British Power-Operated Gun Turrets

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Robert Hurst
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Postby Robert Hurst » 26 Apr 2003 10:04

Hi

The Boulton Paul Aircraft Ltd

The Boulton Paul Type H Mid-upper Turret

The Type H turret Mk.II was a development of an early design project started in May 1939, to arm the Halifax and Stirling, with a twin-cannon armed dorsal turret, the BP Type H Mk.I, together with a proposed twin-cannon under defence turret, the BP Type O. These being cancelled before any metal was cut. The Later Mk.II project was ordered in February 1942 as an mid-upper turret for the Lancaster. It was to be armed by twin 20 mm (0.78 in) Hispanos or two 15 mm (0.59 in) cannon of a type developed by Vickers at Crayford*. The Vickers guns did not materialise, however, and the first prototype was a test-firing mock-up with 20 mm (0.78 in) Hispano guns. By September 1942 the company was ordered to give the project top priority, and five prototypes were requested by the Air Ministry on 14 September. By 23 September this number had been increased to six, together with a Lancaster mock-up.

By January 1943 the signs were that the Lancaster would soon be armed with a Type H mid-upper turret. The production drawings were 55 per cent compete, two prototypes were nearly finished and ground firing was scheduled for April. On 27 February a directive was received from the Air Ministry cancelling further development: the project was to be abandoned so that the company could concentrate on 12.7 mm (0.5 in) Type Ds, and an 'ideal' Lancaster front turret, the Type F, together with a remotely controlled barbette defensive system. Such were the frustrations of wartime design and production.

The main structure of the Type H turret comprised an upper section and skirt above the turret ring and a lower section below the ring. The upper part of the turret was divided into three: a central compartment, into which the gunner's head and shoulders projected, which had a central Perspex sighting panel to the front, and a gun compartment to each side. This arrangement protected the gunner from the considerable fumes given off when the Hispanos were fired. The empty cartridges and links were collected in boxes under the guns, after being deflected by side plates at the sides of the turret.

As can be seen in the illustration, the gunner sat well forward in the turret, his feet supported by an extension platform fixed to the turret base. He entered the turret from the front, by swinging the control table out horizontally. The turret had provision for emergency hand operation in rotation only, a feature which was meant for emergency escape. Gun elevation and firing could not be carried out with the power off. The Mk.IC gyro sight was mounted on a sight bar, connected by a parallel linkage system to the turret elevation control. The gunner was provided with a socket for heated clothing, the standard interphone jack, and a regulated oxygen supply. The turret was heavy, with guns and ammuntion it weighed 2,425 kg (1,100 lb). This would have been quite a penalty had it been accepted for use. The gunner was protected by an armoured apron extending round the front of the turret, the 12 mm (0.48 in) plates protecting all except his head. The electro-hydraulic power unit was mounted behind the gunner, giving a maximum rotation speed of 35 degrees/sec; a minimum speed of 0.25 degrees/sec could be achieved when adjusting aim. The guns were limited in traverse to 45 degrees either side of aft, with elevation limits of 50 degrees up and 9 degrees below horizontal.

Details of the Type H Mk.II Turret

Power system: Modified BP electro-hydraulic
Armament: Two 20 mm (0.78 in) Hispano Mk.II cannon
Ammunition: 300 rounds per gun
Ammuntion feed assisters: Drive sprockets for the two guns driven through separate electromagnetic clutches from a common electric motor. Clutches activated by belt tension.
Operating limits:
Traverse: 45 degrees
Elevation: 50 degrees
Depression: 9 degrees
Power requirements:
Voltage: 24 v
Current: Normal 50 amps; high speed 75 amps
Turrets speeds: Max: 35 degrees/sec; Min: Less than 0.25 degrees/sec
Gunfire interrupter: Electro-mechnical type proviidng separate control for each gun
Turret weight: Empty: 227 kg (500 lb); Armed: 449 kg (1,100 lb)
Gunsighting: GGS Mk.IC (proposed)
Turret dome: Not detachable, consisting of Perspex and metal panels mounted on frame members. The sighting panel could be powered to slide upwards leaving a clear space for night sighting
Turret sizes:
Overall height: 176 cm (69.25 in)
Dome diameter: 112 cm (44 in)
Dome to skin line: 65 cm (25.25 in)
Fuselage opening: 94 cm (36.75 in)

The Boulton Paul Type H Mk.I Turret

Aircraft type: Handley Page Halifax, Short Stirling
Type & Mark: H.Mk.I
Position: Mid-upper
Guns: 2 x 20 mm (0.78 in) Hispano Mk.II
Traverse:
Elevation:
Depression:
Status: Cancelled before production

The Boulton Paul Type O Mk.I Turret

Aircraft type: Handley Page Halifax, Short Stirling
Type & Mark: O Mk.I
Position: Mid-under
Guns: 2 x 20 mm (0.78 in) Hispano Mk.II
Traverse: 90 degrees
Elevation: 0 degrees
Depression: 70 degrees
Status: Cancelled before production

The following aircraft were fitted with the Boulton Paul Type H Mk. II
Turret

Aircraft: Avro Lancaster (Not allocated)
Type & Mark: H Mk.II
Position: Mid-upper
Guns: 2 x 20 mm Hispano Mk.II
Traverse: 90 degrees
Elevation: 50 degrees
Depression: 90
Status: Experimental

The above text and photos were taken from "British Aircraft Armament Vol.I: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob
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varjag
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Postby varjag » 26 Apr 2003 11:17

Rob - a SUPERB entry and much news to me. To quote Insp. Columbo - 'there's just one little detail that worries me' - HOW were the gunners on Defiant fighters supposed to escape in case of serious trouble...or did they not even bother with parachutes....?

