Plane Talk: E-flite F-15 Eagle ARF - 2009/09

THE FULL-SCALE McDonnell Douglas
F-15 Eagle is one of the most capable
fighters in the world. Designed to be an
all-weather tactical fighter, to gain and
maintain air superiority in aerial combat, it
first flew in July 1972. It entered US
service in 1976.
The F-15 achieves its maneuverability
with a combination of low wing loading and
high thrust-to-weight ratio, as equipped with
two Pratt & Whitney F-100 turbofan
engines (29,000-pound-thrust class with
afterburning). It flies at speeds of 1,875 mph
(Mach 2.5 plus). This is the first American
fighter with an engine thrust totaling more
than its normal weight, allowing it to
accelerate while in a vertical climb.
As designed, the F-15 was intended for
a multitude of missions. And with a price
tag of roughly $30 million, chances are
that one can only dream of piloting this
world-class fighter.
But E-flite has come to the rescue! Its
semiscale model of the Eagle was
designed around a pair of Park 420 ductedfan
motors, keeping in mind design
features that made the full-scale F-15 such
a success (low wing loading, high thrustto-
weight ratio).
The E-flite version is made from
injection-molded EPS foam, keeping it
lightweight. That’s not a bad idea,
considering that twice the amount of
electronics goes into it. And if the builder
decides to install the factory-supplied
retractable landing gear, three additional
servos and Y harness are needed.
When I opened the box and inspected all
of the F-15 Eagle’s components, I saw
several notable features. The model came
prepainted with the great looks of the
Edwards Air Force Base Safety Chase
paint scheme. Almost all decals were
applied at the factory, and all flight control
surfaces were prehinged. The wings had a
preinstalled carbon wing spar, to increase
wing strength and rigidity.
Fixed and retractable landing gear were
included; I chose to go with retracts. It’s
icing on the cake to watch the gear go up
on a flyby, adding to the scale appearance.
Compared to other models I have built,
I was surprised to see that the F-15 had
such a low parts count. Having never built
or flown a jet of any kind, I had built up
something more complex in mind.
After briefly reading through the
manual, all reservations were laid to rest.
The instructions were well written, with a
step-by-step list of required parts, required
tools and adhesives, and pictures to show
intended results or the finished look.
On occasion, a special note for a
particular step was included to ease the
assembly process. One I particularly liked,
at the beginning of the retract installation,
was an explanation of how to set up
programming for retracts using the DX7
transmitter. This was extremely helpful,
since I had never encountered the need for
this application.
Construction: The assembly process
began with stabilizer installation. Before
permanently installing the electronics in
any project, it is a good practice to lay out and
mock up all of the electronic components.
There are many benefits to making this
one of the first steps in any build; centering
the servos may be one of the most
important. Nothing is more frustrating than
trying to “gracefully” dig a servo out of a
recessed pocket after gluing it in place.
Yes, this is from experience.
I have also learned, as have many other
modelers, that not all servos are created
equal. Some do not mechanically center as
well as others. Putting them in different
channel assignments with different control
horns to get the best result is easier on the
bench without the aircraft involved.
With the servos in their respective
positions, I marked them with a small
piece of tape to remind me of their
placement later. Fortunately, the Eagle has
only two servos (ailerons) in a recessed
pocket that require centering before
installation. With the mock-up done,
installing stabilizer servos is a snap.
Installing the stabilizers brought up a
bit of concern. I found that the stabilizer
control-rod bushings in the fuselage are
not parallel/perpendicular to each other,
because the tail sections’ angles are
different. Installing the stabilizers without
binding took finesse.
The simple solution I came up with was
to insert a drill bit of the same size,
carefully hand-drill the bushings to allow
for better alignment, micro-polish the
stabilizer control rods, and apply graphite
lubricant to both the bushings and the rod.
Then the recommended E-flite S75 servos
were able to properly manage the control
surface without excessive resistance.
When installing the stabilator on each
control rod, you will dent the tail to access
the setscrew, leaving unsightly indentations
on each side. You could make a small
incision to allow for Allen wrench
clearance and glue it afterward, leaving
much less damage.
