LOT Polish Airlines Flight 2 Overspeed and Stick Shaker Incident

Incident Overview and Immediate Response On 19 June 2009, LOT Polish Airlines Flight 2, a Boeing 767-300 with registration SP-LPA, was en route from Chicago O'Hare International Airport to Warsaw, Poland. While in level cruise near North Bay, Ontario, the captain's airspeed indicator suddenly rose above the maximum operating speed, triggering an overspeed warning. The flight crew reduced thrust to flight idle and initiated a climb, which temporarily stopped the warning. However, the captain's indicated airspeed increased again, causing a second overspeed warning. As the crew responded, the stick shaker also activated. During the event, the aircraft climbed from 33,000 to 35,400 feet above sea level before descending to approximately 27,900 feet. The crew diverted to Toronto/Lester B. Pearson International Airport, where the aircraft landed safely. No damage was reported, and none of the 10 crew members or 206 passengers were injured. ## Sequence of Events The aircraft was cruising at flight level 330 in instrument meteorological conditions with light to moderate turbulence. The captain was the pilot flying, with the autopilot and autothrottles engaged. At 2203 Eastern Daylight Time, the captain's airspeed indicator increased from 276 to 320 knots, and the altimeter rose 450 feet in about five seconds. The autopilot initially commanded a pitch-down input, and an overspeed warning activated. The captain retarded the throttles to idle, causing the autothrottles to disconnect while the autopilot remained engaged. The autopilot then pitched down further before pitching up approximately 8 degrees. The overspeed warning remained on for about 41 seconds. The captain disengaged the autopilot and manually initiated a climb at idle thrust. The captain's airspeed indicator decreased to 297 knots, but as the captain increased pitch to 12 degrees nose-up, the indicated airspeed rapidly rose to 324 knots, producing a second overspeed warning. The aircraft climbed to about 35,400 feet before beginning to descend. The captain's indicated airspeed reached a maximum of 339 knots before decreasing. While descending through 34,700 feet, the captain's airspeed was decreasing through 321 knots when the stick shaker activated. The overspeed warning remained on for 20 seconds, became intermittent for 26 seconds, and then stopped. The stick shaker activated intermittently for about 1 minute and 50 seconds. As the aircraft descended through approximately 30,000 feet with the captain's airspeed indicating 278 knots, the captain increased thrust, and the stick shaker stopped within nine seconds. The captain's airspeed then rapidly decreased from 255 to 230 knots, and the fluctuations ceased. The aircraft continued descending to 27,900 feet. Throughout the event, the first officer's airspeed indicator did not show an overspeed condition. ## Diversion and Post-Landing Findings The crew informed air traffic control of the overspeed and altitude-maintenance problems and requested to divert to Toronto. They also indicated a need to dump fuel but did not declare an emergency. No further anomalies were encountered for the remainder of the flight. To reduce landing weight, fuel was dumped en route; because the aircraft could only dump fuel from its center tank, the crew requested a hold to burn off fuel. During the hold at 10,000 feet, the autopilot was engaged but the autothrottles were not. The crew manually reduced thrust to idle, and the autopilot commanded increased pitch to maintain altitude. At 7.6 degrees nose-up, the stick shaker activated. As the aircraft descended to about 9,600 feet, the crew manually increased thrust, with a maximum of 111% recorded on the flight data recorder, and the aircraft began to climb. The autopilot was disconnected while climbing through 9,860 feet. The aircraft continued climbing to 10,500 feet, resulting in a loss of separation with another aircraft, which responded to a Traffic Collision Alerting System Resolution Advisory. Air traffic control was aware of the altitude deviation and inquired about the problem. After landing, the crew completed an aircraft technical report noting the overspeed indication, unusual buffet, vibration, stick shaker, stall, contradictions between the captain's and first officer's airspeed indicators, and left and right Electronic Engine Control illumination on the Engine Indication and Crew Alerting System. No further EICAS messages were reported, and it could not be determined what EICAS messages were present during the event. Inspection found no structural damage and no faults in the air data system. The aircraft was released back into service. ## Subsequent Event On 21 July 2009, the same aircraft, with a different crew, was on a similar Chicago-to-Warsaw flight. About two hours into cruise at flight level 340, with the autopilot and autothrottle engaged, the captain's airspeed abruptly increased from 278 to 336 knots in about 11 seconds, and the captain's altimeter increased by 990 feet. An overspeed warning occurred; the crew reduced thrust and disconnected the autothrottles. Left and right EEC EICAS messages were displayed. The autopilot was disengaged, and the aircraft was flown manually. The crew noticed a discrepancy between the captain's airspeed indication and both the first officer's and standby airspeed indicators, and completed the AIRSPEED UNRELIABLE checklist. The overspeed warning, which lasted about 3 minutes and 20 seconds, stopped when the captain changed the selected Air Data Computer from normal to alternate. The captain's altitude indications returned to normal and remained normal for the rest of the flight. Unlike the 19 June 2009 occurrence, the aircraft did not pitch nose-up and there were no stick shaker activations. The EICAS messages received during this event were: Overspeed; Autopilot; EEC L; EEC R; Aileron Lockout; and Rudder Ratio.