What happened
On the morning of April 14, 2007, a Pilatus PC-6 B1-H2 (registration EC-JOE) was performing a reconnaissance flight for scheduled parachuting operations at the Casas de los Pinos Aerodrome in Cuenca. During the landing phase on runway 30, the aircraft veered off the paved surface.
The pilot reported that during the flare, a gust of wind lifted the left wing. In an attempt to maintain control and level the aircraft, the pilot applied left rudder and bank, but the aircraft subsequently exited the runway. The aircraft traveled approximately 50 meters off the runway, striking the ground at a downward angle. The impact caused the left main landing gear to detach and the propeller to separate from the engine at the reduction gearbox. The aircraft eventually came to a stop on its fuselage.
Both the pilot and the passenger were able to exit the aircraft under their own power. The pilot sustained a minor injury to his chin, while the passenger was unhurt. The aircraft sustained serious damage, including a cracked cockpit windshield, a damaged fuselage underside, and structural damage to the tail section and left aileron.
The investigation
Investigators examined the wreckage, maintenance logs, and meteorological data. The inspection of the aircraft's braking system revealed that the coating on the left brake was worn beyond limits; however, because the aircraft did not touch down on the runway, the brakes were never applied and could not have contributed to the excursion.
Regarding the flight parameters, the investigation noted that the pilot conducted the approach at 70 knots without the use of flaps. Given the aircraft's weight at the time, this speed provided a safety margin of approximately 20 knots above the stall speed. While the pilot attributed the event to a wind gust, meteorological data from the time did not confirm the presence of significant turbulence or gusts.
Findings
- The aircraft was fully compliant with all required certificates, licenses, and maintenance schedules.
- The damage to the landing gear, propeller, and fuselage was determined to have been caused by the impact of the excursion itself, rather than pre-existing mechanical failures.
- The pilot's approach speed was sufficiently high to maintain control even in the presence of gusts, making the unexplained alteration of the aircraft's flight path the central mystery of the event.
- The investigation could not definitively confirm the presence of a wind gust sufficient to cause a stall, nor could it determine why the aircraft's path was altered at low altitude.