Autopilot problems caused July QRF-4C drone crash


By Brian Everstine, Incorrect inputs to the autopilot brought down an unmanned targeting drone on July 13 in Florida, the Air Force announced Wednesday. The QRF-4C, a modified F-4 Phantom fighter jet, crashed eight seconds after takeoff from Tyndall Air Force Base, Fla.

An investigation found that the drone’s Attitude Heading Reference System, which controls the aircraft’s up and down movement, sent incorrect inputs for the horizontal pitch to the aircraft’s autopilot, causing the aircraft to pitch up and down rapidly.The system was defective, the report found.

The pilot in the ground-control station went through the proper emergency checklist and was unable to stabilize the aircraft. The drone pitched down 33 degrees and crashed into the runway and a barrier, according to the Air Force Accident Investigation Board report.

The drone, assigned to the 53rd Weapons Evaluation Group at Tyndall, was destroyed, along with a flare-dispensing pod and 120 flares. The total loss is valued at almost $4.6 million.

The drones are used as aerial targets for weapons testing and training, and are typically destroyed over the Gulf of Mexico. This crash closed nearby Highway 98 for about 24 hours before the wreckage stopped burning and was cleared.