FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1953
1953 - 0039.PDF
9 January 1953 first point, he gave remarkable figures showing that if the empty weight of an airliner were increased from 50 to 52 per cent of the gross weight the increase in capital cost of the aircraft would be about £100,000 for a 150,000-lb aircraft; he also pointed out the adverse effects of having to bear increased landing costs and fuel charges. From the revenue-earning point of view it appeared that each pound of gross weight saved could earn about £200 during the life of the aircraft. Dr. Russell then dealt in a similar manner with aircraft drag. Bristols are, of course, pioneers in the use of functional mock- ups. Dr. Russell described these devices as being most useful in the development of the aircraft auxiliary power systems in as near their correct environment as possible; unless skilfully arranged, such systems could resemble an unravelled woollen jumper. He dwelt briefly upon the hydraulic system as an example of what could be achieved with a functional mock-up. After the initial tests had been completed the layout could be used for the life- testing of certain components and the trial installation of new equipment. Attention was then turned to the basic structure of the aircraft. Dr. Russell appeared to have little faith in spot-welding for skin attachment. He proceeded to a concise discussion of various types of riveting, and then turned his attention to more modern methods of metal bonding. Some of the older engineers, he said, could remember the days of wooden aircraft when, with the aid of a pot of glue and a mouthful of brads, aircraft grew visibly from day to day. While there was now no prospect of reverting to rural materials, recent developments in adhesives for metals opened up new possibilities for area jointing as an alternative to point attachments by rivets. Dr. Russell, whose company has done much to further metal bonding processes, quoted many advantages enjoyed by these methods. As a general dictum it was advantageous to break the structure down into panels and sub-assemblies, both from the point of view of maintenance and to facilitate assembly with free access to all faces. An interesting point arising here was that whereas at one time "a fancy-shaped fin" expressed the designer's individuality, such outlines were no longer likely to be seen. Considerations of mass production and interior equipment tended to demand straight tapers. Sandwich construction—a low-density core stabilizing load-carrying skins—appeared uneconomical unless the core weighed less than z\ lb/cu ft. Dr. Russell did not believe that major structural components could be economically made by employing sandwich construction, although small items such as tabs, bulkheads and doors might profitably be made by pouring a low-density filler into pre-formed skins. The strong plastics, however, had a wider scope and Dr. Russell discussed possible applications of materials such as Durestos and Fibreglass. Among other new materials some of the magnesium alloys appeared extremely attractive and were amenable to rapid production techniques with "tantalizing" prospects. The only major barrier to such alloys was probably their poor fatigue life. C. E. FIELDING'S PAPER PROTOTYPE TO PRODUCTION" was the title of the paper by Mr. C. E. Fielding, O.B.E., A.F.R.Ae.S., M.I.P.E. (works director, A. V. Roe and Co., Ltd.), who dealt with the forward planning and control necessary to guide a new aircraft through its various phases up to the completion of the first aircraft, assuming the prototype had completed its trials. Based on the delivery programme specified in the contract, began Mr. Fielding, the activities of three main groups started concurrently, to decide respectively how, when and where the aircraft was to be built. The first group was that which prepared piece-part schedules and bulk material schedules for ordering purposes, and a speed-up in this group's work was possible, using the right type of paperwork. The speaker then gave a detailed description of this paperwork, and how it fitted in to the produc tion system as a whole. Typical examples of parts schedules, material posting sheets, control record cards and weekly progress reports were illustrated. The second department's job, he continued, was to establish process planning and to arrange tooling. Of basic importance was the process sheet, giving details of each operation, tool required and estimated time of manufacture. The methods of manufacture decided on varied according to the quantity to be produced and the type of plant available, while the question of interchangeability had always to be considered. An early tooling-programme should be made out, both for the issuing and the manufacture of tools; and a target established for the necessary sub-contracting. In the design of jigs and tools, the use of standard parts and drawings I was an important factor in reducing the total time required. The third main task was the preparation of target programmes and an analysis of capacity in relation to machine tools, floor space and labour. For each section of the aircraft, a target production programme showed the component programme and the timing I of the various