A321
Human-Machine Interface; Other / Unknown
Aircraft Equipment Problem Critical; Inflight Event / Encounter Loss Of Aircraft Control
Aircraft Equipment Problem Dissipated; Flight Crew Regained Aircraft Control; General Maintenance Action
Aircraft; Human Factors
Initially we were cleared for the LDA PRM at 6;000 FT approaching the localizer we were cleared for a different approach and descend to 4;000 FT. After changing the approach and confirming 4;000 FT in the FCU; I selected Open descent but nothing happened so I disconnected the autopilot; and started the right hand turn. About half way through the turn the aircraft start an uncommanded roll to the left at about 4 to 5 degrees per second. I attempted to use the control stick to roll back to the right; but at first was unable to move the stick. After about 1 to 2 seconds it released and functioned normally for the remainder of the approach. At that point I tried to discuss the problem with the Captain. I noticed that he did not quite understand what had just happened; in addition I had noticed earlier in the flight that he was showing all the signs of fatigue. It was not until we were on the ground that I was fully able to get him to understand what had happened. The second occurrence was not until 10 FT above the ground. As I attempted to add about 1 degree nose up for the flare again the control stick was frozen; but this time in the pitch mode. Thrust was at idle; we were about 5 FT off the ground by this time with no uncommanded pitch or roll; so I elected to land the aircraft. At touch down the stick again released and functioned normally. After arriving at the gate Maintenance was called out to the aircraft; both the Captain and myself were not sure how to write the problem up in the logbook. After describing the problem they suggested to write; 'First officers Joystick was not engaging'. Once at the hotel I called Maintenance Control to check on the history on this problem and was told there was none. I described the problem and asked if the write up was the correct one and was told she did not know at which point she hung up. In the morning I called the Chief Pilot's Office; to discuss what happened and discovered that only a flight control check had been done that night and the aircraft was flying at that moment. I was contacted later in the day; in that discussion and the way the stick felt was most like the magnetic stick lock out had somehow engaged while manually flying.
The reporter describes the magnetic stick lockout as an autopilot component that increases stick resistance to movement with the autopilot engaged and causes autopilot disengagement annunciations when it is over ridden. No autopilot annunciations were received at anytime during the approach and landing. The aircraft flew one leg the next day without any issues. The reporter's persistence resulted in the side stick controller being removed from the aircraft to be tested by the manufacturer.
A321 First Officer experiences a momentarily frozen control stick in the roll axis while flying manually during approach. During the landing flare the stick again freezes momentarily in the pitch axis and releases at touch down.