19. November 2019
First flight for aeroelastic wings at Oberpfaffenhofen special-purpose airport

Su­per-ef­fi­cient wings take off

Departure from Oberpfaffenhofen special-purpose airport
De­par­ture from Oberp­faf­fen­hofen spe­cial-pur­pose air­port
Image 1/7, Credit: DLR (CC-BY 3.0)

Departure from Oberpfaffenhofen special-purpose airport

The FLEX­OP flight demon­stra­tor took off on its maid­en flight on 19 Novem­ber 2019. Var­i­ous flight ma­noeu­vres were suc­cess­ful­ly test­ed dur­ing the 25-minute flight over Oberp­faf­fen­hofen spe­cial-pur­pose air­port.
High in the air – light and stable
High in the air – light and sta­ble
Image 2/7, Credit: DLR (CC-BY 3.0)

High in the air – light and stable

The FLEX­OP flight demon­stra­tor took off on its maid­en flight on 19 Novem­ber 2019. Var­i­ous flight ma­noeu­vres were suc­cess­ful­ly test­ed dur­ing the 25-minute flight over Oberp­faf­fen­hofen spe­cial-pur­pose air­port.
Safe landing – first FLEXOP flight completed
Safe land­ing – first FLEX­OP flight com­plet­ed
Image 3/7, Credit: DLR (CC-BY 3.0)

Safe landing – first FLEXOP flight completed

The FLEX­OP flight demon­stra­tor took off on its maid­en flight on 19 Novem­ber 2019. Var­i­ous flight ma­noeu­vres were suc­cess­ful­ly test­ed dur­ing the 25-minute flight over Oberp­faf­fen­hofen spe­cial-pur­pose air­port.
FLEXOP team after the successful maiden flight
FLEX­OP team af­ter the suc­cess­ful maid­en flight
Image 4/7, Credit: DLR

FLEXOP team after the successful maiden flight

The flight test team is de­light­ed with the suc­cess­ful maid­en flight of the FLEX­OP flight demon­stra­tor, which was car­ried out on 19 Novem­ber 2019 at Oberp­faf­fen­hofen spe­cial-pur­pose air­port by re­searchers from DLR and TU Mu­nich.
Pre-flight preparations
Pre-flight prepa­ra­tions
Image 5/7, Credit: Fabian Vogl / TUM

Pre-flight preparations

The FLEX­OP flight demon­stra­tor un­der­goes ex­ten­sive pre-flight prepa­ra­tions to test new su­per-ef­fi­cient wings.
Flight demonstrator in front of the ground control station
Flight demon­stra­tor in front of the ground con­trol sta­tion
Image 6/7, Credit: Fabian Vogl / TUM

Flight demonstrator in front of the ground control station

The flight tests for the EU FLEX­OP project took place at the Oberp­faf­fen­hofen spe­cial-pur­pose air­port.
Computer workstations in the ground control station
Com­put­er work­sta­tions in the ground con­trol sta­tion
Image 7/7, Credit: Fabian Vogl / TUM

Computer workstations in the ground control station

The screens show the flight route and field of view of the flight demon­stra­tor to guide it through the airspace.
  • Novel wing designs can make aircraft lighter
  • Partners from six EU countries are working on new technologies to control flutter
  • DLR offers expertise in wing design and active damper control
  • Focus: Aeronautics, digitalisation

In cooperation with other institutions, researchers from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and the Technical University of Munich (TUM) have succeeded in developing new technologies for lighter yet extremely stable wings. With the help of these innovative wing designs, flying could soon become both more environmentally friendly and less expensive. The aeroelastic wings made their first flight on 19 November at Oberpfaffenhofen airport.

Wings with longer spans and lower weight generate less drag – and are therefore more energy efficient. More efficient lift could reduce kerosene consumption and thus reduce emissions and costs. The limiting factor for the construction of such wings is the aerodynamic phenomenon of flutter. Wing oscillations become stronger and stronger due to drag and wind gusts – much like a flag flying in a strong wind. "Flutter causes material fatigue and can even lead to the failure of the wing attachment to the fuselage," explains Sebastian Köberle, a researcher at the TUM Institute of Aircraft Design. Although any wing will begin to flutter at sufficiently high speed, shorter and thicker wings have greater structural stiffness, and hence greater stability. Building wings with longer spans that are just as stable and stiff would make them much heavier. In the European Flutter Free FLight Envelope eXpansion for ecOnomical Performance improvement (FLEXOP) project, researchers from six countries are working on new technologies to control flutter while allowing wings to be made lighter.

