Terrain collision near La Sagne during aerotow of SZD-30 in poor visibility after departing Saanen
On July 22, 1976, a glider, SZD-30 'Pirat', collided with terrain during a tow flight near La Sagne, Switzerland. The incident occurred in poor weather conditions with low visibility and cloud cover. The probable causes included the pursuit of a VFR flight in unfavorable meteorological conditions and insufficient flight preparation. The investigation revealed that the tow rope was in a deteriorated state, contributing to the loss of control of the glider.
- Aerotow cruise: During an aerotow ferry flight from Saanen toward La Chaux-de-Fonds, the glider was being towed uneventfully along the planned route.
- Deteriorating weather: Approaching La Sagne, cloud base and visibility were very low and variable, with stratocumulus and precipitation reducing VFR margins.
- Tow enters cloud: The towplane, unable to maintain safe clearance below the rapidly lowering cloud base while still towing, turned right and entered the cloud layer while the glider, slightly higher, lost visual contact with the tug and towrope.
- Glider correction attempts: The glider pilot briefly reacquired sight of the rope off-axis, attempted a heading correction, then lost sight of the rope again while still in cloud and focused forward.
- Oscillations and rope break: Excessive corrective input caused strong yaw oscillations in the glider, leading to high loads and the failure of the already deteriorated towrope approximately in its middle.
- Loss of control in IMC: After the rope broke, the glider pilot, disoriented in cloud and having the sensation of being at the top of a wingover near the tug, lost control and descended uncontrolled toward the terrain.
- Crash - no injury: The glider collided with treetops and then the ground near La Sagne, the wings being torn off and the fuselage passing between two trees so that the aircraft was destroyed but the pilot was uninjured.