Morphing Winglet: Clean Sky
innovation waiting in the wings
Clean Sky's Morphing Winglet project not
only promises operational performance
improvements and emissions reductions, it's
also aiming to reduce manufacturing costs
and production lead times.
W
inglets have become an increasingly
ubiquitous feature of civil airliners over
the past couple of decades due to their
aerodynamic benefits, such as reducing the
wingtip vortices, which lead to energy loss.
Winglets also reduce drag, help boost aircraft
performance and cut fuel consumption.
Clean Sky’s Morphing Winglet project aims to
enhance the aero-efficiency of more durable,
affordable and lighter-weight wing structures
through the design, build and ground testing
of winglet structures with innovative curved
contours made from lightweight composite
materials that have inte grate d micro
electromechanical actuators (EMA).
In terms of defined aerodynamic and
environmental targets, the project aims to
reduce weight at component level by around
15% relative to current state-of-the-art winglets,
leading to drag reduction at aircraft level of
Winglet Digital Mock-Up view
around 5% and an expected 10% improvement
in load alleviation. The cumulative anticipated
benefit of these targets is intended to
precipitate a corresponding reduction in
fuel consumption that will be confirmed in
forthcoming flight tests.
Another key target of the project is to also
reduce the manufacturing costs of the winglets,
helping curb impact on the environment in line
with the goals of the European Green Deal. The
manufacturing approach to achieve this is to
employ a low-cost jigless one-shot composite
material process. The ultimate objective is to
reach TRL6 in respect of all the technologies
integrated into the morphing winglet concept,
which will be installed and flown in the Regional
IADP Flight Test Bed Demonstrator, a C295based aircraft, with a first flight test scheduled
for 2021. A further flight demonstration regime
is slated for 2023.
‘We wanted to incorporate a micro electromechanical actuator (EMA) in the winglet
tab with independent actuation, in order to
have benefits in terms of drag, especially in
terms of aerodynamic optimisation, in respect
of aerodynamic efficiency, in terms of lift, in
terms of performance, and additionally as
well to address load alleviation,’ says Antonio
Hernández, airframe ITD coordinator and
Airbus DS Clean Sky 2 manager at Airbus.
‘With this new winglet we are able to reduce the
bending moment of the aerodynamic forces of
the wing because we can deflect at a negative
angle the tab of the winglet — we can move
the centre of the pressure of lift to the inner part
of the wing, converging to the wing root. This
brings benefits in terms of load alleviation and
can help us to reduce the weight of the structure
of the wing, because the loads we need to apply
for the design of the structure are less.’
Castillo, VP Technology Development, at the
Sp ain - h ea d quar tere d a eros t r u c t ure s
company Aernnova.
Aernnova's main activities include the
w in gl et d esign, f ro m ear l y co n cept s
formed together with Airbus to detailed
design, drawings, and reports, as well as
the development of new design principles
associated with the new manufacturing
processes, validated by tests.
Winglet mounted on the aircraft wing tip
The second stream of the project is that the
winglet is designed in a highly integrated
way so that fasteners and bondings are
replaced by producing the winglet in a
simplified and unified manner.
‘We are trying to progress towards a jigless
process to manufacture the winglet in one
shot, by integrating the different elements
of the winglets and therefore reducing the
number of part numbers and to eliminate as
many of the joints as we can,’ says Hernández.
‘In conventional manufacturing, you have to
combine the different elements — ribs,
spars, skins — which are all connected with
fasteners, rivets and screws. This creates a lot
of weight in the structure, and what we want
to do instead is to avoid that, so we wanted
to manufacture for example the torsion box
of the winglet in one shot.’
The process of manufacturing is focused
around low cost tooling. Traditionally,
tooling is made from hard-wearing metals
that are expensive and slow to produce,
but are required in order to ensure the
correct tolerances in the geometr y of
the comp onent s. Instead, Hernández
explains, the team decided ‘to use tooling
manufactured from composite materials,
and using a liquid resin infusion process
which allows us to be more flexible in terms
of geometry and reduce the non-recurring
tooling costs, and therefore reduce the
overall costs of manufacturing.’
This process also reduces the lead time.
However, one of the challenges of soft
tooling is faster degradation of the tool,
which means that the number of cycles for
making the winglet is less. Hernández says
that this ‘is another challenge we need to
face, but we are working on it.’
The target that the project has set itself is to
reduce manufacturing costs and lead times
by 5%, relative to current manufacturing
methods, minimising the environmental
impact during the manufacturing cycles.
The project's core partner, Aernnova, has
developed the morphing winglet composite
structure, with Airbus having provided the
external loft, the loads and the high level
technical requirements.
