Category Archimedes

The evolution of aerodynamics in the twentieth-century – was it engineering or science? In retrospect, this should now appear to be a rather naive question. The answer is both, and more. When the academic community embraced the idea of powered flight at the turn of the century, they found a plethora of questions about aerodynamics ripe for science to answer. Of course, airplanes were flying, and flying somewhat successfully, long before the answers came. It is this aspect that prompted the aviation historian Richard K. Smith to state: “The airplane did more for science than science ever did for the airplane.”12 Today, modem aerodynamics is dominated by the computer; the techniques of computational fluid dynamics allow us to solve complex aerodynamic flowfields heretofore dreamed impossible. And applications are being made to the whole spectrum of flight, from low-speed to hypersonic vehicles. However, it is clear that the way we have arrived at our current understanding of aerodynamics, and our ability to predict aerodynamic phenomena, is through an intellectual process that blended the disciplines of science, engineering science, and pure engineering. Perhaps, within the scope of the history of technology, aerodynamics is one of the best examples of such blending.

These conclusions about the MAA raise one final irony. The criteria used by the Justice Department in 1972 to rationalize breaking up the Manufacturers Aircraft Association soon proved to be inappropriate. The Antitrust Division had identified nine restrictions that it believed should be applied to patent licensing. Restriction number two forbade a patentee from requiring a licensee to assign to the patentee any subsequently acquired patents.94 The cross-licensing agreement did this, and it was on this basis that the Justice Department filed against the MAA. By 1973, however, the Justice Department began to appreciate that these restrictions were, in the words of the Chief of the Intellectual Property Section of the Antitrust Division, “economically counterproductive in that [they] discouraged investment in R&D and discouraged efficient licensing of patents.”95 This revelation did not, however, stop the wheels set in motion in the U. S. District Court in New York. The same Justice Department that endorsed the cross-licensing agreement in 1917 brought it to a close in 1975. The agreement probably did restrain trade in 1917; it probably did not in 1975. The Justice Department got it wrong both times.

This essay studies engineering exchange within the context of American aircraft manufacture during World War II. At issue is the nature of engineering knowledge within the manufacturing firm and how this is transferred among firms. While technology normally finds its way between competing firms (often surreptitiously), this period is interesting in that companies broadly encouraged technology transfer. Wartime mobilization brought both pressures and opportunities for firms to establish cooperative links, eventually leading to the establishment of product – oriented and industry-wide cooperative structures.1

The methods of technology transfer and the kinds of information sought teach us much about the nature of engineering knowledge and the process of exchange. What becomes obvious in this history is that traditions of practice unique to each manufacturer obstructed technology transfer. The difficulty of exchanging engineering knowledge had less to do with legal and proprietary boundaries than it did with technological cultures, a firm’s unique methods of designing and producing aircraft. In some cases these practices were so different that even when firms attempted to manufacture identical products, they were simply unable. While individual components of a manufacturing system might be adopted across firms, production systems themselves remained highly localized and the result of idiosyncratic philosophies. An examination of the design and manufacturing process reveals that design information was not only lost or changed as it proceeded from the drawing board to the factory floor, but that it continued to be created along the way. While engineers might have believed that all design information began with them and could be transmitted completely through drawings, the imposition of different tooling and production groups from outside companies exposed the degree to which engineers were also imbued with specific traditions of production.2

Within these constraints (many of them initially unknown to the manufacturers themselves), firms established varied means for communicating technological knowledge. Before mobilization, technological information normally found its way through engineering and trade journals, scientific and technical societies, and user- producer relationships.3 This is exemplified through the story of the Guerin process, a metal stamping technology that began at Douglas Aircraft and diffused across the industry through journals and machine tool suppliers. With the advent of cooperative wartime structures, the ease, urgency, and rapidity of information flow increased dramatically. Manufacturers established methods for exchange, including tooling transfer, central data repositories, committees, publications,

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inter-plant visits and standards-setting bodies. While conclusions about the success or failure of this transfer are elusive, the quantity and persistence of exchange throughout the war testify to some measure of achievement. In addition, the types of material exchanged, from explicit design data to more tacit shop-floor information, as well as the mediums of exchange, suggest a diversity of engineering knowledge and reaffirm the assertion that engineering knowledge was embedded within a firm’s culture.4

A brief look at the historical treatment of engineering knowledge discloses two recurring strands. The first is the importance of design, and the second is a design trajectory that posits a movement from idea to finished product. Originally, the notion of engineering knowledge emanated in part from a desire to reject the applied-science definition of technology, and to characterize engineering as a distinct and valued branch of knowledge. By asserting that technology extended beyond material artifacts, engineering could be placed on a par with science rather than serve as a translator of theory into artifact. More important to historians of technology was the function of design in what was considered to be a knowledge­generating activity or process. Engineering knowledge was not simply distinct from scientific knowledge in its content, but also embraced creativity. This was original knowledge, not reconstituted theory. In design and creativity, engineers could lay claim to the kind of prestige normally reserved for scientists, while some historians underscored engineering’s relation to the arts. Edwin Layton’s oft-cited 1974 article “Technology as Knowledge” emphasized the role of design as an ideal within American engineering and as a distinguishing characteristic from science. Furthermore, he described a trajectory that began with an idea (rather than a scientific theory) and eventually culminated in a product. He writes:

The first states of design involve a conception in a person’s mind which, by degrees, is translated into a detailed plan or design. But it is only in the last stages, in drafting the blueprints, that design can be reduced to technique. And it is still later that design is manifested in tools and things made…. We may view technology as a spectrum, with ideas at one end and techniques and things at the other, with design as a middle term. Technological ideas must be translated into designs. These in turn must be implemented by techniques and tools to produce things.

Similarly, Walter Vincenti’s work What Engineers Know and How They Know It also emphasizes design, and characterizes the process as a movement from the abstract to the physical.5

Both Layton and Vincenti were well aware that while design was an important quality of engineering knowledge, it was not everything. Furthermore, they understood that the process was much more complex than the idealized and sometimes reductionist versions they portrayed.6 This is especially so in the case of the manufacturing firm.

As an organization that generates large quantities of engineering knowledge, the firm cannot be treated in the same way as an individual engineer. Outside of a small number of gifted individuals who have designed both the product and the production process, these activities are normally carried out by different communities of engineers.7

It should be evident that the design trajectory, the movement from an idea through increasingly material stages, does not fit neatly into the factory. Production, as a stage in this process, is not simply downstream from the idea stage. It is itself the operational stage of a different design process. Layton appreciated this relationship, stating:

The designs for the final products of technology do not exist in isolation. They are intimately asso­ciated with production and management, which, as Frederick W. Taylor insisted, also require design. The innovations of Eli Whitney and Henry Ford were less in the final products, whether muskets or automobiles, than in the design of systems of production and tooling.8

While we may idealize the creation of a product as a linear process, in practice it is much more circular, since production techniques feed back and change the original design. Vincenti alluded to this in his study of flush-riveting, which he termed “production-centered.”9

Changing our perspective to incorporate all the engineering activities of a manufacturing firm serves to eliminate some of the strict distinctions between design, production, and operation, as well as notions that this is a linear process. In reality a manufacturer is usually doing all three; it does not necessarily follow that one begins with design, and moves on down the line to production and operation. Rather, in a company practicing design and production, there is a negotiation between different groups of engineers and managers. The aeronautical engineers are but one group, and they may well conceive of the process as linear. But the tooling engineers will have a different understanding, since they are designing a process in which the product is not an aircraft, but a quantity and quality of aircraft under certain limitations of machinery, material, and labor.10 Figure 1 illustrates this relationship in a simplistic fashion. The actual circumstance would incorporate far more communities of engineers (aerodynamics, structural, systems, weight, etc.), a

web of feedback loops, as well as inputs from labor, materials, and machinery. The two dimensions given here are sufficient to make the point that what an aircraft factory does is a negotiated result of multiple design models.

As products and production processes grow more complex, an intermediate group appears, namely production engineers, who mediate between product and process designs. The World War II period saw a blurring between design and production as aircraft came to be “designed for production.” The history of Ford’s Willow Run facility reveals how an aircraft, the Consolidated B-24, was redesigned, not around performance specifications but around manufacturing specifications.

The idealized design trajectory itself exists only in a extremely contorted fashion within the manufacturing firm. For example, tooling engineers begin with a product and work backward to design a process. And while they certainly operate under a set of fundamental design concepts, it is more appropriate to discuss traditions of practice. A tooling engineer, confronted with a novel product, is going to have at his or her disposal a range of well-known production techniques that can be applied to create a production process. He or she does not necessarily return to abstract fundamental concepts each time a new production process is to be made. In the end, it must be concluded that depending on what technology is under consideration, there may be a whole range of models for the description of engineering knowledge. Layton’s warning in this regard is appropriate, “We need not assume that technological thought is a single monolithic whole or that it can be uniquely characterized in any single formula.”11

Comprehending the nature of engineering knowledge within a manufacturing establishment is difficult, not only because much of it is tacit or proprietary, but also because some of it involves seemingly non-technical issues. Engineering practice in a company is not only a body of collected knowledge; it is part of a culture or tradition of practice. Just as companies may have distinct business cultures with their own internal momentum, so may firms have distinct engineering cultures. These traditions of practice count, and they are embedded not only in the engineers, but in the technicians, the workers, the managers, and even the equipment. Engineering within a large company is far richer than traditional notions of engineering knowledge allow. When it comes to understanding the nature of engineering exchange among companies, many non-technical issues impinge on the flow of information. As will become clear, ideological and practical differences regarding the optimal form of manufacture resulted in three different systems for the production of the same aircraft. Transferring the Boeing aircraft company’s system to the Douglas and Vega aircraft companies would have involved far more than the simple exchange of technical information; it would have bordered on the wholesale adoption of a tradition of practice.

