EMB-175 flight crew reported a pitch trim failure; resulting in a temporary loss off pitch control. After completing the appropriate QRH checklist; pitch trim control was restored; and an uneventful landing was accomplished.
Synopsis
EMB-175 flight crew reported a pitch trim failure; resulting in a temporary loss off pitch control. After completing the appropriate QRH checklist; pitch trim control was restored; and an uneventful landing was accomplished.
Narrative
During approach to runway XX in ZZZ we experienced a pitch trim fail event. I was the pilot flying. The event first started at around 2500 feet on the RNAV approach while the aircraft was following the glidepath. The autopilot was on and the plane was being configured for landing. The first indication we experienced can be described as vertical oscillation with the nose of the plane rising and falling twice or so; then continuing to follow the glidepath. Our initial reaction to this was that it was some sort of wake turbulence encounter; that being just an assumption at the time; despite not feeling like wake turbulence I had experienced in the past; which; is typically a rolling and yawing movement. After it stopped the movement we continued because the movement did not take us off glidepath path very far and the approach was still stable and uneventful otherwise. Not long after; within a couple minutes or so; the movement began again. This time I knew something more was going on and my reaction to this realization was to press and hold the Autopilot (AP)/ Trim disconnect button. Just prior to doing so I noticed that the pitch indication was moving. After pressing the AP/ Trim disconnect button we got the AP FAIL and PITCH TRIM FAIL EICAS messages. I followed the memory items for the pitch trim runaway QRC and called for the QRC. We discontinued the approach and made clinging left turn. We notified ATC. We communicated with them and requested priority handling. During this time I decided that I wanted to begin making a left downwind for Runway XY and began to do so in a way that would give us time to run the QRH. We communicated our intentions to ATC. The FO ran the PITCH TRIM FAIL QRH as that was the EICAS message that we had. During this time while flying the plane with add pressure on the control column my thumb would slip off the AP/ TRIM disconnect button due to some turbulence and my hand getting tired. I flew the plane with both hands on the left side of the yoke so each thumb could hold the button for the extended time. During the time when my thumb initially slipped off the button I noticed the trim indication moving. I was able to maintain control of the aircraft while working through the event. Once the QRH procedure was completed we regained control of the trim and made a normal approach and landing on runway XY with the autopilot off.
Second reporter narrative
We were established on the Rnav XX into ZZZ. We were holding 170kts till ZZZZZ about a 5 mile final with autopilot (AP) and autopilot pitch trim (AT) on. Captain was PF and I was PM. Just prior to the fix we selected flaps 3 gear down. Soon after we pass ZZZZZ the captain remarks something's not right. I asked him what was wrong as I don't notice anything on the primary flight display or EICAS in that moment. Seconds after the auto pilot turns off and we get a pitch trim fail and autopilot fail EICAS message simultaneously. Additionally we also lose our pitch trim indication. Captain calls for the QRH; I grabbed the QRH and suggest to discontinue the approach. I call ATC and they give us a left cross wind heading and altitude of 3000. At this moment we start to clean up the aircraft but captain asks to leaving the gear down as it's helping him maintain control of the aircraft. We continue the turn to a left downwind for XY and the captain asks me to request priority handling. ATC is also calling out altitude deviations as we struggle to maintain 3000. I then run the pitch trim failure QRH. The procedure direct us to push in then out the pitch trim system 1 and 2 cutout buttons. I can't recall if I pushed in the cut out switches or if the captain did previously before I ran the QRH; but I certainly pushed them back out as I confirmed with the captain before pushing them back out in case the pitch trim issues came back. After pushing the pitch trim system 1 & 2 cut out buttons out; both auto pilot fail and pitch trim fail EICAS messages went away and our pitch trim indication came back along with pitch control. I reached the end of the QRH we gave ATC souls and fuel remaining and we got vectors for the ILS XY. We kept the auto pilot off and configured the aircraft for a flaps five landing. At one point we had a distant rate of about 1300 fpm and glide slope aural alert; the captain corrected immediately and when I looked up we were 2 red 2 white on the PAPIs. Rest of landing and taxi was uneventful.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.