B737 flight crew reported diverting to an alternate airport after experiencing a stabilizer trim run...

Attributes
ACN	1478908
Time
Date	201709
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737 Next Generation Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Horizontal Stabilizer Trim
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Type 7437
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Type 7124
Events
Anomaly	Aircraft Equipment Problem Less Severe

Narrative:

Normal departure until cleaning up the flaps and slats. After everything was up; got master caution; flight controls; speed trim fail lights. At the same time the aircraft started slow trimming nose up. I was able to counter the movement with the trim switch on the yoke. Kept the speed at 250 and continued the departure so that we could run the non-normal checklist. After turning off the two guarded trim switches below and to the right of the throttles; the runaway condition stopped. Down to manual trim. We [advised ATC] and ATC leveled us off at FL240 and turned us back to [an alternate airport] per our request to divert there. Contacted the company; briefed the flight attendants and passengers. Made a smooth; uneventful overweight landing.

Original NASA ASRS Text

Title: B737 flight crew reported diverting to an alternate airport after experiencing a stabilizer trim runaway.

Narrative: Normal departure until cleaning up the flaps and slats. After everything was up; got master caution; flight controls; speed trim fail lights. At the same time the aircraft started slow trimming nose up. I was able to counter the movement with the trim switch on the yoke. Kept the speed at 250 and continued the departure so that we could run the non-normal checklist. After turning off the two guarded trim switches below and to the right of the throttles; the runaway condition stopped. Down to manual trim. We [advised ATC] and ATC leveled us off at FL240 and turned us back to [an alternate airport] per our request to divert there. Contacted the Company; briefed the Flight Attendants and passengers. Made a smooth; uneventful overweight landing.

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.