What happened when a passenger plane from Taiwan Province of China landed at a Japanese airport and caught fire and exploded? Was it an accident or a man-made conspiracy?
On August 20, 2007, China Airlines Flight 120 was about to land at Naha Airport in Okinawa, Japan, carrying 157 passengers and eight crew members, and flight attendants were making final preparations for landing. The excursion went very smoothly and was a pleasant flight for the two experienced pilots, when the plane began to descend sharply in preparation for landing, releasing the flaps behind the wings and the slit wings in front, which could reduce the speed of the aircraft, and the landing was very standard. The co-pilot also folded up his flaps after the plane landed, and the plane taxied as usual, then slowly stopped at the airport, the seatbelt lights went out, and the passengers began to pack their bags and prepare to get off the plane. However, at this moment, a passenger noticed the abnormality, and the engine on the right side of the plane suddenly emitted smoke and then burned violently, while the pilot was still performing the operation of the checklist. Just then, the cockpit alarm lights came on and flashed, and the airport personnel radioed to inform the crew that there was an emergency and that the plane was on fire, asking them to stand by.
The fire truck arrived immediately, panic soon spread in the cabin, the flight attendants began to carry out emergency evacuation, the fire outside became larger and larger, the engine on the left also began to emit smoke and fire, and the wings on both sides began to catch fire, at this time the flight attendants must evacuate the passengers as soon as possible, because once the fire spreads to the fuel tank, the consequences are unimaginable. However, the cabin doors cannot be opened yet, as pilots must follow the steps of evacuation checks. After completing a series of operations, the pilot finally opened the hatch, but all 157 passengers walked to the exit, and it would take some time, in which case unpredictable situations would occur at any time. The fire grew louder, the cabin filled with smoke, and everyone slid down the slide and fled quickly. The plane had been burning for nearly three minutes, and there was a possibility of an explosion at any moment, and the flight attendant, after inspecting the cabin, informed the captain that the passengers had been evacuated and then fled the plane, and the captain could only leave after confirming that there was no one on the plane, but it was too late. The cabin was completely covered in smoke, the fire blocked the escape exit, and they had to flee through the cockpit windows, while each 737's cockpit was equipped with an emergency escape cable to give pilots to exit the plane through the side windows. Just as the co-pilot escaped from the window and was still in mid-air, the plane suddenly exploded, and the ground shook with it. The co-pilot fell directly from the window to the ground under the impact of the explosion, but fortunately he was able to get up and quickly escape the fire.
At this time, the entire aircraft was surrounded by fire, and the airport was shaken by explosions and vibrations, fortunately, the captain also escaped without any danger, at this time the fire truck finally arrived at the scene, and the rear half of the aircraft fell to the ground because of the high temperature disconnection. Incredibly, on Flight 120, it was a miracle that everyone escaped unscathed. Then a team of investigators from New York came to the scene to investigate, and they were under pressure to find out why a plane that landed safely and had its engines turned off suddenly burst into flames. The investigation team never encountered this situation, because usually the aircraft fire occurred during the flight phase or taxiing, so the investigation team was worried that if the aircraft had design defects, it would cause immeasurable disasters. At this time, there are more than 5,000 737 airliners in the world, which means that every three or four seconds around the world there is an aircraft take-off and landing, so the investigation team must find out the truth as soon as possible, they have to find the cockpit recorder and flight recorder, usually the black box data will provide them with many important clues. The investigators understood that with such a fierce fire, the data of the black box could be lost, and then they approached the captain to inquire, and the co-pilot recalled that the first time he saw the source of the fire was in the position of the wheel. Investigators know that if the wheel of Flight 120 catches fire, there may be several causes of the fire, one is that the tire leaks and causes the rubber to catch fire, and then the overheated brake disc may ignite the hydraulic oil, the aircraft's wheel compartment lays a lot of hydraulic lines, and the hydraulic oil is extremely flammable, if the hydraulic system leaks, the hydraulic oil will burn up when it drips onto the hot brake disc. If the co-pilot's judgment of the ignition point was correct, the investigators should have found the corresponding evidence, so they checked the engine wheel cabin on the right side of the aircraft and the landing gear components, but according to the results of the investigation, they could be sure that the fire did not burn in the engine room, and it was obvious that the deputy captain had mistaken the ignition point.
However, to the relief of the investigation team, the black box of the plane was finally found, but it will take some time to download the complete data inside. At the same time, the investigation team continued to investigate the wreckage of the aircraft, which was a clump of charred wires, which attracted the attention of the investigation team, whether the accident was caused by a short circuit in the wires. While severe circuit failures are rare, such accidents have also occurred before. As early as 1998, a Swissair passenger plane caused smoke to rise from the cockpit due to a short circuit in the wire, when the pilot tried to make an emergency landing, but ultimately failed, and the plane finally crashed into the Atlantic Ocean, killing all 229 people on board. The investigators believed that if the fire on Flight 120 was due to a circuit problem, the data in the black box would definitely prove it, so they began to analyze the data in the black box, and if there was any circuit problem or failure on the plane, it would be reflected in the data, but the investigators checked hundreds of circuit systems and found nothing, and there was no evidence that the aircraft caught fire because of the circuit problem.
