SOUTHERN SECTION CONFERENCE. SESSION III (contd.)

THE IMPACT OF MODIFICATIONS

ON PRODUCTIONREPORT OF DISCUSSION

Chairman : W. E. W. PETTER, C.B.E., B.A.. F.R.Ae.S.

THE CHAIRMAN said that ample material had been pro-vided for discussion and, in particular, it seemed to himthat the question of how far it was desirable to have aseparate department for putting in modifications, to whichMr. Gilbertson had referred, was one which could usefullybe discussed.

The batching of modifications, as another means of re-ducing the production load consequent on modifications,as mentioned by Mr. Howat, might also be examined.

The Designer's ResponsibilityIt seemed to the Chairman that in this matter of modifi-

cations the designer had a position of very great responsi-bility, probably equal to his responsibility in producing theaeroplane at all. There were two kinds of modification,the first being the development modification which keptthe good aeroplane young, the kind of modification whichkept the Mosquito and its engine in being with severaltypes each year for several years. That was one problemwhich, it would be generally recognised, was essential tosolve, and perhaps some of the Production Engineers presentwould like to comment on the best way of introducingthese new types without too much interference with theexisting flow of production.

Secondly, there were the detailed modifications whichmight arise from all sorts of causes and which might ormight not be dealt with in the same sort of way. In thismatter, the designer had a very great responsibility, whichhe did not always recognise.

The Chairman thought that, in general, the structuralmodification was unnecessary; it should have been foreseen.He was not talking about such new and unknown fields asthey were now beginning to enter when considering thefatigue life of aircraft structures in civil aircraft. Whenone left the beaten track, modifications would always benecessary; but the kind of modification arising out of faultyload distribution, or detailed design, should almost alwayshave been susceptible to stress analysis and intelligenttesting and should not require modification afterwards.

In aerodynamics the problem was more difficult, butmore intelligent, and earlier, flight testing, on moremachines, should avoid many modifications. So far asinstallations in the aeroplane were concerned, while it wasnot possible to avoid the new radio and radar sets andother bright ideas which the operational side brought for-ward, a great deal could be done to make the initialinstallation first-class by good mock-up work. It helpedthe designer in many ways and it brought in the shoppeople; they had not time to look at large numbers ofdrawings, but they could understand a mock-up. In thatdirection, more could be done to forestall modifications by,for instance, intelligent installation of equipment, controls,etc.

Aiming at PerfectionIt might be said that this was increasing the load on the

designer, but in the Chairman's opinion it was not worthattempting to put an aircraft into large-scale productionunless it was nearly perfect. The money spent on the

production of aeroplanes was enormous when comparedwith the amount which went into design. The extra effortrequired to achieve something as near perfection as possiblein the design undertaken was a thousand n'mes worthwhile.That was a matter on which the Ministry mus«; help, andit must make the conditions sufficiently attractive for a firmto concentrate on aiming at perfection rather than encour-aging a multiplicity of hurried designs.

Designing for ModificationsThe designer could do a great deal by intelligently

designing for modifications. It was extraordinary what adifference there could be between the method adopted bya junior draughtsman and one which had been carefullyconsidered. There were countless examples of intelligence indesign enormously helping the people in the shop to mini-mise the disturbance when a modification was necessary.

Another way in which the designer must help was that,without pretending to wear an Air Force cap, he must bean amateur Air Staff strategist himself and make the custo-mer establish a cast iron case for the modification He mustgo into the matter in a tactful but thorough manner,before admitting that the modification should be introducedto delay and, perhaps, to some degree spoil—or else greatlyimprove—his • beautiful aeroplane.

Importance of ClarityFinally, the designer must try to make his object in

carrying out the modification, and the manner in which itwas going to be carried out, quite clear. One knew fromexperience of oneself that the standard of intelligence inthis world was not very high, and people were very busy.In introducing a modification to the shops, a really well-written modification sheet showing what one was doing,how one intended to do it, when one was going to do itand how one wanted it carried out, would go a long wayto ease the path for the all-too-few skilled men who had todo the job.

