Wings
may be attached at the top, middle, or lower portion of the fuselage.
These designs are referred to as high-, mid-, and low-wing,
respectively. The number of wings can also vary. Airplanes with a single
set of wings are referred to as monoplanes, while those with two sets
are called biplanes. [Figure 1-5]Many high-wing airplanes have external braces, or wing struts, which transmit the flight and landing loads through the struts to the main fuselage structure. Since the wing struts are usually attached approximately halfway out on the wing, this type of wing structure is called semi-cantilever. A few high-wing and most low-wing airplanes have a full cantilever wing designed to carry the loads without external struts.
The
principal structural parts of the wing are spars, ribs, and stringers.
[Figure 1-6] These are reinforced by trusses, I-beams, tubing, or other
devices, including the skin. The wing ribs determine the shape and
thickness of the wing (airfoil). In most modern airplanes, the fuel
tanks either are an integral part of the wing’s structure, or consist of
flexible containers mounted inside of the wing.Attached to the rear, or trailing, edges of the wings are two types of control surfaces referred to as ailerons and flaps. Ailerons extend from about the midpoint of each wing outward toward the tip and move in opposite directions to create aerodynamic forces that cause the airplane to roll. Flaps extend outward from the fuselage to near the midpoint of each wing. The flaps are normally flush with the wing’s surface during cruising flight. When extended, the flaps move simultaneously downward to increase the lifting force of the wing for takeoffs and landings.
Airfoil—An airfoil is any surface, such as a wing, propeller, rudder, or even a trim tab, which provides aerodynamic force when it interacts with a moving stream of air. Monoplane—An airplane that has only one main lifting surface or wing, usually divided into two parts by the fuselage.
Biplane—An airplane that has two main airfoil surfaces or wings on each side of the fuselage, one placed above the other.
