Half a month later.

Nanzheng, on the 182 factory Liulin Airport under a clear sky.

Two propeller planes, one large and one small, are parked at the end of the take-off runway, waiting for the meteorological conditions to meet the requirements of the test.

Naturally, they are the Y-8F that has been refitted, and the MA60 prototype that was transferred from Hokyo a week ago.

On their wings and tails, red, black and yellow ice thickness scales have been drawn -

In the case of insufficient accuracy of ice detectors, data can only be obtained by video and high-speed camera capture.

Under the leadership of Chang Haonan and Lin Guofan, the 182 factory and the School of Atmospheric Sciences of Jincheng University have exploded into amazing work efficiency.

The former has moved Chang Haonan's calculation of the key regional de-icing system from the drawings to reality in just over a dozen days, while the latter has set up special meteorological monitoring and control stations in Jincheng, Qinling and northern Xinjiang – according to the experience of the past few decades, the above places are statistically the places with the highest frequency of ice accumulation in the whole of China.

However, a group of people waited for a few days, and the entire northwest was cloudless and good.

Under normal circumstances, this is the most suitable climatic condition for flying, but the natural icing test flight is to "face the difficulties", and if there are no difficulties, we must create difficulties, and the current environment is a little faceless.

"Everyone, check the functionality of all the aircraft's anti-icing systems again!"

Liang Shaoxiu held a big horn in his hand and shouted to the staff on the other side of the plane.

"Mr. Liang, I have checked it three times today, especially the hot gas de-icing system, and the frequent start of the engine will also affect the life of the ......"

The deputy next to him reminded in a low voice with black lines all over his head.

Before conducting a true natural icing test, the aircraft first needs to verify the functional, safety and performance characteristics of each anti-icing system in dry air, according to the validation criteria developed by Chang Haonan and Lin Guofan, among others.

But because it's been sunny lately, this process has been going on too many times.

"It's okay, it's foolproof, and there won't be a mistake in checking it a few more times."

In fact, Liang Shaoxiu himself knows that doing this will not have any practical effect, but if everyone is idle all the time, it will breed anxiety or slackness, so it is better to find something to do and exercise your body.

"Chang Gong, in fact, according to our previous experience in going to North America to do icing test flights, it is difficult to accurately analyze the characteristics of clouds in the airspace above 1,000 meters by relying on ground weather stations alone, and it is best to have a meteorological detection aircraft to find a suitable test airspace in the sky."

An engineer seconded from the 602 Institute next to him said next to Chang Haonan.

The latter rolled his eyes:

"The truth is this, but if you want to modify a meteorological detection aircraft, you need to pass the natural icing test first, and in order to pass the natural icing test, you need a meteorological detection aircraft......"

The engineer scratched his head and said nothing more.

"It's hard to get started......"

Chang Haonan changed his posture, put his two hands in his sleeves, and looked at the sky at an angle of 45 degrees and sighed.

At this time, a piece of English with a thick Italian accent came from the side:

"My friends, aren't you really joking with me when you do natural freezing experiments in this place 1,500 kilometers from the coastline and without a large water system?"

The speaker was a tall, thin Italian named Rossi Colombo, the head of the delegation sent by Agusta to follow up on the airworthiness certification.

It's no wonder that he thinks so, the natural environment of southern Shaanxi and the great northwest is indeed slightly different from the Great Lakes region of North America.

Seeing that someone questioned his professional ability, Lin Guofan, who originally had a soft personality, immediately became furious:

"Of course, according to my research in the past ten years, from November to December every year, the frequency of ice accumulation in the airspace of Qinling and northern Xinjiang is more than 50%, Mr. Colombo, you have to learn to be patient, be patient!"

Obviously, everyone was anxious because they couldn't conduct the experiment for many days on end.

Looking at the two people who were already arguing a little angry, Chang Haonan hurriedly played a round in the middle:

"Professor Lin, don't worry, when we find the icy weather, everything will be clear, Mr. Colombo is not a stubborn person, don't you see he has already changed his clothes."

