Incident Overview
On 26 June 2024 at approximately 1230 UTC, a Piper J3C-65 (registration G-BBLH) was being taxied along Taxiway L at London Biggin Hill Airport when it encountered the jet efflux from a Bombardier Global 6000 (registration M-SFPL) that was parked on an adjacent maintenance apron with its engines running. The pilot of G-BBLH reported that the aircraft was "aggressively" spun round and weathercocked clockwise into the jet blast. For several seconds, the pilot experienced total uncontrollability, during which the left wingtip struck the ground on at least two occasions, resulting in damage. The pilot declared an emergency to air traffic control, shut down the engine, and vacated the aircraft to prevent further damage. Onlookers from a nearby hangar assisted in moving G-BBLH away from the efflux zone.
Aircraft and Personnel
The Piper J3C-65, manufactured in 1943 (serial no. 10,549), was powered by one Continental Motors Corp A65-8F piston engine. The Bombardier Global 6000, manufactured in 1991 (serial no. 9,692), was powered by two Rolls Royce BR700-710A2-20 turbofan engines. Both flights were private. G-BBLH had one crew and one passenger on board; M-SFPL had two crew and no passengers. No injuries were reported among any occupants. The commander of G-BBLH held an Airline Transport Pilot's Licence, was 40 years old, and had 11,000 flying hours (100 on type). The commander of M-SFPL held an Airline Transport Pilot's Licence, was 48 years old, and had 8,500 flying hours (4,000 on type).
Aerodrome and Operational Context
Control of aircraft on the apron east of the F4 Holding Point, where M-SFPL was parked, was delegated to the maintenance organisation operating from it. The distance between the newly established apron and Taxiway L was limited, so jet efflux attenuation barriers were not installed. Instead, the airport and maintenance organisation agreed to install apron line markings designed by the airport and installed by the maintenance organisation. These ground markings near Taxiway L were aligned on an approximate north-westerly heading, intended to direct efflux diagonally away from the taxiway. An internal investigation by the maintenance organisation found a "level of normative practice" where aircraft were parked along the apron rather than in alignment with the taxi markings, reducing the area available for appropriate positioning.
Sequence of Events
At the time of the accident, M-SFPL was parked on a northerly heading with engines running. The pilots of M-SFPL were not aware that G-BBLH was about to taxi behind them and had initiated a test of the wing anti-ice (WAI) system. On the G6000, activating WAI results in an increased engine idle thrust setting. The pilot of G-BBLH was not aware that M-SFPL had started its engines before taxiing behind it.
Investigation Findings
The investigation determined that the conditions for the accident were created when M-SFPL was parked perpendicular to the apron edge for engine start rather than in alignment with the yellow ground markings. The investigation did not have sufficient evidence to determine whether the increased engine idle thrust setting during the WAI test was a significant contributory factor. The maintenance organisation undertook safety action to remind their operations team of the requirement to align aircraft with the apron ground markings prior to engine start.