What happened
On 11 May 2001, an Avid MK4 Speedwing, registration G-BUSZ, was performing a private flight from Full Sutton Airfield. Shortly after departing from Runway 04, the aircraft reached an altitude of between 125 and 150 feet when it ceased to climb. The pilot reported that the aircraft became unresponsive to both rudder and stick inputs, despite the engine maintaining 6,200 RPM and the airspeed indicator showing 68 mph.
During the climb, the passenger attempted to retrieve a map from a door pocket. Shortly after this, the aircraft began to bank steeply to the left. The aircraft subsequently struck the ground approximately 50 metres beyond the end of the grass runway in a steep, nose-down attitude. The impact, which occurred in an inverted position, caused major damage to the wings, engine, propeller, and the forward fuselage. Both the pilot and the passenger sustained serious injuries.
The investigation
The AAIB examined the wreckage and the flight control systems. While initial inspections by engineers suggested a potential failure in the elevator control linkage, detailed metallurgical analysis confirmed that the fracture in the elevator push-pull rod attachment was a post-impact phenomenon caused by the deformation of the fuselage.
Investigators also reviewed the engine and propeller. The Rotax 582 engine was found to be in good working order with no evidence of power loss. The propeller blades were correctly pitched for the installation. The investigation also considered environmental factors, such as potential wake turbulence from a preceding Piper aircraft or wind-induced turbulence from nearby trees, but concluded these were unlikely to have caused the loss of control.
Findings
- The primary cause of the accident was insufficient airspeed.
- The aircraft's stall speed at its takeoff weight was approximately 54 mph, and the aircraft was flying at a speed that left little margin for error.
- There was no evidence of pre-impact mechanical failure in the flight controls or engine performance.
- The aircraft's design lacked an elevator travel stop in the nose-down direction, a known vulnerability in some Speedwing models that can lead to damage to the pitch control linkage.
Safety action
Following the investigation, the AAIB recommended that the Popular Flying Association (PFA) identify and mandate a modification to introduce an effective pitch control stop for the elevator. In response, the PFA issued a modification requiring owners to fit a standard elevator stop assembly or an equivalent device.