I

All the papers in this collection are highly accomplished exercises in the history of technology but, of course, they represent history of somewhat different kinds. For example, they assume different positions along the so-called “internal-external” dimension. Profs. Smith and Mindell’s admirably detailed history of the turbo fan engine largely, but not wholly, falls into the “internal” category, as do the authoritative accounts by Prof. Vincenti of work done in supersonic wind tunnels, and Prof. Suppe on the instrumentation used in test flying. Of a more “external” character are papers dealing with the economic, institutional, and legal setting of aeronautical activity, such as Profs. Crouch and Roland’s discussion of patents or Prof. Douglas’ account of the different professional inputs to airport design. Again on the “externalist” side we have Prof. Jakab’s account of the hypocrisy and profiteering surrounding the emergence of McCook Field.

Apart from the “internal – external” divide we also have other kinds of variation. Some papers are clearly more descriptive, while some are more explanatory. I think it is true to say, however, that most contributors have chosen to keep a low profile when it comes to questions of methodology or theory. This is a wise strategy. Concrete examples often speak louder than explicit theorizing. Readers can put their own gloss on the material and see for themselves points of contact with other ideas. Nevertheless it is in the area of theory and method where I may have a role to play. I am not an historian of technology, indeed I am not an historian at all, and I have no expertise in aerodynamics. My comments will all be from the standpoint of sociology. I shall focus on what I take to be the more significant sociological themes that are explicit, or implicit, in what has been said. I shall try to suggest ways in which sociological considerations might be brought into the discussion or where they might help in taking the analysis further. Adopting a sociological approach biases me towards what I have called the “external” end of the scale, but there are some points of contact with the more technical, “internal” discussions, and I shall do my best to indicate these. Here I shall be struggling somewhat, but for me these points of contact between the social and the technical represent the greatest challenge, and the greatest interest, of the whole exercise.

II

Let me begin with Prof. Galison’s paper. His claim, and I think he makes it convincingly, is that aircraft accident reports are beset by an unavoidable

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indeterminacy. Investigators confront an enormously complicated web of circumstances and actions. How is this manifest complexity to be handled? There are two possible directions in which to go. One direction is to narrow down the explanation of the accident on to one or more particulars and highlight these as the cause. We will then hear about the Captain who chose to take-off in bad weather, or the co-pilot who was not assertive enough to over-rule him, or the quality control inspector who, years before, let pass a minute metallurgical flaw. The other direction leads to a broader view, embracing a wide range of facts which can all be found to have played a contributory role in the accident. Had the de-icing been done properly? Was the company code of practice wrong in discouraging the use of full – throttle? What is it that sets the style and tone of group interaction in the cockpit? Who designed the three hydraulic systems that could be disabled by one improbable but logically possible event? Accident reports, he argues, tend to oscillate between specific causes and the broad range of other relevant particulars.

Prof. Galison has put his finger on a logical point similar in structure to that made famous by the physicist Pierre Duhem in his Aim and Structure of Physical Theory (1914). No hypothesis can be tested in isolation, said Duhem. Every test depends on numerous background assumptions or auxiliary hypotheses, e. g. about how the test apparatus works, about the purity of materials used, and about the screening of the experiment. When a prediction goes wrong we therefore have a choice about where to lay the blame. We can, logically, either blame the hypothesis under test, or some feature, specified or unspecified, of the background knowledge. Prof. Galison is saying the same thing in a different context. No causal explanations can be given in isolation. Whether we realize it or not, the holistic character of understanding always gives us choice.

How are those in search of causes to make such choices? Prof. Galison tells us not to think in terms of absolute rights or wrongs in the exercise of this logical freedom. The unavoidable fact is that there are different “scales” on which to work. This, “undermines any attempt to fix a single scale as the single ‘right’ position from which to understand the history of these occurrences” (p.38). What, then, in practice inclines the accident report writer to settle on one or another strategy for sifting the facts and identifying a cause? Legal, economic and moral pressure, we are told, has tended to favour the sharp focus. This has the advantage that it offers a clear way to allocate responsibility: this person or that act was responsible; this defect, or that mechanical system, was the cause. The utility of the strategy is clear. Individuals can be shamed or punished; and a component can be replaced. Now, we may be encouraged to feel, the matter is closed and all is safe again.

Is this a universal strategy rooted in some common feature of human understanding, or near universal social need? Do accident reports from, say, India and China, have the same character as those from France and America? Or are some cultures more holistic and fatalistic and others more individualistic and litigious? It would be a fascinating, though enormous, undertaking to answer a comparative question of this kind. Prof. Galison gives us some intriguing hints to be going on with. In his experience there is not much difference between, say, an Indian and an

American report. What stand out strongly are not broad cultural differences but sharp conflicts of a more local kind. While the National Transportation Safety Board blames a dead pilot, authoritative and experienced pilots dismiss the report as pedantic and unrealistic. While official American investigators point to the questionable behavior of the control system of a French built aircraft under icy conditions, the equally official French investigators point the finger at the crew who ventured into the bad weather. Prof Galison speaks here of the “desires” of industry, of the “stake” of pilots, and of the “investment” of government regulators, as well as economic “pressures”. All of these locutions can be brought under the one simple rubric of ‘interests’. The phenomenon, as it has been described, is structured, strongly and in detail, by social interests. Let me state the underlying methodology of Prof. Galison’s paper clearly and boldly. It is relativist, because it denies any absolute right, and depends on what is sometimes called an ‘interest model’. As we shall see, these challenging themes weave their way through the rest of the book as well, and inform much that is said by the other contributors.

Ill

A number of papers take up a comparative stance – perhaps the most explicit being Prof. Crouch’s discussion of the differential enthusiasm with which governments encouraged aviation in Europe as compared to the United States. It wasn’t the Wright brother’s insistence on taking out patents that held back American aviation, it was lack of government awareness and involvement. Prof. Roland takes up the story of patents to show how the earlier shortcomings were later dramatically repaired. Once the government had got the message, expedient ways were found for circumventing legal issues. One of the themes of Prof. Roland’s paper is that of a culture of design, craft-skill and engineering expertise. His point is that if anything inhibited the flow of information and expertise it wasn’t patents, it was the localized character of engineering practices and the desire to keep successful techniques away from the gaze of competitors. So significant was this local character of engineering knowledge that when different firms came to produce aircraft or components according to the same specifications, they still turned out subtly different objects. Prof. Ferguson gives a stunning and well-documented example of this. He looks at the wartime collaboration of Boeing, Douglas and Vega in producing B-17 bombers. Despite the intelligent anticipation of such problems, and a determined attempt to overcome them, these three companies could not build identical aircraft. The ‘same’ tail sections, for example, proved not to be interchangeable. The lesson, and Prof. Fergusen draws it out clearly, is that practical knowledge does not reside in abstract specifications (not even in the engineer’s blue prints.) Knowledge is the possession of groups of people at all levels in the production process. It resides locally in their shared practices. The problem of producing the same aircraft remained insurmountable as long as the three local cultures survived intact and in separation from one another. It was only overcome by removing, or significantly weakening, the group boundaries. This was done by deliberately making it possible for people to meet and interact. In effect, it needed the three groups to be made into one group.

Others tell us of similar phenomena. Profs. Smith and Mindell speak of the different engineering cultures of Pratt and Whitney, on the one hand, and General Electric, on the other. General Electric’s rapid and innovative development of the CJ 805 by-pass turbofan engine was helped by their recruitment of a number of key engineers from NACA. Again, we see that knowledge and ideas move when people move. Smith and Mindell characterize the culture of Pratt and Whitney as “conservative” – and explain how, nevertheless, contingencies conspired to ensure that its incrementally developed JT8D finally triumphed over the product of the more radical group at General Electric. Their history of the triumph of the Pratt and Whitney engine shows how different groups produce different solutions to the same problem. Add to this their discussion of the Rolls Royce Conway, and the debatable question of which was the ‘first’ by-pass engine, and we have another demonstration of the complexity of historical phenomena and the diversity of legitimate descriptions that are possible. Finally, they address the general question of why turbo-fan engines emerged when they did – some twenty five years after Whittle and Griffith had suggested the idea? The concept became interesting, they argue, because of decline in commitment to speed and speed alone as the arbiter of commercial success in civil aviation. Turbo-fans could succeed economically in the high sub-sonic realm in a way that jets could not. We are dealing with new measures of success, “measures that embody social assumptions in machinery” (p.47). This pregnant sentence once again gives an interest-bound and relativist cast to the argument.

