Wings. Airplane surfaces designed to give lifting force when moved
forward rapidly through the air are wings. Wing design for any given
airplane depends upon size, weight, and use of the airplane; desired
speed in flight and at landing; and the desired rate of climb. Wings
are designated as left and right, corresponding to the left and right
hands of the pilot seated in the cockpit. Variations in design give
a wing its particular features. The wing tip may be square, rounded,
or tapered. Both the leading edge and the trailing edge of the wing
may be straight or curved.
Many types of modern airplanes have
swept-back wings.
Wings on military airplanes are generally of
cantilever design; that is, no external bracing is needed. Wings of
this design are usually of the stressed-skin type.
This means that
the skin is part of the wing structure and carries part of the wing
stresses.
Spar and Box-Beam Wings. In general, monospar, multispar, and box-
beam are the three basic wing-construction designs. Modifications of
these designs may be used by various manufacturers.
A separate
description of each basic design is given in the paragraphs that
follow.
The monospar wing has only one main longitudinal member in its
construction.
Ribs or bulkheads supply the necessary contour or
shape to the airfoil. The strict monospar wing is not in common use.
However, this design is modified by adding fake spars or light shear
webs along the trailing edge to support the control surfaces.
The multispar wing has more than one main longitudinal member in
its construction. To give the wing contour and relieve stress on the
wing's
skin,
ribs
or
bulkheads
are
often
included.
This
construction, or some modification of it, is used in lighter
airplanes.
The box-beam wing uses two main longitudinal members with
connecting bulkheads to give additional strength and contour to the
wing. A corrugated sheet of aluminum alloy may be placed between the
bulkheads and the smooth outer skin so that the wing can better carry
tension and compression loads.
Sometimes, heavy longitudinal
stiffeners are substituted for the corrugated sheets. A combination
of corrugated sheets on the upper surface of the wing and stiffeners
on the lower surface is sometimes used.
Wing Spars.
Figure 1-7 shows spars, ribs, bulkheads, stringers,
and stiffeners.
These, the wing's main structural components, are
riveted or welded together.
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