Airworthiness certification technology of normal aircraft natural icing flight test

When applying for Flight in Known Icing (FIKI), civil aircraft should demonstrate compliance with the requirements of de-ice and anti-ice related airworthiness regulations. Thereinto, natural icing flight test is a critical item which must be completed. Taking natural icing flight test of Y12F aircraft as an example, based on guidance documents issued by Civil Aviation Administration of China (CAAC) and Federal Aviation Administration (FAA) for FIKI and combined with the airworthiness certification process of natural icing flight test of Y12F aircraft, this paper analyzes and summarizes the airworthiness certification requirements and critical techniques of the de-ice and anti-ice system, the test instrument and installation, flight test airspace, icing atmospheric conditions, flight test items, flight test status, flight test procedures, flight test results and analysis, ice detection, icing atmospheric detection, icing accumulation state monitoring, etc. This paper also elaborates the classification of problems discovered during the flight test, the corresponding solutions, design improvement proposals, and completed supplementary certification work. Concurrently certificated by CAAC and FAA, Y12F aircraft obtained approval for FIKI from both authorities. The constructed airworthiness certification method for natural icing flight test has become an important practical guidance material for FIKI airworthiness certification.