What aircraft was involved and where did it happen?

The accident on 2003-03-13 involved a ACCIDENT survenu au planeur, registration F-CFAJ, at FR.

What was the probable cause of the accident?

The accident was caused by the crew's failure to adequately account for local atmospheric conditions, leading to an encounter with significant descending air currents while flying at low altitude near the terrain.

Glider collision with trees during mountain flight in France

A Schempp Hirth Janus B glider sustained heavy damage after striking trees during a training flight near Saint-Alban-Leysse.

What happened

On Thursday, March 13, 2003, at approximately 16:00, a Schempp Hirth Janus B glider, registration F-CFAJ, was involved in an accident during a training flight in the mountains near Saint-Alban-Leysse. The flight, conducted by an instructor and a student pilot, began with a winch takeoff from the Chambéry Challes-les-Eaux airfield around 15:15.

Following a morning weather briefing, the crew departed from the Peney slope at an altitude of approximately 1,450 meters. Their objective was to reach the Revard area, where favorable meteorological conditions had been reported. While navigating from the western slope of Peney toward the Nivolet ridge, the pilot encountered moderate sink rates, necessitating a course correction to the left to bypass the ridge southward.

As the aircraft crossed the ridge at approximately 120 km/h with flaps retracted, the crew turned right to follow the western flank of the Nivolet. At this stage, the airspeed had decreased to 100 km/h with flaps set at +8°. The glider was flying at an altitude of roughly 50 meters, positioned on the lee side of the ridge and approximately 50 meters horizontally from the terrain. Suddenly, the variometer indicated a sharp descent rate of seven to eight meters per second.

In an attempt to regain altitude, the instructor took control and initiated a left turn toward the valley. During this maneuver, the right wing of the glider struck the treetops. The impact caused the aircraft to pivot to the right and come to a halt facing the mountainside, held by the trees with the tail section overhanging a cliff.

The investigation

The investigation focused on the flight path, the meteorological conditions at the time of the accident, and the crew's response to the sudden loss of altitude. Investigators examined the aircraft's configuration, noting the use of +8° flaps, and analyzed the atmospheric conditions, specifically noting a 15-knot northeast wind at 1,500 meters altitude.

Findings

The aircraft, a Schempp Hirth Janus B, sustained heavy damage.
The primary cause of the accident was the insufficient consideration of aerological conditions, specifically the impact of descending air currents on the flight path.
The crew was flying in close proximity to the terrain on the lee side of the ridge, leaving minimal margin for error when encountering sudden sink.