Why did Yun 20 build C9 19?

Finally, the domestic large plane C9 19 successfully made its first flight!

But the first flight is just the beginning. The so-called first flight is the first test flight, followed by the second, third or even nth test flight. Few people know how many more difficult challenges the big plane will face in the next test flight.

Today, I pushed an old article, which recorded in detail the story of ARJ2 1, also a domestic aircraft, and the details of various test flights it experienced after its first flight, "Try the danger". These experiences are likely to be staged in the future C9 19.

There is a high mountain at 10 km ahead, but the plane is still moving at a speed of 450 km/h. If the direction is not changed, as long as 1 min is 20 seconds, the plane will hit the mountain and kill people.

The alarm goes off, 10 seconds, 9 seconds, 8 seconds ... "Pull up! Change one! " This behemoth made of steel suddenly raised its head and abruptly climbed up. In the last few seconds, the plane almost passed the top of the mountain, and the nearest distance from the mountain was only 30 meters. For aircraft with a wingspan of less than 30 meters, this has reached the limit.

False alarm!

From the appearance, this plane is no different from an ordinary passenger plane, but the test cabinet in the engine room still reveals that it is a prototype for flight test-China's first civil regional plane with independent intellectual property rights, ARJ2 1 (the first flight test of ARJ2 1, and then the flight test is today's big plane C9 19, editor's note 2065438+20. This scene just now is exactly what they did in the test flight of terrain early warning system verification.

Many people are no strangers to test pilots, but the test flight engineers who stand behind them and silently command the experimental tasks and shoulder all the potential risks with them rarely enter the public eye. Recently (one day in 20 13, editor's note), a reporter from China Youth Daily approached the team of Comac China Flight Test Center stationed in Yanliang, Shaanxi, and experienced this group and their working process from a distance.

Take an unpredictable adventure trip.

Exploring the most dangerous points in flight is an important task for these flight test engineers. Stall, 27 knots crosswind, engine flameout, rudder jam, etc. These dangers, which usually sound creepy, and the small probability events that only happen once every tens of thousands of flight hours in aviation history are all they often have to face and deal with.

Liu Lisu's face turned white the first time he felt his nose "fall off", although the flight test engineer had passed a heavy "psychological test" before.

Even if an ordinary civil aviation plane approaches stall and hears the alarm that "the crew will be fined", what Liu Lisu and his partner Zhang Dawei have to do is to turn off the stall protection system and let the plane enter a natural stall state. "Let the lift of the plane suddenly lose." Zhang Dawei said.

To understand the stall, we must first understand "what makes the plane float in the air". This seemingly simple question is often misunderstood. In the words of Wang Hucheng, a flight test engineer, "Many people think that airplanes fly in the air by engines, and this idea is only half right, because engines only provide the forward thrust of airplanes." So what is the force that makes it float?

Engineering male, who loves animation in this team, made an interesting analogy. "The civil aviation plane we usually take is neither tinker bell nor astro boy. The former is a rotorcraft and the latter is a rocket. They are all straight up and down traction and recoil, while the plane relies on lift. "

Specifically, the lift force depends on the design of the aircraft wing itself, so that the airflow speed on the upper and lower wings of the aircraft is different during the movement, and the lift force is generated through the pressure difference between the upper and lower wings. When the forward speed of the aircraft increases, the pressure difference between the lower part and the upper part of the wing becomes larger and larger. When it reaches a certain level, the aircraft can "lift".

Just as one action that people can usually see the pilot do is to pull the steering column backwards, at this time the plane will fly upward, but this does not make the engine of the plane "spray downward", but increases the angle of attack and lift of the plane.

But when the elevation angle of the plane is large enough, the airflow on the wing will separate and the plane will bump. Liu Lisu on the plane had a feeling that "the whole plane stood up" and his back suddenly pressed against the seat.

Then, soon, the plane began to fall. That feeling is like "a person holding you, and suddenly, that hand is gone." If you don't change it, it means that the plane will soon go from "stall" to "rotation"-just like a paper plane thrown out, it will fly in the air for a while and then spiral down. Seen from above, its tail hovers back and forth, then falls freely, falling head down until it touches the ground.

Spin is known as the "valley of death" in the field of military aircraft. Many military aircraft once fell here and never "climbed up".

