What happened
On 2 June 2001, a DH115 Vampire T11, registration G-DHAV, was participating in a private formation display at Biggin Hill airfield. The aircraft was flying in a pair alongside a Sea Vixen. Following a routine sequence, the two aircraft began to separate to perform individual manoeuvres. As the Vampire reached an 80-degree right bank while positioned approximately 550 feet behind the Sea Vixen, the aircraft suddenly rolled into an inverted position and entered a steep descent.
Video analysis of the final moments indicates the descent lasted only about five seconds. Although the pilot appeared to attempt a recovery by rolling the aircraft back to a wings-level attitude, the aircraft entered a high angle of attack and likely suffered an accelerated flick stall. The aircraft impacted the ground at high speed, resulting in 2 fatalities and the total destruction of the aircraft.
The investigation
The AAIB investigation examined the wreckage, the flight controls, and the aircraft's history. Examination of the G-DHAV wreckage showed the airframe was structurally intact at the time of impact, with no evidence of mechanical failure in the flying controls or the engine. The ejection seats were found to be armed, but there was no evidence that an ejection had been initiated before the crash.
Investigators also analysed video footage from the public and conducted aerodynamic modelling. The study focused on the interaction between the Vampire and the trailing vortices produced by the much heavier Sea Vixen. The investigation also reviewed historical flight test data from the 1950s regarding the effects of wake turbulence on smaller jet aircraft.
Findings
- The primary cause of the accident was likely the interaction with the wake vortex generated by the Sea Vixen.
- The significant weight disparity between the Sea Vixen and the Vampire meant the trailing vortices from the larger aircraft were powerful enough to exceed the aileron control authority of the Vampire.
- The aircraft's sudden roll into an inverted position likely led to an unrecoverable accelerated stall during the pilot's attempt to level the wings.
- There was no evidence of pilot incapacitation, control jamming, or structural failure prior to impact.