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Robert Hurst
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Postby Robert Hurst » 28 Apr 2003 13:23

Hi

The Boulton Paul Aircraft Ltd

The Boulton Paul Type D Tail Turret Pt - 1

After four years of indecision the Air Staff finally issued production orders for turrets armed with heavy-calibre guns. Both Parnall and Boulton Paul had previously submitted designs for such turrets, but circumstances had prevented their adoption. Boulton Paul designers decided to embark on a completely new design which proved to be extremely roomy and efficient. The new turret was armed with 12.7 mm (0.5 in) Browning guns mounted low and to each side of the seated gunner. The turret had a fabricated structure, most of which was above mounting ring level, the guns being mounted upright in cradles. The ammunition supply was located in the centre fuselage well forward of the turret, thus placing the heavy boxes 255 kg (560 lb) when loaded near the centre of gravity. The structure of the turret consisted of two outboard members carrying the outer bearings of the gun cradle, and two inner sections supporting the inner bearings. The gun mountings were quite substantial, being strengthened Type T turret mountings. The turret was designed for the Mk.IC gyro sight, but this was replaced by the improved Mk.IIC gyro. The sight was mounted on a horizontal tube supported by two levers which were connected to the torque tube to move in harmony with the gun cradles.

The power system was the usual electro-hydraulic unit, with one modification - the elevation mechanism was changed from a hydraulic ram to a hydraulic motor, which was found to be more accurate in control at slow speeds. The gunner sat at his control table with the well-proven controllers to his front, while his central sighting panel was supported in channels which permitted it to slide downwards, leaving an open aperture when conditions were such that sighting through the panel was difficult. Two side panels were also arranged to slide open if needed. The turret doors were mounted on tracks, the two doors meeting in the centre and locking automatically when the outer edges were pushed outwards. There was provision for hand turning the turret in the event of power failure. The 'Free' and 'Engaged' lever was set to the 'Free' position, which automatically broke the gun-firing circuit and disengaged the drive. If the gunner was incapacitated, the turret could be turned by pressing a switch in the fuselage outside the turret, which enabled the dome to be turned until the doors could be opened and the gunner taken out.

The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 28 Apr 2003 14:20

Hi

The Boulton Paul Aircraft Ltd

The Boulton Paul Type D Tail Turret - Pt 2

The heavy ammuntion belts were stored in boxes in the rear fuselage, and the feed mechanism worked as follows: when the firing button was pressed, an electrical relay was energised which switched on powered sprockets which pulled the belts out of the boxes, feeding them through ducting to the 90 degrees bends at the turret base. Ammunition feed assisters then hoisted the belts into the guns, which were controlled by clutches which engaged when the belts reached a preset tension, ensuring an even feed. The guns were fired by Dunlop Maxifort solenoids, and cocked by hand lever chargers of BP design. The gun barrels were aligned with the sight by lock nuts on the rear support mounting, the guns being usually set to converge at 549 m (600 yds). The electrical load of the turret was considerable, a load of 130 amps was needed, and the maximum load of the main drive motor was 330 amps during the start sequence, though the average was 45 amps. Gun heater, feed assisters, and firing solenoids all needed considerable power, and after problems with the circuit breakers on full load, arrangements were made to cut off the gun and the AGLT scanner heaters (see below), when the guns were fired. An accumulator charged by the aircraft generator supplied the 24 volt power, all fuses and circuit breakers being in easy reach of the seated gunner.

As mentioned above, the guns were sighted by the Mk.IIC gyro sight, the range control of the sight being operated by the gunner's right foot. The selector dimmer and height and airspeed control boxes were fixed on the right hand gun chassis support tube. The sight switch and fire/safe switches were fitted to the top right of the control table. If a Mk.IIIA reflector sight was used, the graticule illumination was controlled by the rheostat on the sight. The Type D was the first to be fitted with the AGLT (airborne gun-laying turret) blind tracking radar system, codenamed Village Inn. The control panel for this was behind the gunner's right shoulder, the spot cut-off switch being fitted on the control table. A system of IFF (identification friend or foe) was devised, using an infra-red detector which would identify any friendly aircraft approaching from the rear fitted with an infra red lamp in the nose. The receiver, which used a 10,000 volt detector, was fitted to a bracket mounted to the left of the gunsight, the control box for the system being mounted between the gunner's legs. Gunners were not altogether happy with the mechanism, as they could imagine themselves being electrocuted in the event of battle damage or a loose connection.

The prototype turrets were manufactured at the company's Pendeford Lane works, where most of the development took place. The main production was undertaken by Joseph Lucas, where most Boulton Paul turrets were made. The first squadron aircraft to be fitted with the new turret was the Handley Page Halifax VII, which used the Type D in operations in the last months of the war. The turret was the contemporary of the Parnall FN.82 which was designed for the same specification, but after its successful use in the Halifax it was the Type D which was chosen for the Avro Lincoln heavy bomber, which served for many years after the war.

Several Type D turrets still exist, many having been rebuilt by enthusiasts. A prime example can be seen at the Royal Air Force Museum at Hendon, where it is exhibited on a stand.

