[IMAGE
SimpleHost Webstats produced by Analog 4.15

Do you want to see a
CARD TRICK?

AIRPLANES

SPAMMERS CLICK HERE!

SPAM PAYMENT INFO

[IMAGE

[IMAGE

The Guillow's Supermarine Spitfire Kit #504
Wingspan: 40"

[IMAGE The Supermarine Spitfire is a British single-seat fighter aircraft that was used by the Royal Air Force and many other Allied countries throughout the Second World War. The Spitfire continued to be used as a front line fighter and in secondary roles into the 1950s. It was produced in greater numbers than any other British aircraft and was the only British fighter in continuous production throughout the war.

The Spitfire was designed as a short-range, high-performance interceptor aircraft by R. J. Mitchell, chief designer at Supermarine Aviation Works (which operated as a subsidiary of Vickers-Armstrong from 1928). Mitchell continued to refine the design until his death from cancer in 1937, whereupon his colleague Joseph Smith became chief designer. Where speed was seen as essential to carrying out the mission of home defence against enemy bombers, the Spitfire's thin cross-section elliptical wing allowed it a higher top speed than several contemporary fighters, including the Hawker Hurricane.

During the Battle of Britain (July - October 1940), the Spitfire was perceived by the public as the RAF fighter, though the more numerous Hawker Hurricane shouldered a greater proportion of the burden against the Luftwaffe. The Spitfire units had a lower attrition rate and a higher victory-to-loss ratio than those flying Hurricanes.

After the Battle of Britain, the Spitfire became the backbone of RAF Fighter Command, and saw action in the European, Mediterranean, Pacific and the South-East Asian theatres. Much loved by its pilots, the Spitfire served in several roles, including interceptor, photo-reconnaissance, fighter-bomber, carrier-based fighter, and trainer. It was built in many variants, using several wing configurations. Although the original airframe was designed to be powered by a Rolls-Royce Merlin engine producing 1,030 hp (768 kW), it was adaptable enough to use increasingly powerful Merlin and later Rolls-Royce Griffon engines producing up to 2,035 hp (1,520 kW).

R. J. Mitchell's 1931 design to meet Air Ministry specification F7/30 for a new and modern fighter capable of 250 mph (400 km/h), the Supermarine Type 224, resulted in an open-cockpit monoplane with bulky gull-wings and a large fixed, spatted undercarriage powered by the 600 horsepower (450 kW) evaporative-cooled Rolls-Royce Goshawk engine. This made its first flight in February 1934. The Type 224 was a big disappointment to Mitchell and his design team, who immediately embarked on a series of "cleaned-up" designs, using their experience with the Schneider Trophy seaplanes as a starting point. Of the seven designs tendered to F/30, the Gloster Gladiator biplane was accepted for service.

Mitchell had already begun working on a new aircraft, designated Type 300, based on the Type 224, but with a retractable undercarriage and the wingspan reduced by 6 ft (1.8 m). The Type 300 was submitted to the Air Ministry in July 1934, but again was not accepted. The design then evolved through a number of changes, including incorporating a faired, enclosed cockpit, oxygen-breathing apparatus, smaller and thinner wings, and the newly developed, more powerful Rolls-Royce PV-XII V-12 engine, later named the "Merlin". In November 1934, Mitchell, with the backing of Supermarine's owner, Vickers-Armstrong, started detailed design work on this refined version of the Type 300 and, on 1 December 1934, the Air Ministry issued a contract AM 361140/34, providing 10,000 pounds for the construction of Mitchell's improved F7/30 design. On 3 January 1935, the Air Ministry formalised the contract and a new Specification F10/35 was written around the aircraft.

[IMAGE In April 1935, the armament was changed from two .303 in (7.7 mm) Vickers machine guns in each wing to four .303 in (7.7 mm) Brownings, following a recommendation by Squadron Leader Ralph Sorley of the Operational Requirements section at the Air Ministry. On 5 March 1936, the prototype (K5054) took off on its first flight from Eastleigh Aerodrome (later Southampton Airport). At the controls was Captain Joseph "Mutt" Summers, chief test pilot for Vickers (Aviation) Ltd., who is quoted as saying "Don't touch anything" on landing. This eight-minute flight came four months after the maiden flight of the contemporary Hurricane.

K5054 was fitted with a new propeller, and Summers flew the aircraft on 10 March 1936; during this flight the undercarriage was retracted for the first time. After the fourth flight, a new engine was fitted, and Summers left the test-flying to his assistants, Jeffrey Quill and George Pickering. They soon discovered that the Spitfire was a very good aircraft, but not perfect. The rudder was over-sensitive and the top speed was just 330 mph (528 km/h), little faster than Sydney Camm's new Merlin-powered Hurricane. A new and better-shaped wooden propeller meant the Spitfire reached 348 mph (557 km/h) in level flight in mid-May, when Summers flew K5054 to RAF Martlesham Heath and handed the aircraft over to Squadron Leader Anderson of the Aeroplane & Armament Experimental Establishment (A&AEE). Here, Flight Lieutenant Humphrey Edwardes-Jones took over the prototype for the RAF. He had been given orders to fly the aircraft and then to make his report to the Air Ministry on landing. Edwardes-Jones's report was positive; his only request was that the Spitfire be equipped with an undercarriage position indicator. A week later, on 3 June 1936, the Air Ministry placed an order for 310 Spitfires, before any formal report had been issued by the A&AEE; interim reports were later issued on a piecemeal basis.

