What happened
On 18 May 2011, a PZL Bielsko SZD-55-1, registered D-5*, was undergoing an aerotow at the Temploux airfield (EBNM). The pilot, who had recently acquired the sailplane and possessed limited experience with this specific model, was attempting the first flight of the day.
During the initial ground run, the aircraft experienced significant lateral instability. As the launch crew released the left wingtip, the sailplane began to roll, with both wings alternately making contact with the ground. The pilot attempted to correct the yaw and roll using aileron and rudder inputs; however, the high grass on the runway increased drag and friction, hindering the effectiveness of the controls at low airspeed. After the aircraft drifted significantly off-axis from the towing plane, the pilot opted to release the tow cable. Following the release, the sailplane rotated around the left wingtip and entered a nose-down dive, striking the ground with enough force to rupture the tail boom. The pilot escaped the wreckage without injury.
The investigation
AAIU(Be) examined the aircraft, the site, and the pilot's flight history. The investigation established that the aircraft was airworthy and the pilot held a valid license with significant experience in other glider types, though only six hours of flight time in the SZD-55-1.
Investigators analyzed the aerodynamic forces at play during the low-speed ground run. They noted that at approximately 40 km/h, aileron effectiveness was minimal. Furthermore, the use of right aileron to correct the roll actually increased drag by pushing the control surface into the tall grass. The investigation also considered the runway conditions, noting that the uneven surface and tall grass contributed to the yawing motion.
Findings
- The aircraft was in an airworthy condition.
- Meteorological conditions were favorable, with the wind aligned with the runway axis.
- The pilot had very limited experience with the specific characteristics of the SZD-55-1.
- The accident was caused by a delay in releasing the tow cable after the wingtip had already contacted the ground.