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Innovative Systems to Prevent Ice on Regional Aircraft

Periodic Reporting for period 2 - InSPIRe (Innovative Systems to Prevent Ice on Regional Aircraft)

Reporting period: 2019-09-01 to 2021-12-31

In the current development of the More-Electric Aircraft technological portfolio, a full electric wing ice protection system plays the key role to eliminate bleed air and pneumatic devices. In this framework, the adoption of an electrothermal ice protection system instead of an electromechanical one allows easy integration with laminar wings and/or morphing leading edges, thus resulting in it being more suitable for implementation in the future regional aircraft.

The EU CleanSky2 funded research project InSPIRe focusses on designing, developing and manufacturing a demonstrator for the wing ice protection system (WIPS) of the Leonardo regional aircraft concept.

To meet the design and energy constraints, the solution proposed by InSPIRe is geared towards:
i. optimizing the areas that are ice protected and their power distribution in the morphing leading-edge;
ii. optimizing the heater scheduling and the control logic;
iii. exploring the potential for removing the energy intense parting strip to minimize power consumption for a thermal de-ice system to be suitable for a Regional platform;
iv. applying an innovative, light weight, highly reliable and durable electrothermal technology integrated into the LE composite structure.

Performance verification will be pursued by means of an Icing Wind Tunnel (IWT) test campaign to contribute to reaching TRL5 for the selected IPS technologies.
In WP1 initially the flight conditions and wing geometry of the regional aircraft were defined. The first step of analysis was to study which part of the aircraft wing needs to be protected during an icing encounter.The beneficiaries ATX and AIT analyzed the impingement of supercooled water droplets on the main wing with respect to an extensive set of aircraft flight conditions and the related icing conditions (as specified in CS-25 Appendix C for atmospheric icing conditions and in Appendix O for Supercooled Large Drop icing conditions) by means of numerical simulation applying in-house and commercial flow solvers. Some hundred simulations needed to be performed to identify the impingement limits on the upper and lower wing surfaces. From them, a first estimate of the wing extension that needs to be protected from icing was deduced.
Thermal analysis at the coldest and warmest conditions was performed by ATX for an initial leading-edge composite structure and material layup to obtain first estimates of the maximum total power demand of the WIPS, the maximum internal structural temperature and water runback. The feasibility of a pure de-icing system with low power demand by removing the always powered parting strip was studied. The first system concept was developed, including the distribution and maximum electrical power density of the heater elements, a basic structure of the WIPS control laws (developed by ATX) and power electronics (developed by AIT).

In WP2, a concept for a morphing leading-edge structure was introduced and InSPIRe adapted its initial IPS concept to integrate its main characteristics, specifically by considering a LE (Leading edge) skin with non-uniform thickness distribution.
A concept to integrate the heater layer into a composite LE structure that is compatible with the requirements of the morphing leading edge was developed by the beneficiaries PEAK and VILL and a first prototype has been built to test its manufacturing. The VILL heater layer technology is a carbon based (non-CNT), lightweight, elastic, thin, polymer coating with high power density, up to 120 kW/m², that can be integrated into composite structures and is easily applicable to 3D surfaces. It is tested according to DO-160G, is REACH compliant and has been already tested in the icing wind tunnel (IWT) and in-flight conditions for wing and rotor configurations.

In WP3, the WIPS system design was refined and finalized, both in terms of heater definition (zoning, scheduling, power required) and integration into the leading edge. The ice protection performance placed the focus on a solution without a parting strip to minimize the power requirement.
Development testing on coupons was performed to validate the WIPS system for aeronautically relevant environmental conditions (temperature, altitude, humidity, corrosion, flammability), electromagnetic compatibility, electrical integration, and mechanical characterization. The heater layer integration concept was revised upon the electrical testing results and integrated into the WIPS system concept and the WIPS demonstrator design.
The structural design of the demonstrator was developed by the beneficiary PEAK that includes the main structural components, i.e. the leading edge integrating the electrothermal WIPS (glass fiber structure with metallic erosion shield), the central body and an adjustable flap (both from aluminium), side plates to interface the test article with the lateral turn tables of the IWT, a flap tilting and locking mechanism, and assembly parts.
A preliminary IWT plan and procedure has been produced as a collaboration between ATX and CIRA. The test points will cover aerodynamic calibration and IPS performance evaluation under atmospheric icing conditions (CS-25 Appendix C envelope) and Freezing Drizzle conditions (CS-25 Appendix O envelope). The acquired measurement data will be used further to validate the numerical simulations.

In WP4, the IPS demonstrator and components design was completed. Unique tools and production processes had to be established to produce the leading edge. Major challenges, which influenced the design of the part and the tools significantly, were (a) the integration of the busbars including its electrical connection, (b) the integration of a large number of miniature thermocouples needed to monitor the temperature distribution within the structure, and (c) the bonding to the Nickel erosion shield onto the leading edge. In fact, the erosion shield bonding was only successful with a revised bonding strategy after the first attempt had resulted in incomplete bonding at the leading edge highlight. Furthermore, the IPS control system for IWT demonstration was developed and the control box hardware built and tested.
In the last period of the project, the InSPIRe WIPS system concept will be qualified at the climatic chamber of AIT and finally demonstrated the Icing Wind Tunnel of CIRA to reach TRL5.

Approximately 20% of the global regional aviation market is concentrated in the EU-27, i.e. short-to-medium haul flights within the EU, characterized by an average flight distance of 600 km and approximately 200 million passengers per year (25% of all passengers flown in the EU in 2016). The targeted low-power WIPS is a key technology for the development of the future more-electric regional aircraft. Adopting such a low-power technology can double the energy efficiency of the aircraft IPS and reduce the total fuel consumption of the aircraft by 0.5%. Thus 5 million tonnes of CO2 per year could be saved by InSPIRe WIPS technology.
Furthermore, the CS2 regional aircraft programme, with InSPIRe as a partner, aims at strengthening the European aviation industry.
Assembled InSPIRe demonstrator
Conceptual sketch of InSPIRe technology development and TRL step-up
Design of the InSPIRe demonstrator