Piper PA 32R-301 N35590 accident near Boulder City, Nevada

Probable cause

A total loss of engine power during cruise flight for reasons that could not be determined based on the available evidence.

NTSB analysis

The private pilot reported that, while in cruise flight during the personal flight, the engine started to "sputter" and lose power. During troubleshooting efforts, the engine lost total power. The pilot then attempted to restart the engine without success and subsequently initiated a forced landing on a nearby beach.

A postaccident engine examination revealed that the engine crankshaft would not rotate manually. Disassembly of the engine revealed evidence of wear and heat damage to the Nos. 1 and 2 crankshaft bearing halves. The oil filter contained no contaminants or metallic particles. No further evidence of a preexisting mechanical malfunction was noted during the examination of the engine and airframe.

Damage to main bearings can occur from multiple sources, including oil contamination, excessive loads, or disruption of the lubrication between the bearing face and the main journal. Given that the Nos. 1 and 2 bearings were the only damaged bearings throughout the engine, it is unlikely that oil contamination caused the damage. In addition, given that the Nos. 1 and 2 bearings are located in the forward area of the engine and experience lighter loads than those located in the aft area of the engine, it is unlikely that excessive loads caused the damage. Although a propeller strike could result in an abnormal loading and lubrication of the bearings, a review of the airframe and engine maintenance records revealed no evidence of a reported propeller strike.

Absent one of the above issues, it is likely that a disruption of the lubrication between the bearing face and the main journal resulted in the wear of the Nos. 1 and 2 bearing halves. However, no evidence of oil passage blockage, leaks, or excessive clearance between the bearings and the crankshaft journals was observed; therefore, the reason for the likely lubrication disruption or whether it caused the loss of engine power could not be determined. In addition, the accident bearings had an aluminum-tin intermediate layer, which makes the bearings less robust than those with a copper-alloy intermediate layer; thus, the wear and heat damage could have been preceded by delamination of the aluminum-tin intermediate layer. However, postaccident examination could not determine whether this occurred.

Text from the NTSB. Open the NTSB docket for WPR15LA196 for the full record.