Supermarine Spitfire

One of the most important modifications to the Spitfire was to replace the all machine gun armament with wing mounted [Vous devez être inscrit et connecté pour voir ce lien].

In December 1938, Joseph Smith was instructed to prepare a scheme to equip a Spitfire with a single Hispano mounted under each wing.

Smith objected to the idea and designed an installation in which the cannon were mounted on their sides within the wing, with only small external blisters on the upper and lower wing surfaces.

The first Spitfire equipped with single Hispanos in each wing was L1007 which was posted to [Vous devez être inscrit et connecté pour voir ce lien] in January 1940 for squadron trials.

On 13 January, this aircraft, piloted by [Vous devez être inscrit et connecté pour voir ce lien] Proudman of [Vous devez être inscrit et connecté pour voir ce lien] took part in an engagement when a [Vous devez être inscrit et connecté pour voir ce lien] was shot down.

Soon after this Supermarine was contracted to convert 30 Spitfires to take the cannon armed wing; [Vous devez être inscrit et connecté pour voir ce lien] received the first of these in June 1940 and by 16 August, 24 cannon armed Spitfires had been delivered.

These were known as the Mk IB, the eight machine gun Mk Is were retrospectively called the Mk Ia. With the early cannon installation, jamming was a serious problem. In one engagement, only two of the 12 aircraft had been able to fire off all of their ammunition.

Further cannon-armed Spitfires, with improvements to the cannon mounts, were later issued to 92 Squadron and it was eventually realised the best armament mix was two cannon and four machine guns (most of these were later converted to the first Mk Vb).

From November 1940, a decision was taken that Supermarine would start producing light-alloy covered ailerons which would replace the original fabric covered versions.

However, seven months after the decision was taken to install them on all marks, Spitfires were still being delivered
with the original fabric covered ailerons.

From this time on, metal ailerons were fitted to all Spitfires coming off the production lines.

Retrofitting of older Spitfires with the new ailerons proceeded slowly due to the limited capacity of Supermarine, at the rate of 10 sets a week.

Foreign orders: Mk Is


The type numbers 332, 335, 336 and 341 were given to versions of the Mk I which were to be modified to meet the requirements of [Vous devez être inscrit et connecté pour voir ce lien],[Vous devez être inscrit et connecté pour voir ce lien],[Vous devez être inscrit et connecté pour voir ce lien], and [Vous devez être inscrit et connecté pour voir ce lien] respectively.

Estonia's order was cancelled when the Soviet Union annexed the country.

The Greek and Portuguese orders were refused by the Foreign Office.

The 59 aircraft for Turkey were approved, but after delivering two aircraft, the Foreign Office put a halt to that too in
May 1940.

The 208th production Spitfire I was sold to France and in June 1939 was delivered for evaluation.

In 1941, the British government agreed to supply Portugal with 18 Spitfire Mk 1as.

These were refurbished aircraft, drawn from RAF stocks, retrofitted with TR 9 HF radios and no IFF.

These arrived from late 1942 and were given the serial numbers 370 to 387, forming the XZ Esquadrilha at [Vous devez être inscrit et connecté pour voir ce lien].

These were all scrapped by the end of 1947.

Speed Spitfire (Type 323)


In 1937 ideas about modifying a Spitfire to make an attempt on the world landplane speed record were mooted.

At the time the record of 352 mph (566 km/h) was held by [Vous devez être inscrit et connecté pour voir ce lien] flying a [Vous devez être inscrit et connecté pour voir ce lien] racing aircraft.

Although an early Spitfire I was capable of 362 mph (583 km/h), this was at a full-throttle height of 16,800 ft
(5,100 m); the regulations for the world speed record demanded that the aircraft fly a 1.86-mile (2.99 km) course at an altitude no greater than 245 ft (75 m).

The prototype Spitfire, which was the only one flying, was capable of 290 mph (470 km/h) at very low level.

On 11 November 1937 the modified Messerschmitt Bf 109 V-13 (D-IPKY), flown by Herman Wurster, raised the world speed record to 379 mph (610 km/h).

It was still felt that a modified Spitfire could do better than this and, on the strength of this, the Air Ministry issued a contract to fund this work.

