
Ch04-H6927.tex 20/6/2007 16: 33 Page 66
Chapter 4
The Equations of Motion
4.1 THE EQUATIONS OF MOTION OF A RIGID SYMMETRIC AIRCRAFT
As stated in Chapter 1, the first formal derivation of the equations of motion for a rigid
symmetric aircraft is usually attributed to Bryan (1911). His treatment, with very few
changes, remains in use today and provides the basis for the following development.
The object is to realise Newton’s second law of motion for each of the six degrees of
freedom which simply states that,
mass × acceleration = disturbing force (4.1)
For the rotary degrees of freedom the mass and acceleration become moment of
inertia and angular acceleration ...