Incident Overview
A pilot experienced an engine malfunction during a flight near Laramie, Wyoming, leading to a forced landing on a pipeline. During the landing roll, the aircraft struck a ditch, causing the nose gear to fail and the plane to flip over.
Previous Engine Issue
The pilot reported that on a prior flight, the engine would not produce more than 27 to 28 inches of manifold pressure. The engine was subsequently inspected, but no problem was found that would account for the loss of manifold pressure. During a subsequent takeoff, the engine reached the red line normally.
Flight Details
The takeoff was uneventful, and the pilot climbed to 10,500 feet. Approximately 35 miles from Laramie, Wyoming, the manifold pressure decreased to 17 to 18 inches. Unable to maintain altitude, the pilot decided to land along a pipeline.
Forced Landing and Accident
During the landing roll, the aircraft hit a ditch. The impact caused the nose gear to fail, and the airplane flipped over.
Investigation Findings
An investigation revealed that the bosses for the #6 exhaust valve rocker arm had failed. Additionally, the #6 intake valve push rod had broken, and its rod tube was knocked out of alignment.