In the first part of the project (2019-2022) icing detection technologies were developed and matured, with a focus on Appendix O icing conditions.
Moreover, several icing wind tunnel (IWT) facilities enhanced capabilities to represent Appendix O conditions. As no standardised procedure exists for icing wind tunnels to generate and detect Appendix O icing conditions, extending icing wind tunnel capabilities towards the Appendix O icing regime resulted in valuable insights and gaining understanding. This includes measurements with reference instruments conducted in different icing wind tunnels and comparison and consistency analysis for relevant icing parameters. Ten different technologies with various physical principles for directly detecting ice accretion or atmospheric icing conditions were developed and matured with the EU funding (one technology for airborne scientific and reference measurements and nine aiming at applications for operational air transport application).
Eight technologies provided testing results in different icing wind tunnels in Appendix C and O conditions. Most sensor technologies were able to demonstrate the detection of a large portion of the Appendix O test points while at the same time ensuring very good detection capabilities for Appendix C conditions. Furthermore, some sensors are capable of providing specific relevant icing parameters like liquid water content and median volume diameter, which is considered as a very beneficial input for the hybrid ice detection system.
The hybrid ice detection system was specified and initial considerations of certification aspects were developed in close cooperation with aviation certification authorities, aircraft manufacturers, pilot representatives and research institutions. Subsequently, a suitable hardware and software architecture was developed in order to be flight tested. As part of the hybrid approach, a performance-based indirect ice detection system was developed and matured, able to early detect even relatively light ice accretion on the airframe by utilising fundamental knowledge about the changes of aircraft characteristics under icing conditions.
The second part of the project (2023) was dedicated to flight tests in natural icing conditions including Appendix O and the evaluation of the different icing technologies. Two flight test campaigns took place in early 2023:
- in North America with Embraer Phenom 300;
- in Europe with the French ATR 42 environmental research aircraft of Safire.
These campaigns served to test and demonstrate eight of the direct ice detection technologies under development in SENS4ICE, as well as the hybrid ice detection system, including indirect ice detection. Extensive meteorological support allowed to encounter icing conditions of interest including Appendix O conditions in flight. Furthermore, remote icing detection technologies were investigated during the European campaign, based on satellite data or airborne weather radar data. All detection technologies performed well during the flight demonstration and generally exhibited robust and timely ice detection behaviour. The technology readiness level (TRL) was increased to TRL 5 in several cases and even TRL6 for many technologies. Particularly the hybrid ice detection approach showed in flight tests the capability to provide both early detection and a continuous monitoring of ice accretion on the aircraft. This is very promising and can allow to assess the effectiveness of ice protection systems and/or ice accretion on unprotected surfaces during flight. Furthermore, this can facilitate more efficient use of ice protection systems in order to reduce energy consumption. Particularly the indirect detection is a software solution with retrofit capabilities and may be implemented very cost efficient. In general, the demonstrated novel ice detection technologies facilitate broad and promising possibilities for applications for many different air vehicle types (including greener aviation, UAV, urban air mobility and fully electrically powered aircraft) and further benefits including ensuring operational safety and supporting certification activities.
