Aircraft Structures and the use of aerospace composites

The A310 fuselage is of semi-monocoque, fail-safe construction of circular cross-section, using aluminium alloys with improved stress corrosion and crack propagation behaviour. It is manufactured in nine structural sections (for ease of transportation) largely from sheet metal fabricated frames, open section stringers and skins.

In general, the skins are formed from simple sheet metal, except in highly loaded areas such as the centre fuselage at the wings and landing gear and the nose gear bay, where the skins are machined. Except where integrally machined, stringer attachment is by hot bonding or rivetting. The A310 is fitted with a tail bumper beneath the rear fuselage to protect the structure against excessive nose-up attitudes during take-off and landing.

Aerospace composite structures

A considerable amount of composites has been introduced, including glass-fibre reinforced plastic (GFRP), aramid-fibre reinforced plastic (ARFP) and carbon-fibre reinforced plastic (CRFP). These are used for floor struts and panels, spoilers, wing leading-edges lower access panels, wing/fuselage fairings, nosewheel doors, glide antenna cover, cooling air inlet fairings, main landing gear doors, flap track fairings and flap access doors, engine cowls and the complete fin box. The A310 was the first production aircraft to be certificated with a composite primary structure, starting with an A310-300 for Swissair in December 1985. A total of 13,6701b (6.2 tonnes) of composite material adds up to a weight saving of 3,0901b (1.4 tonnes) over a conventional metal structure. The fin box itself is 2551b (115kg) lighter and has 95 percent fewer components.

All areas of the fuselage are pressurised, except for the radome, the rear fuselage section (tailcone), the nose landing gear bay and the lower segment of the centre section, which includes the air conditioning, hydraulic and main landing gear bays. Each engine is supported on a pylon, which forms a failsafe box-type frame, constructed of high tensile steel. The attachment of the pylon to the wing consists of inner and outer triple-lugged titanium forge attachments, with two sets of twin steel links bolted to double lugs and to two pairs of titanium forged fittings attached to the forward face of the front wing spar and the wing skins.

A spherical stainless steel bearing transmits longitudinal and lateral loads to a titanium spigot forging bolted through the lower wing skin to the forward attachment fittings. The attachment of the engine to the pylon is via pyramid-shaped aero engine mountings machined from forged steel, which pick up the front spigot of the engine. This spigot transmits longitudinal and lateral loads, while four tension bolts carry the vertical loads.

Aircraft wings

The A310 wing has a thickness/chord ratio of 10.8 percent and a 28° sweepback and is made up of three main components providing a continuous and fail-safe two-spar box structure with machined skins and I-section stringers.

It is built mostly of high-strength aluminium alloy, except for the spoilers, outer shrouds, flap track fairings, flap access doors, leading edge lower access panels and wing/fuselage fairings, which are of composite materials. The centre wing box is built integrally into the fuselage, to which are attached the port and starboard cantilevered outer wing sections.