Wednesday, May 22, 2013

Air speed

Introduction :
It is the speed of an air related to the aircraft among them the qualifying airspeed are Calibrated airspeed, Indicated aircraft, Equivalent air speed, true airspeed and finally the density airspeed. This aircraft speed is measured by the airspeed indicator which is shortly and popularly known as ASI. These are connected to the pitot static system. Types of the airspeed are Indicated airspeed, Calibrated airspeed, Equivalent airspeed, True airspeed. In this article we will know types of articles and how to calculate the airspeed.

Air speed Types

Indicated airspeed is abbreviated as IAS. This indicator reads directly form the airspeed indicator by the pitot static system on the aircraft. This is the airspeed related to the CAS that is calibrated airspeed it is corrected for the installation errors and the instrument.

These IAS are very much important for the pilots for the various purposes like calculation of the limited speeds and so on. This plays an important role in the airspeed.

Calibrated air speed is for the instrument errors and position errors and the installation errors. This equation shows the installation and the minus position.
Where, Vc is the calibrated airspeed
qc is the impact pressure
Po is static air pressure. Measures 29.92126 inches Hg at sea level.
ao is speed of sound. Measures 661.4788 knots at standard sea level.
air speed

Equivalent & True airspeed

Equivalent airspeed: This produces dynamic pressure as the true speed at the altitude where the vehicle is flying. It is forward to the flight for the effects of compressibility. Compressible impact pressure makes a function of calibrated airspeed. At standard sea level equivalent airspeed and calibrated airspeed are equal.

True airspeed is also called as TAS, it is the physical speed of the aircraft. The relation between true airspped and speed is Vg.
Vt = Vg - Vw
Where Vw is the wind speed vector.
To compute true airspeed using a function of mach number
Vt = ao.M`sqrt(T/(To))`
Where:
ao= Speed of sound(661.4788 knots) at standard sea level
M = Mach number
T = Temperature in kelvins
To= (288.15 kelvins)Standard sea level temperature

No comments:

Post a Comment