An F-16 Fighting ****** pilot with the Viper East Demonstration Team from Shaw Air Force Base, S.C., creates a ‘cone’ of condensation on Aug. 21, 2010, as he nears Mach 1 during a flyby at an open house at Volk Field Air National Guard Base.
The ‘cone’ of condensation is known as a vapour cone, or shock collar or shock egg. The phenomenon is frequently encountered at high-subsonic Mach numbers, but can also occur in lower-speed conditions, such as high-g maneuvers by fighter aircraft. The cloud is caused by extremely low pressure in an ‘expansion region’ of the airflow around the aircraft, usually in relatively humid atmospheric conditions. A common misconception is that this effect is the aircraft ‘breaking the sound barrier’.