In fact, all flight test engineers have participated in the "spin" training during the training. Ling Ning recalled a detail. Before boarding the plane, the training teacher put the parachute bag into his hand and said, "Pull this if there is an accident." Then, "the teacher left." Ling Ning was at a loss holding this big guy who had only seen it on TV. "It's a psychological comfort not to tell me where to pull!" Ling Ning said.

Civil aircraft several times larger will not take this kind of "confused luck" because once they fall in, they can't "change". Therefore, every entry of flight test personnel is a challenge with "psychological pressure".

Although Liu Lisu once made a test flight and pulled the plane more than 20 meters off the ground, the degree of danger was "the plane will hit the ground in two or three seconds", but he still thought that stalling was more dangerous!

Today, he has become the newest stall owner in the team because of "flying 120 stalls a day". In Zhang Dawei's words, "always bowing, looking up, bowing, looking up ... is equivalent to riding a roller coaster for more than 120 times a day, and its uncomfortable degree can be imagined."

Try all the dangers

When Liu Lisu was "bumping" in the sky, Yin was experiencing a high-risk action like "tail wiping the ground" on the ground. The flight test engineer who insisted on boarding the plane for the longest time in the whole team only said to the reporter: "A little scared, maybe."

According to industry statistics, more than 90% of major flight accidents occur during take-off or landing. A McDonnell Douglas -82 passenger plane from lion air, Indonesia, ran off the runway when it landed at Thoreau Airport in Central Java, Indonesia, causing nearly 100 deaths and injuries.

No one dares to imagine what the ARJ2 1 weighing 40 tons and carrying nearly 100 passengers will look like once the brakes are out of control.

What Yin has to do is to minimize this possibility and verify that the plane is "still safe" in the most dangerous situation.

The reason why the tail wing is allowed to take off is to determine the minimum ground speed of the aircraft. Seen from the outside, the plane is in a backward posture. To put it bluntly, it seems that more than half of the "butt" of the plane is rubbing the ground. They installed a "tail acceleration slip regulation" and a special metal material at the tail of the plane. During the test flight, once the tail of the plane touches the ground, the sensor will immediately send a signal to the cockpit to remind the test pilot to pay attention.

After the plane began to taxi, the tail wing was splashed with sparks and a layer of steel plate with a thickness of more than 20 cm was scraped off. At this point, Yin in the cabin is still joking with the test pilot: "Dude, is your ass hot?"

People never thought that the fuel tank on the plane would be blown off by the sun? It was not until July 1996 that a TWA Boeing 747 exploded over Long Island, new york, killing 230 people, that people gradually realized this problem. After that, any new passenger plane test flight must complete the hot climate fuel test flight subject.

Of course, ARJ2 1 is no exception.

Before take-off, what Wang Hucheng has to do is to "heat" the oil in the fuel tank to 54.5℃, which is slightly higher than the scheduled 54℃, so as to ensure that the temperature of jet fuel will not cool down quickly. The "flash point" of jet fuel is 38℃, which means that as long as there is an electric spark on the plane, it may cause an explosion. In addition, he will take off immediately in this specially selected hot weather.

What still makes Luo Hailin feel a cold sweat is "single engine failure", that is, one of the two engines that should be started at the same time is turned off to see the flight state of the plane under such conditions. To put it bluntly, it is to see if the plane can "drag" the sick body back to the airport in such an emergency.

The supplier provided Luo Hailin with a theoretical envelope, and the speed and height in the envelope were safe. What he did was to verify its authenticity. For example, when the plane flies to an altitude of 5,000m, the twin-engine plane will shut down one of the engines and restart it to see if it can be restarted smoothly at high altitude. If yes, the theoretical range of the envelope is "no problem".

Under no circumstances can the engine be started, especially at high altitude. The higher the altitude, the thinner the oxygen, the less air the engine inhales and the slower the turbine speed. If there is a mountain below the plane at this time, the plane can't descend "to raise the engine temperature or inhale more air", so it probably can't start. This is similar to car engines, for example, some car engines will not start because it is too cold in winter.

The supplier said, "At an altitude of 5000 meters, you can still restart the engine without lowering the height of the plane.". What Luo Hailin has to do is fly to an altitude of 5000m to verify whether the engine can be started in this state.

