On October 11, 1986, an Enstrom F-28A (registration N238Q) operated by Leon J. Riel was involved in an aviation accident near Belmont, NH. Investigators recorded the probable cause as: The failure of the number four connecting rod in the engine. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced an in-flight engine failure during cruise, leading to a hard landing autorotation that collapsed the left front strut and damaged the main rotor assembly.
What happened
The helicopter was operating in a cruise flight configuration when a sudden engine failure occurred. The pilot immediately initiated an autorotation procedure to manage the loss of power. During the descent, the aircraft impacted the ground with significant force. This hard landing caused the left front landing gear strut to collapse. As the nose section lowered due to the impact, the tail cone was forced upward. Consequently, the main rotor blades made contact with the tail rotor assembly.
The investigation
Examination of the engine revealed a mechanical failure within the internal components. Specifically, the number four connecting rod had failed completely. This structural failure was identified as the primary reason for the loss of engine power during the flight.
Probable cause
The failure of the number four connecting rod in the engine.