What happened
On August 13, 1970, at approximately 20:00, a Piper PA-30 Twin-Comanche B, registration HB-LDE, was taxiing toward the light aircraft parking area at Geneva-Cointrin Airport following a landing on runway 23. While maneuvering through the parking apron, the pilot attempted a sharp 180-degree left turn to position the aircraft alongside a parked Piper PA-30 Twin-Comanche B, registration G-ATYR.
To execute the tight turn, the pilot significantly increased the RPM of the right engine. To tighten the turning radius, the pilot applied the left brake; however, the left brake failed to respond. The momentum of the aircraft, combined with the lack of braking force, caused the aircraft to overshoot its intended path and strike the stationary G-ATYR. The pilot, who was the sole occupant of HB-LDE, was uninjured, but both aircraft sustained significant damage.
The investigation
Investigators examined the braking system of HB-LDE and found that the left brake pedal offered no resistance during the initial inspection, though the pedal stroke decreased after several applications. While the brake fluid reservoir contained sufficient fluid, a small leak was identified at the bleed fitting of the left wheel brake cylinder.
Further technical analysis revealed that the brake segments were heavily worn and partially crumbling. These specific segments (P. No 752 342) were older-style parts that Piper had eventually superseded with harder, more wear-resistant metal segments, though both types remained approved for use. The aircraft's maintenance records showed the brakes had been serviced in November 1969, with 46 flight hours and 123 landings completed since that service.
Findings
- The primary cause of the collision was a failure of the left-wheel brake during the final phase of a parking maneuver.
- The failure was triggered by a combination of a fluid leak at the brake cylinder bleed fitting and the degraded condition of the brake segments.
- The collision was exacerbated by the pilot's high taxi speed, caused by a significant increase in right-engine RPM during the turn.
- It is probable that the brake fluid leak had already begun during the initial taxi from the runway to the parking area.