For the public to "try again", there are thousands of "must do" subjects and thousands of flight tests are needed. Zhu Weidong told reporters, "The more detailed we do, the richer the sideline business involved. For the public, the safer the plane under normal flight. "

Behind-the-scenes director of aerial stage play

For flight test engineers, it is easy for laymen to confuse their identity with the engineer who designs the aircraft and the test pilot who drives and controls the aircraft.

Taking the former as an example, the designers consider "making the system I designed meet the airworthiness requirements", so in order to achieve this goal, they pay more attention to the final data rather than the specific flight process. The flight test engineer should not only obtain the data supporting verification, but also consider the factors of flight safety. After all, they are "heavenly" themselves.

Just a few days before the reporter's visit, Zhu Weidong had a disagreement with the designer in a flight test to verify the engine performance.

The designer's consideration is to make the plane fly to a certain height and push the engine thrust to the maximum to verify whether it can reach a certain maximum power, but they ignore one point: "At the maximum power, the plane is accelerating constantly, and the plane has a certain speed limit, which is not feasible in practical operation."

Zhu Weidong made a popular analogy: "It's like a car driving on an expressway with a speed limit of 65,438+020 mph. It is impossible to go from 65,438+000 to 200 at once. Take your time. When the speed is increased to 65,438+020 mph, you can't accelerate any more, otherwise you will overspeed. "

Don't simply understand the flight test engineer as an engineer standing on the plane. In an outfield test flight to Dongying, flight test engineer Le Yafei greatly reduced the task order of 18 to 8 sorties.

Generally speaking, a task list is a flight, and the cost of a flight is 200 thousand. If measured from the perspective of cost saving, this is value.

Le Yafei is the only female flight test engineer in this first-line team. She is responsible for the test flight of ARJ2 1-700 aircraft 103. Gao Feisheng, who graduated from Fudan University, is full of proper terms about flight test, from task list countersigning, task coordination of related subjects, flight monitoring, post-flight evaluation, aircraft tracking plan making and flight report making.

However, all this comes down to the work of the flight test engineer, that is, in a word, "let the plane fly safely and strive to achieve some performance it should have."

This morning, Le Yafei was wearing blue overalls and holding a task list, ready to board the plane. This is the task list of the "next task" the afternoon before. All the test points that she and her plane will do today are written on this A4-sized paper. In the industry, flight test engineers refer to the standards used to test aircraft performance as "terms" and "outlines". To put it simply, the flight test of this plane can only be called complete if every item in the outline is checked.

The flight test engineer does more detailed work, so as to "not only complete the task", but also "how to complete every step of the task". It was the task list in her hand that recorded these details.

In fact, among international peers, the flight test engineer is regarded as the soul of flight test, and the test pilot performs the actions in the flight test task list in the air. However, how and why to do this action is designed by the flight test engineer according to the airworthiness clause, aircraft body and system characteristics, fully considering the factors of flight test safety and risk reduction.

In the United States, half of the test pilots are selected and trained from senior flight test engineers, and these test pilots can usually become the best test pilots after flight skills training because of their solid theoretical foundation in the early stage.

"If the test pilot is compared to a dancer in the air, then the flight test engineer is the behind-the-scenes director of this aerial stage play." Le Yafei said. And the task list in her hand is her script.

Out of Mojave Desert and Ostrich Capital

Since 20 10, China Comac has sent 34 technicians to participate in the professional flight test engineer training in 1 0, and the cost per person is about 3.5 million RMB. There are two locations, one is Auden, the ostrich capital of South Africa, and the other is Mojave Aviation Base in California, USA.

"Out of Amazon", when Wang Junjie first heard of this "heavily invested talent plan", the name of the film popped up in his mind. The thought of the hero in the movie training special movements in the stormy playground in the extreme weather makes him excited.

When Wang Junjie really stood at the airport more than ten kilometers away from downtown Orton, he saw that the airport runway was full of "grotesque" retired planes, such as 707, 747 and F4 ghosts, and those "flying shows" that he had never seen before, such as flying low on the lake and "drawing big circles in the sky", he found that all this was almost exactly the same as he had imagined.