The theme of the local engineering culture, whether it be Pratt and Whitney versus General Electric, or Boeing versus Douglas, strikes me as sociologically fascinating. And it is, of course, something calling out for comparative analysis. How many kinds of local engineering culture are there? Are there as many cultures as there are firms? Ferguson’s work suggests that there are, and that we are dealing with a very localized and sharply differentiated effect. Nevertheless, even if local cultures are all different from one another, they might still fall into classes and kinds, perhaps even a small number of kinds. If they were to fall into a small number of kinds then comparison should enable us to see the same patterns repeating themselves over and over again. This might allow us to identify the underlying causes of such cultural styles. Calling Pratt and Whitney “conservative” might tempt us to think in terms of a dichotomy, such as conservative versus radical. Other dichotomies, such as open societies versus closed societies, or Gemeinschaft versus Gessellschaft, the organic versus the mechanical, or markets versus traditions, will then suggest themselves as models. But there are other options. Why work with a dichotomy? If we follow the suggestions of the eminent anthropologist Mary Douglas we arrive at the idea that there might be, not two, but four basic kinds of engineering culture (cf. Douglas,1973,1982).

Let me explain how this rather striking conclusion can be reached. The first step is to notice that the basic options open to anyone in organising their social affairs are limited. They can attend to the boundaries around their group and find them, or try to make them, either strong or weak. They can then structure the social space within the group in a hierarchical or an egalitarian manner. If we assume that extreme, or pure cases, are more stable, or self-reinforcing, than eclectic or mixed structures, this gives us essentially a two-by-two matrix yielding four ideal types.

The same conclusion can be arrived at by another route. Think of the strategies available to us for dealing with strangers. We can embrace strangers, we can exclude them, we can ignore them, or we can assimilate them to existing statuses or roles. To embrace strangers means sustaining a weak boundary around the group, while to exclude them requires a strong inside-outside boundary. Having a pre-existing slot according to which they can be understood and their role defined means having a complex social structure already in place which is sufficiently stable to stand elaboration and growth. Responses to strangers thus etch out the pattern of boundaries around and within the group and the options, of embracing, excluding, ignoring or assimilating, generate four basic structures – arguably the same four as identified above.

The second step in Mary Douglas’s argument is to suggest that our treatment of things is, at least in part, structured by their utility for responding to people. We have seen the principle at work in the large scale in the case of the by-pass engine as a response to market conditions. But the idea can be both deepened and generalized. Perhaps our use of objects, at whatever level of detail, will always be monitored for implications about the treatment of people. Do they leave existing patterns of interaction and deference in tact, or do they subvert them? Do they provide opportunities to control others, or opportunities to evade control? Take some simple examples. A place may be deemed “dangerous” if we don’t want people to go there. Or a thing is not to be moved or changed, because it embodies the rights of some person or group, say the right of ownership or use. Or the introduction of a new practice may render existing expertise irrelevant, and hence existing experts redundant. Put these two ideas together, social interaction as the necessary vehicle and unavoidable medium for the use of things, and the limited patterns of such interactions, and we may have a basis for a simple typology of cultures or styles in the employment of natural things and processes. We may even have a basis for a typology of styles of engineering.

Whatever your reaction to this idea, I hope you will agree that we badly need intellectual resources with which to think about such difficult themes. That is why I should like to hear a lot more about the sociology of Pratt and Whitney and General Electric, and a lot more from Prof. Suppe and Prof. Vincenti about the groups with whom they worked. How strong were the boundaries between the inside and the outside of the group? Did members of the group readily work with those outside it, trading ideas and information? How hierarchical or internally structured was the inside of the group? Did people swap roles or was the division of labor clear cut? Did they eat and relax together as well as work together? Who and how many were the isolates or outcasts -1 mean: those who were considered unreliable, incompetent or downright dangerous? These are the questions that Mary Douglas wants us to ask.

They may shed light on why some parts of a design are held stable while others are changed, or why a problem may be deemed solved by one group while another treats that solution as an unsatisfying expedient.

I say that these ideas may provide the basis of a typology. There are many ways of criticizing the line of thought I have just sketched. But I would ask you not to be too critical too soon. Give the idea time to settle. It may start generating connections that are not at first obvious to you. For example, Prof. Bilstein’s account of the international heritage of American aerospace technology connects with what I have just said about responses to strangers. He is telling us about a segment of culture that was eager to embrace strangers, where ‘stranger’ here means experts and outsiders from Europe. The European input is sometimes retrospectively edited out, but in practice and despite difficulties, it was seen as a source of opportunity rather than threat.

Or consider the “ways of thinking” alluded to by Prof. Vincenti. Here too we are dealing with questions of group culture and group boundaries. His first-hand account describes the problems of understanding an aerofoil in the transonic region. Two different groups of people had reason to address this issue: those designing wings, and those who worked on propellers. Those who work on wings routinely use the categories of ‘lift’, ‘center of lift’ and ‘drag’, but this is not exactly how the designers of axial turbines and compressors think: “because the airfoil-like blades of their machines operate in close proximity to one another, [they] think of the forces on them rather differently” (p.23). If NACA had structured its research sections differently and with different boundaries from those which actually obtained, might Prof. Vincenti’s group have had a different composition, and could that have enabled them to think about the forces on their wings “rather differently”? Or, to put the point another way, what would have happened if propeller and wing theorists had switched roles? Would the same understanding have emerged, or would they, like the teams at Boeing, Douglas and Vega, have made subtly different artifacts? These are enormously difficult questions that we may never be able to answer in a fully satisfactory way. The need to think counterfactually may defeat even the most well – informed analyst, but these, surely, are the ultimate questions that we cannot avoid addressing.

There is one misunderstanding that I should warn you against. Theories such as Douglas’s tend to be seen, by critics, in terms of stereotypes. The stereotype has them saying that “everything is social” or that “the only causes of belief are social.” Douglas’s approach is not of this kind at all. Society is not the only cause, just as it was not the only cause at work in the episode when the tail-sections from different factories would not fit together. We must also remember that certain large-scale pieces of equipment such as wind tunnels (or great radio telescopes or particle accelerators) have a way of so imposing themselves on their users that they actually generate a characteristic social structure. Given certain background conditions, the apparatus itself may be a cause of the social arrangements. This is compatible with what Douglas is saying. Her ideas would still come into play. The point would be this: suppose people have to queue up to use such things as wind tunnels, radio telescopes and accelerators. If so, there has to be a decision about who comes first, and how long they can have for their experiment. Things have to be planned in advance, timetables have to be drawn up and respected. These are all matters which presuppose a clear structure of authority. Someone must have the power to do this. These are not, perhaps, easy environments for the individualist. Having said that the physical form of the apparatus can be a cause, it would still be interesting to know what leeway there is here. To what extent is it possible to operate such things as wind tunnels, or huge telescopes, in different ways? And if it is possible, how many different ways are there?

IV

Two papers that I have not yet mentioned seem to me to provide a particularly good opportunity for opening up themes bearing on local cultures in engineering or science. The first of them is Prof. Schatzberg’s account of the manufacture of wooden aeroplanes during World War II. The British and Canadians were successful in their continuation of this technology, the Americans had ‘forgotten’ how to do it. Although not presented in these terms, this episode clearly bears on the question of local engineering culture and style. There must have been something about de Havilland which explains why they could and did build in wood and which differentiates them from the American manufacturers, such as Curtiss-Wright, who did not or could not. And presumably there was something equally special about the Canadian firms who were especially keen to get in on the act. Prof. Schatzberg grounds these facts about the culture of firms in the wider culture. He suspects that we need to go to the symbolic meaning of the material under discussion, namely wood. Wood for the Americans meant outmoded tradition; metal meant modernity. Wood for the Canadians meant the mythical heart of their nation, with its great forests. Wood for the British was more neutral, having neither strongly positive nor negative connotations. In that matter-of-fact spirit they built the formidable Mosquito – made of ply and balsa.

Symbolic meanings are not easy to deal with, so it is worth seeing if the argument can be recast in simpler terms. Would it suffice to appeal to, say, vested interests? Canada’s wood was a major economic resource – what better stance to take than to advocate a use and a market for it? Self-interest would dictate nothing less. The American manufacturers had moved on from wood, they had gone all out for metal so as not to be left behind in a competitive market. Who wants to go backwards in a manufacturing technique? It is expensive to re-tool and re-skill. What about de Havilland? They were still building the famous Tiger Moth trainer out of wood, and supplying it in great numbers to the RAF. Even more to the point, as Prof. Schatzberg points out, they could cite their experience with wooden airliners which had important similarities with the Mosquito (p.20). Perhaps economic contingencies such as these are basic, and explain the phenomenon attributed to symbolic meanings. But as Prof. Schatzberg argues, such contingencies often balance out. Canada may be rich in forests, but so was the United States. Canada was no more short of aluminum than the United States. Britain was short of both aluminum and timber and had to import both. As for the market, why did it lead manufacturers to metal in America but not in Britain? Why was demand differently structured in the two cases? That points to a difference of underlying disposition. Perhaps the presence and operation of such dispositions can be illuminated by the idea of symbolic meaning. But whatever our thoughts about the relation of symbolic meanings to interests, Prof. Schatzberg’s intriguing study raises important questions. How local are local engineering cultures, and to what extent do they depend on the wider society?

