What happened
A single-engine airplane equipped with a Soloy engine conversion—which replaced a Continental TSIO-520 reciprocating engine with a Rolls Royce-Allison 250-C20S turbine engine—experienced a loss of engine power during a night instrument cross-country flight. While encountering icing conditions, the pilot was utilizing the engine deice system. Upon perceiving snow, the pilot selected engine alternate air. Shortly after this selection, the engine lost power.
The pilot-rated passenger feathered and secured the engine before the aircraft established a best glide speed. The pilot made multiple attempts to restart the engine but could not reach the 12 percent N1 required for a successful start. As the aircraft entered visual meteorological conditions, the pilot performed a forced landing in a gravel area.
The investigation
An examination of the engine revealed that the anti-ice line had separated from the compressor case. Metallurgical analysis showed that the mounting pad of the anti-ice line separated from the compressor case due to fatigue cracking. This cracking originated at a braze joint that exhibited oxidation.
Engine manufacturer and conversion representative data indicated that the broken line prevented heated air from reaching the engine inlet guide vanes, even when the deice system was active. When the pilot selected alternate air, the introduction of relatively warm air into the inlet dislodged accumulated ice, resulting in an engine flameout. Maintenance records showed the engine had received a 100-hour inspection approximately 29 hours before the accident. Additionally, the engine operations manual noted that thermal differences could cause the gas producing section to lock up after an in-flight shutdown, potentially requiring a wait of up to 10 minutes before a restart is possible.