The harsh natural environment surrounds the seemingly glamorous airport. In the wilderness 600 meters away from the runway, they found the best data observation point. However, the wilderness is covered with knee-deep bushes, and there is no road for driving, no place to sit and rest, and no place to shelter from the scorching sun.

In order to get the best data, they should be exposed to the scorching sun above 40℃ and stand by for at least five or six hours every day. When they successfully completed all the test tasks, the bushes that had no way out were abruptly pulled out of a path.

Soon, Wang Junjie realized the feeling that "after this special training, life can be changed".

In fact, when these people, including Wang Junjie, become one in a hundred, their careers are no longer "in line" with the previous ones. Since then, in the aviation industry of China, their business position has only one name-flight test engineer.

Just like Le Yafei, a colleague said, without this training, this girl studying aircraft design might still work in the design laboratory from nine to five like other girls in their twenties who work in Shanghai, and then she would get used to the leisurely life of shopping, singing K and playing board games after work.

Instead, she chose to rush to Mojave Aviation Base, a national test pilot college located 40 kilometers north of Lancaster, California.

The first level is four major exams: physical examination, psychological test, foreign language and theoretical basis. However, passing the physical examination of in-situ rotation and handstand does not mean that she and her teammates can "escape" the discomfort caused by real high-altitude flight in the real theoretical training and practical operation in the future.

It is an airport near the desert, and the teachers trained are basically the top pilots in the United States. Naturally, they are also very strict with their students.

Students hardly have weekends, and their lives are divided into three weeks-this division method follows the rhythm of training-which are alternately theoretical classes, exams, flights and reports. Usually, there will be three or four different courses in the first week of theoretical class, each of which is equivalent to the content of a semester in college. After studying, they will take exams. In the next two weeks, they will directly apply what they have learned to flight test terminology and actual flight, and complete all courses in the third week.

In Ling Ning's description, they live a life of "attending classes at 8 o'clock in the morning and finishing classes at 6 o'clock in the afternoon", "attending classes from Monday to Thursday and taking exams on Friday" and "only taking two days off every three weeks to catch up with the Chinese college entrance examination". The difficulty of the course is so high that even the flight test students who grew up listening to their mother tongue are struggling.

As one of the few aviation majors in the team, Le Yafei finally graduated with an average score of 90 points. But not everyone is as lucky as her. When Ling Ning saw that the first week's study task was a thick aerodynamic English textbook, the communication major boy who should be engaged in 3G felt "at a loss". He really couldn't figure out that "only relying on aerodynamics, such a simple four words explained how the plane flew".

In order to find out the parameters of an engine, he spent a whole night searching more than 200 pages on Google to find it. After returning to the dormitory, Ling Ning cooked a simple dinner and gave the rest time to "watching PPT and reviewing" and "reading and previewing".

Meanwhile, Luo Hailin and Wang Junjie, who are now quasi-flight test engineers, have just spent half a year and more than eight months studying at Orton Airport. Although these two young people, who are less than 30 years old, are "studious" and "serious" different from "local idle pilots", they are still timid in the face of the final exam.

Give you a plane and design a test flight plan! The school dragged them to Johannesburg and asked him to make a specific task list with the simulator, but it was not until the night before that the students drew lots to know what type of plane they were flying.

"I was completely shocked!" He still has a lingering fear. "A flight manual as thick as a fist should be compressed into an A4 paper every day!"

In the presentation session of the final exam, the school invited all the teachers who taught them to be judges. "You said the plan above, and the teacher below asked you like a nitpicker. This expression doesn't seem quite right. There seems to be something wrong with this. Your arm should be raised to better demonstrate ... "

Push everyone to the front desk! Luo Hailin recalled, "This is not only to exercise your expressive ability, but also to let you know that you have to bear this responsibility and stand at the front desk, just like standing on an airplane. You have to have the courage to hold up all this! "

Make an agreement with life and fight the sky with youth.

When the reporter visited, it just happened to catch up with the birthday celebration of ARJ 2 1 flight test engineer "flying time exceeds 1 1,000 hours". Five flight test engineers,,, Le Yafei, and Yin, whose personal flight time exceeds 100 hours, accepted the award certificates and spoke in turn.

At that time, they had no "Jianghu spirit" at all. Their ruddy faces and big red flowers on their chests made them look like middle school students who had just won awards.

