## 82 The gas turbine engine general principles

Although there are many variants of gas turbine-based aero engines, they operate using similar principles. Air is compressed by an axial flow or centrifugal compressor. The highly compressed air then passes to a combustion chamber where it is mixed with fuel and ignited. The mixture of air and combustion products expands into the turbine stage which in turn provides the power through a coupling shaft to drive the compressor. The expanding gases then pass out through the engine tailpipe,...

## 81 Propellers

A propeller or airscrew converts the torque of an engine (piston engine or turboprop) into thrust. Propeller blades have an airfoil section which becomes more 'circular' towards the hub. The torque of a rotating propeller imparts a rotational motion to the air flowing through it. Pressure is reduced in front of the blades and increased behind them, creating a rotating slipstream. Large masses of air pass through the propeller, but the velocity rise is small compared to that in turbojet and...

## Symbols and notations

Table 3.1 Important parameters and constants Planck's constant (h) Universal gas constant (R) Stefan-Boltzmann constant (ct) Acceleration due to gravity (g) Absolute zero Volume of 1 kg mol of ideal gas at 1 atm, 0 C Avagadro's number (N) Speed of sound at sea level (a0) Air temperature at sea level (T0) Air density at sea level (p0) 6.6260755 X 10-34 J s 8.314510 J mol K 5.67051 X 10-8 W m2 K4 9.80665 m s2 (32.17405 ft s2) -273.16 C (-459.688 F) 22.41 m3 6.023 X 1026 kg mol 340.29 m s (1116.44...

## 91 Aircraft roles and operational profile

Civil aircraft tend to be classified mainly by range. The way in which a civil aircraft operates is termed its operational profile. In the military field a more commonly used term is mission profile. Figure 9.1 shows a typical example and Table 9.1 some commonly used terms. Relevant formulae used during the various stages of the operational profile are Cflof 2 This is derived from (ia)dVz J0 Total take-off distance Sto (SG)(Fpi) where Fp1 is a 'take-off' plane form coefficient between about 1.1...

## 41 Forces and moments

Forces and moments play an important part in the science of aeronautics. The basic definitions Weight of aircraft acting vertically downwards. Force exerted (on an aircraft) by virtue of the diversion of an airstream from its original path. It is divided into three components lift, drag and lateral. Force component perpendicularly 'upwards' to the flight direction. Force component in the opposite direction to flight. Total drag is subdivided into pressure drag and surface friction drag. Force...

## Xdx Xx XX Xx XX fX Xx XX Xv XXX

A matrix which has an array of m X n numbers arranged in m rows and n columns is called an m X n matrix. It is denoted by This is a matrix having the same number of rows and columns. This is a square matrix in which all the elements are zero except those in the leading diagonal. This is a diagonal matrix with the elements in the leading diagonal all equal to 1. All other elements are 0. The unit matrix is denoted by I. Two matrices may be added provided that they are of the same order. This is...