This sentence is said in English, so Colombo next to it can also understand -

When he first arrived in Nanzheng a few days ago, the guy wore a stiff plush suit and insisted it was part of his professional image.

But within two days, he honestly put on a padded jacket with the logo of the aviation industry.

Now he can learn from Chang Haonan very skillfully and put his hands together to keep warm.

Colombo looked down at his cotton clothes, cotton pants, and cotton shoes, and opened his mouth to say nothing.

As the bickering of several people came to an end, the atmosphere around the runway became dull and boring again.

At this moment, a rustling sound suddenly came from the walkie-talkie on a table next to him, which immediately attracted the attention of almost everyone.

This old-fashioned analog walkie-talkie has poor signal transmission stability, and you have to wait a while to hear what the other side is saying after being turned on.

“…… The Qinling Meteorological Station reported that at an altitude of 1200-1500m, it was found that icy clouds that may meet the conditions were forming, and the airspace range was composed of the following five coordinate points: 106.108E, 32.473N, 105.906E, 32.459N......"

Lin Guofan grabbed the pen and paper on the table next to him, wrote down a few of the most important data, and then quickly gave his judgment:

"The airspace is about 12,000 square kilometers, but judging from the speed of cloud formation, the window of time left for us is not very long, and it may only be enough for one round of test flights."

The best meteorological conditions for natural icing tests are "snow in the sky", so if the clouds are too thick or the temperature is too low and the snow has already started, it will not be suitable for test flights.

The crowd looked at each other, and finally set their eyes on Chang Haonan:

"Comrade Xiao Chang, let's decide, do you want to let Yun 8 go first, or Xinzhou 60 go first?"

"Since the airspace is large enough and the time is short, there is no need to divide the order, so I think it is better to have two planes test fly together, so that the possibility of successfully collecting data is also greater."

The responsible comrades of the 603 Institute and Liang Shaoxiu from the 182 factory glanced at each other, and then nodded at the same time:

"Okay, let's test fly together!"

Lin Guofan next to him also raised his head at this time:

"I've heard comrades who have been to the United States say that they will be equipped with random meteorological engineers to make specific decisions according to the actual situation after the plane arrives in the predetermined airspace?"

The engineer from Institute 602 was stunned for a moment, and then nodded:

"That's right, the flexibility and judgment accuracy of the ground monitoring mode are not enough, so it will be much more efficient for meteorological engineers to fly with the aircraft."

Speaking of which, he hesitated again:

"But to be honest, the FAA made this configuration based on their in-depth understanding of the meteorological conditions in the Great Lakes region, as well as more than a decade of experience, and our natural icing experiments have only just begun, and the safety aspect is ......."

Lin Guofan waved his hand and directly interrupted the other party's worries:

"Yu Li, the meteorological conditions in the Great Lakes region, the FAA has been tracking for more than ten years, and I have also tracked the meteorological conditions in the Qinling Mountains for more than ten years. Because our natural icing experiments are just getting started, we need to take some risks to speed up the experiments. ”

"Yu Qing, I am also involved in the design of the de-icing system of the Yun-8 aircraft throughout the whole process, and I can go to the sky together, which can also give more confidence to the crew members who participated in the test flight, Comrade Xiao Chang and Comrade Xiao Liang are engaged in aircraft design, and Zhu Lan is engaged in surface physics, rather than letting them increase the risk in vain, it is better to let me go up, and it can also play some use."

"I've made up my mind about this matter, so I don't need to mention it again."

At this time, Colombo, who was at a loss, learned what was happening through an interpreter.

After a short period of astonishment and the embarrassment of being slapped in the face, he also hurriedly strode over with meteors:

"I'm going to get on the plane too!"

"You?"

Chang Haonan and Liang Shaoxiu turned their heads to look at Colombo.

Although the latter, as a partner, representing Agusta, was allowed to take off with the aircraft, the natural icing test was one of only three Category I risk subjects, and one less person in the sky was one less risk.

"Don't worry, I have followed the A109 helicopter to do natural icing tests, experienced!"

