System Maintenance Manual

Page 8-12 G1000/GFC700 System Maintenance Manual – C90A/C90GT/C90GTi King Air
Revision F 190-00682-01
13. Press the FLC key on the AFCS mode controller and verify that ‘FLC’ is annunciated on PFD1
and PFD2 in green with a reference of 100 KTS.
14. Press the ALT SEL key on the AFCS mode controller and verify that the ‘ALT’ annunciation is
displayed in green on PFD1 and PFD2 with an altitude reference equal to the aircraft altitude
(within the nearest 20 feet).
15. Press the FD key and verify that the mode annunciations and command bars are removed from
the display.
8.2.3 Autopilot Clutch Overpower Check
NOTE
The GFC 700 uses electronic torque limiting as well as mechanical slip clutches to limit
the maximum servo effort. When the system is on the ground, the electronic torque
limiting is removed, allowing manual checks of the slip-clutch settings.
1. Engage the Autopilot by pressing the AP key on the AFCS mode controller.
2. Manually overpower the autopilot clutches in pitch and roll. If the Autopilot clutches cannot be
overpowered, check the servo clutch torque settings. For the GSM 86, if the GSM86 clutch
cannot be overpowered, check the GSM 86 clutch cartridge. Refer to the servo installation
drawing (listed in Table 1-2) as applicable.
3. Actuate and hold PITCH TRIM switch in either the NOSE UP or NOSE DOWN direction to
disconnect the autopilot. While the trim is running, restrain the aircraft pitch trim wheel and
verify that the trim clutch can be overpowered. If it cannot be overpowered, check the trim servo
clutch torque setting. For the GSM 86, if the GSM86 clutch cannot be overpowered, check the
GSM 86 clutch cartridge. Refer to the pitch trim servo installation drawing, listed in Table 1-2.
4. Engage the autopilot by pressing the AP key on the AFCS mode controller. Actuate and hold the
manual electric trim switch in either the up or down direction to disconnect the autopilot. Verify
that the trim wheel moves smoothly in both directions throughout the entire trim range during
manual electric trim operation. If the trim wheel hesitates, this may indicate that the pitch trim
clutch is slipping and proper clutch setting and cable tension should be verified. Refer to the
King Air Model 90 Series Maintenance Manual and Pitch Trim Servo Install drawing, listed in
Table 1-2, for clutch settings and cable tensions. If both clutch setting and cable tension are
within tolerance, check the aircraft pitch trim system for excessive friction. Refer to the
appropriate C90 Maintenance Manual, listed in Table 1-2.
8.2.4 Manual Electric Pitch Trim Speed Check
1. Run MANUAL ELECTRIC PITCH TRIM in one direction until it runs against the mechanical
stop.
2. Run the trim in the opposite direction, and using a stop watch or equivalent device, time the trim
speed to the opposite mechanical stop. Verify the elapsed time for full travel measures 15 ± 5
seconds.
8.2.5 Autopilot Operation Checks
1. Engage the Autopilot by pressing the AP key on the AFCS mode controller. Push the HDG knob
to synchronize the heading bug to the current aircraft heading. Select HDG mode by pressing the
HDG key on the AFCS mode controller. Verify the command bars are level and the control wheel
is stationary. (There may be some roll motion in the yoke if the aircraft not perfectly level.)