Details of the Type D Turret

Position: Tail
Motive power: BP electro-hydraulic
Power source: Accumolators charged by aircraft generator
Operating voltage: 24 v
Armament: Two 12.7 mm (0.5 in) Browning No.2 Mk.II guns
Ammunition: 1,515 rounds per gun
Belt feed assisters: BP booster units, Dunmore motors
Firing system: Dunlop Magnovox solenoids Type 14 D.I:G:S
Gun chargers: Hand levers, BP design
Armoured shielding: 9 mm (0.354 in) plate. front aspect
Gunsighting: GGS Mk.IIC gyro sight, or Mk.IIIA reflector sight. Light models AGLT Blind Tracking Radar
Weight of turret:
Empty: 200 kg (440 lb)
Armed: 249 kg (548 lb)
Weight of guns: 33 kg (72 1/2 lb)
Weight of ammunition: 415 kg (914 lb)
Operating limits:
Traverse: 90 degrees either side
Elevation: 45 degrees above horizontal
Depression: 45 degrees below horizontal
Speed of operation:
Traverse: 35 degrees/sec
Elevation: 35 degrees/sec

The following aircraft were fitted with the Boulton Paul Type D Turret

Aircraft type: Handley Page Halifax B.Mk.VII; Avro Lincoln B.Mk.I & II
Type & Mark: D.Mk.II
Position: Tail
Guns: 2 x 12.7 mm (0.5 in) Browning No.2 Mk.II
Traverse: 180 degrees
Elevation: 45 degrees
Depression: 45 degrees
Status: Series production

A Summary of other Boulton Paul Turrets

Aircraft type: Avro Lancaster
Type & Mark: Not allocated
Position: Nose (barbette)
Guns: 2 x 20 mm (0.78 in) Hispano Mk.V
Traverse: Nil
Elevation: 30 degrees
Depression: 10 degrees
Status: Experimental

Aircraft type: Avro Lancaster
Type & Mark: Not allocated
Position: Mid-upper
Guns: 2 x 20 mm (0.78 in) Hispano Mk.V
Traverse: +/- 45 degrees
Elevation: 45 degrees
Depression: Nil
Status: Experimental prototype only

Aircraft type: Avro Lancaster
Type & Mark: Not allocated
Position:Mid-under
Guns: 20 mm (0.78 in) Hispano Mk.V
Traverse: +/- 45 degrees
Elevation: Nil
Depression: 45 degrees
Status: Experimental prototype only

The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 29 Apr 2003 13:51

Hi

The Boulton Paul Aircraft Ltd

The Boulton Paul Electro-hydraulic Power System - Pt I

The electro-hydraulic power system was selected because it made for compactness and simplicity. The most important feature of the design was that the hydraulic system was confined to the rotating parts of the turret, which avoided the difficulty and hazard of transmitting high-pressure fluid from the aircraft power source through continuously rotating joints.

Whole power units were built into the turrets, leads for the electrical power and other services being taken to a slip-ring unit on the axis of rotation. Installation of turrets on the production line and replacement of damaged turrets was simplified in that it consisted merely of lining up, bolting down, and connecting up the electrical services. All ground testing could be carried out before installation in the aircraft.

Motive power was supplied by a 24 volt DC electric motor running at 4,000 rpm. This was the top section of an integral unit which also contained the two hydraulic pumps that formed the hydraulic generator unit. The two pumps controlled the the separate actions of rotation and elevation, and incorporated blow-off valves set to blow-off at 71 kg/sq cm (1,000 lb/sq in). The motor was started when a grip lever was pressed on the control handle by the gunner. Since this operation was performed only when the gunner put his turret into operation, no power was required when the turret was not in use. The lever also served as a 'dead man's handle'.

Once the motor was running, the hydraulic generator was driven at 1,230 rpm, making power available for turret operation. The control handle was connected to the pumps by control slides - when the handle was moved the slide opened to release fluid to the pistons in the pumps, which activated the control required. An oil supply was carried in the pump which made up internal leakages, and 50 watt heaters were fitted into the oil circuit to ensure adequate oil viscosity.

Movement of the control handle imparted stroke to the pumps, the power being proportional to (a) the degree of movement applied, and (b) the pressure built up in the hydraulic system due to external resistance to turret movement.

The turret was rotated by a seven-cylinder elliptical cam-type unit, with a rotating cylinder block and a stationary distributor spindle. It was reversed by changing the direction of the delivered fluid. The hydraulic rotation motor turned the turret by means of a geared, toothed wheel acting on gears on the inside of the turret ring. The moving ring of the turret was supported on a double row of cageless ball bearings, and the lower row taking the structural loads and the upper row the radial stresses.

The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 29 Apr 2003 14:43

Hi

The Boulton Paul Aircraft Ltd

The Boulton Paul Electro-hydraulic Power System - Pt 2

The gun cradle was elevated by a ram acting upon it. This operated in conjunction with another ram which moved the gunner's seat so as to keep his eyes always in line with the gunsight - thus when the guns were raised the seat was lowered, and vice versa.

Each gun was fired by a separate solenoid, a single firing button being mounted on the top of the control column with a safety isolating switch on the gunner's control panel. An interrupter system was fitted to the rear defence and upper turret's firing circuits: as the guns were spaced apart, independent interruption was provided to give a maximum field of fire.

