Accident Overview
On September 15, 2023, at about 1058 Pacific daylight time, an experimental, amateur-built Seawind 3000 amphibious airplane, registration N57TJ, was substantially damaged during a takeoff accident on Lake Sammamish near Bellevue, Washington. The pilot sustained fatal injuries, and the passenger was seriously injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Witness Observations
Multiple witnesses reported seeing the airplane depart from Lake Sammamish in a south-southeast direction. During the step phase of takeoff, the airplane was observed skipping on the water three times before pitching up, banking to one side, and impacting the water. Several witnesses noted that the engine sounded normal throughout the sequence.
One witness, a pilot of another amphibious airplane, described the takeoff as initially normal. The airplane reached step speed and was near takeoff velocity when it encountered three large wakes or waves. The first two waves caused significant bounces, lifting the airplane a few feet before it contacted the water again. Upon hitting the third wave, the airplane pitched up sharply, climbed approximately 30–40 ft, then nosed down at a 30–35° angle, struck the lake, and flipped inverted.
Video and Audio Evidence
A security camera recorded audio and video of the accident. The engine rpm increased shortly before the airplane entered the frame from the left. The video confirmed witness accounts of calm water near the shoreline, while a slow lake swell moved from left to right in the area where skipping occurred. A witness attributed the swell to boat activity near the south end of the lake.
Wreckage and Site Conditions
The accident site was near the middle of the lake. First responders noted multiple floating sections of the airplane and a fuel smell. The canopy, forward fuselage sections, and nose landing gear were initially present but were not recovered when the wreckage was towed by law enforcement the same day and retrieved from the water the following day. Postaccident examination revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation.
The forward seat lap belts remained attached to the airframe but were found unlatched and undamaged. The right forward seat shoulder harness was undamaged and still attached to the canopy ceiling panel. The left forward shoulder harness inertia reel and webbing were missing; the shoulder harness canopy mounting bolt remained attached to the left canopy ceiling.
During initial response, a diver reported that the pilot was secured only with the lap belt. Photographs from previous flights showed the pilot not wearing a shoulder harness on several occasions.
Engine and Flight Data
An Electronics International Inc. MVP-50P panel-mounted engine display was removed and downloaded by the NTSB Vehicle Recorder Laboratory. Data covered the entire flight from 1053 to 1058. Although about 11 seconds of invalid data occurred for some parameters from 10:57:13.7 to 10:57:24.7, no other anomalies were noted. Airspeed increased from 0 to 60 knots over the final 15 seconds of the recording.
Handbook Information on Swell and Skipping
The FAA Seaplane, Skiplane, and Float/Ski Equipped Helicopter Operations Handbook notes that waves and swell add variables to water takeoffs and landings. Even small waves can cause pounding or overturn risk. When swell is not aligned with wind, pilots must balance swell hazards against crosswind limits and experience. Skipping can occur when crossing boat wakes while on step. Skipping produces vertical G-forces, distinct from porpoising. Corrective action involves increasing back pressure and power to prevent float contact, then establishing proper pitch and reducing power gradually.