This paper considers inflight parameter identification and icing location detection of the aircraft in a more common time-varying nature. In particular, ice accumulation is modeled as a continuous process, and the effect of the ice upon aircraft dynamics is to be accreted with time. Time-varying case of the Hinf algorithm is implemented to provide inflight estimate of aircraft dynamic parameters, and the estimated results are delivered to a probabilistic neural network to decide icing location of the aircraft; an excitation measure of the aircraft is also adopted in the network input layer. A database corresponding to different icing cases and severities was generated for the training and test of the detection network. Based on the test results, the icing detection framework presented in this paper is believed to be with promising applicableness for our further studies. 1. Introduction Current aviation research and development has begun to focus more on creating aircraft that are safe and reliable during severe weather conditions. Aircraft icing is of great concern due to the detrimental effect of accreted ice on aircraft performances. Most of the accidents related with aircraft icing occur because the ice accumulation modifies the stability and controllability of the aircraft [1, 2]; other accidents include engine failure or critical probes (pitot tube, etc.) malfunctioning [3, 4]. Currently there are two main approaches to deal with the ice accretion problem. First, pilots are provided with weather information prior to flight missions in the pursuit of avoiding potential icing conditions or aircraft are thoroughly deiced before takeoff, while an icing protection system (IPS) could be operated in flight to remove dangerous ice accretions. Under all circumstances, apparently ice avoidance is a more desirable goal. For most of the commercial flight courses, however, while revenues and schedules must be maintained, IPS still occupies an important part in the insurance of safe flight. Current IPS mainly consists of devices that could bleed hot engine exhaust to counteract the frigid icing conditions, or inflatable boots are used to break off the accumulated ice. Generally the IPS functions in an either advisory or primary capacity. The advisory IPS relies upon pilots to activate icing protection devices based on any aircraft icing information, which might be allocated from icing/environmental sensors. As for IPS that functions in the primary capacity, it utilizes the information collected from various sensors, and the deice/anti-ice devices are activated
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