What happened
On August 22, 2020, at approximately 20:07 local time, an Air Tractor AT-802, registration EC-HOR, was performing takeoff operations at the La Resinera aerodrome in Granada, Spain. The aircraft, operated by Pegasus Aviación, had been engaged in firefighting duties for three hours prior to the incident.
During the takeoff roll on runway 27, the aircraft initially drifted to the right of the centerline. The pilot applied left pedal to correct the trajectory; however, the aircraft then swung sharply to the left and exited the runway. While traveling off the paved surface, the aircraft struck a 60 cm mound with its left wheel, causing it to lift slightly before dropping heavily onto its right main gear. The impact caused the right main gear to bend beneath the fuselage, though it did not fully collapse. The pilot, who was the sole occupant, was uninjured and evacuated the aircraft on his own.
The investigation
The investigation focused on the loss of directional control during the takeoff roll. Although the cockpit control lever indicated that the tailwheel lock was engaged, investigators found that the mechanism had not fully seated. The investigation revealed that the area around the locking pin was heavily contaminated with solidified fire retardant. This residue prevented the pin from completing its vertical travel, meaning the tailwheel was not effectively immobilized.
Because the tailwheel was not properly locked, it was able to rotate during the takeoff roll. This rotation, combined with the high engine torque characteristic of the aircraft's powerful engine, created an unpredictable yawing motion that the pilot could not stabilize with rudder inputs.
Findings
- The primary cause of the deviation was that the tailwheel was not locked during the takeoff roll.
- Solidified fire retardant residue prevented the locking pin from fully engaging in its designated position.
- The aircraft's high engine torque requires precise rudder compensation, which was rendered impossible by the uncontrolled rotation of the tailwheel.
- The aircraft had not been cleaned of retardant residue following previous operations, as no ground crew was available at the temporary base.
Safety action
- REC 32/20: It is recommended that Pegasus Aviación modify its "Firefighting Base Work Guide" to include a specific inspection item to verify that the tailwheel locking pin is correctly and fully positioned.