What happened
On 25 June 2023, an amateur-built DB-6R balloon, registration G-CMFS, was participating in the British Grand Prix 2023 series. The flight was part of a competition event involving several balloons, with the aircraft launched from Worcester Racecourse. After successfully dropping a marker at a target near Ombersley Park, the balloon began a rapid ascent.
Witnesses and other pilots observed the balloon climbing quickly, noting grey smoke emanating from the area. Shortly thereafter, the balloon's appearance changed significantly; observers described the envelope looking distorted, as if it had lost internal pressure. One witness noted the flame from the burner appeared to be hitting the outside of the fabric. The balloon then entered a 'streamered' state, with the fabric trailing behind the basket, and descended rapidly to the ground at Ombersley Court. The pilot, who held a Commercial Pilot’s Licence, sustained 1 fatal injury.
The investigation
The AAIB investigation examined the aircraft, the flight logs, and witness accounts from other competitors and bystanders. The investigation focused on the mechanics of the envelope's failure and the environmental conditions at the time of the accident. Investigators analyzed the behavior of the balloon's vent system and the impact of the rapid climb on the internal pressure of the envelope. The investigation also reviewed the design of the amateur-built aircraft and the operational procedures of the competition.
Findings
- The balloon likely experienced a parachute stall, a condition where the vent fails to reseal properly.
- The rapid rate of climb, combined with the specific balloon design and existing wind gradients, contributed to the failure.
- The envelope's structural integrity was compromised during the ascent, leading to the rapid deflation and subsequent descent.
Safety action
To improve safety within the ballooning community, the following recommendations were made:
- The British Ballooning and Airship Club (BBAC) should develop better reporting cultures and provide guidance on preventing and recovering from parachute stalls and the emergency jettisoning of fuel tanks.
- The Civil Aviation Authority (CAA) should provide guidance regarding the oversight of competition ballooning and the design, testing, and inspection of amateur-built balloons.