For this purpose Boulton Paul used a rotating-drum system. A small cylindrical drum was made to rotate at the same speed as the turret, with two spring-loaded sliding bushes located one above the other, the top bush controlling the right and the bottom the left-hand guns. Patterns were cut on the drum corresponding to where the airframe obstructed the guns. These were filled with insulating material which broke the circuit when it came into contact with the bushes.

Nose and mid-upper turrets were fed by belt boxes under the guns. No booster units were needed, the normal gun feed receivers being able to lift the belts with out assistance. As mentioned in the description of the Type E turret, tail turrets needed more ammunition, and the boxes were
stored between the wing and tail where the trim of the aircraft was less affected. Boulton Paul feed assisters were fitted inside the turret, through which the long belts were taken. This unit was complex but rarely gave trouble. The belts were taken over toothed sprockets which were normally free, but when tension in the belt exceeded a certain pressure, a hinged arm moved over and engaged a band brake to the gear, which applied power to the sprockets, pulling the belt into the gun receiver.

A means of operating the turret movements at high speed was provided. When the high-speed button was pressed on the gunner's control panel, a resistance was switched in to the field windings of the drive motor giving increased speed of operation. This could only be used for short spells as it placed an overload on the motor. When the high-speed facility was in operation a red warning light was switched on.

The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 30 Apr 2003 10:26

Hi

The Bristol Aircraft Company Ltd

The Bristol Type B.I Series

This turret, designated the Bristol Type B.I Mk.I, was the first of a series of Bristol-designed hydraulically powered turrets which were to be associated mainly with the Blenheim and Beaufort. The control system was to remain basically the same throughout the whole range of sub-types, the main difference being the type and number of guns fitted. The company rightly claimed that the Blenheim turret was a big step forward in bomber defence, giving the gunner powered gun control from a compact enclosed cupola.

The B.I turret was powered from a three-stage gear-type hydraulic pump mounted on the port engine, which delivered 11.4 litres (2 1/2 Imp galls) of oil per min at a pressure of 49.3kg/sq cm (700 lb/sq in). As the pump also supplied pressure to the flaps and undercarriage, a selector valve in the cockpit directed oil to either turret or the main hydraulic services.

The hydraulic reservoir was fixed to the bulkhead of the port engine, and contained 4.6 litres (one Imp gal) of oil and space for a further 4.6 litres (one Imp gal) to allow for agitation and foaming. The early reservoirs lost oil during violent manouevres, sometimes with disastrous results.

When the turret was not in use the cupola could be partially retracted to reduce drag by turning a small handle on the right-hand cupola support tube. The handle turned a pinion which acted on a toothed rack inside the tube, lowering the dome until a spring-loaded pawl engaged. The cupola was automatically extended when a release lever was operated, releasing the pawl. Springs inside the support tubes raised the dome to the limits.

The turret was controlled in elevation and rotation by means of a tee-shaped control column, the gunner holding handles on either side of the upright. A squeeze lever on the left handle operated the main hydraulic valve supplying pressure to the system. On the right handle was the gun firing trigger, linked to the gun by a Bowden cable. In later versions the trigger operated solenoid units attached to the guns.

The turret was rotated by a bicycle-type steering movement - turned to the left it rotated to the left, and vice versa. This was achieved by hydraulic valves actuating a double-acting ram, anchored to a floor-mounted pin, turning the turret by means of an elbow joint.

A feature unique to the B.I turret was the ability to turn the guns independently of the main rotation system. A ram controlled by foot pedals turned the gun cradle, enabling the gunner to fire at a target approaching from dead astern, where an attacking fighter could not usually be engaged from a mid-upper turret.

The guns were elevated and depressed by a twisting movement of the handles, the gunner's seat being linked with the gun elevation system. A hydraulic ram operated the seat, which was linked by an arm to the gun cradle. When the gunner twisted the handles towards him the ram extended. lowering the seat and elevating the gun cradle; when twisted in the opposite direction the guns were depressed and the seat raised. This system ensured that the gunner's eyes were always in line with the gunsight.

The gunner entered the turret through a hatch forward of the turret. He stowed his parachute on a rack, then stooped down under a bulkhead and up into the turret (the restricted access to the B.I was a cause of concern -releasing injured gunners was very difficult). He then stepped into his seat and fastened a lap strap. On the starboard side of the fuselage within his reach were the various services, the layout of which can be seen from the illustration. He plugged in the oxygen connector and intercom jack and switched on the reflector sight (the early models were sighted by a ring and bead or a G1 prismatic sight). The turret could not be operated until the aircraft was airborne and the pilot had switched over the hydraulic supply. In common with all turrets the Perspex panels were prone to condensation and icing up, a problem which was overcome by the provision of two movable segments to the gunner's front. These could be slid aside to give a clear field of view.

The airframe was protected from damage by two separate systems, a lever under the gun cradle which cut off the depresssion valve before the gun barrels hit the airframe, and a micro switch actuated by a cam on the main gun pillar which cut off the gun firing system when the guns approached the danger zone.

