With icing still a prevalent threat to air transport, a European-funded project has been exploring hybrid detection of ice build-up through a combination of new sensor technology and analysis of degraded aircraft performance.
The project, SENS4ICE, drew up its findings earlier this year and the results are being presented at a number of aviation conferences.
Ten different candidate direct ice-detection sensors, all based on diverse physical principles, were assessed of which eight progressed to a flight-test programme.
Four were fitted to an Embraer Phenom 300 testbed and the other four installed on French environmental research agency Safire’s ATR 42-300.
But crucially both aircraft also featured an indirect ice-detection algorithm which, complemented by the sensors, forms a hybrid ice-detection system.
The indirect ice-detection function uses an accurate reference database to compute the aircraft’s expected flight performance, which can then be compared with the performance experienced.
Any difference in the two can then be analysed by the system, along with the direct ice-sensor data, to determine the likelihood that performance degradation is due to the accretion of ice.
Flight-testing took place last year, in February-March over North America with the Phenom, and Europe in April with the ATR.
Analysis of the flight-test data shows the advantage of hybrid detection are “undeniable”, says the SENS4ICE final report.
It says the direct-detection technologies are “very promising” while the indirect detection algorithm was “able to announce the performance degradation during all icing encounters” during the flight-test campaign.
The algorithm could also detect reduced performance resulting from residual ice accretion on the airframe after leaving the icing clouds, it adds.
“Although the algorithm is only reactive to conditions where the flight performance is already degraded due to ice accretion on the aircraft surfaces,” it states, “it provides a high potential for applications where no direct sensing technology could be applied or is too complex or expensive.”
These applications, beyond air transport, could include smaller aircraft types, advanced air mobility vehicles or unmanned craft.
Validation of hybrid detection through the flight-test campaign has enabled the project to consider the approach as having achieved technology readiness level of TRL5 under the thresholds of the EU’s Horizon 2020 initiative.
The final report acknowledges, however, that further research for maturation is necessary because the testing covered a “relatively small” part of the icing envelope, primarily freezing drizzle, and a broader regime – including freezing rain – would need to be encountered to provide a more thorough assessment of the SENS4ICE technologies.
Along with the potential safety benefits, it adds, hybrid ice detection could also support “significant reduction” in fuel consumption through a more efficient use of ice-protection systems.
Direct ice-detection sensors developed for the project were developed by companies including Collins, Safran, Honeywell and AeroTex plus research organisations INTA, ONERA and DLR. The test programme also involved icing windtunnel analysis.
