Some excerpts taken from the book:
Pressure Instruments
CHAPTER 11
THE AIR SPEED INDICATOR
The speed of a land vehicle is generally associated with the speed of the adjacent traffic relative to the observer who is seated in the vehicle. The higher such a relative velocity is the faster the vehicle must be. In marine transport, the speed of a ship is measured according to the motion of underneath water- current relative to the ship. Similarly, in air navigation, the air speed of an aircraft is based on the relative motion of air current, which is surrounding it.
An Air Speed Indicator (ASI) is the DR reference for the aircraft Indicated Air Speed (fig. 11.1). Indicated Air Speed (IAS) becomes unrealistic when the boundary layer of the air is detached from the aerofoil. This is one of the reasons for having un- cumbered sweep- back aerofoil on faster aircrafts.
Assuming an undisturbed air- boundary layer, therefore, the accuracy of the ASI may be accounted for by the terms of equation (8.15).
11.1. Dynamic Pressure.
According to the wind- tunnel experiments, air at speeds of
11.3. Problem Solution.
The following examples are intended to illustrate the meteorological definitions found in sections 11.1 to 11.2.1.
Question 1.
State precisely how the speed of sound varies with temperature. An aircraft is at F.L.350, TAS 462kts and mach 0.79 when the temperature deviation is 9 C relative to the jet atmosphere. Without using a computer, give the temperature deviation at F.L.310, which at mach 0.79 would give the same TAS 462.
C.P.L. [10]