MR. W. S. HOLLYHOCK (Chief Production Draughtsman,Hawker Aircraft, Ltd.), dealing with the subject of batch-ing, said that he could speak only with regard to smallmilitary aircraft, and his views were not generally shared.First, he thought that the prototype was in itself not aproduction machine. It was essentially a machine designedfor high performance. After the prototype had flown, hefelt that the best method of introducing production wasto have a batch of pre-production aircraft. These could bebuilt with rough tools, and could be subject to the changeswhich were bound to be asked for during the early produc-tion life. In that way, many of the modifications whicharose could be cleared within the first 10/15 aircraft, andthus leave the main production clear of modifications,except for those changes which were inevitable.

If the job had been planned satisfactorily, after theprototype had been built a great deal would be learned,and in the following year or so much more would belearned. During that time, the position would be clarifiedand changes could be introduced with less difficulty and

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with less interruption to the programme, than at a subse-quent date.

With regard to the subsequent introduction ot modifica-tions, Mr. Hollyhock felt that batching was a good thingfor all modifications except those of a safety nature. Heknew that the Service did not like batching, because itmeant on the face of it delaying the introduction of certainmodifications. In the long run, however, he felt thai itwas quicker, because there was not a continuous interrup-tion of flow for the introduction of modifications whichrequired new material and perhaps six months fabricationperiod for castings, forgings, and so on.

Generally speaking, a batch of something like 20 per cent,of the current order was a useful figure at which to aim,not necessarily 50 aircraft, as had been suggested, thoughfor a big order that would be satisfactory. With an orderfor 100, to treat 20 as a batch would be a satisfactory wayof introducing modifications without unduly embarrassingthe production side.

MK. R. E. MILLS (Senior Designer, Bristol Aeroplane Co.Ltd.), said that in helicopter work they had run into anew trouble with modifications. On helicopters, the struc-ture was only one part of the aircraft, and the mechanicalside, which in his Company was dealt with by the AirframeDepartment and not by the Engine Division, was anotherside. For structure work the trial installation proceduregave a very useful breathing space, because the results wereoften a foregone conclusion in the sense that one knew whatone was going to put in, and that it would be all right.

On the mechanical side, however, the trial installationwas a different matter and it was very much more difficultto forecast that some new design or modification was goingto work until it had actually been tried. It was found thatthere had to be modifications to the modifications, whichnearly always took place during the trial installation period.

Mr. Mills said his Company found that they were run-ning into considerable trouble with this, because on themechanical side there were usually greater productiondifficulties. It might be necessary to produce new castings,to jig up more and do more accurate machining work, sothat the trial installation did notigiye that breathing spacewhich was usually obtained on the structural side. Hethought that there should be some alteration to the modifi-cation procedure to cover that difficulty.

MR. H. S. HOWAT, replying to Mr. Hollyhock, said thatit was a realistic approach to try to have a small batch ofaircraft in which modifications could be introducedwhere they were known but, of course, they were not allknown until the aeroplane got into service. Moreover, itwas not always possible to adopt that procedure, becausethere was very great pressure from the Services to have theaeroplane quickly. It was necessary to compromise and,in Mr. Howat's opinion, the best method was to put in eachindividual modification as'soon as it could be introduced.

With regard to helicopters, as with aircraft, there werealways modifications to modifications. There was no greatbody of experience on helicopters and it was bound to takelonger to get the modifications right.

MR. A. I. MORGAN (Technical Officer (Engineering)),commenting on Mr. Howat's statement regarding increasedsupervision of detail design by Drawing Office staff, saidhe presumed that it was generally accepted that manysubsequent modifications arose from errors in the DrawingOffice. He had recently visited the principal aircraft firmsin the Conference area to investigate the. demand fordraughtsmen, and the diversity of methods of employingdraughtsmen in Drawing Offices had become apparent tohim.