When war was declared in 1939 the Blenheim was the only effective light bomber in Squadron service with the RAF, and it was later used on every war front. When it had entered service in March 1937 it outperformed every fighter in Service, but by 1939 it proved no match for the German fighters over France. After the fall of France Blenheims were sent on low level sorties against targets in occupied Europe, and losses were high. Gunners complained of the lack of armour protection and the poor firepower of the single gun, so as a stopgap measure an armoured shield was fitted in the rear fuselage behind the turret, and the drum-fed Lewis and Vickers K guns were changed to belt-fed Browning guns. The Mk.IV version of the turret was then introduced, armed with two Browning Mk.II guns which gave much-improved firepower, but the basic design was by then outdated, and in response to adverse comments from Squadron gunnery officers, the company designed a completely new turret for the Blenheim, the Mk.X.

Details of the Bristol Type B.I Series Turrets

Position: Mid-upper
Power system: Bristol hydraulic, from three-stage pump on port engine
Diameter of of turret ring: 762 mm (30 in)
Armament:
Type B.I Mk.I: 1 x 7.7 mm (0.303 in) Lewis Mk.III gun
Type B.I Mk.IE: 1 x 7.7 mm (0.303 in) Vickers K gun
Type B.I Mk.II: 1 x 7.7 mm (0.303 in) Vickers K gun
Type B.I Mk.III: 1 X 7.7 mm (0.303 in) Vickers K gun
Type B.I Mk.IIIA: 2 x 7.7 mm (0.303 in) Vickers K gun
Type B.I Mk.IV: 2 x 7.7 mm (0.303 in) Browning Mk.II gun
Type B.I Mk.V: 2 x 7.7 mm (0.303 in) Browning Mk.II gun
Type B.I Mk.VI: 2 x 7.7 mm (0.303 in) Browning Mk.II gun
Ammunition: 400 rounds per gun
Firing mechanism:
Type B.I Mk.I: Bowden cable manual
Other Marks: Electrical solenoid sear releases via microswitch and gunfire interrupter
Field of fire:
Traverse: 60 degrees either side of aft
Elevation: 60 degrees above horiziontal
Depression: 32 degrees below horizontal
Armour protection: 9 mm (0.354 in) face shield; 9 mm (0.354 in) apron to gunner's front (varied with unit)
Operating speeds:
Rotation: 50 degrees/sec
Gun rotation: 40 degrees/sec
Elevation/Depression: 45 degrees/sec
Weight: 177 kg (390 lb)
Gunsighting:
Type B.I Mk.I: Ring and bead or GI prismatic
Type B.I Mk.IE: Mk III reflector sight; subsequent Mk.IIIA reflector sight

The following aircraft were fitted with the Bristol Type B.I Series Turrets.

Aircraft type: Bristol Blenheim Mk.I
Type & Mark: B.I Mk.I
Position: Mid-upper
Guns: 1 x 7.7 mm (0.303 in) Lewis Mk.III
Traverse: 120 degrees
Elevation: 60 degrees
Depression: 32 degrees
Remarks: Partial rotation

Aircraft type: Bristol Blenheim Mk.IV
Type & Mark: Type B.I Mk.IE
Position: Mid-upper
Guns: 1 x 7.7 mm (0.303 in) Vickers K
Traverse: 120 degrees
Elevation: 60 degrees
Depression: 32 degress
Remarks: Modified hydraulics

Aircraft type: Bristol Blenheim Mk.IV
Type & Mark: Type B.I Mk.II
Position: Mid-upper
Guns: 1 x 7.7 mm (0.303 in) Vickers K
Traverse: 120 degrees
Elevation: 60 degrees
Depression: 32 degrees
Remarks:

Aircraft type: Bristol Blenheim Mk.IV
Type & Mark: Type B.I Mk.III
Position: Mid-upper
Guns: 1 x 7.7 mm (0.303 in) Vickers K
Traverse: 120 degrees
Elevation: 60 degrees
Depression: 32 degrees
Remarks:

Aircraft type: Bristol Blenheim Mk.IV
Type & Mark: Type B.1 Mk.IIIA
Position: Mid-upper
Guns: 2 x 7.7 mm ().303 in) Vickers K
Traverse: 120 degrees
Elevation: 60 degrees
Depression: 32 degrees
Remarks:

Aircraft type: Bristol Blenheim Mk.IV
Type & Mark: Type B.I Mk.IV
Position: Mid-upper
Guns: 2 x 7.7 mm (0.303 in) Browning Mk.II
Traverse: 120 degrees
Elevation: 60 degrees
Depression: 32 degrees
Remarks:

Aircraft type: Bristol Beaufort Mk.I
Type & mark: Type B.I Mk.V
Position: Mid-upper
Guns: 2 x 7.7 mm (0.303 in) Browning Mk.II
Traverse: 120 degrees
Elevation: 60 degrees
Depression: 32 degrees
Remarks:

Aircraft type: Avro Anson & Fairey Battle
Type & Mark: Type B.I Mk.VI
Position: Mid-upper
Guns: 2 x 7.7 mm (0.303 in) Browning Mk.II
Traverse: 120 degrees
Elevation: 60 degrees
Depression: 32 degrees
Remarks: Gunnery training

The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 30 Apr 2003 14:12

Hi

The Bristol Aircraft Company Ltd

The Bristol Type B.II and B.III Powered Turrets

With the success of the powered pillar design, it was decided to adopt the same principle to power a new enclosed turret system for the Bristol Bombay. The resulting designs were the Bristol turret types B.II (nose) and B.III (tail). The basic details were as follows:

A Vickers K gas-operated gun was mounted on its side, and the barrel fixed through a gimbal-type mounting in a radial slot running horizontally across the front of the turret. The breech end of the gun was fixed to a quadrant-shaped arm which moved vertically in a semi-circular guide. A hydraulic ram powered this movement, and a series of moving arms linked this movement with the gunsight. Another ram mounted on the turret floor rotated the enclosure horizontally. To seal the mechansism from the outside slipstream a strip of thin steel moved in a slot and rotated with the mounting.

