Hobby King Dassault Alpha Fighter EDF-2011/09

pump out products at an
unbelievable rate with
too-good-to-be-true
prices.
Swashbuckling modelers around
the world apparently want to try out
HK personally, and here at MA
we’re no less immune. However, for
HK to be seen on our radar, the
company had to meet our USA
distribution location requirement.
As it turns out, HK now has a
warehouse in the US from which to
order directly and in at least a few
countries, the company is beginning
to open dedicated hobby stores.
Clearly HK is influencing the way
the RC hobby is enjoyed, and it’s
growing. Say what you’d like about the
company’s development methodology,
I like to think that its maturing as a
company and, despite its colorful
reputation, is challenging the market to
be more innovative and compete for our
business.
This is an exclusive review of HK’s
Dassault Alpha Jet PNF, sized for a
90mm-class EDF power system. Don’t
judge this model solely on the
comments briefly mentioned in the
September 2011 67
THE GLOBAL
market has expanded
in all directions in the
last decade. Today it’s
possible to order anything from half
a world away and it can arrive in
roughly the same time it takes
priority mail to travel coast-tocoast.
Mention Hobby King and you’ll
likely hear many stories and charred
evidence might even be offered.
Despite the customer service
learning curve, the China-based
hobby retailer (HK) continues to
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:24 AM Page 67
68 MODEL AVIATION
This size Alpha Jet is available in two air
show color schemes. This one is the
anniversary scheme used by Patrouille de
France.
Red case servos operate in the reverse
direction from the black case 9-gram
mini servos. Hinges are molded into the
control surfaces and provide free
movement with a gapless seal . The
provided linkages are simple, slop-free,
and snap tight.
Right: The factory-installed servo leads
are labeled so that receiver connections
are simple to complete. Spektrum
AR6200 DSM2 and AR6255 DSMX
receivers were tested. The large canopy
hatch is secured with a spring-release
latch and magnets.
Left: The Alpha Jet’s acrylic paint finish is
bright and neatly finished except for on
the canopy. The water-sl ide decal
graphics are applied at the factory. The
EPO foam molding is lightweight and
detail rich.
Left: The simulated scissor-spring nose strut
is internally shock resistant and the directlink
nose wheel steering is effective and
simple.
Below: The preinstalled, shock-absorbing,
retractable landing gear features working
linkages and dedicated servo control.
Minimal adjustment is required, but each
assembly should be rebuilt with threadlock
compound.
Static photos by Michael Ramsey Flight photos by Jay Smith
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:25 AM Page 68
September 2011 69
Specifications
Type: RTF level, RC electric ducted fan
Skill level: Advanced builder/
Intermediate pilot
Wingspan: 40.157 inches (1,020mm)
Length: 54.330 inches (1,380mm)
Weight: 88.185 ounces (2,500 grams)
Wing loading: 10.3 ounces/square
foot (96g/dm2)
Radio: six-channel transmitter and
receiver required
Motor: 1,500 watt brushless inrunner
(included)
EDF: 90mm nylon-fiber unit with sixblade
impeller (included)
ESC: 80A w/3A BEC (included)
Servos (included): 8 x 9g (five
normal, three reverse), 3 x 17g (two
normal, one reverse)
Construction: Expanded Polyolefin
(EPO) foam, composite spars, and
plywood mounts
Finish: Factory applied two color
paint scheme with water slide decals
Battery: 3,700 mAh 22.2V 6S 20C Li-
Poly (required)
Price: $250.95 (USA)
Pluses and Minuses
Motor:Warhead 3545-
1350KV EDF Outrunner Motor
Battery: Turnigy 3.6A 6S 30C
Li-Poly
ESC: Turnigy K-Force 100A
Brushless ESC w/3A SM-BEC
BEC: Castle Creations 10A
CC-BEC
Servos: five HXT900, three
BMS-371, three HK MG
retract servos
Radio: Spektrum DX8
transmitter, Spektrum AR6255
receiver
Flying weight: 80 ounces
(2,270 grams)
Flight Duration: 4-5 minutes
Manufacturer/Distributor:
StarMax/Hobby King USA
www.hobbyking.com
(800) 607-5803
Test Model Details
The Alpha Jet flies light on the wings and doesn’t need to carry a lot of speed on landing.
Pluses and Minuses sidebar. There is much to this product story
including drama, edification, and gratefully, a happily-ever-after
ending.
What I learned is that when a product is sold cheap, the money
saved must be spent in taking the time to thoroughly inspect everything
down to the last screw and wire. Take nothing that was factory
assembled for granted and avoid guessing at the specifications of the
provided electronics. The extra time spent scrutinizing will pay you
back with a more trouble-free model that should better fulfill the
original intent of the retailer.
+•
Available in two air show color schemes
• Finish painted and water-slide decals
applied
• Impressive size for a one-piece EPO foam
model
• Tastefully molded-in details into a durable
semiscale jet
• Strong EDF power system and fun to fly
• Mechanical retracts with shock
absorption
• Full six-channel control with a servo for
every surface -•
Motor required insulation service,
impeller out of balance
• Incomplete or poor factory-placed hard
points and latch mechanisms
• Faulty stock 80A ESC, low-voltage servos
• Minimal and difficult-to-read instruction
manual
• Secondary BEC highly recommended
• Requires complete disassembly and
inspection of the factory-completed
sections
My Alpha Jet model was released and delivered approximately nine
months ago. Although the sample was built quickly, teething problems
along the way kept the project from taking flight. Hobby King worked
with me as well as it could, considering the overnight email
communication variance. Because China is literally half a world away,
instant help isn’t really available unless you’re a forum hunter. HK
does have some website resources, but the service is still in its infancy.
Instead of becoming aggravated, we optimistic modelers call such
product issues a challenge and accept that even an RTF project still
requires patience. Instead of jumping to negative conclusions—or
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:26 AM Page 69
worse, dumping our anxiety on Internet
forums—today’s global modeler should stand
tall, scratch one’s scalp with a calm agitation,
and submit to the situation the question,
“What could I have done differently?”
Although my Alpha Jet was shipped with
some definite factory defects, at least one of
my solutions could have been handled better.
HK’s customer service personnel responded
to my issues to the best of their ability.
For the major electronics failure
encountered on the bench, substitute
equipment took more than six weeks to
restock and ship. Certainly the ironic
frustration of an RTF model waiting on the
bench for parts tried my patience. When the
model did finally fly, the hard work put into
the project paid off with a good-looking
model that flies extremely well.
As I write this, I have nearly 30 flights on
the Alpha Jet. I’m excited to share it with
friends and offer my lessons learned so that
they, too, can get a great deal on a cuttingedge
model and ride out any hurtles
successfully along the way.
Although not famed as a frontline fighter
from Lockheed or Mikoyan, a large number
of Franco-German Alpha Jet multirole aircraft
have been since 1973. The fighter is respected
by dozens of countries in need of a highperformance
attack jet with handling qualities
that allow it to double as a jet trainer. To this
day it remains a venerable asset and has even
entered the private aircraft sector.
I chose this high-powered, electric ductedfan
model of the Alpha Jet from HK because
it seemed to represent a benchmark sample
among the company’s higher-end RTF
selections. HK calls this one “Plug-n-Fly”
because the $250 purchase (+S&H) does not
include the radio or battery. I call it “high
end” because it uses an expensive 6S Li-Poly
battery.
It also includes operational flaps and
retractable tricycle landing gear, which are
complexity points that fit it into an upper-crust
RC classification.
A cushy EPS foam container provides a
luxurious ride for shipment of the Alpha Jet
components. The compartmentalized box
prevents the bagged parts and assemblies
from chaffing against each other.
