CRJ700 flight crew experiences a Master Caution Autopilot Pitch Trim followed by a Master Caution Autopilot ND Trim message shortly after engaging the autopilot at 600 FT AGL. When the First Officer disengages the autopilot the aircraft pitches up aggressively and a track deviation from the RNAV procedure occurs; resulting in loss of separation.
Synopsis
CRJ700 flight crew experiences a Master Caution Autopilot Pitch Trim followed by a Master Caution Autopilot ND Trim message shortly after engaging the autopilot at 600 FT AGL. When the First Officer disengages the autopilot the aircraft pitches up aggressively and a track deviation from the RNAV procedure occurs; resulting in loss of separation.
Narrative
After takeoff on Runway 8R on the Cokem 4 departure I selected Speed Mode and Nav Mode and at 600 FT the auto pilot was turned on. FMS2 was armed in the FMA. The autopilot was also active. While I was running the after takeoff checklist we received a Master Caution Autopilot Pitch Trim followed by a Master Caution Autopilot ND Trim message. We were trying to determine what may have been causing these messages because all the trims were in the green. I was getting the QRH and turning to the automation section and my First Officer turned off the autopilot. The aircraft pitched up abruptly. My First Officer then re-trimmed the aircraft. When I found the pages I noticed that we were right of course. I looked to see what the flight director was showing. It showed wings level and the FMS2 were active in the FMA but we were still right of course. HRSHL was active as the next waypoint. I told my First Officer to turn towards HRSHL. At that point ATL Departure asked if we were navigating to HRSHL. I told them yes we were turning and we had a problem. Then they gave a heading of 360. We turned left to heading 360. We now ran the QRH and then reselected the auto pilot on. [We] then received a Master Caution AP Trim LWD message. Again ran the QRH and then reselected the auto pilot on. Then it worked normally. This all happened in less than 2 minutes ATC then asked us to call when we landed due to a possible loss of separation. The threats were the auto pilot caution messages just about the time we should have been turning towards HRSHL. The errors were the FMS and auto pilot not locking on to the desired flight path and us not catching it because we were distracted by the caution messages. I have to disagree with the auto pilot on procedure at 600 FT for RNAV departures. I think gives us a false sense of security. I think by hand flying your paying closer attention to what the aircraft is suppose to be doing. You know coming out of ATL on a RNAV departures your going to turn shortly after takeoff.
Second reporter narrative
After the positive rate call I commanded the Captain (pilot not flying) for speed and NAV mode; and then at 600 FT AGL called for autopilot on. This is the preferred method to use when departing ATL via a RNAV departure. Just a few seconds after the autopilot was engaged a master caution AUTOPILOT PITCH TRIM was displayed. It immediately cleared itself; but reappeared and cleared itself again. This process went on for three or four times; and during this time a second master caution items was displayed as AUTOPILOT TRIM IS ND. I now had two master caution messages being displayed that pertained to the autopilot just after takeoff. I firmly believed that the aircraft was flying in speed mode accelerating to 250 KTS; in NAV mode flying the COKEM FOUR Departure to HRSHL. I took my focus away from the PFD and MFD to see exactly what were the two master cautions pertaining to the autopilot; and what was the condition of the aircraft's three trim settings. By doing this I had a better understanding of what the malfunction might be; and what the aircraft might do unexpectedly while conducting a departure. I told the pilot not flying that I was going to disconnect the autopilot and hand fly the aircraft until we could run the QRH and correct the problem. When I disconnected the autopilot it aggressively pitched up to where I had to apply a good amount of force on the controls to bring the aircraft back in a normal attitude and into the command bars. This was when I looked at the PFD and MFD and saw that the aircraft was in the command bars; but we were right of course to HRSHL on the COKEM Departure. It took me a few seconds to process what was going on since what I commanded the aircraft to do; and what the aircraft was doing and displaying were two separate things. Also; the command bars were not turning towards HRSHL; I didn't see any CDI deflection towards the left; and I believe that FMS 2 was displayed. It was at that time that the pilot not flying said why are we right of course to HRSHL. Departure then called us and asked if we were we turning to HRSHL or why were we not turning to HRSHL. The pilot not flying stated that we had a problem and ATC gave us an immediate turn to heading 360. The Flight Attendant working 'A' then called us to see if everything was O.K. since she heard the several caution chimes just after takeoff and the aggressive pitch up of the aircraft. The QRH was then performed once back on the RNAV departure; and Dispatch and Maintenance were notified of the two earlier master caution messages that no longer existed while in flight. The remainder of the flight was uneventful. Once on the ground the autopilot caution messages were written up in the AFDL; and ATL Departure Control was contacted.I never saw the aircraft proceeding right of course during the time of the initial caution messages appearing until I disengaged the autopilot and was back inside looking at the MFD and PFD. Prior to this I believed that the aircraft was flying in speed; NAV mode; with autopilot on flying the departure. I never saw any aircraft off to my right which we had a loss of separation with and never had any TCAS advisory or RA; but this could have been muted due to our low altitude at the time if an advisory or RA was to be activated.Things did seem to be moving very quickly during this short period of time; and we were focused on the autopilot caution messages with it still engaged and I didn't undue this focus until I disengaged the autopilot. Now I can second guess myself by stating that had I been hand flying the aircraft I would have never received any autopilot caution messages; and I would have been flying the aircraft while being more heads down in the PFD and MFD and would have detected any deviation of course. Either way I still would have called for autopilot on at 600 FT that day since I was on day four of flying and this was leg 13 of 16 for the trip.
More incidents for this aircraft family →
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.