What happened
On 18 October 2020, a Druine D.31 Turbulent, registration G-ARNZ, was conducting a private flight near Damyns Hall Aerodrome. After approximately 80 minutes of local flight, the pilot attempted to rejoin the airfield circuit from the south-east. While at an altitude of 1,100 ft, the engine began to run roughly before suffering a complete loss of power. The pilot declared a MAYDAY.
Recognising the aircraft's limited glide performance due to its short wings, the pilot bypassed a distant golf course in favour of a nearby field. Although the landing site initially appeared suitable, the terrain was found to be boggy and overgrown during the descent. The aircraft touched down approximately 1.3 nm from the airfield, at which point it flipped onto its side and came to rest inverted. The pilot, who suffered minor injuries, was airlifted from the scene. The aircraft sustained extensive damage.
The investigation
Investigators examined the engine and fuel system of the aircraft to determine the cause of the power loss. The inspection focused on the mechanically driven fuel pump, which had been installed 30 hours prior to the accident. This specific pump was a sealed unit featuring a plastic rocker arm, a relatively new component in aftermarket pumps for this engine type.
Engineers discovered a crack in the plastic cam-driven rocker arm within the mechanical fuel pump. This failure prevented the pump from delivering sufficient fuel to the engine, leading to the engine's malfunction and subsequent shutdown.
Findings
- The engine failure was caused by the cracking of a plastic rocker arm within the mechanical fuel pump.
- The failure of this component resulted in a total loss of engine power.
- The pilot's decision to land in a field with boggy vegetation contributed to the aircraft overturning upon touchdown.