Colombo patted his chest and promised:

"Moreover, according to the contract, I must follow all the test flight projects throughout the whole process in order to get the full bonus given to me by the headquarters."

……

After determining the crew members of each aircraft, the two planes, which had already completed their pre-flight preparations, took off one after the other under the command of the tower.

The Qinling area is not far from Nanzheng, so not long after Chang Haonan and the others returned to the tower, they received a report that two planes had entered the airspace for test flights:

"It was found that there were large-scale stratus clouds in the airspace, and the weather conditions above the stratus clouds were fine, which met the basic conditions for icing test flights."

The tower commander began to give instructions one by one in accordance with the requirements of the test flight manual in front of him:

"Check that the test equipment is working."

Soon the pilot's clear voice was heard on the radio:

"Report 01, all test equipment is working fine."

"Report 02, all test equipment is working properly."

"Turn on the atmospheric parameter detector."

"Checking atmospheric parameters"

“……”

This time the interval between receiving responses is slightly longer:

"The cloud top height is 1800, the atmospheric liquid water content is 0.7g/m, and the average diameter of supercooled droplets is 35 microns, which meets the requirements of continuous maximum icing test, and the cloud vertical detection is requested."

"Request approval."

Due to the lack of satellite communication, the quality of the call between the crew and the tower will drop sharply after the plane enters the clouds rich in water vapor, and Chang Haonan and they can only hear the murmur of stinging and stinging.

The vertical detection of the cloud requires the aircraft to enter the cloud from above the cloud, descend to the bottom of the cloud and then climb out of the cloud, record the change of liquid water content in the cloud during the vertical altitude change, and determine which height is the most suitable for the test, the whole process will only last about 2 minutes, and the anti-de-icing system will be turned on throughout the whole process, which will theoretically not affect flight safety.

Still, not being able to maintain real-time contact with the aircraft was somewhat nerve-wracking.

Finally, the noise on the radio disappeared.

Lin Guofan's voice came to everyone's ears:

"The cloud base height is 1200, the atmospheric liquid water content is 4.5 g/m, and the average diameter of supercooled droplets is 105 microns."

"I plan to conduct natural icing test flights at two altitudes of 1500 and 1200, each lasting 15 minutes, corresponding to the 4th and 3rd categories of anti-icing capabilities in the airworthiness certification standards."

Obviously, he wanted to take advantage of the precious meteorological conditions that were rare in the past few months to complete all the test flight items specified in the manual at one time.

According to the interim standards formulated by Chang Haonan and Lin Guofan, the anti-icing ability of aircraft is divided into 4 categories.

Categories 1 and 2 correspond to imperfect anti-icing capabilities, and flights are only allowed if the weather is good and there is no risk of ice accumulation or weak ice accumulation.

Category 3 corresponds to the ice accumulation in most of the airspace of the northern temperate zone, and aircraft that meet this requirement can fly safely in almost all normal climatic conditions.

Category 4 anti-icing capability is equivalent to an additional question that is only required for aircraft that are expected to be used in environments with a greater risk of ice accumulation.

The tower commander looked back at Chang Haonan, who was standing behind him.

The latter hesitated for a few seconds, then nodded.

"Test flight plan approved!"

……

After receiving the news of the approval of the plan, the two planes turned around and plunged headlong into the thick clouds.

Soon, a dense layer of ice formed on the surface of the plane, blocking everyone's view from looking outside.

Normally, aircraft avoid this obviously dangerous airspace, so it's a pretty special experience for both an engineer taking off randomly and a seasoned test pilot.

In particular, the navigator's cabin in the nose of the Y-8 has a 270° field of view completely wrapped in ice, and the navigator reports that he is in an Eskimo igloo.

But as the ice thickened and the freshness wore off, pilots began to feel that the plane was becoming more and more difficult to maneuver.

In the cabin behind, Lin Guofan was staring at the picture on the laptop screen, for fear of misreading the position of the ice thickness scale.

According to Chang Haonan's previous simulation, the ice thickness of the unprotected leading edge of the wing should reach 7cm in the normal configuration of horizontal flight, so as to meet the test standard.

