HELICOPTERS Dave Chesney THIS month next few column will primarily beginners Since col umns have told about RC helicopter aerobatics including impossible inverted flight auto-rotations choppers perhaps Ive left out few notes about basics Just does darn thing fly set up learn fly much does cost get biggie dont write book few questions heard exception last question Ill try answer few answers intended impressively technical since best am hobbyist aeronautical engineer RC helicopter unlike other enginedriven RC aircraft full-scale counter parts Both helicopter airplane obey basic laws flight flight controls similar helicopter mechanically cnmnlicted Since mnt nf familiar radio control airplanes lets compare trainer airplane helicopter airplane has engine prop thrust wings lift helicopter has engine main rotor system both lift thrust airplane controlled about its flight axis servos connected its three flight controls ailerons elevator rudder servo used control speed engine heli copter controlled about its flight axis servos connected its three basic flight controls fore/aft cyclic right/left cyclic tail rotor servo used engine control speed rotor same throttle servo fifth servo parallel throttle servo may also control collective pitch OK before get flight control similarities lets take look airplane wing agree fixed angle attack Oops see Figure 1 faster wing moves through air against relative wind lift generated Please assume wing stalled consider example airplane tends zoom upward after high speed dive using up elevator control Now since rotor blade rotating wing helicopter does require forward movement aircraft because wing propelled through air engine airplane wing provides lift higher speeds helicopter rotor must also generate lift engine revolves against its relative wind note relative wind opposite direction rotation rotor blades higher rpms way controlling ascent descent helicopter setting pitch ofthe main rntnr hlades chnoino niilv nppd et / rotor turns Helicopters using throttle control often called fixed pitch heli copters should really called fixed collective pitch helicopters What collective pitch both blades two-blade system set 0 degrees moved say 6 degrees positive pitch have moved both blades together collectively 0 6 degrees blades could fixed pitch setting common RC helicopters rotor blade pitch may varied collectively negative positive variable collective pitch lift rotor system can varied independently rotor speed throttle setting An excellent example independent collective pitch use Tach-tron device associated RC gear installed chopper can adjusted provide constant rotor rpm assum ing engine powerful enough maintain pre-set rpm maximum collective pitch angle Tach-tron governor usually included hellcopter kits time both throttle collective pitch controlled simultaneously using same servo servo function same control channel radio throttle stick controls both com mon throttle collective linkages ad justed pitch settings taking best possible advantage engine power both airplanes helicopters engine power can significant factor successful flight aircraft problems creating enough lift overcome gravity lift generated drag Drag bad news airplane drag determines engine power re 117 XECUTIVE CORP AmItyvIll NY 11701 FAI team selection program Its again well underway time read Subject vote program entrants Team Finals will Pensacola FL excellent flying site over Labor Day weekend Rae Fritz excellent contest director will keep everybody honest Its guaranteed excitement worth watching cant compete outcome Second World Championships last year Belgium surely will have influence designs year So want see what F3B about see some designs dreams year ago think PensacolaLabor Day further information program contact Ray Marvin 2781 South Garfield Denver CO 80210 Lets go flying Dan Pruss RR 2 Box 490 Plainfield IL 60544 RC HELICOPTERS/CHESNEY co ntinued page 36 quired pull wing through air fast enough get plane air keep same true helicopterbut airplane drag largely result induced drag creating lift plus parasitic profile drag caused resistance bumps lumps like wheels canopies other junk sticking out airstream helicop ter also subject mechanical drag Powerrobbing drag bad enough binds helicopter gear train course binds running friction factor mechanics drive system should assembled carefully reduce friction Now succeed overcoming drag gravity get helicopter airplane moving forward flight similarities control response can checked out See Figure 2 airplane controlled about roll axis its ailerons increasing decreasing lift ofeach wing tip opposite other helicopter control similar ailerons called right/left cyclic lateral cyclic So roll bank airplane move aileron stick helicopter rolled banked using cycliclateral cyclic pitch axisthe airplane controlled elevator down elevator causes nose drop up elevator nose rise copter friend cyclic back again now forelaft cyclic longitudinal cyclic Longi tudinal cyclic causes helicopter nose pitch down forward command up aft command remember forward flight right now forward flight helicopter tail rotor similar rudder airplane both control yaw nose aircraft right left Right stick right yaw left stick left yaw airplane note some RC heli copter fliers set control linkage tail rotor right stick gives left nose right tail boom movement like fullscale helicopter Reasons changing tail rotor control will become apparent begin flight training set up normal yaw initially examples flight control similarity aircraft moving forward through air An airplane motion through air called parked tied-downmaybe crashed airplane must moving forward against relative airflow speed sufficient provide lift overcome gravity helicopter may indeed stop move rearward sideways because engine-driven rotating wings provide relative airflow helicopter will lifted off ground engine power rotor pitch set