What happened
On December 31, 1964, at approximately 14:10 local time, a Beech 3/5 Bonanza, registration HB-ECM, was positioned on the tarmac in front of the large hangar at Geneva Airport. The pilot had engaged the parking brakes and started the engine to allow for a period of warm-up. During this process, the aircraft began to move, initiating a left-hand turn.
The pilot attempted to use the brakes to halt the movement, but the aircraft continued toward a parked Miles Gemini M 65 IA, registration HB-EKS, which was stationed just a few meters away. In a final attempt to prevent the impact, the pilot shut down the engine, but the collision occurred. The rotating propeller of the HB-ECM struck the wing of the HB-EKS multiple times, and the right wing of the Bonanza also struck the right engine cowling of the Miles Gemini, causing significant denting.
There were no injuries resulting from the incident.
The investigation
Local police conducted the initial scene investigation, noting that the ground consisted of packed, frozen snow. Investigators identified a significant hydraulic fluid leak originating from the right main gear brake system of the HB-ECM. A visible patch of hydraulic oil was found in the snow directly beneath the area where the pilot had applied the brake pedal.
Subsequent technical analysis performed by Pilatus revealed that the hydraulic cylinder for the right brake had actually broken. This failure caused the right wheel to become unbraked, leading to the uncontrolled movement of the aircraft.
Findings
- The primary cause of the collision was a rupture in the hydraulic brake system of the right main gear.
- The failure occurred while the engine was warming up, causing the right wheel to release.
- The pilot initially misinterpreted the movement as uneven braking and attempted to correct it by applying the pedal, rather than immediately recognizing the total loss of braking pressure on that side.
- The collision was unavoidable once the mechanical failure had compromised the aircraft's ability to remain stationary.