30.09.2008, 16:58
Ok, brief chronology.
Spitfire MKIX starts with MKIII. This aircraft was designed to evaluate fitting the Merlin 60 series engine with the two stage/two speed supercharger to the Spitfire. Was to lead to the MKVII and MKVIII which were supposed to be definitive versions of the Spit. Used a slightly modified V airframe.
February 1942 - Due to the threat posed by the Focke Wulf, urgency was given to fitting the Merlin 61 to the Spitfire Vc airframe with as few changed as possible, using the information from the earlier MKIII such as the symmetrical radiator arrangement proposed for the VII/VIII
February 26 1942 - First test aircraft flown
June 1942 - MKIX enters production with Merlin 61
July 1942 - MKIX enters squadron service with 64Sqn.
Initially, 280 Vc airframes were converted to MKIXs. These aircraft distinguishable from later IXs by identification light on the spine, wider cannon blisters, u/c indicator on the top of the wing towards the trailing edge. Later aircraft did not have these features.
1943 - From the beginning of 1943 the Merlin 61 was replaced in the F.IX by the Merlin 63. Minor differences only, no designation change.
March 1943 - Spitfire LF.IX with the Merlin 66 entered service. This was the major production variant of the MKIX and the engine was optimised for lower altitude work.
March 1943 - Spitfire VII enters service with a redesigned fuselage, extra fuel capacity, retractable tail wheel, modified ailerons and horn balances and with the broad chord and pointed rudder. This rudder adapted for use on Spitfire IX from about this point.
June 1943 - Spitfire VIII enters service .Similar to the VII and with the same strengthening and aerodynamic improvements as the VII that were lacking from the IX. Importantly for the IX though, the Voke aero-vee tropical filter (which had been specifically designed for the VIII) entered service with this aircraft. The filter was then adapted for the MKIX and used on production IXs from about this time.
August 1943 - Production of Merlin 63 powered F.IX discontinued.
Early 1944 - Spitfire HF.IX enters service with Merlin 70 engine, optimised for high altitude work. Only about 400/500 produced.
August 1944 - 'e' wing with 2 cannon and 2 .5" machine guns begins to be fitted to Spitfire IXs, creating the IXe. Earlier aircraft retrospectively designated IXc. Up until this point all MK.IX aircraft had been fitted with the 'c' wing using either the 4 cannon or 2 cannon and four machine gun armament. The 8 machine gun option available with the 'c' wing was never fitted to the MKIX.
September/October 1944 - MKXVI enters production and service. Essentially a MK.IX, the XVI was fitted with the Merlin 266 (an American Packard built Merlin 66. The prefix '2' was used because the 266 used metric measurements and required different tools). The slight differences between the merlin 66 and the Packard Merlin 266 required the XVI to have a slightly bulged upper engine cowling. This revised cowling was also used on IX aircraft from this point. All MKXVI aircraft entered service with the 'e' wing and with clipped wingtips. Referred to as Spitfire LF.XVIe.
January/February 1945 - 'Bubble' canopies and cut down rear fuselage introduced to the MKIX/XVI.
Couple of notes:
Clipped wings did not relate to the engine optimisation. While many (most, i think) LF models used the clipped wingtips, some did not. Even some of the XVI aircraft had the standard wingtips fitted at squadron level. HF. Models of the SpitIX didn't use the extended wingtips of the VII, as they were found to offer little benefit.
The four cannon variant of the IX was quite rare, but did exist. The MKIXc and the MKVIII couldn't carry bombs under the wings while the four cannon were fitted though, due to the thickness of the wing. It was for that reason that the cannon were moved to the outboard bays on the 'e' wing.
Spitfire MKIX starts with MKIII. This aircraft was designed to evaluate fitting the Merlin 60 series engine with the two stage/two speed supercharger to the Spitfire. Was to lead to the MKVII and MKVIII which were supposed to be definitive versions of the Spit. Used a slightly modified V airframe.
February 1942 - Due to the threat posed by the Focke Wulf, urgency was given to fitting the Merlin 61 to the Spitfire Vc airframe with as few changed as possible, using the information from the earlier MKIII such as the symmetrical radiator arrangement proposed for the VII/VIII
February 26 1942 - First test aircraft flown
June 1942 - MKIX enters production with Merlin 61
July 1942 - MKIX enters squadron service with 64Sqn.
Initially, 280 Vc airframes were converted to MKIXs. These aircraft distinguishable from later IXs by identification light on the spine, wider cannon blisters, u/c indicator on the top of the wing towards the trailing edge. Later aircraft did not have these features.
1943 - From the beginning of 1943 the Merlin 61 was replaced in the F.IX by the Merlin 63. Minor differences only, no designation change.
March 1943 - Spitfire LF.IX with the Merlin 66 entered service. This was the major production variant of the MKIX and the engine was optimised for lower altitude work.
March 1943 - Spitfire VII enters service with a redesigned fuselage, extra fuel capacity, retractable tail wheel, modified ailerons and horn balances and with the broad chord and pointed rudder. This rudder adapted for use on Spitfire IX from about this point.
June 1943 - Spitfire VIII enters service .Similar to the VII and with the same strengthening and aerodynamic improvements as the VII that were lacking from the IX. Importantly for the IX though, the Voke aero-vee tropical filter (which had been specifically designed for the VIII) entered service with this aircraft. The filter was then adapted for the MKIX and used on production IXs from about this time.
August 1943 - Production of Merlin 63 powered F.IX discontinued.
Early 1944 - Spitfire HF.IX enters service with Merlin 70 engine, optimised for high altitude work. Only about 400/500 produced.
August 1944 - 'e' wing with 2 cannon and 2 .5" machine guns begins to be fitted to Spitfire IXs, creating the IXe. Earlier aircraft retrospectively designated IXc. Up until this point all MK.IX aircraft had been fitted with the 'c' wing using either the 4 cannon or 2 cannon and four machine gun armament. The 8 machine gun option available with the 'c' wing was never fitted to the MKIX.
September/October 1944 - MKXVI enters production and service. Essentially a MK.IX, the XVI was fitted with the Merlin 266 (an American Packard built Merlin 66. The prefix '2' was used because the 266 used metric measurements and required different tools). The slight differences between the merlin 66 and the Packard Merlin 266 required the XVI to have a slightly bulged upper engine cowling. This revised cowling was also used on IX aircraft from this point. All MKXVI aircraft entered service with the 'e' wing and with clipped wingtips. Referred to as Spitfire LF.XVIe.
January/February 1945 - 'Bubble' canopies and cut down rear fuselage introduced to the MKIX/XVI.
Couple of notes:
Clipped wings did not relate to the engine optimisation. While many (most, i think) LF models used the clipped wingtips, some did not. Even some of the XVI aircraft had the standard wingtips fitted at squadron level. HF. Models of the SpitIX didn't use the extended wingtips of the VII, as they were found to offer little benefit.
The four cannon variant of the IX was quite rare, but did exist. The MKIXc and the MKVIII couldn't carry bombs under the wings while the four cannon were fitted though, due to the thickness of the wing. It was for that reason that the cannon were moved to the outboard bays on the 'e' wing.