ERA20LA134 · Maule MT-7 235

The pilot departed in the afternoon to complete a cross-country trip. He completed a brief stop at an intermediate airport, picked up a passenger, and then departed for the final destination under an instrument flight rules flight plan. The departure and en route phases of flight were routine and large portions of the pilot’s route were about 10 to 15 nautical miles from the shoreline over open water. About 1 hour into the flight, air traffic control instructed the pilot to proceed to an initial waypoint that was a part of a GPS instrument approach procedure at the destination airport; however, a descent clearance was not provided. About 13 minutes later, the airplane’s flight track showed a descending right turn spiral and radar contact was lost. No distress calls were received from the pilot. The wreckage was located on the ocean floor about 0.30 nautical mile from the last radar point and was not recovered. Photographs taken underwater revealed fragments of wing, fuselage, engine, propeller, and empennage in the same general area on the ocean floor. Although the engine was not examined, the propeller exhibited signatures that indicate the engine was producing power at the time of impact. Review of weather data and light conditions at the time of the accident revealed that the pilot was likely flying in instrument meteorological conditions (IMC) that were conducive to spatial disorientation; however, the pilot was current and qualified to operate the airplane at night in IMC. Although it is possible that the pilot experienced spatial disorientation and a subsequent loss of control, given that an autopsy, toxicology testing, and an examination of the wreckage could not be performed, the investigation was unable to determine the cause of the airplane’s turning descent into the water.

Verbatim NTSB analysis and probable cause from the NTSB dataset