The foam used to mold the Alpha is
Expanded Polyolefin (EPO), which is the
technical name for what many manufacturers
have named Elapor, Aerocell, and Z-foam.
It’s more resilient than Expanded Polystyrene
(EPS) foam and, depending on how it’s
utilized, it can produce a smoothly finished
model that’s resistant to varying temperatures,
easy to repair, and (the part I like best) is
exceptionally lightweight.
The paint used to decorate the Alpha is
acrylic and can be removed with household
alcohol. Its surface bond can easily fail if
adhesive tape is applied and then peeled off.
Over-sprayed areas where glue is expected to
stick should be cleaned with isopropyl alcohol
then scored with 60-grit sandpaper if you
expect a strong bond.
HK’s Alpha Jet is available in two color
schemes. Shown in this review is a replica of
the lead French-built Alpha Jet E flown by the
demonstration team Patrouille de France. The
other striking color scheme offered is a replica
of the German-built Alpha Jet A used by the
flight display team Asas de Portugal. The
paint is generally well applied, as are the
crisp, opaque water-slide graphics.
As a semiscale model, the shoulder wing
design features inherent stability similar to
that of a high-wing trainer; its anhedral wings
and generously sized stabilizers keep the
aircraft positively neutral without any fancy
mixing or pilot input magic.
Conventional control surfaces make the
model easy to set up using standard linkages
and micro electronics that are light and
reliable. The design is a little tricky because of
the narrow-spaced undercarriage that allows it
to tip if turned on the ground too quickly.
A soft router mat over the building surface
is excellent protection against adding
unwanted weathering to the airframe. Take
the time to closely inspect every part out of its
sealed plastic bag. Tug on the installed servos
and be sure the molded hinging is free from
defects.
The instructions included with the Alpha
are provided with poorly translated English in
a small brochure-like booklet with color
photos that are a strain to interpret. The CG is
spot on and the assembly order is sound, but
otherwise the manual provides little support.
Each servo is neatly flush mounted in
formed pockets with rubber cement and clear
tape that hold well enough but can be relieved
if necessary. The universal servos are custom
wired with the appropriate lead length. The
black and red case servos weigh 9 grams and
offer roughly about 12 inch/ounce of output
power at 4.8-volts. Black servos operate with
a clockwise rotation and the red rotate counter
clockwise. The three retract servos have metal
gears and tug with approximately 18 inch/
ounce of torque at 4.8-volts.
The labeled servo extensions are easy to
organize and reach well into the radio
compartment so that connections to the
receiver can be neatly bound while connected.
To ensure that each servo operates correctly
and is centered, test each one before final
assembly. New servos are a cinch to replace
before the airframe is assembled.
The lower body of the fuselage contains
the EDF system and landing gear. Inspection
of this assembly is crucial; failure of any part
could cost the entire airframe at the field. My
sample included a number of faults, but none
were terminal. Some I caught early; other
problems presented themselves during their
moments of disintegration.
A wise customer should take apart
everything that is screwed into place and tug
hard on everything glued to the airframe. I
assumed the power system installation was
sound and proceeded to test the EDF in the
workshop.
Three momentary slow throttle input
cycles drastically overheated the motor. The
ESC temperature was cool as was the battery.
Vibration from the whirling fan was also
outside comfort levels especially for a power
system expected to rotate at roughly 35,000
rpm and draw 70 amps of current. The
required inspection of the motor proved to be
very revealing, but repairable by an
experienced modeler.
The fan shroud was only spot-glued into
the recesses of the ducts and floated over what
should have been hard points not installed by
the factory. Thread-locking compound would
have been nice to find on the motor screws
(that were loose), and the motor leads
dangerously bent around the sharp edges of
the composite fan shroud. This fan system
was not at all ready to run.
It appeared that the motor lead wires were
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:26 AM Page 70
poorly insulated both inside, next to the motor
windings, and outside. The motor test caused
the provided heat shrink tubing to weld
together. I poured a small amount of epoxy
over the windings and the output leads to
prevent internal chaffing. A twin layer of
heat-shrink tubing properly insulated the
leads and an extra helping of solder
reinforced the 3.5mm bullet connectors.
The six-blade impeller needed a few strips
of correctly located adhesive-backed foil to
balance it dynamically. Once everything was
reassembled using a thread-lock compound,
and plywood plates were glued in for shroud
support, the system was tested again. Happily
there were no issues evident. I also made a
smooth recess notch in the shroud to
comfortably route the motor leads to the ESC
nested inside the internal ducting.
None of the shock-absorbing landing gear
mounts were adequately glued in place.
Before a rubber adhesive such as Welders or
Goop was applied, all of the recoil strut
mechanisms were disassembled and rebuilt
with thread-lock and the correct amount of
torque to the hardware.
Retraction of the gear, although
functional, lacks authority because of the
marginal power of the provided servos.
They do lock positively in the down
position, but in flight they sag somewhat
and the buzz of the servos tells me that
72 MODEL AVIATION
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Y they’re working hard to hold the wheels up.
The oversized canopy hatch, designed to
snap into place, is center secured with
magnets and has a built-in oversized molded
tongue to catch the front end. The catch plate
on my hatch was missing and was critical for
keeping the hatch in place.
Instead of asking HK to replace the part,
a spare GWS landing gear plate was carved
to fit and secured with epoxy as was the
spring-loaded fuselage mounted latch
mechanism that loosened after only a few
uses.
The black-painted interior of the cockpit
can be finish detailed by the user. I kept it
clean, but I regret not adding at least paper
profile pilots to the inside. Rubber adhesive
is best to secure the poorly trimmed and
masked canopy. Cleaning up the outer edges
is easy, and the overspray on the clear
windows can be made bright again by
scrubbing with a soft towel soaked in
alcohol.
Carefully inspect the plywood battery
tray. At the rear there is a minimal amount of
support and the front end is attached with a
minimal amount of rubber cement. The tray
should pull free easily and be much stronger
after it’s reinstalled with epoxy.
The fit of the major parts into the molded
sockets is exceptional. They fit snugly and
are polarized so there’s no guessing about
the location or alignment. Hobby-grade 20-
minute epoxy was used to attach the EPO
sections.
The multipoint composite spars
supporting the wings are permanently
attached to the fuselage. This makes the
model cumbersome to store and transport;
however, I wouldn’t trade the integrity of the
airframe for anything.
The Alpha Jet does not need nose weight,
so consider a lightweight, full-range receiver
such as the Spektrum AR6255, and a
minimal battery such as the Turnigy 3.6
22.2V Li-Poly that has a constant discharge
rating of 30C.
Because no documentation is provided
concerning the electronics, the safe
assumption is that the provided BEC
supplies at best 3-5 amps. I strongly suggest
adding an extra BEC to the power system.
The 11-servo operational load could
overstress the system, so a Castle Creations
10amp CC-BEC was wired in for peace of
mind. Do not set the BEC voltage higher
than 5.0 volts.
Even with inspecting and repairing the
factory assemblies, the Alpha only took
about 10 hours to assemble.
The first flight attempt was interrupted
with a failed ground power test. This time
the ESC overheated and ceased to function
for reasons I can only suspect. A replacement
ESC on hand produced a working motor
again; however, its 6.0-volt BEC setting
overloaded the servos, which caused all but
three of them to terminally fail on the bench.
Admittedly, some of the fault was mine for
this particular stall of the project, but
guessing at the electronic specifications that
were not provided was my only option.
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:26 AM Page 72
Hobby King stepped in and replaced the
ESC with a selection of my choosing, but
could only replace the clockwise direction
servos. Through trial and error, it was found
that Hitec HS-55 and Bluebird BMS-371
micro servos operate in the opposite direction
from the HXT900 micro servo sent as
substitutes, and match the stock
specifications.
