What happened
On 4 September 2012, a Schempp-Hirth Nimbus-3 glider, registration G-EENN, was undergoing a winch launch at Portmoak Airfield, Scotland. The pilot had positioned the aircraft approximately 31 metres south of the standard launch area to avoid a patch of bad ground. During the early stages of the launch, the right wingtip made contact with the ground. As the aircraft accelerated, the right wing continued to run along the grass for approximately 51 metres. The aircraft eventually became airborne but entered an unrecoverable state, cartwheeling to the right and coming to rest in an inverted position. The pilot sustained one fatal injury.
The investigation
The AAIB examined the wreckage and the launch site, noting ground marks consistent with the right wing dragging along the surface. Analysis of the aircraft's cockpit revealed that the cable release handle was positioned in a way that could potentially interfere with the full range of movement of the control column. Testing on a similar Nimbus-3 demonstrated that when the release handle is operated, the control column's movement can be restricted, specifically limiting the ability to achieve full aileron deflection. The investigation also reviewed the winch setup, finding the cable positioning and the winch settings to be appropriate for the aircraft type.
Findings
- The aircraft was positioned significantly offset from the winch cable, which likely introduced a rolling moment towards the right.
- The right wingtip contacted the ground during the launch, creating significant drag that increased the yawing and rolling momentum.
- The pilot did not release the winch cable in time to prevent the aircraft from entering an unrecoverable roll and subsequent cartwheel.
- The physical arrangement of the cable release mechanism in the G-EENN cockpit may have restricted the pilot's ability to use full control authority while attempting to operate the release.
Safety action
- Safety Recommendation 2013-009: It is recommended that the European Aviation Safety Agency (EASA) require Type Certificate holders of EASA TC gliders to ensure that the cable release can be operated without restricting any flying control movement.
- Safety Recommendation 2013-010: It is recommended that the British Gliding Association (BGA) ensure that, where practicable, the cable release on EASA Annex II gliders can be operated at any stage of the launch without restricting control movement.