Early RAF Gun Turrets

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Robert Hurst
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Early RAF Gun Turrets

#1

Post by Robert Hurst » 04 Apr 2003, 14:34

Hi

The Westland Pterodactyl Turret

Given the fact that hostile aircraft usually attacked from the rear, where the tailpane usually impeded the field of defensive fire, Westland designed a two-seat fighter with a maximum field of fire against an attack form the rear. This was the tailless Pterodactyl Mk.V of 1932.

Painted to resemble its prehistoric namesake, the single-seat prototype of an earlier Pterodactyl was flown at air shows, providing light entertainment for the crowds, but the Mk.V two-seat fighter was a studied attempt to revolutionise the accepted concept of fighter design. Designed with the assistance of Professor G.T.R. Hill, the new fighter was to be armed with two Lewis guns which could cover the whole rear hemisphere, the pilot being provided with a fixed, forward-firing Vickers gun. The turret was mounted directly behind the pilot, supported by ball-bearings running in a ring fixed to the aircraft structure.

The turret was powered by a 24 volt electric motor fed from a generator driven by the engine or a windmill-type generator with a battery back-up unit. When the turret was being used the motor ran continuously, power being taken off when required from a gearbox containing two infinitely variable disc and roller friction-type take-offs.

From the gearbox, shafts carrying worm gears engaged in teeth on the outer rim of a circular frame to which the guns were fitted. The turret was rotated in azimuth by a pinion meshing into internal teeth cut into the fixed ring. The gunner controlled the speed and direction of turret rotation via a handle which applied power from the gearbox by way of bellows chambers and hydraulic tubes. The motor stored sufficient kinetic energy for any sudden acceleration, and eliminated the initial sluggishness of a directly coupled motor. Motion of the handle forwards or backwards elevated the guns and sight arm, and a sideways movement rotated the turret in the same direction. Spare drums for the Lewis guns were contained in a U-shaped dispenser - when an empty drum was placed into one side of the container, a full drum was automatically unlocked from the other side ready for use.

Unfortunately the Pterodactyl fighter turret did not get beyond the experimental stage, and there are no records of it being air-tested. One reason was probably the variable disc and roller transmission system which, although it was thought to be an ideal method of transmission, was rejected by both Bristol and Boulton Paul after early experiments with turret drives.

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

Regards

Bob
Attachments
Test rig.jpg
Test rig.jpg (26.11 KiB) Viewed 5162 times
Pterodactyl turret 1932.jpg
Pterodactyl turret 1932.jpg (46.67 KiB) Viewed 5166 times

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#2

Post by Robert Hurst » 04 Apr 2003, 15:20

Hi

The Heyford Dustbin

The Handley Page Heyford, designed in 1927, was fitted with a retractable under defence turret, known for obvious reasons as the Dustbin. Armed with a Lewis gun on a flexible mounting, it was wound down into position under the big biplane bomber. The gunner then lowered himself on to a small seat. The gun was fitted to a tubular arm low to his front. He could rotate the enclosure round to each beam, giving him a reasonable field of fire to counter an attack from below, and spare ammunition drums were stowed in the fuselage within reach. Gunners reported that the position was very cramped, and when facing aft there was a blustering draught. When turned to the beam position slipstream interference was negligible.

The Barnes Wallis Windmill

The Aircraft Division of Vickers-Armstrongs submitted a design in 1934 for a biplane light bomber. This aircraft the Vickers G.4/31, was chosen from eight competing designs, but was later rejected in favour of the Wellesley monoplane bomber made by the same company. The G.4/31 featured a primitive powered turret in the rear cockpit, driven by a slipstream-operated power unit.

The mounting concisted of an L-shaped body fixed at the base to a rotatable ring. The windvane motor turned a flywheel which powered a flexible drive through a friction clutch. The gunner selected the speed and driection of rotation by means of a finger dialling mechanism. The dial operated a differential gearbox which drove a pinion meshed with the rotating ring of the turret. If the dial was turned to the left on the first hole, the turret would revolve slowly anti-clockwise, dialling fully to the right rotated the turet quickly to the right. There was provison for oxygen supply, gun and clothing heating and an intercom jack plug, the electrical services being fed through brush gear from the fixed ring. The single Lewis gun was fitted to an arm at the top of the main turret frame, being manipulated in elevation by hand. Wallis devoted much time and attention to the design, which was said to work quite successfully.

As with the Westland turret, the Vickers design was not accepted for Service use, but was significant as being another step in power assisted aircraft manipulation.

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

Regards

Bob
Attachments
Barne Wallis' wind powered gun mounting.jpg
Barne Wallis' wind powered gun mounting.jpg (24.37 KiB) Viewed 5155 times
Heyford with under-turret extended.jpg
Heyford with under-turret extended.jpg (32.8 KiB) Viewed 5158 times
The 'Dustbin' under turret.jpg
The 'Dustbin' under turret.jpg (33.37 KiB) Viewed 5159 times


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#3

Post by Robert Hurst » 05 Apr 2003, 10:41

Hi

The Armstrong Whitworth Turret - Pt 1

In the early 1930s, the Sir W.G. Whitworth Aircraft Company was among the leading producers of aircraft for the Royal Air Force. In 1932 the company was working on a design for a new monoplane bomber transport aircraft powered by two Armstrong Siddeley Tiger engines, the AW.23. When the defensive armament system was discussed, it was decided that the gunners would have to be protected from the slipstream. In common with most manufacturers at this time, it was realised that with increased operating speeds it was becoming difficult to control free mounted defensive guns in open cockpits. The Bristol Company had just produced a totally enclosed manually operated turret for their Type 120 biplane, but this was merely a glazed cupola fitted over a standard Scarff ring, and was never produced in quantity.

