What happened
On May 4, 2019, a LAK-17AT glider, registration SE-UUL, was conducting a general flight training mission from Borås Airport. While approximately 8 km from the airport, the pilot encountered weakening thermals and an increased sink rate. Due to a headwind and insufficient altitude to reach the airport, the pilot identified the need for an out-landing field.
The pilot initially selected the Kråklanda airfield as a landing site. During the approach, the pilot attempted to start the aircraft's small auxiliary engine. This engine is designed to be deployed and started via windmilling at speeds between 120–140 km/h to assist with climbing. However, the engine failed to start during two attempts made while turning onto the base leg.
As the aircraft descended, the pilot realized the planned airfield was no longer reachable. Consequently, the pilot decided to land on the northbound lanes of the heavily trafficked Route 41. During the touchdown, the glider struck the roof of one vehicle traveling in the same direction and the windshield of an oncoming vehicle. The aircraft also collided with two road signs, causing the wingtips and landing gear to break off and the nose of the aircraft to sustain significant damage. There were no fatalities and no physical injuries were reported among the pilot or the occupants of the cars.
The investigation
The Swedish Accident Investigation Authority (SHK) examined GPS data, interviewed the pilot, witnesses, and the drivers involved, and consulted with aviation experts. The investigation focused on the sequence of events leading to the decision to land on the highway and the technical state of the aircraft during the descent.
Analysis of GPS data revealed that the engine start attempts were initiated at a low altitude and at a significant distance from the intended landing field. Furthermore, the investigation found that the engine remained in the extended position throughout the landing. The pilot discovered after the event that the engine had not been retracted because the main power switch for the engine unit had been turned off instead of the retraction switch.
Findings
- The decision to land on a high-traffic highway created a high risk of a more serious accident.
- The engine start attempts were conducted too far from the target field and at an altitude that was too low to maintain the planned glide path.
- The engine remained extended during the landing, which contributed to a steeper descent than the pilot had anticipated.
- The auxiliary engine on this aircraft type is not a reliable safety tool for avoiding out-landings, as failed start attempts are relatively common.