What happened
On August 9, 2003, a Piper PA-19 Super Cub, registration F-BOUK, was performing local circuit training at AD Brive (19) during a period of calm winds and CAVOK conditions. During the second landing of the flight, the aircraft touched down to the right of the runway centerline and subsequently bounced.
In an attempt to realign the aircraft with the runway axis during deceleration, the pilot applied rudder inputs and potentially used the brakes. During this maneuver, the pilot lost control of the aircraft as it appeared to sag toward the right side. This resulted in a ground loop, during which the right wingtip struck the runway, causing damage to the right wing.
The investigation
The investigation focused on the mechanical integrity of the landing gear components. Examination of the aircraft revealed that the bungee cord (sandow) acting as the shock absorber for the right landing gear had ruptured. The inspection also identified multiple fatigue cracks and points of failure within the sheath and peripheral elastic fibers of the cord. Similar signs of wear were observed on the left bungee cord.
Investigators reviewed the maintenance records for the aircraft. While the maintenance program for the approved maintenance unit requires visual inspections of the bungee cords after disassembly at intervals of 50, 100, 500, and 1,000 hours, the records were inconclusive regarding the last replacement date of the cords. The only recent documentation found was a 1994 order for four replacement bungees. Notably, during the 1,000-hour inspection performed in April 2003, there was no recorded mention of the condition of the bungees, and the relevant maintenance item had not been formally validated.
Findings
- The primary cause of the ground loop was the rupture of the right landing gear shock absorber bungee.
- The maintenance inspection was incomplete, as the condition of the bungee cords was not properly assessed or documented during the most recent 1,000-hour inspection.