Great Planes PT-40 MkII Kit - GPMA0118 - Manual (Page 47)

For three channel operation the rudder servo should be
plugged into the aileron plug in the receiver (channel #1 on
most receivers).
Your “main steering function” in the air is
always done on the right stick. Later, when you transition to
a four channel model, you will have to “relearn” ground
steering your PT on the left stick (where the rudder and
nose steering will be moved to when you add ailerons).
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13. Connect the receiver to the servos, switch and
battery. Turn on your transmitter and receiver, then position
the elevator, r udder and aileron tr im tabs on your
transmitter in the center. This is called “centering” the
servos and will allow you to place the servo horns on the
servos in a neutral position.
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14. Slide the nose steering and throttle pushrods into the
respective screw lock connectors on the servo horns. Use a
pliers to bend each rod so the horns will fit on the servos
with little or no binding.
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15. Fit the elevator, rudder, and throttle horns on the
servos and temporarily place the receiver inside the
fuselage at the approximate location shown on the plan.
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16. Glue the aileron servo tray supports to the aileron
servo tray, then glue the doublers to the bottom of the tray.
Securely glue the assembly in the wing the way we showed
you during final wing construction.
Skip step #17 if you are building your PT as a
3-channel model.
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17. If you are building your PT as a 4-channel model
with ailerons, drill the holes for the servo mounting screws,
then mount the aileron servo to the servo tray. Place a large
servo wheel on the servo.
We’ll stop installation of the radio at this point, then resume
after the model is balanced. It’s helpful to be able to shift
the servo tray when balancing the model.
Note: This section is VERY important and must NOT be
omitted! A model that is not properly balanced will be
unstable and possibly unflyable.
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1. Use a felt-tip pen or a narrow strip of tape to accurately
mark the balance point on the bottom of the wing near
both sides of the fuselage. The balance point (CG) is shown
on the plan and on the PT-40 is located 4-7/64" (104mm)
back from the leading edge. For the PT-20 the balance
point is located 3-1/2" (89mm) back from the leading
edge. This is the point at which your model should balance
for your first flights. Later, you may experiment by shifting
the balance up to 1/4" forward or back to change the
flying characteristics. Moving the balance forward may
improve the smoothness and arrow-like tracking, but it may
require more speed for takeoff and make it more difficult to
Balance Your Model
If, at any point during the radio installation and hook up
that follows, it becomes apparent that the elevator and
rudder servo horns or pushrods will interfere, you can
“flip flop” the elevator servo to provide a little more
clearance between the two servo horns. This will not
change any part of your setup except that you will make
the elevator pushrod a little shorter.
47
NOTE TO PT-20 BUILDERS PT-40
4-7/64"
PT-20
3-1/2"