Ground staff service a Spitfire 485 Squadron RNZAF
The Spitfire II was the initial model produced by the Castle Bromwich Aircraft Factory (CBAF) in Birmingham, a facility responsible for more than half of the total Spitfire and Seafire production. The prototype, which was a modified Mk.I, first took flight in September 1939, and the first production aircraft from the new plant emerged in June 1940. The CBAF faced numerous initial challenges that led to delays. Originally managed by the Nuffield Organisation, the facility underwent significant changes when Lord Beaverbrook, the new Minister of Aircraft Production, ordered a management overhaul. Consequently, Vickers-Armstrong took control of the factory. The first operational squadron to receive the new Spitfire II was No. 611 Squadron at Digby, in August 1940, and a few of these aircraft participated in the Battle of Britain.
The Mk.II differed from the Spitfire I by featuring the more potent Merlin XII engine, which, thanks to its use of 100 octane fuel compared to 87 octane, allowed for higher supercharger boost pressures and, thus, greater power. Other modifications included replacing the electrical starting system with a Coffman cartridge starter and enhancing the pilot’s armor protection from the ground up.
Out of the total production, 170 Spitfire IIs were completed as Mk.IIBs, equipped with a ‘B’ wing configuration that included two cannons and four machine guns. This variant introduced a redesigned feed and ejection system for the 20mm ammunition and mounted the guns on their sides, creating the distinctive ‘B’ wing blister on the upper wing. This configuration improved the reliability of the cannon installation, addressing the jamming issues of the Mk.IB.
In 1942-43, fifty Spitfire IIs were converted into Mk.IICs (later designated ASR.II) for air-sea rescue missions, designed to operate in the Thames Estuary and the English Channel. These modified aircraft were equipped to drop flares, rescue packs (including dinghies and rations), and smoke bombs from rear fuselage chutes, with additional smoke marker bombs carried on underwing racks. Furthermore, these rescue aircraft were upgraded with the more powerful Merlin XX engine, offering 1,460 horsepower (1,089 kW) and a 2-speed/1-stage supercharger. The ASR.II model served with five search and rescue squadrons.