W
hen the 757 first flew more than 33
years ago, no one at Boeing could have
guessed that in 2015 one of these ven-erable twinjets would be helping pioneer 21st-
century “green” technology for future airliners.
Guy Norris Seattle
Technology
Spiral
Boeing maintains test tempo as 757
becomes latest ecoDemonstrator
CIVIL AIRCRAFT ADVANCES44 AVIATION WEEK & SPACE TECHNOLOGY/MARCH 30-APRIL 12, 2015 AviationWeek.com/awst
Yet on March 17, a heavily modifi ed 757 became the com-
pany’s newest ecoDemonstrator technology testbed to fl y,
and the third in the series since the environmental perfor-
mance initiative was fi rst unveiled in 2010. Confi gured with
an actively blown vertical tail and new wing leading-edge
sections, the 757 will gather data in tests beginning in April
that could dramatically infl uence the use of natural laminar
and active fl ow control technology in future airliner designs.
Held in collaboration with NASA and the TUI Group, eval-
uations will focus on two methods of protecting wing leading
edges from the laminar fl ow-destroying ef ect of residue left
by insect strikes, as well as the performance of the active fl ow
control (AFC) tail. Part of the leading edge slat on the right
wing will be treated with several experimental “bug-phobic”
coatings designed to keep the surface free of contaminants,
while the left wing is modifi ed with a glove section supporting
a variable-camber Krueger fl ap that covers the leading edge
at altitudes where insects would be encountered.
The tail tests, which also form part of NASA’s Environ-
mentally Responsible Aviation (ERA) program (page 47), will
evaluate the ability of active fl ow jets mounted on one side of
the tail to increase rudder ef ectiveness. As vertical tails are
sized to cope with the asymmetric forces resulting from loss
of an engine on take of , Boeing and NASA believe that increas-
ing rudder ef ectiveness 20% will lead to substantial reduc-
tions of up to 17% in tail size, with resulting cuts in weight
and drag. “Even if you can reduce the tail size by 10-15% that’s
still a signifi cant benefi t,” says 757 ecoDemonstrator program
manager Douglas Christensen.
The AFC, mounted on the right side of the fi n only for the
tests, comprises 31 passive sweep jet actuators positioned
ahead of the rudder leading edge. Supplied by pressurized air
from the auxiliary power unit that has been pre-cooled in an
externally mounted heat exchanger beneath the aft fuselage,
the actuators emit a jet that sweeps back and forth across an
arc. The action re-energizes the separated fl ow, re-attaching
it to the defl ected rudder. Test fl ights are expected to run
through July and, following completion, the 757 will make the
ultimate sacrifi ce for environmental research and be broken
up using special recycling methods under an agreement with
the Aircraft Fleet Recycling Association.
Although tests involving the 757 are just beginning, Boeing
is already planning a series of follow-on ecoDemonstrators
for 2016- 18 and beyond, as it seeks to build on the momentum
gained from the fi rst two aircraft. The series began in 2012
with 15 technologies tested on a 737-800 leased from Ameri-
can Airlines, and continued in 2014 with more than 25 new
technologies demonstrated on ZA004, one of Boeing’s early
developmental 787-8s.
“The ecoDemonstrators are about ‘what’ we do and ‘how’
we do it,” says Mike Sinnett, Boeing’s vice president of Prod-
uct Development. “A lot of the airplane is about the ‘what’
we do, and how we use it to spiral technologies on to either
existing or next-generation products. But also, and almost as
importantly, it’s about ‘how’ we do it, how we innovate and
how we have improved the process of innovation. It’s not just
about being cost ef ective, it’s how you approach things and
try to do more for less. We try to focus on practical things
that might get on an airplane as opposed to science projects
that won’t get on airplanes.”
With Boeing’s broader product development portfolio es-
sentially locked in for at least the next decade, the timing of
the ecoDemonstrator initiative is propitious. Designed to ac-
celerate the testing, refi nement and use of new technologies
and methods that can boost ef ciency and reduce noise, the
program is aimed at incremental short-, mid- and long-term
improvements rather than radical leaps. “There is a place for
X-planes and a place for moonshots clearly, but what we are
focused on now is neither of those. It is really the practical
application of spiraling technology in a less-risky way,” he says.Pictured near the 757 ecoDemonstrator, 787 ZA004 completed its
research role in December after 33 fl ights and 94 fl ight hours.
BOEING