Early warning and thickness measurement of aircraft icing using ultrasonic pulse echoes

Abstract

The accumulation of ice in critical regions on the surfaces of modern aircraft is a serious threat to flight safety, and so for aircraft to be able to fly safely in all weathers, they must be capable of reliable early warning of icing and online measurement of ice thickness. In this paper, an ultrasonic pulse-echo technique combined with signal processing is proposed for icing early warning and ice-thickness measurement. The early-warning sensitivity and ice-thickness measurement ability are verified through both simulations and experiments. The simulation results show that (i) the proposed signal processing method can identify ice and water effectively and (ii) the minimum icing warning and precise measurement thickness of the ice layer decrease with increasing center frequency of the excitation pulse; for a given center frequency, the icing-warning thickness is approximately a third of the initially measured ice thickness. The experimental results show that a probe-type sensor with a center frequency of 7.5 MHz can measure 0.24-mm-thick ice, and the early-warning time is 8.5 s ahead of the accurate measurement time. A flush-mounted sensor cannot measure the ice thickness because of the roughness of the ice surface, but it can still provide early warning of icing.