Trio Avionics Pro Pilot - Manual (Page 76)

Trio Pro Pilot Manual 3.8
76
The servo mounting location must be strong and rigid. If,
for example, you need to mount the servo on the skin of an
airplane, it will be necessary to use additional bracing or a
“doubler” to provide appropriate rigidity. You do not want
the movement (rocking) of the servo to fatigue the mounting
structure.
When mounting the servo, be careful not to drill mounting
holes into critical load bearing members. It may be best to
construct a mounting plate, place and bond machine screws
so that they will interface with the case mounting holes, and
then secure the assembly into place. For a composite aircraft installation, the bottom of the plate
(shown) should be floxed and the holes in the plate filled with flox before applying fiberglass layers over it
to secure it to the fiberglass structure.
NOTE : It is important that the servo mounting plate surface be flat and smooth. If it is not, this can
distort the servo frame when the servo is secured to the mounting plate.
Usually the servo pushrod will terminate on a control pushrod or a bell crank. If you are connecting to a
pushrod care should be taken to keep the pushrod from being free to rotate. (To repeat, the
pushrod should NOT rotate.)
The reasoning for this is that as the pushrod rotates there is “lost motion” in the system, i.e., movement
of the crank arm does not result in movement of the control system. The control movements are so
small that it takes very little slop in the system to make the airplane not track properly.
It will simplify installation adjustments if there is enough overhead clearance to allow removal and
replacement of the servo lid with the servo remaining in place (for instance, you will possibly want to
adjust the slip clutch). The servo lid is secured by two screws on the top of the servo.
Positioning the Servo Crank Arm
The crank arm is not attached to the servo when shipped. To suit your particular installation, you will
need to position the servo crank arm to get the correct geometry to drive the control system. It can be
installed in one of 4 positions, in 90 degree increments. The screws that are supplied have Loctite®
applied to the threads. Once these screw are tightened, the will be very difficult to remove – so be sure
that the crank arm orientation is correct.
Should it be necessary to remove the screws, once installed, it is required to apply heat with a heat gun
before attempting to loosen the four screws. The heat should be applied for at least one minute to allow
the Loctite® to soften. Failure to heat the assembly will more than likely cause the screws to break off
when being removed.
If it is necessary to reposition the servo Crank Arm, perform the following steps:
1. Use a #2 Phillips screwdriver to remove the screws. Ensure sufficient pressure is used to
prevent slippage of the screwdriver and subsequent rounding of the screw heads.
2. Rotate the crank arm to the correct position for your installation.
3. When satisfied with the positioning, apply a small amount of Loctite® 222 to the screws, reinsert
and tighten the screws.
Install the Servo Pushrod
Cut the pushrod to the proper length so that, when the servo is at neutral, or centered in its full rotation
stop to stop, the aircraft aileron or elevator is also neutral (see note).
Choose the longest possible crank arm radius that accommodates a pushrod range of movement equal
to or exceeding that required for full aileron or elevator travel.