The substitute Turnigy K-Force 100A
ESC is overkill for this model, but it added a
level of protection I wanted to ensure many
seasons of flying fun. Its switch mode BEC
has an output of 3 amps at 5.0 volts. The
additional 10A CC-BEC was set at the same
output. Full throttle produces gobs of thrust
with only a 63-amp draw, and every servo
operates with quick response.
To achieve the recommended CG, 2
ounces of ballast was recessed into the tail
cone and concealed with foam and touch-up
paint. With the recommended battery
installed, the flying weight came in more than
8 ounces underweight. Time to go flying!
With no instruction provided regarding
control-surface deflection, using my
Spektrum DX8 transmitter I set full throws at
100% ATV and cushioned them with 30%
exponential on all control surfaces. The low
rates were cut by 50% with no exponential.
The flaps were set with 11° and 35° deflection
for takeoff and landing modes respectively.
Roughly 10% mix of down-elevator in the
landing mode keeps the nose from ballooning
dramatically.
Other than the loud noise the power
system makes, the Alpha Jet flies like a wellmannered
sport airplane. Its mix of delicate
retracts and foam construction is reason for
me to advise against flights from grass fields
unless the turf is very well manicured. I
recommend smooth pavement departures and
arrivals for this EDF.
Even with a small crosswind against the
narrow undercarriage, before throttle is at
30%, the control surfaces are effective and
ground taxiing to a takeoff roll is easy to
manage. Full power isn’t even necessary to
break ground and instead of “popping” off as
many jets do, the Alpha Jet rotates smoothly
and climbs out with authority. At full power
and takeoff flaps the Alpha can climb out at a
75° angle with no sign of instability or ceiling.
Accurate molding and correct center
positioning of the control surfaces allowed the
Alpha to fly neutrally with little trim input.
High rate control response offered
authoritative feel without a sense of
commanding a high-speed model that’s
twitchy. The harmony of the controls was
interpreted as scale feeling with a touch of
reserve surface movement available to safely
and abruptly abort a heading if necessary.
I calculated that about 4 minutes of flight
time would leave a 20% reserve for go-around
and discharge margin. Approximately 50%
power is needed to maintain a steady cruise,
depending on the headwind. Full power need
only be applied for dramatic, low high-speed
passes or for verticals that seem to have no
end or loops that tickle the stratosphere.
Besides the Turnigy 3.6A 22.2V Li-Poly
sent from Hobby King, I used other 6S packs
on hand in order to rack up flight time with
the model. Although the Alpha is
overpowered and lightly loaded, the full
potential of performance won’t be realized
without a fresh, high-quality battery pack. My
older battery samples were not up to the
output delivered by the Turnigy pack. The
Alpha Jet flew with the sickly packs, but I
enjoyed flying a lot more with a healthy
battery.
A lighter 3,200 mAh 25C 6S pack will
improve performance slightly in the climb,
but the minimal inertia of the foam model
isn’t very good at pushing the Alpha any
faster. I’d guess that the top down-line speed
of the Alpha is no more than 100 mph. Fullhouse
composite aircraft in this power class
have been said to fly at 130 mph; however,
they probably lack the low-speed
predictability of this Alpha Jet.
Roll rotation naturally wobbled slightly,
but is crisp. Point rolls that hesitate long
enough for corrective pitch and yaw input is
stunning to witness. Inverted flight takes the
typical amount of down-elevator pressure.
And at full speed, knife-edge flight can be
maintained as long as you please to mix out
the aileron and elevator adverse coupling.
High- and low-speed stall testing revealed
no bad habits. Positive-spin maneuvers are
quite easy to enter and they exit predictably. I
have yet to test inverted spins. In the
intermediate book of Aresti patterns, the
Alpha is adept to perform. Stall turns are
honestly ugly; however, pull and push
recoveries, when seeming little airspeed is
shown, are within the friendly list of manners
the Alpha Jet can deliver.
When the winds are up, flaps aren’t even
necessary. Un-jetlike about the Alpha is its
ability to slow on landing to where the rollout
hardly exists. Using any measure of flaps
makes it possible to carry power through the
landing approach without having much air
speed, all of which benefit the delicate retracts
that have lasted flawlessly through my testing,
thanks to landing procedure diligence and the
handling ease of the Alpha Jet.
The availability and price of the Hobby
King Alpha is a tempting offer. If I had
another sample and applied the inspection
lessons learned, I would likely be flying
with the original electronics. If you’re
looking for a fun and very jetlike
experience, maybe the Alpha Jet can be the
answer to your RC adventure. MA
—Michael Ramsey
[email protected]
Supplemented Equipment List:
Turnigy K-Force brushless ESC
HXT900 micro servo
BMS-371 micro servo
BMS-375MG servo
Hextronik MG-14 servo
Turnigy Li-Poly pack
Sources:
Spektrum RC
www.spektrumrc.com
(800) 338-4639
Castle Creations
(913) 390-6939
www.castlecreations.com
74 MODEL AVIATION
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:27 AM Page 74

pump out products at an
unbelievable rate with
too-good-to-be-true
prices.
Swashbuckling modelers around
the world apparently want to try out
HK personally, and here at MA
we’re no less immune. However, for
HK to be seen on our radar, the
company had to meet our USA
distribution location requirement.
As it turns out, HK now has a
warehouse in the US from which to
order directly and in at least a few
countries, the company is beginning
to open dedicated hobby stores.
Clearly HK is influencing the way
the RC hobby is enjoyed, and it’s
growing. Say what you’d like about the
company’s development methodology,
I like to think that its maturing as a
company and, despite its colorful
reputation, is challenging the market to
be more innovative and compete for our
business.
This is an exclusive review of HK’s
Dassault Alpha Jet PNF, sized for a
90mm-class EDF power system. Don’t
judge this model solely on the
comments briefly mentioned in the
September 2011 67
THE GLOBAL
market has expanded
in all directions in the
last decade. Today it’s
possible to order anything from half
a world away and it can arrive in
roughly the same time it takes
priority mail to travel coast-tocoast.
Mention Hobby King and you’ll
likely hear many stories and charred
evidence might even be offered.
Despite the customer service
learning curve, the China-based
hobby retailer (HK) continues to
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:24 AM Page 67
68 MODEL AVIATION
This size Alpha Jet is available in two air
show color schemes. This one is the
anniversary scheme used by Patrouille de
France.
Red case servos operate in the reverse
direction from the black case 9-gram
mini servos. Hinges are molded into the
control surfaces and provide free
movement with a gapless seal . The
provided linkages are simple, slop-free,
and snap tight.
Right: The factory-installed servo leads
are labeled so that receiver connections
are simple to complete. Spektrum
AR6200 DSM2 and AR6255 DSMX
receivers were tested. The large canopy
hatch is secured with a spring-release
latch and magnets.
Left: The Alpha Jet’s acrylic paint finish is
bright and neatly finished except for on
the canopy. The water-sl ide decal
graphics are applied at the factory. The
EPO foam molding is lightweight and
detail rich.
Left: The simulated scissor-spring nose strut
is internally shock resistant and the directlink
nose wheel steering is effective and
simple.
Below: The preinstalled, shock-absorbing,
retractable landing gear features working
linkages and dedicated servo control.
Minimal adjustment is required, but each
assembly should be rebuilt with threadlock
compound.