V

I now want to focus on Prof. Hashimoto’s paper. You will recall that this deals with the work of Leonard Bairstow and his team at the Natural Physical Laboratory in Teddington during and after World War I. We are told of their problematic relation both to PrandtTs school in Gottingen and the (mostly) Cambridge scientists who worked at the Royal Aircraft Establishment in Famborough. Bairstow worked with models in a wind tunnel. He had made his reputation with important studies of the stability of aircraft. Divergences then began to appear between the results of the wind tunnel work and those of the Famborough people testing the performance of real aircraft in the air. Bairstow took the view that his wind tunnel models gave the correct result and the full scale testing was producing flawed and erroneous claims.

Prof. Hashimoto’s account is a clear and convincing example of an interest explanation of the kind I have spoken about. Bairstow and his team had invested enormous effort into the wind tunnel work. Reputations depended on it. Is it any wonder, when it comes to the subtle matter of exercising judgement and assessing probabilities, that Bairstow should be influenced by the time and effort put into his particular approach? Notice I say “influenced” rather than “biased”. I don’t think that there is any evidence in the paper that Bairstow was operating on anything other than the rational plane. He seems to have been a forceful controversialist, but those arguing on the other side had their vested interests as well. Time, energy, skill, and not a little courage, had gone into their results too. Rational persons acting in good faith can and do differ, sometimes radically. To my mind the only questionable note in Prof. Hashimoto’s analysis is when a negative evaluation of Bairstow creeps into the historical description. I suspect that the analysis goes through as well without it.

Bairstow did not just argue in defense of his wind tunnel work on models. He also held out against Prandtl’s “boundary layer” concept. This stance seems to me even more intriguing than his opposition to scale effects. If I understand the matter rightly, Prandtl’s idea of a boundary layer functioned as a justification for certain processes of approximation and simplification which made the treatment of the flow round an aerofoil mathematically tractable. For example, it allowed the problem to be divided into two parts. Bairstow’s opposition seems to have centered on his suspicion of these mathematical expedients. His obituarist, in the Biographical

Memoirs of Fellows of the Royal Society (Temple, 1965 ), suggested that Bairstow didn’t want a simplified or approximate solution to the Navier-Stokes equation for viscous flow, but a full and rigorous solution for the whole mass of fluid. He tried to produce such a treatment, but with only limited success (p.25). So again we are dealing with a matter of scientific judgement on Bairstow’s part. His response to Prandtl was not foolish or dogmatic, but a rational expression of a particular set of priorities and intellectual values. I should like to know where these priorities came from, and if they can be explained.

At first sight it seems odd that a person such as Bairstow, who placed so much weight on the experimental observation of models in wind tunnels, should incline to a mathematically rigorous and complete solution to the equations of flow. We might expect an experimentalist to embrace any clever expedient that would get a plausible answer, even at the cost of a certain eclecticism. So there is a puzzle here. Of course, it may be that we are dealing with nothing but a psychological idiosyncrasy of Bairstow as an individual, but we should at least explore other possibilities. If his strategy commanded the respect of some portion of the scientific community then we are certainly dealing with more than idiosyncrasy. I have already suggested that large installations, like wind tunnels, may demand or encourage clear-cut social organisation and hierarchy. Could it be that living with the demand for rigorous and extensive social accountability lends credibility to the demand for a correspondingly rigorous and general form of scientific accountability? Or is the issue one of insiders and outsiders, of the boundary round the group? If there were a body of existing mathematical techniques which had always sufficed in the past then why import potentially disruptive novelty from the outside? Here we see the relevance of Mary Douglas’s observations about strategies for dealing with strangers. What she says about ways of dealing with novel persons applies on the cognitive plane too. Typically, dealing with new ideas means dealing with new people. A disinclination to do the latter might explain a disinclination to do the former. Clearly all this is speculation on my part. It is no more than a stab in the dark. But however wrong the suggestions might be, I think that this is the area where the argument can be developed.

Interest explanations, it seems, are ubiquitous, and beginning with Prof. Galison and ending with Prof. Hashimoto, we have seen how naturally the different contributors have had recourse to them here. Nevertheless, there is a great deal that we do not yet understand about the operation of interests. For example, the trade-off between long term and short term interests is little understood, though they often incline us to quite different courses of action. Prof. Deborah Douglas’s account, of the relation between engineers and architects, suggests that at first these two groups felt they were in competition with one another. In the event they reached a working relationship, seeing the advantages of co-operation rather than conflict. Prof. Jakab describes how the drying up of government contracts, in 1919, led to a change in the relation between the Engineering Division at McCook Field and the private manufacturers of aircraft. After a period of plenty, a divergence of interests came to the fore and set the stage for a decade of bickering. In offering an interest analysis, then, we are not dealing with a static and unchanging set of oppositions, but a potentially flexible and evolving system of self-understanding. Critics of interest explanations, and there are many of them, often assume they are static and forget that change and flexibility are actually inherent to this manner of explanation.

VI

A further theme I could have pursued is brought out with great clarity in Prof. Anderson’s paper (a paper which, for non-specialists such as myself, was invaluable for introducing some of the basic ideas in aerodynamics). Prof. Anderson’s theme was the coming together of academic or ‘pure’ science with the needs of the practical engineer, and the synthesis of a new form of knowledge that might be called ‘engineering science’. There is a temptation, amongst intellectuals, to treat theory as higher, or more profound, than practice. Practice is the application of theory so, (we might be tempted to conclude) behind every practice there must lurk a theory. In opposition to this, Prof. Anderson reminds us of the post hoc character of the circulation theory of lift. Similarly, with regard to drag, the theoretical explanation of just why engine cowling was so effective came well after the practical innovation itself. There is a whole epistemology to be built by insisting that practice can, and frequently does, have priority over theory. That epistemology will be the one needed to understand the history of aviation and the science of aeronautics. The theme of the priority of the empirical is also made explicit at the end of Prof. Suppe’s paper which tells us about the growth of instrumentation in the history of flight testing. He argues for the significance of this site as a source of new ideas to revivify the philosophy of science. That discipline has, arguably, been too closely linked with the academic laboratory, or at least, with the image of scientific work as theory testing. Prof. Suppe takes us out of the laboratory into the hanger, where the price of failure is far greater than the disappointment of a refuted theory. The aim is to discern useful patterns in the mass of data produced by probes and gauges, it is to root out systematic error, and to find the trick of making signals stand out from noise. Again, there are no rules and no absolute guarantees. Even, or perhaps especially, in these practical fields, reality cannot speak directly to those who want and need to act with the maximum of realism.

If we were looking for a philosophical standpoint that does justice to the practical character of knowledge, for an epistemology for the engineer or aviator, where might we look? I can think of two sources that would be worth exploring, though both suggestions may seem a little surprising. First we could follow the lead of Hyman Levy. Levy was professor of mathematics at Imperial College, London, and had written one of the early textbooks in aeronautics, Cowley and Levy (1918). His theoretical work in fluid mechanics linked him with Bairstow, and he had worked in this field at the National Physical Laboratory. Levy wanted to understand his science philosophically and to develop a philosophy appropriate for “modem man”. He was also a Marxist and belonged to that impressive band of left-wing scientists in Britain in the inter-war years which included J. D. Bernal, Lancelot Hogben, J. B.S. Haldane, and Joseph Needham [see Werskey (1988)]. They did much to spread the scientific attitude and to educate the public about the potential and importance of science. As a Marxist, Levy accepted the laws of dialectical materialism, one of which is the law of the unity of theory and practice. In his Modern Science. A Study of Physical Science in the World Today; published in 1939, Levy devoted a chapter to ‘The Unity of Theory and Experiment.’ He did not here talk in the language of philosophical Marxism, but about wind tunnels and the measurement of lift and drag. His exemplar of the unity of theory and practice was aeronautical research. This might commend itself to Prof. Anderson and Prof. Suppe. But I can also think of another source of philosophical inspiration, one coming from what, at first sight, appears to be the opposite ideological direction. For a philosophy which grounds theory in practice, and meaning in use, we could hardly do better than to consult Wittgenstein’s Philosophical Investigations (1953) and his Remarks on the Foundations of Mathematics (1956). The formalistic concern with theory testing that, as Prof. Suppe observes, limits so much academic philosophy, is wholly absent from Wittgenstein’s work. Perhaps it is no coincidence that Wittgenstein was trained as an engineer and did research on propeller blades. The young Wittgenstein once asked Bertrand Russell if he (Wittgenstein) was any good at philosophy. Wittgenstein’s reason for asking was that if he was no good he intended to become an aviator.1 [3] 1909 they set up the Advisory Committee for Aeronautics under the eminent Cambridge physicist Lord Rayleigh, and dedicated a section of the National Physical Laboratory to aeronautical questions. Prof. Schatzberg reminds us that such facts stand in opposition to many a political lament about Britain’s national decline and lack of industrial spirit. But can this rapid response really have come from a culture that was (as the stereotype has it) dominated by an anti-technological elite steeped in the classics?2

As the papers in this collection make amply clear, the history of aviation as a field of study is rich and many-faceted. There is material enough here to prompt major, and exciting, revisions in the history of culture – as well as in the theory of scientific and technical knowledge.

