES INC 7 Greenwood Lane VaiSsIla New YorE lOSES 1914 888-9373 FAT PENDING TEST FLOWN IN 72 GM PLASTICS F4U CORSAIR 72 BOB DIVELYS SU-2 BIPLANE 88 PROCTOR NIEUPORT 28 BIPLANE 58 MONOCOUPE EISA March 1990 43 $1695 LIST THE PIPER BRAVE 1/4 scale model Pipers latest Ag plane t wing span 30-33 lbs 5 cc power lb payload ational flaps hopper door onal Spreader Kit formed aluminum landing gear rglass cowls um-formed canopy tucted extruded foam ply hardwood r -Model actually dustingBRKE $269~ OPTIONAL995 SPREADER SEND siee FOR CATALOG OFC/IRT 1 NEODESHA KS 66757 SAC KITS AND ACCESSORIES316 325-2821 Free Shipping Kit OrdersScott Airplane CompanyVISA MASTERCARD tion figure leads obvious con- distribution assumed could have ious props yielded some important observa clusion propellers re- resulted slight shift noise boun- tions Since explained previously thc gion bounded curves either dont dary necessary exclude 9 x 75 prop goal match peak propeller effi exist simply aren t practical use important thing recognize ciency airspeed model i specified engine desirable propeller pitch/diameter ratio often flown performance othex ranges pitch diameter occur near least 083 would required meet se- speeds does suffer consequence Examrange represented data base propel- lection criteria pitch/diameter ratio pIes noticeable performance degradation lers both because prediction increased further might possible op- off design conditions follow equations derived data acquired erate required airspeed less first thing modelers will notice thil such propellers because props out- noise the static rpm will much lower highside range tend subject prob- recent introduction new line pitch props However expected lems area practicality props allows further investigation result flow separation blades Functional propellers must able ab- hypothesis Known APC Advanced Pre- aircraft i5 restrained theres no sorb power available engine cision Composite props line manu- reason discouraged fact follow reasonable rpm must also perform ad- factured California Landing Products rule thumb prop screaminl equately off design situations distributed hobby dealers through ground engine sufficientl rules out propellers too little diameter Horizon Distributors Several examples loadedwhich means flight perform too much pitch example ad- props flown Miss Martha ance will compromised noise ditional boundary sets lower diam- test aircraft evaluated qualitatively creased course direct opposi eter limit 9 might appropriately instrumentation several tion way modelers choose prop inserted Figure 5 Doing con- produced excellent results 9 present fines realistic choices narrow x 10 P/D 111 A second observation takeofi shaded region figure The APC 9 x 10 propeller produced level acceleration will reduced increas time flight testing per- flight speeds never previously attained es takeoff length small amount Du formed highest pitch/diameter ratio other prop aircraft as- excessive thrust-to-weight ratio 01 prop available use type engine tounding observation however model airplanes however 9 x 75 P/DO83 Notice quietness APC prop propeller major problem Figure 5 prop should theoretically quiet airflow around Finally thrust low flight speeds i satisfy constraints example How- plane audible no data has reduced resulting degraded maneuvet ever inspection data propel- acquired props quite obvi- performance Note aircraft fly ler Figure 3 reveals noise con- ous exhibit increased levels effi- ing fast climb rate excellent its straint would met Remember ciency due increased performance model slows down powet though boundaries Figure 5 decreased noise levels is increased nose raised ef derived imperfect experi- Qualitative comparisons takeoff fect becomes apparent mental data average blade chord lengths climb performance var- Continued page 140 PRACTICAL SIZED GIANT SCALE MODEL PLANS Fiberg/ass Cowlings Canopies Available N1 311/2 1140Span54200 F4u CORSAiR2 1/4 193Span$3000 ASMS ZERO2 1/2 Span $3000Plans RK-20 cuRTiS P40 2 1/2 Span $3000 RK-740 Oucted Fans AT-6 TEXAN 24 1 Span $3000 Phaniom 35 Span $1000 FSF BEARCAT 2 1/2 Span $3000 FQKKER OR127163 Viggen32 Span SiO00 Tripe $2700p36 Span $1000 Pian nd canopy$1500 Order FromCredited First Order $25 Nick Ziroli29 Edgar Dr Smithtown NY 11787 USA516-234-5038 44 Model Aviation Mere Fun SPECIFICATIONS Wing Span62'2 inches Wing Area770 square inches Engine Size 10 cc 90 129 four stroke Designed AMA FAI Turn-around pattern Foam wing stab 3-32 Balsa sheet covering Tricycle conven tional gear fixed retracts Rear side exhaust fiber glass canopy Very positive maneuverable XLT SPECIFIC Wing Span65 inches Length65 inches Wing Area845 square inches Recommended Engine Size 10 cc 90 120 four stroke XLT designed tuned pipe re tract landing gears Capable AMA Turn-around pattern Rear side ex haust SPECIFICATIONS Wing Span Wing Area Engine Size 63'4 inches 700 square inches 50-60 Glow 90 four stroke fun sport pattern turn-around can done Utter Chaos completely built up Balsa construction Canopy engine mount included years proven flying reliablity BRIDI AIRCRAFT DESIGNS INC 23625 Pineforest Lane Harbor City California 90710 213 549-8264 326-5013 SEE YOUR FAVORITE HOBBY SHOP OR RETAIL OUTLET Dealer Inquries Invited PRODUCTS Complete Line Exheust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers Expansion Mufflers copter Ball Mufflers ialized Exhaust Systems Unsurpassed Workmaashin & Padormance Inc Chicago IL 60651 Stay-Brite silver solder Stay Clean flux 1W Harris Co 10930 Deerfield Rd Cincinnati OH 45242 Tools SR batteries tool kit contains SAE metric hex wrenches well