Static photos by Michael Ramsey Flight photos by Jay Smith
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:25 AM Page 68
September 2011 69
Specifications
Type: RTF level, RC electric ducted fan
Skill level: Advanced builder/
Intermediate pilot
Wingspan: 40.157 inches (1,020mm)
Length: 54.330 inches (1,380mm)
Weight: 88.185 ounces (2,500 grams)
Wing loading: 10.3 ounces/square
foot (96g/dm2)
Radio: six-channel transmitter and
receiver required
Motor: 1,500 watt brushless inrunner
(included)
EDF: 90mm nylon-fiber unit with sixblade
impeller (included)
ESC: 80A w/3A BEC (included)
Servos (included): 8 x 9g (five
normal, three reverse), 3 x 17g (two
normal, one reverse)
Construction: Expanded Polyolefin
(EPO) foam, composite spars, and
plywood mounts
Finish: Factory applied two color
paint scheme with water slide decals
Battery: 3,700 mAh 22.2V 6S 20C Li-
Poly (required)
Price: $250.95 (USA)
Pluses and Minuses
Motor:Warhead 3545-
1350KV EDF Outrunner Motor
Battery: Turnigy 3.6A 6S 30C
Li-Poly
ESC: Turnigy K-Force 100A
Brushless ESC w/3A SM-BEC
BEC: Castle Creations 10A
CC-BEC
Servos: five HXT900, three
BMS-371, three HK MG
retract servos
Radio: Spektrum DX8
transmitter, Spektrum AR6255
receiver
Flying weight: 80 ounces
(2,270 grams)
Flight Duration: 4-5 minutes
Manufacturer/Distributor:
StarMax/Hobby King USA
www.hobbyking.com
(800) 607-5803
Test Model Details
The Alpha Jet flies light on the wings and doesn’t need to carry a lot of speed on landing.
Pluses and Minuses sidebar. There is much to this product story
including drama, edification, and gratefully, a happily-ever-after
ending.
What I learned is that when a product is sold cheap, the money
saved must be spent in taking the time to thoroughly inspect everything
down to the last screw and wire. Take nothing that was factory
assembled for granted and avoid guessing at the specifications of the
provided electronics. The extra time spent scrutinizing will pay you
back with a more trouble-free model that should better fulfill the
original intent of the retailer.
+•
Available in two air show color schemes
• Finish painted and water-slide decals
applied
• Impressive size for a one-piece EPO foam
model
• Tastefully molded-in details into a durable
semiscale jet
• Strong EDF power system and fun to fly
• Mechanical retracts with shock
absorption
• Full six-channel control with a servo for
every surface -•
Motor required insulation service,
impeller out of balance
• Incomplete or poor factory-placed hard
points and latch mechanisms
• Faulty stock 80A ESC, low-voltage servos
• Minimal and difficult-to-read instruction
manual
• Secondary BEC highly recommended
• Requires complete disassembly and
inspection of the factory-completed
sections
My Alpha Jet model was released and delivered approximately nine
months ago. Although the sample was built quickly, teething problems
along the way kept the project from taking flight. Hobby King worked
with me as well as it could, considering the overnight email
communication variance. Because China is literally half a world away,
instant help isn’t really available unless you’re a forum hunter. HK
does have some website resources, but the service is still in its infancy.
Instead of becoming aggravated, we optimistic modelers call such
product issues a challenge and accept that even an RTF project still
requires patience. Instead of jumping to negative conclusions—or
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:26 AM Page 69
worse, dumping our anxiety on Internet
forums—today’s global modeler should stand
tall, scratch one’s scalp with a calm agitation,
and submit to the situation the question,
“What could I have done differently?”
Although my Alpha Jet was shipped with
some definite factory defects, at least one of
my solutions could have been handled better.
HK’s customer service personnel responded
to my issues to the best of their ability.
For the major electronics failure
encountered on the bench, substitute
equipment took more than six weeks to
restock and ship. Certainly the ironic
frustration of an RTF model waiting on the
bench for parts tried my patience. When the
model did finally fly, the hard work put into
the project paid off with a good-looking
model that flies extremely well.
As I write this, I have nearly 30 flights on
the Alpha Jet. I’m excited to share it with
friends and offer my lessons learned so that
they, too, can get a great deal on a cuttingedge
model and ride out any hurtles
successfully along the way.
Although not famed as a frontline fighter
from Lockheed or Mikoyan, a large number
of Franco-German Alpha Jet multirole aircraft
have been since 1973. The fighter is respected
by dozens of countries in need of a highperformance
attack jet with handling qualities
that allow it to double as a jet trainer. To this
day it remains a venerable asset and has even
entered the private aircraft sector.
I chose this high-powered, electric ductedfan
model of the Alpha Jet from HK because
it seemed to represent a benchmark sample
among the company’s higher-end RTF
selections. HK calls this one “Plug-n-Fly”
because the $250 purchase (+S&H) does not
include the radio or battery. I call it “high
end” because it uses an expensive 6S Li-Poly
battery.
It also includes operational flaps and
retractable tricycle landing gear, which are
complexity points that fit it into an upper-crust
RC classification.
A cushy EPS foam container provides a
luxurious ride for shipment of the Alpha Jet
components. The compartmentalized box
prevents the bagged parts and assemblies
from chaffing against each other.
The foam used to mold the Alpha is
Expanded Polyolefin (EPO), which is the
technical name for what many manufacturers
have named Elapor, Aerocell, and Z-foam.
It’s more resilient than Expanded Polystyrene
(EPS) foam and, depending on how it’s
utilized, it can produce a smoothly finished
model that’s resistant to varying temperatures,
easy to repair, and (the part I like best) is
exceptionally lightweight.
The paint used to decorate the Alpha is
acrylic and can be removed with household
alcohol. Its surface bond can easily fail if
adhesive tape is applied and then peeled off.
Over-sprayed areas where glue is expected to
stick should be cleaned with isopropyl alcohol
then scored with 60-grit sandpaper if you
expect a strong bond.
HK’s Alpha Jet is available in two color
schemes. Shown in this review is a replica of
the lead French-built Alpha Jet E flown by the
demonstration team Patrouille de France. The
other striking color scheme offered is a replica
of the German-built Alpha Jet A used by the
flight display team Asas de Portugal. The
paint is generally well applied, as are the
crisp, opaque water-slide graphics.
As a semiscale model, the shoulder wing
design features inherent stability similar to
that of a high-wing trainer; its anhedral wings
and generously sized stabilizers keep the
aircraft positively neutral without any fancy
mixing or pilot input magic.
Conventional control surfaces make the
model easy to set up using standard linkages
and micro electronics that are light and
reliable. The design is a little tricky because of
the narrow-spaced undercarriage that allows it
to tip if turned on the ground too quickly.
A soft router mat over the building surface
is excellent protection against adding
unwanted weathering to the airframe. Take
the time to closely inspect every part out of its
sealed plastic bag. Tug on the installed servos
and be sure the molded hinging is free from
defects.
The instructions included with the Alpha
are provided with poorly translated English in
a small brochure-like booklet with color
photos that are a strain to interpret. The CG is
spot on and the assembly order is sound, but
otherwise the manual provides little support.
Each servo is neatly flush mounted in
formed pockets with rubber cement and clear
tape that hold well enough but can be relieved
if necessary. The universal servos are custom
wired with the appropriate lead length. The
black and red case servos weigh 9 grams and
offer roughly about 12 inch/ounce of output
power at 4.8-volts. Black servos operate with
a clockwise rotation and the red rotate counter
clockwise. The three retract servos have metal
gears and tug with approximately 18 inch/
ounce of torque at 4.8-volts.
The labeled servo extensions are easy to
organize and reach well into the radio
compartment so that connections to the
receiver can be neatly bound while connected.
