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Supermarine Spitfire - the gun wings

Supermarine Spitfire - the gun wings

Supermarine Spitfire - the gun wings

The Supermarine Spitfire was fitted with a series of different wings during its service career. The type of wing generally indicated the armament of the fighter, or the range of guns that a particular aircraft could carry, and was combined with the Mk number to produce a full designation – Mk IIb or Mk Vc.

In each case the number of guns indicates the total for the fighter, not the total per wing.

“a” wing

The Spitfire I was originally armed with eight .303in Browning machine guns, each with 300 rounds. This type of wing was officially designated as the “a” wing on 15 March 1940, to distinguish between machine gun armed Spitfires and cannon armed aircraft. The vast majority of Spitfires in use during the battle of Britain were armed with machine guns.

“b” wing

The eight .303in machine guns of the Mk I Spitfire had given it a great deal of punch when it was designed, but when the Germans began to add armour to their bombers the machine guns were found somewhat lacking. Accordingly experiments were made with the use of 20mm Hispano cannon.

This gave it a great deal of punch when it was developed, but when the Germans began to add armour to their bombers, the rifle calibre machine guns lost some of their effectiveness.

The response was to fit the Spitfire with the 20mm Hispano cannon. This poses a variety of problems, not least of which was the size of the cannon. The only way to fit it in the Spitfire wing was to mount it on its side. A second problem was that the early cannons were prone to jam under the pressure of combat. If one cannon jammed, the recoil from the other one was enough to push the Spitfire off course.

The “b” wing entered service during 1940. No.19 Squadron used it during the battle of Britain, but the cannons were still causing problems. Finally in November 1940 No.92 Squadron was given Spitfires equipped with two 20mm cannon and four 0.303in machine guns. This proved to be a much more effective combination of weapons, and became the standard for the “b” wing.

“c” wing

The “c” wing appeared in October 1941. It was a “universal” wing that could take eight .303in machine guns, four 20mm cannon or two 20mm cannon and four machine guns. Each cannon now had 120 rounds, compared to the 60 of the “b” wing. This wing was used on the majority of Mk V Spitfires, normally with the combined cannon and machine guns configuration. The “c” wing also had the capability to carry two 250lb bombs under the wings, or one 500lb bomb under the fuselage. If machine guns were used, they were used in the outboard position. The “a” and “b” wings were not used after the Spitfire V.

“d” wing

This was a wing used on some photo reconnaissance Spitfires. Instead of guns this wing carried extra fuel, giving the reconnaissance aircraft a range of up to 2000 miles.

“e” wing

The “e” wing was a further development of the Universal. It could carry either four 20mm cannon or two 20mm cannon and two 0.5in Browning machine guns. This time the cannon took the outer position and the machine guns the inner. This was partly because it gave more room for machine gun ammunition and partly because the bombs were carried below the inner gun positions, and there had been some problems reported when both cannon and bombs were on the same part of the wing. The “e” wing appeared in the second half of 1944.

Mk 21/24 wing

The wing used in the Mk 21 Spitfire was significantly redesigned. The leading edge lost its curve, running straight out to the guns. Armament was standardised at four 20mm Hispano Mk II cannon, with 175 rounds for the inboard gun and 150 for the outboard gun. In official documents this was referred to as the “new shape wing”.

Prototypes - Mk I - Mk II - Mk III - Mk V - Mk VI - Mk VII - Mk VIII - Mk IX - Mk XII - Mk XIV - Mk XVI - Mk XVIII - Mk 21 to 24 - Photo Reconnaissance Spitfires - Spitfire Wings - Timeline

The Hispano Cannon

The Hispano-Suiza HS.404 20 mm-calibre automatic cannon was one of the most widespread aircraft weapons of the 20th century, used by British, American, French, and many other military services. Firing a 20 mm diameter projectile, it delivered a useful load of explosive from a relatively light weapon. This made it an ideal cannon for use onboard fighters, replacing the multiple 7.62 mm (.30 caliber) machine guns commonly used in military aircraft in the 1930s.

Overall arrangement of the armament bay of the Spitfire LF Mk. IXe, with Hispano Mk. II cannon to the left and the American M2 Browning machine gun to the right.
[Martin Waligorski]


Like the name implies, the Hispano cannon was developed by the French company Hispano-Suiza. It was based on the earlier Swiss Oerlikon FF S weapons, which the company manufactured under license in France as HS.7 and HS.9.

In the late 1930s, engineer Marc Birkigt designed a new and much improved version with a revised action, much faster rate of fire, and somewhat higher muzzle velocity. The result was the Type 404, or HS.404, which was widely considered the best aircraft cannon of its kind. The 404 was widely used on pre-war French designs, notably in installations firing through the drive shaft of the Hispano-Suiza 12Y engine, a system known as a moteur-canon employed in Morane-Saulnier M.S.406 and Dewoitine D.520.

The HS.404 was fed by drum magazines that could accommodate at most 60 rounds. Since in most installations the magazine could not be switched during flight, the small ammunition capacity was problematic. In 1940, Hispano-Suiza was developing a belt-feeding system, as well as derivatives of the HS.404 in heavier calibres such as 23 mm, but all these projects were halted with the German occupation of France.

British License

In the meantime, Great Britain had acquired a license to build the HS.404, which was first used in a British fighter as the Hispano Mk.I with the Westland Whirlwind of 1940. British engineers developed a belt-feeding mechanism. The new design was adopted by the RAF and FAA in 1941 in a slightly modified form as the Hispano Mk.II.

Four cannon replaced the eight Browning .303 machine guns in the Hawker Hurricane Mk. IIc and in Supermarine Spitfire Mk. Vc, and became standard armament in late-war British fighters such as the Hawker Typhoon/Tempest family or late marks of the Spitifre. Although earlier Spitfires equipped with Type C wing could accomodate four cannon, most of them carried only two because of technical difficulties such as inadequate gun-heating capacity for the outboard cannon leading to the gun freezing at high altitiudes.

Installation of Mk. II Hispano cannon in the wing of Spitfire Mk. Vc.
[Crown Copyright]

American License

The gun was also licensed for use in the United States as the M1, with both the United States Army Air Corps (USAAC) and U.S. Navy planning to switch to the 20 mm as soon as sufficient production was ready. A massive building program was set up, along with production of ammunition, in 1941. When delivered the guns proved to be extremely unreliable and suffered a considerable number of misfires due to the round being “lightly struck” by the firing pin. The British were interested in using this weapon to ease production in England, but after receiving the M1 they were disappointed. In April 1942 a copy of the British Mk.II was sent to the U.S. for comparison, with the differences being primarily that the British version used a slightly shorter chamber that they believed was the cause of the U.S.’s problems.

The U.S. declined to modify the chamber of their version, but nevertheless made other different modifications to create the no-more-reliable M2. By late 1942 the USAAC had 40 million rounds of ammunition stored, but the guns remained unsuitable. The U.S. Navy had been trying to go all-cannon throughout the war, but the conversion never occurred. As late as December 1945 the Army’s Chief of Ordnance was still attempting to complete additional changes to the design to allow it to enter service.

Hispano Mk. V

Meanwhile, the British had given up on the U.S. versions and production levels had been ramped up to the point where this was no longer an issue anyway. They upgraded to the Hispano Mk. V, which had a shorter barrel, was lighter and had a higher rate of fire, although at the expense of some muzzle velocity. One of the main British fighters to use the Mk. V was the Hawker Tempest Mk. V Series II, which mounted a total of four.

The U.S. followed suit with the M3, but reliability problems continued. After World War II the United States Air Force (USAF) adopted a version of the M3 cannon as the M24, similar in most respects except for the use of electrically primed ammunition.

