The Sperry Power Operated Gun Turret- Upper Local-Operation and Maintenance Manual- Part One General Operation

1943. Staple bound imprinted wrappers. Square 24mo.5"x4". 69 monochrome illustrated pages (one side only) presented in film strip fashion. The Sperry Model A-1 Mid-upper Turret During the Second World War Boeing Flying Fortress Mks. II, IIA and III (B-17E, F and G) aircraft were operated by a number of RAF Coastal Command sqds as maritime patrol and weather reconnaissance aircraft, as well as being operated by by Nos.214 and 223 Sqds of No.100 Group, RAF Bomber Command as radio warfare aircraft. These famous bombers were fitted with Sperry turrets armed with twin 12.7 mm (0.5 in) Browning guns. In 1940 the US Army Air Corps had been conferring with (truncated) the Sperry Gyroscope Company, as well as other manufacturers concerning the design of turrets for bombers. it was known that several British companies had developed enclosed power-operated turrets for the RAF, and the facility at Wright Field had acquired some Boulton Paul and Nash and Thompson turrets from Britain for appraisal. These turrets were studied by the engineers of the companies nominated to submit designs for the Air Corps, and were used as the basis of the first design. Sperry designers, in association with Steel Products Engineering of Sprigfield, Ohio, designed a turret mounting two 12.7 mm (0.5 in) Browning guns. The Sperry K-2 automatic computing gunsight was also modified for use in turrets, and in the summer of 1940 the company received a contract covering the purchase of 540 local control mid-upper turrets and 113 lower remote-control turrets to be fitted with automatic computing sights. The Steel Products Company were brought in as sub-contractors to manufacture the turrets, and the prototype mid-upper turret design was delivered to the Boeing plant at Seattle. It was installed in a B-17C Flying Fortress in November 1940 for flight and firing tests. On 22nd August, 1941 a conference was held at Wright Field at which Sperry representatives requested to be relieved of responsibility for turret production to concentrate on new turret designs. The mid-upper turret and under-defence ball turrets were adopted as standard for the Boeing B-17E Flying Fortress, but the lower remote turret was not accepted for service use. It was found that in common with the Bendix and British remotely controlled under defense turrets, visibility through the periscopic sight was unacceptable, for an attacking fighter could not be tracked in the few seconds of the firing pass. The Sperry Model A-1 mid-upper turret served with distinction on B-17s on many war fronts. It was powered hydraulically by a self-contained electro-hydraulic unit. The gunsight gave the gunner a computed impact point, being developed from the larger K-2 computer-controlled sight, and was known as the Model K-3 (the inverted K-4 was fitted to the ball turret). Visibility was restricted in the first Model A-1s; two metal segments of the cupola to the sides were criticised by gunners, and were replaced by Perspex sections manufactured in the UK for the Eighth AAF in Europe. This modification was soon adopted on the production line. The gunner could enter the turret from the pilot's cabin or, as was usually the case on an operation, over the bomb bay, when he had to crawl between two columns, turn round, and then rise from a stooped position to stand in the turret. The footrests were adjusted so that the gunner's eyes were behind the optical head of the sight. There was also a sling-type seat which he could clip under him. He then engaged the rotation and elevation clutches, using small crank handles above the ammunition cans. The main circuit-breaker near his left shoulder was switched on, and the sight rheostat adjusted for brightness. In front of the control handles were the ammunition booster motor switches, which were closed. The twin handle controller was operated in the normal way, with the exception that the right handle incorporated a twist grip which adjusted the sight reticules to the size of an attacking fighter. On the left handle was a safety lever which ensured the turret could not move unless the gunner was in position. Triggers were mounted under the index fingers and a press-to-talk button controlled by the left thumb. A simple method of cocking the guns was by means of two handles suspended from pulleys in the roof of the cupola, which pulled back the charging handles of the guns. Oxygen was supplied from a demand-type regulator under the control unit, below which was the heated-suit plug. The interphone jacks for the gunner's headphones and throat microphones were situated in a junction box near his left shoulder. A trouble light and switch were mounted in a small box forward of the oxygen, and a Fairchild gun camera could be mounted on the left side of the sight cradle. The twin 12.7 mm (0.5 in) Browning M2 guns were fed from 125-round ammunition cans which were loaded from the front of the turret, they were loaded with the rounds pointed to the outside of the turret, pushed forward on to rollers and clipped into position. using two 25-round lengths of ammunitions feed strips the rounds were fed into the gun feedway and over the booster-unit sprockets. The single link of the feed strip belt was then fixed on to the double link of the leading belt link in the can, using a single round to join them. Each gun was fed from three 125-round cans which were linked together giving a continuous 375-round belt. The cans could be reloaded during a lull in firing. Fastened to the gun's ejection chute were canvas bags to collect the spent rounds. The Sperry K-3 computer gunsight gave a computed impact point. Information fed into the sight was (1) rate and direction of rotation, (2) angle and direction of elevation, and (3) range given by the gunner adjusting the illuminated sighting graticules and position of aircraft-type indicator set by gunner on the sight body. The Sperry A-1 was a very efficient turret which, with an experienced gunner able to track smoothly and use the sight to advantage, posed a threat to any attacking fighter. Details of the Sperry Model A-1 Mid-upper Turret. Aircraft Type: Boeing Flying Fortress Mks. II, IIA, and III (B-17E, F and G) Position in aircraft: Mid-upper Armament: Two 12.7 mm (0.5 in) Browning M2 guns Ammunition: Three 125-round rechargeable cans Gunsights: Sperry K-3 computing sight, also fitted with ring-and-bead as standby. Gunfire interrupter: Limit stops preventing mechanical damage, fire cut-off system preventing fire damage to airframe. Field of fire: Traverse: 360 degrees Elevation: 0 degrees to 85 degrees Depression: n/a Motive power: Electro hydraulic unit. Fire control: Electrical solenoid units. Turret speed: 40 degrees/sec.  Mild rolling to covers and text block. Lower edge apparently trimmed short (not affecting text or plates). Creases to several page edges. Short tears to some bottom page edges ( not affecting text or plates with the exception of bottom of one plate with small patch of photo peeled ).Usual oxidation to staples. Generally, a Very Good, crisp copy. (Inventory #: 6243)