Testing Aeroelastic Wing Technology within the German FLEXOP Solution

Nowadays, the goal to create aircraft that is safer, greener, and more cost-effective can be achieved by innovational aircraft design methods. An integrated design approach already performed by the German scientists will lead the industry to significant performance enhancement of aircraft in the future.

The engineering team from TUM (the Technological University of Munich) in tandem with the German Aerospace Center is going to conduct the first test flights that take place at an airfield in Oberpfaffenhofen. A specific airplane type will participate in the event. It is equipped with specific wings that are much lighter than conventional wings but wider in the span. The specialists believe that aeroelastic wing technology would make aircraft more eco-friendly due to reducing dioxide emissions. Moreover, the technology would contribute to financial profitability because of getting more fuel-efficient.

The above-mentioned are in general called the German FLEXOP solution. Although all the modern research resources are directed towards Flying without Wings , German specialists follow the traditional “with wings” approach in their project.

Key Goals of FLEXOP

FLEXOP is a European project with the target to design both lighter and wider wings that may cope with such aerodynamic phenomenon as flutter . FLEXOP researchers believe that a coherent functioning of flight control systems and wing aeroelasticity provide new opportunities to develop the designs unviable previously.

A set of approaches designed by FLEXOP engineers introduces effective ways to speedily fit existing design options into derivative aircraft so that they avoid a flutter challenge revealed during the design process. They are sure about the following methods on how to achieve the goal:

· They should optimize the efficiency of existing wings. This is possible to achieve if they increase span without redundant structural weight. Additionally, engineers should consider appropriate aeroelastic tailoring modifications to implement the new wing option;

· FLEXOP specialists should find out tools for accurate flutter control synthesis and analysis. Those factors will add much to better flutter supervision during design, certification, and implementation. Moreover, such tools should enable aircraft to fly with the stretched wing at various airspeed;

· Finally, engineers are to check the accuracy of designed tools using an appropriate experimental platform. That presupposes opportunities for a deeper investigation to represent the intersectoral design cycle. Potential customers, who will buy FLEXOP solution, need a warranty that they gain the real chance to optimize aircraft performance due to integrated work of aeroelastic tailoring and flutter control system.

The above-mentioned goals were implemented early in the design process. So, the time came for testing aerospace wing technology. Official flight test data will be announced on the project website to fix a benchmark for aerospace communities around the globe. Testing results will serve as a hint regarding possible certification standards for all the future kinds of flexible aircraft.

The FLEXOP project was introduced during the 9 th EASN International Conference on “Innovation in Aviation & Space.” This time, the annual reputable event took place in Athens (Greece) during September 3-6. The audience witnessed five presentations that demonstrated the project nature in general followed by the common significant achievements already gained thanks to the project partners.

Aeroelastic Wings to Fight with Flutter

Individuals who have ever flown in a commercial aircraft are familiar with the following situation. When you are on board an aircraft (with light wings), you periodically feel the up-and-down motion of the wings’ tips.

They make extremely sensitive people feel anxiety. Such a thing is caused by wind gusts and aerodynamic drag. To understand the idea, you should imagine a flag flying in a strong wind. The above-mentioned is called flutter.

According to Sebastian Köberle, a scientist at the TUM Institute of Aircraft Design, this phenomenon may lead to material fatigue and, as a result, problems with the wing attachment to the aircraft’s fuselage.

On the one hand, it is not profitable to refuse using light wings because they reduce fuel consumption. On the other hand, such wings tend to be impacted by flutter.

Although any wing type may start fluttering as far as an aircraft gains high speed, it is an aeroelastic wing that will allow greater stiffness of the structure, and, thus, higher stability level to successfully cope with flutter.

Thus, currently, within the FLEXOP project, engineering specialists from six countries are doing their best to successfully test the technology of super light aeroelastic wings to control flutter.

Details on Testing

Engineering professionals from the Technical University of Munich are liable for the development and implementation of the series of flight testing. They want to discover the actual behavior of aeroelastic wings.

Firstly, the TUM specialists constructed the demo version of the wing with the sizing as of three and a half meters long and seven meters wide. Additionally, they adopted several systems received from the European partners on the FLEXOP project.

What is to be represented during testing? An extremely light wing! The construction is defined as an aeroelastically improved wing. It is designed with carbon-fiber-reinforced composites. The last is innovational material used in the aerospace industry due to its being super light feature.

The engineers of the German FLEXOP solution have found out the methods to influence its behavior of torsional and bending nature. It was done through a specific alignment of all the fiber levels during the design of the aeroelastic wing.

In the latest interview with the press this autumn, Wolf-Reiner Krüger (DLR Institute of Aeroelasticity) explains that “as far as the wing is affected by aerodynamic forces, it momentarily starts rotating. It is performed by the wing simultaneously to that. This way the aeroelastic wing minimizes airflow-infused loads.

The TUM researchers have revised the most optimal settings as well as created detailed checklists and manuals for their flight testing. This was done beforehand for the demo version to automatically perform all the predefined patterns of the test flight. They expect that the “aeroelastic” aircraft will fly with high speed. According to such conditions, the new wings would theoretically start fluttering. However, the testing will show the real situation.

Sebastian Köberle says the testing will be considered as being successful if nothing goes wrong with aeroelastic wings at such a speed of an aircraft.

During the testing, the aircraft will remain under a review of the engineering team from the ground. This guarantees that they will be able to interfere if something unpredicted happens. The flight will be conducted within the distance as of one kilometer of the ground control center.

Ambitious Plans

Researchers plan that the testing results will be transferred for check in the automotive industry as well. In particular, the configurations are going to be implemented in transport and passenger aircraft. Regarding the last sector, the project’s commercial partners are going to be Bristol University and Airbus.

Moreover, during the press conference, the representatives from both sides commented that they are planning to introduce one more type (more complex) of the aeroelastic wing in 2022. This time, their partner will be the Computer and Automation Research Institute of the Hungarian Academy of Sciences.