A B737-300 flight crew reported both autopilots would mis-trim the aircraft; so they continued with ...

Attributes
ACN	891322
Time
Date	201005
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Climb
Component
Aircraft Component	Autopilot
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 149 Flight Crew Type 8000
Person 2
Function	Pilot Flying First Officer
Experience	Flight Crew Last 90 Days 239
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural FAR Deviation - Procedural Published Material / Policy

Narrative:

I was the pilot monitoring while the first officer was flying the departure. After climbing above about 17;000' MSL; the 'stab out of trim' light illuminated. We followed the checklist while continuing the climb. The stab trim worked properly with the autopilot disengaged. Following the recommendation of the checklist; we re-engaged the autopilot in the climb; again after several minutes of use; the 'stab out of trim' light illuminated. We then retrimmed the aircraft and switched the control of the aircraft to me. I then engaged the 'a' autopilot to see if that would make a difference. After a few minutes; it did the same thing. At that point; we were leveling off at FL360. After completing the level off and stabilizing the airspeed/retrimming; we re-engaged the 'a' autopilot. After a few minutes; the autopilot began to trim the stab into an out of trim position. At that time; I gave the flight controls back to the first officer; notified dispatch; and continued. There should be mention on the 'stab out of trim' checklist about flying in rvsm airspace without an autopilot.

Original NASA ASRS Text

Title: A B737-300 Flight Crew reported both autopilots would mis-trim the aircraft; so they continued with the autopilot disengaged. They realized later they were no longer legal for RVSM operations.

Narrative: I was the Pilot Monitoring while the First Officer was flying the departure. After climbing above about 17;000' MSL; the 'Stab out of Trim' light illuminated. We followed the checklist while continuing the climb. The stab trim worked properly with the autopilot disengaged. Following the recommendation of the checklist; we re-engaged the autopilot in the climb; again after several minutes of use; the 'Stab out of Trim' light illuminated. We then retrimmed the aircraft and switched the control of the aircraft to me. I then engaged the 'A' autopilot to see if that would make a difference. After a few minutes; it did the same thing. At that point; we were leveling off at FL360. After completing the level off and stabilizing the airspeed/retrimming; we re-engaged the 'A' autopilot. After a few minutes; the autopilot began to trim the stab into an out of trim position. At that time; I gave the flight controls back to the First Officer; notified Dispatch; and continued. There should be mention on the 'Stab out of Trim' Checklist about flying in RVSM airspace without an autopilot.

Data retrieved from NASA's ASRS site as of April 2012 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.

A B737-300 flight crew reported both autopilots would mis-trim the aircraft; so they continued with the autopilot disengaged. They realized later they were no longer legal for rvsm operations.