What happened
On July 3, 2003, at 14:10, a Schem/Hirth Ventus CM motor glider, registration HB-2210, departed from the Sisteron airfield in France. Shortly after takeoff from runway 36, the pilot encountered significant downdrafts near the end of the runway. Despite the engine performing normally, the pilot noted a significantly reduced rate of climb.
Navigating through the Durance valley with low altitude and airspeed, the pilot determined that returning to the departure airfield was not possible. Consequently, the pilot executed an emergency landing in the bed of a nearby river. During the landing roll along the riverbank, the left wing struck a shrub, causing the aircraft to undergo a nose-over (pitch-over) maneuver. The impact resulted in the breakage of the tail boom, and the aircraft came to a stop on the bank with the engine still running. The pilot escaped the wreckage without injury.
The investigation
The investigation focused on the meteorological conditions and the pilot's decision-making process. At the time of the accident, winds were recorded from 300 to 330 degrees at 6 knots, with gusts up to 16 knots. The investigation examined the pilot's observation of previous departures that day, noting that he had observed other gliders and motor gliders taking off without apparent difficulty, which influenced his decision to proceed.
Furthermore, investigators reviewed local operating procedures. The airfield maintains specific local instructions that warn pilots of potential turbulence at the end of runway 36 under these specific weather conditions. These instructions recommend turning west as early as possible to avoid the downdrafts prevalent in the Durance valley.
Findings
- The primary cause of the emergency landing was the insufficient consideration of aerological conditions and local instructions regarding turbulence.
- The pilot failed to adhere to the recommended flight path (turning west early) to avoid known downdrafts in the valley.
- The pilot's decision to depart was based on the observation of other aircraft performing normal departures, which did not reflect the immediate turbulence encountered during his own climb.