blades rotating against relative wind such way provide enough lift overcome gravity no other forces acting helicopter will hover Now lateral longitudinal cyclic controls may used slide helicopter laterally left right longi tudinally forward rearward tail rotor must used yaw control also keep fuselage spinning around against rotation main rotor Well get back tail rotor later now what cyclic pitch rotor blades Cyclic pitch changes responsible lateral longitudinal movement helicopter An application cyclic control causes pitch blade change opposite other effect blade will oscillate fixed collective pitch setting through positive relative pitch back collective reference pitch relative negative pitch setting back reference collective pitch setting highest lowest relative pitch positions blade will determined position cyclic stick Keep mind blade reaches its highest pitch opposite blade will its lowest pitch excursion blade during revolution like sine wave See Figure 3 Next month will have about cyclic collective pitch rotor head swash plate Dave Chesney Rt 9 Box 621A Greensboro NC 27409 CL BEECHCRAFT/HAUGHT continued page 40 made Instruct helper watch excessive outward yaw unlevel wings will able notice things circles center well another opinion always useful Too much outward yaw causes excessive line tension can see top bottom wings indicates correction needed Both conditions may alleviated relocating leadout guide see tops wings lower guide too much outward yaw move guide forward etc tail heavy model will too difficult control Too much nose weight makes model too sluggish controls too sensitive move pushrod bellcrank down elevator horn etc Level flight boring will find Beech fully aerobatic Loops basic maneuver Most beginners hold fixed amount too much up resulting mushy loop Try varying control throughout loop making big round Lazy eights logical progression inverted flight Begin normal loop neutral ize controls kr way through loop hesitating split second model its back shallow dive give down elevator come around end eight returning level flight Practice lazy eights extending inverted protion until achieve magical first lap inverted flight its merely matter practice Soon youll able tolerate lap upright level flight row Staggerwing SAFE FLYING IS NO ACCIDENT July 1980 117 Deep uselag full cabin b flight capability 112 40 to 60 EngInes igepan dowels lightness movable tail ORGANIZED surfaces actuated movable stubsHee S set 4 sturdy fries hoS OVer fit tail Soar Gull only4 years Vt favorite 8 11 magazirtes different its package clever innovations 4 MAG FILES $495 linkages designsend 5495 plus St 00 postage handtrrrg DON INDUSTRIES P0 BOX 388-K DOVER NH 03820 yourEngine flioo1 G IOw MIUGUE 1/eA Vat Scale Power Usable Power Greater Economy Send 4O & Stamped Addressed Envelope Dealer Inquiry Invited Davis Diesel Development Inc Box 141 Milford CT 06460
Edition: Model Aviation - 1980/07
Page Numbers: 36, 117
Edition: Model Aviation - 1980/07
Page Numbers: 36, 117
HELICOPTERS Dave Chesney THIS month next few column will primarily beginners Since col umns have told about RC helicopter aerobatics including impossible inverted flight auto-rotations choppers perhaps Ive left out few notes about basics Just does darn thing fly set up learn fly much does cost get biggie dont write book few questions heard exception last question Ill try answer few answers intended impressively technical since best am hobbyist aeronautical engineer RC helicopter unlike other enginedriven RC aircraft full-scale counter parts Both helicopter airplane obey basic laws flight flight controls similar helicopter mechanically cnmnlicted Since mnt nf familiar radio control airplanes lets compare trainer airplane helicopter airplane has engine prop thrust wings lift helicopter has engine main rotor system both lift thrust airplane controlled about its flight axis servos connected its three flight controls ailerons elevator rudder servo used control speed engine heli copter controlled about its flight axis servos connected its three basic flight controls fore/aft cyclic right/left cyclic tail rotor servo used engine control speed rotor same throttle servo fifth servo parallel throttle servo may also control collective pitch OK before get flight control similarities lets take look airplane wing agree fixed angle attack Oops see Figure 1 faster wing moves through air against relative wind lift generated Please assume wing stalled consider example airplane tends zoom upward after high speed dive using up elevator control Now since rotor blade rotating wing helicopter does require forward movement aircraft because wing propelled through air engine airplane wing provides lift higher speeds helicopter rotor must also generate lift engine revolves against its relative wind note relative wind opposite direction rotation rotor blades higher rpms way controlling ascent descent helicopter setting pitch ofthe main rntnr hlades chnoino niilv nppd et / rotor turns Helicopters using throttle control often called fixed pitch heli copters should really called fixed collective pitch helicopters What collective pitch both blades two-blade system set 0 degrees moved say 6 degrees positive pitch have moved both blades together collectively 0 6 degrees blades could fixed pitch setting common RC helicopters rotor blade pitch may varied collectively negative positive variable collective pitch lift rotor system can varied independently rotor speed throttle setting An excellent example independent collective pitch use Tach-tron device associated RC gear installed chopper can adjusted provide constant rotor rpm assum ing engine powerful enough maintain pre-set rpm maximum collective pitch angle Tach-tron governor usually included hellcopter kits time both throttle collective pitch controlled simultaneously using same servo servo function same control channel radio