Autonomous Aerial Refueling Highlights Command-Control of Unmanned Aircraft

The Naval Air Systems Command ( Patuxent River, MD) announced that an X-47B aircraft successfully conducted the first ever Autonomous Aerial Refueling (AAR) of an unmanned aircraft April 22, completing the final test objective under the Navy's Unmanned Combat Air System demonstration program.

An X-47B (see figure), built by Northrop Grumman, was used for this test. The X-47B is an unmanned autonomous aerial vehicle that flies missions according to pre-programmed instructions rather than being controlled by a ground-based pilot. The aircraft was designed to demonstrate autonomous carrier operations including launch, recoveryand operations within 50 nautical miles (57.5 mi, 92.6 km) of a carrier. Only one of the two demonstrators built is designed for autonomous aerial refueling operations using the Air Force “boom/receptacle” approach as well as the Navy probe and drogue method. No weapons were carried by either aircraft and no sensor tests were conducted.

With its stealthy design, aerial refueling capability and large internal payload, the X-47B is more representative of the Navy’s earlier naval unmanned aerial combat system (N-UCAS) deep strike aircraft. Since then, the service has modified its goals to create the Unmanned Carrier Launched Surveillance and Strike (UCLASS) program. The initial UCLASS goals were to provide an off-cycle surveillance capability for a carrier strike group and provide limited strike capabilities in uncontested airspace that didn’t need an aerial refueling capability.

In the first test of its kind, the X-47B flew off the coast of Maryland and Virginia in the Atlantic Test Ranges. It connected to an Omega K-707 tanker aircraft and received over 4,000 pounds of fuel using the Navy's probe-and-drogue method.

“What we accomplished today demonstrates a significant, groundbreaking step forward for the Navy," said Capt. Beau Duarte, the Navy’s Unmanned Carrier Aviation program manager. “The ability to autonomously transfer and receive fuel in flight will increase the range and flexibility of future unmanned aircraft platforms, ultimately extending carrier power projection."

During the test, the X-47B exchanged refueling messages with a government-designed Refueling Interface System (RIS) aboard the tanker. The aircraft autonomously maneuvered its fixed refueling probe into the tanker’s drogue, also known as the basket, the same way a Navy pilot would refuel a manned aircraft.

“In manned platforms, aerial refueling is a challenging maneuver because of the precision required by the pilot to engage the basket,” Duarte said. “Adding an autonomous functionality creates another layer of complexity." This testing helps solidify the concept that future unmanned aircraft can perform standard missions like aerial refueling and operate seamlessly with manned aircraft as part of the Carrier Air Wing, he said.

“This segment of the X-47B demonstration program allowed us to further mature AAR technologies and evaluate the government tanker RIS,” said Barbara Weathers, X-47B deputy program manager. “We used similar command-control and navigation processes previously demonstrated during the X-47B landings aboard the aircraft carrier."

Over the last few years, the Navy accomplished several significant firsts with the X-47B that showcased the Navy’s commitment to unmanned carrier aviation. With the completion of this program, the service continues to develop its future unmanned carrier-based platform, known as UCLASS.