Firing tests revealed that fumes from the gun were troublesome, and to overcome this problem a fume extractor system was devised which vented to the outside air. The B.III tail turret was not a great success owing to excess vibration and movement at the end of the fuselage. in addition, quick-release clips had to be provided to jettison the tail cupola after an unfortunate gunner was trapped in a landing accident. The B.II nose turret incorporated the bomb sight, and a separate seat was provided for bomb aiming, giving a view downwards through a flat glass panel.

The following aircraft were fitted with the Bristol Type B.II and B.III Turrets

Aircraft type: Bristol Bombay
Type & Mark: Type B.II
Position: Nose
Gun: 1 x 7.7 mm (0.303 in) Vickers K
Traverse:
Elevation:
Depression:
Remark:

Aircraft type: Bristol Bombay
Type & Mark: Type B.III
Position: Tail
Gun: 1 x 7.7 mm (0.303 in) Vickers K
Traverse:
Elevation:
Depression:
Remarks: Severe vibration

The above text and top photo were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

The middle photo was taken from "The Hamlyn Guide to British Aircraft of World War II", by David Money.

The bottom photo was taken from "Armament of British Aircraft 1909-1939", by H F King.

Regards

Bob
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Postby Robert Hurst » 30 Apr 2003 14:44

Hi

The Bristol Aeroplane Company Ltd

The Bristol Type B.IV Mk.I Turret - Pt 1

After a prolonged development period the Bristol Beaufort entered service in April 1940. Designed for a four-man crew, the Beaufort was earmarked for maritime strike and reconnaissance work.

Although similar to its stable mate the Blenheim, the crew compartment was larger, being carried through to the mid-upper turret. This was a special design tailored to fit the airframe, designated the Type B.IV and armed with a single Vickers K gas-operated gun. The designers were required to keep the weight of the turret as low as possible and, to this end, a new rotation system was devised: this consisted of a pulley-like drum at the base of the turret, which was turned by cables drawn back and forwards by a ram. As the extended fuselage protected the turret from the slipstream, the cupola was made less rigid than the Type B.I.and these and other features kept the weight down to a reasonable 66 kg (146 lb). The gun was fired by a trigger, from which a Bowden cable operated a switch controlling a solenoid gun-firing unit: this and the other controls were identical to the Type B.I system. As with the B.I, gunners complained of the lack of firepower, and the Mk.IVE was introduced in which the gun cradle was modified to take two Vickers K guns. The gun-sighting was by a Mk.III, or Mk.IIIA, free gun reflector sight, this being fixed directly on the gun body by an angled bracket.

The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Guns and Turrets", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 01 May 2003 11:10

Hi

The Bristol Aeroplane Company Ltd

The Bristol Type B.IV Mk.I Turret - Pt 2

The Mk.I was fitted with a cheek pad to steady the gunner's aim, but this was dispensed with on the twin-gun Mk.IE. Spare magazines were stored on pegs fixed to the starboard fuselage walls, within reach of the gunner. The usual oxygen, interphone and heating sockets were fitted to the port side walls close to the rack for the gunner's parachute.

After adverse reports from gunnery officers attempts were made to convert the turrets to Brownings, but this was found to be impossible, and the turrets were replaced with a special version of the Type B.I, designated Type B.I Mk.V. Although this gave sustained firepower, these aircraft were still vulnerable to attacks from German fighters, which were armed with heavy calibre cannon. Astute use of cloud cover and vbery low operating heights proved the best defence.

The Beaufort Under-defence Mounting.

Some Beauforts were fitted with a manually controlled rearward-firing Browning gun, enclosed in a Perspex moulded fairing, to cover the blind zone under the tail. The gun was operated by the bomb aimer by means of a handle fixed to the rear of the gun body. The gun was clamped into a mounting which gave limited movement in elevation and traverse, being aimed by means of a mirror which was aligned on a ring-and-bead sight. The gun was fed by a 200-round box, the belt being routed into the receiver via a swan-neck duct. Empty cases and links were ejected into the slipstream through an aperture in the bottom of the moulding. The mounting was very rarely used, as most operations took place at low level and it was found to be very difficult to locate an attacking fighter in the mirror.

Australian Beauforts

Some Australian-built Beaufort Mk.VIIIs were fitted with Type B.V Mk.I turrets fitted with twin 12.7 mm (0.5 in) Browning guns.

Details of the Bristol B.IV Mks. I and IE Turrets

Position: Mid-upper
Diameter of ring: 101.6 cm (40 in)
Weight of turret Without cupola: 46 kg (102 lb)
Weight of turret with cupola: 66 kg (146 lb)
Power source: Engine-driven gear type pump
Servo mechanism: Hydraulic
Fluid used: Oil lubricating anti-freeze Type A
Working pressure: 67 kg/sq cm (800 lb/ sq in)
Field of fire:
Traverse: 90 degrees either side of aft
Elevation: 60 degrees
Depression: 40 degrees
Armament:
Mk.I: Single 7.7 mm (0.303 in) Vickers K gun
Mk.IE: Twin 7.7 mm (0.303 in) Vickers K guns
later fitted with B.I Mk.V: Twin 7.7 mm (0.303 in) Browning Mk.II guns
Armour: Empty cartridge box fitted with armoured panels
Fire control mechanism: Trigger-operated Bowden cable, or trigger-operated electro-hydraulic firing and interrupter gear
Gunsight: Mk.IIIA free reflector sight.