In the mid-1930s, aviation design teams worldwide started developing a new generation of all-metal, low-wing fighter aircraft. The French Dewoitine D.520 and Germany's Messerschmitt Bf 109, for example, were designed to take advantage of new techniques of monocoque construction and the availability of new high-powered, liquid-cooled, in-line aero engines. They also featured refinements such as retractable undercarriages, fully enclosed cockpits and low drag, all-metal wings (all introduced on civil airliners years before but slow to be adopted by the military, who favoured the simplicity and manoeuvrability of the biplane).

Mitchell's design aims were to create a well-balanced, high-performance bomber interceptor and fighter aircraft capable of fully exploiting the power of the Merlin engine, while being relatively easy to fly. At the time, no enemy fighters were expected to appear over Great Britain; to carry out the mission of home defence, the design was intended to climb quickly to meet enemy bombers.

[IMAGE The Spitfire's airframe was complex: the streamlined, semi-monocoque duralumin fuselage featured a large number of compound curves built up from a skeleton of 19 formers, also known as frames, starting from frame number one, immediately behind the propeller unit, to the tail unit attachment frame. The first four frames supported the glycol header tank and engine cowlings. Frame 5, to which the engine bearers were secured, supported the weight of the engine and accessories, and the loads imposed by the engine: this was a strengthened double frame which also incorporated the fireproof bulkhead and, in later versions of the Spitfire, the oil tank. This frame also tied the four main fuselage longerons to the rest of the airframe. Behind the bulkhead were five 'U' shaped half-frames which accommodated the fuel tanks and cockpit. The rear fuselage started at the eleventh frame, to which the pilot's seat and (later) armour plating was attached, and ended at the nineteenth, which was mounted at a slight forward angle just forward of the fin. Each of these nine frames were oval, reducing in size towards the tail, and incorporated several lightening holes to reduce their weight as much as possible without weakening them. The U-shaped frame 20 was the last frame of the fuselage proper and the frame to which the tail unit was attached. Frames 21, 22 and 23 formed the fin; frame 22 incorporated the tailwheel opening and frame 23 was the rudder post. Before being attached to the main fuselage, the tail unit frames were held in a jig and the eight horizontal tail formers were riveted to them.

A combination of 14 longitudinal stringers and four main longerons attached to the frames helped form a light but rigid structure to which sheets of alclad stressed skinning were attached. The fuselage plating was 24, 20 and 18 gauge in order of thickness towards the tail, while the fin structure was completed using short longerons from frames 20 to 23, before being covered in 22 gauge plating. There was ample room for the camera equipment and additional fuel tanks which were to be fitted during the Spitfire's operational service life. Supermarine Spitfire Mk XVIe side elevation drawing.

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 flush riveting was used on the fuselage, affecting all Spitfire variants. In some areas, such as at the rear of the wing, and the lower tailplane skins the top was riveted and the bottom fixed by brass screws which tapped into strips of spruce bolted to the lower ribs. The removable wing tips were made up of duralumin skinned spruce formers. At first the ailerons, elevators and rudder were fabric-covered. 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.

In 1934, Mitchell and the design staff decided to use a semi-elliptical wing shape to solve two conflicting requirements; the wing needed to be thin, to avoid creating too much drag, while still able to house a retractable undercarriage, plus armament and ammunition. Mitchell has sometimes been accused of copying the wing shape of the Heinkel He 70, which first flew in 1932; but as Beverly Shenstone, the aerodynamicist on Mitchell's team, explained "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."

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-chord, 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. Beverly Shenstone

The wing section used was from the NACA 2200 series, which had been adapted to create a thickness-to-chord ratio of 13% at the root, reducing to 9.4% at the tip. A dihedral of six degrees was adopted to give increased lateral stability.

[IMAGE A feature of the wing which contributed greatly to its success was an innovative spar 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 leaf spring; 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 Goshawk led to the adoption of a cooling system which used 100% glycol. The radiators were housed in a new radiator-duct designed by Fredrick Meredith of the RAE at Farnborough; this used the cooling air to generate thrust, greatly reducing the net drag produced by the radiators. In turn, the leading-edge structure lost its function as a condenser, but it was later adapted to house integral fuel tanks of various sizes.

Another feature of the wing was its washout. The trailing edge of the wing twisted slightly upward along its span, the angle of incidence decreasing from +2 degrees at its root to -1/2 degrees at its tip. This caused the wing roots to stall before the tips, reducing tip-stall that could otherwise have resulted in a spin. As the wing roots started to stall, the aircraft vibrated, warning the pilot, and hence allowing even relatively inexperienced pilots to fly the aircraft to the limits of its performance. 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 subcontractors, most of whom had never dealt with metal-structured, high-speed aircraft. By June 1939, most of these problems had been resolved, and 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 Battle of Britain, pilots found 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. 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.

The Build: CLICK IMAGES TO ENLARGE...

[IMAGE
[IMAGE
[IMAGE

[IMAGE
[IMAGE
[IMAGE

[IMAGE
[IMAGE
[IMAGE

[IMAGE
[IMAGE
[IMAGE

[IMAGE
[IMAGE
[IMAGE

[IMAGE
[IMAGE

Here's what you came to see:

[IMAGE
[IMAGE
[IMAGE

[IMAGE
[IMAGE

NEXT:

One of the 500 Series Planes Blown to 120"... Yep. ten feet... We just don't know which one yet... Stand by for further developments...

Parker Information Resources
Houston, Texas
E - mail: bparker@parkerinfo.com
[PIR]

The HTML Writers Guild
Notepad only
[raphael]
[hbd]
[Netscape]
[PIR]