Chapter 448? Option 3, Drive Away

Chapter 448 Plan 3, drive away

Tang Guozheng arrived at the scene a little later, but the rain became even heavier.

In order to ensure the integrity of the scene as much as possible, the station urgently erected a huge rain shelter that could cover the Yun-8. This move left a very important piece of evidence at the scene.

Li Zhan discovered that there was obvious ice on the wings, and the flaps failed due to ice. This is completely consistent with his previous judgment. After carefully inspecting the appearance of the fuselage, Li Zhan was surprised to find that the crew and millions of cargoes were just a hair away from entering hell.

According to his understanding of the Y-8, the icing phenomenon on the wings means that the aircraft will crash at any time, maybe the next second. The successful emergency landing of cargo flight 8Y1771 was simply the blessing of fate.

"What do you see?" Tang Guozheng strode over and asked Li Zhan, who was standing on the wing.

Li Zhan pointed to the wing under his feet and said, "There is obvious icing. They are at the gate of hell."

"Icing?" Tang Guozheng looked outside subconsciously. After the snow stopped, the temperature rose. At this time, the temperature must be above zero, but the temperature in the mid-to-high altitude was not the same. However, the icing phenomenon is not easy to explain.

Li Zhan jumped down directly, clapped his hands and said, "I asked the crew and the de-icing system is on. But the de-icing system of Yunba relies on engine heat to work. After the two engines no longer provide thrust, It affects the working effect of the de-icing system, and it is basically certain that this is the reason why the flaps are frozen."

Zhang Wei added, "Ice on the wings will affect air flow, and the consequences are no better than frozen flaps."

Pilots are naturally well aware of the consequences of ice on the wings, and senior pilots are even more aware of its seriousness. The wing is the main component that provides lift. Air flows smoothly from the top and bottom of the wing to generate lift or downward pressure, driving the aircraft up or down. Once the smooth flowing air is changed, the wings cannot normally provide enough lift or downward pressure, and the aircraft will continue to rise or fall uncontrollably, and the final result will be a stall and crash.

The consequences of frozen flaps are obvious - the pilot cannot control the aircraft to rise or land normally. The crew of cargo flight 8Y1771 should be thankful that they were in the maximum lift position before the flaps were frozen, that is, the take-off and landing position, otherwise they would not be able to support the nearby Zhongnan Station.

Tang Guozheng asked Li Zhan curiously, "Do you know much about Yunba?"

"I know more about other aircraft than I do." Li Zhan pointed to the Yun-8F-400 lying tiredly on the ground with a smile, and said, "I am familiar with every model of the Yun-8. It is no exaggeration to say that some models I You can even disassemble and assemble it with your eyes closed.”

Tang Guozhenghu asked, "Why are you so familiar with Yunba?"

Li Zhan shook his head slightly and said, "I can't say."

After being slightly surprised, Tang Guozheng stopped talking about this topic, while Zhang Wei felt even more strange. Li Zhan had never been exposed to the Yun-8 during his nine months in the Second Division. It should be said that except for the J-7E and the J-7E, he had never been exposed to other aircraft types. Could it be that Li Zhan came into contact with these aircraft while working in Beikou?

Tang Guozheng looked at the plane, his eyes fell on the blackened engine, and he frowned and said, "What do you think is the reason for the engine catching fire?"

They seemed to regard the civilian Y-8, numbered B-25277, as a military aircraft to study and discuss, and regarded the current accident as a military accident, so they discussed it very seriously. Li Zhan even regarded this accident as a rare opportunity for practical combat, and used his strengths to do some quite useful research and analysis.

Li Zhan said, "It should be caused by a hot start. The fuel supply system did not stop after the two engines stopped working. The crew only cut off the fuel supply when they restarted the engines according to the procedure. However, there was already a lot of fuel in the engine at this time, so The fire started after starting the engine with the help of the APU."

After a pause, he said, "An engine fire is not the most dangerous situation. I think icing is the main reason why the plane had to make an emergency landing. The crew had cut off the fuel supply to the burning engine in time. It was raining heavily at the time, and the fire in the engine room was In any case, it will not develop very big, but will gradually weaken. However, the crew did not realize that the loss of the two engines affected the normal operation of the de-icing system, and the wings and flaps began to ice. They thought that the flaps The failure was due to the fire in the engine room spreading to the wing, but it was not the case, the fire was not very big at the time."

