ANC04LA050 · Cessna U206F

The commercial certificated pilot was departing a remote gravel runway, located adjacent to a rocky beach, on an on-demand air taxi flight. The airplane was equipped with a short takeoff and landing (STOL) modification. The STOL installation droops the ailerons about 16 degrees as the flaps are extended. The pilot said he lowered the airplane flaps to 20 degrees and applied full power for a short field takeoff with the control yoke aft. As the airplane gained speed, the pilot said the nose of the airplane rotated to about 10 degrees above the horizon, and the main landing gear tires lifted off the runway surface. About 3 feet above the runway, the airplane suddenly rolled to the left. The pilot applied right aileron and right rudder to stop the roll, without affect. The left wingtip collided with small rocks along the beach about 800 feet from the beginning of the runway, and the airplane swerved about 30 degrees to the left. The airplane came to rest on a rocky beach, about 150 degrees to the left of the runway centerline. The pilot said the engine was producing power throughout the event. He did not report any aileron control problem. Postaccident photographs of the accident scene and the airplane revealed that the left wing was bent upward at the tip. The right wing was bent upward about midspan. A view of the aft side of the airplane revealed that the left wing flap was extended slightly. The right wing flap was extended about one-half of its range. The airplane was recovered by insurance and company personnel, and transported to the operator's facility. The wings, rudder, horizontal stabilizer, and the elevator were removed for transport. Postaccident examination of the wings by the NTSB investigator-in-charge revealed no observed mechanical malfunction of the internal flap and aileron control mechanism within each wing. Since the wings were removed for recovery, the rigging of the aileron and flap cables could not be established. The right front seat passenger was recording the flight on a hand-held video recorder. Review of a copy of the video tape revealed that the airplane was taxied at a fast pace toward the departure end of the runway. The airpane made a rolling "U" turn, did not slow or stop, and the pilot applied full power. As the airplane lifed off, it almost immeditely rolled to the left and collided with the ground. The video does not record any sound of a stall warning horn, or a view of the flap handle position. The elapsed time from application of full power for takeoff, until the left wing collided with the ground, was about 17 seconds. Following the accident, additional video from the passenger's camera recorded the position of the airplane at the point of rest. The video showed that the left flap appeared to be slightly extended. The right flap appeared extended about one-half of its normal travel.

Verbatim NTSB analysis and probable cause from the NTSB dataset