We live in a world that is defined by three spatial dimensions and one
time dimension. Objects move within this domain in two ways.
or changes location, from one
point to another.
And an object
or changes its attitude.
In general, the motion of any object
involves both translation and rotation.
The translations are in direct response to external
The rotations are in direct response to external
torques or moments (twisting forces).
The motion of an
is particularly complex because the rotations and translations
are coupled together; a rotation affects the magnitude
and direction of the forces which affect translations.
To understand and describe the motion of an aircraft, we usually try
to break down the complex problem into a series of easier problems.
We can, for instance, assume that the aircraft translates from one
point to another as if all the mass of the aircraft were collected
into a single point called the
center of gravity.
We can describe the motion of the center of gravity by using
laws of motion. There are four
forces acting on the aircraft; the lift,
drag, thrust, and weight. Depending on the relative magnitudes and
directions of these forces, the aircraft will
climb (increase in altitude),
dive (decrease in altitude), or
bank (roll to one side).
The magnitude of the aerodynamic forces depends on the
of the aircraft during the translations. The attitude depends on
the rotations about the center of gravity when the aircraft is
- Re-Living the Wright Way
- Beginner's Guide to Aeronautics
- NASA Home Page