Incident
On 22 July 2021, at approximately 12:14 local time, a Robin DR 400/180 R, registration HB-KAW, was involved in an incident at Bex Airfield (LSGB) during the Swiss Junior and Western Swiss Gliding Championships. The aircraft was used as a towplane for launching gliders. After releasing a glider near Col de Bretaye, the pilot returned to Bex and attempted to retract the 54-meter tow rope using the automatic winch. The rope did not retract, as indicated by a cockpit gauge showing 100% rope extended. The pilot reported this on the radio.
During the final approach to Runway 33, the trailing rope struck the left wing tip of a glider positioned for takeoff. The impact rotated the glider approximately 100 degrees and separated its left winglet. A second glider sustained minor damage, and a person standing nearby sustained minor injuries. The tow rope broke, and the towplane's fuselage bottom and winch system were seriously damaged.
Aircraft and Crew
The towplane was a single-engine Robin DR 400/180 R, owned and operated by Vol à voile Club Valais, based in Sion. The pilot, a Swiss citizen born in 1982, held a valid PPL(A) issued by the Swiss Federal Office of Civil Aviation. He had logged approximately 572 total flight hours, with about 400 hours on the type, including 6 hours and 23 minutes in the preceding 90 days. This was his first tow operation at Bex airfield.
Investigation Findings
The investigation determined that while the pilot was aware the tow rope had not retracted, he proceeded with an approach that brought the aircraft low over the line of gliders waiting for takeoff. The report noted that a rope trailing behind a towplane at a typical approach angle can hang significantly lower than the aircraft. In this case, the aircraft flew approximately 10 meters above the gliders, making it impossible to clear them safely with the rope extended. The pilot was apparently unaware of the hazard posed by a trailing rope at low altitude.
The analysis highlighted that knots in the rope or malfunctions in the winch can prevent full retraction. Pilots and ground crew should be familiar with procedures for landing with an unretracted rope, such as using a clear runway or having observers report the rope's position. However, the report did not assign a specific probable cause.
Damage and Injuries
- Towplane HB-KAW: seriously damaged (fuselage bottom and winch system).
- Two gliders positioned on the ground: one seriously damaged (left winglet separated, rotated 100°), the other slightly damaged.
- One person (a helper of a competition pilot) sustained minor injuries.
No other injuries were reported.