What happened
A certificated airline transport pilot was conducting a personal flight under 14 CFR Part 91 to deliver wooden roofing shakes to a remote lodge. Shortly after takeoff, as the aircraft climbed to an altitude of approximately 200 to 300 feet, witnesses observed the airplane abruptly pitch up about 70 degrees and drift to the right. The aircraft continued a right turn while the nose momentarily lowered. During this period of slow flight, the landing gear was extended. The nose then pitched up again, the right wing dropped, and the airplane began a descent. One witness described the descent as the wings rocking back and forth like a card in the wind. The airplane ultimately impacted shallow water within an area of tidal mud flats. There were no fatalities reported.
The investigation
The post-accident investigation determined that the estimated gross weight of the aircraft at takeoff was 11,500.8 pounds, which was 1,400.8 pounds in excess of its maximum takeoff gross weight. Investigators were unable to calculate the airplane's center of gravity because the exact location and station of the cargo could not be determined. An examination of the aircraft showed no evidence of mechanical anomalies prior to the impact.