crosspoint regular screwdriver bits nifty box ratchet drive screwdriver-type handle very handy use love bits fit electric screwdriver should grab interest somewhat greater interest fact can buy single replacement bits should damaged lost Think sel dom can thing like days SR Batteries Inc Box 287 Bellport NY 11713 tel 1-516/286-0079 Wen portable tool kit #2336 has de scribed previous column contains drill motor Dremel-type grinder saber saw sol dering iron plug cigarette lighter 12-VDC receptacle car have kit find uses dont have people snicker idea toy tools look like toys worked like 110VAC tools no trouble cutting A-in ply wood drilling 4-in holes Ford van body parts Portasol butane-fueled soldering iron also described earlier Suffice say worked fine Camera bought Minolta Weather matic Dual 35 main thought might travel salt air splashes possibility being dropped overboard rule Out use expensive cameras lenses camera 0-ring-sealed against dust moisture has corrosion-resistant yellow plastic exterior will float water accepts DXcoded ASA 100 1000 35mm color print film has pushbutton-selected internal 35mm 50mm lenses features automatic film advance/rewind well autofocus nearest focus point two feet 50mm lens focus-hold feature built shutter button just big cameras tiny built-in flash much better no flash 26 x 31 x 58 less pound camera relatively small light nice hiking must carry everything body much dust Alaska stayed outside camera bought camera its weather resistance learned enjoy fact can worked hand ap preciate its durability favorite lens 35mm-to-tOSmm macro zoom can understand felt limited BATT- CHEKEX Saves Time . Saves Models Install RO Models 3-Level indication receiver battery status press button Precise Rugged Small Light /2 oz Made SA Also custom units other applications Order Today si 495 trom dealer send check money order topostpaid Protune Corp 914 462-6452 PO Box 1808 Poughkeepal NY 12601 NY State residents add sales tax non-macro 35/50mm lens selection use found could get about 85% pic tures wanted Thats pretty good compro mise Any camera just tool good general-purpose tool think would look good field kit perhaps could send some pictures column Minolta Weathermatic Dual 35 local camera store Light 12-VDC fluorescent light plugs automobile cigar lighter very handy put couple strips VelcroTM hooks back permit stick light prati cally anywhere cloth interior van sticks very neatly head-liner seat backs comes off easily need another po sition unit draws 06 amps opposed vans interior lights draw 24 amps provides plenty light reading working whatever have separate deep-cycle RV recreational vehicleEd battery van operate re frigerator lights whatever other items might need total capacity RV battery 70 amp-hours refrigerator alone can exhaust about 17 hours Ito fall asleep refrigerator interior lights battery would exhausted 11 hours Sub stituting fluorescent light vans stan dard interior lights will let battery last 15 hours think extra four hours operating time very valuable RV battery course independent battery starts van wont give manufacturer light because have seen similar units K-Mart Radio Shack etc Prop Noise Continued page 44 last factor controlled fi nal choice prop test aircraft An APC 10 x 8 determined best compromise fact maximum flight speed noise level appear similar 9 x 10 prop low-speed thrust greatly improved As airplane/prop combination demon strates now possible operate model aircraft reduced noise levels little no compromise performance hoped propeller manufacturers will follow APC lead developing introducing new lines will benefit aircraft sizes would major step toward preserving community relations ensur ing continued growth hobby 140 Model Aviation Radio Technique/Myers Continued page 107 Celebrating 10 years producing largest selection giant scale kits available today Design building integrity scale fidelity scale flight characteristics standard IKON NWST 22 kits choose Conclusions research program sponsored AMA order gain better understanding propeller noise major objectives determine con tribution propeller makes over aircraft noise isolate main source prop noise latter proved significant establish guidelines would ulti mately lead quieter model aircraft opera tion combination propeller theory experimental data wind tun nel flight tests provided some definitive conclusions 1 In order reduce noise generated model aircraft dominant source must reduced Provided reasonable muffler used propeller domi nant noise source 2 The dominant source propeller noise torque noise Since efficient propellers generate thrust given amount required torque use will re sult less noise given airspeed 3 Propellers currently available mod elers general quite inefficient use such propellers leads less ideal performance acoustic characteris tics 4 Modelers should select propeller peak efficiency occurs near range airspeeds aircraft will usually operated general props increased pitch/diameter ratios must made available allow such integration wide variety aircraft 5 Noise reduction efforts should directed maximum flight speed condi tion way truly quantify noise attempt reduce mea sure flight 6 It possible develop propeller se lection method based in-flight experimental data addresses both noise performance would give aver age modeler means selecting prop would meet noise regulations performing satisfaction 7 This information will useful applied universally will job ganized groups such AMA clubs hobby dealers manufacturers edu cate individuals enforce proper pro cedures research study described series articles has