His general impression had been that Drawing Offices ingeneral were overburdened with the junior or intermediatedraughtsman, who could not be trusted to take a design tofinality. Such men required considerable supervision andchecking, and it might mean taking senior men off aresponsible project for the purpose. Moreover, despiteextensive and exhaustive checking, bad designs did getthrough. It was known that this was largely due to thegreat influx of draughtsmen into the industry towards the

end of the War, when almost anyone who could use apencil or a square had been drafted into a Drawing Office.Some had had no opportunity to get practical workshoptraining.

He wondered whether the aircraft industry could intro-duce a system, in easy stages, whereby .some of the so-called senior draughtsmen could be induced to take re-fresher courses in the workshop. There would no doubt bea great deal of opposition to such a ;cheme, because itseemed to be regarded as undignified for draughtsmen togo back to the shop, but it would be interesting to haveviews on whether such a scheme could be put into opera-tion.

MR. V. H. WILTON (Assistant Director, Aircraft Produc-tion, Aircraft Supplies Division, Ministry of Supply),speaking as one of those who had to provide an " alibi "when a firm did not meet the programme, referred totho-e modifications which resulted from the specificationissued not being met. He would urge ihe Design Officesto consider carefully the specification requirements, andthe development and pre-production engineers to comeforward rapidly with the necessary plans for testing andmeeting them.

He had in mind, in smaller aircraft, such things aspressurisation and cabin hoods. Programmes were set for18 months or two years ahead, and as the delivery timeapproached, it was often found that the aeroplane woutdnot stand up to pressurisation and also that there was somefault in the hood, apart from any change in operationalrequirements.

Mr. Hollyhock had referred to the introduction of pre-production aircraft. Would he expect a break in deliveryfollowing the delivery of, say 20 aircraft from pre-produc-tion, before delivering the first true production aircraft ?That point was of interest, because if one were toolingfor large-scale production, the tools must be ready whenthe first production aircraft was put out. If, while pro-ducing the first 20, these aircraft were being subjected tomodifications, the tools would be affected, and the questionarose of whether it v\ould be possible to embody the modifi-cations in the first true production aircraft, without causinga break in delivery. *

MR. HOLLYHOCK explained that his object in having apre-production quantity was to afford a breathing-spacein which to change the tools to the altered requirements,rather than having the whole flow through the productionshops upset. One could go on with the aircraft which werebeing built under more or less freehand methods at thesame time as one was preparing and lining up the toolprogramme for the full production.

MR. H. G. PARKER (Assistant Chief Engineer, ShortBros. & Harland Ltd.), replying to Mr. Morgan, mentionedthat at a recent lecture at the Royal Aeronautical Societyit had been stated that one aircraft firm, during a recentslack period, had returned quite a number of their seniordesign staff to the works for a refresher course, with verygood results.

On the question of having more senior draughtsmen fordetail design, that would apply also to maintenance. Designfor maintenance had been discussed at similar Conferencesin the past. In both cases, maintenance and detail design,he thought that it would pay to have senior draughtsmen—it might be said that they could not be spared, but hedid not accept that—in every office, who had no responsi-bility for a particular aeroplane, or to anybody but theChief Designer or Chief Engineer, but whose sole objectwas to act as miniature consultants—dabbling in everythingin the office which concerned bad detail design and badmaintenance.

Reference had been made the previous day to the needfor education. There was need not only for education, butfor continual re-education, for every junior that came intothe office. He had found, over a number of years, that assoon as a junior became a senior he was so busy with hisstructural design that he forgot all about maintenance, andhis juniors had again to be re-educated. They had foundsuch re-education very advantageous over the last few years,

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and he himself had a job of that kind at the moment,being free to dabble anywhere in the Drawing Office, andtake up anything which he found was detrimental to main-tenance or was in the nature of bad detail design.

