Supermarine Spitfire

The skins of the fuselage, wings and tailplane were secured by rivets and, in critical areas such as the wing forward of the main spar where an uninterrupted airflow was required, with flush rivets; the fuselage used standard dome-headed riveting.

From February 1943 on, flush riveting was used on the fuselage, affecting all Spitfire variants.

In some areas, such as the rear of the wing, the top was riveted and the bottom fixed by woodscrews into sections of [Vous devez être inscrit et connecté pour voir ce lien]; later, [Vous devez être inscrit et connecté pour voir ce lien] would be used for these areas.

At first, the ailerons, elevators and rudder were fabric-covered. However, when combat experience showed that fabric-covered ailerons were impossible to use at high speeds, fabric was replaced with a light alloy, enhancing control throughout the speed range.

Elliptical wing design


In 1934 Mitchell and the design staff decided to use an elliptical wing shape to solve two conflicting requirements; the wing needed to be thin, to avoid creating too much [Vous devez être inscrit et connecté pour voir ce lien], while still able to house a retractable undercarriage, plus armament and ammunition.

Beverley Shenstone, the aerodynamicist on Mitchell's team, explained the wing's qualities;

The elliptical wing was decided upon quite early on. Aerodynamically it was the best for our purpose because the induced drag, that caused in producing lift, was lowest when this shape was used: the ellipse was...theoretically a perfection...

To reduce drag we wanted the lowest possible thickness-to-[Vous devez être inscrit et connecté pour voir ce lien], consistent with the necessary strength.

But near the root the wing had to be thick enough to accommodate the retracted undercarriages and the guns...

Mitchell was an intensely practical man...

The ellipse was simply the shape that allowed us the thinnest possible wing with room inside to carry the necessary
structure and the things we wanted to cram in. And it looked nice.

Vue en coupe d'un Seafire, même principe pour l' aile

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Mitchell has sometimes been accused of copying the wing shape of the [Vous devez être inscrit et connecté pour voir ce lien], which first flew in 1932.

As Shenstone explained;

It has been suggested that we at Supermarine had cribbed the elliptical wing shape from that of the German Heinkel 70 transport.

This was not so...Our wing was much thinner and had quite a different section to that of the Heinkel.

In any case it would have been simply asking for trouble to have copied a wing shape from an aircraft designed for an entirely different purpose.^{[Vous devez être inscrit et connecté pour voir ce lien]}

The wing section used was from the [Vous devez être inscrit et connecté pour voir ce lien], which had been adapted to create a thickness-to-chord ratio of 13% at the root, reducing to 6% at the tip.

A [Vous devez être inscrit et connecté pour voir ce lien] of six degrees was adopted to give increased lateral stability.

Un lien renvoyant sur le site Spitfire 3d ( naca 2200 )

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A feature of the wing which contributed greatly to its success was an innovative [Vous devez être inscrit et connecté pour voir ce lien] boom design, made up of five square tubes which fitted into each other.

As the wing thinned out along its span the tubes were progressively cut away in a similar fashion to a [Vous devez être inscrit et connecté pour voir ce lien]; two of these booms were linked together by an alloy web, creating a lightweight and very strong main spar.

The undercarriage legs were attached to pivot points built into the inner, rear section of the main spar and retracted outwards and slightly backwards into wells in the non-load-carrying wing structure.

The resultant narrow undercarriage track was considered to be an acceptable compromise as this reduced the bending loads on the main-spar during landing.

Ahead of the spar, the thick-skinned leading edge of the wing formed a strong and rigid D-shaped box, which took most of the wing loads.

At the time the wing was designed, this D-shaped leading edge was intended to house steam condensers for the
evaporative cooling system intended for the PV-XII.

Constant problems with the evaporative system in the [Vous devez être inscrit et connecté pour voir ce lien] led to the adoption of a cooling system which used 100% [Vous devez être inscrit et connecté pour voir ce lien].

The radiators were housed in a new radiator-duct designed by [Vous devez être inscrit et connecté pour voir ce lien] of the [Vous devez être inscrit et connecté pour voir ce lien] at [Vous devez être inscrit et connecté pour voir ce lien]; this used the [Vous devez être inscrit et connecté pour voir ce lien], greatly reducing the net drag produced by the radiators.

In turn the leading-edge structure lost its function as an condenser, but it was later to be adapted to house integral fuel tanks of various sizes.

Another feature of the wing was its [Vous devez être inscrit et connecté pour voir ce lien].

The trailing edge of the wing twisted slightly upward along its span, the [Vous devez être inscrit et connecté pour voir ce lien] decreased from +2° at its root to -½° at its tip.

This caused the wing roots to [Vous devez être inscrit et connecté pour voir ce lien] before the tips, reducing tip-stall that may have resulted in a spin.

This washout was first featured in the wing of the Type 224 and became a consistent feature in subsequent designs leading to the Spitfire.

The complexity of the wing design, especially the precision required to manufacture the vital spar and leading-edge structures, at first caused some major hold-ups in the production of the Spitfire.

The problems increased when the work was put out to sub-contractors, most of whom had never dealt with metal-structured, high-speed aircraft. By June 1939 most of these problems had been resolved and Spitfire production was no longer held up by a lack of wings.

All of the main flight controls were originally metal structures with fabric covering.

Designers and pilots felt that having ailerons which were too heavy to move at high speed would avoid possible aileron reversal, stopping pilots throwing the aircraft around and pulling the wings off.

It was also felt that air combat would take place at relatively low speed and that high-speed manoeuvring would be
physically impossible.

During the [Vous devez être inscrit et connecté pour voir ce lien] pilots found that the ailerons of the Spitfire were far too heavy at high speeds, severely restricting lateral manoeuvres such as rolls and high speed turns, which were still a feature of air-to-air combat.

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Flight tests showed the fabric covering of the ailerons "ballooned" at high speeds, adversely affecting the aerodynamics.

Replacing the fabric covering with light alloy dramatically improved the ailerons at high speed

There were two main variations on the normal elliptical wing shape; when the Spitfire took on a role as a high altitude fighter (Marks VI and VII and some early Mk VIIIs) the standard wingtips were replaced by extended, "pointed" tips which increased the wingspan to 40 ft 2 in (12.3 m).

The other wingtip variation, used by several Spitfire variants, was the "clipped" wing; the standard wingtips were replaced by short fairings which reduced the span to 32 ft 6 in (9.9 m)