In the post-war era the HS.404 disappeared fairly quickly due to the introduction of revolver cannon based on the German Mauser MG 213. The British introduced the powerful 30 mm ADEN cannon in most post-war designs, and the French used the very similar DEFA cannon, both firing the same ammunition. The USAF introduced the 20 mm M39 revolver cannon to replace the M24, while the Navy instead combined the original Hispano design with a lighter round for better muzzle velocity in the Colt Mk 12 cannon.

A pair of Mk. V Hispanos installed in the wing of the Spitfire Mk. 21. Shorter barrels and smaller feed motors resulted in a more compact arrangement.
[Crown Copyright]


The Mk. II Hispano fired a 130 gram (4.58 oz) 20 mm x 110 mm projectile with a muzzle velocity between 840 and 880 m/s (2,750 and 2,900 ft/s), depending on barrel length. Rate of fire was between 600 and 850 rounds per minute. It was 2.36 m (7 ft 9 in) long, weighing between 42 and 50 kg (93 and 110 lb). The British Mk V and American M3/M24 weapons were lighter with higher rates of fire than the early HS.404 guns.

  • Type: single-barrel automatic cannon
  • Calibre: 20 mm ?110 (0.79 in)
  • Operation: gas operated
  • Length: 2.36 m (7 ft 9 in)
  • Weight (complete): 42?50 kg (93?110 lb)
  • Rate of fire: 600?850 rpm
  • Muzzle velocity: 840 to 880 m/s (2,750 to 2,900 ft/s)
  • Projectile weight: 130 g (4.58 oz)
  • HE round explosive filler:

Installation of the Hispano Mk. II in the armament bay of the Spitfire LF Mk. IXe. The prominent drum on top of the cannon breech is the belt-feeder, a spring-loaded mechanism which was re-tensioned every time the gun recoiled.The smaller breech to the right of the cannon belongs to the .5″ M2 Browning machine gun.
[Martin Waligorski]

Details of the belt-fed Hispano Mk.II installation in the armament bay of the Spitfire LF Mk. IX, looking aft. The belt was pulled from the ammunition box, integrated with the wing’s structure, through a roller visible at the right edge of the photo.
[Martin Waligorski]

The text in this article uses content from a Wikipedia article and is therefore licensed under the GNU Free Documentation License (GFDL). The Images are property of their respective copyright owners as specified and are not sin the GFDL unless specifically stated.

The Silver Spitfire is a Mk.IX Spitfire finished in polished aluminium with the guns removed. By ‘de-militarising’ the aircraft in this manner we aim to highlight the timeless beauty of its design. With a plane that is less provocative than one adorned with camouflage paint, we hope to broaden the appeal and reach of the project, and gain easier access to nations en route.

By presenting the aircraft in this beautiful ‘bare metal’ state we aim to highlight the beauty of the Spitfire’s timeless design, drawing attention to the unique and famous shape of the airframe.

“The Silver Spitfire is one of the most original airworthy spitfires in the world”

P-51 Mustang vs Spitfire: Specs

Throughout and after the war, several variants of both the P-51 Mustang and the Spitfire were developed. As such, we will compare the specifications of the two most common variants of the Mustang and Spitfire.

The most common variant of the P-51 Mustang is the P-51D, previously in service with the RAAF, SAAF and USAF. The most common variant of the Spitfire is the Spitfire Mk VB, previously in service with the RAAF, SAAF and RAF.

P-51s were not only used in WWII, however, it is the conflict that made them famous. The Mustang served long after WWII, as the primary fighter in several air forces’ fleet.

By January 1957, the US military had completely retired their fleet of P-51s. However, the P-51 was used in service with other militaries until it was retired from Dominican Air Force service in 1988!

Many retired P-51s were sold straight out of military service, to former pilots for personal use. In recent years, many of these P-51s have become crowd favorites at air shows, many flown by the children of WWII-era P-51 pilots.

Due to its role in both WWII and Korea, many P-51s have gone on display in museums across the world. Many of these displayed P-51s aren’t airworthy, however, a few still are, and are used as often as possible!

Weirdly, both the Cessna Citation Mustang and the Ford Mustang are two of the things who are named in honor of the WWII fighter. Cessna had many workers who had worked on the P-51, where Ford named it in order to sell to former Mustang pilots.

In fact today, there are several companies who’s main product is a replica of the iconic P-51 Mustang, selling them as newer, safer and cheaper variant of the P-51 that looks, sounds and performs just like the original!


Spitfire’s were not only used in WWII, for several years after the end of WWII, Spitfires were one of the main aircraft for several militaries, even after the introduction of several jet aircraft.

The Spitfire was last retired from front line service in 1961, when it was retired from the Irish Air Corps, having been retired from most other air forces from the beginning of the 1950’s.

However, this was not the end of the Spitfire’s flying days. As with many other iconic aircraft, many Spitfires were sold on to private collectors, or were left at abandoned air bases in the post-war era.

Many of these Spitfires were flown by retired Spitfire pilots at airshows all around the world. Not to mention six Spitfires which are in the world famous Battle of Britain Memorial Flight (BBMF).

Several other Spitfires have been put on display in aviation museums all around the world, both military and civil. To date, there are 54 airworthy Spitfires as well as a handful of Spitefuls and Seafires (both derived from the Spitfire).

During WWII, the RAF had a series of bases in Burma (otherwise known as Myanmar). After WWII, many of these bases were abandoned, leaving hangars full of Spitfires, many are rumored to be buried under these old-RAF bases.

Supermarine Spitfire Mk XIV

Read on to find out more about the history of our Spitfire, but make sure and also check out the Spitfire Restoration Webpage.

Only 957 production Mk XIVs were built. It was the first Spitfire in large-scale production with the V-12 Rolls Royce Griffon 65 engine, and entered service in 1944. The Mk XIV was the most successful of all the variants at destroying V-1 flying bombs, accounting for 300 kills. In October 1944 a Mk XIV had the distinction of being the first to destroy a jet-powered Messerschmitt Me 262.

Our Spitfire was built at the Aldermaston factory in Berkshire, England and then delivered to the Royal Air Force. The aircraft was shipped to Karachi, India in July, 1945 for anticipated operations in Southeast Asia. In 1947 it was transferred to the Indian Air Force.

In 1983 the aircraft was found badly damaged in Patna and was returned to England. It was restored and flew again at Cranfield in 1983. The aircraft was painted in the colors of the South East Asia Command.

In 1985 the aircraft was purchased by David Price and shipped to Los Angeles. That year the aircraft won an award at the Oshkosh Air Show. Now owned by the CAF, this Spitfire Mk XIV is at the CAF, Southern California Wing’s Hangar at Camarillo Airport. It is currently in flying status and is available for airshow bookings year-round.

Spitfire Crew: Colin Bedding, Dick Roberts, Steve Nagle, Robert Seeger, Barry Roberts.

Photo by Phil Makanna www.ghosts.com

Spitfire NH749 Background
This essay is being written on the 14th of July 14, 2008 to provide a more detailed look into the whereabouts of this amazing aircraft. On this day, sixty two years ago, a Supermarine Spitfire FR Mk.XIV was on its way to the sub-continent of India. Today that same aircraft, serial number NH749, is sitting in our hangar here in Camarillo. How it got here and what has happened to it since then is an interesting story.

