What happened
On June 30, 2017, a Piper PA-28-161 (registration OH-PHE), operated by Blue Skies Aviation Oy, was performing a training flight at Siljansnäs airport in Sweden. The flight was part of a long-distance training mission involving two students and an instructor. After refueling at Siljansnäs to reach maximum takeoff weight for a subsequent leg to Åre, the crew attempted a takeoff using a short-field procedure.
During the takeoff roll, the pilot rotated the aircraft at approximately 43 knots, which was significantly lower than the recommended rotation speed for the aircraft' and weight. Upon liftoff, the aircraft maintained a high pitch attitude, causing the stall warning to sound continuously. The aircraft impacted the runway twice before eventually crashing into a nearby crop field. During the sequence, the instructor took control to attempt to maintain flight, but a turn executed to avoid obstacles further exacerbated the situation. The instructor sustained injuries from a GPS screen mounted on the control column during the impact.
The investigation
The investigation examined the aircraft's performance, the crew's actions, and the environmental conditions. Investigators analyzed video footage from a GoPro camera mounted in the rear seat, which allowed for the calculation of engine RPM, rotation speeds, and pitch angles. The investigation also reviewed the aircraft's weight and balance, the meteorological data, and the operator's training manuals. The investigation confirmed that the aircraft's mass exceeded the maximum allowable takeoff weight by 70 kg. Furthermore, the investigation looked into the effectiveness of the stall warning system while the crew was using Active Noise Reduction (ANR) headsets.
Findings
- The primary cause of the accident was that prescribed operational takeoff procedures were not applied regarding the indicated rotation speed, resulting in an attitude where drag exceeded available thrust.
- The aircraft's takeoff mass was 70 kg above the maximum allowable limit.
- The rotation speed used (43 knots) was below the recommended speed for the aircraft's weight.
- The aircraft's weight and balance were outside of permissible limits.
- The placement of the airport windsock behind a wooded area may have led to an inaccurate assessment of wind conditions.
- The crew's use of ANR headsets may have made the stall warning harder to perceive initially, although testing showed the frequency was audible.
- A turn performed at low speed to avoid terrain likely worsened the stall condition.
- The operator's manual lacked detailed instructions regarding procedures for an aborted takeoff during a short-field attempt.
- A non-certified GPS screen mounted on the control column caused injuries to the instructor during the impact.