Casualties unknown

Cylinder Separation Forces Emergency River Landing (N4052Z)

Chandalar, AK, US

On August 20, 1984, a Piper PA-18-150 (registration N4052Z) was involved in an aviation accident near Chandalar, AK. Investigators recorded the probable cause as: The failure of a cylinder bolt, which resulted in the separation of a cylinder from the engine. 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 severe engine knocking led to a cylinder separation and oil covering the windshield, forcing an emergency landing in the Chandalar River.

What happened

During flight at approximately 4,500 feet mean sea level, the aircraft's engine began exhibiting severe knocking. Shortly thereafter, a cylinder separated from the engine assembly. The resulting failure caused oil to completely cover the windshield, severely obscuring the pilot's forward vision. Attempting to execute an emergency landing beside the Chandalar River, the aircraft ultimately came to rest in approximately four feet of water.

Findings

Investigation revealed that a cylinder bolt had failed, leading to the separation of the cylinder and subsequent loss of engine function. The failure occurred during cruise flight before the pilot could establish a safe forced landing site on solid ground.

Probable cause

The failure of a cylinder bolt, which resulted in the separation of a cylinder from the engine.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X40548. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.