Fuselage
From Wikipedia, the free encyclopedia
The fuselage (from the French fuselé "spindle-shaped") is an aircraft's main body section that holds crew and passengers or cargo. In single engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage. The fuselage also serves to position control and stabilization surfaces in specific relationships to lifting surfaces, required for aircraft stability and maneuverability.
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[edit] Types of structures
[edit] Box truss structure
The structural elements resemble those of a bridge, with emphasis on using linked triangular elements. The aerodyamic shape is completed by additional elements called formers and stringers and is then covered with fabric and painted. Most early aircraft used this technique with wood and wire trusses and this type of structure is still in use in many lightweight aircraft using welded steel tube trusses. This method is especially suitable for amateur-built aircraft kits, where a complete welded truss structure is delivered with the fitting of other components, covering, and finishing completed by the user, as it ensures that a robust, uniform load bearing structure is within the completed aircraft.
[edit] Geodesic construction
structural elements were used by Barnes Wallis for British Vickers between the wars and into World War II to form the whole of the fuselage, including its aerodynamic shape. In this type of construction multiple flat strip stringers are wound about the formers in opposite spiral directions, forming a basket-like appearance. This proved to be light, strong, and rigid and had the advantage of being made almost entirely of wood. The structure is also redundant and so can survive localized damage without catastrophic failure. A fabric covering over the structure completed the aerodynamic shell. The logical evolution of this is the creation of fuselages using molded plywood, in which multiple sheets are laid with the grain in differing directions to give the monocoque type below.
[edit] Monocoque shell
In this, the exterior surface of the fuselage is also the primary structure. A typical early form of this was built using moulded plywood, where the layers of plywood are formed over a "plug" or within a mold, A later form of this structure uses fiberglass cloth impregnated with polyester or epoxy resin. A simple form of this used in some amateur-built aircraft uses rigid expanded foam plastic with a fiberglass covering, eliminating the necessity of fabricating molds, but requiring more effort in finishing. An example of a moulded plywood aircraft is the de Havilland Mosquito fighter/light bomber of World War II. The use of molded fiberglass using negative molds (which give a nearly finished product) is prevalent in the series production of many modern sailplanes. The use of molded composites for fuselage structures is being extended to large passenger aircraft such as the Boeing 787 Dreamliner.
[edit] Semi-monocoque
This is the preferred method of constructing an all-aluminum fuselage. First, a series of frames in the shape of the fuselage cross sections are held in position on a rigid fixture. These frames are then joined with lightweight longitudinal elements called stringers. These are in turn covered with a skin of sheet aluminum, attached by riveting or by bonding with special adhesives. The fixture is then disassembled and removed from the fuseleage, which is then fitted out with wiring, controls, and interior equipment such as seats and luggage bins. Most modern large aircraft are built using this technique, but use several large sections constructed in this fashion which are then joined with fasteners to form the complete fuselage. As the accuracy of the final product is determined largely by the costly fixture, this form is suitable for series production, where a large number of identical aircraft are to be produced. Early examples of this type include the Douglas Aircraft DC-2 and DC-3 civil aircraft and the Boeing B-17 Flying Fortress.
Both monocoque and semi-monocoque are referred to as "stressed skin" structures as all or a portion of the load is taken by the surface covering.
[edit] Exceptions
"Flying wing" aircraft, such as the Northrop YB-49 Flying Wing and the Northrop B-2 Spirit bomber have no separate fuselage; instead what would be the fuselage is a thickened portion of the wing structure.
Conversely there have been a small number of aircraft designs which have no wing per se but use the fuselage to generate lift. Examples include NASA's experimental lifting body designs and the Vought XF5U-1 Flying Flapjack.