[1]

P. Galison and A. Roland (eds.), Atmospheric Flight in the Twentieth Century; vii-xvi © 2000 Kluwer Academic Publishers.

Predating the wartime cooperatives were a number of formal and informal means for sharing technological information. The Manufacturers Aircraft Association (MAA) had since 1917 served as a means to pool critical aircraft patents. The MAA’s reach did not cover manufacturing technologies though. Nor did it have much influence on military designs, since during the interwar years the US Navy and Army Air Corps could award production contracts to any manufacturer they chose – regardless of the design’s origin. Though not the original intention of the military’s policy, this was a powerful means for spreading leading-edge aircraft design knowledge across the nation’s industry. Manufacturing knowledge, however, depended on more informal channels, occurring routinely through personal communication, trade journals, worker mobility, tooling manufacturers and raw material suppliers, and the occasional act of industrial espionage. It is to manufacturing knowledge that we turn our attention specifically, because it enlightens our understanding of the design and production process.12

One of the more dramatic exchanges of manufacturing knowledge, brought about in part through mobilization, was the large-scale introduction of presses. Job shop production methods of the 1930s involved the manual bending and shaping of sheet metal using brakes, shears, and drop hammers.13 Low production runs did not justify large capital expenditures merely to increase throughput. When orders from England, France, and eventually the United States became significant, and the number of skilled workers proved insufficient to the task, the manufacturers adopted mechanical and hydraulic presses which had long been in use in the automobile industry. Though the automobile industry provided a powerful model for mass production, many of its techniques could not be readily transferred without some measure of adaptation. In this case, not only did aircraft stampings require greater accuracy, but they were in a different material – sheet aluminum versus sheet steel. Aluminum is considerably softer than steel, and exhibits different stretch and spring-back properties. In short, the same equipment could not be universally used in the two industries.

In the late 1930s, Henry Guerin, a department head at Douglas Aircraft, arrived at a way to use hydraulic presses with rubber as one side of a die (Figure 2). Gordon Ashmead, who chronicled aircraft manufacturing techniques in the 1950s, described this innovation:

[The Guerin Process] has been the greatest single contribution to the manufacture of all-metal airplanes. The almost universal adoption of this method of forming sheet metal was the factor that lifted the forming of sheet metal out of the hand-forming category and placed it into mass produc­tion. Most airplane manufacturers give it credit for winning our air war.

While the use of rubber in forming dates to at least the 19th century, Guerin developed techniques that made it appropriate for the aircraft industry. The process substituted layers of rubber for the female half of a die. After workers positioned a sheet of aluminum over the male die, the press lowered the rubber pad and compressed it against the aluminum to the point that the rubber began to flow. The aluminum sheet formed to the male die as the rubber applied equal pressure over the entire piece. Guerin’s process was distinct from earlier methods in that the rubber was restricted to a box that fit tightly around the male die, preventing the rubber from escaping and increasing pressure on the aluminum.14

The presswork championed by Detroit thus had to go through a translation before finding widespread application in the aircraft industry. The Guerin process would have been inappropriate for Detroit, where sheet steel would have quickly abraded the rubber. Not only was the Guerin process matched for aluminum, but it required only one metal die. At a time when tooling departments were working overtime to build jigs and fixtures, a fifty-percent reduction in diework was a welcome savings. Set-up time was reduced as well, since the rubber sheets did not have to be as accurately placed as a standard female die. Typically companies did not require many presses for the Guerin process, as a single large press with moving trays and 24-hour schedules could produce large quantities of stampings. In 1940, for example, Douglas operated a single 2,000-ton press with the Guerin process. As the war progressed, ever-larger presses came into use, including 5,000-pound presses with six work trays wherein a single shift could produce fifteen thousand parts. Ashmead indicates that the Guerin Process was most economical when quantities were between a few hundred and 50,000 parts – within the range typical of aircraft production. The Guerin process found widespread application throughout the airframe industry.15

The Guerin method is somewhat unusual in that most industrial processes were not patented at this time. Many processes were simply unpatentable, and so companies kept information proprietary through secrecy. Other processes, as noted, remained traditions of practice within a company’s tooling department. But even when a patent existed, as in the Guerin case, manufacturers quickly established distinct methods of using it, these too becoming part of local practice and forming a base of tacit knowledge within individual tooling departments. While Douglas’ patent on the innovation was sufficient to inform other manufacturers of the potential for such a process, it did not necessarily ensure good results. Surrounding the Guerin process arose a new body of engineering knowledge regarding its use, involving questions of press choice, die construction and arrangement, and appropriate pressures. The exchange of this accumulated tacit knowledge would eventually take place, but only after months and even years had elapsed, often traveling indirect routes between manufacturers. Typical of these indirect routes would be trade journals, tool manufacturers, and professional societies. In the case of the Guerin Process, representatives from Continental Rubber Works and Brewster Aeronautical (and later Eastern Aircraft – an aircraft division of General Motors) penned a series of articles on the many facets of the technique. Continental Rubber, though not strictly a tooling company, would obviously benefit from the adoption of the process. In this case Brewster and Continental Rubber surveyed different firms’ techniques and published them in Aero Digest, a leading trade journal of the time.16

It was not an uncommon practice for engineers and companies to champion particular techniques through articles and technical updates. With the outbreak of war, however, such indirect means of communication became difficult, as censorship restrictions limited the ability of trade journals to describe the latest technical advancements in detail. In some cases, the Army Air Force found itself reviewing material before publication; in many cases the resulting technical descriptions were so woefully vague that they could not have been of much assistance.17

Still, without other avenues, trade journals and user-producer relationships often provided the fastest pre-war means for accumulating and disseminating such esoteric information. Production and tooling information lacked the numerous channels of exchange that existed for other branches of aircraft technology. Tooling was not a subject for standardization within the Society of Automotive Engineers (SAE) or National Aircraft Standards Committee. As a practical art, tooling had no scientific component, and thus no society like the Institute for Aeronautical Sciences to pursue theoretical advancements. Not only were tooling patents excluded from the MAA, but the MAA agreement and military contracting policy intensified the importance of keeping production technologies proprietary. If significant aircraft design patents were to be shared under the MAA or transferred as part of a military design, it became all the more important to retain a competitive advantage in production techniques.

Aircraft have two main components: airframe and engines. To avoid disasters such as destruction of the second B-29 prototype and crew, February 18, 1943,3 a basic rule offlight test is that only one of these two main components should be unproven. In some cases this is accomplished by having a new airframe design use an established powerplant.4 This is not feasible if the new airframe also requires a new powerplant. Then existing airframes are modified to fit the new engine.

Thus, a B-29 Superfortress was used in 1943 as high-altitude jet-engine test bed for the General Electric 1-16 developed for the X-P59, America’s first turbo jet aircraft.5 A subsonic XF-4D swept wing fighter repeatedly was taken through the sound barrier in tests of GE turbines for supersonic aircraft. For the T-38 supersonic trainer, a modified FI02 carried the diminutive J-85 engine in its bomb bay and, when airborne, the tiny engine would be lowered hydraulically, air started, and then put through its paces. Flight testing of the gigantic J-93 engines for the X-B70 mach 3 bomber used a modified supersonic B-58 bomber with a J-93 engine pod slung in its underbelly (see Figure 12). Once engine development and testing had progressed

[3]

I have tried to relate the issues discussed in the preceding papers to some broader themes in sociology and the sociology of knowledge. I have tried to bring out the role of interests, the need for comparative study and the need for a typology of social forms that can help us see patterns in engineering styles. My aim has been to raise questions and problems of a somewhat more general kind than has been addressed in the papers themselves. The richness of the papers means that there are many possible lines of comment and inquiry that I could have pursued but did not. In particular I have neglected what might be called the political or institutional dimension. This means that I have rather short-changed those contributors who have addressed this side of things. There is much that could and should be said on such matters. For example, there is a whole nest of issues that emerges in these papers about the relation between the so-called ‘free market’ and various forms of government finance and subsidy. Time and again we see the importance of government research and state finance, whether it be tacit subsidy of civil aviation through military expenditure or the research effort of government laboratories. Prof. Roland quotes the figure of 85% of aerospace research deriving from government funding.

A second example, to which I cannot resist drawing attention, is provided by a significant observation made in three of the papers. Profs. Bilstein, Crouch and Hashimoto, respectively, all note how rapidly, in the early years of this century, the British government responded to the emerging phenomenon of the aeroplane. In

The Boeing-Douglas-Vega (BDV) pool was among the first of the major wartime aircraft cooperatives. As a product-oriented organization it illustrates the manner in which engineering knowledge is embedded within a firm. Before the attack on Pearl Harbor, the US government made arrangements for a number of standard aircraft types to be produced jointly by different manufacturers. Boeing, Douglas and Vega were to produce the B-17 bomber, a four-engine Boeing design begun in 1934. Implicit in such an arrangement was that Douglas and Vega would gain access to Boeing’s system of manufacture. Within this system Boeing had many individual production techniques unique to their company, some proprietary, others matters of Boeing’s manufacturing culture. Among the differences noted in the trade journals were Boeing’s drawing system, factory methods, and unique tools.18 To coordinate the three companies’ manufacturing, procurement, design changes, and scheduling issues, they formed the BDV Committee. Begun in May of 1941, the Committee was located in Seattle and included representatives from all three manufacturers as well as the Army Air Corps (later the Army Air Forces after its 1942 reorganization). In addition to a powerful executive committee, three sub­committees operated, including Tooling, Technical, and Procurement, all based in Seattle. Through these committees, Douglas and Vega were given “ready access to all phases of Boeing production.”19

The BDV Committee contemplated a wide-ranging transfer of information, extending beyond aircraft blueprints to include production information as well. Douglas and Vega received all the master tooling and jigs, as well as one complete aircraft and numerous sets of parts for initial production. From their factories in southern California, Douglas and Vega sent scores of workers to Boeing’s Seattle facilities to personally observe tooling construction and manufacturing methods. The extent of cooperation was so great that workers from all three companies joined in building assembly and sub-assembly jigs. Highlighting the relationship between production and organization, an integral part of the technology transfer to Douglas and Vega was managerial information, including major assembly man-hour lists, percentage breakdown charts, schematic drawings with man-hour indications, assembly books, parts cards, and parts list. These were all means for controlling and auditing production flow. Finally, Boeing learned to adopt some of the methods it found in Southern California, such as Douglas’ “production illustration” method.20

The members of the BDV Committee were not entirely unprepared for the obstacles posed by technology transfer. Indeed, they seemed quite aware of the fact that traditions differed dramatically between firms. Regarding tooling, Mac Short, the Vega Vice President of Engineering wrote:

A survey of existing tooling by the Tooling Subcommittee revealed that there was in existence in the Boeing plant a number of small tools for which there were no available drawings. These tools had been constructed in many cases by the workmen on the job during the preceding years of building B-17s. It was the decision of the BDV Committee that these tools represented “know­how” and would be of aid to the Douglas and Vega companies if the information could be transferred to them.

