What happened
On 30 August 2011, a modified Piper PA-18-150 Super Cub, registration G-BJIV, was performing an aero-tow takeoff at the Yorkshire Gliding Club, located at Sutton Bank, North Yorkshire. During the takeoff run, a steel bracket within the right landing gear assembly failed. This failure caused the wheel attachment to shift upwards, which subsequently led to the right wingtip making contact with the ground.
In response to the mechanical failure, the pilot released the tow rope and shut down the engine to protect the propeller from potential damage. Following the incident, the aircraft performed a 270-degree turn to the right and came to a halt. There were no injuries to the pilot, and the aircraft sustained damage limited to the landing gear bracket and the wingtip.
The investigation
Investigators examined the landing gear assembly to determine the cause of the upward migration of the wheel attachment. The investigation established that a steel bracket, which is responsible for reacting the loads from the bungee, had developed a concealed crack.
On this specific aircraft model, each main landing gear is fitted with a cable designed to support standard suspension loads in the event of a bungee failure. In this instance, the cable functioned as intended, absorbing the support loads following the bracket's fracture. While this prevented more extensive damage to the airframe, the limited travel of the wheel was still sufficient to allow the wingtip to strike the ground.