What happened
On 19 December 2002, an Avions Pierre Robin CEA DR3CO/180R, registration G-BVYM, was performing a private flight near Dunstable. The aircraft, which is used for towing gliders, was returning to the airfield following a tow operation. Due to the wind direction, the pilot had to fly an approach path that crossed a road running along the northwestern edge of the airfield.
During this approach, the aircraft descended too low over the boundary near the road. The trailing tow rope, which was 216 feet in length, became entangled with three-phase 11,000 volt power wires supported by wooden poles. The impact caused three of the power wires to break. Although the tension on the rope caused the weak link—rated at 1200 lbs—to fail as intended, the aircraft was able to land safely without any damage to the airframe or injuries to the pilot.
The investigation
Investigators examined the local topography and meteorological conditions at the time of the incident. The airfield is situated near the Chiltern Hills, and the wind was reported at 090 degrees with gusts up to 28 knots. These conditions were known to create significant turbulence and downdraughts near the airfield boundary.
Technical analysis focused on the length of the tow rope and the approach altitude. It was noted that the rope used was approximately 30 feet longer than the standard length typically used by the club, though it remained within the maximum limits set by the British Gliding Association. The investigation also looked at the established procedures for landing with a rope attached, which usually requires a high approach to mitigate the risk of sink rates causing the rope to drag on the ground before reaching the airfield.
Findings
- The primary cause of the incident was the aircraft's low altitude over the airfield boundary during the approach.
- Strong local downdraughts, caused by wind blowing over the nearby ridge, likely contributed to the descent.
- The use of an extended tow rope length, which was 216 feet, acted as a contributing factor.
- The failure of the rope's weak link functioned as designed, preventing further damage to the aircraft.