It was decided that a purpose-made turret would have to be designed for the AW.23, suitable for installation in the nose and tail positions of the new aircraft. A small turret development unit was formed, and in nine months a prototype was ready for ground firing tests. The tests revealed a faulty gun mounting bracket, but this was soon rectified and the turret was mounted in an Atlas biplane for air testing. Armed with a single Lewis gun, the turret was suspended on rollers in a vertical track, and was turned by the reaction of the gunner's feet on a ribbed rubber floor covering. The main feature of the new turret was the gun elevation control; this was an ingenious mechanism which balanced the weight of the seated gunner with his gun. There was also a following link system which ensured that the gunner,s eye was always in line with the gunsight throughout all angles of elevation. The designers also achieved a remarkable range of vertical movements - from an upward limit of 87 degrees the gunner could by standing and leaning forward over the front overhang, engage targets almost directly below him. The company claimed that merely by leaning forwards or backwards the gun could be depressed or elevated, and the whole mechanism gave accurate gun control during any evasion manoeuvres carried out by the pilot. Although the turret could be locked in any positoin of traverse or elevation, the gunner could fire whilst moving the turret without any problems of recoil or excessive vibration. When firing to the beam, the force of the slipstream on the barrel tended to rotate the cupola to the rear. To help overcome this, two balancing vanes were fixed to the top rear framing, but even then, firing to the beam required string hands and legs.

The 7.7 mm (0.303 in) Lewis Mk III gun was sighted by either a 114 mm (4.5 in) ring and bead sight, or a Norman Vane-type speed compensating sight. Five 97-round magazines were carried, spare magazines being clipped to the inside wall of the turret within easy reach of the seated gunner. The gunner entered the turret from the rear fuselage and stepped into a tip-up type seat. Later gunnery training models were fitted with bicycle-type seats made by Terrys Ltd, which, as some ex-gunners recall, were not the most comfortable mode of air travel. The dome shaped cupola consisted of a welded metal framework which housed panels made of Rhodoid acrylic plastic material.

The air firing tests were so promising that the company decided to take out a patent. This was dated November 1933, and details were then circulated to other manufacturers. A sister company, A.V. Roe Ltd, became interested in the turret and decided to use it to arm their new reconnaissance bomber, the Anson.

The Armstrong Whitworth AW.23 did not reach production, but the design was used for the famous Whitley, which was fitted with the turret in the nose and tail positions. Although the Whitley was eventually re-armed with Nash and Thompson power operated turrets, the AW turret saw limited service with Anson aircraft in the early war period. Its main use however was for gunnery training in Ansons and Airspeed Oxford aircraft.

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

Regards

Bob
Attachments
Whitley Mk 1 Tail Gun Turret.jpg
A drawing of the AW turret layout. The seat was balanced with the gun arm.
Whitley Mk 1 Tail Gun Turret.jpg (44.81 KiB) Viewed 5137 times
AW rear turret.jpg
AW rear turret.jpg (35.71 KiB) Viewed 5140 times
Avro Ansons armed with AW turrets.jpg
Avro Ansons armed with AW turrets.jpg (40.1 KiB) Viewed 5144 times

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#4

Post by Robert Hurst » 05 Apr 2003, 11:20

Hi

The Armstrong Whitworth Turret - Pt 2

When the first Ansons and Whitleys entered squadron service, air firing training commenced, with gunners firing at towed drogue targets. After the cold and draughty open gunner's cockpits, the turrets were very popular with the gunners and the usual cumbersome and heavy clothing was soon discarded: this fact alone contributed to a higher accuracy of gunnery. As the gunners mastered the new technique, accuracy improved even more, but reports of accidental damage to the host aircraft became more frequent than was usual when using the Scarff ring-mounted guns. Some Ansons were returning from air firing exercises with bullet-riddled tail surfaces and wings. An enquiry found that the traversing mechanism was so smooth that it was very easy to overrun when traversing on to a target, and also that when the gun was fired the vibration tended to turn the turret, with the help of the force of the slipstream on the barrel, towards the tailplane. With this in mind, gunners were instructed to avoid the tailplane area until guard rails could be installed. This edict applied only to training: in the event of of hostilities the tailplane would have had to take its chances, as it would be precisely this area where the enemy would be pressing home his attacks. The turret had an all-round traverse of 360 degrees when mounted on Anson and Oxford aircraft; on the Whitley installation the field of fire was limited by the fuselage to 85 degrees to each beam.

The de Havilland Don and AW.29 prototypes were also fitted with the turret, and the Royal Navy ordered a large number to arm motor torpedo boats and patrol craft, in which it was found to be an ideal weatherproof gun mounting and lookout position.

The Armstrong Whitworth turret was probably the most efficient hand-operated aircraft gun turret in service in the early 1930s, but several other companies were developing electrical, pneumatic and hydraulically powered designs which were to revolutionise bomber defence in the next decade.

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

The photos in this section were taken from "Armament of British Aircraft 1909-1939", by H F King.

Regards

Bob
Attachments
AW.23 fitted with AW turret.jpg
AW.23 fitted with AW turret.jpg (37.36 KiB) Viewed 5138 times
AW turret as applied to a singe & a twin engined bomber.jpg
AW turret as applied to a singe & a twin engined bomber.jpg (41.84 KiB) Viewed 5137 times
Airspeed Oxford I with AW turret.jpg
Airspeed Oxford I with AW turret.jpg (38.47 KiB) Viewed 5136 times

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#5

Post by Robert Hurst » 08 Apr 2003, 11:34

Hi

Early Boulton Paul Aircraft Gun Turrets - Pt 1

Boulton & Paul's first essay into unusual aircraft armament is linked with the company's design for a 'bomber destroyer', in the shape of the Boulton & Paul Bittern. This consisted of two Lewis guns mounted in trunnions, one either side of the front fuselage so that they could rotate in the vertical plane. They were remotely controlled by the pilot, who aimed the guns by a sight which was linked with the movement of the guns in elevation. The Bittern was not accepted for production, but the novel armament installation marked the beginning of the company's involvement in this importamt field of military aviation.

In 1927 the prototype of a new high-performance bomber, the Sidestrand, flew from the company's airfield at Mousehold near Norwich. This aircraft, which was contemporary with the Fairey Fox, had a speed and performance equal to any of the fighters in RAF service. The defensive armament consisted of the usual Lewis guns mounted on Scarff rings, fitted to open gunners' positions, and a Lewis in an under defence position. Successful trials were carried out leading to a production order for 20 aircraft, which were destined for No.101 Squadron based at Bircham Newton. The squadron air crews were delighted with their new equipment, and proceeded to show many intercepting fighters a clean pair of heels during mock interceptions. The only problem seemed to be with the air gunners, for with the higher operating speeds it was found to be more difficult to manipulate the Lewis guns in the stronger slipstream. The open cockpit of the nose position in particular was proving very uncomfortable in low temperatures, and changing ammunition drums with cold, heavily gloved hands was very difficult, some of the drums even being lost overboard, damagng propellers and aircraft structure.

