What happened
On June 20, 2017, a Piper PA 28-235 Cherokee, registration HB-PQH, departed Geneva Airport for a night VFR navigation training flight toward Caen. The flight was being conducted by a pilot in training, accompanied by an instructor.
Shortly after departure, the pilot requested to deviate from the assigned route to fly toward the Jura ridges. While climbing along the mountainside toward the Col du Sac, the pilot gradually increased the aircraft's pitch to maintain a visual distance between the ridgeline and the engine cowling. This maneuver caused the airspeed to decay until the stall warning activated. The instructor took control of the aircraft, but the plane was too close to the terrain to avoid a collision. The aircraft struck trees on the eastern slope of the mountain with high energy, causing the left wing to separate. The impact with a rock followed, and a fire brokeard shortly after. Both the pilot and the instructor sustained two injuries, and the aircraft was destroyed.
The investigation
The investigation examined the wreckage, flight data, and the crew's actions. Physical evidence showed the engine was producing power and flight controls were functional at the time of impact. The investigation also reviewed the crew's experience, noting the pilot had approximately 90 total flight hours, while the instructor was highly experienced with over 5,200 hours.
Investigators analyzed the environmental conditions, noting that the accident occurred during twilight (mesopic vision), which can degrade depth perception and contrast. The investigation also looked into the crew's focus, finding that the instructor was preoccupied with a software error on a navigation tablet, while the pilot was focused on visual references rather than flight instruments.
Findings
- The pilot's attempt to maintain a constant visual distance from the ridgeline led to an increasing pitch attitude and a subsequent loss of airspeed.
- The instructor failed to monitor the flight parameters effectively due to a distraction caused by a technical error on a navigation tablet.
- Improper management of the flight path during the ridgeline crossing was the primary cause.
- Twilight lighting conditions likely degraded the crew's ability to accurately judge distances and terrain proximity.
- High ambient temperatures may have contributed to reduced engine performance during the climb.