CRJ-550 flight crew reported stabilizer trim and TCAS malfunctions.
Synopsis
CRJ-550 flight crew reported stabilizer trim and TCAS malfunctions.
Narrative
Stabilizer trim was unresponsive to trim control input during flight. After completing available QRH procedures; we cycled the stab trim channels by pressing the 'Stab Trim Disc'; and re-engaging the Stab Trim Channels.Flight was a ferry flight from ZZZ2 ZZZ1. All trim and flight controls were functioning normally during preflight and initial climbout. Climbing through approximately FL260; we received a MACH TRIM caution msg; accompanied with a STAB FAULT status msg. We completed QRH for MACH TRIM and msg persisted. The Autopilot was still functioning and we continued normal flight according to procedure. Referencing the STAB FAULT status message informed us we had lost system redundancy. Cruise was normal in regards to trim. Seemingly unrelated we also had multiple intermittent TCAS FAIL messages during cruise. These would clear in seconds and then function normally. In descent at approximately FL200; we received an AP PITCH TRIM caution msg. Running the QRH required disengaging the Autopilot and manually trimming the stabilizer. According to our MACH TRIM fault procedure; we needed to slow below 250 kts. The trim indication was 1.6 at this time; and stab trim was unresponsive to either Captain or First Officer (FO) trim switch inputs. The issue persisted after accomplishing QRH. Searching for further QRH procedures for our condition; we did not find an applicable procedure; stab trim channels indicated engaged; but stab trim was unresponsive. Upon completing our descent procedures; we verified CBs were not popped and based on system knowledge; we discussed and chose to activate STAB TRIM DISC; which disengaged both stab trim channels. We re-engaged the stab trim channels; and regained STAB TRIM CHANNEL 2; but not STAB TRIM CHANNEL 1. With STAB TRIM CHANNEL 2; we now had control and function of the stabilizer trim. We continued to a normal landing at ZZZ.'Suggestion add a QRH procedure; or include a step within a procedure; that would direct the crew to utilize the 'Stab Trim Disc' when stabilizer trim is unresponsive with Stab Trim Channels engaged. The closest applicable QRH procedure looks to be 'STAB TRIM' caution msg; which we did not receive. But this procedure does not have STAB TRIM DISC as a step.
Second reporter narrative
Stab Trim required manual disconnect to reengage after AP PITCH TRIM caution. Climbing through FL260 @ 290 KIAS we received a MACH TRIM caution and STAB FAULT status. Ran QRH and messages persisted. We continued normally with Autopilot engaged as per QRH. While in cruise at FL330 we received intermittent TCAS FAILs on the Primary Flight Display (PFD) that cleared each time before there was time to run the QRH. While descending through FL200 we received an AP PITCH TRIM caution and ran QRH. We slowed to 250 KIAS before disengagement of Autopilot to comply with previous MACH TRIM QRH. Upon disengagement of Autopilot the manual pitch trim would not move up or down. None of the QRHs reference a manual disengagement of stab trim; just to verify stab trims are engaged; which we were indicating. After all non-normal checklists were complied with and still no control of pitch trim we agreed to attempt a manual disengagement of the stab trim with the yoke STAB TRIM DISC to attempt to regain control of the pitch trim before level off. After manual disengagement of stab trim we were able to reengage stab trim channel 2; channel 1 never reengaged. With stab trim channel 2 engaged we regained control of pitch trim and continued for a normal landing. After shutdown we contacted Maintenance Control to relay the discrepancies. Add verbiage in QRH to manually disconnect stab trim if indicating trim is engaged but not moving.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.