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

Abstract

Icing is a regular occurrence in aviation when an aircraft meets supercooled water droplets in the air. While medium to large size aircraft can mitigate icing effects by e.g. thermal ice protection systems, UAV are much more limited in this regard. The reason therefore arises from the small size and limited power supply of most UAV. Therefore identifying icing immediately before it overwhelms the performance of the aircraft is crucial which can be done with an ice accretion sensor. Such a sensor has been developed as part of the EU funded SENS4ICE project. It is based on measuring ultrasonic lamb waves traveling through the aircraft structure. An ice accretion will alter the lamb wave pattern, which can be used to detect ice. By using the aircraft structure itself as the sensitive surface, the installation space and weight of the sensor can be kept at minimum. Furthermore the ice accretion can be detected at the most sensitive locations, e.g. the leading edges of lift surfaces. In the presentation a brief overview about the sensor principle and design is given. Wind tunnel and flight test results will be presented. Especially for the flight test a small and lightweight sensor electronics unit was designed which even has the potential to be further miniaturized. It could be shown in both tests, that an ice accretion can be detected within a minor delay from entering the icing conditions.