To ensure that each servo operates correctly
and is centered, test each one before final
assembly. New servos are a cinch to replace
before the airframe is assembled.
The lower body of the fuselage contains
the EDF system and landing gear. Inspection
of this assembly is crucial; failure of any part
could cost the entire airframe at the field. My
sample included a number of faults, but none
were terminal. Some I caught early; other
problems presented themselves during their
moments of disintegration.
A wise customer should take apart
everything that is screwed into place and tug
hard on everything glued to the airframe. I
assumed the power system installation was
sound and proceeded to test the EDF in the
workshop.
Three momentary slow throttle input
cycles drastically overheated the motor. The
ESC temperature was cool as was the battery.
Vibration from the whirling fan was also
outside comfort levels especially for a power
system expected to rotate at roughly 35,000
rpm and draw 70 amps of current. The
required inspection of the motor proved to be
very revealing, but repairable by an
experienced modeler.
The fan shroud was only spot-glued into
the recesses of the ducts and floated over what
should have been hard points not installed by
the factory. Thread-locking compound would
have been nice to find on the motor screws
(that were loose), and the motor leads
dangerously bent around the sharp edges of
the composite fan shroud. This fan system
was not at all ready to run.
It appeared that the motor lead wires were
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:26 AM Page 70
poorly insulated both inside, next to the motor
windings, and outside. The motor test caused
the provided heat shrink tubing to weld
together. I poured a small amount of epoxy
over the windings and the output leads to
prevent internal chaffing. A twin layer of
heat-shrink tubing properly insulated the
leads and an extra helping of solder
reinforced the 3.5mm bullet connectors.
The six-blade impeller needed a few strips
of correctly located adhesive-backed foil to
balance it dynamically. Once everything was
reassembled using a thread-lock compound,
and plywood plates were glued in for shroud
support, the system was tested again. Happily
there were no issues evident. I also made a
smooth recess notch in the shroud to
comfortably route the motor leads to the ESC
nested inside the internal ducting.
None of the shock-absorbing landing gear
mounts were adequately glued in place.
Before a rubber adhesive such as Welders or
Goop was applied, all of the recoil strut
mechanisms were disassembled and rebuilt
with thread-lock and the correct amount of
torque to the hardware.
Retraction of the gear, although
functional, lacks authority because of the
marginal power of the provided servos.
They do lock positively in the down
position, but in flight they sag somewhat
and the buzz of the servos tells me that
72 MODEL AVIATION
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Y they’re working hard to hold the wheels up.
The oversized canopy hatch, designed to
snap into place, is center secured with
magnets and has a built-in oversized molded
tongue to catch the front end. The catch plate
on my hatch was missing and was critical for
keeping the hatch in place.
Instead of asking HK to replace the part,
a spare GWS landing gear plate was carved
to fit and secured with epoxy as was the
spring-loaded fuselage mounted latch
mechanism that loosened after only a few
uses.
The black-painted interior of the cockpit
can be finish detailed by the user. I kept it
clean, but I regret not adding at least paper
profile pilots to the inside. Rubber adhesive
is best to secure the poorly trimmed and
masked canopy. Cleaning up the outer edges
is easy, and the overspray on the clear
windows can be made bright again by
scrubbing with a soft towel soaked in
alcohol.
Carefully inspect the plywood battery
tray. At the rear there is a minimal amount of
support and the front end is attached with a
minimal amount of rubber cement. The tray
should pull free easily and be much stronger
after it’s reinstalled with epoxy.
The fit of the major parts into the molded
sockets is exceptional. They fit snugly and
are polarized so there’s no guessing about
the location or alignment. Hobby-grade 20-
minute epoxy was used to attach the EPO
sections.
The multipoint composite spars
supporting the wings are permanently
attached to the fuselage. This makes the
model cumbersome to store and transport;
however, I wouldn’t trade the integrity of the
airframe for anything.
The Alpha Jet does not need nose weight,
so consider a lightweight, full-range receiver
such as the Spektrum AR6255, and a
minimal battery such as the Turnigy 3.6
22.2V Li-Poly that has a constant discharge
rating of 30C.
Because no documentation is provided
concerning the electronics, the safe
assumption is that the provided BEC
supplies at best 3-5 amps. I strongly suggest
adding an extra BEC to the power system.
The 11-servo operational load could
overstress the system, so a Castle Creations
10amp CC-BEC was wired in for peace of
mind. Do not set the BEC voltage higher
than 5.0 volts.
Even with inspecting and repairing the
factory assemblies, the Alpha only took
about 10 hours to assemble.
The first flight attempt was interrupted
with a failed ground power test. This time
the ESC overheated and ceased to function
for reasons I can only suspect. A replacement
ESC on hand produced a working motor
again; however, its 6.0-volt BEC setting
overloaded the servos, which caused all but
three of them to terminally fail on the bench.
Admittedly, some of the fault was mine for
this particular stall of the project, but
guessing at the electronic specifications that
were not provided was my only option.
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:26 AM Page 72
Hobby King stepped in and replaced the
ESC with a selection of my choosing, but
could only replace the clockwise direction
servos. Through trial and error, it was found
that Hitec HS-55 and Bluebird BMS-371
micro servos operate in the opposite direction
from the HXT900 micro servo sent as
substitutes, and match the stock
specifications.
The substitute Turnigy K-Force 100A
ESC is overkill for this model, but it added a
level of protection I wanted to ensure many
seasons of flying fun. Its switch mode BEC
has an output of 3 amps at 5.0 volts. The
additional 10A CC-BEC was set at the same
output. Full throttle produces gobs of thrust
with only a 63-amp draw, and every servo
operates with quick response.
To achieve the recommended CG, 2
ounces of ballast was recessed into the tail
cone and concealed with foam and touch-up
paint. With the recommended battery
installed, the flying weight came in more than
8 ounces underweight. Time to go flying!
With no instruction provided regarding
control-surface deflection, using my
Spektrum DX8 transmitter I set full throws at
100% ATV and cushioned them with 30%
exponential on all control surfaces. The low
rates were cut by 50% with no exponential.
The flaps were set with 11° and 35° deflection
for takeoff and landing modes respectively.
Roughly 10% mix of down-elevator in the
landing mode keeps the nose from ballooning
dramatically.
Other than the loud noise the power
system makes, the Alpha Jet flies like a wellmannered
sport airplane. Its mix of delicate
retracts and foam construction is reason for
me to advise against flights from grass fields
unless the turf is very well manicured. I
recommend smooth pavement departures and
arrivals for this EDF.
Even with a small crosswind against the
narrow undercarriage, before throttle is at
30%, the control surfaces are effective and
ground taxiing to a takeoff roll is easy to
manage. Full power isn’t even necessary to
break ground and instead of “popping” off as
many jets do, the Alpha Jet rotates smoothly
and climbs out with authority. At full power
and takeoff flaps the Alpha can climb out at a
75° angle with no sign of instability or ceiling.
Accurate molding and correct center
positioning of the control surfaces allowed the
Alpha to fly neutrally with little trim input.
High rate control response offered
authoritative feel without a sense of
commanding a high-speed model that’s
twitchy. The harmony of the controls was
interpreted as scale feeling with a touch of
reserve surface movement available to safely
and abruptly abort a heading if necessary.
I calculated that about 4 minutes of flight
time would leave a 20% reserve for go-around
and discharge margin. Approximately 50%
power is needed to maintain a steady cruise,
depending on the headwind. Full power need
only be applied for dramatic, low high-speed
passes or for verticals that seem to have no
end or loops that tickle the stratosphere.