Built at the Supermarine factory at and assembled at the satellite plant at Aldermaston where it was test flown in late 1944. It was delivered to number 33 Maintenance Unit (MU) on 23rd Feb. 1945. From there it went to 215 MU on 20th May 1945. Having missed the war in Europe, she was sent on 2nd July 1945 to India on the S.S. Samaturdy arriving on the 28th. On the 9th of August she was assigned to the RAF’s South East Asia Command. Since this was the day that the second atom bomb was dropped and Japan surrendered five days later. It seems that the RAF never found it necessary to operate NH749. Instead she went into storage until being sold to the Indian Air Force on 29th Dec 1947. Her service in India remains largely a mystery although a tantalizing reference appears here http://www.bharat-rakshak.com/IAF/History/1950s/Wilson01.html
She was found by the Hayden-Bailey brothers languishing in there in 1978 and was brought back to England. http://www.bharat-rakshak.com/IAF/History/Aircraft/Spitfire/SpitNH749o.jpg

The fighter was restored to flying condition by Craig Charleston, sold to Keith Wickenden and appropriately registered G-MXIV. The next owner was David Price’s Museum of Flying in Santa Monica from 1985 until 2005 when he sold it to us.
Shortly after arriving at our facility, the aircraft was being flown by Steve Barber when it suffered a loss of coolant. Steve is a very experienced and skilled pilot and he was able to nurse the aircraft back to Camarillo for an uneventful landing. It was determined that the engine needed to be removed and sent out for overhaul. Mike Nixon’s excellent Vintage V-12’s facility in Tehachapi, California was selected for this work. Removing the engine was quite a task and this was overseen by Leslie Bedding who was a mechanic in the RAF during WW2 and had, coincidentally, served in India. Les is a very gifted craftsman and a stickler for detail and high standards. He determined that our Spit needed quite a bit of work. To achieve all this, he assembled a team of volunteers consisting of his son Colin, Dick Roberts, Robert

The entire coolant system has been refurbished, the engine mounts have been sent out for X-Ray testing as have the undercarriage components. All of the wing attach bolts as well as the undercarriage attach bolts have been replaced with newly manufactured ones. The canopy was found not to operate correctly so that’s being redone. The hydraulic, pneumatic and electrical systems have all been thoroughly tested by Les and components repaired or replaced as necessary. The colors used in the original restoration were not stock and so it was decided to restore the cockpit, engine compartment and as many other components as possible to their proper colors. Colin Bedding is leading this effort and it is far from easy! The aircraft is now being reassembled in preparation for the return from Vintage V-12’s of our engine. The installation of the engine represents an enormous undertaking. The cooling system and its associated plumbing is complex and the airframe in which they fit is very tight. There are many busted knuckles and frayed tempers on the horizon.
At the moment, the aircraft is finished in South East Asia markings. This is about to change as we are considering a European color scheme and the markings of 41 Squadron which flew low backed F Mk.XIV with the 2nd Tactical Air Force from former Luftwaffe bases in liberated Europe in 1945, scoring many victories over a wide range of German Air Force types including a number of jets. 41 Sqn. is one of the oldest still serving with the RAF today after 92 years of continuous service.

Each of the combatant nations involved in the Second World War seems to have produced an aircraft that has become an icon. For the U.S., it is the P-51. For the Germans, the Bf 109 and the Japanese have the Zero. For the British, that aircraft is the Spitfire. Even people with absolutely no interest in aviation can usually recognize the graceful form of the Supermarine Spitfire. The Southern California Wing is fortunate enough to count one of these fighters in our collection.

As most of you know, the Spitfire was designed in the mid thirties by R.J. Mitchell and the prototype, serial number K5054 was first flown by Supermarine chief test pilot Mutt Summers at 4:35p.m. on March 5th, 1936. The flight lasted 8 minutes with no problems and as he stepped down from the aircraft afterward, Mr. Summers’ terse instructions were “I don’t want anything touched!!” It was an auspicious beginning.

The Spitfire was accepted by the Air Ministry and although it’s designer died shortly after it’s first flight after a long illness, responsibility for it’s subsequent development was placed in the very capable hands of an unassuming man with an unassuming name Joe Smith. Throughout its entire development period from 1935 to 1948 there were no significant failures of the basic design. Mutt Summers moved on to become the chief test pilot for Vickers and most of the production and developmental test flying was accomplished by Jeffrey Quill and Alex Henshaw, ably assisted by others too numerous to mention here. Smith, Quill and Henshaw oversaw improvements in the capabilities of the Spitfire which can only be described as remarkable.

Spitfire - Design - Elliptical Wing Design

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.

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.

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° at its root to -½° 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 Spitfire had detachable wing tips which were secured by two mounting points at the end of each main wing assembly: when the Spitfire took on a role as a high-altitude fighter (Marks VI and VII and some early Mk VIIIs) the standard wing tips were replaced by extended, "pointed" tips which increased the wingspan from 36 ft 10 in (11.23 m) to 40 ft 2 in (12.3 m). The other wing tip variation, used by several Spitfire variants, was the "clipped" wing the standard wing tips were replaced by wooden fairings which reduced the span to 32 ft 6 in (9.9 m) The wing tips used spruce formers for most of the internal structure with a light alloy skin attached using brass screws.

The airflow through the main radiator was controlled by pneumatic exit flaps. In early marks of Spitfire (Mk I to Mk VI) the single flap was operated manually using a lever to the left of the pilot's seat. When the two-stage Merlin was introduced in the Spitfire Mk IX the radiators were split to make room for an intercooler radiator the radiator under the starboard wing was halved in size and the intercooler radiator housed alongside. Under the port wing a new radiator fairing housed a square oil cooler alongside of the other half-radiator unit. The two radiator flaps were now operated automatically via a thermostat.

The light alloy split flaps at the trailing edge of the wing were also pneumatically operated via a finger lever on the instrument panel. Only two positions were available fully up or fully down (85°). The flaps were normally lowered only during the final approach and for landing, and the pilot was to retract them before taxiing.

The ellipse also served as the design basis for the Spitfire’s fin and tailplane assembly, once again exploiting the shape’s favourable aerodynamic characteristics. Both the elevators and rudder were shaped so that their centre of mass was shifted forward, thus reducing control-surface flutter. The longer noses and greater propeller-wash resulting from larger engines in later models necessitated increasingly larger vertical and, later, horizontal tail surfaces to compensate for the altered aerodynamics, culminating in those of the Mk 22/24 series which were 25% larger in area than those of the Mk I.

Read more about this topic: Spitfire, Design

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The majority of the Spitfires from the Mk VIII on, used three basic wing types C, D and E

C type Edit

Also known as the "universal wing" the new design was standard on the majority of Spitfires built from mid 1942. The design of the wing was altered to reduce labour and manufacturing time and carry various armaments: A type, B type, or four 20 mm Hispano cannon. [4]

The undercarriage mountings were redesigned and the undercarriage doors were bowed in cross-section allowing the legs to sit lower in the wells, eliminating the upper-wing blisters over the wheel wells and landing gear pivot points. Stronger undercarriage legs were raked 2 inches (5.08 cm) forward, making the Spitfire more stable on the ground and reducing the likelihood of the aircraft tipping onto its nose. [4] During production of the Mk VIII and Mk IX a new undercarriage leg was introduced which had external v-shaped "scissor-links" fitted to the front of the leg this also led to small changes in the shape of the undercarriage bay and leg fairings. [5] Because the Spitfire was no longer to be used as a night fighter, the retractable landing lights were no longer fitted. [4]

The Hispano Mk IIs were belt fed from box magazines allowing for 120 rpg (the Chattellerault system). The fairings over the Hispano barrels were shorter and there was usually a short rubber stub covering the outer cannon port. New upper wing gun-bay doors incorporated "teardrop" shaped blisters to clear the cannon feed motors and the lower wings no longer had the gun-bay heating vents outboard of the gun-bays. The first series of Spitfire Mk IXs retained the bay doors first used on Spitfire VCs these incorporated large blisters to clear the feed motors of two Hispano cannons. All later Spitfires had smaller, more streamlined blisters. [4] To provide room for the belt feed system of the cannon, the inner machine gun bays were moved outboard to between ribs 13 and 14. [4]

