Supermarine Spitfire

The Supermarine Spitfire was a single seat fighter used by the RAF and many Allied countries in World War II.

Supermarine Chief Designer R.J. Mitchell had won three Schneider Trophy seaplane races with his aircraft, by combining powerful Napier or Rolls Royce engines with minute attention to streamlining[?]. These same qualities are equally useful for a fighter design, and in 1930 Mitchell produced such a plane in response to an Air Ministry request for a new and modern monoplane fighter.

This first attempt at a fighter resulted in a open-cockpit monoplane with gull-wings and a large fixed spatted undercarriage. The Supermarine Type 224 did not live up to expectations; nor did any of the competing designs which were also deemed failures.

Mitchell immedately turned his attention to an improved design as a private venture, with the backing of Supermarine owners Vickers. The new design added gear retraction, an enclosed cockpit, oxygen gear, and the much more powerful Rolls Royce PV-12 engine.

By 1935 the Air Ministry had seen enough advancement in the industry to try the monoplane design again. They eventually rejected the new Supermarine design on the grounds that it did not carry the required eight-gun load, and didn't appear to have room to do so.

Once again Mitchell was able to solve the problem. Looking at various Heinkel[?] planes he settled on the use of an eliptical planform, which had much more chord to allow for the required eight-guns, while still having the low drag of the earlier, simpler wing design. This was enough to sell the Air Ministry on this new Type 300, which they funded as F.10/35.

The prototype first flew on March 5, 1936. Performance was such that the Air Ministry immediately placed an order for 310. At the time it was still being "shaken out" by Vickers test pilots, even before the aircraft had been handed to them for their own flight testing.

Spitfire Mk.I

It was becoming clear that the new design was going to be the best British fighter available, and unlike the Hawker Hurricane, it appeared to have immense room for future improvement. Realizing that the initial order for 310 was but the first of what was likely to be a long production run, Vickers started construction of a huge new factory in Castle Bromwich to build Spitfires (in addition to their existing line in Woolston).

In 1938 their forward thinking paid off, when the Air Ministry placed an order for an additional 1000 Spitfires from the new factory. It was followed in 1939 by an order for another 200 from the Woolston factory, and only a few months later, another 450. This brought the total to 2,160, making it one of the largest buys in history.

The Woolston line started delivering the Mk.I Spitfire in late 1937, with front-line service commencing in August 1938. The Mk.I was powered by the 1,030hp Merlin Mk.II engine driving a two-blade wooden fixed pitch propeller. Only 77 had been completed before a three-bladed, two-position metal propeller was substituted, which greatly improved performance.

By the opening of the war, only a few units were equipped with the Spitfire, and the Hurricane would be the only fighter to see action in mainland Europe. However by the opening of the Battle of Britain in July 1940 the supply issue had improved to the point where 19 squadrons were flying Spitfires, while another 27 were equipped with Hurricanes. By the end of the battle in October, 565 Hurricanes and 352 Spitfires had been lost.

But by this point the factories were at full production and the losses could easily be replaced (not so the pilots however). Production of the Hurricane as a front-line fighter was ramped down.

During the battle, 19 Squadron received several cannon-armed Spitfires, known as the Mk.IB (the eight-gun versions retroactively becoming the Mk.IA). The cannon's hitting power was recognised, but jamming was a serious problem. Nevertheless, further cannon-armed Spitfires were issued to 92 Squadron and it was eventually realised that the best mix was an aircraft with two cannon and four machine guns.

In all, 1,583 of the original 2,160 Mk.I's were delivered, before production instead switched to the updated Mk.II.

Mk.II

With the end of the Battle of Britain the RAF gained some breathing room over the winter of 1940/41. They took this opportunity to work several additions into the production lines, creating the Type 329 Spitfire Mk.II.

Chief among the changes was the upgraded 1,175hp Merlin XII engine. The added power boosted top speed by 15 knots, and improved climb rate somewhat. The climb rate would have been improved further if not for the addition of 75 pounds of armor plating around the pilot.

The Mk.II was produced both in the IIA eight-gun and IIB cannon armed versions. Deliveries were very rapid, and they quickly replaced all remaining Mk.I's in service, which were then sent to training conversion units. The entire RAF had re-equipped with the new version by April 1941, and a total of 920 were built.

Mk.III and Mk.IV

With the Mk.II proving a match for the Luftwaffe fighters, the RAF asked Supermarine for much more ambitious upgrades to the basic design. Two proposals resulted.

