Wind tunnel and flight testing of a lamb wave based ice accretion sensor

Abstract

Ice accretion happens, when atmospheric water freezes on structures. If the ice accretion is too heavy, it can lead to a catastrophic failure of the structure. This is especially the case in aviation, where airplanes regularly encounter freezing temperatures in the air as well as atmospheric. To mitigate icing, modern aircraft are equipped with ice protection systems. Up to now however the activation of these systems is either precautionarily ion the case of predicted icing conditions or the pilot recognizes ice accretion. To speed up the detection of airframe icing and to avoid the energy consumption of anti icing systems when no ice accretion happens, icing sensors would be helpful. Within the EU project SENS4ICE, different icing sensors are developed and tested, of which one will be presented in detail in this presentation. This sensor is based on sending ultrasonic lamb waves through a structure, which is prone to ice accretion, therefore it is called Local Ice Layer Detector - LILD. Upon ice accreting on the surface where the sensor is located, the transmission behaviour of the structure changes and this can be seen in the lamb wave pattern. This principle has been tested in a wind tunnel test in 2021 and will be tested in a flight test in March 2022. In the wind tunnel test the sensor was able to detect an ice accretion on the clean airfoil with minor delay. The presentation will also provide preliminary results from the flight test.