Editing Fuselage (section)

== Types of structures ==

[[File:Fuselage Piper PA18.JPG|thumb|[[Piper PA-18]] welded tube truss fuselage structure]]

=== Truss structure ===
{{Main|Truss}}
[[File:Truss-type fuselage structure.png|thumb|right|Some older types of aircraft design utilized open truss structure constructed of wood, steel, or aluminum tubing.<ref name="phak" />{{rp|3-3}}]]
This type of structure is still in use in many lightweight aircraft using [[welding|weld]]ed [[steel]] tube trusses.
A box truss fuselage structure can also be built out of wood—often covered with plywood. Simple box structures may be rounded by the addition of supported lightweight stringers, allowing the fabric covering to form a more aerodynamic shape, or one more pleasing to the eye.

=== Geodesic construction ===
{{Main|Geodetic airframe}}
[[File:Vickers Wellington Mark X, HE239 'NA-Y', of No. 428 Squadron RCAF (April 1943).png|thumb|The [[geodetic airframe]] of a [[Vickers Wellington]], visible as a result of damage sustained to the fuselage skin on the aircraft's tail]]

Geodesic 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. A similar construction using aluminum alloy was used in the [[Vickers Warwick]] with less material than would be required for other structural types. The geodesic structure is also redundant and so can survive localized damage without catastrophic failure. A fabric covering over the structure completed the aerodynamic shell (see the [[Vickers Wellington]] for an example of a large warplane which uses this process). The logical evolution of this is the creation of fuselages using molded plywood, in which several sheets are laid with the grain in differing directions to give the monocoque type below.

=== Monocoque shell ===
[[File:vans.rv-7.g-kels.arp.jpg|thumb|The [[Van's Aircraft RV-7]] of semi-monocoque construction]]

In this method, the exterior surface of the fuselage is also the primary structure. A typical early form of this (see the [[Lockheed Vega]]) was built using molded [[plywood]], where the layers of plywood are formed over a "plug" or within a [[Molding (process)|mold]]. A later form of this structure uses [[glass-reinforced plastic|fiberglass]] cloth impregnated with polyester or epoxy resin as the skin, instead of plywood. A simple form of this used in some amateur-built aircraft uses rigid expanded foam plastic as the core, with a fiberglass covering, eliminating the necessity of fabricating molds, but requiring more effort in finishing (see the [[Rutan VariEze]]). An example of a larger molded plywood aircraft is the [[de Havilland Mosquito]] fighter/light bomber of [[World War II]].
No plywood-skin fuselage is truly [[monocoque]], since stiffening elements are incorporated into the structure to carry concentrated loads that would otherwise buckle the thin skin.
The use of molded fiberglass using negative ("female") molds (which give a nearly finished product) is prevalent in the series production of many modern [[sailplane]]s. The use of molded composites for fuselage structures is being extended to large passenger aircraft such as the [[Boeing 787]] ''Dreamliner'' (using pressure-molding on female molds).

=== Semi-monocoque ===
{{Multiple image
| header = Monocoque and semi-monocoque design<ref name="phak">{{cite web |title=Pilot's Handbook of Aeronautical Knowledge |url=https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak |publisher=[[Federal Aviation Administration]] |access-date=16 January 2023 |date=August 24, 2016}}</ref>{{rp|3-9}}
| image1 = Monocoque fuselage design.png
| caption1 = Monocoque construction uses stressed skin to support almost all loads much like an aluminum beverage can.
| image2 = Semimonocoque fuselage design.png
| caption2 = Semi-monocoque construction, partial or one-half, uses a substructure to which the airplane's skin is attached.
}}

[[File:Fuselage-747.jpg|thumb|upright|Sectioned fuselage of a [[Boeing 747]] showing formers, [[Stringer (aeronautics)|stringers]] and skin all made of [[aluminium]]]]

This is the preferred method of constructing an all-[[aluminium|aluminum]] fuselage. First, a series of [[former]]s in the shape of the fuselage cross sections are held in position on a [[Fixture (tool)|rigid fixture]]. These formers are then joined with lightweight longitudinal elements called [[longeron|stringers]]. These are in turn covered with a skin of sheet aluminum, attached by [[rivet]]ing or by bonding with special adhesives. The fixture is then disassembled and removed from the completed fuselage shell, 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 [[fastener]]s 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 many identical aircraft are to be produced. Early examples of this type include the Douglas Aircraft [[Douglas DC-2|DC-2]] and [[Douglas DC-3|DC-3]] civil aircraft and the Boeing [[B-17 Flying Fortress]]. Most metal light aircraft are constructed using this process.

Both monocoque and semi-monocoque are referred to as "stressed skin" structures as all or a portion of the external load (i.e. from wings and empennage, and from discrete masses such as the engine) is taken by the surface covering. In addition, all the load from internal [[Cabin pressurization|pressurization]] is carried (as ''skin tension'') by the external skin.

The proportioning of loads between the components is a design choice dictated largely by the dimensions, strength, and elasticity of the components available for construction and whether or not a design is intended to be "self jigging", not requiring a complete fixture for alignment.