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TPS students test autonomous aerial refueling

EDWARDS AIR FORCE BASE, Calif. (AFMCNS) -- Students at the U.S. Air Force Test Pilot School demonstrated various autonomous aerial refueling maneuvers during a flight test program at Edwards during October.

A C‑12 represented the tanker and Calspan’s Variable Stability Lear‑25 represented the autonomous receiving aircraft. Both aircraft were equipped with carrier phase differential Global Position Systems designed as a master’s thesis by Capt. Chris Spinelli, a student in the joint Air Force Institute of Technology and TPS program.

The control system in the Learjet was also an AFIT and TPS thesis, designed by Capt. Steve Ross, in the same program.

“The tanker used a small Micro-Electrical Mechanical System Inertial measurement unit for bank angle and roll rate measurements,” said Captain Ross, the chief test pilot and project manager. “These measurements with the relative position to the tanker were data linked to the receiving aircraft. The control system then used these inputs to schedule the control surfaces and throttles automatically.”

An operator in the receiving aircraft selected either the contact, pre-contact or wing observation position. The receiving aircraft was able to hold any of the positions autonomously, meaning hands off the stick and throttle, as well as transitioning between formation positions autonomously. This was demonstrated throughout a standard race track course where the tanker banked as much as 30 degrees.

“The controller performed quite well,” he said. “By the last three test flights, the controller was turned on shortly after takeoff, and the pilots were hands free for nearly the entire two hour duration.”

For refueling in straight and level flight, the controller held the receiver on average within 1.3 feet of its desired position, well inside of the envelope of a refueling boom.

“As far as I know, this in-flight demonstration of autonomous aerial refueling maneuvers during a standard race track course has never been done before,” Captain Ross said. “This represents a major aviation milestone, and the entire program was done by military students, with assistance from Calspan, on a relatively small budget.”

He said autonomous aerial refueling is of great interest to the Department of Defense.

“Autonomous aerial refueling can increase J-UCAS deployment capability, remove transportation vehicle requirements, decrease dependence on in-theater land operations and greatly extend range and station time,” Captain Ross said.

This project was accomplished under the joint Air Force Institute of Technology and Test Pilot School program, where students do course work and preliminary research for 15 months at AFIT, then “fly their thesis” near the end of the 48-week TPS program. In addition to AFIT, Air Force Research Lab also assisted with funding for the effort.