What happened
On 7 August 2019, a 15-year-old pilot was conducting a private flight near Skelling, Cumbria, in an SB-5E glider, registration G-DEJH. After several training flights and check flights earlier in the week, the pilot attempted to fly along the ridges of the Pennines. During a second pass along the summit of Cross Fell, the aircraft was flying at a low altitude, estimated at less than 100 ft, following a path behind the ridge.
Witnesses on the ground, including hikers, observed the glider performing a low-level pass. Video footage captured by a bystander showed that the aircraft's V-tail began to oscillate laterally. Shortly after, a loud cracking sound was heard as the tail section separated from the fuselage. The loss of the empennage caused the glider to pitch nose-down, striking the ground with the right wing first. The pilot sustained serious injuries.
The investigation
The AAIB examined the wreckage at the summit of Cross Fell and analyzed mobile phone video of the accident. The investigation focused on the structural integrity of the tail section and the aerodynamic conditions during the flight. The wreckage showed significant damage, with the fuselage largely disintegrated and the V-tail components twisted.
Investigators reviewed the aircraft's maintenance records, including the use of adhesives and the status of Airworthiness Directives. They also examined the pilot's training records, logbook, and the cockpit instrumentation, specifically the airspeed indicator (ASI) and the speed limitation placards. The investigation also looked into the briefing provided by the Chief Flying Instructor (CFI) regarding ridge flying techniques and local weather conditions.
Findings
- The primary cause of the accident was structural failure of the tail section due to flutter.
- This flutter likely occurred while the glider was operating at a speed between the indicated Rough Air speed limit and the maximum operating speed (VNE).
- The airspeed indicator and cockpit placards contained incorrect speed limitations, which had likely been erroneously copied from incorrect sources for decades.
- The pilot's practical experience with ridge flying was limited, and his understanding of the local terrain was partially based on information from a peer rather than formal instruction.
- Incomplete pilot training records led to an inaccurate assessment of the pilot's flying experience by the host club's instructor.
- The aircraft's design features, specifically the lack of mass balancing on the ruddervators, made the airframe more susceptible to aeroelastic flutter.
Safety action
- The BGA has introduced a new national syllabus for hill and ridge soaring to standardize training.
- New protocols have been established for the supervision of junior pilots (under 18) flying on ridges.
- The BGA has updated its guidance to emphasize that public safety must be the absolute priority, specifically instructing pilots never to fly close to or directly over people on the ground.