ABSTRACT
The structure of the fuselage of a commercial transport aircraft is like the hull of a boat. Its section is roughly circular and varies in diameter along its length with the maximum diameter near the wing root position. If the aircraft is pressurised, airtight bulkheads are fitted near the front and rear of the fuselage. Both forward and rear pressure bulkheads are dish-shaped structures made of sheet with substantial radial and circumferential stiffening members. The age-hardening aluminium-copper alloys discovered in 1911, usually containing some magnesium, provide the combination of strength, stiffness, toughness and low density ideal for aircraft structures. Service life and the passage of time cause aircraft structures to deteriorate until they ultimately reach a condition when they are no longer airworthy. The lifespan of an aircraft, like that of a house or a human being, depends critically on how well it is inspected and maintained.
