Continental Airlines Flight 99

During a near maximum gross weight takeoff from runway 4L, in gusty winds, the captain recalled that the airplane's rotation was normal, but it did not "fly away" as he expected. As the captain continued to rotate the airplane, the tail section struck the ground, and the "tail strike" EICAS (Engine Indication and Crew Alerting System) message illuminated. The flight crew then completed the takeoff sequence, completed all checklists, jettisoned fuel, and returned to the airport where an uneventful landing was made. The winds recorded at the airport, about 1 minute after the accident, were from 280 degrees, at 21 knots, gusting to 28 knots. Review of the DFDR data revealed that at the time the takeoff roll began, the captain's control wheel was turned 25.5 degrees to the left, resulting in the upward deflection of the left wing outboard aileron, flaperon, and 6 of 7 spoilers, which was consistent with a correction for crosswind conditions. As the takeoff roll continued, the control wheel input varied between 19.6 degrees and 37.5 degrees to the left, and at the approximate point of rotation, the control wheel was turned to the left 38.4 degrees. The control column position also began to move aft at the point of rotation, with a force of 22.7 pounds, and the pitch of the airplane rose to 3 degrees nose up. As the pilot continued the rotation, he held the pitch control at a value consistent with previous recorded flights, before pulling the control column further aft, increasing the pitch angle to the tail strike attitude of approximately 13 degrees nose up. One second later, as both left and right main gear indicated no weight on wheels, the control column position reached its maximum value during the event, 9.2 degrees aft, and the pitch reached 17.8 degrees nose up. A Safety Board vehicle performance study compared the airspeed and groundspeed recorded during the accident, and determined that a wind gust caused an approximate 7 knot loss in airspeed, the lateral control wheel input during the rotation ranged from 24 to 37 degrees, and the maximum pitch rate during the rotation was approximately 6.0 degrees/second. Using these data in a Boeing estimation method, it was determined that three factors contributed to the reduced tail clearance during the takeoff. These factors were the loss of airspeed that resulted from a tailwind gust during the rotation, the loss of lift that resulted from the deflection of the lateral control surfaces, and a pitch rate in excess of that recommended. These factors combined for a total reduction in tail clearance of approximately 150-170 percent. It was concluded in the performance study that reducing the pitch rate to the Boeing recommended 2.5 degrees/second would have brought the tail clearance reduction to the 80 percent to 100 percent of nominal level, and from that point, a 1-knot increase in rotation speed would have provided about a 7 percent increase to the tail clearance margin. According to Boeing, the typical liftoff attitude was 8.5 degrees, the minimum tail clearance was 37 inches, and the tail strike pitch attitude was 12.1 degrees up. The operator's flight manual warned pilots to "Avoid any tendency to rapidly rotate to a 10 degree pitch attitude and hold it until lift-off. This technique invites a tail strike." In addition, neither Boeing, nor the operator, had procedures or policies for adding an increase in rotation speed to compensate for crosswind or tailwind conditions.

Verbatim NTSB analysis and probable cause from the NTSB dataset