After ruling out the wheels and circuit problems, the investigators focused on the engine on the right side of the aircraft, which was more than 1,000 degrees Celsius in flight, higher than the temperature of the magma, but the investigators carefully examined the engine of the aircraft and ruled out the possibility of engine fire. With thousands of 737s flying every day, the pressure on the investigation team is increasing, and investigators have to increase their efforts to find clues, and their efforts have paid off. On the day of the incident, a ground crew member clearly saw that before the plane caught fire, there was liquid left in the wing part, and there was only one possibility of the liquid flowing out of this part, that is, aviation fuel, because the 737 passenger aircraft had 16,000 liters of fuel, most of which was stored in the two huge wings of the aircraft. The investigation had made a major breakthrough, and it was now imperative to find out where the oil had leaked, with a high-pressure oil pump in the wings of the 737 that injected 750 litres of fuel into the engine every hour, with all the fuel entering the engine flowing through the soft tubing. So the investigators began to carefully examine each tubing, and this time they still searched the entire fuel system of the aircraft, but they still found nothing, and the oil pipe of the aircraft was completely without problems. Investigators still can't explain the cause of the fire, they only know the fire caused by the leaking fuel from the plane, but they can't figure out where the fuel leaked out.
After ruling out the possibility of a fire in the tubing, the investigation team turned its attention to the fuel tank, which is made of aluminum alloy material, and the design can pass the strict test of many years of flight, and theoretically should not be cracked or leaked. The investigators shot the hole probe deep inside the tank and found a bolt piercing the tank in an inconspicuous position. Although the source of the bolt is unknown, the part of the fuel tank pierced happens to be the place where the ground crew found the oil leak, which is a breakthrough in the investigation. Finding the location of the oil spill, the next investigation focused on finding the source of the bolt, they studied the structural schematic diagram of the 7377, and then traced the maintenance records of the aircraft, and finally figured out the source of the part. This bolt is called the lower stop component, which is part of the leading edge of the wing front, the pilot will release the flaps and leading edge slats every time they take off and land, and the lower stop component is installed at the end of the sliding track of the slit to limit the range of movement of the front slat.
In simple terms, this component locked in the maximum stretch length of the front slat, but just knowing this was not enough for the investigation team to find out what had happened and let the bolt penetrate the tank. The investigators studied the 737 maintenance manual in detail about the repair of the lower stop gear components, and did not expect to make an unexpected discovery. The workshop manual has documented two incidents in which a lower gear component fell off and caused a minor fuel leak, but this was the first time that a severe fire had been caused. Obviously, Boeing knows the existence of this problem, so for the lower stop gear components on the global 737 passenger aircraft, a special repair work order was issued on this plan, Boeing suggested first removing the screw hairs on the lower stop gear components, and then coating the nut with a layer of solidification material, and finally putting the nut back, so that the nut will be more stable. Investigators suspected that the plane had not been repaired as required, and after an investigation learned that the plane's maintenance had only been completed a few weeks earlier. The investigation seemed to have reached a dead end again, the investigators rechecked the lower stop components on the 120 and compared them one by one according to the drawings, and finally they happened critical, and a gasket was missing. Subsequently, the investigation team found the gasket near the wing foreman. But the problem arose again, the nut was firmly tied to the bolt, but the middle washer was missing, which was unreasonable. Based on this, the investigation team decided to go to the headquarters of China Airlines, hoping to find clues to the falling of the gasket here. A mechanic demonstrates the process of repairing the lower stop component, which may seem relatively simple, but it is a bit cumbersome to perform. The mechanic worked in a place with a small visual range, and he could only feel the parts with his hands by feeling, and he could not see the above situation at all, because the parts occasionally fell off, the repair work had to be interrupted, and even if the final repair work was completed, they could not confirm that all the parts were installed properly.
The investigation team believed that there was only one reason for the washer of the lower stop gear component to fall off, that is, it fell off during the maintenance work, and the mechanics ignored this. Investigators found the lower stop component on the 120 to test its absence of a gasket, and they were surprised to find that this small gasket was the only connector used to fix the entire component position. In other words, without a gasket, the entire component will fail. The engineers of the 737 will maximize the use of space when designing the aircraft, so in the leading edge of the slat area, they designed a structure called the orbital tank, and this orbital tank is used to accommodate the sliding rail of the slit, and the space of the rail tank is very narrow, can only accommodate the sliding of the lower slit rail, if there is a foreign metal foreign body falling into the rail tank, the accident is inevitable.
At this point, the investigation team has fully grasped the cause of the accident. A few weeks before the incident, a careless maintenance work has planted a bane, an uninstructed gasket, so that the entire lower gear component into a safety hazard, just when the aircraft is preparing to land at Naha Airport in Okinawa, the pilot released the flaps and slits, and at this time the lower stop gear component is almost about to fall off, and then the shock generated by the landing directly shocked him down, and the unsuspecting crew soon put away the flaps and slits, and the aircraft's powerful hydraulic system retracted the slats into the orbit tank, At this time, the lower stop gear component has fallen into the slide rail, the slit wing will bolt inward, the fuel tank of the right wing is instantly punctured, the hole in the fuel tank caused fuel leakage, when the aircraft is stopped, the exposed fuel is directly sprinkled on the hot tail nozzle, and the fire engulfs the aircraft in an instant. Fortunately, the professional organizational skills of the flight attendants allowed all 157 passengers to escape in 1 minute and 42 seconds, otherwise the damage caused by the explosion would be unbearable. No one would have imagined that an inconspicuous gasket would burn an expensive airliner and then discover that there were 20 airliners in the United States alone. Subsequently, Boeing rectified this component, and the aviation accident was no small matter, and the crew and the airline should be treated strictly in order to ensure the safety of passengers.