stages right back to the date when tools and material were required, and thus the material, tool and detail priorities 37 could be obtained. Requirements for special tools should, of course, be made known at an early date. A man-hour analysis and labour assessment was then made, using known figures for previous types, the respective structure weights and the "80 per cent law" (or a more appropriate local- percentage law). Problems of labour procurement and manufac turing batch sizes followed; the first batches should be small, and later batches large. After the pre-production arrangements had been completed, job cards were to be issued, based on the piece- pan production programme, together with route cards and material requisitions. Progress on particular sections was noted by means of weekly reports, and man-hours could be checked. Final assembly should cause few delays, assuming interchangeability problems had been properly handled. Mr. Fielding concluded, "With careful plan ning and suitable weekly reports to check the position at the various stages, it is possible to keep a grip on the situation, and although this can be affected by circumstances outside your own control, proper organization will minimize their adverse effect." H. POVEYS PAPER T HE second "Prototype to Production" paper was read by Mr. H. Povey, A.F.R.Ae.S., director (Aircraft Production), de Havilland Aircraft Co., Ltd., and was largely based on the experience of his company with the Comet. The normally long period between first prototype flight and first production delivery for any aircraft (1-2 yr for light aircraft, 3-7 yr for large types) could be reduced, the speaker claimed, by effective and early decisions on the three main points of financial risk, flight testing, and tooling. For civil aircraft, these decisions were greatly influenced by competition and the need to give attractive delivery dates to customers. In the case of the Comet, heavy financial risk was undertaken by the company at an early stage, once delivery, price and per formance guarantees had been made. A big effort was made to get the prototype into the air at the earliest possible moment, in order to eliminate snags and obtain the C. of A. Much work was performed on the second and third aircraft while the prototype was being tested, to reduce the gap between prototype flight and the time when succeeding aircraft were ready to fly. The question of tooling was a major one, involving many factors. To make some progress before tools were available, five sets of all parts were made, largely by freehand methods. By careful liaison between experimental and production departments over the experimental lash-up jigging and temporary tools used for the prototype, much of this tooling could be re-arranged and quickly modified to give good production tooling. The risk of modifications could not be assessed. By proceeding with production before every single part was approved, a loss of some £350,000 had been incurred due to subsequent changes, but this was a small price to pay for the speedier delivery gained. As the number of tools required was increasing with each new design, production engineers could show—and, on the Comet, had shown—great ingenuity in introducing new methods to reduce the time required for tool manufacture. In jig and tool design, much time could be saved by intelligent co-operation between the designers and the makers; the detailed design of tools could often be performed by the latter. A further important liaison was that between the design, planning and production departments at all stages of manufacture. Mr. Povey then gave a list of the major problems (including those mentioned above) encountered during the Comet's "proto type to production" period, and emphasized the large volume of work which had to be done in this time. In conclusion, he stated "Production engineers who have the task of creating a production line of aircraft have many difficult problems to face, and it is upon their skill and ingenuity that success can be measured." The ensuing discussion brought this profound point from Mr. S. Scott-Hall: whereas his whole training had led him to look upon prototypes as end-products, he now realized his real job was to help in building numbers of aircraft. PAPERS BY T. GILBERTSON AND H. S. HOW AT SESSION III of the conference was opened, on behalf of the industry, by Mr. T. Gilbertson, M.I.Prod.E., director and general manager, Folland Aircraft, Ltd. His subject was "the impact of modifications on production." He pointed out that, although modifications were necessarily accepted by the pro duction department in the right spirit, there was need to introduce them in the most economical manner. This could be achieved by requiring the planning department to hold regular meetings in order that modifications were dealt with at once. Other observations by Mr. Gilbertson were : planned visits to other factories and Service establishments were beneficial; methods engineers should be brought in at the start of every project; at the outset, management should provide for the incor poration of later modifications; production engineers should not (Continued at foot of page 38)
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
