Air carrier flight crew reported flying in RVSM airspace with the autopilot off due to stabilizer trim issue.
Synopsis
Air carrier flight crew reported flying in RVSM airspace with the autopilot off due to stabilizer trim issue.
Narrative
Departed Runway XXC. On climb out we get a stabilizer trim malfunction as we enter IMC weather with thunderstorm cells nearby. We do the memory items; run the QRC; QRH; and keep the autopilot and autothrottles off as directed per the procedure while climbing to avoid and deviating around thunderstorms in IMC conditions. The malfunction does not continue; and aircraft flies normal. The climb is continued to avoid weather and to gain altitude so that if a malfunction occurs again; there's altitude to recover. After that we level off; ACARS message Dispatch; and get a phone patch to Maintenance Control. I do not know if another trim malfunction will occur or not during flight. We assessed the situation; balanced the task loading; and communicated with all available resources. Also; maintained aircraft control; analyzed the situation; took the appropriate action; and landed when the situation permitted. A joint decision between Dispatch and the Crew was made to divert to ZZZ1 and not fly back through the weather we just came through to return to ZZZ. Dispatch sends us the divert information; and we use the divert planning checklist. We calculated performance data for a Flaps 15 landing and also calculate brake cooling temperatures prior to landing. Landed in ZZZ1 without incident; and it was during the debrief with a Supervisor I realized my error of unintentionally flying at FL 340 without using the autopilot in RVSM airspace. I was in high task saturation the whole departure phase. My biggest concern was staying safe by accomplishing the applicable QRH procedure and avoiding storm cells. We could have asked each other where we were in regards to risk management. Also; would it be possible to add check RVSM requirements" on the divert section of the checklist? It's a huge reminder during task saturation."
Second reporter narrative
We departed Runway XXC out of ZZZ with weather off the departure end. There were thunderstorms closing in on the field from the north and the Captain was flying. Around 400 ft AGL the aircraft pitched up to about 20 degrees followed by a nose down pitch and then another nose up pitch to about 20 degrees. The trim would run in the direction that the Captain's side electric trim was selected for. Around 600 ft AGL the Captain said something like I think we have runaway trim". The Captain made a right turn to our assigned heading which got the nose down. The Captain immediately performed the memory items but did not move the Stab Trim Cutout switches because the aircraft was under control now and the trim had stopped moving. I; the F/O (First Officer); tried my electric trim and both directions worked normally. We continued to climb and deviate around weather. We ran the QRC and QRH and began to fly towards our destination and continued climbing out of the weather. Once we leveled off; we notified Dispatch through ACARS of the situation; we told ATC; and we were able to get a hold of Maintenance. Both Pilots and the Dispatcher decided to divert to ZZZ1. We took turns hand flying the aircraft the rest of the way. We briefed our arrival and approach and what we would do if the trim began to run again and what we would do in case of a go-around. We had an uneventful Flaps 15 landing and taxied to the gate. Maintenance met us at the gate; and we deplaned normally. Not until after landing did we realize that we had flown into RVSM airspace with the autopilot off. Although we did not deviate from our assigned altitude by more than 1000 ft; we were so task saturated that we had completely forgotten about RVSM requirements. A note on the QRC or QRH or even diversion checklist about airspace requirements would've caught the error."
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.