An Introduction to the Airplane

Airplanes come in many different shapes and sizes depending on the mission of the aircraft, but all modern airplanes have certain components in common. These are the fuselage, wing, tail assembly and control surfaces, landing gear, and powerplant(s).

For any airplane to fly, it must be able to lift the weight of the airplane, its fuel, the passengers, and the cargo. The wings generate most of the lift to hold the plane in the air. To generate lift, the airplane must be pushed through the air. The engines, which are usually located beneath the wings, provide the thrust to push the airplane forward through the air.

The fuselage is the body of the airplane that holds all the pieces of the aircraft together and many of the other large components are attached to it. The fuselage is generally streamlined as much as possible to reduce drag. Designs for fuselages vary widely. The fuselage houses the cockpit where the pilot and flight crew sit and it provides areas for passengers and cargo. It may also carry armaments of various sorts. Some aircraft carry fuel in the fuselage; others carry the fuel in the wings. In addition, an engine may be housed in the fuselage.

The wing provides the principal lifting force of an airplane. Lift is obtained from the dynamic action of the wing with respect to the air. The cross-sectional shape of the wing as viewed from the side is known as the airfoil section. The planform shape of the wing (the shape of the wing as viewed from above) and placement of the wing on the fuselage (including the angle of incidence), as well as the airfoil section shape, depend upon the airplane mission and the best compromise necessary in the overall airplane design.

The control surfaces include all those moving surfaces of an airplane used for attitude, lift, and drag control. They include the tail assembly, the structures at the rear of the airplane that serve to control and maneuver the aircraft and structures forming part of and attached to the wing.

The tail usually has a fixed horizontal piece (called the horizontal stabilizer) and a fixed vertical piece (called the vertical stabilizer). The stabilizers provide stability for the aircraft—they keep it flying straight. The vertical stabilizer keeps the nose of the plane from swinging from side to side (called yaw), while the horizontal stabilizer prevents an up-and-down motion of the nose (called pitch). (On the Wright brothers' first successful aircraft, the horizontal stabilizer was placed in front of the wings. Such a configuration is called a canard after the French word for "duck").

The hinged part found on the trailing edge of the wing is called the aileron. It is used to roll the wings from side to side. Flaps are hinged or pivoted parts of the leading and/or trailing edges of the wing used to increase lift at reduced airspeeds, primarily at landing and takeoff. Spoilers are devices used to disrupt the airflow over the wing so as to reduce the lift on an airplane wing quickly. By operating independently on each wing, they may provide an alternate form of roll control. Slats at the front part of the wing are used at takeoff and landing to produce additional lift.

At the rear of both the aileron surfaces and elevators and rudders are small moving sections called trim tabs that are attached by hinges. Their function is to (1) balance the airplane if it is too nose heavy, tail heavy, or wing heavy to fly in a stable cruise condition; (2) maintain the elevator, rudder, and ailerons at whatever setting the pilot wishes without the pilot maintaining pressure on the controls; and (3) help move the elevators, rudder, and ailerons and thus relieve the pilot of the effort necessary to move the surfaces.

The landing gear, or undercarriage, supports the airplane when it is resting on the ground or in water and during the takeoff and landing. The gear may be fixed or retractable. The wheels of most airplanes are attached to shock-absorbing struts that use oil or air to cushion the blow of landing. Special types of landing gear include skis for snow and floats for water. For carrier landings, arrester hooks are used.

Forward motion, or thrust, is generated by a thrust-producing device or powerplant to sustain flight. The powerplant consists of the engine (and propeller, if present) and the related accessories. The main engine types are the reciprocating (or piston type), and the reaction, or jet, engine such as the ram jet, pulse jet, turbojet, turboprop, and rocket engine. The propeller converts the energy of a reciprocating engine's rotating crankshaft into a thrust force. Usually the engines are located in cowled pods hung beneath the wings, but some aircraft, like fighter aircraft, will have the engines buried in the fuselage.

Other configurations have sometime been used. For instance, the Wright brothers' 1903 Flyer had pusher propellers (propellers at the rear of the plane) and the elevators at the front of the aircraft. Many fighter aircraft also combine the horizontal stabilizer and elevator into a single stabilator surface. There are many possible aircraft configurations, but any configuration must provide for the four forces needed for flight.

—Dan Johnston

Sources:

“Parts of an Airplane.” NASA Glenn Research Center. http://www.grc.nasa.gov/WWW/K-12/airplane/airplane.html

Talay, Theodore A. Introduction to the Aerodynamics of Flight. SP-367, Scientific and Technical Information Office, National Aeronautics and Space Administration, Washington, D.C. 1975. Available at http://history.nasa.gov/SP-367/cover367.htm

Further Reading:

Smith, H.C. “Skip.” The Illustrated Guide to Aerodynamics. 2^nd edition. Blue Ridge Summit, Pa.: TAB Books, 1992.

Wegener, Peter P. What Makes Airplanes Fly? New York: Springer-Verlag, 1991.