"Buzz~Buzz~" Every time a plane flies overhead, a loud roar can be heard on the ground. Sometimes you can see the plane "drawing" a white arc in the air, as if creating a long series of "clouds", which is releasing oil in the air.
It seems to be a common occurrence for airplanes to release fuel in the air. In October 2019, a plane flying to Melbourne released 30 tons of fuel directly in the air, and finally landed at Shenzhen Airport.
As for the matter of aircraft refueling, it is indeed puzzling: why is aircraft fuel so expensive, and why is it often released in the air, and does the oil released not pollute the environment?
Fuel is released in the air for safety
Many people have only heard of the possibility of flying and refueling airplanes, but they have not seen them. Mr. Wang, a passenger, sat by the window when he was on a plane and saw with his own eyes the "grand scene" of oil being released from the air.
On that day, shortly after the flight he was taking off, he suddenly heard the radio saying that there was an emergency, and a passenger suddenly fell ill and the plane needed to land as soon as possible to take him to first aid.
At this time, the scene outside the window attracted Mr. Wang's attention, and he saw that a hole in the wing continuously sprayed fuel, turning into a white arc in the air. The plane returned to the airport to land after refueling in the air, and the crew took the patient to the hospital.
Coincidentally, in March 2019, a passenger on a China Eastern Airlines plane suddenly fell ill and became seriously ill during the flight. If you continue to fly as originally planned, something could go wrong.
After careful consideration, the crew finally decided to discharge 39 tons of fuel in the air in order to ensure the safety of passengers, according to the market price of about 5,000 yuan per ton of oil, for the loss of air fuel, the airline also needs to pay the air traffic control command fee, the ground support fee after landing, etc., this time the loss of 450,000 yuan.
There is no cost to these loss of sudden illness passengers, and the airline will cover part of it, and the insurance company will cover part of it.
If there is an emergency, you need to return to the airport, and everyone can understand it. But why the plane releases fuel in the air, many people are puzzled. Isn't jet fuel a waste when it's not cheap?
In fact, releasing oil in the air is a last resort, not a deliberate attempt to waste money. Usually, the plane will have a specific route, before take-off with enough fuel for a flight, an aircraft is not small, the weight of fuel alone is as high as dozens of tons.
When you take off from an airport, you need to constantly consume fuel on the way, and there is not much fuel left in the fuel tank at the destination airport. As a result, the weight of the aircraft was reduced and it was able to land smoothly.
However, it is inevitable that there will be unexpected situations during the flight, such as sudden illness of passengers, or sudden changes in weather that make it unsuitable for flying. If this happens, it would be life-threatening to continue flying, and in order to ensure everyone's safety, the captain will choose to return to the airport or land nearby.
However, if the plane lands right after takeoff, the fuel tank will be overweight. Due to its large size and mass, it will have an unexpected disaster once it gets out of control.
Overweight aircraft will have greater inertia when landing, and there will be a dangerous situation of rushing out of the runway, which will not only destroy the aircraft and buildings, but also cause serious casualties.
If the landing gear or engine failure of the aircraft itself needs to make an emergency landing, and the aircraft has a lot of fuel, there is a high probability that there will be friction and collision between the fuselage and the ground during the forced landing, and the sparks caused by it may cause a violent explosion due to fuel, and the safety of the crew and passengers cannot be guaranteed.
In addition to the above, if there is an imbalance in the left and right wing fuel tanks during the flight, or if the fuel system failure disrupts the normal fuel consumption sequence, resulting in an unstable center of gravity of the aircraft, the aircraft will also be drained to maintain the balance.
All in all, the aircraft refueling is a last resort, and it is also a choice made for everyone's personal safety. Compared to human safety, no matter how expensive fuel is, it is insignificant.
Aircraft aerial refueling system
The aircraft is a large means of transportation, it is not easy to make such a big guy fly, it needs a steady supply of power, and the fuel system is the basic guarantee for the aircraft to fly safely in the air.
Aircraft are designed with safety in mind, and the same is true for fuel systems. Among them, the three systems of fuel supply, oil delivery and oil discharge are very important for flight safety.
The aircraft has refueling joints, and liquid level control and refueling valves are arranged in each fuel tank to achieve ground pressure refueling. When the fuel is added to the level of the level controller, the remote arm float inside floats up, which will control the refueling valve to close.
When it is necessary to release fuel in the air, the pilot first needs to determine the amount of oil discharged, and then the operator will strictly follow the command of the controller.
Turn the control on the shut-off valve and you can start draining the oil in the air. The oil is usually pumped to the wingtips of the aircraft through a drain pump, avoiding the engine, and is discharged from the pipe when the switch is turned on.
At this time, passengers sitting near the wing windows can see the oil discharged from the pipes, and a wisp of "white smoke" is like a show in the air.
Fuel discharge cannot be done all at once, special circumstances or factors must also be considered, if there is fog, thunderstorm weather is not suitable for landing, need to go to other backup airports, will need fuel to maintain the flight.
The whole system is considered for flight safety, and the fuel drain system is also to escort the safety of passengers.
"Kerosene rain" pollutes the environment?
It is understandable that the aircraft is refueling in the air for safety. However, there are also many people who are worried that if so much fuel is emitted in the air, won't it rain "kerosene rain"?
In fact, there is no need to worry about this, since it can be released in the air, it is natural that all countermeasures have been thought of in advance. There are not a few planes flying in the air, and not every aircraft can release fuel at will, and you need to obey the command.
Most airports will set up a special oil release area, once emergency oil release is needed, there will be a special controller to direct the aircraft to fly to a special oil release area far away from the city, airport, forest.
An area of more than 16 kilometers is protected and no other aircraft are allowed to enter. There is no fixed amount of oil discharge, and it needs to be put to the maximum landing weight.
If the aircraft needs to land in an emergency due to a malfunction, it usually only needs to ensure a 45-minute flight fuel supply, and a 15-minute flight fuel supply is only required for a forced landing.
It is impossible to say that the oil discharge does not pollute the environment at all. With so much fuel emitted in the sky, the environmental impact must be considered.
Therefore, the oil is atomized and diluted before it is discharged. When the oil is discharged, it is usually at a height of 3,000 meters above the ground, and the oil is atomized into very fine "oil droplets" and discharged out.
These oil droplets are very fine, and when discharged, they float in the air like fog visually, rather than directly discharging the oil to the ground to receive the baptism of "kerosene rain".
This oil mist will turn into oil and gas when the wind blows, which will be diluted in the air and disappear. In order to avoid pollution as much as possible, the oil is discharged in the ocean, in the mountains or in the wasteland.
Not all airports have oil release areas nearby, so if you need to release oil in an emergency and there is no oil release area nearby, you need to coordinate with the surrounding control unit and ask for help.
Of course, not all aircraft can complete the action of refueling in the air, and many large civil aircraft are currently equipped with fuel drain pipes at the end of their wings. Narrower aircraft, such as short-haul aircraft such as Boeing 737, have less fuel load and do not have the function of draining fuel.
In the event of an emergency, such aircraft will choose to hover in the air and drop the fuel consumption to a safe value before landing.
The original intention of the invention of the airplane as a means of transportation was to shorten the traffic time and serve the passage of people.
The safety of people's lives should always come first, and air oil release is a helpless choice to ensure safety, if you encounter this situation during the journey, do not panic, the crew will do their best to ensure everyone's safety.