The exchange of such “know-how” was a necessary component of bridging these different engineering cultures. Indeed, the BDV Committee had to create a standard nomenclature for design and tooling engineers since all three companies had, essentially, different languages.21

Still, there was great confidence that the three manufacturers would be able to build identical aircraft. Boeing’s own press releases boasted that “[Boeing, Douglas and Vega] will turn out completely assembled four-engine bombers, identical even to the point of interchangeability of parts.”22 What members of the BDV Committee did not anticipate was the extent to which differing traditions of manufacture as well as conflicting production philosophies would preclude the complete adoption of Boeing’s production system. So long as differences remained, there were bound to be discrepancies between the aircraft produced.

Boeing used what it called a production-density system (later termed multi-line). The process brought nearly complete assemblies together at the very last stage of manufacture.23 Rather than a dominant single assembly line stretching from jigs to the hangar doors, each assembly had its own line terminating at final assembly (figure 3). Most of the installation work on the assemblies was completed before final assembly, meaning that aircraft spent the least amount of time in the stage that consumed the most space. Production-density was considered, “the antithesis of the elongated single production line.”24 The logic behind concentrating on assemblies and sub-assemblies as opposed to final assembly was ably described by Sidney Swirsky, writing with a touch of vitriol in 1943:

That the ideal straight-assembly line for aircraft is, after the fashion of the auto-makers, the final assembly line, is in itself strictly mythical. Actually, the aviation production line must start when parts are received in the form of raw stock at one end of the plant. In order to get more sub-assem­blies to the final line faster, the plant’s board of strategy, including the vice president of manufacturing, the factory manager and the plant layout engineer, must straighten out as much as possible the lines by which fabricated parts and sub-assemblies are to reach the final line. The final

line itself in an aircraft plant is much less a problem than are the sub-assembly lines; the complex­ity of routing and fabricating airplane sub-assemblies is the cause of the ever-threatening bottleneck which can stop production – not straightness or lack of it in the final line, [his italics]25

For Boeing, eliminating the long final assembly line and opting for numerous lines of shorter length had the advantage of requiring less expansive production facilities – one of the original reasons for its adoption in the late 1930s. But as prime contractors for production, not subcontractors, Douglas and Vega were not obligated to implement Boeing’s production-density system. There is no doubt that they benefited from Boeing’s experience, but they were forced to blend Boeing’s aircraft into their own companies’ manufacturing culture. Engineers at Douglas decided that straight-line final assembly was just the thing (Figure 4). Cradled by overhead carriers, workers mated fuselage sections which progressed from station to station down the line. At the first station of final assembly, the fuselage was already in one piece while workers attached the wing sections. Installation of parts and components continued through final assembly. Douglas would later call its straight-line assembly system “Flow-line” and apply it to the A-20 and A-26 aircraft lines. Vega opted for a third system, which it vaguely described as a
“breakdown system.” The focus here was on the fabrication of numerous small pre­assembled components that came together on master jigs. Vega, not unlike the other manufacturers, explained that its system attempted to make the best use of very limited floorspace.26

The result was three different ways of producing the B-17, and an indeterminacy about the best way to mass produce aircraft. An engineer writing on the Douglas system was careful to avoid making comparisons between different production ideologies, arguing that, “Among the many abilities of Americans… is the ingenuity by which different groups achieve similar or identical results, but with widely varying, sometimes seemingly opposite methods.” Unfortunately, the resulting aircraft from these methods were merely similar, and never identical. In fact, in October of 1943 General “Hap” Arnold specifically contacted the National Aircraft War Production Council (NAWPC) about the “non-interchangeability” of assemblies from different companies. He complained that “the different processes employed by the various manufacturers preclude the replacement of a Vega tail assembly by a Boeing or a Douglas tail assembly.” Despite rigid adherence to a single set of master gages and templates supplied by Boeing, differing production ideologies and traditions of practice brought about three different products.27

Figure 4. Douglas B-17 Major and Final Assembly (Building 12 and 13 of the Long Beach Plant). The assemblies and sub-assemblies move from left to right in the bottom building, and then from right to left in the upper building. Source: US Army Air Force, Air Materiel Command, Industrial Planning Branch, “Construction and Production Analysis: Douglas – Long Beach, B-17” (August 1946), exhibits 8 and 9.

While writers lauded the identical qualities of the aircraft in public, the manufacturers privately expressed their concerns about interchangeability within the Aircraft War Production Council. Even companies that were not part of the larger co-production schemes had great difficulty maintaining interchangeability. They attributed the problem to a number of causes, including sub-contractors who, despite having master jigs, often produced parts differently. Within the main airframe firms, they noted the following:

Here a distinct difference in manufacturing processes, tooling, model design, equipment and some small parts exists. The introduction of changes varies. The character of tooling is as diverse as the date, volume, and production rate of each contract, the plant lay-out, type and skill of personnel, climatic conditions, local fabricating habits, and material substitutions and improvisations.

The problems outlined by Hap Arnold were eventually addressed in military specification AN-I-21, which called for various classes of interchangeability. But while the military wanted interchangeable assemblies, sub-assemblies, and parts, such requirements would entail that engineering cultures attain some level of interchangeability as well. Ultimately the Aircraft War Production Council informed the government that the AN-I-21 specification would be impossible to implement across the industry. They argued that because “each company and product presents a specific design and manufacturing problem,” that solutions would need to be equally individualized.28

Despite the lessons of the BDV experience, technology transfer and interchangeability issues remained, even for subsequent cooperative efforts such as the B-29 pool. The Army had chosen the Boeing B-17 and Consolidated B-24 to be the standard large bomber types for the war, but they also sought to place a more modem and capable aircraft into production. This was the Boeing B-29. Like many other aircraft, it would be produced by a group of manufacturers, including Boeing – Wichita, General Motor’s Fisher Division, and North American Aviation. Eventually GM and North American were replaced by Bell (Marietta, Georgia) and Boeing-Renton, with the Fisher Division remaining as a subcontractor. In time, the Omaha plant of the Glenn L. Martin Company would also join the pool. As with the B-17 pool, there was a B-29 Committee established to handle the same coordination problems that arose on the earlier aircraft. Specific details from the B-29 pool give us additional evidence in understanding the difficulties of engineering exchange.

Engineering drawings, when properly rendered, are supposed to communicate all the essential aspects of a design, such that trained workers with appropriate tools can recreate the artifact to specification.29 While Boeing did supply thousands of drawings to the other contractors, all participants understood that these were insufficient to achieve complete interchangeability. Just as a skilled craftsperson uses the same measuring tape for a single project, so did Boeing. The company built master control gages in Seattle which served as the final word on all critical dimensions. These gages remained in Seattle, and were used not to construct aircraft, but to produce other master gages, which in turn would be used to check the accuracy of jigs and completed parts (see figures 5 and 6). Usually the gages bore only slight resemblance, if any, to the assemblies or sub-assemblies to which they corresponded.

Made of thick pieces of steel, the gages were extremely rigid; they conformed to actual aircraft parts at specific reference points – typically locations where a part or assembly would meet another. The B-29 Committee directed the following:

Master gages and master templates shall be used by all four prime contractors and their subcon­tractors to insure interchangeability of all parts which the Air Corps requires to be interchangeable…. Tooling for fabrication of parts shall be such as to insure that all parts are struc­turally and aerodynamically identical. It is not contemplated that tooling be identical. Such prime contractor and subcontractor may construct parts by the method or methods best suited to his shop equipment and practices, consistent with the above; however, the Committee must be assured by the contractor concerned that such tooling will produce satisfactory parts.

