Casualties unknown

Engine Failure at Altitude Leads to Forced Landing on Rocky Terrain (N56924)

Medicine Bow, WY, US

On January 20, 1993, a Boeing A75N1 (registration N56924) operated by Denton, Larry E. was involved in an aviation accident near Medicine Bow, WY. Investigators recorded the probable cause as: The failure of the number 7 cylinder intake valve rocker arm, which resulted in an engine stoppage and a subsequent forced landing. 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 2026-06-22Data APIEditorial standards

An aircraft experienced multiple engine surges after reaching cruising altitude, resulting in a forced landing on difficult terrain during nighttime conditions due to a mechanical failure.

What happened

The pilot reported that shortly after leveling off at 14,000 feet mean sea level, the engine surged three times and then stopped. A forced landing was executed onto rocky, upsloping terrain, under dark night conditions.

The investigation

Subsequent disassembly of the engine revealed that the number 7 cylinder intake valve rocker arm had failed.

Probable cause

The failure of the number 7 cylinder intake valve rocker arm, which resulted in an engine stoppage and a subsequent forced landing.

Frequently asked questions

What happened in the 20 Jan 1993 Boeing A75N1 accident near Medicine Bow, WY?

An aircraft experienced multiple engine surges after reaching cruising altitude, resulting in a forced landing on difficult terrain during nighttime conditions due to a mechanical failure.

What aircraft was involved and where did it happen?

The accident on 20 Jan 1993 involved a Boeing A75N1, registration N56924, operated by Denton, Larry E., at Medicine Bow, WY.

What was the probable cause of the accident?

The failure of the number 7 cylinder intake valve rocker arm, which resulted in an engine stoppage and a subsequent forced landing.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X11759. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.