On May 31, 1989, an Aeronca 7AC (registration N85459) was involved in an aviation accident near Alexandria, MN. Investigators recorded the probable cause as: The pilot's misjudgment of the throttle position during hand-propping, which resulted in excessive thrust and caused the aircraft to jump the chocks and collide with a parked aircraft. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a manual engine start attempt, an aircraft unexpectedly accelerated forward, colliding with a nearby parked aircraft and causing substantial damage to both planes due to excessive thrust.
What happened
The incident occurred while the pilot was attempting to manually start the aircraft engine using the hand-propping method. As the engine successfully ignited, the aircraft suddenly surged forward, jumping over the wheel chocks that were in place to secure it. The moving aircraft then collided with a separate parked aircraft located nearby. This impact resulted in substantial damage to both the aircraft involved in the collision and the stationary aircraft.
The investigation
Following the accident, the pilot provided an explanation for the unexpected movement of the aircraft. He stated that he likely misjudged the position of the throttle during the starting procedure. This error led to excessive thrust being applied immediately after the engine started, which caused the aircraft to accelerate uncontrollably forward before it could be stopped.
Findings
The primary factor contributing to the accident was the pilot's misjudgment of the throttle setting during the critical phase of engine start-up. The sudden application of excessive power overwhelmed the braking capability and the security provided by the wheel chocks, leading directly to the collision with the parked aircraft.
Probable cause
The pilot's misjudgment of the throttle position during hand-propping, which resulted in excessive thrust and caused the aircraft to jump the chocks and collide with a parked aircraft.