Air-to-air refuelling, in which a military aircraft tops up its supplies by plugging in to a pipe trailing from a tanker plane, is a key military capability and one of the trickier piloting feats. Now that robots can do it, unmanned aircraft can potentially stay airborne for very long periods, limited only by maintenance requirements.
DARPA announced (pdf) last week that it had successfully completed a programme called AARD, for Autonomous Airborne Refueling Demonstration, and the story appeared yesterday in theDefence Industry Daily.
Over the past year, the AARD system* has apparently conducted 11 air-to-air refuelling flights without human input. The trials took place using an F-18 fighter jet operated as a testbed by NASA. The F-18 had a human pilot aboard during the trials as a backup, but the droid pilot required no help from its meatsack passenger. It was able to jack the F-18's fuelling probe into a basket trailing behind a refuelling tanker in the toughest of conditions.
Not only did the robo-flyboy manage to hook up with the trailing fuel point flapping up and down in turbulence by up to five feet - apparently the limit for most human stick-jockeys - it could also plug in while the tanker was turning.
"Although pilots routinely follow a tanker through turns while connected, they typically do not attempt to make contact in a turn," says DARPA.
The software improved significantly during the trials, according to NASA test pilot Dick Ewers. Last year it flew "like a second lieutenant", he said. But the robot rookie was upgraded, and now it's "better than a skilled pilot". If it was human, it would now retire and go to work for the airlines, and the military would have to start again with a another second lieutenant; but the robot will stay this good forever, or improve.
DARPA said that in the end the "algorithms were actually able to precisely match the drogue motion – something pilots are specifically taught to avoid... the system followed the drogue through a full three-foot cycle in the two seconds before making contact, never deviating more than four inches from the exact centerline of the drogue, all the while traveling at 250mph, 18,000 feet above the Tehachapi Mountains".
Human pilots, rather than tracking the drogue, are taught to try and slot in with a forward move at the right moment.
But now, yet another of their hard-won manual skills has been mastered by the droids. Things don't look good for the military flyboys at all, in the long run. That said, the money which might buy robot aircraft is largely in budgets controlled by former pilots.