Read the text and check your answers for the questions in ex. 2.2

Wings: construction and functions.

The wings are airfoils attached to each side of the fuselage and are the main lifting surfaces that support the airplane in flight. There are numerous wing designs, sizes, and shapes used by the various manufacturers. Most modern aircraft have all metal wings, but many older aircraft had wood and fabric wings. 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 strongest wing structure is the full cantilever which is attached directly to the fuselage and does not have any type of external, stress-bearing structures. The semi cantilever usually has one, or perhaps two, supporting wires or struts attached to each wing and the fuselage. A few high-wing and most low-wing airplanes have a full cantilever wing designed to carry the loads without external struts. 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.

Figure1. Monoplane and biplane

Figure2.Wood-and-fabric-type wing structure

Figure3. Modern aircraft wings

To maintain its all-important aerodynamic shape, a wing must be designed and built to hold its shape even under extreme stress. So, the wing is a framework composed chiefly of spars, ribs, and (possibly) stringers. Spars are the main members of the wing. They extend lengthwise of the wing (crosswise of the fuselage). All the load carried by the wing is ultimately taken by the spars. In flight, the force of the air acts against the skin. From the skin, this force is transmitted to the ribs and then to the spars.

Most wing structures have two spars, the front spar and the rear spar. The front spar is found near the leading edge while the rear spar is about two-thirds the distance to the trailing edge. Depending on the design of the flight loads, some of the all-metal wings have as many as five spars. In addition to the main spars, there is a short structural member which is called an aileron spar.

The ribs are the parts of a wing which support the covering and provide the airfoil shape. These ribs are called forming ribs and their primary purpose is to provide shape. Some ribs may have an additional purpose of bearing flight stress, and these are called compression ribs. 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.

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.

The most simple wing structures will be found on light civilian aircraft. High-stress types of military aircraft will have the most complex and strongest wing structure.

Figure4.Wing and fuselage attachment