1991 Interflug A310 incident

On February 11, 1991, an Interflug Airbus A310 operating a flight from Berlin to Moscow completely lost the crew's control for a short time due to a conflict between the pilots' actions and the autopilot's logic. For over six minutes, the airliner performed uncontrolled, sharp climbs and dives, stalling into a steep bank four times, before the pilots managed to regain control and land the plane safely. No one was injured.

Incident

On the morning of February 11, 1991, the plane departed from Berlin Schönefeld Airport bound for Sheremetyevo Airport in Moscow. A few minutes before 11:00 AM, the Airbus A310 began its approach to land on runway 25L at Sheremetyevo Airport. The approach was being conducted automatically under air traffic control guidance. The crew was routinely preparing the aircraft for landing, and the first officer had set the prescribed go-around altitude of 3,580 feet on the autopilot. With flaps and slats extended, the plane was nearing the touchdown point when, at an altitude of 1,550 feet, the controller instructed them to go around due to the runway being occupied. At 10:56, the pilots activated the go-around mode by pressing the corresponding buttons on the thrust levers, retracted the landing gear, adjusted the flap setting, and changed the selected go-around altitude to 1,640 feet as instructed by the controller.

As later revealed by flight recorder data, the automatics began a standard climb. However, 41 seconds later, the captain felt the pitch-up angle was too steep. Believing he was disengaging the autopilot, he attempted to lower the aircraft's nose by pushing the control stick forward. In reality, the autopilot remained engaged and interpreted the force on the stick as a command to trim the stabilizer, consequently driving the trim tab in the opposite direction. After the selected go-around altitude was reached, the autopilot automatically disconnected due to the sustained force on the stick, but the pilots did not notice this. Continuing their attempts to correct the aircraft's attitude, they ignored the visual and aural alerts in the cockpit. The aircraft entered an uncontrolled regime: with engines running at takeoff thrust, it began to climb almost vertically at an alarming rate. At 10:57:17, having reached 5,580 feet, the aircraft lost speed and stalled, banking left before entering a steep dive. At 10:57:46, at 1,487 feet, it transitioned back to a climb, reaching 5,787 feet 29 seconds later before stalling again, this time banking left. At 10:58:40, at 1,775 feet, the nose pitched up once more, surging to 7,355 feet in 31 seconds, then stalling into a right bank. In total, over six minutes and ten seconds, the aircraft stalled four times, coming close to inverting. Only after the pilots intuitively reduced engine thrust and inadvertently changed the trim setting did they regain control. At 11:03, the aircraft was once again responsive to the crew's inputs, and at 11:05:58, the pilots took full manual control and landed the plane safely at Sheremetyevo. As all passengers and crew were buckled in, no one was injured.