After persistent reports of the poor marksmanship of Sidestrand gunners, the Air Staff accepted the fact that the problem lay in the increased speed of the new bombers. Consequently Boulton & Paul were awarded a development contract to provide some means of protection for the nose gunners. J D North had attended various armament courses during the war and was not inexperienced in the complexities of air firing, and he was ably assisted by H A Hughes, who took a leading part in the project. It was decided that the only practical solution would be a totally enclosed power-assisted turret. This was to be an historic decision, marking the company's entry into the field of specialised armament projects, in which it was to take a leading role in future years.

It was decided to provide a fully glazed, cylindrical turret with domed ends, which would fit into the nose of the aircraft. Various electrical and hydraulic power systems were tried, but the best power-to-weight performance seemed to be given by a pneumatic system. A reversible compressed-air motor was mounted behind the turret, rotating it by means of a geared drive in the bottom mounting. Side loads were taken by a circular rail amidships, supported by rollers in the fuselage.

The turret was armed with a single Lewis mounted on a pivoted arm. Control of the gun in elevation and depression was manual, but the gunner and gun mounting were supported by an ingenious hydraulic balancing mechanism. The gunner's seat was supported by a hydraulic ram, connected to a pair of smaller rams coupled to the gun arm. The rams were so designed that the gunner and mounting were balanced - if the gun was aimed upwards the rams lowered the seat, giving a comfortable sighting and firing position. When firing downwards the rams connected to the gun arm raised the gunner's seat to a position which enabled him to bring the guns to bear on the target. The gun barrel protruded through a vertical slot extending from top to bottom of the turret front, which was sealed from the slipstream by a zip-fastener mechanism fixed to rubber side facings.

The turret was traversed by the pneumatic motor, controlled by valves actuated by sideways pressure of the gun. Mounted on a pivot, the gun had limited sideways movement, and when moved to the limit the gun actuated a spring-loaded plunger, which operated a pneumatic valve which admitted compressed air to the motor. Further pressure on the gun handle opened the valve further, increasing the movement of the motor and the turret, while movement of the spade grip in the opposite direction opened another valve and rotated the turret in the reverse direction. The turret could be rotated a full 360 degrees in either direction if the gun barrel was sufficiently elevated to clear the fuselage. With the gun below this position traverse was limited by cut-out valves, which cut off pressure before the gun barrel reached the fuselage.

The compressed-air supply was stored in bottle to a pressure of 8.4 kg/sq cm (120 lb/sq in). As pressure was used the bottles were recharged by a compressor on the starboard engine. One of the problems faced by the designers was the need to provide a position for bomb aiming inside the turret. The front half of the turret was extensively glazed, one large section being made to open outwards and lock into a position where a bomb sight could be used. This was on the port side of the cupola, and when the bomb sight was used the turret was locked into a central fore and aft position.

After a series of tests at Boscombe Down the Air Ministry issued an order, to specification 29/33, for enough of the new turrets to equip two squadrons of Sidestrands, which were then to be known as Sidestrand Vs. Several other modifications were also called for: the undercarriage was stengthened, and the Bristol Jupiter engines were replaced with more powerful Bristol Pegasus IIM3s. After these modifications were carried out the name of the aircraft was changed to Overstrand. The first conversion was carried out on Sidestrand (J9186), which became the prototype Overstrand. On 22 February 1933 (J9186) was flown to Bircham Newton for service trials, during which various problems were found, and the aircraft was flown back to Norwich for modifications on 19 March.

On 30 June 1934 the underlying conflict between the flourishing woodworking department and the aircraft side of the business came to a head. After protracted and often acrimonious meetings it was decided to form two separate companies. The woodworking deparment would remain in the existing works, and the aircraft side was taken over by a newly formed company chaired by the Rt Hon Lord Gorell and Viscount Sandon. More significant was the appointment of the dynamic John North and S W Hiscocks as joint Managing Directors.

A new purpose-built factory was to be built at Wolverhampton, and in the meantime aircraft production continued in leased premises in Norwich. The new company was to be known as Boulton Paul Aircraft Ltd, a name which was to make an impact on the aviation industry. Problems with the Overstrand and its turret took longer to sort out than at first thought, but on 24 January 1935 Overstrand (J9185) landed at Bicester, where No.101 Squadron was then based. Overstrands gradually replaced Sidestrands and proved popular with the crews, squadron gunners in particular being full of praise for the comfort and ease of gun manipulation. Seated in a draught-free, heated enclosure with power assisted gun training, gunners acieved a hit rate of 55% against towed targets, compared with an average of 15% by gunners using Scarff rings in open cockpits.

The Overstrand turret received world-wide publicity, being hailed as a pointer to future bomber armament, which indeed it was. The Nash and Thompson hydraulic system was still in the development stage at this time. Various high-ranking officers from the RAF and foreign air forces visited No.101 Squadron at Bicester, many keen to try out the new turret mechanism. One distinguished officer insisted on installing himself inside the turret to test the controls. After closing the door he grasped the spade grip of the Lewis gun and pressed it to one side, and the turret immediately started to rotate at full speed. The unfortunate gentleman became disorientated, but onlookers could do nothing to help until the air pressure was exhausted, and the nauseated officer was then extricated. This incident was not so amusing to Boulton Paul as the highly colourful description related in the mess after the visitors had left. It highlighted the major drawback of the system, that every spell of sustained action had to be followed by a period of rest to allow the compressor to recharge the bottles - a situation unlikely to instil confidence in gunners likely to be under continuous attack. To sustain an adequate supply it was found that the compressor and air bottles would have to be too large to be practicable, and although the Overstrand continued to give good service it was decided to re-examine other means of powered gun control.

Meanwhile the transfer of plant and machinery to the Pendeford Lane works at Wolverhampton was completed in 1936 and the first aircraft produced in the factory began to emerge from the production bay. They were Haweker Demon two-seat fighters, in which ironically the company's competitors were to fit their new FN.1 powered gun turret. The aircraft were flown into the Parnall airfield at Yate. where the turrets were fitted into the specially prepared rear cockpits.

The above text and first two photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke. The bottom photo was taken from "Armament of British Aircraft 1909-1939", by H F King.

