A lamb wave-based icing sensor for aircraft ice detection

Abstract

Ice accretion is a still an issue in modern aviation since icing meteorological conditions can occur within the flight. If an aircraft hits such conditions, the amount of ice accreting on the airplane can have substantial influence on weight and loss of aerodynamic performance, which may be even fatal. Especially supercooled large droplet (SLD) icing is critical due to a high accretion rate and the risk of runback ice on the airfoil. Until now, aircraft are losing control due to severe icing, which is not recognized fast enough by the pilots to react either by activating ice protection or by leaving the icing conditions instantly. To ensure fast reactions, a sensor would be helpful to detect ice accretion on susceptible surfaces, such as leading edges of wings and empennage of aircraft. This would not only enable fast detection of severe icing, but also allow to use thermal anti-icing systems only then when it is really necessary. Due to the high power consumption of such systems, this may lead to fuel saving. Within the EU project SENS4ICE, such a sensor has been developed and tested by the German Aerospace Center (DLR). It uses travelling ultrasonic lamb waves, which are sent though the structure, which is prone to ice accretion. The presence of ice alters the waveguide behaviour of the underlying structure, which can be detected. In the project, a sensor design is developed, prototypes are built and finally tested in an icing wind tunnel experiment. This paper will provide an overview about the measurement principle, the sensor design and present some wind tunnel results. It could be shown, that ice accretion is detectable with very short delay time when happening on a clean airfoil.