Accordingly a standard Mk I K9834 (the 48th production Spitfire) was taken off the production line and modified for the attempt on the World Speed Record.

All military equipment was removed and the hinged gun panels, radio door and flare chute opening were replaced with removable panels.

A special "sprint" version of the Merlin II, running on a special "racing fuel" of [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien] and[Vous devez être inscrit et connecté pour voir ce lien], with a small amount of [Vous devez être inscrit et connecté pour voir ce lien] was able to generate 2,100 hp (1,565 kW) for short periods.

This drove a Watts coarse pitch, four bladed wood propeller of 10 ft (3.0 m) in diameter.

Cooling the more powerful engine was achieved using a pressurised water system.

This required a deeper radiator inside a lengthened duct which extended to the trailing edge of the starboard wing.

A larger diameter oil cooler was fitted under the port wing.

The wingspan was reduced to 33 ft 8 in (10.29 m) and the wingtips were rounded.

All panel lines were filled and smoothed over, all round headed rivets on the wing surfaces were replaced by flush rivets and an elongated "racing" windscreen was fitted.

A tailskid replaced the tailwheel. Finally the "Speed Spitfire" was painted in a highly polished gloss Royal Blue and Silver finish.

As it turned out the finished aircraft weighed some 298 lb (135 kg) more than a standard 1938 vintage Spitfire.

However, in June 1938 the [Vous devez être inscrit et connecté pour voir ce lien] V2 set a new record of 394.6 mph (635.0 km/h), which was very close to the maximum speed the as yet unflown Speed Spitfire was likely to achieve.

The first flight of the modified Spitfire took place on 11 November 1938; from late February 1939 the maximum speed reached was 408 mph (657 km/h) at 3,000 ft (910 m).

It was obvious that further modifications would be needed; the decision was made to delete the radiator and change the cooling to a "total loss" system.

The upper fuel tank was removed and replaced with a combined [Vous devez être inscrit et connecté pour voir ce lien] and water tank.

The water was fed through the engine and back to the tank, where as much as possible would be condensed and the rest was ejected from the base of the engine as a jet of steam.

It was calculated that the Speed Spitfire would be able to make the speed runs and land safely before the water
and much reduced fuel would run out at about the same time.

However once the World Speed records were twice broken in quick succession by the Heinkel He 100 V8 (463.9 mph (746.6 km/h) on 30 March 1939) and [Vous devez être inscrit et connecté pour voir ce lien] (469.22 mph (755.14 km/h) on 26 April), it was decided the Speed Spitfire needed a great deal more modification to even come close to the new speed records and the project lapsed.

On the outbreak of War, the Speed Spitfire was modified to a hybrid PR Mk II with the special Merlin II being replaced by a Merlin XII driving a variable pitch de Havilland propeller, and the racing windscreen replaced by a PR wrap-around type.

Nothing could be done about the reduced fuel capacity and it could never be used as an operational aircraft.

Flown as a liaison aircraft between airfields in Britain during the war, K9834 was scrapped in June 1946.

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PR Mk I Types - Early Reconnaissance Versions


Before the Second World War, the conventional wisdom was to use converted [Vous devez être inscrit et connecté pour voir ce lien] types for airborne photo [Vous devez être inscrit et connecté pour voir ce lien].

These bombers retained their defensive armament, which was vital since they were unable to avoid interception.

It was soon found that modified [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien] were easy targets for German fighters and heavy losses were being incurred whenever these aircraft ventured over German territory.

In August 1939, Flying Officer Maurice Longbottom, inspired by [Vous devez être inscrit et connecté pour voir ce lien], filed a memorandum Photographic Reconnaissance of Enemy Territory in War with RAF Headquarters.

In the memorandum Longbottom advocated that airborne reconnaissance would be a task better suited to fast, small aircraft which would use their speed and high service ceiling to avoid detection and interception.

He proposed the use of Spitfires with the armament and radios removed and replaced with extra fuel and cameras.

As a result of a meeting with [Vous devez être inscrit et connecté pour voir ce lien], Air Officer Commanding [Vous devez être inscrit et connecté pour voir ce lien], two Spitfires N3069 and N3071 were released by [Vous devez être inscrit et connecté pour voir ce lien] and sent to the "[Vous devez être inscrit et connecté pour voir ce lien] Flight", a highly secret reconnaissance unit under the command of [Vous devez être inscrit et connecté pour voir ce lien] Cotton.