Several versions of the Spitfire, starting with the HF Mk VIIs had extra 13 gallon integral fuel tanks added to the wing leading edges between the wing-root and the inboard cannon bay. [6] Although many earlier Spitfires had been modified to carry bomb racks for 250 lb (110 kg) bombs the first Spitfires to be built as fighter-bombers (Modification 1209) were those of the Second Tactical Air Force. The first Mk IX Spitfires used as fighter-bombers began in June 1944. [7]

D Type Edit

These were made for photo-reconnaissance Spitfires, including the PR Mk X and XI no armament was fitted and the "D" shaped leading edges of the wings, ahead of the main spar, were converted into integral fuel tanks, each carrying 66 gallons. To avoid the expansion of fuel in hot weather damaging the wing, pressure relief valves, with small external vent pipes, were fitted near the wing tips. [8]

E type Edit

Structurally identical to the C wing. The outer machine gun ports were eliminated although the outer machine-gun bays were retained, their access doors were devoid of empty cartridge case ports and cartridge deflectors. The new wing allowed for a four cannon armament and the inner bays could carry heavy machine guns. There were thus two possible weapon fits: either

  • 2 × .50 calBrowning M2 machine guns with 250 rpg in the inner bays and 2 × 20 mm Hispano Mk II cannon with 120 rpg in the outer bays

The .303 machine guns mounted in the outer wings were no longer fitted, because rifle calibre bullets were ineffective against heavily armoured aircraft. (These outer guns had always been the less effective part of a Spitfire's armament: their distance from the centreline made them hard to harmonise and in turning engagements, wing flexing meant that the rounds were even more widely scattered). The 20 mm Hispano cannon were moved outboard and the .50 calibre Browning M2/AN, with 250 rpg were added to the inner gun-bays. The first trial installation (modification 1029) was made in BS118 in November 1943 by mid-March 1944 the first service Spitfires to be modified were from 485 (NZ), 222 and 349 Squadrons. Spitfires with this armament were at first referred to as Spifire LF.IX .5 and the E suffix was not officially introduced until early 1945. This armament was standard for all Spitfire Mk IXs and XVIs used by the 2nd Tactical Air Force as fighters and fighter-bombers from shortly after D-Day. [7] It proved more effective for both air-to-air engagements and air-to-ground attacks. [9]

Many Spitfires had their elliptically "pointed" wing tips replaced by shorter, squared off fairings, this slightly improved maximum speed at low altitude and enhanced the roll rate. While many "LF" Spitfires (e.g. the LF.IX) had the "clipped" wings, a number did not. The true distinguishing feature of "LF" versions was the fitting of low-altitude versions of the Rolls-Royce Merlin engine.

Mark numbers, type numbers Edit

The Mark numbers did not necessarily indicate a chronological order, the Mk IX was a stopgap brought into production before the Mks VII and VIII. Some Spitfires of one mark or variant may have been modified to another several of the first Mk VBs were converted from Mk IBs the first Mk IXs were Mk VCs converted, in some instances, by Rolls-Royce at their Hucknall facility.

Up until the end of 1942, the RAF names had Roman numerals for mark numbers. In the period 1943–1948 new aircraft entering service were given Arabic numerals for mark numbers but older aircraft retained Roman numerals. From 1948, Arabic numerals were used exclusively. This article adopts the convention of using Roman numerals for the Mks I–XVI and Arabic numerals for the Mks 17–24. Type numbers e.g. (type 361) are the drawing board design numbers allocated by Supermarine. [10] [11]

Features of late Merlin powered Spitfires Edit

With the development of the Merlin 61/63/66 and 70 series engines, with a two-stage, two-speed supercharger requiring an intercooler, several important modifications were made to the basic airframe and applied to all aircraft powered by these engines. The longer Merlin 61 meant the nose forward of the engine/fuel tank bulkhead was 7 inches (17.8 cm) longer. An intercooler was mounted behind the engine, on the supercharger casing. A small rectangular air scoop for a "Heywood" air compressor was fitted on the starboard upper engine cowling.

The carburettor air intake on early to mid-production Spitfire IXs was a different shape from those of single-stage engined aircraft they were shorter and had a wider air inlet. From 1943, an "Aero-Vee" tropical filter in a long, streamlined fairing was introduced for the carburettor air intake. This was fitted as standard to all Mk VIIs, VIIIs, PR Mk Xs and Mk XVIs, on mid to late production Mk IXs, and to most PR Mk XIs.

A new 10 ft 9 in (3.27 m) diameter four-bladed Rotol propeller was fitted, housed in a pointed spinner. The exhaust units were changed to six "fishtail" stacks per side. Under the nose, the three piece cowling was changed to a one piece layout. The oil tank was no longer a part of the cowling structure. Early Mk IXs had a teardrop shaped blister for a Coffman engine starter [nb 1] on the lower starboard side cowling, just behind the propeller. This was replaced by an improved electric starter on most two-stage Merlin powered Spitfires and, from late 1942 the blister was seen on only a few aircraft.

The Type C wing was fitted as standard. Some mid and most late production Spifire Mk IXs and all Mk XVI were fitted with the Type E wing. While Spitfire IXs converted from Mk VCs had the large teardrop fairings on the upper surfaces, on the majority of Mk VIIs, VIIIs, IXs and XVIs the teardrop shaped blisters covering the Hispano feed motors were reduced in size and more streamlined than those on the Mk VC. According to A.P 1565J P & L (Spitfire IX, XI and XVI Pilot's Notes) the red painted undercarriage indicator rods, which projected through the tops of the wings when the undercarriage was down, were used only on early production Mk IXs. When fitted these rods supplemented an "Electric visual indicator" mounted on the instrument panel. [12] The indicator rods seemed to be fitted on all Mk VIIs and VIIs, supplementing the electric visual indicator. A light for the retractable tailwheel was mounted on the instrument panel, just below the main visual indicator. [13] [nb 2]

Because the intercooler required a radiator, the radiator under the starboard wing was halved in size and the intercooler radiator housed alongside. Under the port wing a new radiator fairing housed a square oil cooler alongside the other half-radiator unit. When the engine was running at low speed, one radiator section provided enough coolant a thermostatic switch turned off the starboard radiator section until more power was called for and extra engine cooling was required. [14]

Other structural changes included flush riveting for the fuselage, introduced in mid-1943. A streamlined round rear-view mirror, with a bullet-shaped fairing replaced the rectangular version. On new production Mk IXs the small, teardrop shaped identification light behind the radio mast was removed.

While early Mk IXs converted from Mk VCs had the original (smaller) elevator horn mass-balances, most had the enlarged version with the straightened leading edge. A new rudder of greater area, which could be identified by a "pointed" tip, was fitted to many Mk VIIs, Mk VIIIs, and mid to late production Mk IXs and Mk XVIs.

All Mk VII and Mk VIII Spitfires had the following changes: The internal structure was strengthened and revised. On the wings the ailerons were reduced in span by 8.5 inches (220 mm) outboard of the outer hinges. There had been some instances of earlier models breaking up in the air in steep high speed dives, it was thought, because of aileron flutter. [nb 3]

The main fuselage fuel tanks were increased in capacity 47 gal (213.7 L) for the upper tank and 49 gal (222.7 L) for the lower. In combination with the wing tanks this gave a total internal capacity of 122 gal (554.6 L), a near 50% increase over the 85 gal (386.4 L) carried by earlier Spitfire marks. In addition a 13 gal (64 L) fuel tank was fitted in each wing leading edge between the wingroot and the inner gun-bay. [16]

The main undercarriage legs, for the first time in the Spitfire's life, were fitted with forward-facing torque links. In addition, the leg doors were slightly concave, allowing the undercarriage to sit lower in the wheel wells when retracted: this meant the upper wing skinning was free of the small bulge which had hitherto been necessary to clear the wheels. The wheels themselves were a new strengthened Dunlop AH10019 "four spoke" pattern, replacing the "five spoke" pattern used since the first Mk Is. This revised undercarriage was also fitted on some mid to late Mk IXs and all Mk XVIs. [17] A retractable tailwheel (Dunlop 2184) was fitted, covered by small doors when in flight. This also applied to the PR Mk Xs and most PR Mk XIs.

