Predator UAV Failure

An April 2006 crash of a Predator UAV near Nogales was indirectly caused by repeated software failures. As reported by USA Today:

No one was injured, but the plane slammed into a hillside near homes in a sparsely populated area north of Nogales, Ariz. A 'pilot' flying the single-engine turboprop plane from a trailer at a military base accidentally shut down the plane's engine while attempting to deal with a locked up computer control console, according to the NTSB.

The NTSB found several disturbing problems in their report:

• Computers used to control the Predator had locked up at least 16 times in the four months before the accident. The failures were not well documented and no attempt was made to determine what caused the problems.
• The drone's pilot was supposed to be monitored by a flight instructor, but none were around at the time of the outage.
• When the Predator's engine stopped, it cut electrical power to key instruments, including the radio transponder that made the plane visible to air-traffic controllers. This meant that nobody knew where the plane went, including other aircraft.
• The Predator's engine cannot be restarted without a radio link to the ground. By the time the operators realized the drone had lost power, it had descended behind mountains and radio contact was impossible.
• A report in C4ISR Journal mentions that the operator had attempted to transfer control to a secondary workstation. However, this procedure calls for the secondary workstation to be "identically configured" at the time of the transfer. The secondary workstation was configured in "fuel off" mode, so the drone obeyed this command.

The Predator B destroyed in the crash cost $6.5M.