What happened
On 14 December 2016, an Isaacs Fury II, registration G-BEER, was conducting private aerobatic manoeuvres approximately 4 nautical miles north of Billericay, Essex. During the execution of a normal loop, the pilot encountered what was perceived as wake turbulence, which triggered a left roll of the aircraft. While the pilot successfully recovered the aircraft to a wings-level position, a post-flight inspection revealed that the aircraft's fabric had separated from the forward section of the top left wing.
Following the incident, the pilot performed control checks in the approach configuration. Despite observing a significant rolling tendency, the pilot determined the aircraft remained sufficiently controllable to proceed with a landing. The aircraft landed without further incident, resulting in no injuries to the pilot.
The investigation
An inspection of the aircraft was conducted by the Light Aircraft Association (LAA). This examination identified a failure within the leading edge structure of the affected wing. The investigation established that the most probable cause was the presence of pre-existing damage to the leading edge. This damage may have been too small to be detected during the pilot's pre-flight walkaround. It is believed that the increased aerodynamic loads experienced during high-energy aerobatic manoeuvres caused this existing damage to progress, leading to the separation of the wing fabric.
Findings
- The primary cause of the fabric separation was structural failure of the wing leading edge.
- The failure likely originated from previous damage that was not identified during pre-flight inspections.
- The stresses of aerobatic flight caused the progression of this undetected damage.