Engine Production

by F R Banks
Group Captain F R Banks, OBE, is a specialist in aviation fuels. From 1930, until the outbreak of the war in 1939, he held the position of technical manager and chief engineer of the Ethyl Corporation (later the Associated Ethyl Co). Group Captain Banks began his engineering apprenticeship when 13 years of age. He served during the entire period of World War I in the Royal Navy in mine-sweepers, submarine chasers and motor torpedo boats. After the war. he specialized in marine Diesel engines. and subsequently became the chief experimental engineer with a well known aero-engine firm. He now directs aero-engine production for the MAP.

Wartime demand has been met by the expansion of Britain's major aero-engine firms and the development of "shadow factories" to augment them.

The directorate general of engine production in the Ministry of Aircraft Production is responsible for ensuring that adequate capacity is available for the manufacture of engines, to meet airframe requirements. In planning this capacity with the various aero engine manufacturers, due account has also been taken of the need for spares — in terms of complete engines and also "bits and pieces."

This may mean, in the case of an entirely new engine, completely new jigging and tooling together with the provision of additional and, perhaps, special purpose plants or, if the engine to be produced is another version (or "mark") of an existing type, only particular jigging and tooling for the altered or new parts.

However, before all this happens, a great deal of development work on the new model will have been done by the firm concerned; in order to see whether, in the first place, the engine will give the improved performance expected of it and to force the pace if it doesn't and, finally, when this improvement is obtained — be it higher takeoff power and greater power at altitude or better specific fuel consumption — whether the new engine is reliable.

It cannot be said too often that, in the particular case of the aero engine, development is production. It is only by intensive development that a successful engine can be put into full production uninterrupted (relatively) by modifications. Of course many modifications have to be faced, but major modifications, which are due to lack of, or ineffective, development have a disastrous effect upon production.

It pays the parent engine firm to have a large development department with plenty of machine tools and adequate test equipment; and a capable staff with someone with foresight at the helm who is in direct contact with those who use his firm's products. In addition, there must be a large staff of capable installation engineers whose job it is to go out into the field and supervise the handling of the new engine.

The production organization of the large aero-engine forces has often been criticized; it is said that they could produce many more units with a better shop layout. Their critics are usually ignorant of the evolution of the average high-duty aero engine and cannot see that in the past and prior to the war most of these firms were just one big development department with few special tools and many general purpose ones. And that they were, and still are the places in which engines are born. Their job is to nurse these engines through their teething and growing pain periods.

The demands of war are such that it is often necessary to introduce quickly and, of necessity, in limited numbers, an engine of improved performance to fit an existing type of aircraft. It is then that the value of the firm having a large and efficient development section is appreciated. How many times lately have we been thankful for such a firm!

Since the close of the last world war there has been a small but robust group of companies in Great Britain designing and manufacturing high quality aero engines. And even in the lean years that the British aircraft industry has faced on different occasions since 1918, the air staff was able to keep the chief aero-engine firms alive. Both this policy and this fact have been of inestimable value to British aircraft designers who were thus assured of the advantage and cooperation of an efficient and progressive sister industry.

British aero engines have kept abreast of world design and they have undoubtedly influenced foreign design considerably as well as being licensed for production abroad.

The number of designing and production forces can be counted on the fingers of one hand; they are generally known as the parent firms. The three principal forces are Bristol, Rolls-Royce and Napier.

In order to meet war requirements, the parent aero-engine firms have been expanded and other factories have been built to manufacture their engines on a production basis. The latter, naturally, are not concerned with development — only production. They are, in some cases, managed by the parent firm and in others are staffed, managed and run by a number of famous British automobile manufacturing concerns.

These plants, in most cases, are known as "shadow factories" but they are, in fact, large Government-owned factories managed and run for the Ministry of Aircraft Production by industry.

The history of British aero-engine production in this war will be written some day and it will have a deservedly high place in the annals of engineering.

There is, in the first place, a very close liaison between these firms and the airframe (or aeroplane) builders. The normal practice is for an aeroplane designer to visualize forward requirements and put a design for a new aeroplane on paper which in turn will call for an engine of a certain power. He will approach the aero engine builder and ask what he has to offer. Maybe he has nothing to offer at the moment but will have something ready by the time the first machine is on the stocks. This may be an entirely new engine or it may be an improved model of an existing type. In peacetime, such a combination of the aeroplane and the engine might be put forward to the Air Ministry as a private venture, or it might have been built to satisfy a definite specification. Time, then, was not necessarily important and the prototype machine would be built in due course and tested. If it was promising, a few more would be built for use in RAF squadrons so that experience could be gained before a production order was given. From the time the project was first considered, to the time when the machine was in full production, might be anything up to four or five years. And, as is usually the case with engines and aircraft, it would probably be obsolescent; new marks of the same engine would already be appearing (at least experimentally) to replace it.

In war, of course, time is very precious and as soon as the air staff indicate their wish for an aircraft of some particular type the design staffs of the firms concerned get busy and offer something, on paper, in a relatively few months. The "prospectus" for a new machine will come out fairly quickly, based on the aggregate knowledge of the aeroplane and engine builders but, of course, it takes many months to do the detailing of a new aeroplane.

However, the needs of war are such that an aeroplane is now ordered "off the drawing board" and jigging and tooling begins soon after its design is approved.

