What happened
On 13 June 2014, a Sikorsky 269C helicopter was conducting a scheduled annual proficiency check at the Cerfontaine airfield (EBCF) in Belgium. The flight, which involved a pilot and an examiner, began normally with two completed circuits. However, during the final approach for the second circuit, the aircraft's descent slope became too shallow. In an attempt to correct the glide path, the pilot increased the collective pitch without sufficiently monitoring the engine or rotor RPM. This resulted in a rapid decay of rotor speed. As the aircraft descended to a height of approximately 30 meters, the engine began to run roughly. During the subsequent attempt to recover, the pilot handed control to the examiner, but the engine stopped, causing the helicopter to fall vertically from a low altitude. The impact destroyed the aircraft, resulting in 1 fatal injury and 1 seriously injured person.
The investigation
AAIU(Be) investigators examined the wreckage and flight data to determine the sequence of events. The investigation focused on the aircraft's mechanical state, the pilot's performance, and the examiner's oversight. Technical analysis of the engine revealed a failed spark plug and the presence of unapproved grease on the magneto high-tension leads. While the tail rotor cable showed wear, investigators determined it failed only upon impact. The investigation also scrutinized the pilot's recent flight experience and the examiner's use of an active noise-cancelling headset, which may have masked the audible signs of the declining rotor RPM.