disclosed nature prob lem propeller noise introduced some solutions Using efficient propellers will reduce model aircraft noise However continued research should directed toward studying effect propeller ge ometry overall efficiency should lead optimal blade designs ulti mately minimal propeller noise Finally carefully organized flight test program would provide data base developing standardized propeller selection criterion SAFE FLYING IS NO ACCIDENT Keithsgo latters numbers some known experimental error associated ex act measurement wire length involved physical portion wire near connector itself cases actual length somewhat intended six inches voltage drops would higher expected Whatever wary installation losses plane Use quality wire quality connectorsbut use sparingly Two new speed controls shown photos month First Jomars latesta large control big systems SC 6 mentioned upcoming new product December 1989 column now closer reality control pictured prototype designed operate 22- 34cell systems features new Signetics chip thats designed drive MOSFET metal-oxide semiconductor field-effect rransistorRMcM gates efficiently course its high-frame-rate design optically coupled Tentative list price $130 Joe Utazi tells product line will soon carried distributors across country competitive pricing will drive price other products down Another new control least new writer Horak imported Canada As understand controls handmade Jiri Horak 3403 Fellmore Drive Mississauga Ontar io Canada L5C 2E1 arc scarce supply Jiri makes several versions including ones brakesContinued page 144 March 1990 141 MOIIUUOUP VUA 114 SCALE 96 STITS PLAYBOYWACO UII-7 113 SCALE 88115 SCALE 72 RC Electrics/Kopski Continued page 47
Edition: Model Aviation - 1990/03
Page Numbers: 39, 40, 41, 42, 43, 44, 140, 141
lodel Propeller NOISE three preceding articles discussing findings ex haustive prop noise study conducted North Carolina State University sponsored AMA has demonstrated average commercial propeller inefficient major source model airplane noise engine properly muf fled What can done solve problem discussed concluding segment ER Vess D Heathcoat R Nagel THE PREVIOUS articles four-part series have shown propellers main source model aircraft noise ex plained various sources propeller noise further shown noise due torque loading dominant different sources Last months article con cluded following comments propellers available generally very inefficient inefficiency leads high torque loads relative thrust produced path model aircraft noise reduc tion therefore clear although perhaps easy Making propellers efficient would reduce noise levels compro mising aircraft performance Simply stated means too much work engine spent turning propeller enough used pulling aircraft through air demonstrate fact consider following thought ex periment propeller model aircraft replaced circular rod clear aircraft would able fly motor would work rod would spin great deal noise would generatedbut no thrust would produced round rod terrible propeller noise generated rod propeller would due thick ness cross-sectional diameter torque torque supplied en gine turn quasi propeller order compare noise gen erated particular propeller rod se lected would have size such engine full throttle would turn either rod propeller same rpm means engine would doing same amount work case may surprised learn rod propeller produce similar noise levels similar operating conditions However noise radiating rod has nothing propelling aircraft fore noise due thrust Unfortunately propellers available model ers little too much like rodthey generate large amount torque noise given amount thrust question concerning what can done solve problem depends upon cares responsible Cer tainly people live near flying sites disturbed noise can counted among care local residents often solve problem pro testing such way create new different problem pilotsloss flying site responsibility model aircraft noise does indeed lie fliers manufacturers What can groups combination widespread ed ucation modelers conscientious flying field practices state-of-the-art equip ment will required reach appropri ate workable solution hoped information series articles will pro vide some necessary education Surely manufacturers will continue recognize severity noise issue direct efforts accordingly However its actions individual modelers March 1990 39 Left Argentinean Quique Somenzini displays business end aircraft FAI World Aerobatics Championships Chesapeake VA FutabalYS 12 four-stroke engine turns APC 14 x 14 pro peller muffler Hatori pipe unit added exhaust exten sion Above Somenzinis aircraft held taxiway manda tory static noise readings made measured SPL 855 dBA recorded lowest contest However text re veals limitations applying static readings flight conditions Lower Pitch/Diameter Higher Pitch/Diameter Increoming Airupeed re 1 eller/ Aircraft Matching 120110100-J 0 n C 3 900 C8070 0 Best Fit Line 0 0 08 o -2dBA 0 o0 8090 Predicted SPL dBA will influence continued growth hobby After theyre ones determine what fly isnt difficult understand just sin gle inconsiderate misinformed pilot can create trouble entire club So formation follows will useful accompanied little common sense What t Its model aircraft flying high speeds far runway possibly nearer dis tant houses likely annoy living within proximity flying site typical flight noise runway generally short duration compared time model air noise associated preparation takeoff landing may reaching neighbors Therefore seems obvious strictest noise control efforts should di rected toward high-speed