Trim Tab Free Play Inspection; Trim Tab Control Wheel Removal/Installation; Trim Tab Control Adjustment/Test - Cessna 172 Series 1996 Maintenance Manual

CESSNA AIRCRAFT COMPANY
MODEL 172
MAINTENANCE MANUAL
(7) Check bearing for smoothness of operation.
(8) Do not attempt to repair damaged or worn parts of the actuator assembly. Discard all defective
items and install new parts during reassembly.
5. Trim Tab Free Play Inspection
A. Inspect Trim Tab Free Play (Figure 203).
(1) Place elevator and trim tab in neutral position and secure elevator from movement with elevator
gust lock.
(2) Determine maximum amount of allowable free play.
(a) Measure chord length at extreme inboard end of trim tab as shown in Detail C.
(b) Multiply chord length by 0.025 to obtain maximum allowable free-play.
(c)
Measure free-play at same point on trim tab that chord length was measured.
(d) Total free-play must not exceed maximum allowable as calculated in step (2)(b).
(3) Using moderate hand pressure (up and down, measure free play at trailing edge of trim tab.
(4)
If trim tab free play is less than maximum allowable, the system is within prescribed limits.
(5) If trim tab free play is more than maximum allowable, check the following items for looseness
while moving trim tab up and down.
(a) Check push-pull channel to trim tab horn assembly attachment for looseness.
(b) Check push-pull channel to actuator assembly threaded rod end attachment for looseness.
(c) Check actuator assembly threaded rod end for looseness in the actuator assembly.
(6) If looseness is apparent while checking steps (a) and (b), repair by installing new parts.
(7) If looseness is apparent while checking step (c), threaded rod end is out of tolerance and must
be replaced.
6. Trim Tab Control Wheel Removal/Installation
A. Remove Trim Tab Control Wheel (Refer to Figure 204).
(1) Relieve cable tension at turnbuckle.
(2) Remove pedestal cover.
(3) Remove screws attaching control wheel retainer.
(4) Remove retainer and pointer, using care not to drop trim control wheel.
B. Install Trim Tab Control Wheel (Refer to Figure 204).
(1) Install retainer and pointer with screws.
(2) Install pedestal cover.
(3) Set cable tension at turnbuckle. Refer to Trim Tab Control Adjustment/Test.
7. Trim Tab Control Adjustment/Test.
CAUTION: POSITION A SUPPORT STAND UNDER TAIL TIE-DOWN RING TO PREVENT
TAILCONE FROM DROPPING WHILE PERSON IS WORKING INSIDE.
A. Set Trim Tab Control Cable Tension (Refer to Figure 205).
(1) Remove rear baggage compartment panel and access plates as necessary.
(2) Loosen travel stop blocks on cables.
(3) Disconnect actuator from trim tab push-pull channel.
(4) Check cable tension and adjust turnbuckle as necessary.
NOTE: If chains or cables are being installed, permit actuator screw to rotate freely as chains
and cables are connected.
(5) Rotate trim wheel full forward. Ensure pointer does not restrict wheel movement. If necessary,
reposition pointer using a thin screwdriver to pry trailing leg of pointer out of groove.
(6) With elevator and trim tab both in neutral, place inclinometer on tab and set at zero.
(7) Rotate actuator screw in or out as required to place tab up with a maximum of two degrees over
travel, with actuator screw connected to push-pull channel.
(8) Rotate trim wheel to position tab up and down, readjusting actuator screw as required to obtain
overtravel in both directions.
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Page 208
Aug 18/2001