What happened
The incident occurred during a ground operation involving an aircraft that required engine starting via hand-propping. The pilot was physically engaged in the propping process while his wife, who held no pilot certificate, occupied the cockpit controls. As the engine started, the pilot issued verbal instructions for her to reduce power by moving the throttle forward or backward depending on the specific installation.
The woman attempted to comply with the command to "throttle down." However, due to a misunderstanding of the control's directionality or mechanical action, she moved the throttle in the opposite direction. This action increased the engine power setting rather than decreasing it. The aircraft began to accelerate rapidly across the ground. Despite her efforts, she was unable to reduce the throttle or shut down the engine before the aircraft collided with another airplane that was parked nearby.
The investigation
Post-accident examination revealed that both the moving aircraft and the stationary target sustained substantial damage. The investigation focused on the sequence of events during the starting procedure. It was determined that the primary factor was the incorrect manipulation of the throttle control by the person at the controls. There were no indications of mechanical failure with the throttle system itself; rather, the error was operational in nature.
Findings
The accident was caused by the pilot's decision to allow a non-pilot to operate the aircraft controls during a high-risk ground maneuver. The non-pilot misinterpreted the instruction to reduce power, resulting in an unintended increase in thrust. This led to a loss of control and a subsequent collision with stationary property. The use of a hand-propping procedure inherently requires precise coordination and clear communication, which was not maintained in this instance.
Safety message
Aviation regulations and best practices strictly prohibit allowing unqualified individuals to manipulate flight controls during critical phases of operation, including engine starting via hand-propping. Pilots must ensure that all persons in the cockpit are fully qualified and understand the specific procedures being performed. Clear, unambiguous communication is essential when multiple people are involved in ground operations.