These two Spitfires were "Cottonised" by stripping out the armament and radio-transmitter, then, after filling the empty gun ports and all panel lines, the airframe was rubbed down to remove any imperfections.

Coats of a special very pale blue-green called Camoutint were applied and polished.

Two F.24 cameras with five inch (127 mm) [Vous devez être inscrit et connecté pour voir ce lien] lenses, which could photograph a rectangular area below the
aircraft, were installed in the wing space vacated by the inboard guns and their ammunition containers as a stop-gap measure.

Heating equipment was installed on all PR Spitfires to stop the cameras from freezing and the lenses from frosting over at altitude.

These Spitfires, which later officially became the Spitfire Mk I PR Type A, had a maximum speed of 390 mph.

Several of the sub-types which followed were conversions of existing fighter airframes, carried out by the [Vous devez être inscrit et connecté pour voir ce lien].

The Type D, which was the first specialised ultra long-range version, was the first to require that the work be carried out by Supermarine.

In the Mk I PR Type B (also known as Medium Range (MR)) conversions which followed the camera lenses were upgraded to an eight inch (203 mm) focal length, giving images up to a third larger in scale.

An extra 29 gal (132 l) fuel tank was installed in the rear fuselage.

It had been envisaged that much larger cameras would be installed in the fuselage immediately behind the pilot, but at the time RAF engineers believed this would upset the Spitfire's centre of gravity.

Cotton was able to demonstrate that by removing lead weights, which had been installed in the extreme rear fuselage to balance the weight of the constant speed propeller units, it was possible to install cameras with longer focal-length lens in the fuselage.

The Type B was the first to dispense with the heavy bullet resistant windscreen.

Many of these early PR Spitfires were fitted with the Merlin XII engine and Rotol constant-speed propeller with the early, blunt spinner of the Spitfire Mk II.

The Mk I PR Type C carried a total of 144 gal (655 l) of fuel and was the first photo reconnaissance aircraft to reach as far as [Vous devez être inscrit et connecté pour voir ce lien].

The extra fuel was carried in the tank behind the pilot and in a 30 gal (136 l) blister tank under the port wing, which was counterbalanced by a camera installation in a fairing under the starboard wing.

A larger oil tank was installed, necessitating the reshaping of the nose to the distinctive PR Spitfire "chin".

This version was also known as the Long Range or LR Spitfire.

The Mk I PR Type D (also called the Extra Super Long Range Spitfire) was the first PR variant that was not a conversion of existing fighter airframes.

The Type D carried so much fuel that it was nicknamed "the [Vous devez être inscrit et connecté pour voir ce lien]."

The D shaped wing leading edges, ahead of the main spar, proved to be an ideal location for an integral tank.

Accordingly, in early 1940, work started on converting the leading edges, between rib four through to rib 21, by sealing off the spar, outer ribs and all skin joins allowing 57 gal (259 l) of fuel to be carried in each wing.

Because the work was of low priority, and with the urgent need for fighters the first two, hand-built prototypes
of the PR Type Ds weren't available until October.

In addition to the leading edge tanks these prototypes also had a 29 gal (132 l) tank in the rear fuselage.

An additional 14 gal (63 l) oil tank was fitted in the port wing.

The cameras, two vertically mounted F.24s with 8 inch (20.3 cm) or 20 inch (50.8 cm) lens or two vertically mounted F.8s with 20-inch (510 mm) lens, were located in the rear fuselage.

With the full fuel load the [Vous devez être inscrit et connecté pour voir ce lien] was so far back the aircraft was difficult to fly until the rear fuselage
tank had been emptied.

Despite these difficulties the type quickly proved its worth, photographing such long distance targets as [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien].

Once the first two Type Ds, P9551 and P9552 had proven the concept the production aircraft, which were soon
redesignated PR Mk IV, were modified to increase the leading edge tank capacity to 66.5 gal (302 l) and by omitting the rear fuselage tank.

These aircraft were better balanced and had the more powerful Merlin 45 engine as used by the Mk V, along with heated cabins, which were a great comfort to pilots on such long flights.

A total of 229 Type Ds were built.

