Tail gunner

A tail gunner or rear gunner is a crewman on a military aircraft who functions as a gunner defending against enemy fighter attacks from the rear, or "tail", of the plane. The tail gunner operates a flexible machine gun emplacement in the tail end of the aircraft with an unobstructed view toward the rear of the aircraft. While the term tail gunner is usually associated with a crewman inside a gun turret, the first tail guns were operated from open apertures within the aircraft's fuselage, like in the Scarff ring mechanism used in the British Handley Page V/1500 (a 1918 aircraft), and also, in the most evolved variants of this type of air-to-air anti-aircraft defense, they may also be operated by remote control from another part of the aircraft, like in the American B-52 bombers (an aircraft first introduced in 1955 but still in service).

The tail gun armament and arrangement varied between countries. During World War II, most United States Army Air Forces heavy bomber designs such as the Boeing B-17 Flying Fortress and Boeing B-29 Superfortress used a fixed gunner position with the guns themselves in a separate mounting covering an approximately 90-degree rear arc. Typical armament was two 0.50 inch M2 Browning machine guns.

In contrast, Royal Air Force heavy bombers such as the Avro Lancaster and Handley Page Halifax used a powered turret capable of 180-degree rotation containing the tail gunner and four 0.303 inch Browning machine guns. A similar arrangement was used in the American B-24 Liberator heavy bomber (but with two 0.50 inch heavy machine guns.) Most British turrets were manufactured by two companies Nash & Thomson and Boulton & Paul Ltd and the same turret model was fitted to a number of different aircraft.

...
Wikipedia