Beech N35 N671VC accident near Phoenix, Arizona

Probable cause

A loss of engine power due to oil starvation due to loose oil cooler attachment bolts. Contributing to the accident was inadequate maintenance during the annual inspection.

NTSB analysis

The airplane was over mountainous terrain when the pilot noticed the engine oil pressure was below 30 psi. He determined that the closest suitable airport was his destination airport, and continued to that airport. Shortly thereafter, the engine oil pressure dropped to zero, and the engine began to shake violently. The pilot shut down the engine, declared an emergency, and turned towards the nearest airport displayed on his GPS, but he did not have enough altitude to glide all the way to the airport. The pilot executed a forced landing in desert terrain. During the landing, the airplane sustained substantial damage to the nose and left wing.

Postlanding photographs show oil and dirt streaks along the right side of the airplane originating from the vicinity of the engine cowling. A postaccident engine examination revealed that the lower bolts that secured the engine oil cooler were not tight and that the lower half of the oil cooler gasket was deformed, which allowed pressurized oil to exit the engine along the bottom of the oil cooler adaptor plate. Additional engine cooling baffling was also secured to the engine by the oil cooler bolts. Thermal and mechanical damage within the engine was consistent with oil starvation. The airplane had its annual inspection 6.4 hours prior to the accident. A normal part of the annual inspection would have been to remove the baffling around the engine oil cooler in order to fully access the engine; the baffling would be replaced after completion of the inspection. It is likely that the bottom bolts of the engine oil cooler where the baffling attached were not properly torqued during reinstallation.

Text from the NTSB. Open the NTSB docket for WPR13LA015 for the full record.