Date:20 July 2012
HOW A LOOSE SCREW DOWNED A R580 MILLION AIRCRAFT
The US Air Force recently released the results of an investigation into the crash of a Global Hawk unmanned aerial vehicle that had been flying over Afghanistan. As in many aviation accidents, a small oversight led to a catastrophic failure. No one was injured, but the military lost one of the few Global Hawks confi gured as a beyondline-of-sight communication relay. – BY JOE PAPPALARDO
1 The EQ-4B Global Hawk is flying 190 km north of Kandahar, Afghanistan. It’s being controlled by crew from Beale Air Force Base in California. At 1707 Zulu, 9,4 hours into the mission, controllers lose contact with the craft.
2 Radar tracks show the Global Hawk pitching into a deep death dive 25 seconds after it experiences lost link. On the way down, the wings separate from the fuselage.
3 Three minutes after contact is lost, the aircraft strikes the ground in the empty desert. US forces bomb the remains to prevent the enemy from using the wreck to glean classi ed information or for propaganda purposes.
The EQ-4B’s mission-management computer was unable to govern flight-control surfaces called ailerons. Insufficient apscrew torque (that is, a loose screw) appears to have allowed a wire to work free, sapping power from the onboard computer and causing the aircraft to tumble from the sky.
Lost link: When operators of an unmanned aircraft lose command and control. Military UAVs are pre-programmed to fly a contingency route to a rally point when this occurs; the malfunction that doomed the EQ-4B prevented it from completing this emergency command.