Through the clouds: airplane handwriting
November 12, 2001 Side 587 – American Airlines, who followed from New York to the Dominican Republic, literally collapsed in the air almost immediately after takeoff at JFK International Airport. Since this, the second in the number of victims, a plane crash in the history of American aviation occurred shortly after September 11, the assumption of the terrorist attack immediately. But the investigation has shown that the reason was more prosaic: the plane came to the sensate trace – the turbulence zone created by another aircraft (in this case it was Boeing 747 Japan Airlines, having flown by the same air corridor shortly before the side 587). And although this trace was invisible, it was he who led to the loss of management and ultimately – to the tragedy.
However, sometimes traces become visible. The white trail of the flying aircraft is well highlighted in a clear sunny day against the blue sky. This trace is called inversion and consists of the same substance as the clouds – the smallest droplets of water. The reason for its occurrence is very simple: heated water vapor, formed when combustion of fuel, is thrown into the atmosphere (the temperature of which, for example, at an altitude of 10 km reaches 50 ° C), it quickly cools and condenses, forming small droplets of water. True, such a trading is not always formed – at various heights, the atmosphere has different temperatures and humidity, and the likelihood of the formation of the inversion trace depends on these parameters. To understand the mechanism of inversion, it is not necessary to go to the airfield: pairs of mouth, exhaled by a person, and couples from exhaust pipes cars in a heavy frost have the same nature (their education also depends on the temperature and humidity of the surround air).
By the way, in the opinion of some experts, an inversion trace can demure military aircraft. This is most important for high-altitude bomber and scouts, thanks to the technology of stealth "invisible" for radar, as well as for fighters in the near air combat, when the enemy detection occurs mainly visually. True, it is almost impossible to deal with his education. During the flight due to the special profile of the wing, the speed of air streams above and under the wing is obtained different (above above, than below). According to the principle of Bernoulli in this case, the pressure on the top surface of the wing is less than on the bottom (their difference is just forms lifting force). Due to the pressure difference, the air flows through the ending of the wing, and two vortex funnels similar to horizontal tornadoes are formed by the plane. Such vortices have a diameter of up to 15 m, the speed of air flows inside them – up to 50 m / s, they live a few minutes and until they roame, can be really dangerous for aircraft following the same corridor. In the interaction of vortex and inversion traces, the latter begins to break out, which sometimes leads to very bizarre "curls" and even weave two traces (from two engines).
In a tear
Condensation of water vapor, "exhaled" engines – not the only reason for the inversion trace, it can be formed even behind a glider that does not have engines. At the air show, you can often see how the fighters are literally in front of the viewers in front of the viewers! Magic? Not at all. The reason for this is the tear-off flows, the vortex areas of reduced pressure, resulting on the upper surface of the wing in certain flight modes (for example, when entering large attack corners). Inside these areas, due to the rapid pressure drop, the temperature decreases and the conditions for condensation of water vapor in the air arise. And although all this looks like magic, in fact, as you can see, there is nothing mysterious in such a fog.