What happened
On July 18, 2013, a Pipistrel Sinus motor glider, registration LN-GPI, was performing a private flight from Elverum Starmoen Airport to Bøverbyle, Oppland. During the approach, the pilot elected to fly the landing with the engine shut off, utilizing the aircraft's glider capabilities.
While on the downwind leg, the pilot encountered more sink than anticipated, necessitating an early turn toward the base leg. As the aircraft approached the final approach for runway 18, the pilot attempted to level the wings. During this maneuver, the aircraft encountered a wind shear. The wind was recorded at 270 degrees with a strength of 14 knots, approaching the aircraft's maximum demonstrated crosswind component of 15 knots. The pilot was unable to correct the wing tilt before the left wingtip and left main landing gear struck the ground. The impact caused the landing gear to break, and the aircraft slid across the terrain on the broken gear, the right wheel, and the propeller spinner, eventually coming to a stop after rotating 180 degrees.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the flight procedures and the aircraft's technical manual. The investigation focused on the pilot's decision to fly with the engine off and the impact of the prevailing wind conditions on the aircraft's stability. The investigation also reviewed recommendations from the Norwegian Gliding Association (NLF) regarding energy management during landings in powered sailplanes.
Findings
- The pilot was flying with the engine shut off, which resulted in a lack of excess energy to manage the approach.
- The pilot encountered unexpected sink on the downwind leg, leading to a premature turn to base.
- The aircraft was subjected to wind shear just before touchdown, which prevented the pilot from leveling the wings.
- The landing approach was constrained and tight due to the combination of the engine being off and the existing wind conditions.