Armament Production

by J W Mills
Mr J W Mills, OBE, Director of Armament Production, Ministry of Aircraft Production, formerly managing director Halley's Industrial Motors. Has held managerial posts with Humber, Coventry Climax Engines, Sunbeam Motor Co and Austin Motor Co. Mr Mills has made frequent visits to the United States and to leading production centers on the Continent. He is a member of the Institute of Automobile Engineers of Great Britain and of the Society of Automotive Engineers in the USA.

Most people think of aircraft armament in terms of guns and bombs. In practice it covers an enormous range of equipment from complicated gun turrets to fuses, as well as a number of weapons. Upon its quality and disposition depends the offensive and defensive efficiency of the aircraft.

Supply of this highly important material to the Royal Air Force is undertaken by the directorate of armament production in the Ministry of Aircraft Production and by the Ministry of Supply. Research into and development of all kinds of aircraft armament is undertaken by other departments of the MAP. But although armament covers many types of equipment, the main problems must, of course, always be the adequate supply of the right kind of guns, power-operated gun turrets, ammunition and bombs.

On the outbreak of war in Europe nearly three years ago the air defence of Britain was dependent upon the eight-gun fighter. The Secretary of State for Air, Sir Archibald Sinclair, during the height of the Battle of Britain described its adoption as "one of the greatest decisions in the history of war."

This article appears at a time marking the second anniversary of the defeat and rout of the Luftwaffe in their major daylight attacks upon England. That was in 1940. But it was seven years earlier that the eight-gun fighter was conceived; a tribute to the men who foresaw the need for a fighter of superlative quality if the bomber of the future was to be defeated.

For all practical purposes the eight-gun fighter can be traced to a blue foolscap minute in a red-covered secret Air Ministry file. That was on April 4, 1933. It was signed by the late Wing Commander A T Williams.

Consideration was being given to the replacement of the Hawker Fury and the Bristol Bulldog fighters with a biplane mounting four, six and eight guns. Because the estimated performance figures set out in that minute were not far enough in advance of what aircraft then building could do, the project was temporarily dropped.

One objection to the extra armament was that it would have the effect of making the aircraft too slow. But the advent of the low-wing monoplane made possible the mounting of all eight guns within the wings — four in each. Also, because the guns would be firing clear of the airscrew, synchronization mechanism for firing through the airscrew was no longer necessary.

Air Vice-Marshal R S Sorley, then a squadron leader, predicted that the extra guns would mean the loss of only one mph, an extra four seconds in the time taken to reach 20,000 feet and an operational ceiling of only 1,000 feet less. Of course these figures have no relation to present-day performance.

Experts, therefore, decided that these slight losses in performance were more than counter-balanced by the increased firepower. The issue was complicated by the development in France of a cannon gun. It was claimed that only one hit from this gun would prove fatal to any aircraft. This gun, however, was in its infancy and had the disadvantage of having to be mounted on the engine and fired through the airscrew boss to secure sufficient rigidity.

In November, 1934, the eight-gun fighter was decided upon. Monoplanes, later to become the famous Spitfires and Hurricanes, were then on the drawing board. It must be recorded that much of the credit for the development and ultimate adoption of the eight-gun fighter must go to the late R J Mitchell of Vickers Ltd, creator of the Spitfire and to Sydney Camm of Hawkers Aircraft Ltd, designer of the Hurricane.

The original Spitfires and Hurricanes were equipped with the Browning .303 gun. The latest and vastly improved types are fitted with cannon guns capable of firing three times the former weight of ammunition.

The Browning was developed from the USA Colt gun, being modified for the RAF in Great Britain. Together with the Vickers gas-operated "K" gun, they were the principal weapons in use in RAF aircraft on the outbreak of war. Production has been enormously expanded and the Browning gun is now being turned out in immense numbers each month in Britain and Canada.

Royal Air Force aircraft in September, 1939, had two important advantages over German warplanes — protective armor including bullet-proof glass and the power-operated gun turret. The war had been in progress more than six months before the Luftwaffe developed effective armor for its pilots and vital parts of the aircraft.

How well our pilots were protected even in those early days of the war can be judged by the following story. A Coastal Command Lockheed Hudson aircraft had been on reconnaissance over enemy territory and had had a successful engagement with Messerschmitt fighters. When the British pilot landed he complained of a splitting headache. He said that he had never suffered from one before and was very disturbed. He was asked if his aircraft had been hit and he replied, "No." But when mechanics were examining his machine they discovered a huge dent in the armor shield behind the pilot's head. His aircraft had been hit by a burst of machine-gun fire. The armor had not only saved his life but had afforded such protection that he hadn't known a thing about it.

The Germans, however, while slow in adopting armor had made considerable advancement by the time they went to war with self-sealing petrol tanks. They were using with great efficacy a rubber compound spread over the metal surface of the tank. When hit by a bullet, the hole immediately sealed up. At first, the RAF used armor for protecting the petrol tanks, although experiments had been in progress with a self-sealing type long before the war.

It became obvious, however, to both sides that although the eight-gun fighter had a devastating fire power, spitting out its bullets at the rate of 10,000 a minute, the cannon shell was necessary to penetrate the new protective armor.

