What happened
On January 31, 2000, at approximately 12:55 PM, a Kitfox Koala ultralight, identified as 31-GS, was involved in a takeoff accident at the Uls landing site in the Ariège mountains. The aircraft, equipped with skis for snow operations, was being operated for private use.
The pilot had previously landed at the site around 12:45 PM and performed a ground reconnaissance on foot to prepare for departure. During this inspection, the pilot observed a partially melted snow bridge spanning a stream directly in the aircraft's path. Consequently, the pilot aligned the aircraft to a heading of 240°.
During the takeoff roll, the aircraft encountered a snow mound. The impact caused the left main landing gear leg to break, forcing it into a horizontal position against the left front strut. Following the structural failure, the pilot elected to divert to Toulouse-Lasbordes, an airfield with a longer runway and established safety resources. Upon arrival at Toulouse-Lasbordes, the pilot utilized the remaining fuel to reach the destination. During the landing on the paved runway 16, the pilot landed on the right wheel only. As the left wing began to dip, the pilot executed a deliberate left turn, resulting in the aircraft coming to a stop on the grass east of the runway after a 120-degree rotation.
The investigation
The investigation focused on the sequence of events leading to the structural failure of the landing gear. Investigators examined the environmental conditions at the time of the accident, noting a temperature of +8°C and approximately one meter of old, wet snow on the ground. The investigation also reviewed the pilot's ground reconnaissance and the subsequent takeoff roll.
Findings
- The primary cause of the accident was the incorrect assessment of the surface conditions of the takeoff area.
- While the pilot had identified a snow bridge, the takeoff roll was longer than anticipated due to poor sliding characteristics of the surface, a factor that was not detected during the initial ground inspection.
- The impact with a snow mound during the takeoff roll directly caused the failure of the left main landing gear leg and damage to the left front strut.