What happened
On September 24, 2013, a student pilot conducted a solo instructional flight in a Grob G-103 Twin Astir, registration F-CFYT, departing from the Saint-Martin-de-Londres airfield. After being towed to an altitude of approximately 700 meters, the pilot failed to find sufficient thermals and elected to land on runway 12.
During the final approach, the glider maintained a speed of approximately 105 km/h, which was higher than the optimal approach speed of 93 km/h. The airbrake deployment was only partial. Upon touchdown, the aircraft bounced twice. Following the second bounce, the pilot extended the airbrakes to prevent the aircraft from overshooting the runway. This action caused the glider to stall at an altitude of roughly 5 meters, resulting in a heavy impact with the ground. The force of the impact caused the tail boom to break, and the aircraft came to rest approximately 150 meters from the end of the runway.
The investigation
The investigation focused on the pilot's flight parameters and control inputs during the landing phase. The pilot had 93 hours of dual instruction time, with very limited solo experience. Meteorological conditions at the time were favorable, with visibility exceeding 10 km and light winds of 4 knots.
Investigators examined the pilot's decision to maintain a higher approach speed, which the pilot stated was an attempt to prevent a stall in the event of increasing winds. However, the instructor noted that the pilot had been taught to use the optimal approach speed during low-wind conditions. Furthermore, the investigation revealed that the pilot likely retracted the airbrakes during the flare instead of extending them, a procedural error the instructor noted was a common lack of automation among students.
Findings
- The approach was unstable due to an excessive approach speed.
- The pilot experienced a loss of control during the landing phase following multiple bounces.
- An error in airbrake handling contributed to the stall and subsequent structural failure of the tail boom.
- The pilot sustained one injury, and the aircraft was destroyed.