There was another matter which concerned the samepoint, from a different angle. He had been concerned fora number of years at the perpetual friction which seemedto exist between production and design in the matter ofmodifications. He had always felt that it was not necessary.Over their last three prototypes, he had had a carefulanalysis taken of all the query forms which had arisen fromthe shop floor up to the time of the first flight. These, ofcourse, were all defects on drawings and did not concernsubsequent modifications. He did not speak in justificationof the Design Office, but to point out the real truth of thematter. Of the queries raised up to the first flight, theaverage correctable on the drawings—points such asdimensions missing or stupid mistakes—was in the regionof 75 per cent., affecting 10—15 per cent, of the drawings.The rest of the queries arose from bad scheduling,alternative materials because certain materials were not instock, and so on. In the end, as everyone associated withthe Drawing Office would agree, if one checked the finalreturns for modification work on a prototype arising fromthese defects and queries, it did not amount to more thanabout 3 per cent, of Drawing Office time.

So far as detail design was concerned—not the bestdesign of a piece of machinery, but a design which wouldat least come together—the Drawing Office was thus about97 per cent, efficient He knew that it did not diminishthe problem of the production side, for by the time theDrawing Office had finished their 3 per cent, of time spentthere was this considerable number—10/15 per cent.—ofdrawings which had been re-issued from this cause alone,with consequent paper work. They would like to do awaywith that, but had so far been unsuccessful.

CAPTAIN (E) C. W. JONES, R.N. (Director, Military Air-craft Research and Development (R.N.), Ministry ofSupply), said that he spoke with some trepidation, in thefirst place because he was a serving naval officer, secondlybecause he was in the design branch of the Ministry ofSupply, and thirdly he had only had the advantages of acheap Service education ! He knew that at least two ofthose qualifications, from what he had heard the previousday, were not entirely acceptable to the ProductionEngineer.

Mr. Hollyhock had mentioned pre-production aircraft,and had been supported by Mr. Wilton. There had beenunder discussion for some time a proposal on those lines.The key to the problem of modifications, and to some ofthe problems which had been mentioned the previous day,lay in the period of five years. If this period could bereduced very considerably it would no doubt reduce theincidence of modifications, but it would still leave the factthat modifications were required when an aircraft firstwent into service and also during its development period.

If the Services could persuade the Treasury to, order anaircraft in a small batch from the moment the staff require-ment was agreed by the Ministry of Supply, and if thatbatch went into service in one or two squadrons, and onethen started to think about a second series of aircraft,-which would embody modifications learnt from this smallnumber, which had gone directly into service, somethingmight be done to give effect to Mr. Hollyhock's proposal.It involved the problem of a break in production, to whichreference had already been made, but personally he thoughtthat it was worth consideration and, in fact, it was actuallywhat was done to a certain extent.

There was also the question of having modificationcentres. It had not been stated whether those should beService-manned or civil-manned. He thought that eitherwould work very well. That had been tried, but they hadalways come up against the problem that each modificationwas a subject for consideration on its own. It was thecircumstances of the time which would dictate whether itwas better to embody it in the modification centre orin the works. During the War, on several occasions inaircraft repair yards they had this modification centretechnique. For those who did not know what aircraft

Mr. C. E. Fielding (left) and Mr. H. S. Howat (right) witha visitor to the Conference during an intermission.

repair yards were, he would explain that one of the reasonsfor their inception was that they provided a very flexiblemedium between inflexible industry and the Service. Italways took industry six months to tool up before it coulddo anything, whereas, at great expense and perhaps in-efficiently, it was possible to get things done in the repairyard until industry could " get cracking ".

Mr. Howat had made the point that Service people didnot treat the aircraft very well. Captain Jones was pre-pared to lay it down as an axiom that anything whichrequired skilled maintenance was bad engineering. It mustbe realised that in a Service, particularly when war began,there was not a vast number of highly-skilled people to callupon; one had to train people very quickly and facecolossal expansion. If the aircraft industry could not makeaircraft to fit the normal individual who was called amechanic when he went into the Service, he was certainthat the Service could not make mechanics to fit theiraircraft.

