Abstract:

The Supercooled Large Droplet （SLD） environment is a common icing condition， causing many air accidents and drawing extensive attention because of the abnormal icing and rapid crash. Over the past two decades， considerable research has been carried out on its icing mechanism， simulation methods and test technologies. However， little progress has been achieved on the icing protection and airworthiness certification. The SLD icing airworthiness requirement is a major challenge for large civil aircraft of China. More importantly， the question whether strict airworthiness requirements impact the operation capacity of aircraft has not been explored. This paper introduces the progress of icing mechanisms， numerical technologies， ice risk assessment and anti-icing methods from basic research to engineering applications. Then the aircraft icing protection design and operation strategy are discussed. It is concluded that the safety design of aircraft under the SLD icing condition has high risks and costs due to the immature SLD icing safety technologies such as the icing numerical/experimental simulation， icing conditions sensing， and the high-efficiency anti-icing. Improvements only in the anti-icing capability will have a low benefit. Instead， the ability of icing detection and icing condition detection， targeted icing protection and icing tolerance needs to be enhanced. Therefore， it is necessary to make breakthroughs in the techniques of accurate icing protection， accurate icing detection and experimental simulation of supercooled large water droplets， while these breakthroughs depend on the development of fundamental research such as simulation of supercooled large droplets conditions and the runback icing mechanism.

Key words: Supercooled Large Droplets (SLD), abnormal icing, icing protection, airworthiness certification, operation efficiency