What happened
On 15 August 2003, a Piper PA18-150 STC 180, registration EI-BIK, was involved in a ground accident at Gowran Grange, Co. Kildare. Following a period of refuelling, the pilot attempted to start the engine while the aircraft was positioned facing a fence and gate. Upon pressing the starter button, the engine ignited and immediately surged to full power.
Despite the pilot's rapid attempts to close the throttle and lean the mixture, the sudden acceleration caused the aircraft to move forward into a farm gate. The impact resulted in significant damage to the propeller and the starboard wing, which was effectively written off. There were no injuries to the pilot or any persons outside the aircraft.
The investigation
The AAIU investigation focused on the mechanical state of the aircraft and the positioning of the aircraft during the refuelling process. Investigators discovered that the securing point for the throttle's Bowden cable had detached because a previous weld on the support had fractured. This specific support had been installed as part of a modification to increase the aircraft's horsepower. The failure of this weld meant the pilot could no longer effectively control the throttle linkage between the cockpit and the engine.
Furthermore, the investigation examined the airfield layout. The aircraft had been positioned close to the perimeter fence to facilitate refuelling using a short hose. The investigation also noted that the manufacturer advises against welding critical components like throttle cable supports.
Findings
- The primary cause of the uncontrolled engine surge was the failure of a weld at the throttle cable support.
- The pilot's decision to restart the engine while facing an immediate obstacle contributed to the collision.
- The parking and refuelling procedure used was deemed unsafe, as the aircraft was not positioned to allow for a safe exit in the event of an emergency.
Safety action
- The aircraft operator's procedures manual should be updated to define safe parking and refuelling methods to ensure adequate separation from obstacles.