Besides the Turnigy 3.6A 22.2V Li-Poly
sent from Hobby King, I used other 6S packs
on hand in order to rack up flight time with
the model. Although the Alpha is
overpowered and lightly loaded, the full
potential of performance won’t be realized
without a fresh, high-quality battery pack. My
older battery samples were not up to the
output delivered by the Turnigy pack. The
Alpha Jet flew with the sickly packs, but I
enjoyed flying a lot more with a healthy
battery.
A lighter 3,200 mAh 25C 6S pack will
improve performance slightly in the climb,
but the minimal inertia of the foam model
isn’t very good at pushing the Alpha any
faster. I’d guess that the top down-line speed
of the Alpha is no more than 100 mph. Fullhouse
composite aircraft in this power class
have been said to fly at 130 mph; however,
they probably lack the low-speed
predictability of this Alpha Jet.
Roll rotation naturally wobbled slightly,
but is crisp. Point rolls that hesitate long
enough for corrective pitch and yaw input is
stunning to witness. Inverted flight takes the
typical amount of down-elevator pressure.
And at full speed, knife-edge flight can be
maintained as long as you please to mix out
the aileron and elevator adverse coupling.
High- and low-speed stall testing revealed
no bad habits. Positive-spin maneuvers are
quite easy to enter and they exit predictably. I
have yet to test inverted spins. In the
intermediate book of Aresti patterns, the
Alpha is adept to perform. Stall turns are
honestly ugly; however, pull and push
recoveries, when seeming little airspeed is
shown, are within the friendly list of manners
the Alpha Jet can deliver.
When the winds are up, flaps aren’t even
necessary. Un-jetlike about the Alpha is its
ability to slow on landing to where the rollout
hardly exists. Using any measure of flaps
makes it possible to carry power through the
landing approach without having much air
speed, all of which benefit the delicate retracts
that have lasted flawlessly through my testing,
thanks to landing procedure diligence and the
handling ease of the Alpha Jet.
The availability and price of the Hobby
King Alpha is a tempting offer. If I had
another sample and applied the inspection
lessons learned, I would likely be flying
with the original electronics. If you’re
looking for a fun and very jetlike
experience, maybe the Alpha Jet can be the
answer to your RC adventure. MA
—Michael Ramsey
[email protected]
Supplemented Equipment List:
Turnigy K-Force brushless ESC
HXT900 micro servo
BMS-371 micro servo
BMS-375MG servo
Hextronik MG-14 servo
Turnigy Li-Poly pack
Sources:
Spektrum RC
www.spektrumrc.com
(800) 338-4639
Castle Creations
(913) 390-6939
www.castlecreations.com
74 MODEL AVIATION
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:27 AM Page 74

pump out products at an
unbelievable rate with
too-good-to-be-true
prices.
Swashbuckling modelers around
the world apparently want to try out
HK personally, and here at MA
we’re no less immune. However, for
HK to be seen on our radar, the
company had to meet our USA
distribution location requirement.
As it turns out, HK now has a
warehouse in the US from which to
order directly and in at least a few
countries, the company is beginning
to open dedicated hobby stores.
Clearly HK is influencing the way
the RC hobby is enjoyed, and it’s
growing. Say what you’d like about the
company’s development methodology,
I like to think that its maturing as a
company and, despite its colorful
reputation, is challenging the market to
be more innovative and compete for our
business.
This is an exclusive review of HK’s
Dassault Alpha Jet PNF, sized for a
90mm-class EDF power system. Don’t
judge this model solely on the
comments briefly mentioned in the
September 2011 67
THE GLOBAL
market has expanded
in all directions in the
last decade. Today it’s
possible to order anything from half
a world away and it can arrive in
roughly the same time it takes
priority mail to travel coast-tocoast.
Mention Hobby King and you’ll
likely hear many stories and charred
evidence might even be offered.
Despite the customer service
learning curve, the China-based
hobby retailer (HK) continues to
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:24 AM Page 67
68 MODEL AVIATION
This size Alpha Jet is available in two air
show color schemes. This one is the
anniversary scheme used by Patrouille de
France.
Red case servos operate in the reverse
direction from the black case 9-gram
mini servos. Hinges are molded into the
control surfaces and provide free
movement with a gapless seal . The
provided linkages are simple, slop-free,
and snap tight.
Right: The factory-installed servo leads
are labeled so that receiver connections
are simple to complete. Spektrum
AR6200 DSM2 and AR6255 DSMX
receivers were tested. The large canopy
hatch is secured with a spring-release
latch and magnets.
Left: The Alpha Jet’s acrylic paint finish is
bright and neatly finished except for on
the canopy. The water-sl ide decal
graphics are applied at the factory. The
EPO foam molding is lightweight and
detail rich.
Left: The simulated scissor-spring nose strut
is internally shock resistant and the directlink
nose wheel steering is effective and
simple.
Below: The preinstalled, shock-absorbing,
retractable landing gear features working
linkages and dedicated servo control.
Minimal adjustment is required, but each
assembly should be rebuilt with threadlock
compound.
Static photos by Michael Ramsey Flight photos by Jay Smith
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:25 AM Page 68
September 2011 69
Specifications
Type: RTF level, RC electric ducted fan
Skill level: Advanced builder/
Intermediate pilot
Wingspan: 40.157 inches (1,020mm)
Length: 54.330 inches (1,380mm)
Weight: 88.185 ounces (2,500 grams)
Wing loading: 10.3 ounces/square
foot (96g/dm2)
Radio: six-channel transmitter and
receiver required
Motor: 1,500 watt brushless inrunner
(included)
EDF: 90mm nylon-fiber unit with sixblade
impeller (included)
ESC: 80A w/3A BEC (included)
Servos (included): 8 x 9g (five
normal, three reverse), 3 x 17g (two
normal, one reverse)
Construction: Expanded Polyolefin
(EPO) foam, composite spars, and
plywood mounts
Finish: Factory applied two color
paint scheme with water slide decals
Battery: 3,700 mAh 22.2V 6S 20C Li-
Poly (required)
Price: $250.95 (USA)
Pluses and Minuses
Motor:Warhead 3545-
1350KV EDF Outrunner Motor
Battery: Turnigy 3.6A 6S 30C
Li-Poly
ESC: Turnigy K-Force 100A
Brushless ESC w/3A SM-BEC
BEC: Castle Creations 10A
CC-BEC
Servos: five HXT900, three
BMS-371, three HK MG
retract servos
Radio: Spektrum DX8
transmitter, Spektrum AR6255
receiver
Flying weight: 80 ounces
(2,270 grams)
Flight Duration: 4-5 minutes
Manufacturer/Distributor:
StarMax/Hobby King USA
www.hobbyking.com
(800) 607-5803
Test Model Details
The Alpha Jet flies light on the wings and doesn’t need to carry a lot of speed on landing.
Pluses and Minuses sidebar. There is much to this product story
including drama, edification, and gratefully, a happily-ever-after
ending.
What I learned is that when a product is sold cheap, the money
saved must be spent in taking the time to thoroughly inspect everything
down to the last screw and wire. Take nothing that was factory
assembled for granted and avoid guessing at the specifications of the
provided electronics. The extra time spent scrutinizing will pay you
back with a more trouble-free model that should better fulfill the
original intent of the retailer.
