Britannica Student Encyclopedia - 2010

as photosynthesis. Plants break down

the molecule, use the carbon, and then

release the oxygen into the air. In this

way the carbon dioxide and oxygen in

the air are constantly used and replaced.

#More to explore

Atmosphere • Molecule • Photosynthesis

Air Force

An air force is the part of a country’s

military that conducts warfare in the

skies. Its pilots fly airplanes and other

aircraft armed with weapons. They use

these aircraft to attack enemy aircraft as

A kite takes flight on a windy day.

BRITANNICA STUDENT ENCYCLOPEDIA Air Force 51

 

well as targets on the ground and in the

water, mostly during wars.

An air force is usually one of several

branches of a country’s military. In the

United States the other major branches

are the Army and the Navy (which

includes the Marine Corps).

Basic Functions and Aircraft

Most air forces perform a variety of military

functions, or jobs. During wars an

air force uses aircraft to observe the

enemy’s activities. It also gathers information

about possible battlefields and

targets.

Another basic job of an air force is to

gain control of the air over a particular

area. To do this, it uses aircraft called

fighters to drive away or destroy enemy

aircraft. Fighters are jet airplanes

designed to fly very fast. They can also

change direction quickly. Fighters carry

missiles, machine guns, or other weapons

on board.

An air force also uses aircraft to drop

bombs. It often uses large aircraft called

bombers to bomb targets in an enemy’s

country. It uses attack aircraft to help its

country’s troops fighting on the ground.

Pilots fly attack aircraft close to the

ground while bombing or shooting at

enemy troops below. Attack aircraft are

smaller and lighter than bombers.

Another duty of an air force is to move

troops and military supplies from place

to place. It normally uses helicopters or

large transport planes to do this.

History

Inventors created the first successful

airplanes in the early 1900s. Several

European countries used fighter aircraft

and bombers duringWorldWar I, from

1914 to 1918. Air warfare was a major

part ofWorldWar II in the 1940s.

Air forces have used many new inventions

to improve their aircraft and weapons

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

Kingdom’s

Royal Air

Force was

formed in

1918. It was

the world’s 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 craft—the 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