flight condi tion explained first article flying aircraft differs greatly both propel ler performance radiated noise restrained craft ie having no ward motion due differences flow fields around prop case Thus current practice measur ing noise level aircraft being held rest ground fact dealing wrong noise wrong condition wrong place 1989 F3A World Aerobatics Champi onships held Chesapeake VA provided case point FAI competition SPL sound pressure level measured dis tance three meters sideline aircraft must exceed 98 dB quite loud Interestingly enough although aircraft met requirement varying degrees very quiet flighta few point being barely audible fact qualitative stand point planes much quieter air static readings would have suggested can explained examining high-pitch propellers have become pop ular among Pattern fliers prime example particular competition APC 14 x 14 prop Argentinean Quique Somen zinis aircraft measured quietest model meet has proven such propellers perform very well significantly decreasing over noise High-pitch props reach peak efficiency higher flight speeds therefore generate less noise relative other props such speeds However excessive angle tack propeller blades model restrained ground promotes flow separation resulting completely differ ent acoustic signature represent ative case aircraft flight true Somenzinis air craft produced noise level reading 855 dB three meters measured statically must realized low level result flow phenomena dont occur under normal flight conditions fore notably quiet in-flight operation aircraft cannot attributed same factors produced static noise read40 Model Aviation U C U ILl a L a -S 01 S L U 1o1o Figure 2 e Prediction Evaluation PointPropPID 111x764 211x655 311x545 410x770 510x660 610x550 710x550 89x71/283 99x778 109x867 119x556 11 0 N 198dBA 115110m 0 105I oi 100-J estFitLine 0 XMuffler 90-0 Standard 0 High Performance 859095100105110115 Max OASPL Equation 1 dBA Figure 3 e Prediction Evaluation Maximum Airspeed gs What tells us way properly attack model aircraft noise roblem develop some means mea uring sound generated airlane flightwhich its per eived bothersome round course suggesting model aircraft oise should measured flight intro Luces variety logistical problems act just about conceivable method Las practical limitations Fortunately ver possible develop method iredicting model aircraft noise flight rom experimental data acquired under trictly controlled conditions Thus ac ual in-flight measurements could made y qualified individuals proper quipment resulting data could ised create noise prediction method everyday modeler fact same lata could also used predict aircraft erformance would possible Jevelop propeller selection method Nould address both performance noise onsiderations Until recently modelers simply icked two three props listed y engine manufacturer satisfactory engine particular displacement rhis poor way choose propeller rhe proper choice can made neeting specific requirements par icular aircraft/engine combination de ired flight condition good way illus rate point comparing typical rainer powered 40-cu-in engine iigher performance sport aircraft utilizing same engine trainer designed fly low air peeds easily managed begin iers proper propeller case should efficient quiet slow tpeeds depicted Figure 1 Such prop would generally characterized having moderate blade pitch sufficient diame er absorb power generated en gine specified limit airspeed comparison high-performance sport aircraft designed fly much faster Pro pellers best suited such craft ones should reach peak efficiency higher airspeeds indicated sec ond curve figure might achieved increasing pitch-to-diam eter ratio important note since dealing fixed-pitch propellers range high efficiency limited fore propeller selected should peak efficiency occurs likely airspeed particular plane Some compromise performance pos sibly noise will evident other air speeds flight envelope extent performance degradation off de sign conditions has significant effect suitability particular prop given aircraft As preceding example has shown pro peller selection driven aerody namic characteristics aircraft ever great diversity types models flown considerably complicates pro cedure developing single propeller se lection method would applicable model airplanes Dividing model aircraft groups similar aerody namic characteristics would reduce num ber variables Data obtained flight tests aircraft typical certain group could used derive performance acoustic prediction methods would applicable other aircraft group An appropriate prop selection criter ion would based prediction infor mation Consider preliminary example following broad categorization trainers sport aircraft high-performance air craft Since divisions based12 typical maxi mum flight speeds some overlapping11 among categories would expected10 Miss Martha aircraft whtch utilized collect9 flight test data dur- ing course of8 research servesas example advanced sport7 aircraft Thus prediction method6 resulting manipulation research data might5 expected ap ply similar sport aircraft6 Data limitations performance data acquired dur ing tests included airspeed propeller rotational speed down-linked telemetry system acoustic data corres ponding performance readings con sisted OASPL overall sound pressure level values recorded air craft passed over microphone visually interpreted separation distance approxi mately two meters should noted data acquired under less ideal circumstances therefore subject error due following difficulties 1 proper engine needle valve set