The Fuselage Structure

A. The fuselage is the main body of the aircraft. It usually serves the purposes of housing the crew, passengers and payload and of connecting the wing and the tail group. It may also carry fuel and support the engines and the landing gear. Its structure is called upon to carry bending, shear and torsion loads due to all these functions.

B. The usual constructions of a fuselage consist of longitudinal members (longerons), transverse rings (frames) and covering skin. The designer’s problem is complicated by the presence of doors, windows, wheel wells, bomb bays, etc.

C. A fuselage construction may be broken down into two main classes: the truss type consists of a welded tubular structure covered with skin and a girder type. The latter is divided into the monocoque type consisting of a strong outer skin from which the fuselage primarily derives its strength, and the semimonocoque type – the combination of a single shell structure with longerons and stringers to reinforce the skin.

D. A very common type of a fuselage is the monocoque type of construction. It is called so because it makes use of a single shell which is sufficient to provide the necessary structural strength. Monocoque construction aims at concentrating the structural material towards the outer surfaces and the success of stressed-skin fuselage depends upon the stiffness of the skin.

E. The semimonocoque type is the most popular fuselage construction. It presents the same outside appearance but instead of relying entirely on the skin for strength incorporates longerons or stringers usually riveted to the skin and carrying the main portion of the load. Thus it may be said that the longerons and the skin mutually reinforce each other.

F. The main longitudinal members, longerons, provide the basis of the necessary strength to resist bending together with transverse frames which are of a very light gauge metal. The transverse frames are rolled in channel or similar shape and spaced at intervals along the fuselage. The whole structure is covered with a very light gauge skin riveted in position. The longitudinal members in a semimonocoque fuselage are held apart by bulkheads, which give the fuselage its shape. Bulkheads are solid or semisolid frames placed where the greater stresses are to occur or at any point in the fuselage that requires special strength.

G. The skin is put on in long strips (or panels) riveted to each other and to the stringers and bulkheads. Both the monocoque and semimonocoque type structures are referred to as stressed-skin construction.

H. The fuselage is generally built in three sections or assemblies: the nose, the centre section and the aft section. When the assemblies are completed they are joined to form the entire fuselage.

Comprehension Check

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