Yang Weining paused and continued: "Butcher, you must also know that since the aviation industry entered the jet age, with the increase in the flight speed of aircraft, the harm of birds to flight has become more and more prominent. According to the statistics of www.biquge.info the US Air Force, from 1956 to 1973, military aircraft engines were hit 112 times, and 77 of them were completely damaged because of the bird collisions. For example, in 1975, a DC-10 civil aircraft took off and crashed in New York, colliding with a group of birds weighing about 1.82 kilograms, causing damage to all the fan blades of the CF6 engine, and rubbing against the epoxy resin screen, resulting in a fire and explosion. In 1975, about 42 percent of the 129 incidents that resulted in air stops were caused by engine rotor strikes by birds. From this, it can be seen how much bird strikes pose a threat to the flight safety of aircraft. ”

"Foreign countries have been studying birds hitting aircraft since 1941, and the requirements are clearly put forward in the acceptance specifications in the early seventies, and now the military specifications used by the American aviation industry MIL-E5007D "General Specifications for Aviation Turbojet and Turbofan Engines", MIL-E-8593A "General Specifications for Aviation Turboprops and Turboshaft Engines" and the engine parts of the airworthiness regulations of civil aircraft in various countries, such as ICAO of the International Civil Aviation Organization and FAR33 of the United States. The UK's BCARC and the European Community's JARE have made strict requirements for aero engine bird swallowing tests. ”

I don't know when, the engineers of the 132 factory in the hangar gathered around one by one to listen to Yang Weining's introduction to the bird-swallowing test.

Although these are all things that have matured abroad for more than ten years, they are all unheard of concepts for them.

Although some people wondered where Yang Weining learned these things, at this time, everyone did not speak, and listened to Yang Weining's speech seriously one by one.

In the history of previous lives, the concept of the engine swallowing bird test was not accepted by engineers in China's aviation industry until after 1984, and it was not until the mid-to-late eighties that it was popularized on a large scale.

This time, Yang Weining can be regarded as popularizing some common sense of the bird-swallowing test to Chinese aeronautical engineers in advance.

Tu Kai said: "Xiao Yang, then can you tell me about the specific experimental method of this bird-swallowing experiment?"

Yang Weining nodded and said with a smile: "These are all things I have seen from foreign English literature, and I only know a rough idea." The specific requirements for the swallowing bird test are different from the military regulations of various countries and the airworthiness regulations of the engines used, which are determined according to the situation of the aero engines in each country and the conditions of use of different models. However, the basic content includes the weight and density of the bird, the speed at which the bird is thrown, and the state of the engine. ”

"For example, in the US military norms, they divide birds into three categories by weight: large birds (more than 2,000 grams), medium birds (about 1,000 grams) and small birds (50 to 1,000 grams). The impact momentum of the big bird is large, and the structural strength of the components is mainly assessed, and the middle bird and the small bird are mostly flocks of birds hitting the engine, so in addition to the structural strength of the components, due to the large impact area of the birds, it is also necessary to assess the instantaneous thrust loss of the engine when swallowing the bird, and whether the compressor stalls and surges and causes the engine to stop in the air. ”

"In addition, because the cruising altitude of modern jetliners is generally above 8,000 meters, few birds can fly so high in the air, so engine bird swallowing accidents generally occur at low and medium altitudes, especially near airports, that is, during the take-off and landing of aircraft. Because the angle of attack of the aircraft during take-off is very large, the speed is not fast, the altitude is not high, the engine needs to be in the maximum thrust state to maintain a stable flight attitude, at this time, once the thrust of the engine decreases because of the bird strike, even if it is only a dozen seconds, it will cause serious consequences. ”

"Therefore, the engine should generally be at maximum thrust during the bird strike test to simulate take-off, and birds of different sizes need to be fired in different radial positions, from the center of the engine axis to the outside of the engine casing, to simulate the actual bird strike situation. During the test, in addition to recording the impact process with a high-speed camera, it is also necessary to record the changes of engine parameters during the whole test process, and decompose the engine after the test, analyze the consequences of bird strikes and the structural deformation of various components (especially fan blades), so as to provide a basis for evaluating the structural integrity of the engine and improving the design. ”

"The bird strike test can be carried out on a pit tester or on a ground explosion-proof tester, but if it is used as a research test, it is more economical to carry out it on a pit tester with a first-class N-class blade or a single blade, and to provide empirical data for scientific research for the whole machine test. At present, with the introduction of Spey MK202 engine-related equipment in China, it has initially met the conditions for pit testing, but if you want to carry out bird strike tests on a large scale, you need to further improve the relevant technologies and specifications. ”

……

More than half an hour passed unconsciously, and everyone was originally restoring the accident process of Jianjiao-5, but it was interrupted by Yang Weining, and it directly became a popular science course for the aero-engine bird swallowing test.

Fortunately, in the previous life, China's aero engine bird swallowing test was carried out very perfectly, Yang Weining was well-informed, and had a very deep understanding of the history and specific details of the bird swallowing test.

At the end, Tu Kai patted Yang Weining's shoulder and said with a wry smile: "Listening to your words is better than reading for ten years." Xiao Yang, if you have any ideas in the future, you must talk to us old men more, if you don't mention it today, I'm afraid we aviation people don't know when we will hear about the bird swallowing test. By the way, if you have time, write me a review of the bird swallowing test as soon as possible, and publish it in Aviation Standardization and Quality when the time comes. In addition, I will contact the 603 Institute, which introduced the Spey engine, and it happens to carry out the bird-swallowing test through their equipment. Our country's aviation people have been working behind closed doors for too long, and it is really necessary to open their eyes and see more of the outside world. ”

"Okay, butcher. ”

Yang Weining smiled and nodded in agreement, although the bird swallowing test could not improve the design and manufacturing level of China's aero engines, but it was of great significance to flight safety, and he was naturally obliged.