over the years. For example, the jet
engine was invented in the middle of the
1900s. This allowed planes to fly much
faster. Computer technology has also
helped in many ways. It has made it
possible to bomb faraway targets with
great accuracy. Computers are also used
to help train pilots to fly airplanes and
to keep airplanes on course.
#More to explore
Airplane Army Bomb Navy
Airplane
Humans have always envied birds for
their ability to fly. In the 1700s and
U.S. Air Force planes called F-16 Fighting
Falcons fly in formation.
The United
Kingdoms
Royal Air
Force was
formed in
1918. It was
the worlds first
air force.
52 Airplane BRITANNICA STUDENT ENCYCLOPEDIA
1800s humans flew in lighter-than-air
ships such as balloons, but not until
1903 did people build the first heavierthan-
air craftthe airplane.
The term airplane, which is often shortened
to plane, usually refers to any type
of power-driven aircraft that has fixed
wings and is heavier than air. An airplane
moves through the air with the
help of its engine and wings. The wings
are shaped in a particular way so that air
flows over them and gives them lift. By
contrast, balloons and airships are lifted
by gases that are lighter than air. Helicopters
are lifted by spinning blades.
Types of Airplanes
Airplanes can be grouped into many
different categories. One way of classifying
them is by the number of wings they
have. Many early airplanes were
biplanes, meaning that they had two
pairs of wings, one above the other.
Triplanes were also built in the early
days of aviation. Today most airplanes
are monoplanes, with one pair of wings.
Most airplanes take off and land from
dry land, but some operate on water.
Seaplanes have special landing gear that
supports them in the water.
Airplanes can also be grouped by their
purpose. Airplanes used for military
purposes by the armed forces include
fighters, bombers, spy planes, troop
transports, and tankers that refuel other
military planes while in flight. The
familiar airliners that carry large numbers
of people from city to city are called civil,
or commercial, aircraft.Other kinds of
Modern passenger airplanes can carry hundreds of people to almost anywhere in the world.
Seaplanes have special landing gear that
allow them to take off from and land on the
water.
BRITANNICA STUDENT ENCYCLOPEDIA Airplane 53
civil aircraft carry cargo. Still others are
flown by their owners as a hobby.
Parts of an Airplane
To understand how an airplane can fly,
it is first necessary to know its different
parts. The major parts are the airframe,
the power system, and the flight controls
and instruments.
Airframe
The airframe includes the fuselage,
wings, tail, and landing gear. The fuselage
is the body of the aircraft. It consists
of a rigid frame and a covering of aluminum,
magnesium, or molded plastic or
fiberglass.
The wings of an airplane have several
moving parts. Flaps and slats are hinged
parts that the pilot adjusts to increase
the size of the wing surface. This
changes the amount of force made by
the wing. Ailerons are hinged parts that
the pilot moves to turn the airplane.
The rear of the plane is called the tail.
The horizontal stabilizer is a part of the
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tail that often looks like a small wing. It
prevents the plane from pitching, or
bucking up and down. The elevator is
hinged to the horizontal stabilizer. It
raises or lowers the nose, or front end, of
the plane. The vertical stabilizer often
looks like a fin. It prevents the aircraft
from yawing, or swinging from side to
side. The rudder is connected to the
vertical stabilizer. It controls side-to-side
movement.
The landing gear consists of rubber tires
and shock-absorbing devices. Most
planes have two main wheels or sets of
wheels and another wheel to support the
tail. Some planes have wheels that fold
up when the plane is in the air.
Power System
A planes power system includes one or
more engines and sometimes propellers.
The two main types of engines are
reciprocating engines and jet engines. A
BRITANNICA STUDENT ENCYCLOPEDIA Airplane 55
reciprocating, or piston, engine turns a
propeller. The turning of the propeller
provides most of the power to move the
plane forward. Reciprocating engines
are usually found on smaller airplanes.
A jet engine moves a plane forward by
shooting exhaust gases out the back. Jet
engines are common on large
commercial planes and military aircraft.
Some small planes have a turboprop
engine, which is a jet engine that turns
a propeller.
Flight Controls and Instruments
Flight controls help a pilot to regulate
the movement and position of an airplane.
The control wheel or stick is used
to adjust the elevator and the ailerons.
Foot pedals allow the pilot to control the
rudder. A throttle controls the engine
power. The pilot also controls the wing
flaps and slats.
Flight instruments are used for navigation,
checking engine performance, and
monitoring other equipment. In addition
to these instruments, there are a
variety of indicators that monitor the
engines and other parts of the planes
mechanical and electrical systems.
How Airplanes Fly
The science of flight is called aerodynamics.
Four main aerodynamic forces
act on an airplane in flight. They are
called drag, thrust, gravity (or weight),
and lift.
As a plane flies, the air slows it down.
This is the effect of drag. To overcome
drag a plane needs the forward-moving
force of thrust. Thrust is produced by
the planes engines or propellers.
An airplane is heavier than air. It will fall
to the ground under the influence of
gravity unless lift is applied. The planes
wings are able to produce the necessary
lift because of their shape. The upper
surface is curved, while the lower surface
is flat. To get past the curved surface, the
air that flows over the wing has to go
fartherand therefore fasterthan the
air that flows under it. This creates a
difference in air pressure between the
upper and lower surfaces as the plane
moves forward. The air underneath is
under greater pressure and therefore
pushes the wing up. The faster the air
flows past the wings, the greater the lift.
For this reason, an airplane takes off
most easily when it faces the wind.
Pilots use flaps and slats to change the
amount of lift. Lowering the flaps
increases the curved surface of the wing,
which provides more lift for takeoff.
Slats also increase lift by allowing air to
flow more smoothly over the wing. Rais-
A plane with turboprop engine uses both jet
power and propellers. Turboprop engines
are used only in small planes.
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ing the flaps reduces lift, which slows
down the plane for landing.
History
Before humans took to the air in airplanes,
they flew in lighter-than-air
craft. In 1783 the Montgolfier brothers
of France made the first balloon that
could carry people high into the air.
Their balloon rose because they filled it
with hot air, which is lighter than