ting difficult maintain throughout entire series runs resulting inconsist encies available power contribute sim ilar inconsistencies both performance March 1990 41 200PoIntPropP/fl 111x764 211x655 311x545 410x770 c 190510x660 a6lOxS506 E7lOxS50 69x753 99x778 l80109x667 119x55685kmph 0 170Best Fit Line 6 S uffler 2 x 150 0 2 0 140 140150160170180190200 Max flight Speed Equation 2 krtiph Figure 4 ormance Prediction Evaluation Full Throttle o Standard High Performance Noise Constraint C 0 C 0 C 0 C Practical Use Range 0 Airspeed Constraint 9 101112 Diameter inches Figure 5 eller Selection Map acoustic data 2 The simplicity airborne teleme try system limited achievable accuracy performance data recorded ground 3 Varying wind conditions drasti cally different aircraft test speeds contrib uted difficulties consistently flying di rectly over sound-level meter 4 The flyover distances simply judged visual comparison nearby ref erence point therefore subject hu man error should noted however data recorded after re peated within acceptable limits three good passes over microphone list error sources introduced discredit data realistically qual ify extent its accuracy famil iarize reader problem areas need addressed prior performing extensive flight tests Any conclu sions drawn carefully scrutinized potential error mind adjusted accordingly conclu sions derived lab experiments favorably supported flight test data Noise prediction Correlation acous tic data flight tests desired geometric parameters measured propellers data base provided foundation development noise prediction method involved rather tedious task mathematically weighing within single equation contribution individual parameter made overall noise level determining well resulting equation predicted ex perimental values repeating entire process until error minimized result effort following equation actually less threatening appears OASPLpred 110 log D15 log P 40 log NllO log [175 logl JIit]f 10 log 1 8Mt4I [32 log {D-93±15}1151 6429 variables expression describe propeller terms particu lar interest investigation de fined follows D diameter inches P h inches N tional speed rpm o dity outer half prop J nce ratio prop tip Mach number plotting predicted noise against measured noise Figure 2 quality prediction equation can visualized perfect prediction equation would repro duce experimental data exactly means point would collapse onto line unit slope two plotted example slope best fit line through data has value 097 indicates prediction repre sents available data quite well data scatter primarily due exper imental measurement error has calcu lated mean value approximately 2 dBA compares favorably noise prediction equations developed aero space industry Remember though usefulness prediction method deter mined both quality data quality equation equation have given however can predict propeller noise listed variables known Obviously severely limits practical use equation since few modelers have means measuring airspeed engine rpm flight Flying clubs need something simpler work witha method uses easily measured parameters development another equation applies maximum flight speed speed interest way allows significant simplification resulting equation 1 indeed practical since based entirely propeller geome try ruler pocket calculator tools required 1 Max OASPL og [D48 x P/Di x C7SR/R66 x CSOR/C7SRS6S x 625] 4 input variables equation D eller diameter measured inches P/D h-to-diameter ratio CxR eller blade chord measured inches stated location exam ple C5R chord length halfradius position midspan blade R Propeller radius half diameter measured inches Power parameter 10 for standard stock mufflers 105 high-performance mufflers last parameter H serves adjust performance aircraft ex haust system has found socalled high-performance mufflers available modeler today tend increase maximum flight speed general re sult noise speed However model equipped highperformance muffler tested same flight speeds attainable ad vanced muffler noise level remains roughly unchanged comparison results predic tion equation measured results ob 42 Model Aviation Left Several new APC propellers displayed front Miss Martha test aircraft exampies depicted nave diameters rangin nine 11 inches pitches six seven eight 10 inches 9 x 10 propeller mounted 0S Max 46SF engine providec startling flight speeds extremely low noise levels Right John Herbert Raleigh Aeromasters RC Club returns pits after flight An APC 9 x 6 propeller used Goldberg Eaglet powered OS Max 25 engine Although resulting increase max imum flight speed suits style flying proper propeller class aircraft would probably have lower pitch/diameter ratio tc shift peak prop efficiency lower airspeed APC propellers Landing Products distributed through Horizon Distributors SAFE FLYING IS NO ACCIDENT THE BEST FUSELAGE JIG EVER PERIOD Provides Solid Support Accurate Building Rugged Construction 7 Ply Aircraft Plywood Provides Lifetime Use Two Sizes Available Regular Fuselages Up 6 Wide Jumbo Fuselages Up 9 Wide Use Own Building Buard Work Bench Base Mount Jig Station Uni-Strut Guide Rails Most Versatile Set-Up Contains Complete Hardware Instructions Including Uni-Strut Information Buxof4StandardJigStatioflsS1795 Boxof4JumboJigStations1995 Two 5 ft long Guide Rails including mounting nuts 2195 ained Miss Martha aircraft full hrottle given Figure 3 noise pro luced different propellers figire ranges about 87 dBA over 110 dBA Propeller selection made differ ence between quiet aircraft ex tremely noisy However because aforementioned measurement error dif ficult obtain