The following aircraft were fitted with Bristol B.IV Mks.I and IE Turrets

Aircraft Type: Bristol Beaufort G R Mk.I
Type & Mark: B.IV Mk.I
Position: Mid-upper
Guns: 1 x 7.7 mm (0.303 in) Vickers K
Traverse: 180 degrees
Elevation: 60 degrees
Depression: 40 degrees
Remarks:

Aircraft Type: Bristol Beaufort G R Mks I & II
Type & Mark: B.IV Mk.IE
Position: Mid-upper
Guns: 2 x 7.7 mm (0.303 in) Viclers K
Traverse: 180 degrees
Elevation: 60 degrees
Depression: 40 degrees
Remarks:

Aircraft type: DAP-built Beaufort Mk.VIII
Type & Mark: B.V Mk.IE
Position: Mid-upper
Guns: 2 x 12.7 mm (0.5 in) Browning Mk.II
Traverse: 180 degrees
Elevation: 60 degrees
Depression: 40 degrees
Remarks: Australian made.

The above text and top two photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

The bottom photo was taken from "Warplanes of the Second World War Vol.7: Bombers and Reconnaissance Aircraft", by William Green.

Regards

Bob
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Postby Robert Hurst » 01 May 2003 11:49

Hi

The Bristol Aeroplane Company Ltd Power Operated Gun Turrets

The Bristol Types B.VI, B.VII, B.VIII & B.IX Mk.I Turrets

Looking for info.

Regards

Bob

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Postby Robert Hurst » 01 May 2003 11:57

Hi

The Bristol Aeroplane Company Ltd

The Bristol Type X Mk.I Turret

The Bristol Type X was designed to replace the earlier Mk.I series of Blenheim turrets. The earlier B.I actuating system with its maze of pipes and leakable glands and rams was abandoned and replaced by hydraulic motors. Two guns were mounted one to each side of the gunner, giving a much improved field of view. No attempt was made to retain a clean fuselage outline, a large cut-out being left out behind the turret to give a better field of fire to the low rear sector.

The twin Brownings were fed from side-mounted ammunition boxes, from where the belts were channelled up over feed rollers into the gun feedway. Spent links and cases were taken away by means of an ingenious circular receiver and ejected into long chutes which dumped them overboard. A long-standing complaint regarding the B.I was the difficulty of escape for the gunner. The Type X featured a large jettisonable panel in the roof of the cupola, which was meant for use in forced landings, or accidents on take-off and landing. There was little chance of bailing out on Blenheim sorties, which were invariably carried out at low level. The guns were linked by a rigid torsion tube, which gave the gun mountings strength and linked the elevation movement.

At the request of gunnery officers, hoisting brackets were fitted to the gun ring housing, enabling armourers to lift the whole turret clear for maintenance and replacement. As can be seen from the illustrations, all services were provided, including no fewer than three floodlights. A new control column was used, still of a 'handlebar' configuration, with master valve control levers on each handle. The guns were fired by means of solenoid units, controlled by a push-button unit mounted on the right control handle.

The gun interrupter system was a cam-following unit, which protected the airframe from gunfire and mechanical damage from the gun barrels. Two detachable panels in the cupola sides gave access to the guns for replacement and servicing. A Mk.IIIA reflector sight was mounted just behind the torsion bar, with the sight switch and spare bulbs on a small panel to the gunner's left. The Type X was a well-designed turret, which was used as a basis for the new types on the drawing boards of the Bristol design office. Accessibility for servicing was appreciated by the armourers and gunners of the strike squadrons, but the Air Staff realised only too well that the Blenheim was proving no match for the Messerschmitts and Focke-Wulf fighters over occupied Europe. It was also vulnerable to the multi-cannoned anti-aircraft mountings placed around targets.

When new types became available the Blenheim was transferred to North Africa where, even with its new turret, it proved easy meat for the agile German interceptors. By 1943 almost all were moving to India.

Details of the Bristol Type B.X Mk.I Turret

Position: Mid-upper
Motive power: Bristol hydraulic motor system
Armament: Two 7.7 mm (0.303 in) Browning Mk.II guns
Firing mechanism: Solenoid release units
Gunsight: Mk.IIIA reflector sight and Mk.I gyro sight
Armour: Full protection to gunner's front
Turret speeds:
Traverse: 60 degrees per sec
Elevation: 50 degrees per sec
Field of fire:
Rotation: 60 degrees either side of aft
Elevation: 70 degrees above horizontal
Depression: 20 degrees below horizontal

The following aircraft was fitted with the Bristol B.X Turret

Aircraft type: Bristol Blenheim B.Mk.V
Type & Mark: B.X Mk.I
Position: Mid-upper
Guns: 2 x 7.7 mm (0.303 in) Browning Mk.II
Traverse: 120 degrees
Elevation: 70 degrees
Depression: 20 degrees
Remarks: Extensive armour

The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob.
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Postby Robert Hurst » 02 May 2003 14:07

