In the course of 1940, the Spitfire Mk.I large scale production at Supermarine company has been fine-tuned so it
could meet the Air Ministry orders, supply the RAF Fighter Command combat units with the new aircraft and replenish the combat losses. The situation was similar at Castle Bromwich Aircraft Factory in Birmingham which after
some initial organizational problems reliably supplied the fighter squadrons with license-built, and, compared to
Mk.I, slightly improved Spitfires Mk.II.
SPITFIRE Mk.V HISTORY
In the end of 1940, the new aircraft were arriving at the units fax Mk.Il and Mk.V. There were none left for Spitfires and the
in their final weapon and equipment configuration as full-fled- idea of an accelerated, large-scale Spitfire Mk.III production
ged, fully functional combat aircraft. Earlier manufactured was silently swept under the table. The smaller series of photoairplanes were continuously upgraded with the installation of -reconnaissance Spitfires PR Mk.III was manufactured under the
armor and more modern equipment to meet the standards of same designation, mostly by converting Spitfires Mk.I.
the newly manufactured Spitfires. However, during the same
time, the modernized Bf 109 versions were arriving at the German Luftwaffe fighter units. The Spitfires were able to keep up Merlin 45
the pace with Bf 109E-7 quite successfully when they appeared Once the Merlin XX installation proved to be more and more
in the fall 1940, but with the arrival of Bf 109F-1 and F-2 in the complicated, in the end of 1940 Rolls-Royce company offered
end of 1940 and beginning of 1941, the tables turned in favor a feasible and fast solution in the form of parallelly developed
of the Germans. In order to counter the growing German tech- and easier to manufacture engine Merlin RM5S later marked
nical supremacy, the Spitfires’ performance had to be improved Merlin 45. It featured a one-stage, single-speed compressor oprapidly.
timized for high altitudes, its output at 5,400 meters was 1,210
A traditional way to increase the aircraft performance is to in- hp (902 kW), some sources state rather optimistic, and to tell
stall the more powerful engine. The first attempt to develop a the truth, less probable output of 1,440 hp (1,074 kW). Merlin
more powerful Spitfire version was the project Improved Spitfi- 45 had the same dimensions as Merlin III powering Spitfires Mk.I
re, later renamed Superiority Spitfire, launched as early as the and its design enabled Merlin III upgrade to Merlin 45 standard
beginning of 1939. The prototype with the factory designation by replacing the compressor. This facilitated the simple instaType 330 and military one as Spitfire Mk.III was ready for its llation into the current Spitfire Mk.I and II airframes and the
maiden flight in March 1940. It was designed by modifying the conversion of the already manufactured aircraft as well. RR
standard Spitfire Mk.I serial number N3927. The airframe was company promised to supply 300 Merlin 45 by March 1, 1941
modified by installing a new Rolls-Royce Merlin RM 2SM engi- and further 200 by April 1.
ne, the future Merlin XX, featuring a single-stage, two-speed The first airframe to receive the new engine, modified from
compressor with the maximum output of 1,320 hp (1,037 kW). Merlin XX, was supposedly Spitfire Mk.I K9788 on December 26,
In order to accommodate Merlin XX, the engine bearers were 1940, in Boscombe Down. It was followed by PR Mk.III X4334,
strengthened and the nose lengthened by four inches.
converted into the photo-reconnaissance version from Spitfire
The wingspan was shortened to 9.30 meters by removing the Mk.I, which took to the air on January 13, 1941, from the Rolls
wingtips and shortening the ailerons while the internal design Royce factory airport in Hucknall. Spitfire Mk.I N3053, too tesremained unchanged. During the flight trials, the prototype t-flown on February 13, 1941, in Hucknall, was another converapparently never reached the calculated maximum airspeed of sion. Right after both airplanes were flown over to Boscombe
644 kph at 6,400 meters, the maximum recorded speed is said Down for further testing. The flight trials recorded the maxito be 620 kph which was still an outstanding improvement in mum speed of 593 kph at 6,100 meters was recorded during
comparison to Mk.I performance. Air Ministry demanded that the flight trials, climbing time to this altitude was 6 min and
the large-scale production of Spitfire Mk.III was accelerated, 12 seconds and the operational ceiling 11,590 meters. The trial
however there was a serious obstacle to this effort due to the also discovered the problems with the constant-speed propelcomplicated development of Merlin XX and teething troubles lers De Havilland when oil in their control system was freezing
with its large-scale production. In the fall 1940, the available at high altitudes. There were troubles with the Mk.II oil cooler
engines were utilized for Hurricane Mk.II and Defiant Mk.II up- as well as it was not efficient enough for the more powerful
grades and they were also installed in Bristol Beaufighter Mk.II, engine. Even though this was considered an interim solution, as
Avro Lancaster B Mk.I, Mk.III and Mk.IV and Handley Page Hali- the Spitfire Mk.III production was still being planned, the order
INFO Eduard - January 2022