What happened
On June 7, 1965, a Sokol Mid aircraft, registration HB-TAX, attempted a takeoff from the Sitterdorf airfield. The pilot, who was accompanied by two passengers, had previously completed two successful flights earlier that afternoon. However, during the third takeoff attempt at approximately 15:57 MEZ, the aircraft encountered difficulties on the grass runway, which had become soft and heavy due to heavy rainfall the previous day.
The aircraft failed to achieve sufficient lift until approximately 100 meters before the end of the runway, lifting off at a speed of roughly 100 km/h. To avoid a 2.5-meter-high hedge located at the end of the runway, the pilot initiated a rightward maneuver. This movement prevented the pilot from maintaining enough airspeed to climb effectively. Consequently, the aircraft lost altitude and speed, causing the underside of the aircraft—specifically the right wing—to strike a fence that stood approximately 2 meters above the runway level.
Following the impact, the pilot managed to land the aircraft without further damage. At the time of the landing, the landing gear and flaps remained in their takeoff configuration as the pilot had not yet had the opportunity to adjust them.
The investigation
The investigation examined the runway conditions, the aircraft's performance, and the pilot's decision-making process. Investigators noted that the takeoff weight was approximately 700 kg, well within the maximum allowable weight of 780 kg. The investigation also reviewed the pilot's flight experience and the environmental factors, including the weather conditions, which were nearly calm with some cloud cover and a slight influence from the Föhn wind.
Findings
- The primary cause of the accident was that the takeoff was not aborted in a timely manner despite the degraded runway surface.
- The soft, waterlogged condition of the grass runway contributed to a delayed rotation and insufficient takeoff roll.
- The necessity of an evasive maneuver to avoid a hedge resulted in a loss of airspeed and altitude.
- There were no injuries to the pilot or passengers, though the aircraft sustained damage to the underside of the wings, particularly the right wing.