Regional Jet 700 ER/LR (CRJ700)
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 70; Flight Crew Total 9873; Flight Crew Type 6470
Time Pressure; Distraction; Situational Awareness; Training / Qualification; Workload
Aircraft Equipment Problem Critical; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Overcame Equipment Problem; Flight Crew Regained Aircraft Control
Aircraft
The Captain and I operated a ferry flight. The pre-departure and departure were normal. At an intermediate altitude prior to our cruise altitude we received AP TRIM ND caution message. Before the QRH was called for the caution message extinguished. The cruise; descent; and arrival were normal. The beginning of the approach was normal. We had the field insight and were given a visual approach. Just past the FAF with the aircraft configured for landing I disconnected the autopilot. At that point in time I felt like I had positive control of the aircraft and began using the yoke trim to trim the aircraft for landing. Everything felt normal to about 100 FT. At that point I tried to raise the nose for a landing attitude and was unable to bring the control column back. I briefly looked down to the floor for an obstruction or to see if I was at the full aft position which I was not. I then looked at the Captain's control column for an obstruction which there was none. I think at 50 FT I stated to the Captain I was unable to pull back or flare. He immediately grabbed his yoke and we were both pulling back. With the nose low attitude I added a little thrust to arrest our descent. At that point I felt the control column break free and move aft of its' prior position. I immediately reduced the thrust to idle; set a landing attitude; and touched down at a normal rate in the touchdown zone. The rollout and exit from the runway were normal. After exiting the runway the Captain asked if I heard a loud thud coming from the back of the aircraft when we regained control. I did not hear the noise. He then asked for another control check with the flight control synoptic page on the EICAS. I completed the check with no abnormalities in the flight controls. The taxi in and parking was normal. The post flight walk around did not show any damage to the elevator or tail section of the aircraft. With the low altitude and the speed at which everything happened I would find it hard to avoid this event. Without the quickness of the Captain helping me pull back on the controls I think the outcome could have been different.
The Reporter stated that Maintenance determined a failed autopilot elevator servo locked the elevator cable which he and the Captain mechanically overrode with their joint elevator control column pull. The AP TRIM caution light earlier in the flight was probably when the failure occurred. The servo is used by both the autopilot and the flight crew trim switches. The Reporter felt that for a short period of time the aircraft was out of control but with the Captain's assistance the landing outcome was successful.
A CRJ-700 First Officer was unable to flare the aircraft just prior to landing because of a failed autopilot trim servo but mechanically overrode the locked servo with the Captain's assistance.