Wanted To See If UAV Would Correct Problem Autonomously

The decision to allow a unmanned aerial vehicle to correct its final approach course without human intervention appears to have led to the July 28 loss of an experimental Raytheon Cobra UAV, which was under evaluation by crews at the US Air Force Academy in Colorado Springs.

According to National Transportation Safety Board's preliminary report on the accident, officials were demonstrating the plane to academy staffers when the accident occurred. The flight started uneventfully, with the UAV performing all its preprogrammed maneuvers.

It was when the plane set up for its landing, though, when things took a turn for the worse... literally. According to the NTSB, the Cobra undershot its preprogrammed turn from base-to-final... forcing the crew to command the plane to execute a go-around, which it did successfully. On the second attempt, however, the Cobra overshot the final turn waypoint.

"The Raytheon team elected not to take over manual control because they reportedly wanted to see if the aircraft would correct its flight path," the Board writes. "The aircraft began to correct, but during the maneuver impacted stadium-style lights on a light pole. The right wing separated and became stuck in the lights. The remainder of the UAS fell to the ground."

The NTSB adds the purpose of the flight was to test the Cobra's ability to control itself, in the event of control-link loss. Prior to the flight, the Raytheon team surveyed the athletic fields and programmed in the GPS waypoints into the autopilot; except for the apparent problem with the final turn fix, the Cobra performed its rectangular autopilot route with no problems noted.

FMI: Read The Full NTSB Prelim, www.raytheon.com