Wings avoid wind

The TUM researchers are responsible for the design and execution of the flight tests that demonstrate the actual behaviour of the two novel wings developed by the project – the aeroelastic wing and the flutter wing. The TUM team first built the three-and-a-half-metre-long and seven-metre-wide flight demonstrator and integrated the various systems provided by the European partners. A particularly light wing, which has now been flown for the first time, is an aeroelastically optimised wing constructed from carbon-fibre reinforced composites. It was developed by DLR in Göttingen, in collaboration with Delft University of Technology. The researchers were able to influence its bending and torsional behaviour through a special alignment of the fibres during the construction of the wing. “When the wing is bent by aerodynamic forces, it rotates simultaneously and thereby reduces airflow-induced loads,” says Wolf-Reiner Krüger of the DLR Institute of Aeroelasticity in Göttingen.

With the help of the reference wings, the TUM researchers worked in advance to have the flight demonstrator automatically fly predefined flight test patterns. They devised optimum settings and developed manuals and checklists for the flight tests. "The flight demonstrator has to fly fast enough with the new wings that they would theoretically have to flutter," explains Köberle. “We have to be sure that nothing goes wrong at such high speeds."

"The aircraft must remain visible from the ground, so that the researchers can intervene at any time. This means that the flight manoeuvres are flown within one kilometre of the ground control station. The extensive test flights followed completion of complex preliminary work. "Everything worked out as we imagined it would," says Köberle. "Now we will begin evaluating the data."

Active damper control for the 'flutter wing'

Another super-efficient wing developed in the project is the 'flutter wing'. This is a TUM design and is made of fibreglass. If fluttering occurs, the outermost flaps are extended. They act like dampers. "The active flap control developed at DLR considerably increases the possibilities for a much lighter design," says Gertjan Looye of the DLR Institute of System Dynamics and Control in Oberpfaffenhofen, which manages DLR's share of the project. A second flight control system is being developed by the Computer and Automation Research Institute of the Hungarian Academy of Sciences (MTA SZTAKI). Project Manager Bálint Vanek of MTA SZTAKI adds: "Such a wing would make it possible to transport 20 percent more cargo or to reduce the required fuel by seven percent." The technology is particularly complex, so tests on this wing will take place at a later date.

Both variants of the super-efficient wing have already been evaluated during static vibration tests conducted at the DLR site in Göttingen.

From demonstrator to passenger aircraft

The wings will not only be used on a flight demonstrator. In a further step, the results of the project will be transferred to configurations for transport and passenger aircraft.

The partners

The partners in the EU FLEXOP project are the Hungarian Academy of Sciences, Airbus Group Innovation, Airbus Group Limited, FACC Operations GmbH, INtegrated Aerospace Sciences COrporation (INASCO), Delft University of Technology, the German Aerospace Center (DLR), the Technical University of Munich, the University of Bristol and RWTH Aachen University.

Contact
  • Falk Dambowsky
    Ed­i­tor
    Ger­man Aerospace Cen­ter (DLR)
    Me­dia Re­la­tions
    Telephone: +49 2203 601-3959
    Fax: +49 2203 601-3249
    Linder Höhe
    51147 Cologne
    Contact
  • Dr. ir. Gertjan Looye
    Ger­man Aerospace Cen­ter (DLR)
    Sys­tem Dy­nam­ics and Con­trol
    Telephone: +49 8153 28-1068
    Münchener Straße 20
    82234 Weßling
    Contact
  • Wolf-Reiner Krüger
    Head of Loads Anal­y­sis and De­sign
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Aeroe­las­tic­i­ty
    Telephone: +49 551 709-2808
    Fax: +49 551 709-2862

  • Dipl.-Ing. Sebastian Köberle
    TUM In­sti­tute of Air­craft De­sign
    Tech­ni­cal Uni­ver­si­ty of Mu­nich (TUM)
    Telephone: +49 89 289 16748

    Contact

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