SKY-HIGH REFUELING DRONE FILL-UPS CAN BE DONE IN MIDAIR FIRST-EVER AUTONOMOUS AIRBORNE OPERATION CARRIED OUT WITH NASA F/A-18 FLIGHT.

Byline: Daily News

EDWARDS AIR FORCE BASE -- A joint test by NASA and the Defense Advance Research Projects Agency demonstrated it is possible to refuel pilotless drones in flight, allowing them to fly farther and longer, officials said.

The first-ever autonomous probe-and-drogue airborne refueling operation was done Aug. 30, using a NASA F/A-18 carrying pilots but equipped to find the refueling tanker's fuel basket without the pilots' intervention.

The Autonomous Airborne Refueling Demonstration system used GPS-based relative navigation, coupled with an optical tracker, to provide the precise positioning required to put a refueling probe into the center of a 32-inch basket dangling in the air stream behind the jet refueling tanker.

The tanker was equipped with a small relative navigation pallet, but production refueling equipment was not modified in any way, officials said.

Pilots were on board the F/A-18 for safety purposes, but they put their hands up and away from the controls as the plane connected itself to the tanker.

``This flight is a significant milestone -- it demonstrates that autonomous systems can employ the benefits of air-refueling that have proven so valuable to military aviation,'' said Lt. Col. Jim McCormick, DARPA program manager.

Researchers chose to demonstrate the probe and drogue refueling method -- used by the U.S. Navy -- because it is the most challenging for autonomous systems, McCormick said. The demonstration applies equally to the boom and receptacle method used by most Air Force aircraft, he said.

The same technology also promises to enhance reliability, safety and the range of operating conditions for midair refueling of manned aircraft, officials said.

The flight was the seventh of eight planned for the 15-month AARD proof of concept program.

For this particular test, the pilot provided approval to proceed at several stages of the maneuver, but was otherwise hands-off.

Operationally, unmanned systems are expected to locate the tanker, form up, accept clearances, refuel, and disengage without any human intervention.

``The end-game movement of the autonomous system had none of the last-second, high-gain stabs at the basket that we often see with human pilots,'' NASA test pilot Dick Ewers said.

When it missed, it was just as smooth while backing up to a restart point, he said.

The system engaged the refueling basket in two out of six attempts, which were made under tight tolerances for what constituted a miss, officials said. During one of the missed attempts, the pilot observed the probe was actually inside the basket when the system pulled back.

More robust tracking algorithms and relaxed miss tolerances are planned to be demonstrated on a final flight later this month.

DARPA initiated the program under the former Joint Unmanned Combat Air Systems program, which was aimed at creating small pilotless bomber aircraft.

The system was developed by Sierra Nevada Corp., with team member OCTEC Ltd. providing the optical tracking system.

Omega Air Refueling Services operated the modified 707-300 tanker used for the tests.

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(color) NASA pilot Dick Ewers and Flight Test Engineer Marty Trout fly hands-off Sept. 7 during the first-ever fully autonomous air refueling demonstration.

NASA