What happened
On June 13, 2020, a GROB 103 Twin Astir, registration SP-4033, was involved in an accident during a winch launch at the Świebodzice – Ciernie (EPWC) airfield. The flight was an introductory flight intended to test the aircraft following its recent purchase by the owner.
Due to ongoing student airplane training on the active runway, the winch launch was positioned to the southeast of the marked runway. To avoid interfering with the primary runway operations and to seek better lift, the pilot opted to launch from an area approximately 150 meters from the runway threshold where the grass had not been mown and stood approximately 50 cm high.
During the takeoff roll, the aircraft initially maintained a correct heading despite a slight left wing tilt. However, as the pilot attempted to transition to a climb at approximately 80 km/le, the right wing encountered the tall grass. This caused the aircraft to veer sharply from its course. The glider lifted off the ground at a significant bank angle of approximately 50 degrees. The winch operator subsequently released the cable, and the aircraft landed with a heavy bank, causing the tail boom to snap upon impact with the ground. The aircraft came to a rest 15 meters from the initial deviation point.
The investigation
The PKBWL investigation focused on the pilot's decision-making and the aircraft's interaction with the terrain. The investigation established that while the pilot was fully qualified and held the necessary licenses, this was his first flight in this specific aircraft type. The investigators examined the takeoff conditions, the height of the grass, and the pilot's reaction to the loss of directional control.
Findings
- The primary cause of the accident was the pilot's failure to release the winch cable immediately after the aircraft lost significant directional control.
- The pilot's decision to perform a takeoff from an area with unmanaged, tall grass contributed to the incident.
- The pilot's lack of familiarity with the specific handling characteristics of the GROB 103 Twin Astir played a role, specifically regarding the low clearance of the wing roots relative to the fuselage in this mid-wing design.
- The use of aileron inputs to correct the wing tilt increased aerodynamic drag, which further exacerbated the loss of direction.
- The aircraft sustained significant damage, including a broken tail boom and a damaged horizontal stabilizer.