MR. A. VINES (Production Manager, Fairey AviationCo. Ltd.), said that Captain Jones appeared to contendthat naval repair yards were highly flexible, while in theaircraft industry it was six months before anythinghappened, What actually took place was, speaking fromthe standpoint of an aircraft firm that knew a good dealabout the Navy, that the naval repair station got an aero-plane and then worried the firm for the parts needed toincorporate the modification. In fact, the firm carried therepair section.

Mr. Vines suggested that it would be easier to fly air-craft to the factories concerned for occasional overhaul andservice. By doing that in a regular sequence, it would bepossible to bring the aeroplane up to date more quicklyand easily than by borrowing a machine from a squadronand giving it back on a certain day, with or withoutmodifications. It would be necessary to order more aero-planes to have a few up one's sleeve for modification.

A point to be borne in mind was that 90% of themodifications which arose were due to bad detail design.He thought that a prototype should be ordered which thepeople who were going to use it would fly, and keep on flying,not keep grounding it for minor development modifications.In that way many of the modifications required would bepicked up earlier. The engine and propeller were typetested for endurance, but not the aeroplane.

There was no detail design office which could be rightfirst time on every detail, and obviously there were goingto be modifications on such a complicated structure if itwere not tested.

To incorporate modifications, the simplest way was fora component to be built in one shop. Instead of havingdetail and sub-assembly shops, all the sub-assemblies weremade in the same shop as the final assembly, and then thesupervision of that shop had a better chance to organise

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the labour and incorporate modifications more intelligently.Mr. Vines' Company had found that helpful from thefactory organisation point of view in the past. They hadsucceeded in making interchangeable sub-assemblies withinterchangeable rivet holes, by means of three-dimensionallofting and envelope tooling which helped with modifica-tions.

If, however, one wanted to incorporate a modificationwith a forging, it was necessary to wait five or six monthsto get the forging delivered. When in America during thewar, Mr. Vines had visited a firm which had a battery ofvertical copy milling machines to produce machined forgingsout of blocks from wooden patterns: instead of waiting forthe forgers to deliver, they carried a large stock of blocksfor the first batches. If the light alloy forging industryhad a battery of machines of this type, they could supplyten to twenty sets of rough-cut forgings from billets fullyheat treated, provided the aircraft firm supplied a woodenpattern, which would be a great advantage for incorporatingmodifications and starting new types quickly.

CAPTAIN JONES disagreed entirely with this view, andsaid he had in mind the type of modification which hadto be carried out in a hurry because it was urgentlyneeded to meet some Service requirement.

A MEMBER said that Mr. Gilbertson had pointed outthat the machinery available in this country was quiteinsufficient, and Mr. Walker had stated earlier that it wasvery often used most inefficiently. It would be interestingto learn what, in Mr. Gilbertson's view, the solution ofthis question was. Clearly more machinery was needed, andhe wondered whether the right answer was that we shouldin this country, with our limited resources, start specificpurpose sub-contractors, instead of having sub-contractorsas they were now, taking over overflows in every direction.

It might be better if, instead of the present arrangement,there was, say, one sub-contractor who specialised inmachining stringers from the solid sheet. The Ministrywould encourage that firm to do that sort of work and seethat they had the machine tools needed.

MR. T. GILBERTSON, before dealing with the question ofmachinery, referred to the remarks which had been madeabout the number of machines which could be ordered andsaid that there seemed to be a feeling that it would be goodpolicy to restrict the numbers ordered at the beginning, inorder to get some idea of how things were going to turnout. Personally, he was opposed to that view; in hisopinion, a bold policy was essential if the ProductionEngineer was to be satisfied and if the factory was to be runin an economic manner. His own Company had beentroubled by having the shop laid out and labour and toolingprepared for certain marks of aircraft and then havinga major modification thrown at them, but two years ago hehad pointed out the dangers of not ordering sufficient of theearlier mark numbers. The merits or demerits of thetype he was not competent to speak about, but it was veryimportant that everyone concerned should get together tosee the impact which was likely to result fromany delaying tactics in the hope of saving money andgetting a better aeroplane. One might get a better aero-plane, but one would get only half as many of them asone would like to have.

