What happened
On 29 August 2013, a B&F Technik FK12 Comet, registration OO-F (as per the provided text), was performing low-level maneuvers at the Avernas airfield (EBAV). The pilot, who was also the aircraft owner, had taken off from the closed airfield to perform a flight demonstration for the 30th anniversary of a local aero club.
The flight involved flying at an extremely low altitude, between 10 and 15 meters above the ground, over the airfield's two aligned runways. The pilot was performing wingover maneuvers—steep climbs followed by vertical turns—while utilizing an onboard smoke generator that produced a continuous stream of light grey or white smoke. During the second or third repetition of this flight pattern, the aircraft entered a sudden descending turn and struck the ground on the northern runway at high speed. The impact resulted in one fatality and the total destruction of the aircraft.
The investigation
Investigators from the AAIU(Be) examined the wreckage and flight history to determine the cause of the impact. The investigation confirmed that the aircraft was in an airworthy condition and that no structural or flight control failures occurred prior to the crash. While evidence of inadequate maintenance regarding the fuel system was found, it was not considered a contributing factor to the accident.
The investigation focused on why the aircraft entered a descending turn at such a low altitude. Two primary hypotheses were considered: a sudden loss of visual and spatial references caused by the pilot flying through the layer of stagnant smoke, or a sudden medical event, such as a "greyout," triggered by the positive G-forces of the preceding pull-up maneuver.
Findings
- The pilot was highly experienced but known for performing unauthorized aerobatic maneuvers and extremely low-level flights.
- The airfield was closed at the time, and the pilot had not notified authorities or checked for military activity.
- The lack of wind caused the self-produced smoke to linger as a mist over the airfield, potentially obscuring the pilot's view.
- The aircraft entered a sudden descending turn likely due to pilot action related to visual disorientation or a physiological event.
- The pilot's previous unsafe flying had resulted in a 90-day flight prohibition at the airfield, which had only been lifted a few days prior to the accident.
Safety action
- The Belgian ULM Federation (BULMF) is encouraged to raise awareness regarding the dangers of pilot overconfidence and the risks of ignoring fundamental safety regulations.
- The federation is also advised to promote the importance of thorough fuel system inspections, particularly for aircraft that have been inactive during winter months.