Defiant gunner in his turret, No. 264 Squadron RAF 1940
The Boulton Paul Defiant fighter was centered around the Type A turret, and the initial production model was designated as the Type A Mk IID. The D indicated that it was specifically designed for the Defiant, setting it apart from the slightly different model used in the Blackburn Roc naval fighter. Both installations featured a unique retractable fairing system. Pneumatic rams, supplied from a fuselage-mounted bottle, held the front and rear turret fairings in the “Up” position. As the guns approached one of the fairings, an air valve closed, causing the fairing to drop into the “Down” position, allowing the guns to traverse past it. The Type A Mk IID turret proved to be an efficient design, with its low profile minimizing drag on the aircraft. The Hele-Shaw-Beacham hydraulic variable gear system ensured a smooth and precise movement in both traverse and elevation. The gunner’s view, though not ideal, was reasonably clear to the front and directly on each side. The presence of the guns and feed mechanism somewhat obstructed the gunner’s view, but it remained manageable. The turret housed four Browning guns, arranged in pairs on either side, while the gunner’s control table was located to the front, equipped with the necessary operating equipment.