What happened
On June 27, 1999, a Piper PA 28-236 "Dakota," registered as HB-PNF, was conducting a VFR circuit flight at Birrfeld airport with three passengers on board. As the pilot approached for landing on runway 26, another aircraft remained on the runway, necessitating an aborted landing.
Due to deteriorating weather conditions and an approaching thunderstorm, the pilot attempted to shorten the circuit. During the turn into the crosswind leg, the aircraft's stall warning activated. Despite applying maximum engine power, the aircraft began to descend. The aircraft struck a roadside embankment, causing the right wing to detach, and eventually impacted a cornfield. The pilot and passengers sustained light injuries.
The investigation
The investigation examined the aircraft's mechanical condition, the pilot's flight parameters, and the prevailing meteorological conditions. Investigators found no technical defects in the Piper PA 28-236; the engine was producing power at the time of impact, and all flight controls were functional. The aircraft's weight and balance were within legal limits.
Meteorological data revealed that a cold front was moving through the region, bringing heavy rain and significant wind shifts. A wind warning had been issued for the area earlier that day, predicting gusts of up to 29 knots. The investigation also noted that the aircraft's flaps remained in position 2 during the maneuver, which hindered acceleration.
Findings
The primary cause of the accident was the insufficient climb performance resulting from the aircraft encountering a downdraft and a sudden, high-velocity tailwind component. As the pilot turned into the crosswind leg, the wind direction shifted, creating a tailwind of up to 40 knots, which abruptly reduced the aircraft's airspeed.
Contributing factors included:
- Poor flight tactics during the go-around maneuver in close proximity to a thunderstorm.
- The decision to continue circuit training despite clear warnings of severe wind and convective activity.
- An inappropriate flap setting for the flight configuration, which negatively impacted the aircraft's ability to accelerate.
Safety action
It is strongly recommended that pilots and front-seat passengers wear seatbelts to prevent facial injuries during impact.