Friends who have flown on the plane may find that after any flight has been boarded by all the people, there will be a flight attendant in the cabin door, one hand grasping the railing in the cabin, half of the body protruding out of the cabin, the other hand is dragging the heavy aircraft door, let it close, every time at this time you can see that the flight attendant is completely relying on her own strength, tight muscles to close the door. So, how heavy are the doors of the aircraft? Is it really safe to close the hatch in this way? Why is the hatch of an airplane not designed to close automatically like a high-speed rail train?
Airlines around the world every year will appear flight attendants in the front door of the aircraft, due to improper operation or on-site wind and other reasons, resulting in accidental fall and thus injured news, it can be said that before taking off to close the hatch to try some dangerous work, and now the technology is very developed, not to mention the high-speed rail train such a large public transport, even some passenger cars the hatch is able to achieve electric control and close, then the aircraft such a very high-altitude means of transport, Why are we still using the indigenous method of manually closing the hatches?
In fact, the very important reason is that any electric or other assisting mechanism in the world has no high mechanical structure reliability, and it is precisely because the aircraft, which is very dependent on reliability, is to pursue the reliability of various structures of the aircraft, so the aircraft hatch has insisted on the use of mechanical structure manpower closure for many years.
Don't look at the plane flying in the air, most of the time is very stable, but the biggest impact on the air flight is the air flow, sometimes the plane will find that it encountered turbulence, the original very smooth plane is like a bus driving on a country road that has not been repaired for many years, resulting in small but very frequent bumps. This kind of bump is not very important to people, but it is not a small test for the various structures of the aircraft. So what bad impact will the use of electric assist have on the aircraft?
If the aircraft hatch adopts electric mode, it is necessary to install a variety of electric mechanical structures near the door of the aircraft, then there will be a very contradictory situation in the structure of the aircraft, the aircraft is a very precisely designed means of transportation, every 1 kilogram of weight will have its meaning of existence, and must not affect the overall weight balance of the aircraft, if a very heavy but very stable electric mechanism is used, it will lead to uneven distribution of the weight of the aircraft. In this case, the aircraft must be counterweighted in other aspects, which will make the aircraft weight increase without members. On the other hand, the power on the aircraft is very valuable, if a very strong electric system is used, it will make the aircraft have to consume a large part of the electricity, and these electricity will come from the engine operation of the aircraft, which is likely to affect the engine's ability to power output, and increase more power burden, but will affect the reliability of the aircraft avionics system.
If the use of lighter structure of the electric system, then it is easy in the aircraft suffered from the process of air flow bumps, the electric system will be damaged, even if the aircraft can land smoothly, will also encounter a fault can not open the hatch, if the design of a set of can disconnect the power system manually switch the door closing automatic mechanism, which will add extra weight near the hatch, and there are many more cumbersome parts, the more cumbersome the parts the higher the possibility of failure, which leads to a decline in reliability. Of course, some people say that there is no need for a set of independent electric systems, such as the operation of the aircraft such as retracting the landing gear, and controlling the wings of the aircraft, there is a set of hydraulic systems to provide assistance, so the aircraft hatch is also added to a hydraulic assistance system, is not it more convenient than manually closing the hatch?
However, many people do not understand, this hydraulic system on the aircraft, the discussion about their reliability has lasted for many years, in order to save the aircraft power considerations, all the mechanisms that need hydraulic assistance on the aircraft are actually using a hydraulic system, this hydraulic system has some problems in any aspect, which will lead to the failure of the hydraulic control of the entire aircraft, and many air disasters and air crises documentaries have shown that after the aircraft hydraulic problems, the control rudder of the aircraft will become extremely heavy If the aircraft has a safety hazard because of the failure of the hydraulic system, the two aircraft pilots have worked hard to land the aircraft smoothly at the airport, only to find that the door of the aircraft cannot be opened because of hydraulic failure, if it is a serious damage to the aircraft, then the members of the aircraft will still be unable to get out of danger.
On the other hand, the weight of the aircraft's hatch is really not light, take the Boeing 767-300 type aircraft as an example, the weight of the front hatch of this aircraft is close to two tons, The weight of the rear hatch is also up to 1.3 tons, if you provide them with a set of hydraulic assistance system, the energy they consume is no less than a large angle of wing adjustment in the flight process, and after the failure of the hydraulic system, whether it can effectively open the hatch is a problem, the aircraft hatch will not be because of the internal problems of the hydraulic system, due to the sudden reduction in pressure, the hydraulic structure will cause structural damage to the aircraft's hatch, and even damage the sealing and locking mechanism of the entire hatch, the hatch can not be opened and not terrible, if the hatch is suddenly opened during the flight is really terrible.
Because the aircraft is actually a very stressful airtight cabin, once the aircraft hatch in the air leakage or even open for no reason, the aircraft door will become a channel for the air pressure in the cabin to flow outward, the air flow in the cabin will be all the items that are not fixed or even people pushed out of the cabin, and at the same time, due to the huge change in pressure, it will also lead to further damage near the aircraft hatch with the increase of the air flow, and its harm may lead to the direct disintegration of the entire aircraft in the air.
So far for safety reasons, in order to reduce any accidents that may occur during the flight of the aircraft, the vast majority of passenger aircraft around the world have not adopted aircraft doors with assistance systems, of course, there are a small number of exceptions, some Saudi aristocrats use large passenger aircraft such as Boeing 747 and even 767 as personal private aircraft, some of them have the front door of the aircraft installed with electric assistance mechanism, and the rear hatch still maintains a pure mechanical structure, after all, there will not be too many passengers on their private aircraft. Moreover, the aircraft has been customized with various decorations, and there is no need to worry too much about the weight distribution of the aircraft.