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Engine Failure Leads to Forced Landing and Nose-Over (N739SU)

Snelling, CA, US

On December 8, 2003, a Cessna 172N (registration N739SU) operated by American School OF Aviation was involved in an aviation accident near Snelling, CA. Investigators recorded the probable cause as: The woodruff key linking the oil pump drive shaft to the oil pump accessory gear had sheared, resulting in oil starvation and a catastrophic failure of the engine. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 2 related events involving the same aircraft type or operator are linked below.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-07-04Data APIEditorial standards

An airplane experienced vacuum instrument failure, then engine power loss with smoke, prompting a forced landing into a field. During touchdown, the nose wheel caught, causing the aircraft to nosed over. Examination revealed a sheared woodruff key caused oil starvation and engine failure.

Incident Overview

During a flight, approximately five minutes after takeoff, the vacuum instruments failed. Five minutes later, while at an altitude of 3,000 feet, the engine emitted a loud noise and black smoke entered the cockpit. The smoke appeared to originate from the engine. Subsequently, the engine lost power and did not respond to throttle adjustments.

Forced Landing and Accident

The aircrew selected a green field for a forced landing. During the landing touchdown, the nose wheel caught the ground, causing the airplane to nosed over onto its back.

Engine Examination

Post-accident examination of the engine revealed that the woodruff key connecting the oil pump drive shaft to the oil pump accessory gear had sheared. This resulted in oil starvation and a catastrophic failure of the engine.

Probable cause

The woodruff key linking the oil pump drive shaft to the oil pump accessory gear had sheared, resulting in oil starvation and a catastrophic failure of the engine.
Engine failure

Related events

Same aircraft family

Same operator

All Cessna 172 accidents →

Frequently asked questions

What happened in the 8 Dec 2003 Cessna 172N accident near Snelling, CA?

An airplane experienced vacuum instrument failure, then engine power loss with smoke, prompting a forced landing into a field. During touchdown, the nose wheel caught, causing the aircraft to nosed over. Examination revealed a sheared woodruff key caused oil starvation and engine failure.

What aircraft was involved and where did it happen?

The accident on 8 Dec 2003 involved a Cessna 172N, registration N739SU, operated by American School OF Aviation, at Snelling, CA.

What was the probable cause of the accident?

The woodruff key linking the oil pump drive shaft to the oil pump accessory gear had sheared, resulting in oil starvation and a catastrophic failure of the engine.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20031212X02023. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.