The Mk.III was an aiframe improvement, strengthening the design overall, adding additional covers and fillets over various openings, and allowing the tailwheel to retract. Combined with the improved Merlin XX engine, it was expected that the Mk.III would gain considerable airspeed and be able to fly at just over 400 knots.

The Mk.IV was much more radical. Although it was based on a similar airframe to the Mk.III, it also included the new Rolls Royce Griffon[?] engine with over 1,500hp available. This extra power not only boosted the speed to over 420 knots, but allowed for a much heavier six-cannon armament. The Mk.IV appeared so promising that Mk.III was abandoned in its favour. Plans were made to have the new design reaching squadron service in October, becoming the standard RAF fighter by the start of 1942, but it was not to be.

Mk.V

Late in 1940 the Mk.II started meeting a new German aircraft in combat. Essentially a cleaned up version of the Bf 109E that Spitfires and Hurricanes had bested the year before in the Battle of Britain, the new Franz model was superior to the Mk.II Spitfire in many respects. Not only was it able to outperform the Mk. II Spitfire in speed and rate of climb, it also was able to out-turn it above about 18,000ft – something previously unheard of.

At this point the Mk.IV was not going to be ready in time to counter the new Franz. Meanwhile the Griffon was running into very serious production problems and it wasn't clear if it would ever be ready. As an emergency stop-gap measure was needed as soon as possible: this was the Mk.V.

The Mk.V was nothing more than a Mk.II with the newer Merlin 45 series engine. This engine delivered slightly more takeoff power at 1,440hp, but greatly increased the power available at higher altitudes due to a new two-stage supercharger design. While it was no Mk.IV, the Mk.V was able to hold its own with the 109F's it was meeting.

Timing played an important part, as over the winter a serious problem in the tail structure of the Franz turned up, and all production was halted. The problem wasn't solved until the early spring, by which time the Mk.V had already started deliveries.

It would turn out that the problems with the Mk.IV's Griffon engine were as bad as some suspected, and it would be another two years before versions with that engine would enter service. In the meantime the Mk.V proved so useful that it would go on to be the most produced version by far, with 94 Mk.VA's (eight-gun), 3,923 Mk.VB's (cannon) and 2,447 Mk.VC's

The Spitfire's elliptical wings gave it a very distinctive look; their thin cross-section gave it speed; the brilliant design of Mitchell and his successors (he died in 1937) meant the Spitfire was loved by its pilots. It saw service during the whole of World War II, in all theatres of war, and in many different variants. Only late in the war, when the Rolls Royce Griffon began to replace the famous Merlin and speeds went up, was it discovered how advanced these wings were: with a safe Mach number of 0.83 and a maximum Mach number of 0.86, the Spitfire's wing was able to reach higher speeds without Mach-induced flutter than many much newer designs. *need to check these numbers*

More than 8,300 of all variants were built, and Spitfires remained in service well into the 1950s.

The Spitfire is often credited with winning the Battle of Britain. The aircraft, and Mitchell, were lauded in the (somewhat inaccurate) movie "The First Of The Few". It certainly must be considered one of the finest aircraft of the war... and possibly the most beautiful. But how did it compare with the Hawker Hurricane (that the RAF used in greater numbers at that critical stage in 1940), or with its counterpart in the German Luftwaffe, the Messerschmitt 109? The Hurricane's guns were better suited to attacking bombers, but the close pattern of fire and slow speed made the Hurricane a bad choice for attacking the German fighter protection. The Spitfire, on the other hand, was in most respects the close equal of the Me109 but had some attributes that helped "Spits" to win many "dog fights"... most often quoted is manoeuvrability but good cockpit visibility was probably a greater factor. Nonetheless, seven in every ten German planes shot down during the Battle of Britain were victims of Hurricane pilots.

There also was a naval version called the Seafire. It was especially adapted for operation from aircraft carriers: with an arrester hook, folding wings and other specialised equipment. Like the Spitfire, the Seafire had a narrow undercarriage track, which meant that it was not well suited to deck operations, and had a very high accident rate. Many Spitfires and a few Seafires remain airworthy and many aircraft museums treasure static examples of this graceful yet lethal fighter. The RAF maintains some for flying display and ceremonial purposes in the Battle of Britain Memorial Flight at Coningsby in Lincolnshire.