There is a range for the aircraft's center of gravity, that is, the front and rear limits of the aircraft's center of gravity. Within this range, the aircraft can have normal flight performance.

The front and rear limits of the aircraft's center of gravity are often expressed as a percentage of the distance from the center of gravity projected onto the average aerodynamic chord of the wing to the leading edge and the average aerodynamic chord length. Generally speaking, the front and rear limits of a modern passenger aircraft should be within 20%

The MAC looks like, and under normal flight conditions, the center of gravity of the aircraft should be near the center of the front and rear limits, which means there is about a 10% MAC safety margin in the front and rear.

If three average-sized flight attendants walk from one end of the plane to the other, the impact on the center of gravity shift is about 2% MAC. Then if more than ten passengers rush from the back cabin to the front cabin, the resulting center of gravity shift will be forward.

It has almost reached the limit of forward movement of the center of gravity.

In addition to the old man and his daughter who had already arrived in the front cabin, as well as more passengers in the rear cabin who were incited to follow, more than 20 passengers moved forward in a large range in almost four to five seconds, and the center of gravity of the aircraft

What if it does not exceed the forward movement limit?

Why do you have to stop check-in some time in advance when checking in? It's because of the load calculation. The distribution of seats on the plane is not randomly arranged, but carefully calculated.

This is why flight attendants do not recommend that passengers change seats randomly on an airplane under normal circumstances. One or two people are fine, but if there are more than one person, it will really affect the center of gravity of the airplane. Once the center of gravity of the airplane changes too much,

That will directly affect aircraft safety.

At this time, due to the spread of panic on the plane, a large number of passengers in the rear cabin gathered in the front cabin, causing the plane's center of gravity to move forward rapidly, and finally directly broke through the front limit of the plane's center of gravity, which in turn caused the plane to begin to deviate from the normal aircraft state.

Because the center of gravity of the aircraft is too far forward, the nose of the aircraft will uncontrollably lower. In addition, moving the center of gravity of the aircraft forward will greatly affect the longitudinal controllability of the aircraft, making the autopilot unable to prevent the aircraft's nose-down moment at all.

After the autopilot is no longer able to maintain the aircraft's status, it will naturally disconnect and return to manual control.

At that time, Xu Xian and Wang Qian were about to put on oxygen masks. In order to prevent them from wearing oxygen masks at the same time, there would be a short period of time when the plane would be unmonitored, so Wang Qian moved ahead a little while, while Xu Xian delayed a little, so that the two

The time to put on the oxygen mask can be staggered, so that the aircraft is under human surveillance at all times.

But just as Wang Qian took out the oxygen mask and was about to put it on, the plane immediately left its normal cruising attitude and began to dive downwards.

This change was even more obvious in the cockpit at the nose of the plane. Wang Qian and Xu Xian felt as if they were weightless. Their eyes gradually moved downwards as the plane pitched down. They no longer even had to lower their heads to look directly at the thunder and lightning.

at.

Xu Xian hasn't figured out what's going on yet, but that doesn't stop him from reacting to it.

The response to this situation is actually very simple, just pull the stick to prevent the aircraft from continuing to fall. The plane is not falling due to stalling. If it is falling due to stalling, then you cannot pull the stick. Instead, you must push the stick first to reduce the impact of the aircraft.

The angle of attack is below the critical angle of attack, and the stall can be recovered before the lever can be attempted.

Otherwise, when the plane stalls, simply pulling the lever to stop the plane from falling is just drinking poison to quench thirst, and will only make the plane's stall become more and more serious.

But Xu Xian couldn't complete this simple operation. After he tried to pull the lever, he found that the steering wheel was stuck and he couldn't pull it.

Xu Xian realized that he was not a weak person who had no strength to tie up a chicken. He would not be unable to lift even a pole!

"Stuck?" Xu Xian had this thought in his mind for a moment, and the current situation was indeed like a jam in the pitch control.

But the strange thing is that the aircraft was cruising fine just now, and the pitch control surface of the aircraft should be relatively balanced. Even if the control surface suddenly jams, I don't know why such a big change in the attitude of the aircraft will occur suddenly.

At this time, Wang Qian didn't care about wearing an oxygen mask. If they rushed down again and plunged into the thundercloud area, they would probably be half cold.