‘Ae r n n o v a h a s b e e n e n g i n e e r i n g a n
innovative composite solution, including
new design concepts and manufacturing
processes that reduce the structural weight
while enhancing competitiveness through
technology innovation,’ says Dr. Miguel Ángel
‘ There have been testing ac tivities in
close collab oration with the Spanish
Foundation for the research development
and application of composite materials
(FIDAMC) for materials coupon testing and
manufacturing trials for the new curved
spars concepts,’ adds Dr. Castillo. Indeed,
collaboration has been key throughout
many aspects of the project, including, he
notes: ‘the co-development with Airbus
of the interfaces with the rest of the wing,
the actuators and systems, and the winglet
Digital Mock Up (DMU) development with
very strong collaboration with the Airbus
team including configuration control.’
Aernnova, with support from the other
partners, has also been responsible for the
development and manufacturing of the
composite manufacturing tools for the
inboard and outboard leading edges, the
torsion boxes, and the tab; the assembly
tools for the winglets and tabs, left and right;
as well as the production of elementary
parts prototypes, assembly of the winglets,
quality assurance of the demonstrators and
inspections prior to delivery to the Airbus
assembly line for integration onto the Flight
Test Bed Platform.
As for timelines and progress thus far, the
Preliminary Design Review took place in
2017 with the first Critical Design Review
in 2018. ‘We started the manufacturing for
the elementary parts and the tooling in
mid-2018, and ground tests were performed
during the second semester of 2019. For
2020 the challenge is to produce all the
technical documentation for the winglet to
obtain a permit to fly for the winglet and
also for the full flight demonstrator,’ says
Airbus's Hernández.
In terms of deliverables, at the end of 2019
Aernnova provided Airbus with left and
right airwor thy morphing winglets for
experimental flight testing.
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Winglet assembly part
‘The new production concepts can provide
more competitive products in their life
cycle,’ says Aernnova's Dr. Castillo. ‘The most
relevant achievements include reduction of
the winglet structure, due to the fact that the
actuators, fittings and hardware for morphing
are integrated within the structure, yet they
have the same overall weight as the current
metallic benchmarked winglets. The tests that
validate the design have been completed,
from coupon test level to the design detail and
component testing performed in Aernnova for
lightning strike test, curved spar strength and
subcomponent load paths tests.’
Aernnova has also completed the manu­fac­turing
trials for curved spars to validate the new press
forming process and the asymmetric stacking
sequences, as well as the validation through
testing of the new Tab RTM manufacturing
process feasibility that includes copper
mesh integration.
‘The manufacturing processes reduce the
amount of fasteners required for assembly.
This means recurring cost reduction during
production and operation,’ says Dr. Castillo,
whose company also, for this project, created
‘new manufacturing processes and design
principles for the Torsion Box Elbow enabled by
curved spars, highly integrated multi-spar torsion
boxes, morphing winglet leading edge and tab,
removable panels and hinge line fittings.’
Winglet assembly part
‘One of the things we need to do is to measure
what we have achieved with all these different
elements that have been manufactured in
terms of weight, in terms of drag reduction,
in terms of loads alleviation, and performance
enhancement. We have some targets and we
have performed a wind tunnel test for the full
mock-up, but we won't know the full results
until the flight testing, in 2021 and in 2023, is
complete,’ says Hernández.
As for the broader value of the Morphing
Winglet project, Hernández says: ‘Clean Sky
2 allows us to establish collaborations with
other organisations, other actors, universities,
and other companies at industrial level. All the
research and academia allows newcomers
to enter the arena with new ideas that can
contribute a lot to increased performance
and competitiveness of the European aircraft
industry. This collaborative research and this
concept of approach enables us to see what's
going on in new technologies in critical areas
of the aircraft and what's going on in different
organisations, and then work together to
promote the aircraft as a product, address
societal needs, and promote the aircraft
industry at European level.’
In terms of industrial achievement for European
aircraft manufacturing he adds: ‘this project
helps ensure that we have enough maturity
to enable highly integrated structures to be
manufactured in one shot using composite
materials, reducing the cost of manufacturing
processes as well as the lead time. This way of
integrating functionality and using composite
materials allows us to significantly reduce
the weight of the winglet. Additionally, the
winglet’s morphing capability allows us to
improve aerodynamic efficiency at aircraft
level, reducing drag and increasing the
performance of the aircraft with a positive
impact on the fuel burn rate.’
Commenting on these benefits, Aernnova's
Dr. Castillo refers to the fact that the EU's
strategy of going climate-neutral by 2050
‘is a challenge that requires extra research
and technology efforts and collaboration
of the European aeronautics value chain.
Clean Sky is very important for this purpose.
The opportunity to integrate and mature
technologies, all the way from low TRL
studies to ground and flight demonstrators,
is a high added value for all the partners.
Clean Sky is part of a coherent roadmap of
technological and operational solutions
needed to achieve this long term EU
strategy. Clean Sky provides a long term
basis that can balance the required flexibility
with the timely delivery of key enabling
demonstrators. Fur thermore, dif ferent
aircraft platforms require different solutions
and this is enabled by the Clean Sky formula
and by collaboration across the value chain.’
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Copyright 2020 – Clean Sky 2 JU – Belgium White Atrium, 4th floor, Av. de la Toison d’Or, 56-60 – 1060 Brussels