What happened
On 20 August 2002, a Piper L1sC (Modified) Super Cub, registration G-BPJH, was conducting a ferry flight from a private airstrip in Draperstown to Newtownards. The purpose of the flight was to deliver the aircraft for scheduled maintenance and a permit renewal. The aircraft had been refueled with 50 litres of Avgas prior to departure.
While cruising at 1,800 feet with the engine set at approximately 2,300 rpm, the engine began to run roughly before failing completely. The pilot performed a forced landing at the Maze Racecourse. During the landing sequence, the pilot applied the left brake to avoid pedestrians on the course, which caused the aircraft to veer left. The left wing tip struck a fence, and the aircraft slid through the fence into a roadside ditch, eventually tipping onto its nose. The pilot sustained no injuries.
The investigation
Investigators examined the aircraft's fuel system and engine components. Analysis of the remaining fuel in the left wing root tank, combined with estimated fuel consumption for the 30-minute flight, confirmed that the engine failure was not caused by fuel exhaustion.
Technical inspections of the fuel lines and carburettor revealed no debris or blockages. While the impact of the accident had distorted the carburettor air box, the heat control linkage remained properly connected. Testing with a temporary fuel header tank and a replacement propeller showed that the engine could start and run normally, and the magnetos were found to be functional.
Meteorological data indicated a surface temperature of 15.7°C and a dew point of 11.3°C. According to icing probability charts, these conditions presented a serious risk of carburettor icing during descent power, though the risk was slightly lower at the cruise power setting used at the time of the failure.
Findings
- The engine failure occurred approximately 30 minutes into the flight.
- There was no evidence of fuel starvation or lack of fuel on board.
- No mechanical defects were identified within the engine, ignition, or fuel delivery systems.
- The pilot reported applying carburettor heat shortly before the failure, though the possibility of carburettor icing could not be ruled out by the evidence.