Measurement of optical diffusion properties of ice for direct detection ice accretion sensors

Abstract

In certain atmospheric and flying conditions, ice can accrete rapidly on the surfaces of aircraft, which can significantly affect its aerodynamic performance and handling qualities. Concern over this important but largely underrated safety issue has been growing in recent years due to a number of unexplained losses of aircraft which were cleared to fly in icing conditions. Ice detection technology has changed very little over the last 30 years, relying on indirect methods based on measurements of ambient air temperature and liquid water content to determine icing conditions. This paper postulates a novel approach to direct detection of ice type and its thickness, based on optical diffusion of light in the ice volume. Experiments used fibre optics to obtain the optical characteristics of ice grown on an aerofoil, in an icing wind tunnel, and the encouraging initial results of this work are presented and discussed.