definite conclusions di rectly figure Nevertheless general trends support claim props higher pitch-todiameter ratios produce less noise flight Furthermore examples high-performance muffler used indi cate increased noise levels because engine performing better significance comparison shown Figure 3 demonstrates first possi ble obtain prediction equation ex perimental data second accu racy data controls usefulness such equation Performance prediction As discussed pre viously goal exercise pro duce example propeller selection method addresses both noise per formance performance data acquired flight tests manipulated same manner derive equation would predict maximum flight speed model within same general category sport aircraft ie aerodynamic characteristics similar Miss Martha IVANS MAGIC GADGET protractor device used Ivan Kristensen accurately measure aileron elevator rudder throw Takes guess work out trimming out airplane quality tool conspiete instructions log book carrying case5795 U PLUG-IN ADJUSTABLE STAB KIT last tan optimize stab incidence best flight charac teristics pair glass filled nylon adjusters included provide micro screw adjustment smaller front tube Main tube aluminum matthing phenolic socket 5695 Include 52 SOlItem UPS esidents Add 6% Sales Tax GATOR RIC PRODUCTS 3713 Pompano Dr acola FL 32514 476-8639 test aircraft Equation 2 result such effort Note variables same defined Equation 1 2 Vmax predicted x [DO x PID015 x C7SRIR9 x CSoRIC7SR65 X C9oR/C7SR055 x PH4] Figure 4 presents graphic comparison measured predicted flight velocity error approximately 5% mean flight velocity translates about 85 kmph Comparison figure Fig ure 3 reveals general trend props higher pitch-to-diameter ra tios data base produced highest maximum flight speed lowest noise Once again consistent labo ratory results Propeller selection method further uti lizing prediction equations 1 2 practical method selecting propeller satisfies reasonable noise per formance constraints can developed aircraft categoryie sport air craft. Consider task selecting pro peller meets following criteria Aircraft Miss Martha Advanced level sport Engine 05 Max 46 SF Muffler PLUG-IN WING ADJUSTER KIT Four glass filled nylon brackets included key wing panels front rear allow accurately adjust panel straight flight Complete hardware & InstructIons 5995 WING TUBE & SOCKETS Aluminum alloy tubing plug-in wings Included pair special slip-fit phenolic sockets build wing structure Now size models 718 diax2S 895 1diax2S 995 1dias351495 Davis Diesel Soundmaster high perform ance Desired maximum flight speed 175 kmph 109 mph Flying site noise regulation 880 dBA @ two meters flyover ap prox 853 dBA @ three meters Reference should made equations 1 2 Since high-performance muf fler used H Furthermore mea surements taken propellers data base produce following average blade chord distribution C7SR/R C5oR/C75R C9oRIC75R0725 will assumed propeller ques tion has expected blade chord distribu tion substituting known values equations following mathemati cal inequalities may written terms blade pitch diameter both inches 1 P155 x l05 x Noise Constraint 2aP 1 295 X Speed Constraint Plotting both same figure Figure 5 produces finite boundary above pitch/diameter combinations sat isfy constraints can found Examina RDABLE AL POWER INTRODUCTORY 849 SPECIAL SEND 5100 TECHNICAL DATA THE MIKE GR6- 120 2-CYCLE POWERPLANT 6 CYLINDER RADIAL ANTY LBSOFTHRuST * 25 SHP IDYNO TESTEDI * NO VIBRATION III * SINGLE NEEDLE VALVE * 8 STAINLESS BALL BROS * IDLES AT 1800 RPM * OIL LUBRICATED GEARS * 3/8 HARDENED SE SHAFT * FULLY FLIGHT TESTED * DIAMETER 8 TO PLUG TIPS * WEIGHT 4 LEE INCLuDING INTEGRAL MOUNT AND MUFFLER * SWINGS 18/8 PROF /8 8880 RPM * EXCEEDS QuADRA 35 IN POWER AND ZENOAH G38 IN THRUST * GLOW FUEL USED-1S% * GLOW PLUG LEADS INCLUDED * READY TO FLY NOT KITI 33 DEALER INQUIRIESs-% INVITEDp TECHNOLOGIES INC 7 Greenwood Lane VaiSsIla New YorE lOSES 1914 888-9373 FAT PENDING TEST FLOWN IN 72 GM PLASTICS F4U CORSAIR 72 BOB DIVELYS SU-2 BIPLANE 88 PROCTOR NIEUPORT 28 BIPLANE 58 MONOCOUPE EISA March 1990 43 $1695 LIST THE PIPER BRAVE 1/4 scale model Pipers latest Ag plane t wing span 30-33 lbs 5 cc power lb payload ational flaps hopper door onal Spreader Kit formed aluminum landing gear rglass cowls um-formed canopy tucted extruded foam ply hardwood r -Model actually dustingBRKE $269~ OPTIONAL995 SPREADER SEND siee FOR CATALOG OFC/IRT 1 NEODESHA KS 66757 SAC KITS AND ACCESSORIES316 325-2821 Free Shipping Kit OrdersScott Airplane CompanyVISA MASTERCARD tion figure leads obvious con- distribution assumed could have ious props yielded some important observa clusion propellers re- resulted slight shift noise boun- tions Since explained previously thc gion bounded curves either dont dary necessary exclude 9 x 75 prop goal match peak propeller effi exist simply aren t practical use important thing recognize ciency airspeed model i specified engine desirable propeller pitch/diameter ratio often flown performance othex ranges pitch diameter occur near least 083 would required meet se- speeds does suffer consequence Examrange represented data base propel- lection criteria pitch/diameter ratio pIes noticeable performance degradation lers both because prediction increased further might possible op- off design conditions follow equations derived data acquired erate required airspeed less first thing modelers will notice thil such propellers because props out- noise the static rpm will much lower highside range tend subject prob- recent introduction new line pitch props However expected lems area practicality