What happened
On February 14, 2004, at approximately 12:30 UTC, a Piper PA 18-150 Super Cub, registration I-BGMT, was performing a recreational flight over the Aosta Valley. While attempting to land on an unmarked landing area on the Brulé Glacier, the aircraft's left landing gear struck a block of frozen snow. The impact caused the landing gear strut to collapse as the aircraft was nearly at a standstill at the end of its landing roll.
There were two persons on board, including the pilot and a passenger, both of whom remained uninjured. The aircraft sustained damage specifically to the landing gear strut, but no damage was caused to third parties.
The investigation
The investigation examined the pilot's approach and the surface conditions of the glacier. Prior to landing, the pilot conducted a reconnaissance of the intended landing site. This included a pass at 10,000 feet to check for turbulence and a low-level pass at approximately 10,700 feet (roughly 400 feet above the ground) to identify potential obstacles.
During this reconnaissance, the pilot observed several blocks of snow on the surface. Based on the time of day and the level of solar radiation, the pilot assessed the snow as being "wet" and underestimated the hardness of the obstacles. However, during the actual landing, the surface proved to be much harder and more icy than anticipated. This unexpected surface texture extended the aircraft's deceleration distance and caused the landing gear to strike a block of snow that was significantly more resistant than the pilot had estimated.