It was time to put together and install the
motor/fan units. Before assembling both
units, I thought it would be best to balance
both impellers after the initial motor test
run. It proved to be time well spent. I was
impressed with the rpm! Take care not to
squeeze the fan housing while running up
the motor; the housing can easily be
distorted, causing unwanted grinding.
After gaining proper clearance between
the impeller and housing, I mounted the
ducted-fan units in the fuselage. Running
up the motors once more made it apparent
that the impeller clearance had changed.
After a bit more sanding here and there, all
was well. Don’t run motors inside; the
decibel level might anger those who live
with you!
Installing the retractable landing gear
proved to be a bit more time-consuming
than anticipated. The nose gear went in with
no hitches whatsoever, but the main gear
retracts did not fit properly in the fuselage.
Referencing the manual’s pictures, the
spring portion of the gear-strut wires were
wrapped in the opposite direction, causing
them to rest outside of the molded channel.
There was also contact with the actuator
arm.
To correct both of those concerns, I
turned the gear-strut wires to improve
clearance and moved the wires more
inboard, and then I clamped the spring
portion in a vise and tweaked them a little
to readjust the toe out of the wheels.
A small portion forward of the wingalignment
tab needed to be removed so
that the gear would retract completely. I
installed the S75 servos in the fuselage
lower than shown in the manual. Then I
put the servo control arm on with the
pushrod connector close to the fuselage,
which improved the geometry of the
actuator arm and control rod, keeping them
more parallel with the fuselage throughout
the range of movement.
With the aileron servos installed, and
main wing panels attached to the fuselage,
completing the electronics was the last
step before radio setup. I found that
keeping the servo wires and Y harness neat
and tidy inside the battery compartment
aids in battery access.
To achieve that, I used a wire loom that
allowed me to put three leads through
without removing the connector ends. The
result gave the wiring a clean look;
however, I did have to notch the canopy in
the rear to improve the fit.
After setting the control throws to the
recommended rates, glue the vertical
stabilizers in place. Although I had the
urge to install them early, it was a good
idea to save them for last. I lost count of
the number of times I had to flip the F-15
during programming.
Having completed the programming, a
quick balance check (with retracts up) was
all that remained before the maiden flight.
Only 1/2 ounce in the nose was needed to
obtain the factory-recommended balance
point of 33/8 inches from the LE.
Flying: After performing preflight checks,
all systems were go! The Eagle taxied
down the flightline nicely. Powering up to
full throttle, it wasted no time shortening
the runway.
With slight up-elevator, the climbout
was smooth and predictable. Once the
model was airborne, it was apparent that
half throttle is sufficient to perform most
maneuvers of which the F-15 is capable—
unless you feel the need to show off with a
screaming flyby.
During the initial flight, I found myself
pushing up on the elevator while the jet
was inverted. The recommended balance
point left the F-15 a bit nose-heavy for my
liking.
After removing the 1/2 ounce from the
nose that I had installed, the Eagle was
more neutral during the second flight.
Switching to high rates, it was more
responsive, with no unwanted characteristics.
This model performs basic aerobatics
such as loops, rolls, and Split “S”
maneuvers with little to no effort. During
a power stall, I found that I was at the end
of the battery’s capacity, causing one of
the ducted-fan units to shut down. The F-
15 continued to be manageable, even with
the loss of a motor. That proved that you
can make it home on one engine.
Before I could set up approach for
landing, the second motor quit, leaving the
F-15 dead-stick. It was still controllable
with the use of full up-elevator to manage
the descent.
Overall, the E-flite F-15 Eagle is
enjoyable for the ambitious pilot who is
looking to take off with his or her first jet
model. MA
Shawn Rubush
[email protected]
Manufacturer/Distributor:
E-flite/Horizon Hobby
4105 Fieldstone Rd.
Champaign IL 61822
(877) 504-0233
www.e-fliterc.com
Other Published Reviews:
Hobby Merchandiser: July 2008
RC Sport Flyer: October 2008
R/C Report: October 2008

THE FULL-SCALE McDonnell Douglas
F-15 Eagle is one of the most capable
fighters in the world. Designed to be an
all-weather tactical fighter, to gain and
maintain air superiority in aerial combat, it
first flew in July 1972. It entered US
service in 1976.
