History of Flight
On February 25, 2021, about 1126 central standard time, a Dassault Aviation Mirage F1B, registration N601AX, was substantially damaged during an accident at Tyndall Air Force Base (PAM), Panama City, Florida. Both pilots sustained serious injuries. The airplane was operated as a public aircraft under Title 49 of the United States Code Sections 40102 and 40125. The planned flight was conducted under a contract between Airborne Tactical Advantage Company (ATAC) and the United States Air Force to provide adversary training.
The accident airplane was the lead of a two-aircraft formation departure from runway 14R. During the takeoff roll, at about 125 knots indicated airspeed (KIAS) after crossing the arresting cable, the pilot reported a sudden swerve to the left. Full right rudder and right brake were applied without effect. The airplane drifted to the left edge of the runway, became airborne in ground effect, and climbed while in the same configuration (flaps and slats full, gear down). The pilot flew south over the water, orbiting to burn fuel and assess the airplane's condition. The second airplane aborted its takeoff.
While orbiting, the pilots reviewed emergency checklists and discussed possible failures. Nearby pilots provided a visual check of the landing gear and tires. The consensus was a left main landing gear issue. After coordinating with air traffic control, the pilot returned to land on runway 14L. Touchdown occurred near the right edge; the rear-seat pilot deployed the drag chute. The pilot felt a significant pull to the left after relaxing left-wing-up input. Full right rudder and brake were ineffective. The airplane departed the runway onto grass, the nose landing gear collapsed, and the rear-seat pilot initiated an unannounced ejection. The rear seat ejected successfully; the front seat did not. The airplane skidded across the grass and impacted a taxiway. Both occupants were rescued and sustained serious injuries.
Aircraft Information
According to ATAC’s Mirage F1 flight manual, the airplane was equipped with electro-hydraulic nosewheel steering (NWS) commanded by rudder pedals, available when the weight-on-wheels microswitch was compressed. The flight manual included a procedure for “Aircraft Swerves During Taxi” directing the pilot to verify the NWS caution light out, check rudder trim, turn off anti-slip switch, and if needed, turn off NWS. The airplane had ejection seats capable of ejection at all altitudes and speeds between 0 and 620 knots. A sequence selector in the front cockpit allowed solo or dual ejection. In the DUAL position, both seats were connected; a rear-cockpit-initiated ejection would eject the rear seat immediately, then the front seat after a 0.5-second delay. At the time of the accident, no limitation prevented operation from a runway equipped with an aircraft arresting system.
Wreckage and Impact Information
Examination of runway 14R revealed tire markings starting about 580 ft past the nearest arresting system, initially centered on the left side, then swerving left. Marks continued to where the airplane became airborne; left main landing gear was off the paved surface. A runway edge light was damaged. After sweeping, a missing anti-skid connector from the right main landing gear was found in the sweeper truck.
Landing runway 14L showed tire marks from nose and main landing gear veering left off the runway onto grass. Nose tire marks were closer to left main marks, consistent with a yaw. Marks crossed a “ramp” (about 18-inch rise) and continued; a floorboard piece and rear canopy fragments were found. The airplane came to rest upright with collapsed nose gear about 5,857 ft from the approach end of runway 14L.
Postaccident examination revealed the nose landing gear collapsed aft, anti-skid connector of right main landing gear separated, and the drag chute deployed. Cockpit rear canopy shattered from ejection; front canopy had a small break. All tires satisfactory except left nose tire (0 psi, torn). The anti-skid switch was off; NWS disconnect switch on with guard covering. Sequence selector set to “Dual.” The front ejection seat did not deploy.
Examination of the NWS system found the annular ball bearing outer race fractured with static load, no preimpact failure. Testing of the NWS distribution block showed the nose landing gear went uncommanded “immediately” to the left 45°, inconsistent with switch position, rudder pedal position, and system design.
According to the ejection seat manufacturer, the rear seat occupant initiated ejection at about 55 knots while the airplane was in a 10° nose-low attitude due to collapsed nose gear. The rear seat showed no issues. Inspection of the front seat revealed a broken lower attachment bolt, deformed upper bolt, and the ballistic time release unit “sear” activated, releasing harness locks and parachute. The disconnecting unit was disconnected from the front seat ballistic manifold, causing gas discharge into the cockpit. A pull test of connections showed no discrepancies.
Additional Information
A previous similar event occurred in May 2020 with a competitor operating a similar aircraft, attributed to crossing a raised arresting system. That operator prohibited crossing raised arresting gear at high speed. The accident operator was unaware until after the accident.
After the accident, the owner/operator implemented safety changes: updated policy prohibiting crossing raised arresting systems at high speed, one-time NWS and ejection seat inspections, a safety sharing agreement with a competitor, and hiring a subject matter expert. They also modified the flight manual for ejection decisions during runway excursions, developed immediate action procedures for runway excursion and loss of directional control on landing, and disseminated accident results to pilots and mechanics.