Britannica Student Encyclopedia - 2010

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

54 Airplane BRITANNICA STUDENT ENCYCLOPEDIA

 

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 plane’s 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 plane’s

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 plane’s 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 plane’s

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

farther—and therefore faster—than 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.

56 Airplane BRITANNICA STUDENT ENCYCLOPEDIA

 

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

unheated air.

The 1800s saw much experimentation

in both lighter-than-air and heavierthan-

air craft. Several people worked

with gliders to establish the principles of

airplane design. Gliders are similar to

airplanes but they have no motor. Once

they are launched, they move through

the air as a plane does.

Early Aviation

On December 17, 1903, in Kitty Hawk,

North Carolina, Orville andWilbur

Wright made the first flight in an

engine-powered airplane. TheWright

brothers had experimented with gliders.

They chose the North Carolina coast for

their testing because of its strong winds.

Their first plane flight, with Orville

piloting, lasted 12 seconds and covered

120 feet (37 meters). By 1905 the

Wright brothers had improved their

plane to the point that it could fly 24

miles (39 kilometers) in 38 minutes.

During WorldWar I (1914–18) airplanes

began to change the nature of

war. Planes were first used to observe the

enemy from the air. Eventually countries

discovered that they could use planes for

dropping bombs. Pilots also learned to

shoot at each other in the sky.