CHI94DEM01

The aerial application flight had completed one pass over a field and was making a climbing turn in preparation for a second swath run. During the climbing turn the pilot reported the engine quit with a loud bang while over a lake next to the area being sprayed. The pilot said he turned toward shore and rapidly decelerated. He said he pitched the airplane down to keep it from stalling. The airplane descended in a steep nose down attitude until reaching an altitude at which the pilot flared the airplane for landing. After landing in the water the airplane nosed over and sank. The on-scene investigation revealed the turboprop engine's combustion chamber had ruptured and that it did not have a negative torque sensing system that would allow the propeller to feather when the engine failed. The airplane was not equipped with a manual propeller feathering system.

On June 2, 1994, at 0610 eastern standard time, a Grumman G-164A, N8939H, registered to Maurice's Flying Service, Incorporated, of Lakeview, Michigan, and piloted by a commercially certificated pilot, was substantially damaged during a collision with water after a pilot reported engine failure. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 137 flight was not operating on a flight plan. The pilot reported no injuries. The flight departed Lakeview, Michigan, at 0540 est.

The pilot stated he surveyed a site for aerial application at the Muskegon State Park, Muskegon, Michigan. The park is located on the northwest side of Muskegon Lake. He said he made one pass from the west to east, pulled up and turned left over the lake. At 400 feet above the lake, and about one-quarter mile from shore, the engine quit with a loud bang. The pilot said he set up a glide toward the shore of the park. He said he was thrown forward into the seat belts by sudden deceleration because the airplane seemed to stop in midair. The pilot said he pushed the nose down to keep from stalling. He said the airplane descended at a steep nose down attitude until he flared just above the water. The airplane hit the water, nosed over on its back and sank in about ten feet of water.

Post accident investigation revealed a ruptured combustion plenum chamber. This airplane was modified with an STC that allowed a turboprop engine to be installed on its airframe. The airplane's owner said that the STC did not incorporate a negative torque sensor to allow the prop to feather when the engine failed. Without the negative torque sensor installed the propeller governor would try to maintain the engine at 2,000 RPM by decreasing the propeller blade's pitch to the minimum stop. The airplane was not equipped with a manual propeller feathering system. According to the airplane's owner, N8939H was not equipped with a fuel shut off system that, when activated, would feather the propeller.