The Research On Select The Airspace Of Aircraft Nature Icing Test

Aircraft icing are a serious threat to the safety of flight, aircraft before being put into operation must meet the regulations of aircraft flight test and have the required performance, and can run safely under icing conditions, as well as obtain a variety of certification including aircraft natural icing test flight safety certification, including aircraft natural icing flight test safety certification, a certification. So aircraft natural icing flight test work is a important project. The key of aircraft natural icing flight test is to find a desired airspace which can used to aircraft natural icing flight test, the ideal airspace should be a vast and have high relative humidity airspace. Besides, the ability of predict the icing condition weather is also important, so that can provide convenience and reduce the time for aircraft natural icing test of new model aircraft.This paper summarizes a variety of domestic and foreign aircraft icing algorithms and indexes, choose two high performance icing algorithm and icing index, they are the improved Ic icing algorithm and SCEM (VV) icing index. Then use the NCEP data to analysis the aircraft icing cases, and to find which icing algorithm is more excellent. Firstly, analysis of case in large scale synoptic situation, and analysis various weather physical characteristics, to find out the reasons of generating icing condition weather, and the common characteristics of aircraft icing meteorological elements. Through MATLAB software use the two icing algorithms that mentioned before to drawing the icing area, observe the painted icing area whether cover the icing position that reported from the aircraft icing case, comparison the accuracy of two kinds of icing algorithms, find out the conclusion of Ic algorithm is more accurate. In addition, through the analysis of aircraft icing case, also find out that the air upward vertical movement can improve icing strength, but not the necessary conditions of aircraft icing.Drawn from the analysis of the aircraft icing case, icing area usually at the edge of cold and warm air masses, and nearby the zero isotherm area, especially, the temperature is below zero degree and higher than-10degrees, as well as the relative humidity is very high, in these region, atmospheric temperature change is fast, often appear frontal surface, so that the airspace have the possible of producing aircraft icing. In addition, the emergence of aircraft icing also have relationship with the atmospheric convergence movement and water vapor polymerization. Through the statistics of China’s50years of daily mean meteorological reanalysis data, calculate the distribution of icing frequency value at different layer height. In this paper, the frequency value of aircraft icing which reached30%are regard as the icing area, the overall situation of the icing area distribution is in our country, in winter, the icing area are located in Yangtze River to the south of the vast Yangtze River Basin, the highest frequency region are often located in the Sichuan Basin, another icing area which have high icing frequency area are located in Northern Xinjiang province. With the passage of time, ground temperature gradually increased, the level of have high icing frequency area are become more and more high, in summer, below the700hPa height layer almost no obvious icing area, at600hPa height level, icing area mainly distributed in the north of35°N, at500hPa height level, it was mainly distributed in the south of35°N. In our country, the icing area is mainly affected by the cold and worm air mass interaction, changes with the change of season, and move between North and South in regular. General rule is, in Dec, Jan, Feb, Mar (winter half year),icing area is located in850hPa and in Northern Xinjiang province, in700hPa height level, it is in the Yangtze River and to the south of Yangtze River regions; In Mar, Apr, May, June, icing area appear in600hPa height level of the Yangtze River Basin. From the beginning of May, in500hPa height level, the Tibetan Plateau area started appear icing area; In Jun, Jul, Aug, Sept, in500hPa height level, the Qinghai Tibet Plateau is the center of icing frequency and these area’s icing frequency was the highest, all the region cover the widest range, from the beginning of September, High Frequency icing area began to appear in north China, in700hPa height layer, in the north China, appeared high frequency of icing area again; in October, there is no obvious icing area; in November, again in the northern Xinjiang area, icing frequency is higher than30%again.