In theory, exact master gages distributed to all the manufacturers should have rendered the same parts, sub-assemblies, and assemblies.30

Two situations show the difficulty of using master gages as a way to communicate engineering information. In November of 1942, the B-29 Committee wrote: “Trial indicated that the extremely close angular tolerance required could not be successfully transferred from the Boeing furnished Master Gages.” While the

information about angular tolerances was encoded into the gage, it could not be used to ensure precision in the produced parts. In effect, the engineering information could not be extracted from the gage without the production of additional gages. A more interesting situation developed a year later when the Committee learned of discrepancies between the nacelles produced by GM’s Fisher plant, and the aircraft wings to which they were attached. The nacelles, when placed on aircraft from the Boeing-Renton facility, had attachment holes that were as far as ft a hole diameter off (a very large distance in a precision product). Boeing-Renton checked its own master control gages and found that their own parts were correct, but that the Fischer parts were not. Bell in Marietta experienced the same problems, but oddly, Boeing’s main B-29 plant in Wichita did not. They fit perfectly there and the plant had already turned out nearly 50 aircraft. The conclusion of the Committee was that,

.. .whether Fisher and Wichita are right or wrong in contrast to Boeing-Renton and Bell, it appears that the only practical answer is for Boeing-Renton and Bell to change their hole locations to coin­cide with the nacelles as produced by Fisher. This of course will mean the changing of the master gages at Boeing-Renton and Bell and the changing of the master control gage at Boeing-Seattle to agree with the masters at Wichita and Fisher.

Later, Fisher changed the process after the 210th set of nacelles – such that the discrepancies were removed. Why these particular nacelles fit at Boeing – Wichita was not explained, but it begs a question. If two of the most prominent engineering organizations of the 1940s, the Fisher Division of General Motors and the Boeing Company, could not transfer engineering information via accepted methods (drawings and master gages), what engineering organizations in the US were competent to produce and interpret such materials? Obviously the engineering precision that is supposedly built-in to engineering drawings and master gages must be complemented by not only technical skill, but additional forms of communication as well in order to bridge different engineering cultures. This explains, in part, Bell’s insistence that they be furnished a large quantity of parts so as to hand-assemble their first five aircraft. In addition, they asked for “two fuselages in sections, structure only… one fuselage in detail parts,” and finally a “sample airplane complete with installations.” All of these structures served to educate engineers and workers in a way that drawings and gages could not.31

Where gages were not used, drawings were supposed to suffice. One last incident concerning the B-29 gives us additional insight into the process of technological design. In August of 1942 the Fisher Division complained that it had yet to receive the drawings for the electrical wiring. Boeing responded, saying that such drawings were not produced in final form until after the first few aircraft were built. Boeing suggested that someone be sent from the Boeing Electrical Shop to personally advise Fisher, the implication being that this aspect of aircraft design routinely took place closer to the factory floor. Unlike the aforementioned cases where design and tooling information was somehow lost or changed in the transfer process, here we find that design information accrued as the product took shape. This is not surprising, but it suggests further that design trajectories are not fully determined on the engineer’s drafting table. Technicians, mechanics, and laborers not only misinterpret or lose initial design information, they create it as well.32

All technologies differ from one another. They are as varied as humanity’s interaction with the physical world. Even people attempting to do the same thing produce multiple technologies. For example, John H. White discovered more than 1000 patents in the 19th century for locomotive smokestacks.1 Yet all technologies are processes by which humans seek to control their physical environment and bend nature to their purposes. All technologies are alike.

The tension between likeness and difference runs through this collection of papers. All focus on atmospheric flight, a twentieth-century phenomenon. But they approach the topic from different disciplinary perspectives. They ask disparate questions. And they work from distinct agendas. Collectively they help to explain what is different about aviation – how it differs from other technologies and how flight itself has varied from one time and place to another.

The importance of this topic is manifest. Flight is one of the defining technologies of the twentieth century. Jay David Bolter argues in Turing’s Man that certain technologies in certain ages have had the power not only to transform society but also to shape the way in which people understand their relationship with the physical world. “A defining technology,” says Bolter, “resembles a magnifying glass, which collects and focuses seemingly disparate ideas in a culture into one bright, sometimes piercing ray.” Flight has done that for the twentieth century.

Though the authors represented in this volume come from very different backgrounds, we share a concern to move beyond a fascination with origins and firsts. Instead, the essays of this book all attend to a technology forever in process, a technology modified all the way through its history. From its shifting relationship with the aerodynamic sciences to the shop-floor culture of bomber production; from the changing functions of patented mechanisms to the standards of pilot training, protocol, and disaster inquiries. Through and through, this is a book about the heterogeneous practices of aviation all the way down the line.

In some ways the technologies of flight seem remarkably stable: in looking at the earliest airplanes, the wings, ailerons, rudder and elevators seem remarkably congruent with the same features on a 747. Yet, over the course of the twentieth century, the technologies of flight have radically altered. Consider the perspective of Hugh Dryden, the former Director of the National Advisory Committee for Aeronautics and Associate Director of the National Aeronautics and Space Administration. He used to say the he grew up with the airplane. He wrote his first paper on flight in 1910, when he was 12 and the airplane was 7. In it he argued for [1] “The Advantages of an Airship over an Airplane,” earning an F from a prescient if harsh teacher. At the time of his death in 1965, Dryden was helping to orchestrate humankind’s first journey to an extraterrestrial body. Bom before the airplane, Dryden lived to see humans fly into space.

Now, at the end of the twentieth century, humans are about to occupy an international space station. Its supporters believe that it will begin a permanent human presence in space. The Wright brothers could hardly have imagined that their primitive attempt to fly would lead within a century to a permanent presence off the Earth. The technology that they inaugurated transformed humans from gravity – bound creatures scurrying about the face of the Earth to spacefaring explorers looking back at the home planet as if it were an artifact of history. At the time of Apollo, historian Arthur Schlesinger, Jr., hazarded the guess that when future generations reflected on the twentieth century they would remember it most for the first moon landing.

Flight has defined the 20th century symbolically, spiritually, and spatially. Individual airplanes such as the workhorse DC-3, the democratic Piper Cub, the dreadful B-29, the rocket-like X-15, and the angular Stealth fighter have imprinted their shapes and their personalities on modem life. They represent our contemporary ability to deliver people, bombs, or disaster relief anywhere in the world in a matter of hours. Popular imagination has rendered the Wright brothers, Charles Lindbergh, and Chuck Yeager as quintessential^ heroic individuals, icons of the human yearning to subdue nature, achieve freedom of movement, and conquer time and space. To the extent that the world has become Marshall McLuhan’s global village, flight has made it so. Communications put us in touch with each other, but airplanes put us in place.

Is a defining technology like other technologies? Or is it different? Does it obey the same mles, evince the same patterns, produce the same results? Or do defining technologies, by virtue of their powerful interaction with society, operate differently? The essays collected in this volume shed considerable light on these questions.

This volume – and the conference that launched it – began with a series of discussions between Alex Roland and Dibner Institute co-directors Jed Buchwald and Evelyn Simha. Would it not be original and fruitful, they wondered, to bring together historians of flight with a wider group of scholars and engineers from related fields – people who had not necessarily written on the history of flight? Peter Galison was recmited as a historian of science and private pilot – and together Roland and Galison began assembling the mix of historians of the technology of flight and the engineers, philosophers, sociologists, and historians who are represented here. Our great debt is to the Dibner Institute for their support of our conference from 3-5 April 1997, and the continuing interest they have had in seeing this volume come to fruition.

In addition to the individual merits of the papers gathered in this volume, we believe that collectively they shed light on the question of whether or not flight functions like other technologies. The simple answer is yes and no. The complete answer is more interesting and more provocative. Readers may find their own version of that answer in the papers that follow. Here we will attempt only to point out some of the ways in which the answer might be construed from these contributions.

First, flight may be seen as similar to other technologies. Patents represent one area in which this is true. These government charters to promote and reward innovation are often depicted as measures of inventive activity and stimulants to technological change. They might be expected to have played a significant role in the development of flight. Thomas Crouch and Alex Roland confirm this expectation, but find that it operated in unexpected ways. Crouch debunks the myth that the Wright patent choked U. S. aviation development in the period leading up to World War I. Though the Wright patent was surely unusual in its scope and impact, it did not retard development, as its opponents claimed, and it was not unique. Roland takes up the same issue where Crouch leaves it. Studying the impact of patents on airframe manufacture in the period from World War I to the present, he finds that patents were important at the outset, less so over time. This pattern is familiar in cumulative industries where foundational patents launch a new technological trajectory but then decline in relative importance.

National subsidy also shaped aviation in the same way that it has shaped other technologies, such as shipbuilding, armaments, microelectronics, and computers. Increasingly in the modem world, industrialized states have intervened in technological arenas deemed important to national security or prosperity. Aviation is no exception. Takehiko Hashimoto’s paper demonstrates the strong role of government policy in the development of British aviation, a pattern repeated in other developed European nations. Walter Vincenti describes a research project within the National Advisory Committee for Aeronautics (NACA), one of the institutional mechanisms by which the United States government subsidized aviation development. The cross-licensing agreement at the heart of Roland’s paper came into being at government behest and with the benefit of a $2 million government buy-out.

Dual-use is another characteristic that likens aviation to other technologies. It means that the technology has both military and civilian applications. From the very first, aviation has been dual-use; the Wright brothers built their plane as an end in itself, but first sought to sell it to the U. S. Army. George Lewis, the Director of Research of the National Advisory Committee for Aeronautics in the 1930s and 1940s, confessed that he could not think of any improvement in aviation that would not benefit military and civilian aviation alike. Thus the research conducted at the Army’s McCook Field in the teens and twenties, examined here in Peter Jakab’s paper, turned out to have important civilian applications. Likewise, the research that Walter Vincenti and his colleagues conducted at the NACA in the 1940s was equally applicable to the wings of military and commercial aircraft. And the production methods worked out in the mass assembly of B-17’s and B-29’s described by Robert Ferguson utterly transformed the practice of airplane assembly after 1945.

