People’s Daily Online, Beijing, December 9 (Reporter Yang Yubolo) On December 9, 2022, the world’s first domestic C919 aircraft numbered B-919A was officially delivered to China Eastern Airlines.
According to the introduction of China Meteorological Bureau, in the face of blank fields and technology monopoly, meteorologists have repeatedly broken technical barriers and constantly explored weather support technology for flight test, thus escorting the journey of airworthiness and evidence collection of domestic large aircraft.
On May 5, 2017, with the roar of the engine, the domestic large plane C919 took off at Shanghai Pudong International Airport and rushed into the sky. This is the successful first flight of domestic large aircraft C919.
According to Li Boping, the head of the flight test meteorological support team of Shanghai Meteorological Bureau, the morning of the first flight was overcast, and the flight test meteorological support team, which was jointly composed of the meteorological department and Commercial Aircraft Corporation of China (hereinafter referred to as "Comac"), accurately captured the "good weather" window of two hours under adverse weather conditions, and successfully ensured the C919 to safely perform its first flight mission.
The success of meteorological support for the first flight is only the beginning. Li Boping said that the first flight of a new aircraft needs harsh "good weather", while the flight test around airworthiness certification needs to find "bad weather" under extreme meteorological conditions. Before officially entering the market, the aircraft must pass a series of test flights and obtain airworthiness certificates. Testing and inspection in "bad weather" such as crosswind, high temperature, high humidity, cold and natural icing are all important tests in the airworthiness certification of aircraft, and targeted meteorological support services are urgently needed.
Due to the late start of China’s civil aircraft business, excessive dependence on foreign technology has made it very passive for domestic large aircraft to obtain evidence, so it is urgent to "localize" the weather support service for test flight. Since 2014, focusing on the flight test demand of domestic large aircraft, Shanghai Meteorological Department has stepped forward, actively docked Comac and China Flight Test Research Institute, established the first professional flight test meteorological service support team in China, and started the dream-seeking journey of "localization" of flight test meteorological support.
In the past five years, the flight test meteorological support team has continuously broken through the "stuck neck" technology, and provided several flight test meteorological support services for ARJ21 and C919 models, covering flight test subjects such as natural icing, strong crosswind, high temperature, high temperature and humidity, and extreme cold, as well as routine flight test activities such as first flight and transition, and accurately monitoring and accurately predicting key weather safety conditions such as visibility, strong wind, clouds, precipitation and bumps.
Natural icing flight test is one of the most difficult subjects, which requires extremely strict requirements on the liquid water content of clouds, the diameter of water droplets in clouds and the temperature of surrounding air. Once, in order to complete the test flight of natural icing, the ARJ-21 plane searched in Urumqi for four years without success, and finally went to Wan Li in North America to search for ice.
"Although the information and methods available for reference in China are almost blank, we always believe that clouds that meet the conditions of natural icing flight test can be found in China!" According to Li Baiping’s memory, at first, the team started with a large number of domestic and foreign natural icing forecasting methods and learned the forecasting algorithm of foreign aircraft icing meteorological conditions. The method is available, but it is "acclimatized" when applied to domestic flight test.
It is urgent to verify and optimize the algorithm. In order to obtain a large number of observation data and repeatedly test the algorithm, the flight test meteorological support team took the initiative to enter the icing area to test the flight. Since 2016, it has carried out comprehensive aircraft icing detection tests in Anqing, Anhui, Yichang, Hubei and Shaanxi. At the beginning of 2021, the team conducted long-term tracking and forecasting for four key natural icing target areas in China, sampled cloud physical parameters such as supercooled water and icing, and successfully collected a large number of experimental data and materials, which laid the foundation for preparing for the natural icing test flight of C919 large passenger aircraft.
The flight test meteorological support team carefully compared the prediction results and test data one by one based on the algorithm, and based on the technical advantages of China Meteorological Bureau’s Shanghai numerical forecast model system, developed a new method for forecasting the natural icing potential for large aircraft flight test, gradually formed an autonomous and controllable meteorological service capability for the whole process of aircraft icing flight test, and finally effectively reduced the probability of empty reports.
The breakthrough of technical bottleneck and the autonomy of support ability have given the flight test meteorological support team confidence and laid a solid foundation for the ultimate success of natural icing flight test.
On February 17th this year, C919 completed the natural icing test flight over Yanliang, Shaanxi Province, achieving a "zero breakthrough" in completing the natural icing test flight of aircraft in China according to airworthiness standards, and taking an important step towards airworthiness forensics.
The success of this test flight is the result of the continuous accumulation of countless people over the years, and there is also a strong support provided by the meteorological service process of aircraft icing test flight combining "trend pre-diagnosis" and "proximity diagnosis".
As early as mid-January, the flight test meteorological support team started the "trend pre-diagnosis", obtained a series of natural icing forecast products in the short to medium term based on the numerical forecast system, and gave the forecast opinion that "from January 20 to 28, Shaanxi will experience a large-scale rain and snow weather process" one week in advance, capturing a precious meteorological "window". Three days before the test flight, the team provided a more detailed weather forecast to provide decision-making basis for large aircraft to apply for test flight airspace and test flight time.
The weather process is always evolving. When the time of flight test approaches, "proximity diagnosis" will be started immediately. On the day of the test flight, everyone held their breath. The test flight support team closely tracked the weather changes by using multi-source observation data such as satellite cloud images, weather radar and sounding station data, adjusted the forecast conclusions in time, and kept close communication with the test flight site to guide the aircraft into the frozen clouds in time.
The results show that the predicted icing condition is basically consistent with the actual detection.
With the concerted efforts of all parties, as of February 17, the flight test support team had carried out a total of 5 flight tests and crossed the clouds 29 times, successfully capturing the icing weather that met the requirements of the regulations.