"Have the cabin voice recorder and flight parameter recorder been removed?" Tang Guozheng asked following the words.

Li Zhan said, "No need to dismantle it, just extract it directly."

Zhang Wei reminded, "Chief of Staff, Captain Li, this is not our plane."

The two of them were stunned, and their emotions suddenly stopped. Li Zhan smiled awkwardly, "Oh, right, it's not our plane. The Civil Aviation Administration should be responsible for the investigation. Yes, I can provide them with some help and complete the investigation as soon as possible and remove the plane as soon as possible. "

"It should be no problem. They may be eager for us to help." Tang Guozheng said, "We can also learn lessons from this."

Li Zhan said, "While the weather has not changed significantly, Chief of Staff, send a few people to me. I will immediately start a preliminary investigation and fix some evidence."

"I will send you someone, but you must obtain the approval of the Civil Aviation Administration of China to launch an investigation. Let's do this. You can continue the investigation without affecting the situation on the scene. I will ask my superiors for instructions immediately." Tang Guozheng said decisively.

"yes!"

Zhang Wei asked someone at the ground station to find a SLR camera and follow Li Zhan's instructions to take pictures of some parts of the plane, especially several icy areas that had not yet melted. There is still no news from Tang Guozheng, but Li Zhan is getting more and more information.

Li Zhan's familiarity with the Y-8 series medium-sized transport aircraft is beyond ordinary people's imagination. He has actually had the experience of disassembling and assembling this type of aircraft with the maintenance team several times. With the help of several necessary auxiliary equipment and the tools at hand, they were able to basically dismantle the early models of Yun-8 within an hour.

The army's top soldiers are playing with the decomposition and combination of light weapons, while people like Li Zhan are playing with the decomposition and combination of aircraft. In order to allow pilots to have the ultimate understanding of the aircraft they master, Liu Guojian required each pilot to complete three tests that basically disassemble the aircraft and one assembly test within an hour.

Therefore, Li Zhan is very familiar with every part of the Yun-8, just like he is familiar with his own body parts.

A large number of subsequent modifications have remained unchanged. When the Yun-8 was modified, people like Li Zhan had been exposed to subsequent models and knew what was going on inside.

Li Zhan is well aware that a major flaw of the Y-8 series aircraft is that the de-icing and anti-freezing system is not easy to use, and it has not been completely solved so far. In order to prevent accidents due to ice, a large number of Y-8s are required to be restricted to areas south of the Huaihe River, and are basically not used in plateau areas.

By calculating the meteorological conditions in the airspace where 8Y1771 was located that day, as well as flight parameters, load, unpowered gliding distance and other data, Li Zhan surprisingly found that the flight was able to glide to the tourist airport even with only two engines left, provided that the de-icing system was turned off. .

The engine power occupied by the de-icing system has become the biggest obstacle restricting 8Y1771 from reaching the tourist airport. Of course, if the de-icing system is not turned on, 8Y1771 may not even be able to reach Zhongnan Station.

However, this discovery is of great significance and can provide useful reference opinions for manufacturers to improve the de-icing system of the aircraft. The weather encountered by 8Y1771 was very representative. In subsequent large-scale surveys, it was found that the same weather often occurs in the central and southern regions, but it has never been encountered by a Y-8.

More and more questions have been answered, but what caused the engine to stop has become the last clueless question. The investigation team of the Civil Aviation Administration of China, with the assistance of the army investigation team headed by Li Zhan, conducted analyzes in many directions, and several possibilities were ruled out.

Seeing that New Year's Day in 2012 was getting closer, Li Zhan raised a possibility - could the problem also lie in the de-icing system?

This is a system that is known to have congenital defects. Under normal circumstances, there will be no problems. However, when encountering the weather encountered by 8Y1771, the defects of the de-icing system will definitely be exposed.

But is there a possible relationship between the de-icing system and the stalling of engines No. 1 and 2?

Li Zhan told the civil aviation investigation team that the power system used by the Y-8F-400, which uses a turboprop-6 aeroengine as its main component, has a device to prevent excessive power. If the crew does not lift the restriction, the engine power will exceed the rated value. The rear limiting device will intervene to force the engine power to decrease. If this phenomenon continues, in order to prevent the engine from overloading and malfunctioning, the limiting device will continue to intervene. In this case, the engine may stall.

