Formers, frame assemblies, and bulkheads are the structural members
that give cross-sectional shape and strength to the construction.
Frame assemblies used to separate areas are reinforced, disc-shaped,
equipped with doors or access plates, and known as bulkheads.
Channel members, hat-shaped sections, and built-up assemblies give
the structure additional strength.
Stringers and longerons are the
principal lengthwise fuselage structural members.
These joined to
the formers, bulkheads, and assemblies make a rigid fuselage
framework.
Nacelles are used primarily to house engines on multiengine aircraft.
Generally, on twin-engine Army planes they house the main landing
gear.
Their repair fundamentals are essentially the same as for a
fuselage.
Nacelles must be kept within weight limits, built to
withstand compression and shear loads, and aerodynamically suited for
their location.
Wings on military airplanes are generally without
external bracing, and the skin is part of the wing structure,
carrying some of the wing stresses.
Monospar, multispar, and box-
beam are the basic wing-construction designs.
Monospar means that
one main longitudinal member is used.
The monospar wing is not in
common use.
Multispar wings have more than one main longitudinal
member, and box-beam wings have two with connecting bulkheads for
additional strength.
Spars, ribs, bulkheads, and stringers are
riveted or welded together.
Spars run from the wing's base to its
tip.
Webs are deep wall plates and with their attached capstrips
form the foundation for attaching the skin.
Ribs are a wing's
crosspieces, running from the leading edge to the trailing edge.
They give the wing its shape and transmit the load from the skin to
the spars.
Ribs are also used in ailerons, elevators, fins, and
stabilizers.
Lightening holes in former ribs lessen their weight
without decreasing their strength.
Reinforced and truss ribs are
heavier than former ribs and are only used at points where the
greatest stress is imposed.
The empennage, the aft end of the fuselage, consists of the rudder,
elevators, stabilizers, and trim tabs.
These empennage components
are usually of all-metal construction and cantilever design.
In
general, their construction features are the same as those of wings.
The vertical stabilizer helps maintain directional stability in
flight and supports the rudder.
The horizontal stabilizer helps
maintain stability about the airplane's lateral axis, and it is the
base for the elevators.
Airframe structure for helicopters is generally the same as
that for airplanes. The typical single-rotor helicopter
has two major sections: the cabin and tail cone. Basically,
the cabin structure is semimonocoque with strengthened high-stress
areas. The tail cone supports the tail rotor, tail-rotor
drive shafting, and stabilizers. The stabilizers give lateral and
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