What happened
On April 16, 2014, three gliders departed from Bragança Aerodrome (LPBG) for a recreational training and leisure flight. While one aircraft remained near the airfield, the other two proceeded east into mountainous terrain for a cross-country exercise. During the flight, meteorological conditions began to change rapidly as cirrus clouds appeared, hindering thermal activity in the area.
As the thermal conditions deteriorated, one pilot reported that no further lift was available in the northeast area and returned to the aerodrome. The second pilot, flying approximately 20 km northeast of the airfield, realized they were losing altitude too quickly to reach the aerodrome. Faced with no other safe alternatives, the pilot selected a field containing various cereal plantations for an off-field landing.
During the approach, the pilot realized too late that the chosen terrain featured a significant double negative slope in both the longitudinal and perpendicular directions. After avoiding a small tree and a slope, the aircraft made its first contact with the ground approximately 135 meters into the field. The impact, likely caused by the terrain's lateral inclination or a flight path correction, damaged the right wingtip. Following a bounced landing, the aircraft struck the ground a third time, where the right wing became caught in bushes. The momentum of the free left wing caused the aircraft to roll over into an inverted position, eventually coming to rest 35 meters from the end of the field.
The investigation
The GPIAAF investigation examined the aircraft, the terrain, and the environmental conditions at the time of the accident. Investigators noted that the low sun position and reflections on the aircraft canopy made it difficult for the pilot to visually assess the regularity of the terrain ahead. The investigation also reviewed the pilot's credentials, finding that the pilot held a valid ATPL and was experienced in mountain flying, with no medical conditions contributing to the event.
Findings
- The pilot was forced to perform an off-field landing due to the loss of lifting conditions in the mountainous region.
- The chosen landing site featured irregular terrain with a negative slope, which contributed to the initial wing strike.
- The aircraft, a Schleicher ASW 20 L, sustained substantial damage to its primary structure and cockpit, though the wingtips were the only components lost.
- The pilot sustained minor injuries but was able to exit the aircraft independently.
- The landing dynamics, specifically the energy of the left wing, caused the aircraft to undergo a lateral rollover into an inverted position.