Throwing away the oxygen mask with one hand, Wang Qian also held the steering wheel with both hands and began to exert force in cooperation with Xu Xian.

Unlike Airbus aircraft, due to its fly-by-wire control characteristics, if two people perform control inputs at the same time, the control input will not be superimposed. However, Boeing's transmission system is relatively traditional. If two people carry the lever together, it can

Produces greater rod input.

In the cockpit, Xu Xian and Wang Qian had blue veins on their foreheads, but they still could not stop the plane from falling. However, they were sure that the plane's pitch control was not blocked.

Although the state of the aircraft was not corrected, the two of them worked together to bring in a little bit of input, even though this small amount of input could not return the aircraft to its normal state.

At this time, the peculiar smell had penetrated into the cockpit. Xu Xian and Wang Qian were focused on carrying the poles and did not notice the increasingly strong smell in their noses.

"What happened to the plane?" Xu Xian couldn't figure out why the plane suddenly became like this. It didn't make sense at all!

Wang Qian on the left used excessive force in order to carry the pole. His face was already red and his eyes almost popped out.

Suddenly, Xu Xian's ears twitched, and vaguely, he seemed to hear bursts of noise coming from the cabin, and it was very close.

With a thought in his mind, Xu Xian gritted his teeth and clicked on the surveillance screen of the front cabin cabin. Sure enough, at this moment, several passengers had even rushed to the cockpit door.

"These crazy people!" Xu Xian cursed. He probably knew why the plane was like this. He quickly turned on the passenger announcement and broadcast directly: "If you want to survive, go back to the back! If you stay in the front, the plane will take control."

If not, everyone will die together!"

Once the aircraft's center of gravity exceeds the forward limit, the most intuitive impact is on the aircraft's pitch controllability. As now, a large number of people gather in the front cabin, which will directly make the flight crew's pitch operation extremely difficult. Now, together with

I can't even carry the pole, and I'm afraid many people have already rushed into the front cabin.

Although Xu Xian can probably guess why so many people ran to the front cabin, and people are indeed prone to make some completely unreasonable behaviors under certain special circumstances, but in fact, their behavior is not to avoid danger, but to avoid danger.

It's putting yourself to death.

They have no basic knowledge about flying and think that the flight attendant's words such as saying not to change seats are just making a fuss, but they don't know how much such behavior causes obstacles to the flight crew's control.

Xu Xian would not blame them or hold them accountable afterwards, but that didn't mean that he could still discuss things with them calmly now. He was quite restrained by not greeting their eighteenth generation ancestors.

The steward who was in the front cabin to maintain order could no longer control the situation. Many agitated passengers were moving forward aimlessly. They didn't know the point of pushing forward, but they just wanted to do this.

In fact, many passengers who rushed forward were incited and coerced. Even if they felt that they were being rushed to the front cabin, they had to keep up. In fact, they did not understand the difference between the front cabin and the rear cabin.

Not long ago, when the smell had not dissipated, there was still some difference between the front cabin and the rear cabin. But now it can be smelled even in the cockpit. There is no so-called air that can be breathed directly and smoothly on the entire plane.

There is no big point in running to the front cabin.

As for the so-called burnt carpet, many people didn't see it clearly, so they were frightened by several leaders.

A group of people who have lost their minds and ability to think cannot maintain order with just a few flight attendants and safety officers. This fear reaches its peak especially when the aircraft has extremely obvious changes in attitude.

Passengers can feel that the plane is descending, and some people who have taken many seats on the plane can very clearly feel that there is something wrong with this downward attitude.

In a normal flight, except for a very few stages of general ascent or descent, the passengers in the cabin actually feel that they are not big. However, this time, the passengers in the cabin need to grab something to maintain the stability of the body. The entire cabin has

It's a huge slope.

Such an abnormal state, combined with the extremely irritating gas and the suspected burnt carpet, made more "imaginative" passengers even more frightened.

It’s just that they don’t know that the root cause of all this actually comes from themselves.

Not knowing, not being clear, the unknown is the fear. But when the broadcast from the cockpit came, they suddenly realized that they themselves seemed to be seeking death, and the noisy cabin fell silent for an instant.

