Skirt for a fighter jet: 20 photos of mysterious clouds that are mistakenly called supersonic (21 photos)

Spectacular photographs of fighter jets in a dense cone of water vapor are often claimed to represent the aircraft breaking the sound barrier. But this is a mistake. Come in, we'll tell you and show you why.





F-18 Hornet



A vapor cone, shock collar, or shock egg is a visible cloud of condensation that can sometimes form around an aircraft.











This is the so-called Prandtl-Glauert effect - a physical phenomenon that occurs when an aircraft approaches the speed of sound. It has nothing to do with breaking the sound barrier.



This phenomenon often occurs at high subsonic Mach numbers, but can also occur in lower speed conditions, such as during high-G maneuvers of a fighter aircraft. The cloud is caused by extremely low pressure in the "expansion zone" of airflow around the aircraft, usually in relatively humid atmospheric conditions. A common misconception is that this effect is that the aircraft "breaks the sound barrier."



The surface layers of air are denser than the atmosphere at high altitudes. When flying at low altitudes, increased friction and drag occur.



"Blue Angels" (eng. Blue Angels) - aerobatics team of the United States Navy







Water vapor cones are associated with shock waves (of which there are several) that form around the aircraft as it gains speed.



F-15 Strike Eagle



For the Prandtl-Gloert effect to occur, certain climatic conditions are necessary - namely, warm and humid air.







At the moment when the speed of the aircraft approaches the speed of sound (about 1234 km/h at sea level), a difference in local pressure and temperature occurs in the air flowing around it.

As a result, the air loses its ability to hold moisture, and condensation forms in the shape of a cone.



The visible vapor cone is caused by a shock wave, which creates a difference in pressure and temperature of the air surrounding the aircraft

Because of the spectacular nature of the phenomenon, it is often used to popularize naval aviation.



Pilots deliberately maneuver over the sea, where the conditions for the Prandtl-Glauert effect to occur are most optimal.



The shock wave when an aircraft reaches supersonic speed is difficult to detect with the naked eye - the photo was taken using special instruments