Супермарин Спитфайер: Кейінгі Merlin қозғалтқыштарының нұсқалары

Late Merlin powered variants of the Supermarine Spitfire

The British Supermarine Spitfire was facing several challenges by mid 1942. The debut of the formidable Focke Wulf Fw 190 in late 1941 had caused problems for RAF fighter squadrons flying the latest Spitfire Mk Vb. Rolls Royce engineers were already working on a new version of the Merlin incorporating a two stage supercharger; the combination of the improved Merlin and the Spitfire Mk Vc airframe in a "stop gap" design allowed the RAF to combat the Fw 190 on equal terms. In a second stream of development Supermarine was working on an improved, reinforced, Spitfire airframe which incorporated several new features and was designed for the Merlin 60 and 70 series engines. This new airframe later formed the basis for the Rolls Royce Griffon powered Spitfires. This article presents a history of the Spitfire powered by two stage engine variants and also describes some of the "drawing board" projects and experimental Spitfires. The Griffon powered variants are described in a separate article.

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. 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. Because the Spitfire was no longer to be used as a night fighter, the retractable landing lights were no longer fitted. Although many earlier Spitfires had been modified to carry bomb racks capable of carrying bombs the first Spitfires to be specifically modified for the fighter bomber role (known as Modification 1209) were those of the Second Tactical Air Force. The first Mk IX Spitfires started being used in the role in June 1944.

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.

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.

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 (a bulge) for a Coffman engine starteron 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 like bulge 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. The indicator rods seemed to be fitted on all Mk VIIs and VIIIs, supplementing the electric visual indicator. A light for the retractable tailwheel was mounted on the instrument panel, just below the main visual indicator. Maximum power of the Merlin 70 was at 11,000 ft (1,275 kW at 3,353 m): maximum speed of the Spitfire HF Mk IX was at
25400 feet (7742 m) at an all up weight of 7,320 lb (3,320 kg). 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. 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. 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 1200 mile (1931 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. 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.

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. 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. 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 IXc 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.

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. 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.

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. 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. 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. 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. 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. PR Mk XIs used for tactical reconnaissance had an additional, vertically oriented camera in a fairing under each wing.

Supermarine 305: Designed to the same F.9/35 specification which led to the Boulton Paul Defiant turret fighter (and the rejected Hawker Hotspur). The basic F.37/34 (as Spitfire was still then known) wing and undercarriage were mated to a modified fuselage which provided room for a gunner and a remote control four gun turret (originally armed with .303 Brownings, later with Lewis light 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). Supermarine 312: To F.37/35 for a cannon armed fighter. 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. A separate twin engined design to the same specification was also offered. The Ministry rejected the 312 as Supermarine's design office was already too fully engaged on the Spitfire design to work on the alternative wing. The twin engined Westland Whirlwind was accepted for the specification. Supermarine 324, 325 and 327: These designs were for twin engined fighters to F.18/37 (which was for the successor to the Spitfire and Hurricane) 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. Two designs from Hawker which led to the Hawker Typhoon and Hawker Tornado were selected. The Type 327 was considered for a while as it offered cannon armament but the Whirlwind, the Bristol Beaufighter and Gloster F.9/37 were already in development.

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 more detailed explanation can be found in Supermarine Spitfire. The main Castle Bromwich factory was also aided by a smaller number of the shadow factories. As the first of the Mk IXs were converted from Mk Vcs the first true production Mk IX is listed by serial Number. +Production by Mark Mark Builder Number Notes F VII, H. F VII Supermarine 140 First Mk VII September 1942 F VIII, L. F VIII Supermarine 1,658 First Mk VIII 11 November 1942 F IX, H. F IXL. F IX SupermarineCastle Bromwich 5,656 First Mk IX BR581 June 1942 PR X Supermarine 16 First Mk X May 1944 PR XI Supermarine 471First Mk XI November 1942 XVI Castle Bromwich 1,054 First Mk XVI October 1944