ERA10LA328 · Parks J L/Dreffin D SEAWIND 3000

The pilot of the experimental, amateur-build amphibian airplane was also the owner/builder. While descending through 6,000 feet mean sea level, a vibration developed in the elevator control. The pilot reduced engine power and the vibration decreased. When the pilot increased engine power, the vibration increased and he had to reduce engine power to a point where the airplane could not maintain altitude. The pilot subsequently performed a forced landing to water. The airplane touched down hard, which resulted in damage to the engine nacelle and empennage. A postaccident examination of the airplane revealed that approximately three-fourths of the elevator had separated in-flight. Metallurgical examination revealed that the elevator failed due to overstress, in the downward direction.

The pilot completed construction of the airplane about 3 weeks prior to the accident and the airplane had accrued 43 total hours of operation since its completion. The airplane was equipped with an empennage manufactured by a different manufacturer than that of the kit manufacturer, which was 49 percent larger than the kit empennage. Although the increased size did not add much weight, it added significant surface area, resulting in increased gust loads, with no added engineering to compensate for such loads.

The airplane's never exceed speed (Vne) was 230 mph (200 knots) and the maneuvering speed (Va) was 180 mph (156 knots). Review of a radar plot for the accident flight, overlaid on weather radar data, revealed that the accident airplane was traveling at a groundspeed of approximately 200 knots, in the vicinity of convective activity.

Verbatim NTSB analysis and probable cause from the NTSB dataset