What happened
On 16 August 2023, a Schleicher ASW 24, registration G-CHBB, was performing a private aerotow launch from Dunstable Airfield. During the initial stages of the takeoff roll, the glider's vertical position behind the tug aircraft became unstable. Shortly after the towing aircraft lifted off, the connection between the glider and the tug was lost.
While the glider initially climbed to a height of between 50 and 100 feet, it subsequently entered a steep left turn. During this maneuver, the aircraft's airspeed decreased, leading to a wing drop and an incipient spin. The glider struck the ground nose-first, resulting in one fatality.
The investigation
The AAIB investigation examined the aircraft, the tow rope, and the flight data recorded by GNSS-based systems. Investigators found that the tow rope remained intact, with the weak link and connecting rings still attached to the glider's end, and the release mechanism appeared to be functioning normally. No mechanical defects were identified in the glider's tow release system or flight controls.
Analysis of the flight path via GPS data confirmed that the distance between the tug and the glider began to diverge early in the launch. The investigation also reviewed the pilot's decision-making process, noting that while the pilot attempted to turn back toward the airfield, the low altitude and airspeed made this maneuver unachievable.
Findings
- The tow rope detachment occurred at a critical, low-altitude stage of the launch, though the exact cause of the release could not be determined.
- The pilot likely experienced the negative performance-shaping effects of startle and surprise following the unexpected loss of traction.
- The decision to attempt a turnback to the airfield, rather than landing ahead of the aircraft, led to an unsustainable flight regime.
- The glider entered an uncontrolled spin due to the high angle of bank and insufficient airspeed during the turn.