What happened
On March 12, 2002, a Piper PA-18, registration I-BALM, was conducting an aerial fire reconnaissance mission. The flight originated from Venegono, carrying a pilot and an observer. After surveying the provinces of Varese and Como, the crew proceeded toward Valtellina and Upper Valcamonica.
During the mission, the pilot decided to land at the Tonale airfield, located approximately four minutes away, to attend to personal physiological needs. The pilot was familiar with this location, as it had previously served as a secondary base for firefighting operations. Prior to the landing, the pilot performed a low-altitude pass to inspect the runway conditions, noting recent snowfall in the area from the previous week. From the air, the runway appeared to have compact, uniform snow with visible footprints, and the adjacent slope showed patches of dry grass and melting snow.
To minimize the landing distance, the pilot approached at the minimum allowable airspeed. However, upon touchdown, the main landing gear wheels sank more than 60 cm into heavy, wet snow. This sudden deceleration created a pitching moment that caused the aircraft to overturn.
The investigation
The ANSV investigation focused on the pilot's experience, the aircraft's airworthiness, and the runway conditions. The pilot was a 45-year-old male holding a valid commercial pilot license with 5,200 total flight hours, including 3,100 hours on tailwheel aircraft. The investigation found no issues regarding the airworthiness of the Piper PA-18 or its engine. The meteorological conditions at the time of the accident were reported as having good visibility and no wind.
Findings
- The primary cause of the accident was the incorrect assessment of the landing area's suitability.
- While the surface snow appeared compact from a low-altitude pass, the underlying snow was heavy and wet, causing the gear to sink deeply upon impact.
- There were no injuries to the two occupants, though the aircraft sustained damage to the propeller and the right wing strut.