Manufacturing Exercise Involved in the Redesign of the Hawker Siddeley Trident (Tri-Jet) Fuselage

Abstract

The purpose of certain design studies was to examine the application of titanium construction to replace existing aluminium alloy structure using the same design loadings, applying the same structural philosophies, and accepting the same practical constraints on geometry. Under these design conditions weight savings result from the relative specific material properties of titanium alloys and aluminium alloy, the reduction in sizes permissible in titanium and, also from the exploitation of the weldability of titanium to produce more efficient configurations. Ti 8A1, 1Mo, 1V was specified (Duplex Annealed). The relatively thin fuselage skin (0.022 in.) was expected to be sufficiently free from stress corrosion hazards under aqueous conditions. Three particular areas were chosen for evaluation, viz., the sheet/stringer/frame structure in the keel area, the upper fuselage, and a window panel area. The usual attention was given to fatigue strength, critical crack length, and residual strength. Fusion welding was used whenever practicable, i.e., for skin to stringer joints and panel butt welds, with a little electrical resistance spot welding for the frame to fuselage skin attachment. The weight savings possible with the titanium design as compared with the aluminium structure were as follows:

• Fuselage keel area – 26.3%

• Upper fuselage area – 17.6%

• Window panel area – 28.0%

The overall weight saving on the complete fuselage section was 23.6%.