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Aviation History
1946
1946 - 0113.PDF
JANUARY 17TH, 1946 FLIGHT THE LINCOLN'S DEFENCE of the mounting ring, which is immediately above the air-bomber's seat position. Controls, sight linkage and sight extend from the turretinto the bomb-aiming compartment below, and the gunner sights through the transparent nose of the aircraft whilstoccupying the normal bomb-aimer's seat, which is fixed and does not rotate with the turret. The turret can berotated to 45 deg. each side of the fore-and-aft centre line of the aircraft, and the guns can be elevated or depressed40 deg. above or below the horizontal. Both guns are 0.5m. Brownings, with a rate of fire ofapproximately 750 rounds per minute each, and an ammu- Jution supply of 275 rounds per gun is carried in the turret. The turret structure is mounted on a ball-bearing mount-ing ring, the fixed ring of which is attached to the aircraft decking, and the guns are mounted parallel and closetogether on a central gun chassis with a special recoil damper fitted on the front of each gun. Mountings aredesigned to permit quick release of the guns by the action of a single lever. Actuation A hydraulic motor is used to supply the power forrotating the turret and a ram supplies the power for elevat- ing and depressing the guns. Both the motor and the ramare supplied from the hydraulic generator, which functions in a similar manner to that described for the tail turret. Each pump of the generator is connected to the turretcontrols, which take the form of a pair of handles con- nected together by links and pivotable about the verticaland horizontal axes. To elevate and depress the guns the handles are pivotedbackwards and forwards, and to rotate the turret they BELT FEED MECHANISM CON CRADLE BRACKET EMPTIES OH'1" SHAFT FOR FEED A5SISTERLOADING HANDLE CANVAS EMPTIES BAG FEED CHUTC GUN ELEVATION SCPEWJACK-1 CUPOLA TURRET ROTATION MOTOR- -R.H AMMUNITION BOXfLHBOX 1 (NOT SHOWN] — UNDER STRUCTURE ROTATING SERVICE JOINT MOTOR GENERATOR UNIT AMMUNITION BOX The feed of 20 mm. ammunition to the breeches of thecannon in the Bristol mid-upper turret. are pivoted to right or left, a combination of thetwo movements permitting the guns to be aimed at any point within the field of fire. Inter-com-munication, call light and oxygen equipment are all installed in the aircraft nose, so that only twopower leads have to be brought into the turret, and for this purpose trailing cables extend fromthe fuselage to the rear of the turret. Ammunition Feed Ammunition is contained in two detachableboxes, one for each gun, located outboard of each of the two vertical members of the turret frame,and ducts are provided to guide the belts from the boxes to the sides of the gun chassis. Eachof these incorporates a feed roller to allow the belt to feed smoothly from the box into the duct, anda large conical roller to twist the belt through the 90 deg. made necessary by the relative positionsof boxes and guns. Empty cartridge cases and links are ejectedthrough apertures in the gun chassis into, a conical drum attached to the underside of the cradle.The drum directs the empties through passages in the vertical members into the containers belowthe ring level, which are emptied through quick- release doors.A cupola encloses the upper structure of the turret and consists of a frame built up of anglemembers panelled with sheet metal. Trans- parent panels are not necessary, as sighting andsearching are done through the windows in the bomb-aimer's compartment. Small transparentsections are provided in the cupola, and the two large de-tachable doors are fitted at the rear for servicing purposes. The decision to use a heavierdefensive armament than that provided by rifle calibre guns Layout of theB-17 turret show- ing its principalcomponents.
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