FLYING IN FLOCK FORMATION, AIRCRAFT SAVE FUEL IN TESTS.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - Borrowing an idea from nature, a recently completed set of flight tests at NASA's Dryden Flight Research Center showed a substantial fuel savings for aircraft flying in formation like birds.

A National Aeronautics and Space Administration F/A-18 jet experienced a 29 percent fuel savings June 27 when it flew in the vortex of a DC-8 research aircraft. The aircraft flew at 25,000 feet with the F/A-18's nose 200 feet beyond the larger jet.

Tests conducted in 2001 with two F/A-18s flying in formation showed a fuel savings of 18 percent, NASA said.

Just as migrating geese and other birds fly in a V-formation to save energy, Dryden researchers tested the effect of flying one jet in the vortex, or up-wash of air, coming off the wingtip of a plane in front of it.

``By doing formation flying, like birds have done for centuries, you can save fuel,'' said NASA Dryden spokesman Alan Brown. ``The larger the vortex, the better the fuel economy.''

While the fuel saving was greater when the F/A-18 flew in formation with the DC-8 than with another F/A-18, it was still not as great as researchers had anticipated.

``We were hoping for a larger number, based on some predictions that the DC-8 vortex would be bigger, and thus more of the trailing aircraft would be in the upwash,'' said Brent Cobleigh, chief engineer for the program. ``We are not sure whether the smaller vortex that the pilot reported is generally the case for transport aircraft, or perhaps the DC-8 has a particularly small vortex.''

While migrating birds of the same species fly in formation, the pairing of large and small jets does not have a counterpart in nature.

``Many bird species have figured out that formation flight benefits them, but nowhere do you see examples of large and small birds cooperating in a formation,'' Cobleigh said.

The research could be of benefit to both commercial and military aviation. Cargo transport aircraft could save fuel by flying in formation, as could unmanned combat aircraft.

There are no plans for follow-up testing, but it is possible that the Air Force, other government agency or a defense contractor might want one or two flight tests, NASA officials said.

Information from the flight tests will be the subject of a technical report, NASA said.

Jim Skeen, [phone]

james.skeen(at)dailynews.com