SELECTED TECHNICAL GLOSSARY

Alclad

the trademark of Alcoa used as a generic term to describe corrosion resistant aluminium sheet formed from high-purity aluminium surface layers metallurgically bonded to high strength aluminium alloy core material.

Broaching

a machining process that uses a toothed tool, called a broach, to remove material.

Burr

a sharp edge created after machining.

Bush

a metal collar; can be a bearing or also a hardened guide for a cutting tool.

Bush plate

a device to hold a series of bushes for multiple hole drilling etc.

Butt-strap

a strap or plate covering a butt joint and secured to both pieces.

Die

a specialized tool used in manufacturing industries to cut or shape material using a press

Dimpling

a slight depression in a surface; often used to give strength to a flat sheet.

Duralumin

the trade name of one of the earliest types of age-hardenable aluminium alloys.

Finish ream

to use a reamer, which is a metalworking tool used to create an accurate sized hole.

Fixture

a device that holds the item to be worked on.

Former

a previously manufactured ‘shape’ around which metal can be bent.

Gauge

a device used to determine the exact dimensions of an item;  a measurement (often stated as a number) of how large a wire or metal sheet is,  either in diameter or cross sectional area.

Indexing

an operation of dividing a periphery of a cylindrical workpiece into equal number of divisions by the help of index crank and index plate.

Jig

a device to guide the tool towards the item to be worked on, but does not hold the item to be machined.

Joggle

a joint between two pieces of material formed by a notch and a fitted projection.

Lapping

a machining operation,  in which two surfaces are rubbed together with an abrasive between them, by hand movement or by way of a machine.

Layshaft

a secondary shaft, as in a sliding change gear;  a camshaft operated by a two-to-one gear in an internal-combustion engine.

Longeron

a thin strip of wood or metal to which the skin of the aircraft is fastened.

Moncocque

a construction technique that supports structural load by using an object’s external skin.

Nitriding

a heat treating process that diffuses nitrogen into the surface of a metal to create a hardened surface to a specific depth.

Panting

the movement of a metal sheet in a manner similar to a person breathing.

Poppet valve

used to control the timing and quantity of gas or vapour flow into an engine. It consists of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem.Trunnion a cylindrical protrusion used as a mounting and/or pivoting point.

Scarfing

a method of joining two members end to end in woodworking or metalworking.

Sleeve valve

a valve that fits between the piston and the cylinder wall in the cylinder of an engine where it rotates and/or slides, aligning with the cylinder’s inlet and exhaust ports at the appropriate stages in the engine’s cycle.

Spindling

to use a woodworking tool to cut receses in otder to ‘add lightness’

Stringer

a strip of wood or metal to which the skin of an aircraft is fastened

They Who Also Serve...

There has been bookshelf after bookshelf of books compiled, written and published about British aircraft, the Royal Air Force and the activities of its pilots during World War Two. Tales of derring do, bravery and gallantry quite rightly litter the bookshelves and libraries, but little has appeared in print about the what could be called the unsung heroes, those that designed, built and maintained the fighting equipment used to eventually defeat the enemy.

This is all the more incredible when one realises that there exists a huge archive of images that have survived which clearly show the skills and scale of what went on. These images of war - many of which are seen here for almost the first time in seventy years - form a remarkable tribute to the designers, engineers and workers who did so much.

A series of Expansions...

Following the end of the Great War, the Royal Air Force was drastically reduced in both manpower and equipment. The application of a ‘Ten Year Rule’ in which the British Government foresaw no war being fought during the next ten years resulted in minimal defence expenditure throughout the 1920s. These budgetary constraints resulted in many squadrons having to struggle on through the same period with aircraft originally designed during World War One, such as the DH9A and Bristol F2B Fighter.

Each year the ‘Ten Year Rule’ was extended until the early 1930s, when it at last became apparent that Germany was developing expansionist and aggressive tendencies that could no longer be ignored. The British Government and Air Ministry at last began to develop plans of their own to expand and develop the Royal Air Force. A number of plans were approved by the Cabinet, but each one was often replaced by a revised one before the original could be completed.

