What happened
On 30 November 2013, an Auster J5G Cirrus Autocar, registration G-ARKG, was conducting a private flight near Oakham. After approximately 55 minutes of flight time, the pilot and passenger began practicing steep turns at an altitude of 2,000 ft. While executing the second turn, the pilot applied left aileron and suddenly felt the right aileron cable snap. The pilot observed the cable hanging slack outside the cockpit window.
Following the failure, the pilot stabilized the aircraft to a wings-level position. After consulting with the passenger, the pilot verified that while the left aileron remained functional, the right aileron was unresponsive. To avoid the risk of an uncontrollable spiral dive, the pilot avoided using the ailerons and instead used the rudder to perform a gentle, flat turn toward the home airfield. The aircraft completed a successful three-point landing with no injuries and no structural damage to the airframe.
The investigation
Post-flight inspections focused on the right wing leading edge, where investigators identified that the aileron cable had severed behind a wind-driven generator. The investigation established that the cable strands had suffered melting damage. Further examination revealed that the generator was not securely held within its mounting clamp and could be moved rearwards and forwards.
It was determined that the generator had shifted backward until its positive terminal made contact with the ailerton cable. Testing by the Light Aircraft Association (LAA) indicated that the electrical arcing and subsequent burning had occurred across multiple points of contact rather than during a single momentary event.
Findings
- The primary cause of the cable failure was an electrical short-circuit between the wind-driven generator and the aileron cable.
- The generator moved rearwards because the mounting clamp's grip had slackened.
- The lack of stability in the mounting was due to a missing cork gasket between the generator body and the clamp.
- The aircraft was equipped with an older type of generator; a 1951 Auster Service Bulletin had previously warned of the risks associated with mounting this specific generator type too far back, but a promised redesign/modification was never implemented.