Piper PA 46-310P N9133G accident near Redmond, Oregon

Probable cause

A loss of engine power during cruise flight for reasons that could not be determined because postaccident examination of the engine did not reveal any anomalies that would have precluded normal operation.

NTSB analysis

The private pilot reported that, about 30 minutes into the private, cross-country flight and while the airplane was cruising at 23,000 ft mean sea level, the engine started running roughly. The pilot noticed that the No. 5 cylinder head temperature (CHT) was lower than normal. He cycled the magnetos and noticed that the engine ran rougher than normal when the left magneto was selected. He then enriched the mixture, and the engine smoothed out. He continued to monitor the engine and adjust the mixture. About 30 minutes later, the engine lost power. The pilot diverted to a nearby airport and attempted to line up for a runway but did not have sufficient altitude. He performed a forced landing to the airport infield, which resulted in the nose landing gear collapsing and structural damage to the wing spar.

Postaccident examination of the engine did not reveal any anomalies that would have precluded normal operation. During an engine test run up to full power, the only anomaly noted was that the No. 5 CHT was 50 to 70° lower than all the other cylinders. However, the lower CHT likely would not cause a loss of engine power.

Text from the NTSB. Open the NTSB docket for WPR15LA137 for the full record.