Hi

The Bristol Aeroplane Company Ltd

The Bristol Type B.11 Mk.I* - Pt 1

This four-gun model of late 1940 was a masterpiece in turret design. To contain four Browning guns, a full control panel, and gunner's controls in a 762 mm (30 in) diameter enclosure was a remarkable feat. The relative lack of bits and pieces and the clean design of the ammuniton feeds were a credit to the design team, the only fault being a rather restricted field of view downwards. The turret was designed especially for a new Blenheim replacement, the Beaumont, or 'Beau Bomber', but the Air Staff decided not to adopt the new aircraft. The Type 11 was considered for the Douglas Boston and de Havilland Mosquito, but these and other schemes were never adopted, and the turret was not used operationally. The Type 11 used a hydraulic ram for elevation and depression of the gun cradle, the seat moving up and down with the guns. A hydraulic motor was used for rotation similar to the Type X, turning a pinion which engaged in a geared track at the base of the turret. The cupola was very roomy, giving ample room for observation and turret control. A detachable panel could be jettisoned by the gunner for escape.

The arcuated ammunition boxes were formed into a single unit, and could be encased in an armoured apron. provisoion was made for manual rotation by means of a small handle to the gunner's left front. The normal Type B.I control column was used, with all fuses and control switches mounted on apanel just above the handles. The heated clothing and interphone jacks were fitted on flexible cables hanging from the centre of the control panel.

*Note: After the Type X turret, the company dropped the use of Roman Numerals in favour of the normal Arabic ones.

The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob
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Postby Robert Hurst » 02 May 2003 14:54

Hi

The Bristol Aeroplane Company Ltd

The Bristol Type B.11 Mk.I Turret - Pt 2

The four Browning Mk.II guns were fed from the belt boxes up swan-necked chutes into the receivers on the outside of the guns, which were staggered in a very compact mounting fitted to the top of the operating mechanism. During firing trials the staff remarked on the tremendous noise when the four guns were fired, and it was also found that some creep was experienced when firing to the beam. The Mk.IIIA reflector sight was fitted at an angle of 45 degrees on the top of the guns, two cheek pads helping to steady the aim. Three spare bulbs were provided for the sight in holders on the gun ring to the gunner's left. The elevation system was rather shallow in depression, owing to the height needed for the guns and sight, but the guns could be elevated to a remarkable 80 degrees. At an operational weight of 186 kg (410 lb) fully armed there was quite a weight penalty, but the close cone of fire would have been lethal to any aircraft hit by a burst from the four guns.

Details of the Bristol Type B.11 Mk.I & IA Turret

Position: Mid-upper
Motive power: Hydraulic, motor rotation double-acting ram elevation
Armament: Four 7.7 mm (0.303 in) Browning Mk.II guns
Ammuntion: 400 rounds per gun
Field of fire:
Traverse: 360 degrees
Elevation: 80 degrees above the horizontal
Depression: 28 degrees below the horizontal
Gun sight: Mk.IIIA reflecftor sight
Armour: 7 mm (0.276 in) armoured apron front of ammunition boxes and front of control panel
Weight (armed): 186 kg (410 lb)

The following aircraft were fitted with the Bristol Type B.11 Mk.I Turret

Aircraft type: Not allocated (Bristol Beaumont)
Type & Mark: B.11 Mk.I
Position: Mid-upper
Guns: 4 x 7.7 mm Browning Mk.II
Traverse: 360 degrees
Elevation: 80 degrees
Depression: 28 degrees
Remarks:

Aircraft type: De Havilland Mosquito II prototype
Type & Mark: B.11 Mk.IA
Position: Mid-upper
Guns: 4 x 7.7 mm (0.303 in) Browning Mk.II
Traverse: 360 degrees
Elevation: 80 degrees
Depression: 28 degrees
Remarks: Prototype only.

The above text and top photo was taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

The bottom photo was taken from "Warplanes of the Second World War", by William Green.

Regards

Bob
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Postby Robert Hurst » 02 May 2003 15:32

Hi

Bristol Aeroplane Company Ltd

The Bristol Type B.12 Mks 1, 2 and 4 Turrets - Pt 1

The Bristol Type B.12 Mk.1, was designed for the Bristol Buckingham. It was armed with four guns mounted in pairs on either side of the seated gunner. The power system was similar to that of the Type 11, a reversible hydraulic motor for rotation and a double-acting ram for elevation. A third ram elevated the gunner's seat, being connected hydraulically tot he elevation ram so that when the guns were elevated the seat lowered and vice versa.

The specification called for the controls to be so designed that the crew could pass through the unoccupied turret to the bomb-aiming position under the aircraft. Ammunition was stored in arcuic boxes either side of the gunner to give access through the turret. The hydraulic rotation motor was mounted on a frame in line with the turret ring, and the elevation ram was fitted to the port side. The gunner controlled the turret with two side-mounted pistol-grip handles. A twisting movement turned the turret by means of link rods to the rotation valve, and by lifting or depressing the handles the gun cradles were elevated or depressed. On the handles were triggers which operated gun-firing solenoids on the two guns on the side of the handles. In the event of an electrical failure the guns could be fired by a foot pedal linked mechanically with all four gun-firing levers. The firing circuits were taken through an interrupter drum to relays, which energised the gun firing solenoids.

One of the three prototypes was fitted to a Halifax and air tested at Boscombe Down. As can be seen, the turret presented a low drag factor, having a similar profile to the American Martin and Bendix designs.



The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob
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