by Roger Drinnon
Air Mobility Command Public Affairs
8/15/2013 - SCOTT AIR FORCE BASE, Ill. -- AMC's
chief scientist credited birds, dolphins and surfers for the success of
recent ground-breaking C-17 flight tests expected to save the Air Force
millions in annual fuel costs.
Dr. Donald Erbschloe flew aboard the test flights involving surfing
aircraft vortices for energy - or "$AVE" - from Edwards Air Force Base,
Calif., to Joint Base Pearl Harbor-Hickam, Hawaii, and back, July 9-11.
Afterward, he explained how nature provided inspiration for one C-17
aircraft to trail behind another and recapture energy that would
otherwise be lost. This allows the trailing aircraft to use less fuel in
a time when aviation fuel costs are soaring. Data from the tests
promise savings of up to $10 million a year.
"Creatures in the wild do this all the time - exploiting conditions
which give them an energetic advantage - just that slight edge," said
Erbschloe. "Dolphins and human surfers ride the 'bow waves' off ships,
hawks circle in thermals to gain altitude and energy, and geese fly in
V-shaped formations to reduce their exertion during long migrations."
He said during a recent ferry ride in Washington State, he mused at how seagulls employed the method.
"I observed seagulls riding the air bow wave off the top of a ferry"
said Erbschloe. "Just as we were starting our crossing, a seagull
positioned itself and established a sustained glide - it never flapped
its wings once during the entire 20-minute transit. Only when the ship
slowed and maneuvered to dock did the bird start to fly on its own."
AMC aircrews and 412th Test Wing personnel, along with Boeing
researchers, were on the two C-17 aircraft in the $AVE configuration.
The July flights followed previous test flights at Edwards in October,
which proved the science behind the concept. Results from those tests
were compelling enough to warrant the follow-on tests on an actual
operational mission, which also included flying at night.
"We were very pleased with the results of the long range demo. We
demonstrated in-flight rendezvous, day and night operations, and flew
several hours in each direction in our $AVE formation," said Bill Blake,
the Air Force Research Laboratory $AVE Program Manager. "With only
minor changes, we were able to attain double-digit fuel savings, which
exceeded what we measured during our 2012 proof-of-concept test."
Erbschloe said other tests in years past involved fighter aircraft,
which had to fly closely at "fingertip" intervals for any benefit,
requiring a lot of pilot effort for what he described as "white-knuckle"
flying. Not the case with the larger C-17. With minor software changes,
the C-17's autopilot sustains the $AVE position at safe distances
ranging from 3,000-6,000 feet between the lead and trailing aircraft, so
the aircrew workload is minimal. He said in addition to confirming the
fuel savings, assessing how $AVE affected the aircrew was an important
part of these latest tests.
"Maintaining position in the $AVE formation is no more task- saturating
for the aircrew than flying at cruise on any other worldwide mission,"
said Maj. Kyle Clinton, director of 62nd Airlift Wing weapons and
tactics from Joint Base Lewis-McChord and one of the pilots who flew the
trailing C-17 during the tests. "Across the board, I believe the
potential benefits could be worthwhile for the aviation community - not
just for C-17 formations but also for mixed formations, such as tankers
The tests are done, and the concept is validated. The next step involves
funding for a DoD Advanced Technology Demonstrator to figure out the
exact procedures and processes needed to introduce this fuel-saving
concept to other Air Force aircraft. The two- to three-year project
could begin as early as next year, Erbschloe said.
$AVE is the culmination of an ongoing, combined effort between AMC, the
AFRL, the 412th TW, the Air Force Life Cycle Management Center, the
Defense Advanced Research Projects Agency, the Boeing Company, and NASA
Dryden Flight Research Center.