What happened
On 19 May 2013, a Piper PA-28-140 Cherokee, registration G-ATRR, was performing a private cross-country flight from Blackpool to Caernarfon. During the final approach to Runway 26, the aircraft experienced a loss of engine power. As the pilot attempted to manage the descent, the aircraft struck a tree located just inside the airfield boundary. The impact caused the aircraft to pitch nose-down and strike the ground. The accident resulted in one fatality and two serious injuries.
The investigation
The AAIB investigation examined the aircraft's engine, airframe, and maintenance history, alongside meteorological data and airport survey information. Investigators found that the engine had not suffered any mechanical failure and the fuel was uncontaminated. However, the atmospheric conditions, characterized by a specific temperature and dewpoint spread, were highly conducive to carburettor icing.
Regarding the airframe, the investigation identified that the rear spar bolts on both wings were missing, though this was not believed to have contributed to the crash. The investigation also revealed significant maintenance discrepancies; the engine had exceeded its recommended overhaul period, and there was evidence that 150-hour maintenance checks were being recorded as 50-hour checks. Furthermore, the tree that was struck was found to be infringing upon the airport's approach and takeoff surfaces, a fact that had gone unnoticed by the airport operator due to inaccurate height-measurement equipment.
Findings
- The primary cause of the accident was likely carburettor icing, which led to a loss of engine power during the approach.
- The pilot's technique for using carburettor heat may have been insufficient, as the selector was found in the cold position, and the use of heat during the downwind leg might have been too brief to prevent ice build-up during the final approach.
- The tree struck by the aircraft was an obstacle that infringed upon the protected approach surface for Runway 26.
- Maintenance irregularities were identified, including the failure to perform required cylinder compression checks and the use of incorrect maintenance worksheets.