View Full Version : 737-800 Aileron Trim

13th Sep 2023, 15:58
Aircraft has had LH wing aileron control cables replaced (ABSA & ABSB)
Aileron cable adjusts carried out.

Control wheels are in neutral and A/S-15 can be fitted and removed freely
A/S-1 & A/S-1A can be fitted and removed from aileron transfer mechanism freely.
ACBA & ACBB tensions within range
AA & AB cable tensions within range
A/S-4 fits freely
ABSA & ABSB tensions within range.

During functional test is calls for aileron trim response test. During test, move aileron trims switches left wing down until actuator stops, verify control wheels turn 9.5 trim units or move.
During this step 9.5 or more is not achieved. Indicates approximately 8 units on both control wheels.
If any input is made into the control wheel, left or right, when released 9.5 units or move is now achieved. Unfortunately our AMM does not say you can wiggle the control wheel to settle the new neutral trim positions.
During the initial trim, cam follower bearing leaves the cam detent on the feel and centering unit. Upon completion of the trim actuator movement, cam bearing follower does not return to the detent. It is only after a manual input on the control wheel the cam bearing returns to the detent.

Same problems when trimmed right wing down.

Bearing a cam surfaces inspected with no damage.

Does anyone know if this is a common issue and if so what is the likely causes?

Any helps greatly appreciated.