What happened
On 22 August 2002, a modified Avid Speedwing, registration G-FOLD, was performing a solo familiarisation flight at Otherton Airfield, Staffordshire. The pilot, who had no prior experience on this specific type, was conducting the flight following a recent wing span extension modification. During the takeoff roll on the grass runway, the pilot heard a distinct crack and felt a bump at approximately 65 mph.
As the aircraft became airborne, it began an uncommanded roll to the left. Despite the pilot applying full right stick input, the left bank increased. At roughly 100 feet altitude, the aircraft began to descend with an increasing bank angle. The pilot attempted to recover by applying full power and elevator, but the aircraft eventually struck the ground with the left wing low. The impact caused the aircraft to roll onto its right wing and slide through the field. The pilot sustained one serious injury but was able to exit the wreckage without assistance.
The investigation
Investigators examined the wreckage and the flight control system to determine the cause of the roll. While the pilot reported a loss of control, the control stick remained free to move, and no evidence of control detachment or restriction was found in flight. The investigation also looked into the possibility of a stall or spin, but impact patterns and witness accounts suggested a relatively flat pitch attitude, which was inconsistent with a stall.
Detailed examination of the airframe revealed significant damage to the landing gear truss, including an undocumented and unapproved repair involving inserted steel rods. Crucially, the investigation focused on the left wing's aft lift strut. Metallurgical analysis of the fractured threaded rod at the wing attachment point showed that the rod had failed due to overload bending. The analysis ruled out fatigue or corrosion, suggesting the rod had been bent prior to the flight, possibly during ground handling or a previous hard landing.
Findings
- The primary cause of the loss of control was likely the structural failure of the left wing lift strut attachment rod.
- The failure of this strut would cause the wing to twist, creating a nose-down movement on the left side and inducing the observed left roll.
- The pilot's attempt to correct the roll with right stick input likely exacerbated the wing twist due to the aerodynamic effects of the flaperons acting as trim tabs on an unrestrained wing.
- The threaded rod had been subjected to a compressive load sufficient to cause bending, which could have occurred if the rod was already deformed from a previous event.
Safety action
Following the investigation, the Popular Flying Association (PFA) issued an Airworthiness Information Leaflet requiring inspections of the lift strut threaded attachment rods on all Avid aircraft.