Casualties unknown

Cessna 172 Engine Failure Due to Crankshaft Fracture (N1737U)

Manokotak, AK, US

On June 6, 1986, a Cessna 207 (registration N1737U) was involved in an aviation accident near Manokotak, AK. Investigators recorded the probable cause as: A fractured crankshaft in the vicinity of the number 2 and 3 crankshaft journal, which caused the engine to cease operation during cruise flight. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-06-10Data APIEditorial standards

A Cessna 172 experienced an in-flight engine failure during cruise flight due to a fractured crankshaft. The pilot executed a successful off-airport forced landing without further incident.

What happened

During the cruise phase of flight, the aircraft engine began to operate roughly. The pilot attempted to resolve the issue by switching fuel tanks, but the rough running persisted. Subsequently, the engine ceased operation entirely and did not windmill during the emergency descent. An off-airport forced landing was accomplished without further incident.

The investigation

A post-accident examination of the engine revealed that the crankshaft had fractured in the vicinity of the number 2 and 3 crankshaft journal. The specific mode of fracture was not determined.

Findings

The failure was attributed to a fractured crankshaft. The pilot's decision to perform an off-airport forced landing resulted in no further damage or injury.

Probable cause

A fractured crankshaft in the vicinity of the number 2 and 3 crankshaft journal, which caused the engine to cease operation during cruise flight.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001213X33722. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.