Accident Narrative
Witnesses reported that following takeoff from a river, the aircraft climbed to approximately 100 to 400 feet above the water. It then initiated a left turn estimated at 45 degrees of bank. According to the majority of witnesses, after the aircraft had turned about 180 degrees, its nose abruptly dropped and it impacted the water. No witnesses reported any evidence of problems with the aircraft before impact, nor did they hear abnormal engine sounds or sudden changes in engine pitch.
Post-Accident Examination
Upon water impact, the aircraft became inverted and its cabin submerged. Efforts by witnesses to gain entry into the cabin to render assistance were unsuccessful due to aircraft damage. Rescue divers later found all four occupants deceased in the aircraft. The divers were able to remove the two rear-seat victims without undoing any passenger restraints. Autopsies disclosed that all four aircraft occupants had drowned.
Post-accident examinations of the wreckage found no evidence of pre-impact aircraft or engine malfunctions. However, investigators did find that a cabin entry door was jammed shut from impact damage, and the range of travel of both pilot doors was restricted by damaged aircraft components.
Probable Cause
The official probable cause was the pilot's failure to ensure attainment of adequate airspeed prior to initiating a steep turn at low altitude, resulting in an accelerated stall. A factor contributing to the occurrence of the accident was the aircraft's low altitude. Factors contributing to the severity of the accident included a water impact, and jammed/restricted doors due to impact damage resulting in degraded aircraft evacuation capability.