190-02081-03
GFC 600H HFCS Part 27 STC Maintenance Manual
Rev. 3
Page 4-9
4.7 Servo Arm Torque Check
The following checks the friction setting of the servo output arm of the GFS 83 servo (P/N 011-03367-11)
used to control Pitch and Roll axis and is required:
1. Disconnect the control rod (linkage) from the GFS 83 servo output arm in accordance with
Section 6.2. Control rod maybe removed from the rotorcraft, if desired.
NOTE
For the GFS 83 Roll-Axis servo arm (1.5 inch servo output arm), the bolt connecting the
control rod may be left in the output arm, after disconnecting the push rod linkage from the
output arm. Ensure that the bolt left on the servo output arm does not impede the arm
movement thus affecting torque measurement.
2. Remove the servo output arm shear fuse in accordance with Section 6.2.3.
3. Lock the servo output shaft with the Shaft Locking Device (Garmin P/N 117-01307-00).
4. Select a calibrated torque wrench with ¼ inch drive, and set the torque to 40 in-lbf.
5. Place the torque wrench drive into the square hole in the servo output arm. Use a ¼ inch extension
bar, if desired. Ensure the wrench drive is perpendicular to servo output arm and the output arm
movement is not restricted by the wrench drive wedged against the Shaft Locking Device.
6. Apply clockwise (CW) torque to the servo output arm, ensuring the torque wrench drive is square
to the arm.
NOTE
The 117-01080-( ) output arm has a ¼" square hole as well as 1.125" flats, both of which
can be used to couple with a torque wrench. The square hole is offset from the axis of
rotation. Torque wrench drive should be perpendicular to the servo output arm to ensure
accurate torque measurement, regardless if either the square hole or the flats with a
crowfoot attachment are used. Use the torque wrench adapter calculation per AC 43.13-1B
Figure 7-2 to compensate for the measurement if the torque wrench drive is not
perpendicular to the arm.
7. If the output arm does not slip, increase the torque wrench setting by 5 in-lbf. If the arm slips, no
further action is necessary. If it does not, continue to step 8.
8. If step 7 does not pass, the friction must be reduced. Remove the cotter pin from the castellated
nut, and reduce by one castellation.
NOTE
Friction increases by approximately 50 in-lbf for every castle nut rotation (or 1 in-lbf per
every 0.001 inch of nut displacement).
9. Repeat friction measurement in accordance with steps 4-7.
10. Repeat until the required 40-44 in-lbf friction measurement can be achieved.
11. Servo output arm torque reset is
NOT
required if the computed average torque is within 40 to
44 in-lbf. Re-install the shear fuse in accordance with Section 6.2.3.
12. If the computed average torque cannot be achieved, reset the servo output arm torque in
accordance with the reset procedure below.