Super military empire

"Director Liu, there is no problem here. It is not reflected on the black box. It should be normal. The propeller hub of the helicopter may not be lubricated in place during takeoff..." Liao Zhuojing frowned and said.

During the flight test of the helicopter, such slight vibrations were normal.

They allowed the Zhi-7 to fly for a long time, and they still let the Zhi-7 produce several prototypes for test flights.

"Yes, Director Liu, when I flew straight to -7, I encountered many situations like this, and there was no problem." Huang Pingyang also frowned and said.

Before, everyone had a discussion together, and the plane was flying in the low sky under the attention of many people. Otherwise, it would not be enough to let the test pilots have many lives.

"Is there any problem, let's not talk about it for now, tell me, how many times did you encounter this kind of slight vibration during the test flight?" Liu Yijiu shook his head, he was not sure, but he couldn't let go of any details. .

Especially when there is no problem now.

Liao Zhuojing’s team used to work with single rotors, but now they work with double suspense. The helicopter is empty, and it fell off without loading anything. Obviously, this situation is abnormal.

Moreover, this kind of vibration only appeared after flying several tens of meters, not when it just took off at the beginning, so it appeared even more prominent.

Whether it was caused by this small shock, Liu Yijiu couldn't guarantee, but he couldn't rule it out like others.

He is not an expert in helicopters. It is only through his understanding of the structure of various old-fashioned equipment that Liao Zhuojing has not blushed from chief designer to chief engineer, and he himself becomes chief designer.It is for this reason that the helicopter can make its first flight now.

The time is too short, and they didn't even notify the big guys above. Only after the first flight is successful will they report the test schedule and progress of this project.

"For about seven or eight seconds, the plane flew very smoothly, and then there was no abnormality. It just fell off like this. I thought the propeller was off, but the sound of the propeller was still roaring, and the joystick was also very flexible. Yes, the indicator light didn't flicker..." Huang Pingyang looked depressed when he said here.

It's been a long test flight, this is the first time I have encountered it.

The Zhi-91 is much larger than the Zhi-7, and the maneuverability of this helicopter is much better than that of the Zhi-7. Thanks to the large-scale use of hydraulic devices, the operation is very light and flexible.

But it didn't happen at all that the plane fell down when there were no signs.

"How did you feel that the plane fell? Didn't it shake at all before it fell?" If the engine stops and the propeller stops rotating, it is impossible to completely stop in a few seconds.

"There is no vibration, the plane is falling down, I can feel it completely, level flight is different from descent. I didn't operate to descend at all..." Huang Pingyang replied helplessly.

He is more than 40 years old, and this experience is very sufficient.

When the Zhi-5 sample came out, he served as a test pilot, although he did not fly a few times.

As an experienced and excellent test pilot, I can make a rough judgment as to what situation is and what problem is causing.They can be regarded as half experts in science and technology.If you don't understand the equipment you use, you can't show the performance of the equipment you use to the greatest extent.

Liu Yijiu did not speak, but closed his eyes and imagined the situation when Huang Pingyang flew.

He is not a test pilot, and he is unable to and physically knows how to drive, but he wants to vomit when he sits upright -5. He can feel all kinds of problems during the flight of the aircraft, but there is no pilot. That's intuitive.

I couldn't figure out what was going on, and then I asked the managers and technicians again. They were observing the area at the beginning. The performance of the helicopter in the air, every movement, every second, affected them. Heartbeat.

In the end everyone told Liu Yijiu in unison that they didn't see any abnormalities.

The wreckage of the helicopter is on the ground. Perhaps the wreckage is not too appropriate, because the plane fell from a height of more than 20 meters and did not disintegrate at all.

The huge body turned over and lay on a gentle slope, like a truck after a car overturned, perhaps because the emergency landing was not successful, after all, the entire system failed at the end.

The deformation is real in many places, even the bulletproof glass in front of the cockpit has no cracks.The only problem is that the tail beam is deformed, and the blades of the rotor are all severely deformed.

Such a shape proves that the structural strength of their design is not too problematic.

"Have you analyzed the problem of rotor blades?" Liu Yijiu asked Liao Zhuojing after checking the condition of the aircraft.

"The rotor blades were destroyed after we saw them fall and hit the ground..." Liao Zhuojing has always been in a bad mood.

