Primary finding
Probable cause
The pilot’s loss of control during initial climb for reasons that could not be determined.
Investigator assessment
Analysis narrative
The pilot stated that moments after takeoff from a lake he heard a loud bang, and the airplane impacted the water. The passengers stated that after takeoff there was a sound similar to a cable snap or a hammer hitting metal. The airplane made a hard left turn, and the left wing impacted the water. Postaccident examination of the engine and airframe revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. The airplane came to rest fragmented in a lake and the floats were not recovered; therefore, the fly wires and floats could not be examined, and the reason for the loss of control could not be determined.
Source record
Factual narrative
On July 12, 2023, about 1630 Alaska daylight time, a DeHavilland DHC-2 airplane, N302BL, was substantially damaged when it was involved in an accident near Twin Hills, Alaska. The pilot was not injured, two passengers sustained minor injuries, and two passengers sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 business flight. The pilot stated that just after takeoff from the water, he heard a “bang” and then the airplane impacted the water. The passengers reported hearing a sound similar to a “cable snap” or “hitting a hammer on a piece of metal.” The airplane made a hard left turn, the left wing dipped into the water, and the airplane pivoted around that point. The airplane came to rest mostly submerged and fragmented. Postaccident examination of the airplane revealed the left wing was separated from the fuselage, consistent with impact damage; the right wing was removed to facilitate recovery. Flight control continuity was confirmed from the cockpit inputs to the recovery cuts. The left flap attachment arm remained attached to the flap and was bent and twisted. The right flap attachment arm was undamaged. The fuel selector was set to the aft tank. The floats and fly wires were not recovered from the lake and therefore were not available for examination. The throttle control was near the closed position, and the mixture was at idle. The spark plug attachments and cylinder base nuts were all intact and tight. When the propeller was manually rotated, thumb compression was obtained on all cylinders. The cylinders were examined using a lighted borescope and no anomalies were noted. All magneto leads produced a spark when spun with an electric drill. A review of the maintenance logbooks revealed that the engine had accumulated 66 hours since an overhaul that was completed about 6 months before the accident.