Narrative:

After departure aircraft was being hand flown and trimming normally. Early in the climb the 'speed trim fail' illuminated momentarily then extinguished. This happened two more times. I was the pilot monitoring and reviewed the QRH procedure just in case. We continued to an initial altitude of FL330. At that point the auto pilot failed to engage and the 'speed trim fail' light illuminated and stayed on. We descended to FL270 to comply with non-rvsm requirements and informed ATC while attempting to contact dispatch. Dispatch sent us a new flight plan showing arrival fuel of 4.4. The ride was fairly bumpy and the [destination] weather was not optimal in case of a diversion. We had just flown over [an airport] where the weather was mostly clear. We coordinated with dispatch and diverted. Upon reaching the gate maintenance was standing by as required. After a lengthy system test; all checked normal. Maintenance had discovered that the stab trim cutout for the auto pilot trim was in the 'off' position. Both guards were down with the main electric trim switch was in the on or normal position even though both guards were down. The plane had come from the hanger after completing a PCU (power control unit) replacement. Switches were not placed back to the normal positions per their checklist. Further; during the pre-flight check the first officer missed that the switches were not in their normal 'on' position. I had failed to notice the guards in the wrong position as well. Lesson learned; take a little extra time pre-flighting especially coming from the hanger. Supplemental note in QRH about checking that both trim cutout switches are in the proper position.

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Original NASA ASRS Text

Title: B737-800 Flight Crew reported a speed trim light indication and an inoperative autopilot during climb. Fuel concerns; weather; and the inability to operate in RVSM airspace prompted the crew to divert. Maintenance discovered that the Autopilot cutout switch was in the cutout position and had been missed during the preflight inspection.

Narrative: After departure aircraft was being hand flown and trimming normally. Early in the climb the 'speed trim fail' illuminated momentarily then extinguished. This happened two more times. I was the pilot monitoring and reviewed the QRH procedure just in case. We continued to an initial altitude of FL330. At that point the auto pilot failed to engage and the 'speed trim fail' light illuminated and stayed on. We descended to FL270 to comply with non-RVSM requirements and informed ATC while attempting to contact dispatch. Dispatch sent us a new flight plan showing arrival fuel of 4.4. The ride was fairly bumpy and the [destination] weather was not optimal in case of a diversion. We had just flown over [an airport] where the weather was mostly clear. We coordinated with dispatch and diverted. Upon reaching the gate maintenance was standing by as required. After a lengthy system test; all checked normal. Maintenance had discovered that the stab trim cutout for the auto pilot trim was in the 'off' position. Both guards were down with the main electric trim switch was in the on or normal position even though both guards were down. The plane had come from the hanger after completing a PCU (Power Control Unit) replacement. Switches were not placed back to the normal positions per their checklist. Further; during the pre-flight check the first officer missed that the switches were not in their normal 'on' position. I had failed to notice the guards in the wrong position as well. Lesson learned; take a little extra time pre-flighting especially coming from the hanger. Supplemental note in QRH about checking that both trim cutout switches are in the proper position.

Data retrieved from NASA's ASRS site 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.