When the de-icing system senses that icing still exists, it will continue to request energy from the engine, occupying more and more power of the engine, and it is entirely possible that the engine will be overloaded.

The de-icing system and the engine protection limiter are not smart enough and are straight-forward. Unless the pilot intervenes to adjust their relationship, they will remain in a tug-of-war situation - the de-icing system keeps asking for more power, and the engine protection limiter is in a state of chaos. The engine speed is controlled to avoid overload condition.

To verify Li Zhan's analysis, a real-life experiment must be conducted. The investigation team requested assistance from the army, and the Flight Test Institute located in the Aircraft City accepted the task. After several days of experiments, the results were transmitted to Zhongnan Station. The investigation team was shocked after reading the conclusions - they were completely consistent with Li Zhan's analysis.

No one thought that the interaction between the engine limiter and the de-icing system, which was originally a protective device for the aircraft, would become the culprit that almost killed the aircraft.

The investigation conclusion of this accident attracted great attention from the airline company and the manufacturer. A higher-level investigation team went to Zhongnan Station before New Year’s Day to learn more about the situation. The detailed report of the military-civilian joint investigation team's exit made the high-level investigation team find a treasure, and basically determined the direction and methods to solve some problems encountered in the development of the Y-X tactical transport aircraft.

The remaining problem for Li Zhan is how to get B-25277 away. If he doesn't get the plane away, his next exploratory flight will be impossible.

A joint military-civilian investigation team came to the scene to discuss plans.

Option one is to tear it down and transport it away. Option two is to use a heavy-duty helicopter to lift it away.

The cargo has already been emptied. Both methods are feasible, but the first option will cause irreparable damage to the aircraft. Because the road down the mountain is difficult to pass over-sized flatbed trucks, the body must be divided, so that the aircraft cannot continue. After it is used, the usable parts can only be disassembled and used as aviation materials, and the body is put into the furnace.

Option two requires the use of the world's largest helicopter, the Mi-26. Only this helicopter can lift the Y-8G-400's body. However, it is still necessary to remove the wings to reduce the weight and bring it within the allowable load weight range of the Mi-26. And this method is very dangerous.

Everyone was discussing anxiously. On one side, the troops continued to clear the runway and resume normal operations. On the other side, the Postal Service also hoped that the aircraft could be repaired in the repair shop as soon as possible and put back into operation. The loss of a plane grounding for one day is hundreds of thousands. No matter how big the company is, Postal Airlines will not ignore such huge losses.

Li Zhan walked to the front of the plane and squatted down, staring blankly at the plane lying on the runway.

Tang Guozheng and Zhang Wei continued to discuss with people from civil aviation, airlines, and insurance companies, and their opinions gradually moved towards removing the left and right wings, vertical fins, horizontal wings, landing gear and other heavy parts, and then using Mi- 26 Lift away.

Zhang Wei noticed Li Zhan's abnormality and walked over. He also squatted down and followed Li Zhan's gaze towards the plane. "What are you thinking about? We are almost unanimous. Let's use the second option."

Li Zhan seemed not to have heard Zhang Wei's words and said to himself, "The aircraft has no structural damage. The friction damage on the belly should not have a big impact. The engine fire did not burn the wings, and the landing gear may not have any damage either." If it is seriously damaged, it should be possible to replace the two damaged engines and lift the aircraft up and drive away."

"Drive away?" It took a while for Zhang Wei to come back to his senses, his eyes almost popping out of his head, "Drive away? You mean fly away directly?"

Li Zhan was still thinking hard, as if he was calculating something in his mind.

Zhang Wei did not dare to disturb Li Zhan and waited with bated breath for Li Zhan's answer.

Suddenly, Li Zhan stood up, raised his hands and said loudly, "Option three! Drive away! The plane can fly away directly!"

The members of the military and civilian investigation team gathered in a circle on the right side of the nose of the plane looked over in unison.

Someone said, "Fly away? It's a sweet dream in broad daylight."

More people fell into deep thought after being surprised, and once again looked at the B25277 lying on the ground - the aircraft seemed to have no other major damage except for the damage to the two engines.

More and more people fell into deep thought, and then they became thoughtful. When several technicians quickly walked around the aircraft to observe, almost everyone's eyes lit up.

They realized this might be the perfect solution.

PS: I have to read Air Crash Day before going to bed these days...