+•
Available in two air show color schemes
• Finish painted and water-slide decals
applied
• Impressive size for a one-piece EPO foam
model
• Tastefully molded-in details into a durable
semiscale jet
• Strong EDF power system and fun to fly
• Mechanical retracts with shock
absorption
• Full six-channel control with a servo for
every surface -•
Motor required insulation service,
impeller out of balance
• Incomplete or poor factory-placed hard
points and latch mechanisms
• Faulty stock 80A ESC, low-voltage servos
• Minimal and difficult-to-read instruction
manual
• Secondary BEC highly recommended
• Requires complete disassembly and
inspection of the factory-completed
sections
My Alpha Jet model was released and delivered approximately nine
months ago. Although the sample was built quickly, teething problems
along the way kept the project from taking flight. Hobby King worked
with me as well as it could, considering the overnight email
communication variance. Because China is literally half a world away,
instant help isn’t really available unless you’re a forum hunter. HK
does have some website resources, but the service is still in its infancy.
Instead of becoming aggravated, we optimistic modelers call such
product issues a challenge and accept that even an RTF project still
requires patience. Instead of jumping to negative conclusions—or
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:26 AM Page 69
worse, dumping our anxiety on Internet
forums—today’s global modeler should stand
tall, scratch one’s scalp with a calm agitation,
and submit to the situation the question,
“What could I have done differently?”
Although my Alpha Jet was shipped with
some definite factory defects, at least one of
my solutions could have been handled better.
HK’s customer service personnel responded
to my issues to the best of their ability.
For the major electronics failure
encountered on the bench, substitute
equipment took more than six weeks to
restock and ship. Certainly the ironic
frustration of an RTF model waiting on the
bench for parts tried my patience. When the
model did finally fly, the hard work put into
the project paid off with a good-looking
model that flies extremely well.
As I write this, I have nearly 30 flights on
the Alpha Jet. I’m excited to share it with
friends and offer my lessons learned so that
they, too, can get a great deal on a cuttingedge
model and ride out any hurtles
successfully along the way.
Although not famed as a frontline fighter
from Lockheed or Mikoyan, a large number
of Franco-German Alpha Jet multirole aircraft
have been since 1973. The fighter is respected
by dozens of countries in need of a highperformance
attack jet with handling qualities
that allow it to double as a jet trainer. To this
day it remains a venerable asset and has even
entered the private aircraft sector.
I chose this high-powered, electric ductedfan
model of the Alpha Jet from HK because
it seemed to represent a benchmark sample
among the company’s higher-end RTF
selections. HK calls this one “Plug-n-Fly”
because the $250 purchase (+S&H) does not
include the radio or battery. I call it “high
end” because it uses an expensive 6S Li-Poly
battery.
It also includes operational flaps and
retractable tricycle landing gear, which are
complexity points that fit it into an upper-crust
RC classification.
A cushy EPS foam container provides a
luxurious ride for shipment of the Alpha Jet
components. The compartmentalized box
prevents the bagged parts and assemblies
from chaffing against each other.
The foam used to mold the Alpha is
Expanded Polyolefin (EPO), which is the
technical name for what many manufacturers
have named Elapor, Aerocell, and Z-foam.
It’s more resilient than Expanded Polystyrene
(EPS) foam and, depending on how it’s
utilized, it can produce a smoothly finished
model that’s resistant to varying temperatures,
easy to repair, and (the part I like best) is
exceptionally lightweight.
The paint used to decorate the Alpha is
acrylic and can be removed with household
alcohol. Its surface bond can easily fail if
adhesive tape is applied and then peeled off.
Over-sprayed areas where glue is expected to
stick should be cleaned with isopropyl alcohol
then scored with 60-grit sandpaper if you
expect a strong bond.
HK’s Alpha Jet is available in two color
schemes. Shown in this review is a replica of
the lead French-built Alpha Jet E flown by the
demonstration team Patrouille de France. The
other striking color scheme offered is a replica
of the German-built Alpha Jet A used by the
flight display team Asas de Portugal. The
paint is generally well applied, as are the
crisp, opaque water-slide graphics.
As a semiscale model, the shoulder wing
design features inherent stability similar to
that of a high-wing trainer; its anhedral wings
and generously sized stabilizers keep the
aircraft positively neutral without any fancy
mixing or pilot input magic.
Conventional control surfaces make the
model easy to set up using standard linkages
and micro electronics that are light and
reliable. The design is a little tricky because of
the narrow-spaced undercarriage that allows it
to tip if turned on the ground too quickly.
A soft router mat over the building surface
is excellent protection against adding
unwanted weathering to the airframe. Take
the time to closely inspect every part out of its
sealed plastic bag. Tug on the installed servos
and be sure the molded hinging is free from
defects.
The instructions included with the Alpha
are provided with poorly translated English in
a small brochure-like booklet with color
photos that are a strain to interpret. The CG is
spot on and the assembly order is sound, but
otherwise the manual provides little support.
Each servo is neatly flush mounted in
formed pockets with rubber cement and clear
tape that hold well enough but can be relieved
if necessary. The universal servos are custom
wired with the appropriate lead length. The
black and red case servos weigh 9 grams and
offer roughly about 12 inch/ounce of output
power at 4.8-volts. Black servos operate with
a clockwise rotation and the red rotate counter
clockwise. The three retract servos have metal
gears and tug with approximately 18 inch/
ounce of torque at 4.8-volts.
The labeled servo extensions are easy to
organize and reach well into the radio
compartment so that connections to the
receiver can be neatly bound while connected.
To ensure that each servo operates correctly
and is centered, test each one before final
assembly. New servos are a cinch to replace
before the airframe is assembled.
The lower body of the fuselage contains
the EDF system and landing gear. Inspection
of this assembly is crucial; failure of any part
could cost the entire airframe at the field. My
sample included a number of faults, but none
were terminal. Some I caught early; other
problems presented themselves during their
moments of disintegration.
A wise customer should take apart
everything that is screwed into place and tug
hard on everything glued to the airframe. I
assumed the power system installation was
sound and proceeded to test the EDF in the
workshop.
Three momentary slow throttle input
cycles drastically overheated the motor. The
ESC temperature was cool as was the battery.
Vibration from the whirling fan was also
outside comfort levels especially for a power
system expected to rotate at roughly 35,000
rpm and draw 70 amps of current. The
required inspection of the motor proved to be
very revealing, but repairable by an
experienced modeler.
The fan shroud was only spot-glued into
the recesses of the ducts and floated over what
should have been hard points not installed by
the factory. Thread-locking compound would
have been nice to find on the motor screws
(that were loose), and the motor leads
dangerously bent around the sharp edges of
the composite fan shroud. This fan system
was not at all ready to run.
It appeared that the motor lead wires were
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:26 AM Page 70
poorly insulated both inside, next to the motor
windings, and outside. The motor test caused
the provided heat shrink tubing to weld
together. I poured a small amount of epoxy
over the windings and the output leads to
prevent internal chaffing. A twin layer of
heat-shrink tubing properly insulated the
leads and an extra helping of solder
reinforced the 3.5mm bullet connectors.
The six-blade impeller needed a few strips
of correctly located adhesive-backed foil to
balance it dynamically. Once everything was
reassembled using a thread-lock compound,
and plywood plates were glued in for shroud
support, the system was tested again. Happily
there were no issues evident. I also made a
smooth recess notch in the shroud to
comfortably route the motor leads to the ESC
nested inside the internal ducting.
None of the shock-absorbing landing gear
mounts were adequately glued in place.
Before a rubber adhesive such as Welders or
Goop was applied, all of the recoil strut
mechanisms were disassembled and rebuilt
with thread-lock and the correct amount of
torque to the hardware.
Retraction of the gear, although
functional, lacks authority because of the
marginal power of the provided servos.
They do lock positively in the down
position, but in flight they sag somewhat
and the buzz of the servos tells me that
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Y they’re working hard to hold the wheels up.
The oversized canopy hatch, designed to
snap into place, is center secured with
magnets and has a built-in oversized molded
tongue to catch the front end. The catch plate
on my hatch was missing and was critical for
keeping the hatch in place.
