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LOw Subsonic Investigationof a largecomplete Turboprop Aircraft

Final Report Summary - LOSITA (LOw Subsonic Investigationof a largecomplete Turboprop Aircraft)

Executive Summary:
In LOSITA an aerodynamic characterization of a Green Regional Aircraft configuration comprising laminar-flow technology as well as rear-mounted turbofans was performed by means of wind-tunnel tests, with a special emphasis on innovative solutions for high-lift devices. In order to achieve this a consortium of three partners was build and implemented. These three partners are:
- IBK-Innovation in charge of project management and model design and data post-processing.
- RUAG for developing an engine simulator allowing to simulate the rear-mounted turbofan
- EUROTECH (replacing REVOIND) for model manufacturing
In order to perform the test-activities specific requirements for the tests and the WT-model needed to be defined. Due to the fact that the model is large (span of 4.9m) all activities needed to be planned with care including logistics onsite in the WT. The WT was chosen to be the RUAG Large-Wind Tunnel in Emmen.
During the project a wind-tunnel model with a strong emphasis on reducing time for configurational changes was designed. This included solutions for actuated devices, which could work together with a hinge-moment measurement solution.

In the project RUAG performed the development of the engines to be tested in the LOSITA WT-Model and EUROTECH was in charge of manufacturing the model.
Due to the need for substituting a partner project management was strongly challenged. The result was a major project adaptation in terms of budget distribution as well as overall project schedule. EUROTECH was successfully implemented substituting REVOIND as a partner and took over the manufacturing activities. Due to the need to cope with a reduced budget and time available the model was simplified, thus removing control-device actuation. The model was delivered to the Wind-Tunnel in Emmen in Q1/2017.
After model availability the tests were performed in the RUAG-Wind-Tunnel using a test-matrix, including both powered and unpowered tests, jointly defined together with the Topic Manager. The Wind-Tunnel tests were performed as planned, allowing a characterization of the noise acting on the wing and analyzing the effect of low-noise technologies developed with the GRA-ITD.
As a final outcome the project can present the aerodynamic characterization of the GRA-configuration.

Project Context and Objectives:
The story of the turboprop took an interesting turn in the 1970s-when a strong increase of the fuel prices drove research activities to the study of more efficient aircraft configuration. Throughout the late 1970s and early 1980s, NASA engineers worked on an effort dubbed "the Advanced Turboprop Project"-a US government-funded study to examine the feasibility of developing the turboprop engine as a viable competitor to the larger, less efficient turbojet and turbofan designs found on airliners of the day. The studies showed that the turboprop configurations were very efficient at cruise speeds up to about Mach 0.65 providing a fuel savings between 10 to 20 percent with respect to equivalent technology turbofan aircraft. On the other hand, above this speed, the increased drag due to compressibility losses on the propeller blades causes efficiency to fall rapidly. One way to lower compressibility losses is to increase the Mach number at which drag rise occurs by using thinner airfoil sections. In the past, when the fabrication was limited to metal blades, the construction of very thin blades was not possible and the development of high speed turboprop aircrafts stopped leaving space to turbofan configuration. Now, with the use of composite materials and advanced construction techniques, it is possible to construct blades with thinner airfoil sections and more optimum shapes (sweeping the blade leading edge, scimitar geometry, etc) that can operate in high subsonic conditions (up to M=0.8). Therefore, taking into account the fuel saving and the lower operating costs, the optimization of the turboprop configuration is going to become again one of the most important matter of research studies. This is widely demonstrated by the strong interest that the main international agencies are dedicating to the design of advanced Turbo-prop aircrafts. The main research branches are focused on the design of high efficiency and low noise configuration, on the fuselage noise attenuations for passenger comfort, on the design of innovative and high efficient propellers, and on the optimization of the engine-airframe integration. Within this context, special care is dedicated to the integration of turboprop engines into the airframe presenting some unique aerodynamic challenges. The integration of a turboprop is more critical than that of a turbofan because of the large interaction between the slipstream and wing. The propellers slipstream has an essential influence on the lift and stability and controllability characteristics of an aircraft due to interaction with the wing, fuselage and empennage. On the other hand, the nacelles, fuselage, wing and other aircraft components influence the flow velocity distribution over the Propellers plane of rotation, and as a consequence alter the aerodynamic loads on the Propellers blades and their thrust characteristics in comparison with free-stream flow. To reduce the uncertainties associated with the installation of these advanced turboprop propulsion systems, combined experimental and analytical activities are necessary. Modern computation methods are mainly based on ideal fluid theory, and are not able to fully reveal and take into account the above-mentioned effects. Experimental activities are therefore the main way to study the problems of Propellers and airframe interaction and in particular to assess the magnitude of the aerodynamic interference, to understand the aerodynamic phenomena associated with the installation, and to develop an analytical and experimental data base for numerical comparisons. This is especially true in the case of aircraft of unusual layout with an unusual position of the engines and empennages. Experimental tests on turboprop configuration typically use unpowered engines providing only main aerodynamic characteristics without simulating the interference between the propulsion system and both the airframe and aerodynamic surfaces (wings, fuselage and empennage). To provide more accurate experimental estimates of both aircraft performance and stability, challenging experimental tests using active propellers are necessary. The main innovative aspect of LOSITA regards, in fact the optimization of an Advanced Turbo Prop Regional Aircraft by mean of wind tunnel tests on a complete and powered aircraft Model. Wind tunnel tests are performed:
• to optimize the integration between nacelles and wing (several nacelle shapes and attaches will be tested);
• to evaluate engine thrust effects on the aerodynamic performances and on the aircraft stability;
• to evaluate the performances of several trailing edge high lift devices and flap deflections(corresponding to take-off, intermediate and landing positions) and settings (gap / overlap combinations);
• to evaluate the performances of ailerons, elevator, rudder and airbrake/spoilers performances;
In order to fulfill these goals, the LOSITA project can be split in several phases having each one several innovative aspects:
I. Design and manufacturing of a scaled modular A/C model
II. Design and Manufacturing of the powered engine simulators
III. Model Assembly and ground testing
IV. WT test campaign.
The primary difficulty in design of scaled A/C model is to meet adequate structural integrity under aerodynamic loads and the model modularity to allow the setting of the different configurations and easy access to the instrumentation installed in the model. The modeling approach itself has to be innovative in order to speed-up the configuration changes during wind tunnel tests. One example for testing different High lift devices (HLD)-settings would be to use brackets which would allow fixing the HLD to a given position. This might lead to a lot of brackets, and for each change of the HLD-setting the test has to be stopped. This takes time for the manual changes and time for stopping the wind-tunnel and bringing it up to speed again. Therefore, the possibility to use actuators in order to be able to continuously change HLD-positions is an important aspect to be considered. A further innovative aspect in this project is the coupling of all these points with the design of complete scaled powered propulsion system to be integrated on the model airframe. In fact, even though models with propulsion are not essentially state-of-the-art but have been tested in the past, such a complex model with actuation, different configurations and engine propulsion certainly represents a challenging matter.
The design of a powered turbo prop engine involves several engineering aspects tightly linked together:
• Design of nacelles
• Design the propulsion system
• Routing of cables, pipes for the supply of the propulsion system.
The first one is a structural problem, viz, sizing the nacelle and the necessary connections to the propulsion system assuring that the flow-conditions encountered in flight are reasonably well simulated. Moreover forces generated by the propulsion system have to be supported by the nacelles and the wings to which the nacelles are connected. This problem is also coupled to the space constraints in the nacelles - to locate the propulsion system and assuring the necessary stiffness - as well as the fuselage, wings for the cabling of wires, pipes, etc. for the supply and control of the engine simulator.
From a technical point of view, the model has two wing mounted engine simulators. The proposed scheme is to use engine simulators powered by a hydraulic system able to set and keep thrust within 5% of the target value (as requested in the CfP). The design of such complex configuration within the given time and budget constraints is possible only thanks to the experience in the design of such system of the LOSITA consortium (and in particular of RUAG) and because the Emmen Wind-tunnel (the WT selected for testing) already has a suitable hydraulic infrastructure (4 pumps of 1000kW total power) that can be used for the purpose.
Finally, a subsonic wind tunnel test campaign is performed in the RUAG wind tunnel to assess the performance of the GRA turboprop aircraft configuration in take-off and landing conditions by testing high lift systems. In particular, the test campaign focuses on the optimization/estimation of the aircraft configuration (in terms of nacelle shape, trailing edge devices, movable surfaces, etc.) and on the validation of the resulting overall optimized aircraft architecture.
Considering that the LOSITA project involves many engineering fields (design and manufacturing of structural parts, design of electro-mechanic components, design of Hardware and Software for controlling and recording, design and manufacturing of engine simulators, wind tunnel activities),this project can be implemented only by constituting a consortium of specialists on their relevant topics that pool together their experiences.

Project Results:
Main S&T results/ foreground
The following scientific and technical results have been identified:
- LOSITA was able to perform the aerodynamic characterisation of the GRA-developed innovative aircraft configuration for next generation GRA Aircrafts. This includes the delivery of test-results usable for deriving aircraft stability and control data.
- LOSITA also delivered the comparison of the aerodynamic efficiency of different high-lift devices and two different winglet-devices. LOSITA was able to show the aerodynamic influence of the turboprop simulator on the overall results.
The technical results were delivered to the GRA-ITD and support the CS-GRA work performed in Clean Sky 1 and Clean Sky 2..
Within LOSITA several technical achievements were realised
- The use of actuated devices in the WT is not standard approach nowadays, however, it can improve the use of the WT test-time considerably. In LOSITA solutions for this were developed, unfortunately, due to the complex project setup, they were not chosen to be implemented into the final test. These solutions will be used in future R&D projects, in particular they are currently extended for implementation in the Clean Sky 2 project POLITE and will also be candidates for the project WTM-RECYCLE.
- Within LOSITA IBK has developed local balances to measure hinge-moments. For the same reason as the actuators this technology could not fully be exploited during the LOSITA-campaign, however, the knowledge generated is available and will be used in future projects.
- RUAG has designed a turboprop simulator which allows performing WT-tests in turbofan configurations taking into account the effect of the mass-flow through the turbofan on the overall aerodynamic performance. RUAG has demonstrated the performance of the solution successfully through the test in LOSITA.

Potential Impact:
Bringing together a complementary, in terms of competencies, set of SMEs and Industry,allows for commonalities to be identified and opens the possibility for cross-domain sharing of concepts, methods and tools in order to enable reusable embedded technology development. In addition, the LOSITA consortium includes one of the largest European Wind Tunnel with extensive experience in mechanical design of aircraft models, the development of hydraulic motors, on the development of equilibrium in the wind tunnel and sensors for measuring the wind tunnel testing. These transversal competences, added to the specific competences of the involved SMEs, enables the consortium to be extremely confident in solving any critical problem that requires interdisciplinary expertise, thus allowing LOSITA to address any technological innovation and/or any new model. It is expected that this cooperation between partners enriches their knowledge and their capability in design and manufacturing. On the other hand, the development of engine simulators for turbofan will increase the capacity of the wind tunnel that can offer this service to all European aeronautical industries. This allows increasing the competitiveness of the European aeronautical industries in the world.
The impact of this project will work on several different levels:
• Regarding JTI-Cleansky this project will help in solving important questions about the landing and takeoff flight conditions. In fact, the project aim to investigate the high lift devices more appropriate for turbo prop wings showing low noise and their application on future Green Regional Aircraft. On an international level this increases Europe’s competitiveness in the development of the future Green Turbo prop regional aircraft, since the landing and take-off flight conditions are strongly affected by these devices. Suitable high lift system, able to guarantee aerodynamic performance and to reduce noise emission (such as flap based on Liner technology) and optimized winglets will contribute to further improve the performance of this new Green Regional Aircraft allowing to match the future ACARE 2020 goals.
• Apart from an national level each partner that contributes to the project has several advantages:
o Insight into high fidelity test results for an advanced technology aircraft wing
o A reference project that shows competence on an international level
o All partners in the consortium have the opportunity to further increase their know-how by working in synergy and in an international context. In case of the SMEs this can be further exploited by transferring IP generated in this project into industrial applications. The research facilities strengthen their competence in their field of work.
o The SMEs will strongly interacted with one of the largest European Wind Tunnel (RUAG) and this provided a formidable chance to enrich their expertise
o partners such as IBK are giving lectures at universities. This allows transferring knowledge achieved in this project to future engineering generations.
• RUAG contributes to the project and will receive several advantages:
o Development and availability of engine simulators coupled to turbo prop, for future Turboprop Aircraft testing
This will contribute to increase the competitiveness of the European aeronautical industries because they will have a facility that can also simulate landing and take-off conditions by using engine simulators for turbo prop aircraft configurations.

Socio-Economic Impact/ Wider societal impact:
Due to the strong technical focus of this project the direct socio-economic impact of this project is limited.
Indirect IBK as well as EUROTECH as SME´s are seeing gender equality as one of the relevant topics for their human-resource strategy. Within IBK ~30% of the employees are female (seen over all technical units). Apart from that IBK is very supportive in enabling work-life balance, especially supporting young families with part-time jobs. This helps to keep young and very skilled professionals in the company, provides a good internal climate and a forward oriented mind-set.
Being able to positively support these projects as SME is therefore supporting IBK´s and EUROTECH´s strategies.
All work packages undergo an internal check from each partner for exploitation. The management of knowledge and intellectual property, as well as the establishment of exploitation and dissemination strategies are dedicated
− To manage the generated knowledge and confidentially-related issues.
− To identify the results that can be disseminated (through publications, conferences, workshops, technology transfers)
− To identify results that should be protected (through patents, copyrights or secret) and - if necessary - to achieve an agreement in case of joint ownership.
− To analyse end-user requirements and a potential market as an exploitation strategy.
− Intellectual Property Rights and dissemination of knowledge are not incompatible, provided that they are based on clear principles and rules.
Ownership of results, mutual granting of access rights, IP protection (including patenting) and licensing policy are defined in a Consortium Agreement between the three participants.
Currently the following items have been identified for further exploitation:
- RUAG has developed solutions for designing, manufacturing, operating and testing turboprop simulators. This strongly improves their service portfolio and will be directly exploited by them.
- IBK has developed solutions for quick model changes and tested them up to prototype level. Due to the complex management issues arising during the project the ESICAPIA-model was simplified, thus not allowing to test these features. However, the design was matured at IBK and IBK will exploit this in future projects.
- IBK has designed component balances for all movable devices. Similiarly to the model actuation activities those were not used during the tests, however, considerably knowledge at IBK was developed and will be exploited.
- In LOSITA there was a need to quickly rotate the model after the aerodynamic test campaign to implement it into the acoustic configuration. This was realised in cooperation with RUAG in a very efficient way, reducing the WT-blocking time and improving in total the output.
- EUROTECH has created a track-record which allows them, as a small company and startup, to foster their situation by having a reference project.

List of Websites:
no public website
Coordinator contact:
Stephan Adden
IBK-Innovation GmbH & Co. KG
Butendeichsweg 2
21129 Hamburg