The speed at which this machine, as a whole, will be produced and flying depends upon the success of its initial design and also upon whether the engine is of entirely new design or is an improved "mark" of an existing type. Before the war, when speeds ranged around 200 mph and when the biplane was favoured by the RAF, it was not difficult to evolve a new type of machine. But the change to the monoplane and the demand for speeds around 300 mph brought a whole train of trouble — wing flutter for example — which had not previously been apparent. Now we speak quite casually of speeds of 400 mph; and the difficulties of the aeroplane designer are further increased. Two years will probably elapse from the initial design stage to the completion of the prototype aeroplane.

The production of the engine, however, is quite another matter since it takes about four or five years to get a new type engine into production from the drawing board. This period will vary according to the ability of the development department or the engine firm in question, but it has never been much less than four years. The experimental engines are produced in, say, 18 months or two years and, if reasonably satisfactory, are given a special category test in order to enable them to be put into the prototype aeroplane so that flight testing can proceed. In the meantime the development of the engine on the test bed is being pushed hard and the jigging and tooling for its production is going ahead. It is, of course, known what machine tools will be required, in numbers and type; but, inevitably, the jigging and tooling may have to be altered according to the degree of trouble met during bench and flight testing and the consequent amount of redesign which becomes necessary. So, eventually, a complete aeroplane is evolved during war time. But a good deal of frantic work, both on the part of the aeroplane and engine builder, is necessary to produce it.

Naturally, if only an improved version of an existing engine type is required, then a certain amount of time is saved. While, therefore, in peacetime, an engine was in a reasonable state of development before its production commenced, in war time, we have to face a good deal of teething trouble while the engine is already being flown and, in fact, has been fitted in relatively large numbers in aircraft actually engaged on war operations.

Where, in the past, engines have been produced only by the parent firms, it was a relatively easy matter for the parent company to produce and keep step, during production, with any alterations which may have become necessary as the result of further development. But now engines have to be produced by firms which have not previously had aero-engine experience, such as the "Shadows."

The "shadow" engine industry in this country has undoubtedly done a fine job of work and the cooperation between the parent firms and their "shadows" has been, and is, excellent. It is, of course, difficult to introduce a modification to an engine when it is in large scale production by such firms. And every care is taken to see that a modification is absolutely necessary before it is approved and incorporated.

The aero-engine industry before the war, in the days of retrenchment, was not large enough to support the demands with which it is now faced for skilled workmen. Indeed there is a general shortage throughout the United Kingdom of skilled machinists and fitters; consequently, large training schemes have been initiated. Men and women from all walks of life are now in our factories, operating machines and assisting in the assembling and testing of aero engines — insurance agents, shop assistants, milliners, manicurists, clerks, actors, actresses, musicians, and so on. These men and women have shown remarkable keenness in their new work and many have demonstrated real ability.

One of our "headaches" (particularly acute in 1940 and 1941) has been the difficulty in finding managerial staff. In the heavy bombing period, after the fall of France and during the Battle of Britain, it was necessary to disperse some of the larger factories. It is not generally realized how difficult this was because it meant multiplying supervisory staff and often housing workmen in rural areas hardly capable of accommodating more than a few thousand of their own inhabitants. Yet it has been done with only a temporary drop in production which overall has contained steadily to increase.

There are many marks of aero engines in production in Britain today. Indeed one of the problems of the directorate general of engine production is the rapid improvement in engine types. There may be six new types in production now; there will be as many further improved types to produce 12 months hence. If an engine is outstandingly successful, the Air Staff will wish to get as many into operation as quickly as possible. A hundred fighters, modified to take a new engine, may be demanded for delivery within a matter of a few months. This raises at once a multitude of difficulties. The airframes themselves have to be modified. The installation and equipment may have to be changed. The capacity required for, say, new radiators must be doubled and so on. The question of spares also arises. Aircraft, whether in the front line or in reserve and according to type, need, in addition to their basic quota of from one to four engines, a certain number of spare engines. All these spare engines require spare parts, which must be dispatched and held in store for maintenance wherever the engine is to be used. The demand for spare parts is enormous and absorbs a large part of the productive capacity required for the manufacture of the complete engine.

This, coupled with the "production cycle," the time taken to obtain materials, plan production, fabricate and assemble the component parts of an aero engine, stretches the resources of the engine industry severely.

Emergencies arise and must be dealt with swiftly. Last year, during the "blitzing" of Britain, the necessity for flame-damping the exhausts became apparent. This entailed a new design of exhaust system which, when finalized, had to be fitted with all possible speed. Working parties had to toil night and day to fit these system so that the night fighters could get within firing range of the bombers, undetected.

Finally, a word about the actual engines. The two most famous British makers of engines whose products had a world wide reputation even before the war have more than justified this reputation — Rolls-Royce and Bristol. Their engines have made history. The Rolls-Royce Merlin is a liquid- cooled, 12-cylinder V engine which started its life by giving 900 hp at what is now regarded as a very low altitude. Today, it has a 50 per cent better all-around performance and has been developed to. maintain it at extremely high altitudes.

The Bristol Company, famous for their air-cooled Pegasus and Mercury poppet-valve engines, which are still giving valuable service in a number of important operational aircraft, started producing their new 14-cylinder sleeve valve air-cooled engine, the Hercules, before the war. It is now in full production and gives more than 1,500 hp.

The Napier Company have also developed, and are building, a liquid-cooled sleeve-valve 24-cylinder H engine, known as the Sabre. This engine has yet to win its spurs in war, but it can be stated that it is the most compact engine yet built, in any country, for an output of over 2,000 hp.

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 162-163, 236, 240, 242.
The original article includes a thumbnail portrait of the author and 5 photos.
Photos from the RAF.

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