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2007 AAR experiment
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Quick question: what’s the biggest limiting factor in today’s aircraft? Answer: the pilot. Fortunately for pilots, they’re also an aircraft’s greatest advantage, which will keep them in the mix, and in the cockpit, for some time to come. Those limitations are bringing unmanned aircraft into the combat picture, however, especially when it comes to the greatest limitation a pilot places on an aircraft: aerial endurance. Remaining awake, active, and effective in a manned fighter aircraft for 72 hours straight is simply not within the realm of possibility. On the other hand, a UAV with that endurance level, flown by pilots on the ground or at sea who can hand the aircraft off to a colleague while they depart for a coffee, bathroom break, or sleep, could easily remain aloft that long. All it needs is an appropriate level of mechanical reliability – and, of course, the ability to take on fuel from an aerial tanker aircraft.

That simple concept has profound implications for the ways in which airpower might be used. Imagine, for instance, a carrier with UCAS-D X-47s on board. The ship receives a crisis call for events 3,000 miles away – and immediately launches its armed complement of X-47 stealth UCAVs toward the area, while the rest of the carrier steams over to catch up. Pilots fly the aircraft via secure satellite links from duty stations within the ship, while USAF aerial tankers keep the X-47s fueled to maintain their surveillance and targeting “orbits” over the crisis area, or even slightly outside of that area. The aircraft are on station much faster, and remain so for a far longer period of time than would normally be possible. The result is effective power projection that attracts as little or as much attention as it chooses, while remaining available for very fast use in the target zone.

UAVs are already being flown over Afghanistan from duty stations near Las Vegas, so part of this scenario has already come true. The missing link? Aerial refueling. Unsurprisingly, Boeing is doing work in that very area. It’s an Air Force project, but a recent report suggests that the Navy’s X-47 may end up involved after all….

Program Goals: Phase II

X-47B Concept
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Work began with a 2005 contract to add this capability to its canceled X-45C UCAV, and was followed by successful 2006 and 2007 exercises that used an unmanned Learjet as a surrogate. These Phase I exercises demonstrated that a single UAV could safely maneuver among 7 refueling positions behind a tanker aircraft, and conduct a breakaway maneuver.

Now, the Phase II contract looks set to extend Boeing’s efforts – and take another step toward the kind of UCAV future outlined above. AAR also encompasses manned aircraft, which could also benefit from systems that are able to automate risky maneuvers like air-air refueling.

Phase II Spiral 1 involves designing and testing a multichannel precision-GPS relative navigation system, an automated flight control system, and the required command and control additions to guide the unmanned receiver to the manned tanker. Tests will use the air force’s boom system.

Under a planned Spiral 2, the team will evaluate non-GPS sensors to augment the Spiral 1 system, and support probe-and-drogue refueling.

The goal is to successfully refuel an F-16, acting as an unmanned surrogate, by 2011. The Navy’s UCAS-D program, which uses Northrop Grumman’s developmental X-47B unmanned attack aircraft, is also involved.

Contracts and Key Events

Boeing AAR concept
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Jan 12/09: Jane’s confirms that the X-47 UCAS-D program will begin aerial refueling tests performed in 2010, using surrogate aircraft.

Nov 19/08: Boeing in St Louis, MO received a $49 million cost plus fixed fee contract as the automated aerial refueling Phase II integrator. At this point, $1.2 million has been obligated. The Air Force Research Laboratory at Wright-Patterson AFB, OH manages this contract (FA8650-09-C-3902).

Boeing will lead the team, and is partnered is partnered with Northrop Grumman and Lockheed Martin as prime contractors. Other contractors include Northrop Grumman Electronic Systems, GE Aviation, Rockwell Collins, and the Sierra Nevada Corp. Under Phase II of the Automated Aerial Refueling (AAR) program, the industry team will coordinate flight tests that will include autonomous multiship operations, and the actual delivery of fuel to a manned surrogate UAV.

Phase II Spiral 1 involves designing and testing a multichannel precision-GPS relative navigation system, an automated flight control system, and the required command and control additions to guide the unmanned receiver to the manned tanker. Tests will use the air force’s boom system.

Under a planned Spiral 2, the team will evaluate non-GPS sensors to augment the Spiral 1 system, and support probe-and-drogue refueling. Boeing release | Aviation Week