A single Mk I PR Type E N3117 was built to address a requirement for oblique close-ups as opposed to high altitude vertical pictures.

This conversion carried an F.24 camera in a fairing under each wing.

These faced forward, were splayed outwards slightly and aimed downwards at about 15 degrees below the horizontal.

A 29 gal (132 l) fuel tank was fitted in the rear fuselage. N3117 proved most useful as it was able to photograph targets under weather conditions that would make high altitude photography impossible and experience with this aircraft resulted in the development of the Type G.

Mk I PR Type F was an interim "super-long-range" version which entered service in July 1940, pending the Type D.

The Type F carried a 30 gal fuel tank under each wing, plus a 29 gal tank in the rear fuselage, as well as having an enlarged oil tank under the nose.

It was a useful enough improvement that nearly all existing Type Bs and Type Cs were eventually converted to the Type F standard.

Operating from[Vous devez être inscrit et connecté pour voir ce lien] it was just able to reach, photograph and return from [Vous devez être inscrit et connecté pour voir ce lien].

15 of these were based on the Mk V airframe.

The Mk I PR Type G was the first fighter-reconnaissance version and performed a similar low-level tactical role to the Type E.

One oblique F.24 camera, with either an eight inch or 14 inch lens, was fitted facing to port, between fuselage frames 13 and 14.
Two vertical F.24 cameras were also installed in the fuselage.

The forward camera, installed below the oblique, could be fitted with a five inch or an eight inch lens while the rear camera could be fitted with an eight inch or a 14 inch lens.

A 29 gal (132 l) fuel tank was fitted just behind the pilot.

The first PR Gs were converted from Mk I airframes and their Merlin II engines replaced with Merlin 45s.

Late PR Gs were converted from Mk V airframes. The Type G was fully armed with 8 × .303" Brownings and retained the armoured windscreen and gunsight

A feature of most PR Spitfires were the specially modified "Blown" canopies which incorporated large lateral teardrop shaped blisters, allowing the pilots a much clearer view to the rear and below, vital forsighting the cameras.

The lateral cameras were aimed by lining up a tiny +, marked on the side of the blister, with a fine black line painted on the port outer aileron.

On all unarmed PR conversions the gunsight was replaced by a small camera control box from which the pilot
could turn the cameras on, control the time intervals between photos and set the number of exposures.

In 1941, a new system of mark numbers was introduced, independent of those used for the fighter versions.

It should also be noted that several PR conversions were re-converted to later PR types.

• The Type C became the PR Mk III.
  
• The Type D became the PR Mk IV.
  
• The Type E became the PR Mk V.
  
• The Type F became the PR Mk VI.
  
• The Type G became the PR Mk VII.
  

In all, 1,567 Mk Is were built (1,517 by Supermarine between May 1938 and March 1941, 50 by Westland, July to September 1941).

Mk II (Type 329)


In the summer of 1939 an early Mk I K9788 was fitted with a new version of the Merlin, the XII.

With the success of the trial it was decided to use this version of the Merlin in the Mk II which, it was decided, would be the first version to be produced exclusively by the huge new Nuffield "shadow" factory at [Vous devez être inscrit et connecté pour voir ce lien].

Chief among the changes was the upgraded 1,175 hp (876 kW) Merlin XII engine.

This engine included a [Vous devez être inscrit et connecté pour voir ce lien], instead of the electric system of earlier and some later versions of the Merlin, and it required a small "teardrop" blister on the forward starboard cowling.

The Merlin XII was cooled by a 70% to 30% water [Vous devez être inscrit et connecté pour voir ce lien] mix, rather than pure glycol used for earlier Merlin versions.

In early 1940 Spitfire Is of [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien] were fitted with Rotol manufactured wide-bladed propellers of 10 ft 9 in (3.27 m) diameter, which were recognisable by a bigger, more rounded spinner: the decision was made that the new propeller would also be used exclusively by the Mk II.

This engine/propeller combination increased top speed over the late Mk I by about 6-7 mph below 17,000 feet
(5,200 m), and improved climb rate.

Due to all of the weight increases maximum speed performance was still lower than that of early Mk Is, but combat capability was far better.

The Rotol propeller units were later supplemented by de Havilland constant-speed units similar to those fitted to Mk Is.