This page is intended for college, high school, or middle school students.
For younger students, a simpler explanation of the information on this page is
available on the
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 aerodynamic forces which affects the translation.
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
climbs (increases in altitude),
dives (decreases in altitude), or
banks (rolls to one side and turns).
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. A rotation is caused by
a force being
at some distance from the center of gravity.
When the aircraft is
trimmed, rotations caused by several forces are
balanced and the aircraft does not rotate.
Forces, Torques and Motion:
Basic Aircraft Motion:
- Beginner's Guide Home Page