What happened
On December 23, 2008, a private PIPER PA 46-310 P 'Malibú', registration EC-KVQ, was preparing for a flight from Pamplona Airport to Sabadell. The flight was scheduled under IFR/VFR rules, but the departure was delayed due to engine starting issues. At the time of takeoff, the airport was experiencing low visibility (20/600m) due to fog and freezing conditions.
During the takeoff roll on runway 33, the aircraft rotated at 80 knots. Once airborne and reaching 90 knots, the pilot noticed that the vertical speed indicator showed zero climb rate and the continuous stall warning alarm activated. The aircraft was only approximately 2 meters above the runway. To avoid flying into the dense fog without a positive climb rate, the pilot decided to immediately execute an aborted takeoff, reducing power and maintaining speed to land back on the runway.
Upon touchdown, the brakes caused the wheels to lock. As the aircraft reached the end of the runway, it lost adhesion on the concrete surface. The pilot attempted to steer away from runway lights, but the aircraft slid off the runway into a dirt area, eventually coming to a stop at a 60-degree angle to the runway axis. There were 3 occupants (one pilot and two passengers), all of whom were uninjured.
The investigation
The investigation focused on the aerodynamic performance of the aircraft and the impact of the prevailing weather conditions. Investigators examined the aircraft's systems, including the Pitot-static system and the stall warning sensor, to determine if ice had obstructed the instruments. The investigation also reviewed the pilot's pre-flight inspection, where the pilot had noted and manually removed a light layer of frost from the wing leading edges.
Findings
- The primary cause of the incident was ice formation on the aerodynamic surfaces of the aircraft.
- This ice accumulation resulted in a loss of aerodynamic efficiency, requiring a higher angle of attack to maintain flight and preventing the aircraft from achieving a positive rate of climb.
- The continuous stall warning was likely triggered because the aircraft was flying at a speed near its stall threshold due to the degraded lift.
- While the pilot had cleared some frost during the pre-flight inspection, the freezing fog conditions during the takeoff roll allowed for further ice accumulation.
- The aircraft sustained significant damage, including a broken propeller, a collapsed nose gear, and a deformed engine mount.