What happened
On March 24, 2017, a Quest Kodiak 100 (registration JA02TG), operated by Setouchi SEAPLANES, Inc., experienced an accident during a water takeoff in Beppu Bay, near Beppu City, Japan. The flight was part of a return trip to the company's base in Onomichi City.
As the aircraft accelerated during its takeoff run from the water, it encountered crossing swells. The aircraft experienced two distinct bounces; the first occurred at approximately 23 knots, and the second at 38 knots. The impact from the second bounce was severe enough that the pilot elected to reject the takeoff. During the subsequent deceleration, the aircraft continued to bounce several times due to the sea state. The aircraft eventually returned to port via water taxiing, but a post-flight inspection revealed substantial damage to the engine firewall, the forward fuselage, the engine mount, and the float struts and hardware.
The investigation
The JTSB investigation examined flight data from the aircraft's Integrated Instrument System, which revealed that the aircraft's pitch angle was unstable from the start of the takeoff run, fluctuating between +10º and +16.84º. The data also showed a roll angle of -7.34º (left wing down) immediately prior to the rejected takeoff.
Investigators analyzed the sea conditions, noting that while wind waves were within operational limits, the presence of crossing swells likely caused the pitching motion. The investigation also reviewed the company's training protocols and operational manuals regarding swell management and water takeoff procedures.