American air-safety authorities have issued a lengthy list of new recommendations regarding the operation of flying robots in US airspace, following the crash of a Predator drone on border-patrol duties last year.
The wrecked sky-droid was a Predator B, a large high-flying turboprop with a 65-foot wingspan which is known as the "Reaper" in the US Air Force service. Combat-equipped Reapers can carry as many as 14 Hellfire missiles, each capable of destroying a tank. In addition, the aircraft's surveillance radar can sweep vast acreages of ground in seconds, picking out any moving man-sized target for closer analysis by telescopic thermal camera.
The US armed forces have lost many unmanned aircraft in combat theatres overseas, but these crashes don't fall under the jurisdiction of civil regulators, and the details seldom become public. However, on April 25 2006, US Customs and Border Protection (CBP) - nowadays an agency of the musclebound Department of Homeland Security - had an unarmed Predator-B aloft near Nogales in Arizona, keeping an eye out for anyone with sinister yearnings to breathe free along the Mexican border. After a sequence of mishaps, the five-ton machine crashed into the desert at around four in the morning local time.
Very full details are available from the National Transportation Safety Board (NTSB) here. In brief, the problems started when the remote console from which the aircraft was being controlled "locked up". The aircraft continued to fly along happily, and indeed a CBP agent who was handling the camera at the system's other console seems to have carried on doing so.
However, the pilot wanted to regain control and decided to take over the CBP agent's console and switch command of the Predator to that. When piloting is switched between consoles, a certain lever changes its function from control of the camera iris to control of the fuel feed to the aircraft's engine. Apparently, the pilot failed to follow the changeover procedure properly, and the lever was left set in its middle position. This meant that as soon as the console took over the Predator, the engine shut down.
The Fall of The Machines
The pilot failed to realise that he had turned off the engine, but did notice that the aircraft was descending. He decided to turn off the control console altogether, hoping that the loss of a control signal would cause the Predator to go into fallback mode, in which it is supposed to climb autonomously to a safe height and fly a pre-planned route until it gets further orders.
However, the robot couldn't do this as its power had been cut off. Another pilot, who knew more about Predators, came in and spotted that the lever was in the wrong position at once, but attempts to get back in contact with the Predator and power it up were fruitless (this was because it had by now descended too low for radio comms, but the pilots didn't know this for sure).
Apparently, the aircraft's radar transponder also cut off following the loss of electric power from the engine. This caused several hours of panic for local air-traffic control as the pilots thought their aircraft was still flying in fallback mode and nobody could now see it on radar. In fact the Predator had crashed by now, but nobody knew that for sure owing to the genius-like decisions to first switch off the engine and then shut down the controls and communications.
Some people are seeing all this as an indication that unmanned aircraft aren't safe enough to fly in civil airspace. Another way of looking at it is that the pilots are the problem, and the sooner we get rid of them the better. ®