B737-ng captain reported losing both captain and first officer control wheel stabilizer trim switche...

Narrative:

Shortly after takeoff we lost both the captain's and first officer's control wheel stabilizer electric trim. We stopped our climb and leveled at 14000 ft to troubleshoot the problem. The first officer could not find an exact match for failure of only the control wheel trim switches. The closest procedure was 'electric stabilizer trim inoperative.' this procedure deals with a failure of both the control wheel and autopilot electric trim. Reading through this procedure we opted to turn on the autopilot to test whether the electric trim worked in the autopilot mode. It did work; so now we knew we had electric trim through the autopilot and manual trim though the trim wheel. We called dispatch and maintenance and all agreed that we could safely proceed to our destination.enroute we began going further into the systems and procedures to determine how we would conduct the approach and landing. Here is where I feel there needs to be a clarification and procedure for a complete failure of the control wheel stabilizer electric trim system. We originally thought of doing an autoland which would allow the aircraft to maintain electric trim throughout the landing. However; we looked up mels related to the control wheel trim failure and found MEL 2709 which deals with a failure of just one of the control wheel switches. In that MEL it restricts the plane to CAT I no autoland. Even though we were not sure why the plane would be only CAT I; we decided that we should not use autoland in our situation. Next we went back to the QRH procedure for electric stabilizer trim inoperative and in the objective section of the procedure we noted that it could be used for landing the aircraft using manual trim; which would be our situation. We decided the best course of action would be to use the autopilot and configure the aircraft for landing; get on speed; and then turn the autopilot off and use the QRH procedure for the remainder of the approach and landing. The procedure would require a flaps 15 landing and turning the stab trim cutout switches to cutout; then using manual trim.[dispatch] did send us a recommended procedure via ACARS that he vetted through the 737 fleet. They suggested what we had planned. However they also suggested turning both stab trim cutoff switches to cutout and then back on as a sort of reset. We decided that putting the autopilot stab trim cutout switch to cutout before final configuration was not the best move since it could eliminate the only source of stabilizer electric trim. We did however cycle the main electric switch to cutout and back on when we were level on the arrival and the control wheel trim did start working. However I cannot be certain if that is what reset the system or it was something else because I did not try the control wheel switches before I put the switch to cutout. We continued the arrival and landed using normal procedures.the purpose of this report is to point out an ambiguity of what to do if this malfunction happens again. There needs to be a procedure that clarifies what a crew should do in this situation. In particular whether to reset the cutout switches; either both or just the affected side; and how to configure the aircraft for landing.

Original NASA ASRS Text

Title: B737-NG Captain reported losing both Captain and First Officer control wheel stabilizer trim switches. He expressed some confusion occurred while trying to interpret the procedure dealing with the issue.

Narrative: Shortly after takeoff we lost both the Captain's and First Officer's control wheel stabilizer electric trim. We stopped our climb and leveled at 14000 ft to troubleshoot the problem. The First Officer could not find an exact match for failure of only the control wheel trim switches. The closest procedure was 'Electric stabilizer trim inoperative.' This procedure deals with a failure of BOTH the control wheel and autopilot electric trim. Reading through this procedure we opted to turn on the autopilot to test whether the electric trim worked in the autopilot mode. It did work; so now we knew we had electric trim through the autopilot and manual trim though the trim wheel. We called dispatch and maintenance and all agreed that we could safely proceed to our destination.Enroute we began going further into the systems and procedures to determine how we would conduct the approach and landing. Here is where I feel there needs to be a clarification and procedure for a complete failure of the control wheel stabilizer electric trim system. We originally thought of doing an autoland which would allow the aircraft to maintain electric trim throughout the landing. However; we looked up MELs related to the control wheel trim failure and found MEL 2709 which deals with a failure of just one of the control wheel switches. In that MEL it restricts the plane to CAT I no autoland. Even though we were not sure why the plane would be only CAT I; we decided that we should not use autoland in our situation. Next we went back to the QRH procedure for Electric Stabilizer Trim Inoperative and in the objective section of the procedure we noted that it could be used for landing the aircraft using manual trim; which would be our situation. We decided the best course of action would be to use the autopilot and configure the aircraft for landing; get on speed; and then turn the autopilot off and use the QRH procedure for the remainder of the approach and landing. The procedure would require a flaps 15 landing and turning the Stab Trim Cutout switches to Cutout; then using manual trim.[Dispatch] did send us a recommended procedure via ACARS that he vetted through the 737 fleet. They suggested what we had planned. However they also suggested turning both Stab Trim Cutoff switches to Cutout and then back on as a sort of reset. We decided that putting the autopilot stab trim cutout switch to cutout before final configuration was not the best move since it could eliminate the only source of stabilizer electric trim. We did however cycle the main electric switch to cutout and back on when we were level on the arrival and the control wheel trim did start working. However I cannot be certain if that is what reset the system or it was something else because I did not try the control wheel switches before I put the switch to cutout. We continued the arrival and landed using normal procedures.The purpose of this report is to point out an ambiguity of what to do if this malfunction happens again. There needs to be a procedure that clarifies what a crew should do in this situation. In particular whether to reset the Cutout switches; either both or just the affected side; and how to configure the aircraft for 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.

Attributes
ACN	1370202
Time
Date	201607
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZZ.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Light	Daylight
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 Last 90 Days 160 Flight Crew Total 7117 Flight Crew Type 1385
Events
Anomaly	Aircraft Equipment Problem Less Severe

B737-ng captain reported losing both captain and first officer control wheel stabilizer trim switches. He expressed some confusion occurred while trying to interpret the procedure dealing with the issue.