Regards

Bob
Attachments
Production Overstrand.jpg
Production Overstrand.jpg (48.75 KiB) Viewed 5124 times
BP Overstrand turret.jpg
BP Overstrand turret.jpg (24.54 KiB) Viewed 5123 times
Prototype Overstrand.jpg
Prototype Overstrand.jpg (35.89 KiB) Viewed 5124 times

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#6

Post by Robert Hurst » 08 Apr 2003, 15:11

Hi

Early Boulton Paul Aircraft Gun Turrets - Pt 2

The de Boysson Turret

In August 1935 John North was approached by a French company, the Societe d'Applications des Machines Motrices (SAMM), who informed him that they were developing a powered turret system to the design of a French engineer, J B A de Boysson, using hydraulic power from a turret-mounted compressor, with an integral electric-motor.

The Boulton Paul designers were already thinking along the lines of a self-contained hydraulic system, and North considered that the de Boysson design incorporated all the features required. As the French Armee de I'Air had shown no interest, and the aircraft industry in France was at this time committed to manually operated cupolas, Boulton Paul were able to negotiate an agreement to manufacture and develop the designs 'within the British Empire'. This agreement was signed in late 1935, with an option on two prototypes manufactured by the French firm, which were to be fitted with four of the new pattern 7.7 mm (0.303 in) Browning guns in place of the French 7.5 mm (0.295 in) Darne machine guns of the original design.

The armament section of the Aeroplane & Armament Experimental Establishment at Martlesham Heath was very impressed with the new turret, and a meeting took place between North, his test pilot, and representatives of the A&AEE to discuss the possibility of a two-seat fighter to replace the obsolescent Hawker Demon which was then (still quite new) in service. The de Boysson turret was to be the basis of the new design, for it was believed at that time that greater accuracy could be obtained from a multi-gun turret than from fixed guns aimed by the pilot (a theory which was later to be proved false).

Project 82

As a result of this meeting the Air Ministry issued a specification, F.9/35, for a day and night fighter armed with the new turret. Boulton Paul duly submitted a design embodying the turret which they called the P.82 project. The other contenders for the F.9/35 specification were Armstrong Whitworth, Bristol, Hawker and Supermarine. After evaluation of the various designs, two were selected as the most promising, these being the Boulton Paul project and the Hawker design, which was a development of the Henley called the Hotspur. However, by the time a decision had been made, the Hawker works at Kingston were fully extended with the development of their new Hurricane single-seat fighter, and they felt unable to proceed with another major project. This left the field open for Boulton Paul as the only contender, and in 1937 a production order was placed for 87 aircraft, now officially named Defiant. With the ominous developments in Europe, work on the aircraft and turret proceeded with great urgency, and under the dynamic leadership of North many new features were added to the original de Boysson turret design, among them the gunfire interrupter unit which automatically prevented any damage to the airframe.

The two French-built prototype turrets duly arrived, and one was fitted in the nose of Overstrand (K8175) for airborne trials. The other was despatched to Martlesham Heath for official firing trials, which North hoped would be of short duration as the turret was needed for important installation and engineering work at Wolverhampton, but unfortunately the trials were very lengthy, and it was only after protracted and at times acrimonious exchanges between John North and the A&AEE that the turret was returned and fitted to the second Defiant prototype, (K8620). This aircraft made its maiden flight on 18 May 1938, followed by the first production machine on 30 July. The first prototype (K8310), had made its inaugural flight on 11 August 1937, minus its turret, in the hands of Chief Test Pilot Flt Lt Cecil Feather at Pendeford Airport, Wolverhampton. Working drawings were completed, and the first production turrets were soon leaving the assembly shop for test firing in the Company stop butts, the name plates bearing the designation BP Type A Mk.1.

The Blackburn Roc

Meanwhile, after years of neglect the Fleet Air Arm found itself without a modern fighter, and thinking (erroneously) that the new Spitfires and Hurricanes would not be suitable or available for carrier work, it was decided to install a Defiant-type turret in the under-powered Skua dive bomber.

In spite of serious misgivings on the part of the design staff at Wolverhampton, the company manufactured 105 of these fighters, named the Blackburn Roc, and fitted them with the new turret. The Blackburn Company was unfortunate in their choice of design for the Air Services, for the Roc fighter was the result of a stopgap decision by the Admiralty and Air Staff in a desperate attempt to provide a modern fleet fighter, a bid for which the company could not be held responsible.

The Defiant

The development of the Defiant proved very long drawn out. It was not until 30 July 1939 that the first production machine made its maiden flight, the first production batch of 87 machines being delivered in early 1940 in time for the machines to take part in several spectacularly successful engagements against the Luftwaffe at the time of Dunkirk. German fighters, thinking they had bounced a bunch of sleeping Tommies from behind, ran into a hail of fire from the multiple Brownings in the turrets. However after this initial success the German pilots were quick to differentiate between the Hurricane and the turreted Defiants. It was soon realised that the two-seat single-engined fighter concept was badly flawed - it would have been useful as a bomber destroyer, but in daylight bombers were always accompanied by agile fixed-gun fighters which could easily out-manoeuvre the Defiants, attacking the many blind spots of the overloaded machines.

Although the Defiant did not live up to the high expectations of its designers, the Type A turret certainly did, and in 1937 the company was given a development contract to design a series of powered turrets armed with 7.7 mm (0.303 in) Browning guns to arm the new generation of heavy bombers then being developed by several manufacturers. The Air Staff had decided that Boulton Paul and Parnall were ideally placed to supply multi-gun powered turrets, which it was hoped would provide all-round protection for the new bomber designs.

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

Regards

Bob
Attachments
Boulton Paul Defiant.jpg
Boulton Paul Defiant.jpg (33.62 KiB) Viewed 5109 times
Blackburn Roc.jpg
Blackburn Roc.jpg (31.97 KiB) Viewed 5109 times
de Boysson turret.jpg
de Boysson turret.jpg (33.44 KiB) Viewed 5110 times

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#7

Post by Robert Hurst » 09 Apr 2003, 14:43

Hi

Early Boulton Paul Aircraft Gun Turrets - Pt 3

The G-Class Project

In early 1939 it was decided to use ex-Imperial Airways G class flying-boats for maritime patrol and reconnaissance. The most extensive modification was the provision of defensive armament. John North was summoned to Short Brothers at Rochester to advise on the installation of three Type A turrets on the big boats. It was decided to install two dorsal turrets and one at the extreme tail behind the rudder, but the first attempt to fit the tail turret was not a success, and major alterations were necessary before severe aerodynamic problems were ironed out. The aircraft in the photo is the Golden Fleece (X8274), being fitted out at Rochester in early 1940. Soon after his picture was taken the aircraft was handed over to No. 119 Squadron Coastal Command, where, having a longer range than the Sunderland it was used for anti-submarine patrols over the Atlantic and the Bay of Biscay, giving a good account of itself until it failed to return from an operation over the area in August 1941, when two engines failed simultaneously off Finisterre.

