A B737-300 captain reported that after takeoff 15-18 right aileron trim units were need to attain co...

Narrative:

We took the aircraft from a previous crew to fly one last leg for the night. They reported no problems with the aircraft. After takeoff; found excessive aileron trim needed to fly the aircraft. It took 15-18 units/degrees of right aileron trim to fly coordinated flight; in all configurations from takeoff to landing. First officer was flying. Fuel was balanced; thrust was symmetrical; and the ball was centered; and we needed 15-18 units of right aileron trim to fly coordinated flight. We notified dispatch to inform maintenance; and dispatch told us to return to the departure airport. We were exactly half way to the overnight destination; and we turned around and landed; wrote up the aircraft; and took a different one to our scheduled airport. We did not declare an emergency as we had no problems controlling the aircraft. It appeared to be out of rig. We elected not to fly the 'slam dunk' and coordinated with approach control to fly a 15 mile final to configure the aircraft slowly for landing. Previous crew should have noticed and reported the excessive trim problem.

Original NASA ASRS Text

Title: A B737-300 Captain reported that after takeoff 15-18 right aileron trim units were need to attain coordinated flight so Maintenance asked the crew to return to the departure airport.

Narrative: We took the aircraft from a previous crew to fly one last leg for the night. They reported no problems with the aircraft. After takeoff; found excessive aileron trim needed to fly the aircraft. It took 15-18 units/degrees of right aileron trim to fly coordinated flight; in all configurations from takeoff to landing. First Officer was flying. Fuel was balanced; thrust was symmetrical; and the ball was centered; and we needed 15-18 units of right aileron trim to fly coordinated flight. We notified Dispatch to inform Maintenance; and Dispatch told us to return to the departure airport. We were exactly half way to the overnight destination; and we turned around and landed; wrote up the aircraft; and took a different one to our scheduled airport. We did not declare an emergency as we had no problems controlling the aircraft. It appeared to be out of rig. We elected not to fly the 'slam dunk' and coordinated with Approach Control to fly a 15 mile final to configure the aircraft slowly for landing. Previous crew should have noticed and reported the excessive trim problem.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1006068
Time
Date	201204
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Aeroplane Flight Control
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 451 Flight Crew Type 12000
Events
Anomaly	Aircraft Equipment Problem Critical

A B737-300 captain reported that after takeoff 15-18 right aileron trim units were need to attain coordinated flight so maintenance asked the crew to return to the departure airport.