Between 1933 and 1939 the Royal Air Force was given higher priority in terms of rearmament plans than the other services. The policy was driven by the pursuit of parity with Germany more than by defence and strike needs, for there was no fixed ratio of bombers to fighter aircraft to guide procurement.

Of all the RAF expansion schemes between 1934 and 1939, only scheme F was actually completed. Importantly, this scheme included realistic numbers of reserve aircraft and personnel, something that the earlier schemes had failed to do. The RAF also issued requirements for modern fighters in 1935, and heavy bombers in 1936. In November 1938 the emphasis moved from bombers to fighter defence, but delays meant that modern aircraft were in short supply. To demonstrate how things changed: in 1934 42 squadrons existed, providing a first line strength of some 800 aircraft. By 1939 this had grown four-fold. At the same time there had been a major increase in aircraft and aero-engine production and a rapid expansion of training to provide the new air and ground crews.

As a result of this expansion there was naturally a severe shortage of manufacturing facilities. Existing aircraft manufacturers did not have ability to cope, so a plan was developed by the British Government to implement additional manufacturing capacity for the British aircraft industry. Developed by the Air Ministry under the internal project name of the Shadow Scheme, the project was created by Sir Kingsley Wood,  the Secretary of State for Air, and headed by Herbert Austin.

The Shadow Scheme saw many locations around the country handed over to companies for the purpose of aircraft or aero-engine production and is worthy of a book in itself. As the war progressed, it seemed that the whole of the country was involved in aircraft parts manufacture.

In general terms, each outside contractor was responsible for certain components, and concentrated and specialised on only one or two portions of the aircraft. For this outside production, special arrangements had to be made to deal with imparting the necessary information to the firms concerned.

Usually a special department was formed at the parent company, known as the Outside Production Office, to deal with the expansion of production of whatever aircraft it was, in addition to extensive repairs to existing aircraft. Staff was also sent out from the works to help the daughter firms in their production.

The functions of the Outside Production Office were briefly as follows:—

  • (a) To arrange facilities at the parent firm’s works for key workers to receive training in production methods and inspection.
  • (b) To supply technical information, including supplies of copies of drawings, modifications and planning sheets.
  • (c) To arrange for the supply of templates, sample parts and components for use in the preparation of jigs and tools.
  • (d) To supply information and drawings for all tooling equipment.
  • (e) To assist daughter firms in the selection of tools and equipment.
  • (f) To answer all queries raised by and through daughter firms in connection with methods of manufacture.
  • (g) To render advice and give technical approval on repairs and also approve where possible parts which were not to drawing and might otherwise be scrapped.

Production was divided between two main groups. The parent firm had a local sub-office to deal with all technical queries arising from shop errors and rectifications, etc., which acted in a decentralized capacity to give technical decisions which if referred to head office might only be obtained with considerable delay.

All firms concerned in the Production Group had considerable administrative and manufacturing experience and were fully competent to deal completely with matters arising out of their contracts as between themselves and the Ministry of Aircraft Production. From a contractual point of view they were of equal status with the parent firm. Generally speaking, it was discovered that it was best to let each member of the Production Group arrange for its own sub-contracting.

When it came to design changes, those of a major character were made to meet differing conditions in the field. These and other changes were discussed at a meeting of the principals from the Production Group firms under the chairmanship of the Director-General of Aircraft Production. Any changes necessary to give improvement in performance or to meet the changing conditions in service were viewed every fortnight by the Local Technical Committee at the parent firm’s works. This committee was made up of senior representatives from the parent firm’s technical and production staff and also from the Air Ministry. The daughter firms provided representatives present at these meetings to keep them up to date with new developments and to give their views on production matters.

Previous
Page
Next
Page

Contents

If you find an error or have any questions, please email us at admin@erenow.org. Thank you!