Mk VII (type 351) Edit

Like the Mk VI, the Mk VII was a high altitude pressurised variant, this time powered by the Merlin 64 (F. Mk. VII) or 71 (H.F. Mk. VII) series engine with two-stage, two-speed superchargers. [18] [nb 4] The cockpit was pressurised in a similar way to that of the Mk VI, although the details were slightly different. Other changes to the airframe are noted above. The Mk VII used a Marshall manufactured compressor for pressurising the cockpit this was mounted on the right of the engine and drew its air through a long intake under the starboard exhaust stubs. An automatic valve allowed a maximum pressure differential of +2 lb./sq.in. This was built up during the climb and was maintained at heights of 28,000 ft and above. [20]

Extended, "pointed" wingtips were fitted to the Type C wings, increasing the wingspan to 40 ft 2 in (12.2 m). Because the threat from high altitude bombers never materialised many Mk VIIs later reverted to the normal, rounded wingtip.

While early Mk VIIs were fitted with a detachable canopy, secured by four pilot-operated catches, later Mk VIIs were fitted with a "Lobelle"-type hood which opened by sliding backwards, as on non-pressurised versions of the Spitfire. This was a big improvement on the clampdown cockpit of the Mk VI. The canopy was double-glazed and used rubber tubing to create a proper pressure seal against the fuselage. The canopy rails were bulkier than the standard Spitfire type. [20] [21]

In total, 140 Mk VIIs were built by Supermarine. [22] Most of them were powered by the Merlin 64 (F. Mk. VII) or Merlin 71 (H.F Mk. VII), the latter fitted with a Bendix-Stromberg "anti-g" carburettor. [23] The HF Mk had superb high-altitude performance, with a service ceiling of 45,100 feet (13,700 m) French ace Pierre Clostermann recalls in his book, The Big Show, the successful interception of a long-range reconnaissance Messerschmitt Bf 109G-6/R3 by a Mk VII 'Strato Spitfire' of 602 Squadron at 40,000 feet (12,000 m) over the British Home Fleet's base at Scapa Flow in early 1944.

Mk VIII (type 360) Edit

The Mk VIII was an adaptation of the Mk VII without the pressurised cabin and was intended to become the main production model of the Spitfire. When the "interim" Mk IX proved itself to be adequate for the RAF it was decided to use the shadow factory at Castle Bromwich to produce that version only the Mk VIII Spitfires were all built by Supermarine. Apart from the lack of pressurisation, the Mk VIII differed little from the Mk VII beyond the reshaped fin and pointed rudder. Some early production models had extended wingtips but the majority were fitted with the standard version according to Supermarine's Chief Test pilot Jeffrey Quill "When I am asked which mark of Spitfire I consider the best from the flying point of view, I usually reply 'The Mark VIII with standard wingtips.' I hated the extended wingtips. They were of no practical value to the Mark VIII and simply reduced the aileron response and the rate of roll." [24] There were three sub-variants for low altitude (LF Mk VIII), medium altitude (F Mk VIII) and high altitude (HF Mk VIII) which were powered respectively by the Merlin 66, Merlin 63 and Merlin 70 engines. [23]

The F Mk VIII's top speed was 408 mph (657 km/h) at 25,000 ft (404 mph for the LF Mk VIII at 21,000 ft (6,400 m) and 416 mph (669 km/h) for the HF Mk VIII at 26,500 ft), with a service ceiling of 43,000 ft (41,500 ft for the LF Mk VIII and 44,000 ft (13,000 m) for the HF Mk VIII). The two main tanks were given an extra 11 gal for a total of 96 gal which, along with the wing tanks, allowed the fighter to fly for a maximum distance of 660 mi (1,060 km) with a full internal fuel load and 1,180 miles (1,900 km) with a full internal load and a 90 gal drop tank. Provision was made to allow the Mk VIII to carry a single "slipper" drop tank of 30, 90 or 170 gal capacity. With a 170 gal tank, the aeroplane could fly over 1,500 mi (2,400 km). When carrying the 90 or 175 gal tank the aircraft was restricted, once airborne and at cruising altitude, to straight and level flight. [6] A maximum external bomb load of 1,000 pounds (1 × 500 lb (230 kg) bomb attached to the centre bomb-rack plus a 250 lb (110 kg) bomb under each wing) could be carried.

A Mk VIII JF299 was used to experiment with the use of a new cut-back rear fuselage and a "tear-drop" canopy. This was intended to aid pilot visibility many Spitfire pilots who were shot down were done so by enemies who approached in the aircraft's blind spot. In trials, the new hood design was found to bring about great improvements to all-round visibility and with several modifications, was standardised on later Spitfires. [25]

This variant served almost exclusively overseas in the Mediterranean, with the Desert Air Force and the USAAF, in the South West Pacific Area, with the Royal Australian Air Force and RAF and in the South-East Asian theatre with the RAF. After the Mk IX and Mk V, the Mk VIII was the third most numerous operational variant with 1,658 examples built. [24]

Mk IX (type 361) Edit

In the early months of 1942, with the clear superiority of the Focke-Wulf Fw 190 over the Spitfire VB, there was much pressure to get Spitfires into production using the new two-stage supercharged Merlin 61 engine. In September 1941 the Spitfire Mk III prototype N3297 had been converted by Rolls-Royce at their Hucknall plant to take a Merlin 60, which had been specifically designed for use in the Wellington Mk VI high altitude bomber.

The performance increase was described by Jeffrey Quill as a "quantum leap" over that of the Mk VB and another Spitfire airframe, R6700 was modified to take the new engine. Although design work on the Mk VII and VIII series was under way, these would take over a year to get into production and a counter to the Fw 190 was urgently needed. The Air Ministry made the decision that Mk VC airframes should be converted to take the more powerful engine and, as a result, many of the early IXs were converted Mk VCs which did not have any of the refinements which later appeared. These could be identified by the Type C wing with the large double blisters over the inner cannon bays and the identification light on the fuselage spine, behind the aerial mast. The elevator horns were also smaller in size than that of most Mk IXs which had larger horn balances. [26] [27] The first IX was a modified VC AB505, which was tested by the Air Fighting Development Unit (AFDU) in April 1942. [nb 5] The report said

The performance of the Spitfire IX is outstandingly better than the Spitfire V especially at heights above 20,000 feet. On the level the Spitfire is considerably faster and climb is exceptionally good. It will climb easily to 38,000 feet and when levelled off there can be made to climb in stages to above 40,000 feet by building up speed on the level and a slight zoom. Its manoeuvrability is as good as a Spitfire V up to 30,000 feet and above is very much better. At 38,000 feet it is capable of a true speed of 368mph and is still able to manoeuvre well for fighting. [29]

Although the Mk IX's airframe did not have the aerodynamic and strength improvements, or the modified control surfaces of the Mk VII and VIII, the Mk IX still proved to be an effective counter to the Focke-Wulf Fw 190. [30]

In September 1942, the "High Altitude Flight" was set up at RAF Northolt to counter the threat of the high altitude Junkers Ju 86 R bombers. Two Spitfire IXs converted from VCs were stripped of armour, the .303 Brownings and other equipment and repainted in a lightweight PRU blue finish. One of them intercepted a Ju 86R at over 40,000 feet (12,000 m).

