An indirect technique for aircraft in-flight icing detection was matured and combined with direct sensing in a novel hybrid icing detection approach. The indirect icing detection (IID) is based on aircraft characteristics variations. The hybrid approach is particularly addressing reliable detection of supercooled large droplets (SLD) icing conditions, which are potentially safety critical and very challenging to detect. The ice detection technologies were successfully demonstrated in flights in relevant natural icing conditions in the EU project SENS4ICE, particularly also the indirect ice detection. Apart from good results for indirect individual in-flight icing encounter detection, the overall flight data for one campaign was evaluated. The reliability of the IID output for major drag increase is very good. For minor drag increas the IID appears to be more sensitive with regard to the actual overall aircraft performance degradation compared to direct icing sensors.
Schwarz et al. (Tue,) studied this question.