props allows further investigation result flow separation blades Functional propellers must able ab- hypothesis Known APC Advanced Pre- aircraft i5 restrained theres no sorb power available engine cision Composite props line manu- reason discouraged fact follow reasonable rpm must also perform ad- factured California Landing Products rule thumb prop screaminl equately off design situations distributed hobby dealers through ground engine sufficientl rules out propellers too little diameter Horizon Distributors Several examples loadedwhich means flight perform too much pitch example ad- props flown Miss Martha ance will compromised noise ditional boundary sets lower diam- test aircraft evaluated qualitatively creased course direct opposi eter limit 9 might appropriately instrumentation several tion way modelers choose prop inserted Figure 5 Doing con- produced excellent results 9 present fines realistic choices narrow x 10 P/D 111 A second observation takeofi shaded region figure The APC 9 x 10 propeller produced level acceleration will reduced increas time flight testing per- flight speeds never previously attained es takeoff length small amount Du formed highest pitch/diameter ratio other prop aircraft as- excessive thrust-to-weight ratio 01 prop available use type engine tounding observation however model airplanes however 9 x 75 P/DO83 Notice quietness APC prop propeller major problem Figure 5 prop should theoretically quiet airflow around Finally thrust low flight speeds i satisfy constraints example How- plane audible no data has reduced resulting degraded maneuvet ever inspection data propel- acquired props quite obvi- performance Note aircraft fly ler Figure 3 reveals noise con- ous exhibit increased levels effi- ing fast climb rate excellent its straint would met Remember ciency due increased performance model slows down powet though boundaries Figure 5 decreased noise levels is increased nose raised ef derived imperfect experi- Qualitative comparisons takeoff fect becomes apparent mental data average blade chord lengths climb performance var- Continued page 140 PRACTICAL SIZED GIANT SCALE MODEL PLANS Fiberg/ass Cowlings Canopies Available N1 311/2 1140Span54200 F4u CORSAiR2 1/4 193Span$3000 ASMS ZERO2 1/2 Span $3000Plans RK-20 cuRTiS P40 2 1/2 Span $3000 RK-740 Oucted Fans AT-6 TEXAN 24 1 Span $3000 Phaniom 35 Span $1000 FSF BEARCAT 2 1/2 Span $3000 FQKKER OR127163 Viggen32 Span SiO00 Tripe $2700p36 Span $1000 Pian nd canopy$1500 Order FromCredited First Order $25 Nick Ziroli29 Edgar Dr Smithtown NY 11787 USA516-234-5038 44 Model Aviation Mere Fun SPECIFICATIONS Wing Span62'2 inches Wing Area770 square inches Engine Size 10 cc 90 129 four stroke Designed AMA FAI Turn-around pattern Foam wing stab 3-32 Balsa sheet covering Tricycle conven tional gear fixed retracts Rear side exhaust fiber glass canopy Very positive maneuverable XLT SPECIFIC Wing Span65 inches Length65 inches Wing Area845 square inches Recommended Engine Size 10 cc 90 120 four stroke XLT designed tuned pipe re tract landing gears Capable AMA Turn-around pattern Rear side ex haust SPECIFICATIONS Wing Span Wing Area Engine Size 63'4 inches 700 square inches 50-60 Glow 90 four stroke fun sport pattern turn-around can done Utter Chaos completely built up Balsa construction Canopy engine mount included years proven flying reliablity BRIDI AIRCRAFT DESIGNS INC 23625 Pineforest Lane Harbor City California 90710 213 549-8264 326-5013 SEE YOUR FAVORITE HOBBY SHOP OR RETAIL OUTLET Dealer Inquries Invited PRODUCTS Complete Line Exheust Systems * Tuned Pipes led Tuned Pipes * Headers uri Mufflers Expansion Mufflers copter Ball Mufflers ialized Exhaust Systems Unsurpassed Workmaashin & Padormance Inc Chicago IL 60651 Stay-Brite silver solder Stay Clean flux 1W Harris Co 10930 Deerfield Rd Cincinnati OH 45242 Tools SR batteries tool kit contains SAE metric hex wrenches well crosspoint regular screwdriver bits nifty box ratchet drive screwdriver-type handle very handy use love bits fit electric screwdriver should grab interest somewhat greater interest fact can buy single replacement bits should damaged lost Think sel dom can thing like days SR Batteries Inc Box 287 Bellport NY 11713 tel 1-516/286-0079 Wen portable tool kit #2336 has de scribed previous column contains drill motor Dremel-type grinder saber saw sol dering iron plug cigarette lighter 12-VDC receptacle car have kit find uses dont have people snicker idea toy tools look like toys worked like 110VAC tools no trouble cutting A-in ply wood drilling 4-in holes Ford van body parts Portasol butane-fueled soldering iron also described earlier Suffice say worked fine Camera bought Minolta Weather matic Dual 35 main thought might travel salt air splashes possibility being dropped overboard rule Out use expensive cameras lenses camera 0-ring-sealed against dust moisture has corrosion-resistant yellow plastic exterior will float water accepts DXcoded ASA 100 1000 35mm color print film has pushbutton-selected internal 35mm 50mm lenses features automatic film advance/rewind well autofocus nearest focus point two feet 50mm lens focus-hold feature built shutter button just big cameras tiny built-in flash much better no flash 26 x 31 x 58 less pound camera relatively small light nice hiking must carry everything body much dust Alaska stayed outside camera bought camera its weather resistance learned enjoy fact can worked hand ap preciate its durability favorite lens 35mm-to-tOSmm macro zoom can understand felt limited BATT- CHEKEX Saves Time . Saves Models Install RO Models 3-Level indication receiver battery status