Production of the Mk IX finished at Supermarine in June 1943, with production continuing exclusively at the Castle Bromwich factory. Several major and large numbers of minor improvements were progressively introduced to Mk IXs, some of which were used on other Spitfire variants.

The Merlin 61 was phased out early in 1943 in favour of the Merlin 63 and 63A. [31] The new engine had increased power resulting from engine improvements and engine limitations of +18 lbf/(sq in) and 3,000 rpm (5 minute combat). During the second half of 1943, production of the Merlin 63 powered F Mk IX was discontinued in favour of the Merlin 66 powered LF Mk IX. [32] Early production Spitfire IXs suffered from vapour locks in the fuel lines resulting from fuel evaporating if the aircraft was parked in direct sunlight. As a result of this the gun-camera was moved from the port wingroot to the starboard wingroot and a fuel cooler, fed by a small round air-intake was fitted in its place. This fuel cooler was also fitted to early PR Mk XIs [33]

Production of the LF Mk IXs, frequently referred to as the Spitfire IXB, initially ran in parallel with the Merlin 63 powered Marks. This version first became operational in March 1943 with the Biggin Hill Wing, comprised at the time of 611 and 341 (Free French) Squadrons. This type was by far the most produced of the Spitfire IX variants, with over 4,000 built. The maximum power of the Merlin 66 was 1,720 hp (1,280 kW) at 5,750 ft (1,283 kW at 1,752 m) and the maximum speed of the Spitfire LF IX was 404 mph (650 km/h) at 21,000 feet (6,400 m). [34] The Merlin 66 introduced a new Bendix-Stromberg injection carburettor, which replaced the earlier S.U float carburettor. [31]

The H.F IX was powered by the specialised high altitude Merlin 70 and entered service in the Spring of 1944. Serial listings show that the HF Mk IX was produced in relatively limited numbers when they were required, with priority being given to versions rated for low and medium altitudes [nb 6] Maximum power of the Merlin 70 was 1,710 hp (1,280 kW) at 11,000 ft (1,275 kW at 3,353 m): maximum speed of the Spitfire HF.IX was 405 mph (652 km/h) at 25,400 feet (7,700 m) at an all-up weight of 7,320 lb (3,320 kg). [36]

Also introduced in early 1944 was a new Mark II Gyro gunsight. This gunsight calculated the correct angle of deflection to use when leading the target. Its introduction doubled the effectiveness of RAF gunnery and was a major factor in Allied air superiority. [37]

The capacity of the main fuel tanks was 48 gal for the upper tank and 37 gal for the lower, for a total internal capacity of 85 gal. Jettisonable "slipper tanks" of 30, 45 or 90 gal could be carried under the centre-section. [38] As an alternative a cylindrical 50 gal drop tank, adapted from those carried by long range Hawker Typhoons, could be carried on the fuselage bomb rack used on most Mk IXs of the Second Tactical Air Force. To further increase the combat radius some late production Mk IXs were fitted with additional internal self-sealing fuel tanks in the rear fuselage: the upper tank carried 41 gal and the lower 34 gal. When both were full this enabled a ferry range of over 1,200 miles (1,900 km), although they made the aircraft unstable in flight and only straight flight and gentle manoeuvres at low altitudes were recommended by the pilot's manual. The pilot was also warned to avoid instrument flying whenever possible. [39] [40]

Late production Mk IXs, in common with Mk XVIs introduced a new upper engine cowling which incorporated a distinct bulged top surface this design was adopted for the Mk XVI to allow for the modified intercooler of the Packard Merlin 266, which had an integral header tank.

The cut-down rear fuselage and bubble canopy, trialled on a Spitfire Mk VIII, was incorporated into very late production Mk IXs. With the cut down fuselage the lower forward fuselage tank capacity was increased to 47 gallons, while the rear fuel tanks were decreased to a capacity of 66 gallons. [38] These were the rarest of the Mk IXs and many of them featured the "clipped" wings. The great majority of these saw postwar service with the SAAF, both in South Africa and in deployment in Korea during the 1950s.

During early 1945, some Spitfire IXEs and XVIEs of 74 Squadron were fitted with a single RP-3 rocket under each wing. This was believed to be the only RAF Spitfire unit to use rockets operationally during the Second World War. [41]

PR Mk IX (type 374) and FR Mk IX Edit

Pending development of a dedicated Merlin 61 powered PR Spitfire (the Mk XI) at least three Mk IXs (BS338, BS339 and BS473) were taken off the production line and modified to carry two vertical cameras in the rear fuselage. The first of these was delivered to 541 Squadron at RAF Benson on 30 November 1942. Subsequently, another 15 Mk IXs were converted to PR Mk IXs (factory designation type 374) at the Vickers-Armstrong Worthy Down facility. As well as incorporating camera equipment, a wrap-around PR type windscreen was fitted and a larger oil tank was installed under the nose. All armament was removed and a PRU Blue finish applied. These aircraft lacked the "wet wing" tanks, meaning that the PR Mk IX relied on drop tanks for extra range. The most famous PR Mk IX missions involved carrying out reconnaissance missions in preparation for Operation Chastise, the 617 "Dambusters" Squadron attacks on the Ruhr dams. A PR Mk IX photographed the dams the day before the operation and photographed the Moehne Dam after the operation. [42]

FR IXs were standard, armed Mk IXs modified with a single, port-facing, oblique camera. These aircraft were used for low altitude "Dicing" missions in tactical support of army operations. 16 Squadron, which was a unit of the 2nd TAF, used several FR Mk IXs (painted a pale, "Camoutint" Pink, which provided excellent camouflage under cloud cover) to photograph the Arnhem area before and during Operation Market Garden. Another unit using FR Mk IXs was 318 (Polish) "City of Gdańsk" Fighter-Reconnaissance Squadron based in the Mediterranean. [43] Some Spitfires in the MJ- and MK- serial ranges, sent for repair to the Forward Repair Unit (FRU), were also converted by the FRU to a different style of FR Mk 9C with streamlined blisters on both sides of the fuselage. These were used exclusively by No. 414 Squadron RCAF to replace its TAC-R Mustangs. The same conversion was used on F Mk XIVE Spitfires to make FR Mk XIVE Spitfires used exclusively by No. 430 Squadron RCAF. [44]

T Mk IX and TR 9 (type 509) Edit

Although there were wartime conversions of the Spitfire into a two-seat trainer including the one-off modification of a Mk VC by RAF no. 261 Squadron and a Mk IX converted for use as a trainer by the Soviets, the two-seat Spitfire trainer was primarily a postwar programme. In 1946, a Mk VIII (MT818) was the first Vickers-built trainer built as a demonstrator, but in 1948, 10 Spitfire T Mk IXs, were exported to India. In 1951, a further six TR 9 trainers were converted from the standard Mk IX to train pilots for the Irish Air Corps (IAC) Seafire fleet. The Spitfires provided transition training that included gunnery practice since the type was equipped with two .303 Browning machine guns, one in each outer wing bay. Most of the TR 9 aircraft passed to the ground technical training school at Baldonnel where they were used as instructional airframes for the training of aircraft engineers for the Air Corps. Four of the IAC aircraft survived and two went on to join the warbird fleet in the 1970s and later.

In total, 5,656 Mk IXs were built, 561 by Supermarine and 5,095 by Castle Bromwich. [22] Production of the Mk IX ended in April 1945 and, in combination with the Mk XVI this "compromise" was produced in larger numbers than any other Spitfire variant.

