NASA'S AUTONOMOUS FORMATION FLIGHT: FOLLOW THE LEADER AND SAVE FUEL
October 29, 2001
Release: 01-61 Printer Friendly Version
(The airflow from the wingtips of an aircraft can provide energy, and thereby more efficient flight, to another aircraft flying in an optimum position behind the leader. Engineers and research pilots at NASA's Dryden Flight Research Center are exploring wingtip vortex energy with a pair of F/A-18 jet fighters flying over California's Mojave Desert. Central to the NASA Autonomous Formation Flight [AFF] program is a system of software and hardware still under development that will enable precise formations to be held without pilot inputs.)
A graceful vee of geese flying overhead is far more than an expression of natural aesthetics; the follower geese each derive energy from the flowfield generated by the next goose ahead in stepped formation. The result for the individual birds is a lower induced drag allowing a reduction in the energy required to maintain a given speed. The formation can fly farther before resting or use less energy per bird, than can geese flying solo.
Dryden researchers, working with counterparts from NASA's Ames Research Center, Moffett Field, Calif., The Boeing Co., St. Louis, Mo., and Long Beach, Calif., and the University of California, Los Angeles (UCLA), are combining software, satellites, and synergy to make a go of AFF.
The goal of the AFF project is to demonstrate a sustained 10 percent fuel savings by the trailing aircraft during cruise flight. Recent flight data suggests savings as high as 15 percent are achievable. Boeing and UCLA have developed a Formation Flight Instrumentation System that takes advantage of Global Positioning System (GPS) satellites plus onboard movement measurements to establish the relative position between the two aircraft to an accuracy better than 12 inches. A Boeing and NASA Dryden collaboration resulted in a Formation Flight Control System fitted to both F/A-18s.
And, to keep the research aircraft from getting too cozy, a Dryden-developed Independent Separation Measurement System can disengage the automatic flight control system should the F/A-18s come too close together.
That's the plan; the outgrowths are tantalizing. If AFF can make close formation flights routine, the air traffic system capacity could be increased. The goal of 10 percent fuel savings by follower aircraft also means an attendant reduction in carbon dioxide and nitrous oxide compound emissions into the atmosphere. And, as aircraft computer systems get ever smarter, one way a follower aircraft might maintain optimum formation position is by letting the flight computers monitor fuel flow, repositioning the follower as needed to keep flow at a minimum.
Once the concept is proven with the pair of F/A-18s, dissimilar aircraft could be surveyed to determine their "sweet spot," enabling formations of virtually any varieties of aircraft to enjoy the efficiencies of AFF. The formation technology might also be used to assemble a satellite in orbit by placing small, economical payloads in orbit and having them pace each other close enough to function as a whole.
The AFF jets flew formation over the California desert for the first time this February. They verified an initial ability to hold position within five feet, beating a goal set for this stage of the program. Gerard Schkolnik, AFF program manager, said the early flights met all project objectives. They are flying again, conducting risk-reduction research that will enable further refinement of the technique. Smokewinders - wingtip smoke generators - are enabling the NASA testers to visualize vortex activity as the jets hold formation.
Autonomous Formation Flight is another example of modern technologies working in synergy to enable aircraft to more closely resemble the master fliers, birds. There's a long-standing public fascination with NASA spin-offs, those serendipitous and seemingly coincidental outgrowths of NASA research. But AFF shows another side to that story - its fascinating outgrowths will be the intentional result of careful planning and research.
--nasa-- Note to Editors: (For Beta footage and photos of the Autonomous Formation Flight F/A-18s, please call (661) 276-7960.)
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