Just two days ago, Ling Ning, who was in his early thirties, was talking about how he was inspired by his father who was a mechanic to join the team. There were six or seven model planes in his room.

The reason they gave for "choosing to enter" or "choosing to stay" was simple, "I just like it".

Many college students of Le Yafei "switched careers" to do financial work in investment banks, and only she came to an aircraft company with awe of "professionalism". She thought she liked airplanes enough, but when she met these engineering male, she found that "she didn't even know that the Russian' torpedo' without horizontal tail and vertical tail was the legendary sixth-generation fighter".

"Test pilots or flight test engineers are generally hairless or short." This is not consistent with the handsome pilot image that people usually see in film and television dramas. At the scene, the reporter also saw that many test pilots had little hair or even hair loss. A very important reason is that the radiation is very large and the hair loss is serious. Therefore, the flight test engineer has a self-deprecating metaphor that "the less hair, the higher the flying level".

This group of young people don't have much "worry" when talking about this topic, but are more joking or joking.

"I dreamed that I was bald yesterday." This is from Lai. At the flight test site of Yan Liang, he was one of the flight test engineers who could not get on the plane, and the other was Wang Junjie.

"Do you know why Prince William's hair is getting smaller every year? Always fly a plane! " Wang Junjie said.

Taking advantage of this topic, several engineering male also took the opportunity to make fun of Le Yafei, the only female flight test engineer at the front. "Although I usually feel that I don't have much hair, once the barber shop owner told me that girls don't have baldness genes, I was relieved."

Before Le Yafei's voice fell, the boys swore at him. "There will be", "There really is, women don't start balding from the top of their heads like men," and "Don't comfort yourself, I've seen women bald!"

In the year when they gradually fell in love with the post of flight test engineer, almost everyone has a lot of unknown bitterness behind them-

When a brother went out for training, the child was just born. He said that training abroad made me miss the birth of my child, and flying in other places made me miss the growth of my child.

Another brother, who has a good girlfriend, broke up with Fei because he spent too long together.

There are two "school-age" brothers who are single, but now they want to continue this state. "It's not realistic, I have to go back in a year or two. Isn't it a delay to find them here? "

This has much to do with their exile. As Luo Hailin said, when he was training abroad, China Commercial Aircraft Flight Test Center was established, and he returned to Shanghai from abroad on September 20 12, but after the National Day, Luo Hailin soon came to Xi 'an Yanliang, an aviation city. "When I returned to Shanghai on my last business trip, I realized that most people in Shanghai base camp didn't know."

"Outside is the runway. Every day at the test flight airport, listening to the plane flying in the sky, we are test flight engineers. If we are not in the nearest place to the plane, what is the point? " Zhu Weidong said.

Although they are also in the front line, he lai's work is not in the sky, but in the monitoring hall on the ground, where flight test engineers are also needed. They and design engineers should monitor the parameters of the aircraft in real time through telemetry data and monitoring software to ensure the safe completion of the test flight mission.

In fact, among the 34 flight test engineers, except 1 1, the other 23 are based in Shanghai. Of course, these 23 people are not idle. They are compiling the flight test program of C9 19 aircraft.

They all know in their hearts that both those who are in the front-line command stage and those who are still behind the scenes will become "pioneers of hardship" because of their status as the "first generation". This is a sentence from Tan Xiangsheng, deputy director of China Commercial Aircraft Flight Test Center and vice captain of An outfield test team.

Before the establishment of Comac in China, this middle-aged man with technical engineering background worked in another aviation enterprise for nearly half his life before producing two models. He told reporters, "Young people only know that it is not easy to dry the model and dry the test flight after the experience. This is a question of' paying youth'. "

Thirty-four young people with an average age of only 30 made a "deal" with the youth: here, the young people flew for 3,823 hours, there, ARJ2 1 got 252 confirmed and intended orders from 13 customers, and C9 19 also got 4,000 orders from 16 domestic and foreign users.

"Make an agreement with life and fight the sky with youth." Ma Fei said.

Text synthesis China Youth Daily Zhongqing reported Qiu online. The pictures are from CCTV and China Commercial Aircraft Flight Test Center. Wechat Editor: Qiu.