Trio Avionics EZ Pilot - v 2.3 - Manual (Page 30)

26
The servo crank arm uses a pushrod terminated by rod end bearings to link the servo arm to the
aircraft aileron control system. The pushrod provided in the installation kit should be trimmed to
the correct length for your particular installation.
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 hub by four machine screws that can be
removed for indexing the crank arm in 90 degree increments (see Paragraph 7.8 for additional
precautions).
In most cases the servo is installed with the bottom of the servo parallel to the ground, but it
operates equally well in any orientation.
There are four holes in the crank arm that give operating radii with the combinations of force and
peak-to-peak travel listed in Table 1 below:
Crank Arm Radius Max. Travel (peak-to-peak) Pounds of Force
1.0 inch 1.5 inch 36
1.2 inch 1.8 inch 30
1.4 inch 2.1 inch 26
1.6 inch 2.4 inch 22.5
Choose an operating radius on the servo crank arm that allows full aileron movement
(aileron stop to aileron stop) without driving the servo crank arm into its limits (+/- 50
degrees). Most aircraft get best performance in the 3
rd
or 4
th
(outermost) hole.
7.2 Servo Mounting Hardware
A hardware mounting kit is shown below. A push rod is provided, with two rod end
bearings. The pushrod has a tapped insert riveted into one end. The other end is left
open so the tube can be cut to proper length. Once the rod is cut to the desired length,
the second insert must be riveted into place. Typically, the end of the pushrod connects
to the servo crank arm and the other attaches to an aileron bellcrank. When the servo is
connected to the aileron control system it should be installed so that the servo crank arm
is at a right angle to the bellcrank. This mechanically centers the servo mechanism to the
control system so that there is equal displacement in either direction when the servo is
actuated. Fine zeroing using electrical trim will be accomplished later in paragraph 7.6.4.
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 EZ Pilot
control head must be programmed to reverse the drive signal.