The Wings
The
Wings
Wing
construction is basically the same in all types of aircraft. Most modern
aircraft have all metal wings, but many older aircraft had wood and fabric
wings. Ailerons and flaps will be studied later in this chapter.
To maintain its
all-important aerodynamic shape, a wing must be designed and built to hold its
shape even under extreme stress. Basically, the wing is a framework
composed chiefly of spars, ribs, and (possibly) stringers (see figure
1-5). 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 may have an additional purpose of bearing flight stress, and these
are called compression ribs.
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.
Three
systems are used to determine how wings are attached to the aircraft fuselage
depending on the strength of a wing's internal structure. 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 semicantilever
usually has one, or perhaps two, supporting wires or struts attached to each
wing and the fuselage. The externally braced wing is typical of the biplane
(two wings placed one above the other) with its struts and flying and landing
wires (see figure 1-6).
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