Accident Overview
A single-engine turboprop airplane, operated by a private pilot on a multi-leg ferry flight to Brazil, experienced a total loss of engine power while cruising at 27,000 feet over open water. The pilot opted to fly direct from the departure airport in Puerto Rico to the destination in Grenada, rather than following the island chain and remaining within power-off gliding distance of the shore. At the time of the power loss, the aircraft was approximately 119 miles west of a suitable landing area.
Flight Details
During the cruise, the engine torque indication dropped from the cruise power setting to zero foot-pounds. Subsequently, the engine began to vibrate and smoke emanated from the engine. The pilot ditched the airplane, which subsequently sank and was not recovered. Both the pilot and a pilot-rated passenger were rescued by a French Navy helicopter.
Operational Considerations
According to the pilot, the decision to take a direct route instead of staying closer to the island chain was based on experience ferrying three similar airplanes to Brazil in the previous year. He described it as a judgment call and a calculated risk, given the engine's perceived reliability. However, at the planned operating altitude of 27,000 feet, the aircraft could have glided about 54 miles. Had the route been optimized to take advantage of this glide distance, the pilot could have remained closer to the island chain while not following a direct path.
Fuel and Weight Issues
Review of fueling documentation, the Pilot's Operating Handbook (POH), and statements from the pilot and passenger revealed several deviations from good operating practices. The aircraft was fueled to capacity without the addition of a fuel icing additive, despite the planned high-altitude operation at 27,000 feet. Additionally, the airplane was operated in excess of the manufacturer's published weight limitations. No power setting or performance data were available for operations beyond these limitations.
Power Setting Discrepancies
Before the engine failure, the pilot reported a torque setting of approximately 937 foot-pounds, while the pilot-rated passenger noted about 980 foot-pounds. Both values exceeded the maximum torque limit listed on the maximum cruise performance chart in the POH and Airplane Flight Manual (AFM). Operating the engine beyond recommended power settings for a prolonged period can lead to accelerated deterioration of hot section components, affecting reliability and durability.
Probable Cause
The official investigation determined that the total loss of engine power during cruise flight occurred for reasons that could not be identified because the airplane was not recovered. Contributing to the accident were the pilot's failure to comply with airplane and engine limitations and his decision to fly over water beyond power-off gliding distance from shore.