What happened
On May 14, 2019, at approximately 17:12 local time, a pilot departed from Birrfeld Airport, Switzerland, in an amateur-built Alfa HB 207 VRG for a private VFR flight. The flight was planned to include a route via Konstanz and Wangen-Lachen before returning to Birrfelle.
Following a normal takeoff, the pilot retracted the landing gear while in a steady climb. GPS data and dashcam footage from a witness indicate that approximately 32 seconds after liftoff, the aircraft entered a left-hand turn. During this phase, the aircraft's true airspeed decreased significantly. The BFU investigation suggests that a loss of engine power likely occurred during this initial climb.
As the aircraft continued into a turning maneuver, the pilot attempted to maintain the course, but the airspeed dropped to approximately 102 km/h, which was below the required stall speed for the aircraft's bank angle. This led to an accelerated stall, causing the aircraft to wing over to the left and roll inverted. The aircraft then descended in a near-vertical attitude, impacting the ground and catching fire. The pilot sustained fatal injuries, and the aircraft was destroyed.
The investigation
The BFU reconstructed the flight path using GPS data from a Garmin 296 device carried on board and dashcam footage from a nearby motorist. The investigation included a technical examination of the wreckage at the SUST facility in Payerne.
Investigators examined the engine and fuel systems, noting that while the engine was too damaged to definitively confirm the cause of a power loss, the drop in airspeed was highly indicative of a partial or total loss of thrust. The investigation also reviewed the aircraft's maintenance history, noting that the owner-operator had performed the most recent 100-hour inspection just one day prior to the accident. Medical examinations of the pilot revealed chronic heart conditions that could explain arrhythmias, though the BFU found no evidence that a medical emergency incapacitated the pilot, as the aircraft's flight controls were actively manipulated to stop the roll after the stall began.
Findings
- The aircraft entered an accelerated stall due to the combination of a likely loss of engine power and the high bank angle maintained during the turn.
- The pilot's airspeed fell below the critical threshold required to maintain flight in a turning configuration.
- The altitude at the time of the power loss (approximately 129 meters) provided insufficient margin to recover the aircraft after the stall occurred.
- The aircraft's handling characteristics near the stall speed were noted by previous instructors as demanding and less forgiving.