press button Precise Rugged Small Light /2 oz Made SA Also custom units other applications Order Today si 495 trom dealer send check money order topostpaid Protune Corp 914 462-6452 PO Box 1808 Poughkeepal NY 12601 NY State residents add sales tax non-macro 35/50mm lens selection use found could get about 85% pic tures wanted Thats pretty good compro mise Any camera just tool good general-purpose tool think would look good field kit perhaps could send some pictures column Minolta Weathermatic Dual 35 local camera store Light 12-VDC fluorescent light plugs automobile cigar lighter very handy put couple strips VelcroTM hooks back permit stick light prati cally anywhere cloth interior van sticks very neatly head-liner seat backs comes off easily need another po sition unit draws 06 amps opposed vans interior lights draw 24 amps provides plenty light reading working whatever have separate deep-cycle RV recreational vehicleEd battery van operate re frigerator lights whatever other items might need total capacity RV battery 70 amp-hours refrigerator alone can exhaust about 17 hours Ito fall asleep refrigerator interior lights battery would exhausted 11 hours Sub stituting fluorescent light vans stan dard interior lights will let battery last 15 hours think extra four hours operating time very valuable RV battery course independent battery starts van wont give manufacturer light because have seen similar units K-Mart Radio Shack etc Prop Noise Continued page 44 last factor controlled fi nal choice prop test aircraft An APC 10 x 8 determined best compromise fact maximum flight speed noise level appear similar 9 x 10 prop low-speed thrust greatly improved As airplane/prop combination demon strates now possible operate model aircraft reduced noise levels little no compromise performance hoped propeller manufacturers will follow APC lead developing introducing new lines will benefit aircraft sizes would major step toward preserving community relations ensur ing continued growth hobby 140 Model Aviation Radio Technique/Myers Continued page 107 Celebrating 10 years producing largest selection giant scale kits available today Design building integrity scale fidelity scale flight characteristics standard IKON NWST 22 kits choose Conclusions research program sponsored AMA order gain better understanding propeller noise major objectives determine con tribution propeller makes over aircraft noise isolate main source prop noise latter proved significant establish guidelines would ulti mately lead quieter model aircraft opera tion combination propeller theory experimental data wind tun nel flight tests provided some definitive conclusions 1 In order reduce noise generated model aircraft dominant source must reduced Provided reasonable muffler used propeller domi nant noise source 2 The dominant source propeller noise torque noise Since efficient propellers generate thrust given amount required torque use will re sult less noise given airspeed 3 Propellers currently available mod elers general quite inefficient use such propellers leads less ideal performance acoustic characteris tics 4 Modelers should select propeller peak efficiency occurs near range airspeeds aircraft will usually operated general props increased pitch/diameter ratios must made available allow such integration wide variety aircraft 5 Noise reduction efforts should directed maximum flight speed condi tion way truly quantify noise attempt reduce mea sure flight 6 It possible develop propeller se lection method based in-flight experimental data addresses both noise performance would give aver age modeler means selecting prop would meet noise regulations performing satisfaction 7 This information will useful applied universally will job ganized groups such AMA clubs hobby dealers manufacturers edu cate individuals enforce proper pro cedures research study described series articles has disclosed nature prob lem propeller noise introduced some solutions Using efficient propellers will reduce model aircraft noise However continued research should directed toward studying effect propeller ge ometry overall efficiency should lead optimal blade designs ulti mately minimal propeller noise Finally carefully organized flight test program would provide data base developing standardized propeller selection criterion SAFE FLYING IS NO ACCIDENT Keithsgo latters numbers some known experimental error associated ex act measurement wire length involved physical portion wire near connector itself cases actual length somewhat intended six inches voltage drops would higher expected Whatever wary installation losses plane Use quality wire quality connectorsbut use sparingly Two new speed controls shown photos month First Jomars latesta large control big systems SC 6 mentioned upcoming new product December 1989 column now closer reality control pictured prototype designed operate 22- 34cell systems features new Signetics chip thats designed drive MOSFET metal-oxide semiconductor field-effect rransistorRMcM gates efficiently course its high-frame-rate design optically coupled Tentative list price $130 Joe Utazi tells product line will soon carried distributors across country competitive pricing will drive price other products down Another new control least new writer Horak imported Canada As understand controls handmade Jiri Horak 3403 Fellmore Drive Mississauga Ontar io Canada L5C 2E1 arc scarce supply Jiri makes several versions including ones brakesContinued page 144 March 1990 141 MOIIUUOUP VUA 114 SCALE 96 STITS PLAYBOYWACO UII-7 113 SCALE 88115 SCALE 72 RC Electrics/Kopski Continued page 47