Flight tests of a digital data acquisition system for analysis of ultrasonic pulse-echo signals used to measure ice accretion

Abstract

A number of signal processing algorithms were developed for analyzing ultrasonic signals used to measure aircraft ice accretion in flight. A high speed digital signal acquisition system was designed and constructed to acquire the signals. The ultrasonic signals were acquired during a series of flight tests in actual icing conditions. This digital data was used to evaluate various algorithms for determining the ice thickness. An analog data acquisition system provided data for comparison with the digital data. A gated peak detector, employing low signal to noise ratio filtering and derivative preprocessing, was developed. This algorithm correctly determined the ice thickness for all tested flight data. Icing rate algorithms were also developed. The measured icing rate correlated reasonable well with the liquid water content of the cloud.