As well as Golden Fleece, two other G Class flying-boats were used by No. 119 Squadron, these were Golden Hind (X8275) and Golden Horn (X8273). No.119 Squadron was later disbanded in December 1941, and the remaining two aircraft were later handed over to BOAC.

Known as the S.26M in military form, the G Class flying-boat was fitted with three Boulton Paul Type A Mk.II turrets each housing four 7.7 mm (0.303 in) Browning guns. The forward turret was mounted between the wing spar frames slightly to starboard of the centre line of the aircraft; the centre turret was also mounted in the hull roof and was offset to starboard aft of the wing trailing edges, and the third turret was mounted in the extreme tail. Four 600-round ammunition boxes were fitted in each turret, and another four boxes were stowed in racks adjacent to each turret.

Also fitted with armament by Boulton Paul were two Short C Class flying-boats, designated S.23M in military form. The flying-boats concerned, Clio (AX659) and Cordelia (AX660) were fitted with the following defensive armament: One Boulton Paul Type A Mk.II dorsal turret mounted offset to starboard, and one Boulton paul Type A Mk.II rear turret mounted in the tail. Each turret housed four 7.7 mm (0.303 in) Browning Mk.II guns. One of the boats, Clio, was lost during military operations.

The Halifax Turrets

Following the success of the Type A design, it was decided to develop turrets suitable for the new heavy bomber projects of Avro, Short and Handley Page. Turrets were designed for the nose, tail and ventral positons of these aircraft using the electro-hydraulic system of the Type A. Prototypes of the new turrets were produced, and two types the C (nose) and E (four-gun tail) were demonstrated to representatives of Short Bros, A V Roe and Handley Page. After comparative testing Avro and Short decided to adopt the Parnall (Nash and Thompson) turrets for their aircraft, but Sir Frederick Handley Page was very impressed with the Boulton paul designs, and after a meeting with the Air Staff an official order was issued for nose and tail turrets to arm the HP 57 four-engined bomber, later named the Halifax.

On 17 July 1940 the two prototype Halifaxes, (L7244 and L7245), were tested at Farnborough with mock-up turrets in position. Soon after this the first production aircraft, (L9485), was air tested with the first Type C and E prototypes fitted. After some initial problems, when severe vibration and aerodynamic trouble was experienced with the Type C Mk 1, the turrets were accepted. (The Type R under defence turret was also tested, but was not used on production aircraft).

The above text and last two photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke. The first photo was taken from "Armament of British Aircraft 1909-1939", by H F King.

Armament details with regard to the Short C & G Class flying-boats was taken from "War Planes of The Second World War - Flying Boats", by William Geen.

Regards

Bob
Attachments
Handley Page Halifax.jpg
Handley Page Halifax.jpg (47.91 KiB) Viewed 5108 times
Short 'G' Class.jpg
Short 'G' Class.jpg (33.18 KiB) Viewed 5107 times
Boulton Paul Defiant.jpg
Boulton Paul Defiant.jpg (44.78 KiB) Viewed 5109 times
Last edited by Robert Hurst on 10 Apr 2003, 10:12, edited 1 time in total.

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#8

Post by Robert Hurst » 09 Apr 2003, 15:07

Hi

Early Boulton Paul Aircraft Gun Turrets - Pt 4

Boulton Paul Cannon Turrets

Even before work on the Type A turret was completed, it was realised that with the increasing use of heavy-calibre guns in fighters of other air forces, consideration would have to be given to turrets armed with shell-firing cannon, which could match the range and hitting power of opposing interceptors. Plans were put in hand in 1938 when a 20 mm Oerlikon gun was mounted in the open cockpit of Overstrand (K8176). The gun was mounted on a pedestal arrangement on the lines of a de Boysson design. The Air Staff were fully aware of this need and issued a specification (39/36) for a cannon-armed turret. In response to this the company submitted a design to meet this requirement. However, as the only such gun likely to be available was the 20 mm Hispano, which was not yet in production in Britain, it was decided to concentrate on 7.7 mm (0.303 in) Browning turrets until the production of heavy-calibre guns was sorted out. The company kept its options open, however, and work continued on a multiple cannon turret to specification P.11/37 which, it was hoped, would be considered for the Avro 679, later to become the Manchester. When the defensive armament was finally chosen, however, A V Roe decided to opt for the Nash and Thompson turrets made by Parnall.

The cannon turrets which came nearest to fruition were those submitted to Handley Page and Short Brothers for the Halifax and Stirling, the BP Type O (ventral) and the Type H (mid-upper). Prototypes of these turrets were ordered in 1939 but not completed.

All work on cannon turrets was officially terminated in 1940 when the Air Staff, strongly advised by the overlord of aircraft production, Lord Beaverbrook, decreed that all turret design teams should concentrate on rifle-calibre gun installations. Although with hindsight this may seem a retrograde step, given that the new generation of bombers was desperately needed , and also that the very high rate of fire of the Browning guns made up for deficiencies in marksmanship, the decision was perhaps justified at the time.

Of all the cannon-armed turrets designed by the company only one was completed, a Type A Mk II turret in which a 20 mm Oerlikon was mounted. This turret was flown in the first Defiant prototype.

P.92

Before the decision to shelve all work on cannon turrets was made, and the high hopes of squadrons of Defiants decimating hostile bomber streams had been dashed, the company was asked to submit a design for a new bomber destroyer, called AM specification F.11/37. This was to be a large, multi-seat, heavy fighter armed with four 20 mm Hispano guns. The new aircraft, designated the BP P.92, was to be powered by two Rolls-Royce Vulture engines. The design work was completed on the aircraft and a half-scale model was flown to evaluate its performance. The project was doomed from the outset, the RR Vulture engines proving to be one of the few major miscalculations made by the famous engine manufacturers. The aircraft would have been even more vulnerable than the Defiant, and the 'no cannons' edict would have ended all production.

