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Aircraft have changed out of all recognition in little more than a century since the first flight. During that relatively short period of history there has been a few aircraft that are recognised far beyond the world of aviation enthusiasts, but one stands alone as an icon of aviation - the Supermarine Spitfire.
By the early 1930s the biplane that had dominated the early decades of flight was becoming obsolete, replaced by the monoplane. This was aided by the advent of the all-metal semi-monocoque as the preferred method of construction, especially for fighter aircraft, as more powerful engines became available and speeds rose.
Replacing tubes and canvas, this new construction was more demanding when building the aircraft, but it delivered better aerodynamics and higher performance.
The potential of aluminium for airborne construction had been evident since 1903, when German metallurgist Alfred Wilm discovered that after quenching, an aluminium alloy containing 4% copper would harden slowly when left at room temperature for several days. Duralumin, also known by several other trade names, is today mainly used to describe aluminium-copper alloys, designated as the '2000' series by the International Alloy Designation System (IADS).
Its first use was in rigid airship frames of the 'Great Airship' era of the 1920s and 1930s. Duralumin quickly spread throughout the aircraft industry in the early 1930s, and was used by Spitfire designer Reginald Mitchell in his successful racing seaplanes of the 1930s.
A notable feature of the Spitfire design was its distinctive elliptical wing. Thin, to reduce drag, the wing still needed to house the retracted wheels and armaments. It also needed to be strong to enable high speeds when diving, and Mitchell's solution was...