"The ice condition has met the requirements, and the maneuver flight test has begun!"

Since it was impossible to communicate with the tower in the clouds, Lin Guofan could only give instructions to the two planes together.

"Wait...... This is crazy. ”

A Colombo voice was heard over the radio:

"I just saw on my computer that the water content in the outside atmosphere is already more than 4g/m! This...... This is 4 times higher than the data stipulated by the FAA! ”

"You're right, Mr. Colombo, but we're not the FAA, we're the CCAR."

Lin Guofan said into the microphone in his hand.

"But...... But why be so extreme? There is simply no such extreme situation except for a blizzard, and it would not have been possible to get a plane to take off on a blizzard day! ”

Colombo's voice trembled a little, as if he had regretted it a little at the moment.

"For safety, of course, rest assured, we have the best anti-icing system in the world to keep you safe."

"Besides, it's too late to say anything, and there's no way we're going to throw you out of the cabin."

After Lin Guofan finished speaking, he did not take Colombo again, but directly ordered:

"Begin to circle horizontally steadily."

The pilots of both aircraft carefully controlled the rudder surfaces and allowed the planes to begin a steady hover with a 40° slope to the right.

"I ...... I saw that the wings of this plane fluttered a lot, it was really ...... Is it really okay? ”

Colombo, who was in the cabin of the MA60, asked the mechanic next to him with a pale face.

The latter calmly glanced up at the screen of the other camera, and then looked back at the laptop in front of him: "It's okay, that's our active flutter control system at work." ”

"Active flutter control?"

Maybe it's because of the nervousness, or maybe it's because of the cold, Colombo today is particularly talkative: "

"Yes, it's like...... Uh, just like Active Noise Cancellation, using controllable flutter to counteract uncontrollable flutter, which is also the core technology of our MA60. Haven't you read the brochure of our plane, it's all written on it. ”

"Who's going to look at that kind of advertising thing, you're probably the first aircraft manufacturer to make a brochure and a flight manual the same thing......"

Colombo's teeth have begun to fight.

"Looks like we still have a lot to learn from you in this regard......

At the same time, Lin Guofan, who was on another plane, had already operated a high-speed camera to capture all the required footage of ice growth.

Compared with the previous computer simulation results, it is almost identical.

"Whew-"

He breathed a sigh of relief.

To say that you are not nervous about taking off with the plane must be false.

In fact, until he captured the ice accumulation situation just now, Lin Guofan found that his hands were trembling slightly.

However, the design of the aircraft anti-icing system is based on the simulation of the severity of ice accumulation at different locations, and since the simulation results are not problematic, it means that the entire de-icing device should not be problematic.

"The hovering flight roll subject is over, turn on all the de-icing systems!"

……

Since it had been nearly half an hour since the crew had not been able to get in touch, the atmosphere in the tower of Nanzheng Airport was a little anxious.

Every second is as long as an hour

It's one thing to have confidence in an anti-icing system, but not being able to hear the pilot's voice is always overwhelming.

Especially Zhu Lan, who is worried about her husband, has been standing in the corner like a sculpture for a long time.

"Unit 01 report."

The sudden and clear sound of conversation made everyone's faces happy.

"The maneuver flight test procedures under the landing configuration, the waiting mechanism type and the approach configuration have been completed, the anti-de-icing system is working normally, and it is fully in line with the test flight qualification criteria, and our two-plane formation is ready to return!"

Zhu Lan, who was leaning against the wall, suddenly relaxed, and fell directly on the sofa next to her.

Liang Shaoxiu, who has been tense for more than half a month, was also completely relieved and called the deputy next to him:

"Notify the manufacturing workshop to replace the other three Y-8Js with new anti-icing systems as soon as possible, and the finalization schedule of the equipment must not be delayed!"

Chang Haonan, on the other hand, set his sights on the direction of the assembly workshop.

There are several other Y-8F platforms waiting to be delivered.

Standing in front of the tower's floor-to-ceiling windows, he muttered in a voice that only he could hear:

"In this way, the tragedy in history should not happen again......

(End of chapter)