On July 11, 2006, a Grumman-schweizer G-164B (registration N6645Q) operated by Tri State Aero was involved in an aviation accident near Frederick, MD. Investigators recorded the probable cause as: Fractured masterod consistent with exposure to hydraulic lock prior to the accident flight. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During cruise, the pilot reported rough engine, smoke, and power loss. Emergency landing in cornfield resulted in inverted airplane with substantial damage. Post-accident examination revealed fractured masterod from prior hydraulic lock.
Accident Overview
During cruise flight, the pilot of a Grumman-Schweizer G-164B airplane reported that the engine began to run rough and shake violently. Smoke was observed coming from the exhaust. The engine subsequently lost power, prompting the pilot to perform an emergency landing in a cornfield. Upon touchdown, the airplane came to rest inverted, resulting in substantial damage.
Engine Examination
A post-accident examination of the engine revealed a fractured masterod. The masterod, a critical engine component, was found to be broken. Further analysis of the deformation and damage to the masterod indicated that it was consistent with being exposed to a hydraulic lock prior to the accident flight. Hydraulic lock occurs when incompressible fluid, such as oil, accumulates in a cylinder and prevents piston movement, potentially leading to severe component stress and failure.
Probable cause
Fractured masterod consistent with exposure to hydraulic lock prior to the accident flight.