by Roger Drinnon
Air Mobility Command Public Affairs
10/10/2012 - SCOTT AIR FORCE BASE, Ill. -- Migrating
birds, NASCAR drivers and Tour de France bicyclists already get it. And
now the Air Force is thinking about flying gas-guzzling cargo aircraft
in formation--'dragging' off one another--on long-haul flights across
Flight tests with C-17s "vortex surfing" at Edwards Air Force Base,
Calif., Sept. 6 and Oct. 2, have demonstrated potentially large savings
of fuel and money by doing what geese do naturally. Tests show that
flying in formation might be smarter than flying alone for Airmen, and
not just for birds.
As one effort in the Air Force drive to reduce its overall fuel consumption, vortex surfing may be the wave of the future.
"The concept, formally known as Surfing Aircraft Vortices for Energy, or
$AVE, involves two or more aircraft flying together for a reduced drag
effect like what you see with a flock of geese," said Dr. Donald
Erbschloe, Air Mobility Command chief scientist.
A series of test flights involving two aircraft at a time, allowed the
trailing aircraft to "surf" the vortex of the lead aircraft, positioning
itself in the updraft to get additional lift without burning extra
Early indications from the tests promise a reduction of fuel consumption
by up to ten percent for the duration of a flight. Over long distances
and with even a small fraction of Air Mobility Command's average of more
than 80,000 flights a year, the fuel and cost savings could reach into
the millions of dollars, experts say.
Next up: The Air Force Research Laboratory will analyze the data from
for possible applications to other aircraft on a variety of missions.
Dr. Erbschloe said larger air mobility aircraft like the C-17 can fly in
formations that are potentially easy to maintain and which do not
require the planes to be exceptionally close together.
"The test flights were flown at longitudinal separations of 4,000 or
greater," said William Blake, one of the key developers of $AVE at the
According to AFRL officials, modified C-17 Formation Flight System
software enabled precise auto-pilot and auto-throttle systems to ensure
the trailing aircraft achieved and maintained proper flight position
without active assistance from pilots.
"The autopilot held the position extremely well - even close to the
vortex," said Capt. Zachary Schaffer, aircraft commander on one of the
test flights. "The flight conditions were very safe; this was as
hands-off as any current formation flying we do."
Other pilots found differing levels of ride quality and discovered some
flight test points might be difficult for long-endurance flights.
"The key will be finding the right balance of quality for improving fuel
efficiency and ride," said Maj. Eric Bippert, another aircraft
commander on one of the test flights.
Bippert said being a part of the test program with so many talented
engineers was a remarkable experience, and the concept could eventually
impact global air transportation, overall.
"AMC has done really well with fuel efficiency at the operational level.
The command has worked to gain efficiencies from the 'low-hanging
fruit' such as optimizing flight routing, reducing weight where
possible, and by not carrying excess fuel," said Erbschloe. "$AVE offers
significant efficiency gains, if employed in concert with these
He said early indications show the tests meet AMC criteria of the
concept regarding safety and minimization of aircrew and aircraft strain
while also being operationally sensible with a viable return on
"AMC consumes 20 percent of the fuel used by the overall Federal
government, so we're constantly looking for pragmatic ways to improve
our fuel efficiency," said Erbschloe.
"Assured energy advantage for our Air Force is only possible through
revolutionary energy initiatives like $AVE," said Dr. Mark Maybury, Air
Force chief scientist, upon hearing the results of the tests.
The $AVE concept was previously highlighted in the 2011 "Energy
Horizons" study, sponsored by the Secretary of the Air Force and chaired
The tests were the culmination of an ongoing, combined effort between
AMC; the AFRL; the 412th Test Wing; the Air Force Life Cycle Management
Center; the Defense Advanced Research Projects Agency; the Boeing
Company; and NASA Dryden Flight Research Center.
Editor's Note: Holly Jordan, Air Force Research Laboratory, contributed to this report.