The development of the 20-mm shell-firing gun, popularly known as the cannon, had been in progress in Britain, as well as in France and Germany, before the war and small quantities were being produced. The Hispano-Suiza type, which had been selected by the RAF, had many teething troubles which were gradually overcome, and for some time now it has been in large-scale production, incorporating a continuous shell-feed mechanism, both in Britain and America.

Provision of ammunition for the RAF is solely the responsibility of the Ministry of Supply, and this department also meets the requirements of the Navy and Army. Vast quantities are being produced in Britain, the United States and Canada and are allocated by a special Anglo-American supply committee.

As stated above, nearly all British bombers when war broke out were equipped with power-operated turrets mounting a battery of guns. German bombers, besides being under-gunned, did not have this advantage. In consequence they were particularly vulnerable when attacked by fighters. The RAF and the Luftwaffe had followed contrary policies. As the result of experience gained during the Spanish civil war, the Germans came to the conclusion that a bomber's best defence was speed. This, however, was a wrong decision because it was based on a faulty premise. Fighter opposition in Spain was negligible and the quality of the aircraft being used was not up to the standard likely to be experienced in a war between major powers.

In honesty to the German Air Staff, it must be stated that they were unaware of the great progress made in Britain in radiolocation — probably the determining factor in the Battle of Britain. True we possessed fighters of superior speed and firepower, flown by pilots with indomitable courage, but there was insufficient margin of speed between the British fighter and the German bomber to be really the deciding factor without the scientific aid of knowing where the bomber was and so placing the fighter in the best position to intercept it.

But the Heinkel He-111 and the Dornier Do-17 did suffer heavily because they were unable to adequately protect themselves. So our Spitfires and Hurricanes shot them out of the sky in great numbers even when the Luftwaffe tried vainly to protect its huge bomber formations with hordes of Messerschmitt fighters.

British bombers have always been heavily armed, it being contended by the British Air Staff that a bomber should be capable of fighting its way to the target. This has proved sound policy, our day and night bombers often coming out best when attacked by fighters. During a mass raid on Bremen in June this year a Stirling shot down three out of five Messerschmitts and arrived home safely.

The early types of gun turrets were hand-operated. The power-operated turret was an important advancement because it would be physically impossible for a gunner to traverse a hand-operated turret in an aircraft flying at present-day speeds.

British firms — the Bristol Aeroplane Company, Nash and Thompson and the Boulton-Paul Aircraft Company — have been in the vanguard of the development of these turrets for carrying single and multi-guns with high ammunition capacity.

The first Bristol turret was developed in 1935, and the type was accepted for use in the RAF in the Blenheim medium bomber. It is electric-hydraulically controlled. Today this turret is in daily operation against the enemy in Blenheims, Beauforts and other types. Large-scale production commitments of aircraft and engines have made it necessary for the Bristol company to pass on manufacture of these turrets to other famous engineering companies.

The two other main types are the Frazer-Nash and the Boulton-Paul.

Power for the Frazer-Nash turret is derived from a pump incorporated in the engine which supplies oil under pressure to a high-efficiency oil motor which rotates the turret. Elevation and depression of the gun is effected by pressure-operated rams and the gun controls are centralized, similarly to those on the handlebars of a motorcycle, for ease of manipulation.

The Boulton-Paul turret is also characterized by its electro-hydraulic operation; power being supplied from an electric generator driven by the engine. An electric motor in the turret coupled to an oil pressure pump rotates the entire turret and its guns. The controls, in this case, are centralized and rather resemble a pilot's "joystick."

Turrets must also incorporate all the ancillary services which the gunner finds necessary, such as electric lighting, oxygen supplies and telephone communication with the pilot and other members of the crew. A very high standard of efficiency is obviously essential.

At the outbreak of war, the RAF had large stocks of bombs ranging in size from the small 20- and 40-pound anti-personnel bombs for use in cooperation with the Army to large high explosive bombs for use against industrial areas and shipping. These have developed in size and power.

Bomb requirements vary a great deal. They are needed to blast large areas, for the penetration of buildings and deep-seated targets, for the piercing of ships and the armor plating of battleships.

Manufacture is on mass-production lines, either by casting or forging processes. The big high capacity bombs are, however, too large to be made in one piece by either process and are formed of composite structures of immense weight.

Incendiary bombs which are also manufactured in immense quantities are of two main types — the cast magnesium bomb and the case bomb filled with inflammatory composition. The requirements of magnesium metal for filling the first type has entailed the erection of large metal-producing plants specially for this purpose.

Production of components to match that of bomb bodies is also a problem of considerable magnitude, especially in the case of the larger bombs for which several sets (in some instances five) of explosive parts are necessary.

Equipment to produce these necessitates the very latest type of machinery, much of which is semi-automatic or fully automatic. Fabrication has been modified to enable automatic types of welding to be used.

This article was originally published in the September, 1942, "Special Royal Air Force Issue" of Flying and Popular Aviation magazine, vol 31, no 3, pp 164-166.
The original article includes a thumbnail photo of the author and 5 captioned photos.
Photos are not specifically credited, but seem to be from the British Air Ministry.

Photo captions: