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Scaled Test Aircraft Preparation and Qualification

Periodic Reporting for period 3 - SCALAiR (Scaled Test Aircraft Preparation and Qualification)

Reporting period: 2019-10-01 to 2021-03-31

In Clean Sky 2, Platform 1 of IADP Large Passenger Aircraft (LPA), WP1.3 aims at validating scaled flight testing as a viable means to de-risk disruptive aircraft technologies and aircraft configurations to a high technology readiness level. As part of LPA 1.3 the, LPA WP1.3.3 SCALAiR project will develop the demonstrator of a scaled reference aircraft to show that it can be used to obtain performance characteristics that are representative for the full-scale aircraft. The aim is to develop a geometrically scaled version of a reference aircraft such that the transposition from the full scale to the scaled demonstrator can be correlated.

Using the A320 as well-known reference aircraft enables LPA 1.3 to demonstrate the possibility to design and manufacture a scaled flight demonstrator having an overall behavior that is representative for the full-scale aircraft.

Two flight demonstrators were planned, of which only the SFD is developed within this project:
• Scaled Flight Demonstrator (SFD): The SFD will have the full representation of the geometry and will be equipped with the complete arrangement of the flight and data-acquisition systems. It will be a scaled version of the A320 with the exception of the aeroelastic behavior. The SFD will be used to check the flight control and data acquisition systems and can be used for static parameter identification.
• Dynamically Scaled Flight Demonstrator (DSFD): The DSFD has the same outer geometry and flight control system, but will be designed to have identical aero dynamic behavior of the reference aircraft. The DSFD will be used to demonstrate the representativeness of the overall dynamic behavior of the full-scale aircraft.

The attached picture illustrates how scaled demonstrators could be a valuable intermediate step between the already existing experimental facilities and computational capabilities (left side) and the full scale development of disruptive configurations for transport aircraft (right side).
The original proposal was to use the geometry of a reference aircraft for the Scaled Flight Demonstrator (SFD) design. Due to issues with the release of actual geometry data the decision was taken to develop the geometry for the SFD based on Open Source data and guidance from the reference aircraft OEM (Airbus). The final SFD geometry is assessed by comparing the 3D models and by Computational Fluid Dynamics by a partner within LPA 1.3. In the first period of the SCALAiR project the 3D model of the SFD has been developed, starting with the design of the aerodynamic surfaces. Also the best scaling factor (1:8,5) for the SFD was selected, using a Matlab tool whereby the scaling factor can be optimized given scaling requirements and design constraints. 2D and 3D analysis techniques were used to verify that the SFD geometry can fly given the selected scaling factor. The final SFD geometry was approved within LPA 1.3 to start the further design. These inputs were used to calculate the aerodynamic loads, hinge moments of the control surfaces and basic performance parameters, as drivers for the selection of components, e.g. actuators, engines and the structural design of the SFD. The fact that the SFD will undergo a wind tunnel test puts additional requirements on the structural design of the SFD. The procurement, design and manufacturing of the SFD components and structure has started.

Partially independent of the SFD geometry is the design of the electrical system for the SFD, including the Avionics Rack. Using the operational requirements defined within LPA 1.3 the high level architecture of the electrical system has been defined and the basis autopilot to be used has been selected. Most components of the electrical system, e.g. datalink system, power supply, vehicle control unit, etc. have been procured or are under development.

Two projects in LPA 1.3 provide subsystems that need to be integrated in the SFD; the NOVAIR project that designs the Flight Test Instrumentation system used to monitor and measure specific parameters for the scaling analysis and the analysis of the SFD behaviour. The HyperF project designs the Guidance and Navigation Computer that will initiate and control the specific test maneuvers of the SFD. These systems have a close interface with the SCALAiR project both electrical interfaces and structural interfaces.

In the second half of 2019, financial issues have been identified by NLR. The critical risk as identified in the proposal that adjustments or redesign of the new vehicle is too expensive and time consuming w.r.t. allocated resources has materialized. Discussions were held between WP1.3 partners, PL1 leader and CSJU and a recovery plan was proposed and agreed in Q1 2020. It was agreed that the remaining activities in 2020 and later are funded under the NOVAIR project. The SFD has been tested in the wind tunnel of DNW in April 2021. Qualification and mission flight tests campaigns are planned to be performed in September-October 2021.
With an actual dynamically scaled model, based on an existing full scale vehicle, the viability for future applications can be investigated. With the methodology of scaling validated, with a proven set of rules and procedures, novel configurations can be subjected to scaled model testing as well. Besides regular dynamic stability and control models, aircraft simulators can be extended with dynamics outside the normal flight envelope. Pilots can be trained in post stall motions of which the knowledge results from scaled model testing. This project can lead towards a significant reduction in aircraft accidents.

From a financial, operable as well as technical point of view there are opportunities for scaled flight testing, going beyond the state-of-the-art. In fact, considering scale models, at the moment Europe is not at the state-of-the-Art: United States companies are the major contributors. SCALAiR extends the scope by increasing the number of applications and uses an existing full-scale aircraft so that representativeness can be actually analyzed.
Use of Scaled Flight Testing for the development of disruptive aircraft configurations
Final SFD Geometry including Air Data Boom