Flight International - June 30, 2015 UK

COVER STORY

24 | Flight International | 30 June-6 July 2015 flightglobal.com

KERRY REALS loNDoN

Boeing’s latest ecoDemonstrator testbed is a retiring 757

on which it will research bug-phobic coatings and new

recycling methods in a bid to speed green applications

GoinG with

thE fLow

Tests are aimed at reducing tail size and weight

Boeing

B

oosting aerodynamic efficiency is
the cornerstone of Boeing’s latest
battery of ecoDemonstrator test
flights. The tests are being carried
out on a near-end-of-life 757 that will later be
used to test new aircraft-recycling techniques,
before being consigned to history.
The 757 is the third aircraft type to under-
go ecoDemonstrator test flights, following
earlier programmes involving a 737-800 in
2012 and a 787 in 2014. While the 737 flights
were carried out in conjunction with Ameri-
can Airlines, and the 787 flights were run
under the US Federal Aviation Administra-
tion’s continuous lower energy, emissions
and noise (CLEEN) programme, Boeing has
chosen a European airline partner – TUI
Travel – to work with on the 757 tests.
The overall aim of the ecoDemonstrator
programme, says Boeing Commercial Air-
planes director of environmental performance
Jeanne Yu, is to speed up the implementation
of fuel-saving technologies in aviation, and

“Shaving aircraft fuel

consumption by even a few

points can save millions”

fAY CoLLiER

Project manager, ERA

“inspire people to action” on developing

more environmentally-friendly aircraft.

Whereas the 737 ecoDemonstrator focused

strongly on adaptive wing and regenerative

fuel cell technologies, and the subsequent 787

programme concentrated on ceramic matrix

composite nozzle design, the latest round of

testing will look at ways of reducing environ-

mental effects on natural laminar flow. A key

piece of this research involves the application

of various insect-repelling, or “bug-phobic”,

coatings to the leading edge of the aircraft’s

left wing to try to reduce drag by minimising

the amount of insect residue.

dE-BuGGinG tEChnoLoGY

“Any bug you have on an airplane will affect

drag,” says Yu, adding that a total of five dif-

ferent “microscopically adhered” coatings

will be tested. The bug-phobic testing is being

carried out in conjunction with NASA’s envi-

ronmentally responsible aviation (ERA) pro-

ject. Sections of the various coatings will be

applied to the leading edge slats, after estab-

lishing a baseline by using uncoated surfaces

to capture insect-accumulation levels. Dura-

bility of the coatings will be examined to see

how they withstand flight conditions.

The coatings will be tested on 15 separate

flights, taking place throughout June and com-

ing to an end in July. These tests will be carried

out in Shreveport, Louisiana, a location chosen

because of its high insect levels. Shreveport

was selected from 90 candidate airports on ac-

count of its “runway length, temperature, hu-

midity, weather, ability to handle a 757 aircraft

and thunderstorm frequency”, says NASA.

Knowledge gained by NASA – with the excep-

tion of anything that uses Boeing’s proprietary

technology – will later be made publicly avail-

able to benefit the entire industry.

Another set of 757 ecoDemonstrator tests,

completed in April, focused on active flow con-

trol. These tests involved installing 31 actuators

to force jets of air on to the aircraft’s vertical tail

and rudder surfaces, the aim being to reduce

the size and weight of the tail that is needed by

generating the same side force during take-off

and landing that a larger tail provides.

The results of the nine test flights carried out

in Seattle are now being analysed. However,

NASA expects them to confirm the findings of

an earlier wind tunnel test, which showed that

the active flow control jets could increase side

force by 20-30%. “A 20% increase in side force

could allow designers to scale down the verti-

cal tail by about 17% and reduce fuel usage by

as much as 0.5%,” says NASA.

“Solutions to reduce fuel use by 1% or 2%

may not sound like much,” says Fay Collier,

Boeing chose European

TUI Travel as its partner

to work on 757 tests