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Aviation History
1957
1957 - 0170.PDF
172 FLIGHT, 8 February 1957 DESIGN FOR PRODUCTION . . . merits must be prepared to allocate these extra components veryearly in the programme if die full benefit is to be obtained from the prototype aircraft (Fig. 3). Mention has already been made [continued the lecturer] of thenecessity of completing structural test specimens before flight and of the early completion of tunnel tests before the construction ofcontrol surfaces. There are many other facets to the successful initiation of a fully approved production programme and thewhole picture from initial design to final product is illustrated in Fig. 4. This can be used as a master progress chart to assessachievement against targets, and highlights the necessity for making special efforts to correct any items which may become out ofphase. Each item should have its own separate planning chart for this purpose. The diagram illustrates many important prin-ciples if the project is to be successful: — (a) Wind tunnel tests should be completed as soon as possible so thatstabilizers, control surfaces, etc., may be finalized in time to avoid changes in the shops. (b) Mechanical tests on detail parts should also receive top priority indesign and manufacture, for the same reasons. (c) Maximum engineering development on all "systems" should becompleted on ground rigs before these items are installed in the aircraft. (d) The static airframe tests should be completed before the flight ofthe first prototype to avoid strength restrictions on flight manoeuvres or pressurization. (e) Stiffness and resonance tests should be completed and assessedbefore the flight of the first prototype to avoid speed restrictions. (f) Fatigue tests, both detail and airframe, should be completed by thecommencement of the production programme. (g) Flight tests including winterization and tropical trials should becompleted before the production run starts. (h) C.A. release, or C. of A. should be obtained before delivery of firstproduction aircraft. There is no doubt that the quality and type of equipment, andthe conditions under which they are used can have a marked influence on output in design. The British specialist team whovisited the U.S.A. under the auspices of the Anglo-American Council on Productivity reported that companies had paid specialattention to drawing equipment and adequate accommodation and amenities, even to the extent of experimenting with multi-colourschemes of decoration. One firm reported a "considerable" increase in output with the same staff, merely by moving to morecommodious accommodation. Adequate reference space is a pre- requisite for any designer aiming at productivity. The loss ofvaluable time by design draughtsmen trying to make do with a very limited reference table is considerable. A comfortable adjust-able seat with a back and a readily adjustable drawing table with a light green backing paper, allied to a shadowless lighting systemgiving not less than 75 foot-candles at board level is suggested as an ideal. Drawing machines of various types to suit office prefer-ence are available, but the old Tee square has undoubtedly out- lived its usefulness as a production instrument. It is essential that the design office is fully aware of the facilitiesavailable immediately in the workshops. An enterprising produc- tion organization is constantly adding new equipment and intro- ducing new processes which are potential improvements inproduction times. Copies of a manual giving details of all the "special plant" installed in the author's warks are circulated to allsection leaders and filed for reference in the technical library. The type of construction necessary for a new project may bedictated by design considerations if, for instance, flight speeds are much advanced beyond current designs. Early consultation withworks departments is necessary to obtain new plant and introduce new techniques. In less sophisticated regimes, such as that ofcurrent civil aircraft, alternative methods are possible and here a compromise must be made between what is essential for designand what is expedient in the works. This process can also work in reverse where the production departments claim productionadvantages for new methods which have to be examined for suitability by the design office. The key to success guiding a new project through all its stagesis effective liaison between production and design at all levels. Day-to-day queries from the shop floor are usually handledthrough the process planning department representatives, using shop query forms (with or without prior verbal consultation) withthe particular design office section concerned. This scheme demands immediate and sympathetic consideration by the D.O.and depends for its success on the goodwill existing between the departments. Modern tendencies for D.O. and works to beseparated makes this more difficult and intrinsically demands a higher standard of accuracy and clarity on initial drawings ifirritating delays are not to occur. Production advisers are usually people with a wide experience. . . who are attached to the D.O. Their duties vary in different organizations from merely consultative to a responsibility for vet-ting all drawings for suitability for production. The development committee must consist of members of high executive standingwith the power to make decisions on the spot or to order more detailed investigations. This committee should meet as soon asthe chief designer can give any indication of the probable shape and size of the project and certainly well in advance of issue ofdrawings. It is doubtful whether any drawing system really exists and inany case the system is often geared to the particular organization in which it is to operate, causing quite a few headaches whenparts are sub-contracted. The S.B.A.C. system has, however, gone a long way to solve this problem and most firms are now using itin one form or another. Latest thoughts indicate that the letter- ing and numbering system should enable the location of a detailpart to be recognized, i.e., the aircraft and component on which it is used. The character of drawings varies considerably and quitelarge reductions in D.O. time possible by departing from the prin- ciple of: one detail part, one drawing. Schedules on drawings(instead of separate schedule sheets) also leads to economy in D.O. time. Is it too much to hope that planning and D.O. could be integratedto such an extent only one set of schedules or groups need be written? Apart from duplication the present system can lead tomany difficulties and misunderstandings. For example the weights department must be acquainted with the planning groups in order Fig. 3 (below). An allocation chart covering the first five airframes to be constructed. Although presented anonymously this chart could well refer to the A.W.650, the forthcoming Armstrong V/hitworth transport. Fig. 4 (right). An engineering and production phasing diagram, showing target dates for completion of the various stages. This again indicates the sort of programme which Armstrong Whitworth have currently in mind. i... WING Is, FUSELAGE 2« WING 2«c FUSELAGE 3.o WING — 3.o FUSELAGE 4IK WING — 4,. FUSELAGE (!•. TAILBOOM • TAIL UNIT - [2M> TAILBOOM - TAIL UNIT "' .- FUSELAGE AND WING K TAILBOOM - TAIL UNIT •'•< TAILBOOM - TAIL UNIT 1 STATIC FUSELAGE TEST STATIC TEST COMPLETE AIRCRAFT FATIGUE TEST COMPLETE AIRCRAFT Is- PROTOTYPE FIRST FLIGHT 2 »o PROTOTYPE FIRST FLIGHT 3 w PROTOTYPE FIRST FLIGHT O PERCENTAGE COMPLETE25 5O 7S FINAL ASSEMBLY COMPLETE IOO START| r.. . OF MAlM PRODUCTION o i 16NO. OF AIRCRAFT
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