PR Mk X and PR Mk XI (types 387, 365 and 370) Edit

When development started on new Merlin 60 powered Spitfires, both the Mk VII and VIII were to have photo-reconnaissance (PR) variants. On 21 April 1942, an order was placed for 70 aircraft, provisionally designated PR Mk VIII. Based on the revised MK VIII airframe these aircraft were to be powered by Merlin 61s and were assigned serial numbers LV643–681 and LV726-756. The Spitfires bearing these serials were eventually built as Merlin 66 LF Mk VIIIs. [45]

A policy change resulted in the pressurised PR variant of the Mk VII being renamed PR Mk X (type 387). This version followed the PR Mk XI into production and was based on the Mk VII airframe with PR Mk XI wings and camera installation. It had the pressurised Mk VII cockpit, with the Lobelle sliding canopy, and retained the fighter style windscreen with the bullet-proof glass panel. The long thin air intake to the cockpit pressurisation system was fitted under the exhaust stacks on the starboard cowling. The performance was similar to that of the PR XI although the pressurised cockpit meant that this version could stay at altitudes of over 40,000 ft for longer without the exhausting physiological effects experienced by the pilots of unpressurised cockpits. [46] Sixteen Mk Xs were built during April and May 1944, with the first mission being flown on 11 May. All saw limited service in 541 Squadron and 542 Squadron for high altitude reconnaissance. Experience with this version led to the development and production of the pressurised version of the PR Mk XIX. [47]

The Mk XI (type 365 standard, type 370 tropicalised) was based on a combination of features from the marks VII, VIII and IX. The Mk XI was the first PR variant to have the option of using two vertically mounted F52 cameras with 36-inch-focal-length lens in the fuselage behind the cockpit. [48] Several other configurations could be fitted, depending on the mission the X Type installation, for example had two vertically mounted F24s with 14-inch lens and an oblique F24 with an 8-inch lens mounted above and facing to port. [49] PR Mk XIs used for tactical reconnaissance had an additional, vertically oriented camera in a fairing under each wing. [48]

Physically the Mk XIs had a deeper nose fairing to accommodate a larger 14.5 gal oil tank and used the unarmoured, wrap-around PRU windscreen. Booster pumps for the wing tanks were fitted and covered by teardrop shaped fairings under the wings. Retractable tailwheels were fitted as standard and the majority of the Mk XIs built had the later large-area pointed rudder. 260 Mk XIs were powered by Merlin 61, 63 or 63A engines, while the remaining 211 used the high-altitude Merlin 70. All of the Merlin 70 and 198 of the Merlin 60 series aircraft were fitted with the Vokes Aero-Vee dust filter in the extended, streamlined carburettor air intake under the nose. [48] All Merlin 60 powered aircraft featured the fuel cooler in the port leading edge wing root. The radio installation was either the VHF TR.1133 or TR.1143 fitted with the "Rebecca" beam approach equipment. [48]

Additional slipper drop tanks could be fitted under the centre-section in common with the Mk IX these could be 30, 45 or 90 gal capacity and, for the Mk XI, a tank of 170 gal capacity was also available. [38]

Spitfire PR Mk XIs were capable of a top speed of 417 mph (671 km/h) at 24,000 ft (7,300 m) and could cruise at 395 mph (636 km/h) at 32,000 ft (9,800 m). Normally Spitfire XIs cruised between these altitudes although, in an emergency, the aircraft could climb to 44,000 ft (13,000 m) However, pilots could not withstand such altitudes for long in a non-pressurised cockpit without suffering from serious physiological effects. [46]

At first, production of the PR Mk XI was delayed because development of the Mk VII and VIII series was delayed. As a result, it was decided to base the Merlin 60 powered PR aircraft on the MK IX airframe. [45] Production was further threatened because of a dispute over RAF PR doctrine: in early 1943, because the new PR Spitfire was delayed, the Air Ministry proposed that all PR units be converted to de Havilland Mosquitoes. After further analysis the Air Staff agreed that Mosquitoes could perform 90% of PR missions so the Spitfire production for only 10% of PR units was mooted. Air Vice Marshal John Slessor, head of Coastal Command pointed out that the Spitfire was smaller than the Mosquito, used half the number of Merlin engines and was faster, more manoeuvrable and quieter and, therefore production should be increased, not reduced. As a result, the Air Staff decided that PR Mk XI production should be accelerated at the cost of the fighters. [48]

The first Mk XIs were built in November 1942: from April 1944 production ran concurrently with the PR Mk XIX before ending in December 1944, when they were phased out in favour of the Mk XIX. In total 471 Mk XI were built by Supermarine. [50]


The PR Mk XIII was an improved PR Type G with a single-stage Merlin engine and is described in Supermarine Spitfire (early Merlin powered variants)

Mk XVI (type 361) Edit

The Mk XVI was the same as the Mk IX in nearly all respects except for the engine, a Merlin 266. The Merlin 266 was the Merlin 66 and was built under licence in the USA by the Packard Motor Company. The "2" was added as a prefix in order to avoid confusion with the engines, as they required different tooling. All Mk XVI aircraft produced were of the Low-Altitude Fighter (LF) variety. This was not determined by the length of the wings (clipped wings were fitted to most LF Spitfires), but by the engine, which had been optimised for low-altitude operation. All production Mk XVIs had clipped wings for low altitude work and were fitted with the rear fuselage fuel tanks with a combined capacity of 75 gal. [38] Many XVIs featured cut-down rear fuselages with bubble canopies. On these aircraft the rear fuselage tank capacity was limited to 66 gal. [38]

Because of a slightly taller intercooler and rearranged accessories on the Packard Merlins a new, bulged upper cowling was introduced and also appeared on late production IXs. [51]

Armament for most Mk XVIs consisted of 2 × 20 mm Hispano II cannon – each with 120 rpg – and 2 × .50 calibre Browning machine guns – each with 250 rpg. 1 × 500 lb (227 kg) bomb could be carried underneath the centre rack, and 1 × 250 lb (114 kg) bomb could be slung under each wing. Some production aircraft had rear fuselage fuel tanks in addition to the main tank which allowed it to fly approximately as far as the Spitfire Mk VIII. Problems with the licence-built engines limited introduction to front-line squadrons for several months. A total of 1,054 Mk XVIs were built by Castle Bromwich. [22]

Spitfire Floatplanes (types 355 and 359) Edit

With the German invasion of Norway in April 1940 the RAF took an interest in the concept of using floatplane fighters in areas where airfields were not immediately available. To this end a Spitfire Mk I R6722 was taken in hand at the Woolston factory to be modified and mounted on Blackburn Roc floats. Tank tests were carried out at Farnborough, using a 1/7 scale model, it was found that the concept was basically sound, although the vertical tail surfaces would need to be enlarged to counterbalance the side area of the floats. The end of the Battle of Norway and the need for as many Spitfires as possible meant that R6772 was converted back to an ordinary fighter without being flown. [52] [53] With the entry of Japan into the war the concept was revived in early 1942. A Spitfire V W3760 was fitted with a pair of floats 25 ft 7 in (7.8 m) long, mounted on cantilever legs. This aircraft was powered by a Merlin 45 driving a four-bladed propeller of 11 ft 3 in (3.43 m) diameter (3.4 m). A Vokes filter was fitted to the carburettor air intake and under the tail an extra fin extension was added. [54]

Other changes included external lifting points forward of and behind the cockpit and a spin-recovery parachute with a rudder balance-horn guard. The Spitfire floatplane was first flown on 12 October 1942 by Jeffrey Quill. Soon afterwards the Vokes filter was replaced by an Aero-Vee filter, similar to that on later Merlin 61 series aircraft, which was extended to prevent water entry, and full Mk VB armament was installed. Two more VBs EP751 and EP754 were converted by Folland and all three floatplanes were transported to Egypt, arriving in October 1943. At the time it was thought that the floatplanes could operate from concealed bases in the Dodecanese Islands, disrupting supply lines to German outposts in the area which relied on resupply by transport aircraft. This scheme came to naught when a large number of German troops, backed by the Luftwaffe, took over the British held islands of Kos and Leros. No other role could be found for the floatplane Spitfires, which languished in Egypt, operating from the Great Bitter Lake. Specifications for the VB based floatplane included a maximum speed of 324 mph (521 km/h) at 19,500 ft (521 km/h at 5,943 m), a maximum rate of climb of 2,450 ft/min at 15,500 ft (12.45 m/s at 4,724 m) and an estimated service ceiling of 33,400 ft (10,180 m). [55] [nb 7]

In the spring of 1944, with the prospect of use in the Pacific Theatre, a Spitfire IX MJ892 was converted to a floatplane. This used the same components as the earlier Mk VB conversions. Jeffrey Quill wrote:

The Spitfire IX on floats was faster than the standard Hurricane. Its handling on the water was extremely good and its only unusual feature was a tendency to "tramp" from side to side on the floats, or to "waddle" a bit when at high speed in the plane.

