On September 24, 1985, a Hiller UH-12D (registration N67182) was involved in an aviation accident near Breese, IL. Investigators recorded the probable cause as: The engine failure was caused by the #4 piston failing due to burning and molten aluminum transferring to the exhaust valve stem, causing the valve to stick open. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced an engine failure at low altitude, forced landing to a road construction site resulted in tail boom separation and rotation due to a failed piston.
Incident Overview
A pilot reported a loss of engine power while flying at an altitude of approximately 200 feet above ground level (AGL). Following the power loss, the pilot turned the helicopter and initiated an autorotation to a road construction site. The landing was tail low, causing the tail boom to be severed. The helicopter then bounced and rotated 180 degrees before coming to rest.
Engine Examination
An examination of the engine identified a failure of the #4 piston. The piston had burned and molten aluminum transferred to the stem of the exhaust valve, resulting in the valve sticking open. This condition prevented the cylinder from sealing and contributed to the loss of engine power.
Probable cause
The engine failure was caused by the #4 piston failing due to burning and molten aluminum transferring to the exhaust valve stem, causing the valve to stick open.
What happened in the 24 Sept 1985 Hiller UH-12D accident near Breese, IL?
A helicopter experienced an engine failure at low altitude, forced landing to a road construction site resulted in tail boom separation and rotation due to a failed piston.
What aircraft was involved and where did it happen?
The accident on 24 Sept 1985 involved a Hiller UH-12D, registration N67182, at Breese, IL.
What was the probable cause of the accident?
The engine failure was caused by the #4 piston failing due to burning and molten aluminum transferring to the exhaust valve stem, causing the valve to stick open.
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