Automated aerial refueling

An Air Force Research Laboratory program was started in 2004 at the AFRL Air Vehicles Directorate. The initial program was the evaluation of technologies that could be used for AAR. The key new concept is the use of precision GPS. The AAR program has since held several flight tests. The important factors were the software and communication systems that kept the aircraft at the proper altitude and speed.{{citation needed|date=September 2015}}

In 2007, the Defense Advanced Research Projects Agency (DARPA), with the help of NASA, demonstrated automatic refuelling from a conventional tanker by a high-performance aircraft. A pilot was on board to supervise, so the demonstration was not entirely automated.{{Cite web |title=NASA TechPort - Project Data |url=https://techport.nasa.gov/view/14615 |access-date=2024-06-10 |website=techport.nasa.gov}} It served as the basis for DARPA's Autonomous High-Altitude Refueling (AHR) program which, in 2012, demonstrated the potential for fully autonomous aerial refueling of unmanned high-altitude long-endurance aircraft.{{Cite web |last=Rosenberg |first=Zach |date=October 9, 2012 |title=DARPA completes autonomous high-altitude refuelling tests |url=https://www.flightglobal.com/darpa-completes-autonomous-high-altitude-refuelling-tests/107352.article |access-date=June 10, 2024 |website=flightglobal.com}}{{Cite web |last=gguarino |date=2012-10-08 |title=DARPA’s AHR Program Moves Closer to Autonomous Aerial Refueling |url=https://www.aviationtoday.com/2012/10/08/darpas-ahr-program-moves-closer-to-autonomous-aerial-refueling/ |access-date=2024-06-10 |website=Avionics International |language=en}} The final test involved two modified Northrop Grumman RQ-4 Global Hawk aircraft flying in close formation less than 100 feet from a tanker, close enough for refueling to take place, at 44,800 feet altitude.{{cite web| url=http://www.darpa.mil/about-us/timeline/autonomous-highaltitude-refueling| title=Autonomous High-Altitude Refueling| work=DARPA| accessdate=September 5, 2015}}{{cite news| url=https://www.bbc.co.uk/news/technology-19871063| title=Unstaffed drone refuelling test 'successful'| work=BBC News| date=October 8, 2012| accessdate=September 5, 2015}}

Appropriate flight control systems (FCS) include sensors to detect the position of the tanker and its refueling drogue along with rules to control the client aircraft. Several different techniques have been proposed for controlling the refueling process. One proposal involves the use of LED beacons on the drogue and an optical sensor on the tanker to determine the drogue's position and attitude. A second involves treating the drogue's position as fixed, ignoring turbulence with the help of a low-pass filter in the control system.{{cite book|title=Effect of Mass Variation on the Dynamics of Receiver Aircraft During Aerial Refueling|url=https://books.google.com/books?id=b-VBKGJPf3YC&pg=PA10|year=2008|publisher=ProQuest|isbn=978-0-549-67175-6|pages=10–13}}

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Category:United States Air Force