The P.92 turret was also meant to to be used on a projected new bomber, The B.1/39. This was to be armed with two of the multi-cannon installations, in the mid-upper and ventral positions. Special cannon-armed turrets were also designed to arm a projected new flying-boat, the AM specifcation R.3.38. These comprised a nose turret mounting a single Hispano, and a twin-gun tail design. The specification brought in proposed designs from Blackburn,Saro, Shorts and Vickers, but the Sunderlands were proving adeqaute, and it was not thought prudent to embark on a lengthy tooling-up programme at that stage.

The above text and photos were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke. The photo of the Short C Class flying-boat Clio (AX659) was taken from "War Planes of The Second World War Flying-Boats", by William Green.


Regards

Bob
Attachments
Boulton Paul P.92.jpg
Boulton Paul P.92.jpg (30.22 KiB) Viewed 5100 times
Converted Type A turret with 20 mm gun.jpg
Converted Type A turret with 20 mm gun.jpg (22.04 KiB) Viewed 5149 times
Short C Class flying-boat.jpg
Short C Class flying-boat.jpg (28.57 KiB) Viewed 5101 times

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#9

Post by Robert Hurst » 10 Apr 2003, 11:02

Hi

Early Bristol Aeroplane Company Turrets - Pt 1

The Bristol Type 120 Turret

The Bristol Aeroplane Company was responsible for the first fully enclosed free gun mounting to be designed for the Royal Air Force. It was fitted to the rear cockpit of the Bristol Type 120, which competed for the Air Ministry Specification G.4/31, to select a replacement for the Westland Wapiti and Fairey Gordon. The gunner's cockpit on this two-seat biplane was fitted with a Scarff ring mounted lower than normal, at the level of the top longeron. To this was fixed a dome-shaped cupola constructed of transparent panels in light framework. The segment of the cupola in front of the gunner was left open to give the Lewis gun full elevation, and to give the gunner a clear view. This elementary turret, known as the 'parrot cage', was traversed by hand, the enclosure moving with the rotating ring of the Scarff mounting.

Air trials revealed that the turret was quite successful, especially when standing to fire downwards, when the slipstream was most troublesome in an open cockpit.

Entry was through a small triangular door on the port side of the fuselage - a feature not conducive to a rapid exit with a parachute pack. Great care had to be taken to avoid hitting the tail, as the enclosure tended to creep to a rear-facing position. During air trials, the occupant had a remarkable escape when the whole cupola broke free of the turret ring. The gunner received a glancing blow but was not injured. On the way to obscurity the enclosure broke off part of the rudder.

Similar manual enclosures were also in widespread use with the French Armee de I'Air. Some of their bomber aircraft in service featured multiple hand-operated cupolas until 1940, even though higher operating speeds restricted accurate manipulation of the guns.

The Bristol Bombay

In 1932 the Bristol designers were working on a large twin-engined, high-wing bomber transport, the Type 130, later to become known as the Bombay. It was proposed to arm this aircraft with a new design of power-assisted enclosed turret in the nose and tail. The power source was to be an electrical system which featured a motor-driven disc, from which a variable speed and reversible friction drive conveyed motion to the guns, controlled by a small joystick. This sytem was found to be insufficiently smooth in operation however, and electrical systems were rejected until some years later when a solution to this problem was found. When the first Bombays entered service they were armed with Scarff ring cupolas similar to the Type 120 'parrot gages'.

In 1933 a compact twin-gun nose turret was designed, in which the gunner crouched and was rotated with his Lewis guns about an axis of 360 degrees. It was powered by compressed air in rotation, the gunner having a rather restricted control in azimuth. The gunner's position was very similar to the much later Sperry ball turrets of the Second World war. As the illustration shows, it would probably not have been over popular with air gunners.

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

Regards

Bob
Attachments
Experimental Bristol nose turret.jpg
Experimental Bristol nose turret.jpg (30.38 KiB) Viewed 5082 times
Bristol Type 120.jpg
The parrot gage in situ.
Bristol Type 120.jpg (36.37 KiB) Viewed 5085 times
Bristol 120 turret.jpg
Bristol 120 turret.jpg (31.94 KiB) Viewed 5086 times

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#10

Post by Robert Hurst » 11 Apr 2003, 14:32

Hi

Early Bristol Aeroplane Company Turrets - Pt 2

The Powered Pillar

The army co-operation aircraft entering service in 1934 carried an observer who was expected to perform many duties from his cockpit, so the free gun mounting had to cause the minimum obstruction. To fit this requirement Bristol designed a hydraulically operated powered pillar mounting. This gave adequate and sensitive control and was a great improvement over the earlier hand-operated and bulky Scarff ring mountings.

The Bristol Remote Turret

In 1936 Frise designed an advanced tail turret in which the gun cradles were mounted in a circular enclosed turntable mechanism remote from the gunner's enclosure. The gun cradles could be elevated and depressed by double-acting hydraulic jacks. Similar jacks rotated the turntable by a rack and pinion system. The gunner had an uninterrupted field of view from his position above the gun mounting, but his cupola did not revolve, making sighting to the beam difficult.

The reflector sight was mechanically connected to the gun movement by a system of following cranks and rods. Ammunition was stored at the side of the guns, each belt being fed into the receiver by a swan-necked duct. provision was made for 1,000 rounds 7.7 mm (0.303 in) per gun. The gunner's control handle operated hydraulic valves feeding the double-acting jacks: it was claimed that a system of spring return in the hydraulic system eliminated backlash problems. Owing to the complexity of the design, this project was abandoned.

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

Regards

Bob
Attachments
Experimental tail defence mounting.jpg
Experimental tail defence mounting.jpg (35.74 KiB) Viewed 5081 times
Hydrauliccaly powered Bristol pillar mounting.jpg
Hydrauliccaly powered Bristol pillar mounting.jpg (25.19 KiB) Viewed 5081 times
Last edited by Robert Hurst on 09 May 2003, 15:01, edited 1 time in total.

