Equivalent airspeed (EAS) is the airspeed which represents the same dynamic pressure at altitude that would be generated by flying at the corresponding true airspeed (TAS) at sea level. It is useful for predicting aircraft handling, aerodynamic loads, stalling etc. This article contains information that has not been verified and thus might not be reliable. ...
Where
standard air density is 1.225 kg/m³.
EAS can also be obtained from the aircraft mach number and static air pressure.
Where
astd is the standard speed of sound at 15 °C (661.47 knots)
Combining the above with the expression for Mach number as a function of impact and static pressures gives, for subsonic compresible flow: Mach number (Ma) (pronounced mack in British English and mock in American English) is defined as a ratio of the speed of an object or flow relative to the speed of sound in the medium through which it is travelling. ... Mach number (Ma) (pronounced mack in British English and mock in American English) is defined as a ratio of the speed of an object or flow relative to the speed of sound in the medium through which it is travelling. ...
Where
qc is impact pressure
At sea level EAS is the same as calibrated airspeed (CAS). At high altitude, EAS may be obtained from CAS by correcting for compressibility error. Calibrated airspeed (CAS) is indicated airspeed, corrected for instrument error and position error. ...
Equivalentairspeed (EAS) is calibrated airspeed corrected for error due to air compressibility which arises at high altitudes and mach numbers.
The significance of equivalentairspeed is that at Mach numbers below the onset of wave drag, all of the aerodynamic forces and moments on an aircraft scale with the square of the equivalentairspeed.
The equivalentairspeed is closely related to the Indicated airspeed speed shown by the airspeed indicator.
![EAS={a_{std}}sqrt{{5P_0 over P_{std}}[(frac{q_c}{P_0}+1)^frac{2}{7}-1]}](http://upload.wikimedia.org/math/d/a/c/dac4e3a5219dfbac455b62b479b8c8be.png)
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