The F-15 achieves its maneuverability
with a combination of low wing loading and
high thrust-to-weight ratio, as equipped with
two Pratt & Whitney F-100 turbofan
engines (29,000-pound-thrust class with
afterburning). It flies at speeds of 1,875 mph
(Mach 2.5 plus). This is the first American
fighter with an engine thrust totaling more
than its normal weight, allowing it to
accelerate while in a vertical climb.
As designed, the F-15 was intended for
a multitude of missions. And with a price
tag of roughly $30 million, chances are
that one can only dream of piloting this
world-class fighter.
But E-flite has come to the rescue! Its
semiscale model of the Eagle was
designed around a pair of Park 420 ductedfan
motors, keeping in mind design
features that made the full-scale F-15 such
a success (low wing loading, high thrustto-
weight ratio).
The E-flite version is made from
injection-molded EPS foam, keeping it
lightweight. That’s not a bad idea,
considering that twice the amount of
electronics goes into it. And if the builder
decides to install the factory-supplied
retractable landing gear, three additional
servos and Y harness are needed.
When I opened the box and inspected all
of the F-15 Eagle’s components, I saw
several notable features. The model came
prepainted with the great looks of the
Edwards Air Force Base Safety Chase
paint scheme. Almost all decals were
applied at the factory, and all flight control
surfaces were prehinged. The wings had a
preinstalled carbon wing spar, to increase
wing strength and rigidity.
Fixed and retractable landing gear were
included; I chose to go with retracts. It’s
icing on the cake to watch the gear go up
on a flyby, adding to the scale appearance.
Compared to other models I have built,
I was surprised to see that the F-15 had
such a low parts count. Having never built
or flown a jet of any kind, I had built up
something more complex in mind.
After briefly reading through the
manual, all reservations were laid to rest.
The instructions were well written, with a
step-by-step list of required parts, required
tools and adhesives, and pictures to show
intended results or the finished look.
On occasion, a special note for a
particular step was included to ease the
assembly process. One I particularly liked,
at the beginning of the retract installation,
was an explanation of how to set up
programming for retracts using the DX7
transmitter. This was extremely helpful,
since I had never encountered the need for
this application.
Construction: The assembly process
began with stabilizer installation. Before
permanently installing the electronics in
any project, it is a good practice to lay out and
mock up all of the electronic components.
There are many benefits to making this
one of the first steps in any build; centering
the servos may be one of the most
important. Nothing is more frustrating than
trying to “gracefully” dig a servo out of a
recessed pocket after gluing it in place.
Yes, this is from experience.
I have also learned, as have many other
modelers, that not all servos are created
equal. Some do not mechanically center as
well as others. Putting them in different
channel assignments with different control
horns to get the best result is easier on the
bench without the aircraft involved.
With the servos in their respective
positions, I marked them with a small
piece of tape to remind me of their
placement later. Fortunately, the Eagle has
only two servos (ailerons) in a recessed
pocket that require centering before
installation. With the mock-up done,
installing stabilizer servos is a snap.
Installing the stabilizers brought up a
bit of concern. I found that the stabilizer
control-rod bushings in the fuselage are
not parallel/perpendicular to each other,
because the tail sections’ angles are
different. Installing the stabilizers without
binding took finesse.
The simple solution I came up with was
to insert a drill bit of the same size,
carefully hand-drill the bushings to allow
for better alignment, micro-polish the
stabilizer control rods, and apply graphite
lubricant to both the bushings and the rod.
Then the recommended E-flite S75 servos
were able to properly manage the control
surface without excessive resistance.
When installing the stabilator on each
control rod, you will dent the tail to access
the setscrew, leaving unsightly indentations
on each side. You could make a small
incision to allow for Allen wrench
clearance and glue it afterward, leaving
much less damage.
