What happened
On April 27, 2018, a PA-18 aircraft, registration HB-PMN, was performing a private flight under Visual Flight Rules (VFR) from Bex to Bec de Nendaz. After completing a roughly 20-minute flight and landing at the destination, the pilot attempted to execute a 180-degree turn. During this maneuver, the pilot increased engine power; however, the aircraft failed to initiate the turn and continued to slide straight ahead. Unable to regain directional control, the aircraft exited the runway area and struck a small shed located at the end of the landing axis near the lakeshore.
The investigation
The investigation focused on the environmental conditions and the aircraft's behavior during the turn-back. Investigators examined the state of the runway surface and the pilot's actions. The aircraft sustained slight damage to the propeller, the nose, and the outer leading edge of the right wing, while the shed also sustained minor damage. The investigation also considered reports from other pilots operating at the same airfield earlier that day to determine the friction levels of the runway surface.
Findings
- The primary cause of the loss of control was the pilot's misjudgment of the runway surface friction. The pilot estimated that the snow on the runway was more slippery than anticipated.
- While the pilot believed the snow was particularly slick, testimony from another pilot who had landed at the same location earlier that morning suggested the snow was actually quite sticky.
- The aircraft's inability to complete the turn despite increased power indicates a lack of lateral grip on the runway surface.