What happened
On April 15, 2017, a privately owned Cessna T206H (amphibian), registration JA007P, attempted a water takeoff from Lake Shinji in Shimane Prefecture, Japan. The flight was intended to be a familiarization flight to Tottori Airport, carrying the pilot and one passenger.
During the takeoff run, the pilot noted that acceleration felt sluggish as the aircraft approached an area of rough water characterized by whitecaps. As the aircraft reached the step and prepared to become airborne, it struck a large wave. The impact caused the aircraft to pitch forward, leading the front of the right float to strike the propeller, which subsequently caused the engine to stop. Following the collision, the aircraft drifted downwind. During this period, the float separated from the fuselage, causing the aircraft to sink.
The investigation
The JTSB investigation examined the meteorological conditions, the aircraft's performance capabilities, and the pilot's decision-making process. Investigators noted that while the water near the pier was relatively smooth, wind speeds had increased significantly between the pre-flight inspection and the time of takeoff.
Analysis of the Pilot's Operating Handbook (POH) revealed that the required takeoff distance to clear a 50-foot obstacle under the aircraft's actual weight and conditions was approximately 812 meters. However, the pilot had planned for a much shorter takeoff run of roughly 300 meters. The investigation also looked at the sea state, noting that the wind velocity had risen to an average of 20 to 23 knots, which likely produced waves up to 2.4 meters in height—roughly three times the height of the aircraft's floats.
Findings
- The aircraft was operating at a high weight due to a full fuel load intended for a later destination.
- The pilot did not verify the required takeoff performance from the POH prior to the flight.
- The pilot failed to recognize that the necessary takeoff distance exceeded the available smooth water area.
- The pilot did not abort the takeoff run despite noticing decreased acceleration when approaching rougher water.
- Increasing wind speeds led to a sea state with waves too large for a safe water takeoff.