Transonic flow patterns on an aircraft wing showing the effects at critical mach.

The Critical Mach number (Mcr) of an aircraft is the slowest Mach number at which the airflow over a small region of the wing reaches the speed of sound. Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid [1]

For all aircraft in flight, the airflow around the aircraft is not exactly the same as the airspeed of the aircraft due to the airflow speeding-up and slowing-down to travel around the aircraft structure. At the Critical Mach number, local airflow in some areas near the airframe reaches the speed of sound, even though the aircraft itself has an airspeed lower than Mach 1. 0. This creates a weak shock wave. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called At speeds faster than the Critical Mach number:

• drag coefficient increases suddenly, causing dramatically increased drag [2]
• in aircraft not designed for transonic or supersonic speeds, changes to the airflow over the flight control surfaces lead to deterioration in control of the aircraft. The drag coefficient ( Cd, Cx or Cw) is a Dimensionless quantity that describes how streamlined an In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a Transonic is an Aeronautics term referring to a range of velocities just below and above the Speed of sound (about mach 0 For other uses see Supersonic. The term supersonic is used to define a speed that is over the Speed of sound ( Mach 1 Aircraft flight control surfaces allow a pilot to adjust and control the aircraft's flight attitude [2]

In aircraft not designed to fly at the Critical Mach number, shock waves in the flow over the wing and tailplane were sufficient to stall the wing, make control surfaces ineffective or lead to loss of control such as Mach tuck. Mach tuck is an Aerodynamic effect whereby the Nose of an Aircraft tends to pitch downwards as the airflow around the wing reaches Supersonic The phenomena associated with problems at the Critical Mach number became known as compressibility. In Thermodynamics and Fluid mechanics, compressibility is a measure of the relative volume change of a Fluid or Solid as a response Compressibility led to a number of accidents involving high-speed military and experimental aircraft in the 1930s and 1940s.

Although unknown at the time, compressibility was the cause of the phenomenon known as the sound barrier. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Subsonic aircraft such as the Supermarine Spitfire, BF 109, P-51 Mustang, Gloster Meteor, Me 262, P-80 have relatively thick, unswept wings and are incapable of reaching Mach 1. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 0. In 1947, Chuck Yeager flew the Bell X-1 to Mach 1. Charles Elwood "Chuck" Yeager (born February 13 1923 is a retired Brigadier-General in the United States Air Force and a noted Test pilot. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 0 and beyond, and the sound barrier was finally broken.

Early transonic military aircraft such as the Hawker Hunter and F-86 Sabre were designed to fly satisfactorily faster than their Critical Mach number. Transonic is an Aeronautics term referring to a range of velocities just below and above the Speed of sound (about mach 0 WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout They did not possess sufficient engine thrust to reach Mach 1. 0 in level flight but could be dived to Mach 1. 0 and beyond, and remain controllable. Modern passenger-carrying jet aircraft such as Airbus and Boeing aircraft have Maximum Operating Mach numbers slower than Mach 1. 0 but they are routinely operated faster than their Critical Mach numbers.

Supersonic aircraft, such as Concorde, the English Electric Lightning, Lockheed F-104, Dassault Mirage III, and MiG 21 are designed to exceed Mach 1. For other uses see Supersonic. The term supersonic is used to define a speed that is over the Speed of sound ( Mach 1 WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 0 in level flight. They have very thin wings. Their Critical Mach numbers are faster than those of subsonic and transonic aircraft but less than Mach 1. 0.

The actual Critical Mach number varies from wing to wing. In general a thicker wing will have a lower Critical Mach number, because a thicker wing accelerates the airflow to a faster speed than a thinner one. For instance, the fairly thick wing on the P-38 Lightning led to a Critical Mach number of about .69 Mach, a speed it could reach with some ease in dives, which led to a number of crashes. Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid The much thinner wing on the Supermarine Spitfire caused this aircraft to have a Critical Mach number of about 0. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout 89 Mach.

## References

• Clancy, L. J. (1975) Aerodynamics, Pitman Publishing Limited, London ISBN 0 273 01120 0

## Notes

1. ^ Clancy, L. J. Aerodynamics, Section 11. 6
2. ^ a b Clancy, L. J. , Aerodynamics, Chapter 11

## See also

Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid Mach tuck is an Aerodynamic effect whereby the Nose of an Aircraft tends to pitch downwards as the airflow around the wing reaches Supersonic Sound is a vibration that travels through an elastic medium as a Wave. Transonic is an Aeronautics term referring to a range of velocities just below and above the Speed of sound (about mach 0
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