Raytheon Aircraft Company A36 N207PC accident near Enumclaw, Washington

Probable cause

A total loss of engine power due to oil starvation as a result of a loose oil line B-nut.

NTSB analysis

The pilot was at cruise altitude en route on a cross-country flight from Arizona to Washington when he noted that the engine oil pressure indicated zero and the manifold pressure was near zero. He then heard “…a loud bang, as though the engine had thrown a rod.” The cabin filled with smoke and oil covered the windscreen, and the pilot conducted a forced landing into a stand of trees, during which the airplane sustained substantial damage.

Examination of the airframe revealed no anomalies that would have precluded normal operation. An examination of the engine revealed three holes in the crankcase, each consistent with an internal engine failure. All six cylinders remained attached to their respective cylinder bays; there was no indication of impact damage. The Nos. 2, 4 and 5 connecting rods had separated from the crankshaft. All rod bearings displayed lubrication distress consistent with oil starvation. The oil line B-nut attached to the turbocharger scavenge check valve was loose.

Based on the available information, it is likely that the loose oil line B-nut resulted in a gradual loss of oil during the long cross-country flight, which subsequently resulted in the separation of the connecting rods due to oil starvation and a total loss of engine power.

Text from the NTSB. Open the NTSB docket for WPR18LA098 for the full record.