Trio Avionics Pro Pilot - Manual (Page 74)

Trio Pro Pilot Manual 3.8
74
You will mount the servo and pushrod so that the control surface is in a neutral position when the servo
crank arm is at mid position. That’s it, aside from carefully checking that the required range of control
movement is available within the limits of the servo travel range, and that no “over center”
condition can exist. Also, assure that the aircraft control system hits its “stops” before the servo
crank arm hits its “stops”.
The servo crank arm uses a pushrod terminated by rod end bearings to link the servo arm to the aircraft
control system. The pushrod provided in the installation kit should be trimmed to the correct length for
your particular installation.
The servo must be mounted on a solid platform that will not buckle or “oilcan” and attached to a firm
existing support. It is recommended that the servo platform not be mounted to the aircraft “skin” without
a doublers and some other additional support. Rigidity of the servo mount is critical to proper servo
operation. If you do not have the experience required to fabricate the required bracket please contact
Trio Avionics for guidance.
In your installation, it may be more convenient to rotate the crank arm to a new orientation that will give a
neutral (servo center position) at +/- 90 degrees or 180 degrees from that as supplied from the factory.
The servo crank arm is secured to a flange by four machine screws that can be removed for indexing the
crank arm in 90 degree increments.
If the screws need to be removed to reposition the crank arm, after repositioning, Loctite Number 222
must be reapplied (very sparingly) to prevent loosening of the screws.
Choose an operating radius on the servo crank arm that allows full elevator movement (control stop to
control stop) without driving the servo crank arm into its limits. Most aircraft get best performance in the
Note: It is important to assure that the proper direction of travel is
preserved when modifying the crank arm orientation. Changing the crank
arm mounting by 180 degrees will essentially reverse the direction of
travel for the servo arm. In such a case the Pro Pilot must be
programmed to reverse the drive signal. In the event unusual pitch
changes occur in the first flight, the first check on the ground should be to
be certain the servo direction of travel is correct.
OVER-CENTER TESTING
An over-center condition will result in a complete locking of the control system during operation. The
result of this is that you will lose all control of the airplane.
When installing the servo, ensure that under any flight conditions, including inverted flight, control
system flexing, airframe flexing, extreme turbulence or any other abnormal flight conditions,
IT IS CRITICAL TO ENSURE NO POSSIBILITY THAT AN OVERCENTER CONDITION CAN
OCCUR.
Close is not good enough in this case. If you have any questions of doubts, please consult a
qualified technical counselor or call Trio Avionics for consultation.
When shipped, the crank arm and screws are not attached to the servo. This allows easy
installation of the crank arm for each particular installation. The appropriate Loctite compound is
pre-applied to the screws accompanying the crank arm.