Page 251 - Aircraft Stuctures for Engineering Student

232 Principles of stressed skin construction

and rudder of the British Aerospace Jaguar are fabricated from aluminium honey-
comb, while fibreglass and aluminium faced honeycomb are used extensively in the
wings and tail surfaces of the Boeing 747. Some problems, mainly disbonding and
internal corrosion, have been encountered in service.
The general principles relating to wing construction are applicable to fuselages,
with the exception that integral construction is not used in fuselages for obvious
reasons. Figures 7.7, 7.8 and 7.9 show that the same basic method of construction
is employed in aircraft having widely differing roles. Generally, the fuselage frames
that support large concentrated floor loads or loads from wing or tailplane attach-
ment points are heavier than lightly loaded frames and require stiffening, with
additional provision for transmitting the concentrated load into the frame and
hence the skin.
With the frames in position in the fuselage jig, stringers, passing through cut-outs,
are riveted to the frame flanges. Before the skin is riveted to the frames and stringers,
other subsidiary frames such as door and window frames are riveted or bolted in
position. The areas of the fuselage in the regions of these cut-outs are reinforced by
additional stringers, portions of frame and increased skin thickness, to react to the
high shear flows and direct stresses developed.
On completion, the various sub-assemblies are brought together for final assembly.
Fuselage sections are usually bolted together through flanges around their periph-
eries, while wings and the tailplane are attached to pick-up points on the relevant
fuselage frames. Wing spars on low wing civil aircraft usually pass completely
through the fuselage, simplifying wing design and the method of attachment. On
smaller, military aircraft, engine installations frequently prevent this so that wing
spars are attached directly to and terminate at the fuselage frame. Clearly, at these
positions frame/stringer/skin structures require reinforcement.

P.7.1 Review the historical development of the main materials of aircraft
construction.
P.7.2 Contrast and describe the contributions of the aluminium alloys and steel
to aircraft construction during the period 1945-70.
P.7.3 Examine possible uses of new materials in future aircraft manufacture.
P.7.4 Describe the main features of a stressed skin structure. Discuss the
structural functions of the various components with particular reference either to
the fuselage or to the wing of a medium sized transport aircraft.