What happened
On 30 June 2017, a Piper PA-28-161 operated by Blue Skies Aviation Oy was performing a training flight at Siljansnäs Airport in Dalarna County, Sweden. The flight was part of a cross-country training program involving an instructor and two students. During the take-off phase, the aircraft rotated at an airspeed significantly lower than the recommended speed for its weight.
After lifting off, the aircraft failed to maintain altitude, sinking back onto the runway on two separate occasions while the aural stall warning sounded continuously. The instructor took control of the aircraft in an attempt to recover, but the aircraft continued to fly at a high pitch attitude. In an effort to clear obstacles, a banked turn was executed, which further degraded the flight condition. The aircraft eventually stalled a second time and crashed into a nearby cornfield. The instructor sustained one injury to the chest caused by an uncertified GPS screen mounted on the steering wheel.
The investigation
SHK investigators analyzed video footage from a GoPro camera mounted in the rear seat, which allowed for the calculation of engine RPM, pitch angles, and airspeeds. The investigation established that the aircraft's takeoff mass exceeded the maximum permitted limit by 70 kg. Additionally, the crew had exceeded their maximum daily duty time by over two hours at the time of the accident.
Investigators also examined the airport environment, noting that the windsock's position behind a forest may have led to an inaccurate assessment of wind conditions. The investigation also reviewed the aircraft's stall warning system and the impact of the crew's use of active noise reduction (ANR) headphones on their ability to perceive cockpit alerts.
Findings
- The primary cause of the accident was the failure to apply prescribed operational take-off procedures regarding the required rotation airspeed, which created a condition where aerodynamic drag exceeded available engine thrust.
- The aircraft was operating with a mass and balance that exceeded permitted limitations.
- The assessment of wind conditions was likely compromised by terrain-induced disruption of the windsock's visibility.
- The execution of a banked turn to avoid terrain at low airspeed worsened the stall condition.
- The lack of specific instructions in the operator's manual regarding procedures for a rejected take-off may have contributed to the decision to continue the rotation despite the loss of altitude.