With that arrangement, one could not put the people ormachine tools on the job, or go to another contractor foralternative work. In other words, the programme wasaffected, and that demoralised labour and upset the rhythm,which it was very important to maintain.

The first questioner that morning had made a soundpoint, but he thought that it had been covered by Mr.Petter, and also by Mr. Walker the previous day. Itseemed to have been already established by people such asHawker's that it was important to have a component mock-up, by which he meant an actual mock-up though nota complete aircraft, but a wing, a fuselage and so on. Thatcould be done concurrently with the production of theexperimental machine. He endorsed Mr. Petter's remarkthat the Production Engineer and the designer could get a

3-dimensional outlook by seeing the job instead of thedrawings, and it was certainly possible to speed up theeventual production rate as a consequence of making thatarrangement.

To play safe did not pay, but it was a big fault of theBritish people. They should be bolder, and there was aneed for more boldness in the design and supply of machinetools, although it was not necessary to spend a quarterof a million pounds on some immense machine tool. Hedeplored the attitude of the British machine tool industry.It was not keeping up with the needs of the aircraftindustry. All aircraft firms had to go to the Continent andto America to get machine tools which they knew could bemade just as well and at one-third of the cost in thiscountry. He did not see the sense of allowing Britishmachine tools to be exported at the expense of the British-aircraft industry.

He would ask the Ministry of Supply to persuade themachine tool industry to take a more definite interest inthese specialised machine tools. All too often the aircraftindustry were told that if they wanted only one off, thematter did not interest the machine tool industry. Thequantity was a discouragement, but it was necessary for theGovernment to subsidise and support and encourage thesupply of specialised machine tools of an up-to-date type,tracer-controlled and electronically-controlled.

WING COMMANDER L. P. GIBSON (Air Ministry) referredto the sum of £M6£ which had been mentioned asthe cost of modification for the Service aircraft. He askedwhether that sum included the money spent on the Designand Drawing Office effort to produce modifications which,through lack of man-power both in industry and in theService, never found their way into Service aircraft atall.

MR. HOVVAT replied in the affirmative. The total designeffort, he said, was less than £MI out of £M6£. It didnot include the modifications which did not find their wayinto Service aircraft, but he did not think that that repre-sented an appreciable figure.

MR. L. E. BUNNETT (Assistant Director, Ministry of Supply)said he would like to dispel any impression that modifica-tions did not cost money. He was afraid that Mr. Howatmight unwittingly have given that impression by sayingthat an examination of the increased production costs dueto modifications, when compared with complete aircraft,indicated that the additional effort required was about 1 %.

Later, Mr. Howat stated that one firm which produceda new mark of an existing type each year, for several years,estimated that on the introduction of the new mark, theman hours to produce the whole aircraft were increasedby 10%. That might be the actual measure of the costof the parts required and called for on the modificationsheets, but the dislocation of the production flow wasenormous.

He could say without hesitation that if it were possibleto make aeroplanes without any modifications at all, itwould halve their cost. It was very important to getmodifications controlled and cut down because, as Mr. Lowhad stated the previous day, delivery was the essence of thepresent problem, and if more modifications were put in,it would take much longer to produce the aeroplanes.

Professor Richards had suggested that specialised sub-contracting could be introduced. It was desirable to pointout that dispersal had saved this country during the lateWar and if the whole manufacture of, say, ribs were put inone factory and that factory were hit by an atom bomb, itwould be the end of aircraft production in Britain.

MR. A. E. WOODWARD-NUTT (Principal Director of Re-search and Development (Aircraft) Ministry of Supply), onthe question of early user experience with aircraft, said thatin what are usually called " official circles " that idea wasaccepted, and it so happened that it was being tried inthree different ways, according to the three uses of theaircraft. For naval aircraft, in one specific case the Ministryof Supply had ordered an additional prototype purely to

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