On June 22, 1991, a Cessna 180G (registration N4700U) operated by Maxl Willis was involved in an aviation accident near Challis, ID. Investigators recorded the probable cause as: The exhaust valve rocker shaft boss on one cylinder failed, and the broken piece migrated under the intake rocker shaft, causing the valve push rod to bend. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A Cessna 180 experienced engine roughness and power loss minutes after departure, leading to a forced landing near a river. Investigation revealed a failed exhaust valve rocker shaft boss caused a bent push rod.
Incident Overview
A Cessna 180 aircraft was in cruise flight a few minutes after departure when the engine began running rough and lost power. The pilot, unable to return to a safe landing site, elected to attempt a forced landing near a river.
Engine Examination
Following the incident, an engine teardown was conducted. Examination revealed that the exhaust valve rocker shaft boss on one cylinder had failed. The broken piece migrated under the intake rocker shaft, where it caused the valve push rod to bend.
Forced Landing
The pilot executed a forced landing near the river. The aircraft sustained damage during the landing. No other details about the outcome or occupants were provided in the source.
Probable cause
The exhaust valve rocker shaft boss on one cylinder failed, and the broken piece migrated under the intake rocker shaft, causing the valve push rod to bend.
What happened in the 22 Jun 1991 Cessna 180G accident near Challis, ID?
A Cessna 180 experienced engine roughness and power loss minutes after departure, leading to a forced landing near a river. Investigation revealed a failed exhaust valve rocker shaft boss caused a bent push rod.
What aircraft was involved and where did it happen?
The accident on 22 Jun 1991 involved a Cessna 180G, registration N4700U, operated by Maxl Willis, at Challis, ID.
What was the probable cause of the accident?
The exhaust valve rocker shaft boss on one cylinder failed, and the broken piece migrated under the intake rocker shaft, causing the valve push rod to bend.
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