Accident Sequence
A float-equipped airplane was observed taking off in light winds and calm water conditions. The aircraft achieved a steep climb and adopted a nose-high attitude. Witnesses reported hearing no reduction of engine noise from takeoff power to climb power. At an altitude of approximately 200 feet above the water, the airplane entered a steep left bank, then rolled rapidly to the right and impacted the water at a steep angle.
Aircraft Modifications
The airplane had been modified with a Short Take Off and Landing (STOL) kit. Certification flight tests determined that this modification eliminated aerodynamic warning of impending stalls, requiring the installation of an audible stall warning system. The tests also required the addition of a ventral fin and horizontal stabilizer finlets to meet directional stability certification. The least stable condition was identified as the takeoff flap configuration during climb.
Required Equipment
The Supplemental Type Certificate (STC) for the modification mandated installation of the ventral fin and an audible stall warning system. Despite this, the manufacturer produced a marketing video prior to STC approval that stated the stall warning system was not required in the U.S. The company indicated this video was used for training and served as a basis for pilots routinely disabling the stall warning horn by pulling the circuit breaker.
Accident Aircraft Configuration
At the time of the accident, the airplane did not have the ventral fin installed. The takeoff flaps setting was selected, and the audible stall warning circuit breaker was found in the pulled (disabled) position. The local FAA Flight Standards Office had inspected the accident airplane 14 times in the previous 29 months and made no mention of the missing ventral fin.