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#11

Post by Robert Hurst » 15 Apr 2003, 15:31

Hi

Handley Page Ltd Gun Turrets

Harrow Turrets

The turrets were two in number, though a third (dorsal) powered installation has been mistakenly recorded. Designed by Handley page themselves, the turrets (nose and tail), had Frazer-Nash power units, and housed in each were the guns - two Lewis (rear) and one Lewis (front), aimed by means of reflector sights. Vickers G O guns were later fitted. Into the nose turret was built a projecting section incorporating an optically flat panel for the bomb aimer.

The Harrow's nose and tail turrets were distinct in design, and were not strictly 'rotatable' as sometimes asserted. The turret proper was in fact fixed, and the rotatable portion was in the form of a belt set low in a shallow embrasure and carrying the gun(s), which were elevated about a trunnion axis and had a wide field of fire in elevation and azimuth. This installation was associated with the Mk III reflector sight, the gunner's seat and a support for his feet. One advantage claimed was easy aerodynamic sealing. The sight was connected with the gun(s) by a parallel-link motion.

The Harrow's dorsal gun position was more or less in line with the trailing edge of the high-set wing and originally had a dummy fairing. The operational installation was a single Lewis gun and a manually operated cupola resembling that of the Armstrong Whitworth turret. The makers remarked that as the tail turret did not project above the top line of the fuselage, the dorsal gunner could fire past the twin fins and rudders and reduce the blind area to the rear to almost nothing.

The above text and middle photo were taken from "Armament of British Aircraft 1909-1939", H F King. The three-view drawing was taken from "Aircraft of the Royal Air Force", by Owen Thetford. The top photo was taken from "RAF Bomber Command and its aircraft 1936-1940", by James Goulding & Philip Moyes.

Regards

Bob
Attachments
Handley Page Harrow II.jpg
Note single gun in dorsal turret and twin guns in tail turret.
Handley Page Harrow II.jpg (30.04 KiB) Viewed 5064 times
Harrow three-view drawing.jpg
Harrow three-view drawing.jpg (31.33 KiB) Viewed 5070 times
Handley Page Harrow turret.jpg
The Harrow turret, designed by Handley Page, but having Frazer-Nash power units.
Handley Page Harrow turret.jpg (46.25 KiB) Viewed 5072 times
Last edited by Robert Hurst on 16 Apr 2003, 15:12, edited 1 time in total.

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#12

Post by Robert Hurst » 16 Apr 2003, 11:48

Hi

Vickers-Arstrongs Ltd Gun Turrets - Pt 1

The Vickers-Armstrongd Type 271.

Designed by Barnes Wallis to Air Ministry specification B.2/32, the Vickers-Armstrongs Type 271, from which the production-type Wellington was to evolved was provided with the following defensive capabilities.

A rotating nose cupola, contoured to the fine fuselage lines, housed a single Lewis gun on a manually-operated mounting, and a similar Lewis gun mounting was housed in the extreme tail. The tail cupola formed part of the locally fattened rear fuselage. The peculiar shape of the rear fuselage was apparently determined by the theory that a lighter structure would result from streamlining the main fuselage down to the tail unit and then bulging out the gunner's compartment, rather than streamlining the fuselage contour down to the extreme end of the cupola in a smooth curve, with a consequent deeper rear fuselage. Another Lewis gun, also on a manully-operated mounting, was in a mid-upper position with a retractng glazed cover. The glazing of the pilot's compartment was mainly of flat panelling, which looked rather out of place on such a perfect fuselage form and which was severely criticised during test flying because of sunlight glare reflecting from the flat panels.

The top photo was taken from "RAF Bomber Command and its aircraft 1936-1940", by James Goulding & Philip Moyes. The middle and bottom photos were taken from "British Aircraft Armament 1909-1939", by H F King.

Regards

Bob
Attachments
Vickers rotatable cupola.jpg
Vickers rotatable cupola.jpg (29.75 KiB) Viewed 5059 times
Vickers-Armstrongs Type 271 b.jpg
The B.9/32 with the curious enclosure known to the company as a 'windscreen'.
Vickers-Armstrongs Type 271 b.jpg (18.77 KiB) Viewed 5061 times
The Vickers-Armstrongs Type 271.jpg
The Vickers B.9/32 prototype takes off from Brooklands on a test flight.
The Vickers-Armstrongs Type 271.jpg (24.58 KiB) Viewed 5062 times
Last edited by Robert Hurst on 16 Apr 2003, 15:13, edited 1 time in total.

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#13

Post by Robert Hurst » 16 Apr 2003, 12:27

Hi

Vickers-Armstrongs Ltd Gun Turrets - Pt 2

Vickers-Armstrongs Wellington I

The nose and tail turrets of the Wellington Mk I were likewise of Vickers design, but at the Air Ministry's request embodied Frazer-Nash power-control units. In designing these turrets, B N Wallis had again been much concerned with aerodynamic drag, remarking of the 'windscreens' as they were still termed:

'The necessity for the screen to move with the gun about the fixed training axis has hitherto necessitated the provision of a windscreen of circular form, which, when a wide training angle of the order of + 90 degrees is required, prevents the best streamline form of the aircraft body being obtained, and thus involves considerable drag'.

To avoid imposing a circular form he adapted the windscreen to accommodate itself to changes in curvature and distance from the training axis as it moved round the nose or tail. The fixed upper part of the turret was transparent, and between this and the fixed lower part was a flexible band, running on tracks and having vertical openings for two 7.7 mm (0.303 in) Browning guns. The flexible band was formed of a central part and two end panels and means were provided for automatically engaging and disengaging the end panels from the centre part. Rubber strips closed the vertical slots for the guns. The transparent fixed hoods were of good aerodynamic form and were made if ICI perspex.

The armament of the Wellington Mk I consisted of a single 7.7 mm (0.303 in) Browning gun in the Vickers designed power-operated nose turret. In the Vickers designed power-operated tail turret, two pillar mounted 7.7 mm (0.303 in) Browning guns were carried, controlled by a handlebar type actuator. In the turret itself, the gunner's seat was fixed to the floor of the aircraft, making sighting a very hit or miss affair. A fourth rifle-calibre gun was mounted on a manually-operated mounting, and fired through an open hatch in the top of the fuselage.

These Vickers turrets proved very troublesome and were later replaced by Frazer-Nash nose and tail turrets.

