What happened
On August 9, 2013, a Schempp-Hirth Duo Discus motor glider, registration OO-YGB, was conducting a local flight originating from Sisteron. The flight began with the pilot in the front seat at the controls. After performing maneuvers to gain altitude and flying over Mont-Ventoux, the controls were transferred to the rear pilot. Following the flight near Gap Tallard, the front pilot resumed control and began a new route toward Sisteron.
During the flight, the pilot determined the aircraft was too low to reach the intended destination and decided to divert to an airfield in Seyne. While navigating toward the east, the aircraft entered the lee side of a ridge, leading to a loss of altitude. In an attempt to regain height through ridge soaring, the pilot directed the aircraft toward a northeast ridge. However, the descent continued, forcing the pilot to select a nearby plowed field for an emergency landing. During the final approach, the aircraft's speed decreased, leading to a stall. The glider struck a thicket, entered a spin, and ultimately impacted the ground with significant force.
The investigation
The investigation examined the flight profiles, weather conditions, and pilot experience. The front pilot was highly experienced, with over 7,000 total glider flight hours, including significant time in the region. The rear pilot had approximately 3,000 hours but lacked extensive mountain flying experience. The crew had briefed the flight earlier that day, noting northwest winds and average lift.
At the time of the accident, a north/northwest airflow was established in the Alpine valleys, creating marked sink on the lee side of the terrain. The landing site was a 150-meter uphill plowed field bordered by bushes. The investigation also noted that the pilot typically does not utilize the engine during flight if an alternative landing area is available.
Findings
- The aircraft entered a descent due to being positioned on the lee side of terrain during a period of established sink.
- The pilot's decision-making led to a late diversion to the emergency landing site.
- The pilot's overconfidence prevented a timely decision to terminate the flight, which would have allowed for a safer approach to the landing area.