What happened
On 25 March 2017, an Isaacs Fury II, registration G-BBVO, was performing a private return flight from Fenland Airfield to Felthorpe Airfield. The aircraft was flying in formation, with both aircraft operating at speeds exceeding the optimum cruise velocity for the type.
While at approximately 800 ft agl near the former RAF Langham station, the engine experienced a surge before failing completely. The pilot initiated forced landing procedures and identified Langham Airstrip as a potential landing site. However, upon determining that the airstrip was out of reach, the pilot opted to land in a nearby paddock. The aircraft touched down on rough grass with an estimated 10 kt tailwind. As the aircraft neared a halt, the left wing struck a fence, causing the aircraft to slew approximately 75 degrees. This impact resulted in damage to the rear fuselage after the tail skid trunnion was displaced.
The investigation
The investigation established that the pilot had relied on a simplified calculation of remaining fuel based on elapsed time, rather than direct measurement, because the reserve tank lacked a quantity gauge. The pilot's assessment indicated that the aircraft would arrive at Felthorpe with 30 minutes of fuel remaining. However, the investigation found that the pilot had underestimated fuel consumption due to the higher speeds maintained during the formation flight.
Findings
- The engine failure was caused by the exhaustion of fuel.
- The pilot's method of estimating fuel reserves using elapsed time was inadequate for the flight conditions.
- The higher speeds used during formation flight increased the rate of fuel consumption beyond the pilot's expectations.
- The aircraft sustained damage to the rear fuselage and tail skid trunnion due to the side load experienced during the ground loop caused by contact with a fence.