The above text and the first two photos were taken from "Armament of British Aircraft 1909-1939", by H F King. The bottom photo was taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

Regards

Bob
Attachments
Vickers-Armstrongs turret layout.jpg
Vickers-Armstrongs turret layout.jpg (27.2 KiB) Viewed 5057 times
Vickers Wellington Mk I (b).jpg
Vickers Wellington Mk I (b).jpg (53.4 KiB) Viewed 5059 times
Vicker Wellington Mk 1  (a).jpg
An early Wellington I with Vickers turret.
Vicker Wellington Mk 1 (a).jpg (23.49 KiB) Viewed 5057 times

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#14

Post by Robert Hurst » 16 Apr 2003, 15:18

Hi

Vickers-Armstrongs Ltd Gun Turrets - Pt 3

Some more Wellington I photos.

The top photo was taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", b y R Wallace Clarke. The bottom photo was taken from "RAF Bomber Command and its aircraft 1936-1940", by James Goulding & Philip Moyes.

Regards

Bob
Attachments
Vickers-Armstrongs Wellington Mk I (a).jpg
Vickers-Armstrongs Wellington Mk I (a).jpg (38.47 KiB) Viewed 5043 times
Vickers-Armstrongs Wellington Mk 1 (b).jpg
Defensive armament comprised one gun in nose turret, one in roof of centre fuselage, and two in the tail turret.
Vickers-Armstrongs Wellington Mk 1 (b).jpg (17.59 KiB) Viewed 5044 times

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#15

Post by Robert Hurst » 16 Apr 2003, 15:29

Hi

Vickers-Armstrongs Ltd Gun Turrets - Pt 4

The Vickers-Armstrongs 40 mm Dorsal Turret

In line with the 1937 Air Staff assumption that multi-seat heavily armed fighters would be needed to counter hostile bomber formations, a development contract was issued to Vickers-Armstrongs at Weybridge for such an aircraft. Having already carried out a design exercise for a heavy gun mounting in a Wellington fuselage, the company decided to produce an advanced weapon system to suit the specification.

In February 1939 a scheme was prepared in which various specialist companies in the Vickers group would design components for a hydraulically powered dorsal gun turret, in which a 40 mm Vickers 'S'gun would be controlled by the movement of a predictor sight and rangefinder. The project was to be co-ordinated by a team at the Weybridge works, where the prototype Wellington Mk II (L4250) was to be prepared to accept the new turret.

The design of the power control system was undertaken by the Variable Speed Company (VSC) of Elswick. Turret rotation and gun elevation were powered by reversible hydraulic motors, the pressurised oil being taken from the aircraft's main hydraulic system. The turret consisted of a turntable supported by a substantial floor-mounted pillar, side loads being absorbed by rollers running in a circular track. The gunner's position was high and to the left side of the gun cradle, his head and shoulders inside a glazed sighting position. The turret cupola consisted of a heavy-gauge mushroom-shaped cowling with a central opening for the gun.

The gun was aimed by a predictor gunsight, designed by Captain Naninni of Vickers, linked to the hydraulic valves controlling the elevation and rotation motors. As the gunner aligned the sight on the target, the control moved the gun to an identical alignment. Although no records exist of the finer details and accuracy of the system (designed and produced by Troughton and Simms). it would appear to have been similar to the positional control of the Rose turret designed by K H Nicholls in 1943.

The 'S' gun was fed from a 25-round magazine via a flexible duct designed by Percy Higson at Crayford, who also supervised the gun mounting and associated services.

In November 1939 the completed turret prototype was set up on the Swanley firing range in Kent, often used by nearby Crayford armament engineers for test firing. The turret was powered by a portable hydraulic pump unit, and the gun was fired succesfully at various elevations, the control system seeming to be well co-ordinated with the sight. Meanwhile the Wellingtron had been prepared at Weybridge, and the turret was delivered for fitting into the prepared fuselage. During the early testing it was found that the geodetic structure was not sufficiently rigid for accurate gunlaying, and a large section amidships was rebuilt using a stressed skin construction (the FN.5 rear turret had been removed for centre of gravity reasons). The new turret was then fitted into its housing amidships.

The first flight of the new combination took place in early 1941, and proved to be quite eventful. Soon after take-off the pilot reported severe vibration at the rear end, making control of the aircraft very difficult. The offset sighting station had set up turbulence onto the fin, neutralising the rudder. The fact that the central single fin and rudder restricted the gunner's field of fire added to the need to redesign the tail.

It was decided to fit twin fins and rudders, consisting of the upper section of Wellington vertical tails braced to the rear fuselage. This improved stability, but movement of the huge turret continued to affect trim. Various other modifications were needed, and it was not until March 1942 that air firing trials commenced over Lyme Bay off the Dorset coast. These consisted of firing three rounds at minimum and maximum elevation at four positions on each beam - when the gun was fired at minimum elevation over the wings the muzzle blast ripped off a large section of wing fabric.

Trials continued until October, when the installation was considered to be successful, but the problem by this time was that the heavy fighter concept had been proved to be flawed. The heavy turreted aircraft would have been easy meet to German aircraft such as the Ju 88, let alone single-seat fighters. Nevertheless the Vickers turret was an impressive achievement, which was overtaken by events.

Details of the Vickers-Armstrongs Dorsal Turret

Aircraft: Wellington B.Mk II prototype
Armament: 40 mm Vickers 'S' gun
Power unit: VSC hydraulic system
Field of Fire:
Traverse: 360 degrees
Elevation: 45 degrees
Depression: 0 degrees
Weight: 567 kg (1,250 lb)
Armour: Nil
Ammunition: 25 40 mm (2 pdr) rounds
Gunsight: Vickers predictor sight
Power system: Troughton and Simms Ltd

The above text and top and middle photos were taken from "British Aircraft Armament Vol 1: RAF Gun Turrets', by R Wallace Clarke. The bottom photo was taken from "Wellington: The Geodetic Giant", by Martin Bowman.

Regards

Bob.
Attachments
Wellington with Vickers 40 mm 'S' gun turret (a).jpg
Wellington with Vickers 40 mm 'S' gun turret (a).jpg (21.04 KiB) Viewed 5039 times
Wellington with Vickers 40 mm 'S' gun turret (b).jpg
Wellington with Vickers 40 mm 'S' gun turret (b).jpg (34.12 KiB) Viewed 5036 times
Interior of the VA dorsal turret.jpg
Interior of the VA dorsal turret.jpg (36.18 KiB) Viewed 5038 times

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