Instead of asking HK to replace the part,
a spare GWS landing gear plate was carved
to fit and secured with epoxy as was the
spring-loaded fuselage mounted latch
mechanism that loosened after only a few
uses.
The black-painted interior of the cockpit
can be finish detailed by the user. I kept it
clean, but I regret not adding at least paper
profile pilots to the inside. Rubber adhesive
is best to secure the poorly trimmed and
masked canopy. Cleaning up the outer edges
is easy, and the overspray on the clear
windows can be made bright again by
scrubbing with a soft towel soaked in
alcohol.
Carefully inspect the plywood battery
tray. At the rear there is a minimal amount of
support and the front end is attached with a
minimal amount of rubber cement. The tray
should pull free easily and be much stronger
after it’s reinstalled with epoxy.
The fit of the major parts into the molded
sockets is exceptional. They fit snugly and
are polarized so there’s no guessing about
the location or alignment. Hobby-grade 20-
minute epoxy was used to attach the EPO
sections.
The multipoint composite spars
supporting the wings are permanently
attached to the fuselage. This makes the
model cumbersome to store and transport;
however, I wouldn’t trade the integrity of the
airframe for anything.
The Alpha Jet does not need nose weight,
so consider a lightweight, full-range receiver
such as the Spektrum AR6255, and a
minimal battery such as the Turnigy 3.6
22.2V Li-Poly that has a constant discharge
rating of 30C.
Because no documentation is provided
concerning the electronics, the safe
assumption is that the provided BEC
supplies at best 3-5 amps. I strongly suggest
adding an extra BEC to the power system.
The 11-servo operational load could
overstress the system, so a Castle Creations
10amp CC-BEC was wired in for peace of
mind. Do not set the BEC voltage higher
than 5.0 volts.
Even with inspecting and repairing the
factory assemblies, the Alpha only took
about 10 hours to assemble.
The first flight attempt was interrupted
with a failed ground power test. This time
the ESC overheated and ceased to function
for reasons I can only suspect. A replacement
ESC on hand produced a working motor
again; however, its 6.0-volt BEC setting
overloaded the servos, which caused all but
three of them to terminally fail on the bench.
Admittedly, some of the fault was mine for
this particular stall of the project, but
guessing at the electronic specifications that
were not provided was my only option.
09sig3.QXD_00MSTRPG.QXD 7/22/11 10:26 AM Page 72
Hobby King stepped in and replaced the
ESC with a selection of my choosing, but
could only replace the clockwise direction
servos. Through trial and error, it was found
that Hitec HS-55 and Bluebird BMS-371
micro servos operate in the opposite direction
from the HXT900 micro servo sent as
substitutes, and match the stock
specifications.
The substitute Turnigy K-Force 100A
ESC is overkill for this model, but it added a
level of protection I wanted to ensure many
seasons of flying fun. Its switch mode BEC
has an output of 3 amps at 5.0 volts. The
additional 10A CC-BEC was set at the same
output. Full throttle produces gobs of thrust
with only a 63-amp draw, and every servo
operates with quick response.
To achieve the recommended CG, 2
ounces of ballast was recessed into the tail
cone and concealed with foam and touch-up
paint. With the recommended battery
installed, the flying weight came in more than
8 ounces underweight. Time to go flying!
With no instruction provided regarding
control-surface deflection, using my
Spektrum DX8 transmitter I set full throws at
100% ATV and cushioned them with 30%
exponential on all control surfaces. The low
rates were cut by 50% with no exponential.
The flaps were set with 11° and 35° deflection
for takeoff and landing modes respectively.
Roughly 10% mix of down-elevator in the
landing mode keeps the nose from ballooning
dramatically.
Other than the loud noise the power
system makes, the Alpha Jet flies like a wellmannered
sport airplane. Its mix of delicate
retracts and foam construction is reason for
me to advise against flights from grass fields
unless the turf is very well manicured. I
recommend smooth pavement departures and
arrivals for this EDF.
Even with a small crosswind against the
narrow undercarriage, before throttle is at
30%, the control surfaces are effective and
ground taxiing to a takeoff roll is easy to
manage. Full power isn’t even necessary to
break ground and instead of “popping” off as
many jets do, the Alpha Jet rotates smoothly
and climbs out with authority. At full power
and takeoff flaps the Alpha can climb out at a
75° angle with no sign of instability or ceiling.
Accurate molding and correct center
positioning of the control surfaces allowed the
Alpha to fly neutrally with little trim input.
High rate control response offered
authoritative feel without a sense of
commanding a high-speed model that’s
twitchy. The harmony of the controls was
interpreted as scale feeling with a touch of
reserve surface movement available to safely
and abruptly abort a heading if necessary.
I calculated that about 4 minutes of flight
time would leave a 20% reserve for go-around
and discharge margin. Approximately 50%
power is needed to maintain a steady cruise,
depending on the headwind. Full power need
only be applied for dramatic, low high-speed
passes or for verticals that seem to have no
end or loops that tickle the stratosphere.
Besides the Turnigy 3.6A 22.2V Li-Poly
sent from Hobby King, I used other 6S packs
on hand in order to rack up flight time with
the model. Although the Alpha is
overpowered and lightly loaded, the full
potential of performance won’t be realized
without a fresh, high-quality battery pack. My
older battery samples were not up to the
output delivered by the Turnigy pack. The
Alpha Jet flew with the sickly packs, but I
enjoyed flying a lot more with a healthy
battery.
A lighter 3,200 mAh 25C 6S pack will
improve performance slightly in the climb,
but the minimal inertia of the foam model
isn’t very good at pushing the Alpha any
faster. I’d guess that the top down-line speed
of the Alpha is no more than 100 mph. Fullhouse
composite aircraft in this power class
have been said to fly at 130 mph; however,
they probably lack the low-speed
predictability of this Alpha Jet.
Roll rotation naturally wobbled slightly,
but is crisp. Point rolls that hesitate long
enough for corrective pitch and yaw input is
stunning to witness. Inverted flight takes the
typical amount of down-elevator pressure.
And at full speed, knife-edge flight can be
maintained as long as you please to mix out
the aileron and elevator adverse coupling.
High- and low-speed stall testing revealed
no bad habits. Positive-spin maneuvers are
quite easy to enter and they exit predictably. I
have yet to test inverted spins. In the
intermediate book of Aresti patterns, the
Alpha is adept to perform. Stall turns are
honestly ugly; however, pull and push
recoveries, when seeming little airspeed is
shown, are within the friendly list of manners
the Alpha Jet can deliver.
When the winds are up, flaps aren’t even
necessary. Un-jetlike about the Alpha is its
ability to slow on landing to where the rollout
hardly exists. Using any measure of flaps
makes it possible to carry power through the
landing approach without having much air
speed, all of which benefit the delicate retracts
that have lasted flawlessly through my testing,
thanks to landing procedure diligence and the
handling ease of the Alpha Jet.
The availability and price of the Hobby
King Alpha is a tempting offer. If I had
another sample and applied the inspection
lessons learned, I would likely be flying
with the original electronics. If you’re
looking for a fun and very jetlike
experience, maybe the Alpha Jet can be the
answer to your RC adventure. MA
—Michael Ramsey
[email protected]
Supplemented Equipment List:
Turnigy K-Force brushless ESC
HXT900 micro servo
BMS-371 micro servo
BMS-375MG servo
Hextronik MG-14 servo
Turnigy Li-Poly pack
Sources:
Spektrum RC
www.spektrumrc.com
(800) 338-4639
Castle Creations
(913) 390-6939
www.castlecreations.com
74 MODEL AVIATION
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