a significant experimental modification. The aircraft is now
expected to fly in 2016, but all testing under CS1 is planned
to finish in 2016 to allow a year of report writing before the
program must end in 2017. “Blade is right up against the edge.
We believe it will still be inside Clean Sky 1,” he says.
Airbus recently reviewed the project, and concluded dem-
onstrating robust laminarity in flight remains essential. “We
asked what is the value of it, would we launch a natural laminar
flow aircraft without a demonstrator? The answer is no, we
need to demonstrate we can manage the tolerances. It is an
enormous challenge,” says Axel Flaig, Airbus senior vice presi-
dent for research and technology. “The same goes for open
rotors. No chief engineer is going to decide to put them on an
aircraft without a demonstration. This justifies the route taken
with Clean Sky 2, to demonstrate the technologies developed
in Clean Sky 1 and open the path to application,” he says.
Budgeted at €560 million, Platform 1 within LPA will take both
laminar flow and open rotor to the next level of integration. The
program will look at next-generation configurations with much
more extensive natural, hybrid and active laminarity. Plans in-
clude a long-term flight demonstration of HLFC on the fin and
a preflight demo on the wing. “We need
to go to large scale on hybrid laminar-
ity and will look at the tail surfaces
first, using the Blade manufacturing
tolerances,” van Manen says.
Under CS1, Snecma plans to
ground test a geared counter-rotating
open-rotor demo engine by the end of
this year. Under CS2, a flight engine
will be mounted on the aft fuselage of
an A340-300 to assess noise, vibration
and operation. Under LPA, industry
will also build a full-size composite
rear fuselage to demonstrate the safe
installation and integration of 15-ft.-
dia. open rotors on a future 757-class “middle of the market”
airliner. “What are the certification requirements if you have
very large, very high energy unducted rotating parts? That’s
where the ground demo comes in,” says van Manen.
Illustrating the balance to be struck under CS2, Platform
1 will also include lower-TRL research into radical configura-
tions required to enable use of ultra-high-bypass turbofan,
large-diameter open rotor or hybrid turbine/electric propul-
sion concepts. Airbus plans to fly a dynamically scaled model
of a hybrid propulsion configuration with multiple electrically
driven fans.
“With very large integrated engines, where do you put
them?” asks van Manen. “When you look at very-large-di-
ameter ultra-high-bypass or distributed propulsion, one of
the things that comes out is much more radical configura-
tions. Using a dynamically scaled test vehicle, like NASA’s
X-48B, will contain cost and ensure safety. It’s modest risk,
but high reward.”
While further upgrades like the A320neo reengining are
likely, “in time there will be technologies that cannot be inte-
grated on existing aircraft,” says Flaig. “The challenge with
new configurations is we have not found one that gave us
a real advantage. With hybrid propulsion there might be a
completely new configuration that does, by 2035 or later,” he
says.“Clean Sky 2 is an exciting blend of nearer-to-implemen-
tation high-TRL technology and research aiming for maturity
by 2035,” says van Manen. “We are not focusing only on the
immediate next generation, but pushing for the next game
changer. We need to create the headroom in the program to
look further out and be more audacious.”
Platform 2 of LPA will tackle an area Flaig thinks has been
neglected. “We have not focused enough on integration of the
fuselage and cabin. Instead there is a lot of complexity, outer
and inner shells that are completely disconnected,” he says.
“Clean Sky 2 will integrate the fuselage and cabin to save
weight, and also develop new ideas for how the cabin should
look, such as projection of the outside view.”
The program will look at multifunction materials and
structures and better cabin layout and functionality. “We will
take elements that are non-load-bearing now and use them to
bear loads. We will embed wiring and systems within struc-
tures,” says van Manen. Component, subassembly and full-
barrel demos are planned. “The focus is the fuselage. It’s the
last beneficiary of integration,” he says. Some technologies
could have near-term application. “I would not be surprised
if there is potential for a NEO or retrofit approach. The next
completely new aircraft is 10 years further out than where
we were five years ago, so we need ideas we can retrofit,” says
van Manen. Flaig agrees: “While we
focus on demonstrations to mature
breakthrough technologies we can-
not stand still, and must continue to
improve our existing aircraft.”Platform 3 of LPA, looking at the
next-generation flight deck, has
two strands: “an evolutionary solu-
tion that might go into a production
refresh, and a breakthrough that would enter the market
through an all-new design 10-15 years out, where we rethink
the man/machine interface and how we train the pilot,” says
van Manen. “We think we have a good handle on the evolu-
tionary cockpit.” Far-term research will “start with a clean
sheet and it will take 2-3 years to elaborate the agenda for a
breakthrough cockpit.”
Under the Engines ITD within CS2, Snecma will demon-
strate an “ultra-high propulsive efciency” geared turbofan
for an A320/737-replacement short/medium-range airliner. At
some point within the CS2 program, the company will decide
between open rotor and the geared turbofan, says Eric Bach-
elet, executive vice president for research and technology.
Rolls-Royce will demonstrate ultra-high-bypass geared
turbofan technology for long-range airliners and the middle
of the market. “We will continue with open rotor, but it is
a trade between fuel efciency and impact on the airport
environment,” says van Manen. “Snecma, Rolls-Royce and
MTU have diferent architectures, but they are aiming at
the same thing: increasing bypass ratio.”
“Clean Sky 2 is an extension of Clean Sky 1 in which we
will fully complete the journey to the 2020 goals, which we
will achieve a little later than 2020, and make the first steps
to the 2050 goals,” he says. “Without Clean Sky, technology
integration at a higher level would not have happened. Clean
Sky 2 brings incredible opportunity, but also responsibility
for the Joint Undertaking to push the long-term agenda.” cCIVIL AIRCRAFT ADVANCES52 AVIATION WEEK & SPACE TECHNOLOGY/MARCH 30-APRIL 12, 2015 AviationWeek.com/awst
Clean Sky programs, including this
composite-fan flight test, form
a key part of Rolls-Royce’s tech
plans for future engines.ROLLS-ROYCE