It was time to put together and install the
motor/fan units. Before assembling both
units, I thought it would be best to balance
both impellers after the initial motor test
run. It proved to be time well spent. I was
impressed with the rpm! Take care not to
squeeze the fan housing while running up
the motor; the housing can easily be
distorted, causing unwanted grinding.
After gaining proper clearance between
the impeller and housing, I mounted the
ducted-fan units in the fuselage. Running
up the motors once more made it apparent
that the impeller clearance had changed.
After a bit more sanding here and there, all
was well. Don’t run motors inside; the
decibel level might anger those who live
with you!
Installing the retractable landing gear
proved to be a bit more time-consuming
than anticipated. The nose gear went in with
no hitches whatsoever, but the main gear
retracts did not fit properly in the fuselage.
Referencing the manual’s pictures, the
spring portion of the gear-strut wires were
wrapped in the opposite direction, causing
them to rest outside of the molded channel.
There was also contact with the actuator
arm.
To correct both of those concerns, I
turned the gear-strut wires to improve
clearance and moved the wires more
inboard, and then I clamped the spring
portion in a vise and tweaked them a little
to readjust the toe out of the wheels.
A small portion forward of the wingalignment
tab needed to be removed so
that the gear would retract completely. I
installed the S75 servos in the fuselage
lower than shown in the manual. Then I
put the servo control arm on with the
pushrod connector close to the fuselage,
which improved the geometry of the
actuator arm and control rod, keeping them
more parallel with the fuselage throughout
the range of movement.
With the aileron servos installed, and
main wing panels attached to the fuselage,
completing the electronics was the last
step before radio setup. I found that
keeping the servo wires and Y harness neat
and tidy inside the battery compartment
aids in battery access.
To achieve that, I used a wire loom that
allowed me to put three leads through
without removing the connector ends. The
result gave the wiring a clean look;
however, I did have to notch the canopy in
the rear to improve the fit.
After setting the control throws to the
recommended rates, glue the vertical
stabilizers in place. Although I had the
urge to install them early, it was a good
idea to save them for last. I lost count of
the number of times I had to flip the F-15
during programming.
Having completed the programming, a
quick balance check (with retracts up) was
all that remained before the maiden flight.
Only 1/2 ounce in the nose was needed to
obtain the factory-recommended balance
point of 33/8 inches from the LE.
Flying: After performing preflight checks,
all systems were go! The Eagle taxied
down the flightline nicely. Powering up to
full throttle, it wasted no time shortening
the runway.
With slight up-elevator, the climbout
was smooth and predictable. Once the
model was airborne, it was apparent that
half throttle is sufficient to perform most
maneuvers of which the F-15 is capable—
unless you feel the need to show off with a
screaming flyby.
During the initial flight, I found myself
pushing up on the elevator while the jet
was inverted. The recommended balance
point left the F-15 a bit nose-heavy for my
liking.
After removing the 1/2 ounce from the
nose that I had installed, the Eagle was
more neutral during the second flight.
Switching to high rates, it was more
responsive, with no unwanted characteristics.
This model performs basic aerobatics
such as loops, rolls, and Split “S”
maneuvers with little to no effort. During
a power stall, I found that I was at the end
of the battery’s capacity, causing one of
the ducted-fan units to shut down. The F-
15 continued to be manageable, even with
the loss of a motor. That proved that you
can make it home on one engine.
Before I could set up approach for
landing, the second motor quit, leaving the
F-15 dead-stick. It was still controllable
with the use of full up-elevator to manage
the descent.
Overall, the E-flite F-15 Eagle is
enjoyable for the ambitious pilot who is
looking to take off with his or her first jet
model. MA
Shawn Rubush
[email protected]
Manufacturer/Distributor:
E-flite/Horizon Hobby
4105 Fieldstone Rd.
Champaign IL 61822
(877) 504-0233
www.e-fliterc.com
Other Published Reviews:
Hobby Merchandiser: July 2008
RC Sport Flyer: October 2008
R/C Report: October 2008