What happened
On September 1, 1969, at approximately 14:30, a mid-air collision occurred near the Porrentruy airfield in Switzerland. A Piper J3C, registration HB-OUB, was performing circuit patterns with a student pilot and an observer on board. During the fourth circuit, while the Piper was on final approach at an altitude of roughly 40 meters, it was struck from the rear left by a Gardan GY-80 III "Horizon", registration HB-DVB, which was approaching from the direction of La Chaux-de-Fonds.
The impact caused the Gardan GY-80 III "Horizon" to nose-dive and crash into the ground. The Piper J3C was also heavily impacted, causing its flight controls to malfunction. The pilot of the HB-OUB managed to steer the aircraft away from a group of trees, resulting in a forced landing in a field where the aircraft eventually overturned.
Tragically, the pilot of the HB-DVB died while being transported to the hospital. The pilot of the HB-OUSB sustained minor injuries, while the passenger remained unharmed. Both aircraft were completely destroyed.
The investigation
The investigation examined the flight paths, the mechanical state of both aircraft, and the environmental conditions at the time of the accident. Investigators found that the Piper J3C was on final approach with engines at idle and a stabilized airspeed. While the pilot of the HB-OUB had the right of way, the investigation also noted that the sun's position made visibility toward the approach sector more difficult.
Analysis of the wreckage of the HB-DVB revealed that the landing gear extension and flap deployment processes were not yet complete at the moment of impact. The investigation also noted that the flight patterns being used by the HB-OUB were within a smaller circuit area typically reserved for gliders, though this area was known to be used by powered aircraft as well.
Findings
- The collision was caused by an objective lack of vigilance by the pilot of the Gardan GY-80 III "Horizon".
- The pilot of the HB-DVB was likely preoccupied with completing the landing gear and flap configuration, which had not been finalized before the collision.
- The pilot of the HB-DVB likely failed to observe the Piper J3C on his right side in time to take evasive action.