What happened
On July 25, 2010, a private flight involving a B&F TECHNIK FK 14B Polaris, registered OO-G15, ended in a fatal accident in a field between Nivelles and Genappe. The pilot, who was conducting familiarization flights, had arranged to hire the aircraft from a local provider. During the flight, witnesses observed the aircraft flying in a horizontal attitude before it suddenly dropped and entered a left-hand spin. One witness also reported hearing a detonation and seeing a parachute deploy near ground level. The impact of the crash killed both the pilot and the passenger.
The investigation
Investigators from the AAIU(Be) examined the wreckage and the flight history of the occupants. The pilot held a Belgian ULM training license and a French UML pilot license, while the passenger was a highly experienced former ULM instructor. The investigation focused on the aircraft's weight and balance, the contents of the flight manuals, and the effectiveness of the Emergency Parachute Recovery System (BRS).
Analysis of the aircraft's weight revealed that the OO-G15 was approximately 40 kg in overload at the time of the accident. Discrepancies were also found between the manufacturer's manual and the local flight manual provided by the aircraft owner. While the BRS was activated, the altitude was too low for the parachute to fully develop its intended effect. Additionally, the investigation found that the shoulder harness cables were not sufficiently strong to withstand the impact forces.
Findings
- The aircraft was technically airworthy prior to the impact, with no mechanical failures identified.
- The aircraft was flying at a very low speed, close to its stall speed, during the final moments of flight.
- The flight was conducted at an altitude too low to safely perform low-speed or stall-related maneuvers.
- The aircraft was operating in an overloaded state due to inaccurate empty weight data in the provided flight manual.
- The local flight manual lacked critical warnings regarding the dangers of stalls and spins, even suggesting that pilots could test stalls by manipulating the throttle.
- The aircraft lacked a stall warning system or stall strips to provide aerodynamic buffet to the pilot.
Safety action
Following the investigation, several safety recommendations were issued:
- The Belgian ULM Federation was advised to encourage pilots to perform low-speed exercises only at safe altitudes and to use actual, rather than estimated, empty weight data for weight and balance calculations.
- The Belgian CAA was recommended to regulate flight manuals to ensure they include all original manufacturer warnings and accurate weight data.
- B&F TECHNIK was advised to implement stronger cables for shoulder harness connections and to improve stall indication through electrical warnings or stall strips.