The 3.7-Inch QF AA was Britain's primary heavy anti-aircraft gun during Second World War. It was roughly the equivalent of the German 8.8 cm Flak 18 and the American 90 mm flak, but with a slightly larger calibre of 94 mm. It was used throughout World War II in all theatres except the Eastern Front. The gun was produced in six major variants. Ingame, we can accept the gun as the Mk.VI, because the Mk.VI is only used with a fixed mounting, wichgave vastly increased performance. During the First World War, anti-aircraft guns and anti-aircraft gunnery developed rapidly. The British Army eventually adopted the QF 3-inch AA gun as the most commonly used type and on sea the QF-2 Pounder. Shortly before the end of the war a new QF 3.6 inch gun was accepted for service but the end of the war meant it did not enter production. After the war, all anti-aircraft guns except the 3-inch gun were scrapped. However, the War had shown the possibilities and potential for air attack and lessons had been learned. The British had used AA guns in most theatres in daylight, as well as against night attacks at home. In 1925 the RAF established a new command, Air Defence of Great Britain, and the Royal Artillery's anti-aircraft units were placed under its command. In 1928 the general characteristics for a new HAA gun were agreed on; a bore of 3.7 inches (94 mm) firing 11 kg shells with a ceiling of 8,500 m. However, finance was very tight and no action was taken until the 1930s, when the specification was enhanced to a 13 kg shell, 910 m/s muzzle velocity, a 11,000 m ceiling, a towed road speed of 40 km/h, maximum weight of 8 tons and an into action time of 15 minutes. In 1934 Vickers Armstrong produced a mock-up and proceeded to develop prototypes of the weapon, which was selected and passed acceptance tests in 1936. However, the weight specification was exceeded and the muzzle velocity not achieved. Furthermore, the initial mechanical time fuse, No 206, was still some years from production so the igniferous No 199 had to be used, and its lesser running time limited the effective ceiling. Gun production started the following year. On 1 January 1938 the British air defences had only 180 anti-aircraft guns larger than 50 mm, and most of these were the older 3 inch guns. This number increased to 341 by the September 1938 (Munich Crisis), to 540 in September 1939 (declaration of war), and to 1,140 during the Battle of Britain. Production continued until 1945, averaging 228 guns per month throughout the period. Being a high velocity gun, with a single charge and firing substantial quantities of ammunition, meant that barrel life could be short. By the end of 1940 the barrel situation was becoming critical. Some of the substantial numbers of spare barrels required were produced in Canada. Two versions of gun were produced. One used a travelling carriage, for use by batteries in the field army. This consisted of a wheeled carriage (Carriage Mk I or Mk III) with four foldable outrigger trails and levelling jacks. The wheels were lifted off the ground or removed when the gun was brought into action. The other used a travelling platform (Mounting Mk II) with detachable wheels for guns to be used in static positions, but which could be re-positioned. The mounting had a pedestal that was fixed to a solidly constructed, preferably concrete, platform on the ground. In both cases the saddle rotated 360° on the carriage or pedestal and provided elevation up to 80°. An AEC Matador was the normal gun tractor.
In FHSW, the gun appears as single gun or in battery of 3 guns on the Radar Tower (Battle of Britain). The guns appears not on ships! This is the QF 4 inch Mk XVI naval gun (ingame note as the 10.2 cm QF Mark XVI), but it is the same ingame model as the 3.7 inch QF AA. Same for the American 3 Inch Battery (76.2 cm M3).