Not finding the problem is the biggest problem.

They would rather find a lot of problems on this helicopter than encounter the situation where they can't find any problems.

"Later, the operating system failed. Have you analyzed what caused it?" Liu Yijiu continued to ask.

In that case, the operating system is clearly malfunctioning.

The problem is that even if the operating system fails, the aircraft will have a process of losing control in the air, and the pilot can feel the problem.During the test flight, there were quite a few technicians nearby watching the situation.

The flight test plan was originally formulated, and the flight altitude and flight time were strictly regulated.

The observing technicians found no problems at all.

"Remove the engine, as well as the propeller hub and drive shaft. Do a careful inspection of the other various systems..." Although I have searched it again, Liu Yijiu does not believe that the problem is really not found.

As long as there are problems, they can be found.

There is no problem in other places. The operating system only started to fail when the plane was dropped. According to Liu Yijiu's memory, there was only one such situation-the compressor!

It was caused by the kind of vibration reported by the test pilot.

In professional terms, this phenomenon is called surge.

Surge is a very harmful and unstable working condition of the compressor on a helicopter that provides a higher air boost ratio to the turboshaft engine.

When the compressor surges, the air flow, pressure, and speed will change suddenly, and even air backflow will occur, which will cause serious mechanical damage to the engine, or cause the engine combustion chamber to extinguish and stop...

The airplane falls down because the lift is less than the weight of the engine on the entire airplane.

The rapid decline indicates that the lift suddenly becomes too small...

The plane that was flown in the test did not carry anything on it, but the weight of the test pilot was added in the air. If this happens, it means that the rotor cannot provide upward lift in an instant...

The biggest problem is the engine.

But even if there is a problem with the engine, it should not fall down so quickly.

This is one of the most confusing questions.

Rao Liu Yijiu read countless data and analyzed countless times, but he wanted to break his head and couldn't figure out what happened.

Even if the engine is stopped, the rotor will not stop instantly, and will gradually reduce the speed under the inertia.Unless in the process, the lift suddenly disappears.

Looking at the two rotors on the plane that had been completely deformed, Liu Yijiu frowned and stared blankly.

In order to increase the stability of the helicopter and solve the problem that the Mi-24 loses its stability during high-speed flight, Liu Yijiu uses a coaxial twin-rotor, which is often referred to as a twin-rotor coaxial helicopter. Typical representatives are the cards 26, 226, 50 and 52 of the Soviet Union.

The two rotors rotate in opposite directions, and their anti-torque can cancel each other. There was no need to install a tail rotor. In order to improve maneuverability and make the helicopter more flexible, Liu Yijiu also added a tail rotor.Although this design is very weird for this era, Liu Yijiu understands that some conceptual changes take time.

He didn't want to explain, the pilot would find out during the flight.

The two rotors rotate in opposite directions and provide upward lift at the same time, which can make the helicopter's takeoff mass greater.

I kept thinking and deducing in my mind, simulating like a computer how the two rotors would make the upward lift cancel each other out while keeping the rotation.

"Director Liu, or else, let's go back first and think about it when we go back. I will ask them to check again, not even letting go of every screw..." Liao Zhuojing was really helpless.

There is no problem at all!

"Screw!" Hearing this, Liu Yijiu's eyes lit up in a daze.

"Let someone check it...no, I will check it myself..." After Liu Yijiu finished speaking, he ran towards the helicopter that had fallen not far in front.

On the helicopter, several workers are preparing to disassemble various parts of the helicopter.

Seeing Liu Yijiu sliding down while running down, he fell twice in a row, and the staff who was going to the helicopter couldn't help but hurriedly stopped him.

"Look at the screw at the connection between the rotor and the hub, and take it off..." Liu Yijiu said to the personnel on the helicopter, despite the pain that his butt fell.

"What does this have to do with screws?" Liao Zhuojing smiled helplessly, he did not understand Liu Yijiu's thinking mode.

"It's on the screw! I'm sure that the side where the screw connects to the blade has been damaged quite badly. The blade is installed upside down!" Liu Yijiu gritted his teeth.

"Impossible, the two rotors are the same..." Liao Zhuojing felt that Liu Yijiu's words had no sense at all.