CL65 flight crew reports autopilot malfunction during coupled ILS approach below 300 feet AGL. Autopilot was disengaged and missed approach initiated; the second approach was uneventful with autopilot engaged.
Synopsis
CL65 flight crew reports autopilot malfunction during coupled ILS approach below 300 feet AGL. Autopilot was disengaged and missed approach initiated; the second approach was uneventful with autopilot engaged.
Narrative
Established on the ILS CAT 1 approach RVR 2200 feet. Configured Flaps 45 before landing check 2 miles from the outer marker. Over marker Captain called the marker and altitude crossing and I responded altitude checks no flags as per our procedures. I called 500 above DH; at 400 above we both noticed a yellow A blink on the PFD. At 300 I called approach lights continue. At that time the localizer turned yellow and needle move slightly to the right. EICAS message autopilot pitch trim RWD appeared I and the Captain called missed approach. He disconnected the autopilot executed the published missed approach and at that time while he turned the autopilot off the plane suddenly banked 30 degrees to the left. The shaker went off for a second since we were at 141 Vref and in a bank. I advised ATC missed approach and the tower gave us heading 180 and maintain 3000. They asked for the missed approach reason and I told the tower equipment malfunction. I did all the climb; 10000; cruise check; reviewed the QRH for the autopilot trim RWD message; talked to flight attendants and passengers and we did the descent approach checks and ATC vectored us to an ILS to a normal approach and landing.
Second reporter narrative
All required checklist were completed before out final vector to intercept. Gear was down and flaps were at 45 degrees (full) approximately 2 miles from the outer marker. Over the outer marker we confirmed our altitude checked and there were no 'Flags' or abnormalities and cross checked. First Officer made the standard 500 FT above DH call and I noticed an 'A' on my MFD come on and then go off. 'A' = Aileron Trim. The autopilot then felt it was having difficulty holding the airplane on course and at the 200 FT above DH call the localizer blinked green (normal on course) to yellow (off course). When this occurred I clicked the autopilot off. When I did this the airplane jerked and banked approximately 20 to 30 degrees to the left. While I quickly brought the aircraft back to wings level and back on runway heading the stick shaker momentarily went off while we were advancing the thrust levers to max thrust for a go-around. Our go-around and missed approach was normal and in accordance with ATC's instructions. Aircraft was cleaned up and all checks were again completed and we landed uneventfully in the ILS. Upon shutdown our maintenance was notified.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.