Soon after testing started the idea of using floatplane fighters was dropped and MJ982 was converted back to a landplane. [56]

Five aircraft were converted:

  • Mk I – R6722
  • F Mk Vb – W3760
  • Mk V – EP751 and EP754
  • Mk IXb – MJ892[57][58]

Drawing board projects Edit

  • Supermarine 305: Designed to the same specification as the Boulton Paul Defiant and Hawker Hotspur. The basic Spitfire wing and undercarriage were mated to a new fuselage which provided room for a gunner and a remote control four-gun turret (originally armed with .303 Brownings, later with Lewis machine guns.) Other modifications included a cooling system mounted in a chin radiator housing. There was no forward firing armament and dive brakes were added to the wings. Projected speed 315 mph (507 km/h) at 15,000 ft (4,572 m). [59]
  • Supermarine 312: This was the basic Spitfire Mk I adapted to take four 20 mm Oerlikon cannon mounted in modified wings. The radiator and oil cooler were moved from under the wing to a duct under the fuselage. This was R J Mitchell's last design before his death in 1937. [60]
  • Supermarine 324, 325 and 327: These designs were for twin-engined fighters which used the same construction techniques and elliptical wing as the Spitfire. All three used tricycle undercarriage with the primary engine being a Merlin with an alternative being the Bristol Taurus. The 324 and 325 were intended to carry an armament of 12 .303 calibre Brownings in groups of six in each outer wing, while the 327 had the armament changed to six 20 mm Hispanos mounted in the wing roots. The 324 and 327 had conventional tractor engines, while the 325 had a pusher engine. [61]

The early Spitfire variants powered by the Rolls-Royce Griffon were adaptations of Mk VC (early Mk XII) or Mark VIII (late Mk XII and Mk XIV) airframes. The later Griffon-engined Spitfire variants embodied new wings, tail units and undercarriages and were very different from any of the earlier Spitfire marks. Griffon-engined variants are described in a separate article.

After the destruction of the main Itchen and Woolston works by the Luftwaffe in September 1940, all Supermarine manufactured Spitfires were built in a number of "Shadow Factories" by the end of the war there were ten main factories and several smaller workshops which built many of the components. A fuller explanation can be found in Supermarine Spitfire. The main Castle Bromwich factory was also aided by a smaller number of the shadow factories. [62] The breakdown of production figures is taken from Air International 1985, p. 187. Information as to when the first production aircraft emerged is from the serial number lists provided in Morgan and Shacklady 2000. Because the first of the Mk IXs were converted from Mk VCs the first true production Mk IX is listed by serial Number.

The propeller ripped off and the diving aircraft reached more than 620mph (1,000km/h)

According to famed test pilot Eric ‘Winkle’ Brown's book Wings on My Sleeve, the high-speed trials began in late 1943. During the programme, Squadron Leader J R Tobin took a Mark XI Spitfire into a 45-degree dive the plane reached a top speed of 606mph (975km/h), or Mach 0.89 (Mach 1 being the technical term for the speed of sound). It was the fastest speed a Spitfire had ever flown – or at least the fastest that a pilot had lived to tell the tale. But a far more dramatic flight was soon to take place.

In April 1944, Squadron Leader Anthony F Martindale, put the exact same Mark XI Spitfire into a dive. This time, the reduction gear designed to limit its speed failed. The propeller ripped off and the diving aircraft reached more than 620mph (1,000km/h) – Mach 0.92 – as it plunged towards the ground.

Martindale was saved by simple physics. With the heavy propellers wrenched off, the aircraft was now tail-heavy, and this change in the centre of gravity forced it to climb up from the dive at great speed. Martindale was knocked unconscious from the stress of the climb, and woke to find his aircraft flying at 40,000ft (13 kilometres). Somehow he managed to glide the aircraft back to his base, and emerged unscathed. The stress of the plane’s dive had bent the wings, giving them a slightly swept shape – the kind of shape that would eventually help other aircraft travel through the sound barrier.

Martindale was lucky to survive when his high-speed dive ripped the propeller blades off his Spitfire (Credit: Crown Copyright)

This warping would have been caused by the airflow over the wing as the plane picked up speed, explains Rod Irvine, the Royal Aeronautical Society’s aerodynamics group chairman. “When you start approaching Mach 0.85 or 0.95, what happens is you get this subsonic flow over the wing, and it starts to accelerate beyond the sound barrier,” he says. “It starts to flick around all over the place, and it feels like the aircraft is starting to shake itself to bits because you get this fundamental change in the aerodynamics.” Irvine says this problem remains today – airliners such as the Airbus A380 will travel as fast as they can without causing the air flowing over the wings to reach supersonic speed, which can create vibrations and buffeting.

Planes remaining in use [ edit | edit source ]

Preserved Spitfire at Duxford.

About 50 Spitfires and a few Seafires remain airworthy, although many air museums have static examples. The RAF maintains some for flying display and ceremonial purposes in the Battle of Britain Memorial Flight at RAF Coningsby in Lincolnshire.

The Temora Aviation Museum in Temora, Australia, have two airworthy Spitfires: a Mk VIII and a Mk XVI, which are flown regularly during the museum's flying weekends.[2]

Area51Aviation, a British company specializing in ex-military aircraft (particularly jets) have both a Spitfire and Seafire at their Home Airfield at North Weald Airfield.[3]

The Black Spitfire is a black-painted Spitfire which belonged to Israeli pilot and former president Ezer Weizmann. It is on exhibit in the Israeli Air Force Museum in Hatserim and is used for ceremonial flying displays.

Kermit Weeks flys a restored Mk XVI from his Fantasy of Flight museum in Florida.[4]

How The Spitfire’s Gunsight Drastically Changed Our View Of Fighter Planes

The Supermarine Spitfire is arguably the best fighter plane of World War II after its role in the Battle of Britain. Even German Luftwaffe pilots had a deep respect for the stellar performance of the Spitfire when pitted in battle against it. One of the features that set the Spitfire apart from the rest of the crowd was its guns and they went through quite an evolution.

The Supermarine Spitfire had several machine gun ports fitted inside its wings, which made it more aerodynamic to reduce drag. However, internal gun ports rather than external ones created a difficult learning curve for engineers playing with the gun sights. The Spitfire could fire nearly 480 rounds per minute using its eight guns but they needed precision in order to hit a target in the heat of battle.

Pilots were required to learn a variety of visual tricks to prepare them for aerial combat including memorizing a variety of aircraft from different perspectives. But mainly learning to use the Spitfire’s gunsight became the most critical tool for successfully taking down hostile aircraft.

The Supermarine Spitfire’s gunsight went through an interesting evolution during WWII you can see the transitions in this video clip that kept it competitive throughout the war.

Watch the video: Supermarine Spitfire Griffon Engine Startup and taxi - Festa al Cel Barcelona Airshow 2012 (January 2022).