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Pilot's Handbook of Aeronautical Knowledge
Aerodynamics of Flight
Axes of an Aircraft

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Pilot's Handbook of Aeronautical Knowledge



Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making




Axes of an airplane.
Figure 4-15. Axes of an airplane.

A pilot should not attempt to force an aircraft to become
airborne with a deficiency of speed. The manufacturer's
recommended takeoff speed is necessary to provide adequate
initial climb performance. It is also important that a definite
climb be established before a pilot retracts the landing gear
or flaps Never retract the landing gear or flaps prior to
establishing a positive rate of climb, and only after achieving
a safe altitude.

If, during the landing phase of flight, the aircraft is brought into
ground effect with a constant AOA, the aircraft experiences
an increase in CL and a reduction in the thrust required, and a
"floating" effect may occur. Because of the reduced drag and
power-off deceleration in ground effect, any excess speed at
the point of flare may incur a considerable "float" distance.
As the aircraft nears the point of touchdown, ground effect is
most realized at altitudes less than the wingspan. During the
final phases of the approach as the aircraft nears the ground,
a reduced power setting is necessary or the reduced thrust
required would allow the aircraft to climb above the desired
glidepath (GP).

Axes of an Aircraft

The axes of an aircraft are three imaginary lines that pass
through an aircraft's CG. The axes can be considered as
imaginary axles around which the aircraft turns. The three axes
pass through the CG at 90° angles to each other. The axis from
nose to tail is the longitudinal axis, the axis that passes from
wingtip to wingtip is the lateral axis, and the axis that passes
vertically through the CG is the vertical axis. Whenever an
aircraft changes its flight attitude or position in flight, it rotates
about one or more of the three axes. [Figure 4-15]

The aircraft's motion about its longitudinal axis resembles
the roll of a ship from side to side. In fact, the names
used to describe the motion about an aircraft's three axes
were originally nautical terms. They have been adapted to
aeronautical terminology due to the similarity of motion of
aircraft and seagoing ships. The motion about the aircraft's
longitudinal axis is "roll," the motion about its lateral axis is
"pitch," and the motion about its vertical axis is "yaw." Yaw
is the horizontal (left and right) movement of the aircraft's

The three motions of the conventional airplane (roll, pitch,
and yaw) are controlled by three control surfaces. Roll is
controlled by the ailerons; pitch is controlled by the elevators;
yaw is controlled by the rudder. The use of these controls
is explained in Chapter 5, Flight Controls. Other types of
aircraft may utilize different methods of controlling the
movements about the various axes.

For example, weight-shift control aircraft control two axes,
roll and pitch, using an "A" frame suspended from the
flexible wing attached to a three-wheeled carriage. These
aircraft are controlled by moving a horizontal bar (called a
control bar) in roughly the same way hang glider pilots fly.
[Figure 4-16] They are termed weight-shift control aircraft because the pilot controls the aircraft by shifting the CG.

For more information on weight-shift control aircraft, see
the Federal Aviation Administration (FAA) Weight-Shift
Control Flying Handbook, FAA-H-8083-5. In the case of
powered parachutes, aircraft control is accomplished by
altering the airfoil via steering lines.

A weight-shift control aircraft.
Figure 4-16. A weight-shift control aircraft.