throttle stick controls both com mon throttle collective linkages ad justed pitch settings taking best possible advantage engine power both airplanes helicopters engine power can significant factor successful flight aircraft problems creating enough lift overcome gravity lift generated drag Drag bad news airplane drag determines engine power re 117 XECUTIVE CORP AmItyvIll NY 11701 FAI team selection program Its again well underway time read Subject vote program entrants Team Finals will Pensacola FL excellent flying site over Labor Day weekend Rae Fritz excellent contest director will keep everybody honest Its guaranteed excitement worth watching cant compete outcome Second World Championships last year Belgium surely will have influence designs year So want see what F3B about see some designs dreams year ago think PensacolaLabor Day further information program contact Ray Marvin 2781 South Garfield Denver CO 80210 Lets go flying Dan Pruss RR 2 Box 490 Plainfield IL 60544 RC HELICOPTERS/CHESNEY co ntinued page 36 quired pull wing through air fast enough get plane air keep same true helicopterbut airplane drag largely result induced drag creating lift plus parasitic profile drag caused resistance bumps lumps like wheels canopies other junk sticking out airstream helicop ter also subject mechanical drag Powerrobbing drag bad enough binds helicopter gear train course binds running friction factor mechanics drive system should assembled carefully reduce friction Now succeed overcoming drag gravity get helicopter airplane moving forward flight similarities control response can checked out See Figure 2 airplane controlled about roll axis its ailerons increasing decreasing lift ofeach wing tip opposite other helicopter control similar ailerons called right/left cyclic lateral cyclic So roll bank airplane move aileron stick helicopter rolled banked using cycliclateral cyclic pitch axisthe airplane controlled elevator down elevator causes nose drop up elevator nose rise copter friend cyclic back again now forelaft cyclic longitudinal cyclic Longi tudinal cyclic causes helicopter nose pitch down forward command up aft command remember forward flight right now forward flight helicopter tail rotor similar rudder airplane both control yaw nose aircraft right left Right stick right yaw left stick left yaw airplane note some RC heli copter fliers set control linkage tail rotor right stick gives left nose right tail boom movement like fullscale helicopter Reasons changing tail rotor control will become apparent begin flight training set up normal yaw initially examples flight control similarity aircraft moving forward through air An airplane motion through air called parked tied-downmaybe crashed airplane must moving forward against relative airflow speed sufficient provide lift overcome gravity helicopter may indeed stop move rearward sideways because engine-driven rotating wings provide relative airflow helicopter will lifted off ground engine power rotor pitch set blades rotating against relative wind such way provide enough lift overcome gravity no other forces acting helicopter will hover Now lateral longitudinal cyclic controls may used slide helicopter laterally left right longi tudinally forward rearward tail rotor must used yaw control also keep fuselage spinning around against rotation main rotor Well get back tail rotor later now what cyclic pitch rotor blades Cyclic pitch changes responsible lateral longitudinal movement helicopter An application cyclic control causes pitch blade change opposite other effect blade will oscillate fixed collective pitch setting through positive relative pitch back collective reference pitch relative negative pitch setting back reference collective pitch setting highest lowest relative pitch positions blade will determined position cyclic stick Keep mind blade reaches its highest pitch opposite blade will its lowest pitch excursion blade during revolution like sine wave See Figure 3 Next month will have about cyclic collective pitch rotor head swash plate Dave Chesney Rt 9 Box 621A Greensboro NC 27409 CL BEECHCRAFT/HAUGHT continued page 40 made Instruct helper watch excessive outward yaw unlevel wings will able notice things circles center well another opinion always useful Too much outward yaw causes excessive line tension can see top bottom wings indicates correction needed Both conditions may alleviated relocating leadout guide see tops wings lower guide too much outward yaw move guide forward etc tail heavy model will too difficult control Too much nose weight makes model too sluggish controls too sensitive move pushrod bellcrank down elevator horn etc Level flight boring will find Beech fully aerobatic Loops basic maneuver Most beginners hold fixed amount too much up resulting mushy loop Try varying control throughout loop making big round Lazy eights logical progression inverted flight Begin normal loop neutral ize controls kr way through loop hesitating split second model its back shallow dive give down elevator come around end eight returning level flight Practice lazy eights extending inverted protion until achieve magical first lap inverted flight its merely matter practice Soon youll able tolerate lap upright level flight row Staggerwing SAFE FLYING IS NO ACCIDENT July 1980 117 Deep uselag full cabin b flight capability 112 40 to 60 EngInes igepan dowels lightness movable tail ORGANIZED surfaces actuated movable stubsHee S set 4 sturdy fries hoS OVer fit tail Soar Gull only4 years Vt favorite 8 11 magazirtes different its package clever innovations 4 MAG FILES $495 linkages designsend 5495 plus St 00 postage handtrrrg DON INDUSTRIES P0 BOX 388-K DOVER NH 03820 yourEngine flioo1 G IOw MIUGUE 1/eA Vat Scale Power Usable Power Greater Economy Send 4O & Stamped Addressed Envelope Dealer Inquiry Invited Davis Diesel Development Inc Box 141 Milford CT 06460