It turns out that there was something wrong not with the plane, but with them. It was their running around that caused the current state of the plane.

Seeing that everyone seemed to have calmed down, the flight attendant quickly shouted: "A large number of people gathering in the front cabin will cause the plane's center of gravity to exceed the limit. Please sit back in your original position!"

After the steward's explanation, the passengers who were already a little shaken began to move back one after another, and dispersed much faster than they had gathered just now.

Within a few seconds, there were not many people left in the entire front cabin.

They rushed over like a tidal wave and rushed back like a tidal wave. Everything was as ridiculous as a farce.

Driven by the pressure of survival, those passengers who were like headless flies just now finally chose to listen to the words of the flight attendant and returned to their original seats at lightning speed.

All these changes were reflected in the cockpit, that is, Xu Xian found that the force on the control began to decrease, the aircraft's pitch attitude began to gradually decrease, and slowly the aircraft began to return to the point where it could be controlled manually.

As long as people do not gather too much in one place and the center of gravity of the aircraft is within the standard range, the aircraft is controllable.

"I almost fell into a minefield."

Xu Xian wiped the sweat from his head. After the plane leveled, he turned on the autopilot and calmed down a little. His hands were slightly sore and numb from the excessive exertion just now, but the situation should not be serious. He should take a rest.

That’s it.

Wang Qian, who had been exerting a lot of force just now, collapsed directly on the seat, breathing heavily, like a puddle of mud. Faced with the fear of death, Wang Qian really used up all his strength to breathe.

After returning to normal, I suddenly felt like I was out of strength.

Wang Qian rubbed his temples: "I really lack exercise. Why do I feel dizzy and want to vomit when I just took the pole?"

"So exaggerated?" Xu Xian asked strangely. Sometimes after exerting too much force, you will feel a little uncomfortable. But although the force was too strong just now, it didn't last long, so it wouldn't be such a big reaction.

However, I don't know if it was due to psychological factors. After listening to Wang Qian's words, Xu Xian seemed to feel uncomfortable everywhere.

At this moment, Chengdu Control came over and asked: "Xingyu 6333, have you decided to drop the plane?"

Just now, the plane suddenly descended without warning. The Rongcheng control team thought that the crew decided to rush into the minefield, but after descending for a while, the plane leveled off again, which was really strange.

Now Xingyou 6333 has declared an emergency, and the surrounding airspace has been cleared under deployment, allowing the crew to act according to the situation. So when Xingyou 6333 began to descend, the Chengdu control did not ask anything to avoid disturbing the crew's work.

.

In an emergency, the workload of the crew is extremely heavy. If I get involved without anything else, wouldn't it increase the workload of the crew? There are no planes below Star Travel 6333, so it really has no impact.

After the plane leveled off and stabilized, the Chengdu traffic control team saw that it was almost done, and then asked what happened.

Wang Qian squeezed half of his face, picked up the earphones and was about to reply, but as soon as he opened his mouth, a strong feeling of vomiting hit his heart. He threw away the earphones, grabbed the waterproof bag next to him, and retched into the waterproof bag.

Seeing that Wang Qian was unwell, Xu Xian quickly took over the communication and replied: "There was some chaos on the plane just now, but now the situation has stabilized."

"Chaos?" Chengdu Control didn't quite understand what the word meant, but it was good to hear that the situation had stabilized, so he asked: "Then will you maintain the current height, or will you rise back to the original height?"

Star Tour 6333 was leveled nearby, but it has not actually returned to its original height. In other words, the height of Star Tour 6333 is now slightly lower.

"No need!" Xu Xian said. The problem below is just a minefield. We can't touch the minefield at the current height. That's good. We don't have to climb up anymore. We have to come down soon anyway.

Just when Chengdu Control wanted to ask something else, a series of signals requesting calls came from the cabin, which seemed very urgent.

Xu Xian knew that the Rongcheng control department couldn't help him now, so it was better to deal with the matter at hand first.

"Wait a moment!" After temporarily coping with the control, Xu Xian changed the internal call and asked: "What's wrong?"

"Brother, I have something to tell you face to face on the 2nd." The flight attendant said anxiously, and then added: "It's very important."
To be continued...