Ironically, dual-use has become less pervasive in modem aviation at just the time when the military services have focused more attention upon it. The reason

is the increasingly specialized nature of modern, high-performance military aircraft. Many of them, for example, now feature skins that resist heating at high speeds, a characteristic unnecessary on commercial aircraft. Stealth technology, one of the marvels of recent research and development, has no utility for civilian aircraft. The special stability characteristics of fighter aircraft are unique. The avionics of high-speed, low-level flight have few applications on the commercial side, nor do electronic countermeasures, ejection seats, and the ultra-high flying technologies reserved almost exclusively to reconnaissance aircraft. Of course the period before World War II had its share of military technologies with no civilian analog, such as bombsights, armaments, and carrier-landing capability. But the irony remains that civilian applications of military aeronautical technology have become more elusive just when the military and the aerospace industry have taken the greatest interest in them.

The other side of dual-use, of course, is that research and development aimed at military products often differs from that supported by the commercial market. The military usually requires higher standards of performance and reliability. Perfecting such technology may require more research and development than market forces could support. But once the technology has been perfected, it may be transferred to the commercial marketplace fairly cheaply; the overhead has already been absorbed. The classic example of this is U. S. computer development during the Cold War,3 but aviation provides a similar instance. The instrumentation developed by Frederick Suppe and his colleagues to test the performance of military aircraft could later be installed on commercial planes for a fraction of the cost. The turbofan engine development described by George Smith and David Mindell came free to the commercial manufacturers, fully paid for by the military. This phenomenon, a commonplace of United States development during the Cold War,3 seeps into the issue of national subsidy. Roland’s paper concludes that one reason for the success of commercial airframe manufacture in this country was the indirect subsidy of government research. Much of that subsidy took the form of military R&D.

Also, in its relation to science, aeronautics resembles other science-based technologies. John Anderson traces paths by which scientific knowledge has entered the realm of aeronautical engineering. Similar paths have marked the intercourse between thermodynamics and engine design, between solid-state physics and microelectronics, and between microbiology and genetic engineering. In aeronautics, as in all of these other realms, traffic moves along these paths in both directions. Just as science often provides theoretical models for better technology, so too does technological development often provide challenges to theory and new tools for scientific investigation. Walter Vincenti’s paper offers a stunning example of the way in which cross fertilization of an experimental technique from one investigation allowed a breakthrough to conceptual understanding of physical phenomena in another. George Smith and David Mindell explain how advances in metallurgy yielded titanium fan blades for more efficient engines. By exploring the texture of shop-floor life in World War II aircraft production, Robert Ferguson shows how the design process was never restricted to the “top” of the assembly process – innovation, modification, re-design occurred all the way down from initial sketches to the final stages of production. These papers thoroughly rebut the naive picture in which design and knowledge enter only at the start of a massive project.

Equally revealing are the ways in which flight is different from other technologies. First, it is more dangerous than most. Peter Galison’s paper wrests technological insight from two gripping commercial airline accidents; the imperative to identify the cause of an accident drives investigators toward a definition of agency that challenges our very understanding of technological systems and they ways in which they fail. Whether it is the test pilots in Frederick Suppe’s account of flight instrumentation or the fatal crash of Otto Lilienthal, whom Roland represents as the inspiration for the Wright brothers, disaster accompanies the failure of this technology more swiftly and surely than almost any other.

Cost also separates flight from most technologies. Deborah Douglas explores the price of passenger accommodation in the early years of airport design and construction. If customers were going to pay for air transportation, they had to pass through a site that connected everyday life in two dimensions with a technology of three dimensions. The problems were enormous and costly. Frederick Suppe opens up the world of flight instrumentation, one of the auxiliary technologies without which flying would be riskier and less understood. Walter Vincenti reveals the painstaking detail required to understand – or begin to understand – the character of supersonic flow over an airfoil. George Smith and David Mindell track the evolving relationship among compressor, turbine, and airflow that characterized the incremental development of high-bypass jet engines. The wind tunnel in which these ideas were tested cost more to design, build, operate, and staff than did the complete research and development programs in many other technologies.

The romance of flight permeates all these papers, and sets this technology apart from most others. Frederick Suppe captures it in his account of daring test flights in the desert. Even Deborah Douglas’ account of early airport design resonates with the adventure and excitement that airport designers were trying to exploit. The heroic airmanship of pilot A1 Haynes and his crew in nursing United Airlines Flight 232 to a controlled crash ennobles an otherwise tragic technological failure. A technology that allows humans to “slip the surly bonds of earth” cannot help but appear romantic in comparison to the mundane tasks to which most technology is committed. Indeed, in recent years scholars have begun to historicize the romance of aviation, using the airplane as a means of exploring larger issues of twentieth century cultural history.4

Few technologies generate the infrastructure that has grown up around atmospheric flight. The Wrights achieved flight with the materials that they could haul by rail and boat from Ohio to North Carolina, supplemented by food and shelter purchased locally. Today aviation needs research and development of the kind described by Smith and Mindell, Hashimoto, Eric Schatzberg, and Vincenti; testing and instrumentation like that explored in Suppe’s paper; institutional guarantees of rights to innovation as laid out by Crouch, Roland, and Roger Bilstein; operating

infrastructure such as airports (Douglas) and accident investigation (Galison); and much more. Some of the infrastructure is private, some public; most of it now has to be coordinated internationally, so that flight can cross national borders without loss of system integrity.

Finally, atmospheric flight requires higher standards than most other technologies, in part because of the danger involved, in part because of the cost. When a single airliner can cost more than $100 million and an airport costs billions, the incentive to ensure their faultless operation is high. When a single accident can kill hundreds of people, the incentive is incalculable. Hashimoto, Schatzberg and Ferguson show the ways in which standardization entered aircraft design and testing early in the century. Suppe’s paper demonstrates how the price of standardization has risen, with ever more expensive and accurate instrumentation and ever more data points required to get the information necessary for confident operations. Galison’s inquiry into accident investigations reveals the lengths to which the government will go to root out system weakness and replace it with the standardized practice linked to higher levels of safety.

These papers also demonstrate the ways in which flight has varied from time to time and place to place. The historical literature of flight is notoriously parochial and nationalistic; indeed, it proved difficult to break that pattern in assembling the participants in this volume. But even when flight is studied comparatively and from various perspectives, it is difficult to discern international patterns over time. Rather the principal artifacts of this technology, the airplanes themselves, along with their support equipment and infrastructure, reflect the national styles and the periods in which they were generated. The reasons for this are not hard to find.

The main reason is institutional. In consonance with recent scholarship on the shaping influence of the research environment, several papers explore the ways in which differing research styles produced differing artifacts. Hashimoto takes sociologist of science Bruno Latour’s notion of inside/outside research behavior as his explicit model for understanding the impact of Leonard Bairstow on the development of British aviation in the years between the world wars. The concentration of the British on stability research and wind-tunnel modeling, and their tardiness in adopting boundary layer theory and corrections for wall interference effects, were a direct result of Bairstow’s determination to defend his research base in empirical, wind-tunnel studies. It took an international, comparative research project in the 1930s to reveal the extent to which this concentration had retarded British development. Robert Ferguson explores the specificity of engineering cultures even when the companies are producing the identical airplane. Or perhaps, as Ferguson shows, “identical” needs to be put between quotation marks: it seems that no amount of drawing, personnel exchange, or even exchange of airplanes could surmount the myriad of details that separated production at Boeing from that at Vega or Douglas.

Like Hashimoto, our commentator, David Bloor, has stressed the potential fruitfulness of a sociological reading of institutional identity, though Bloor invokes the sociologist Mary Douglas. Douglas’s idea is that rather than dichotomizing institutions, we might invoke a two-by-two matrix, so to speak: institutions are either egalitarian or hierarchical, and they are either boundary-policing or boundary – permeable. Using this four-way typology, Bloor queries our various authors as to where on such a chart they might find their “engineering cultures,” e. g., General Electric versus Pratt and Whitney or Goettingen versus Cambridge. That is, Bloor wants to know whether the various ways that engineers treat objects reflect basic sociological features of the way they treat the people with whom they work.

Also attentive to engineering culture is Walter Vincenti, who attributes the success of his research team to the creative, unstructured, eclectic laboratory environment they enjoyed at the Ames Aeronautical Laboratory of the U. S. National Advisory Committee for Aeronautics. He pictures a free association between theory and empiricism, in which individual researchers were able to bring new ideas and proposals from any source. They were measured by their efficacy in solving the problems at hand, as opposed to the doctrinaire constraints imposed by Bairstow in the British environment.

Suppe presents an entirely different research environment, instrumentation of flight testing. The principal dynamic at work here is the relationship between improving instrument technology and the ever increasing demand for more data. Instrumentation offers more and better data, but it can hardly keep pace with the demands for more data points and more precision as aircraft speed and performance improve. The research imperative is therefore not to figure out the design of better aircraft but to develop and field equipment that will keep up.

Research and development in aerodynamics took a fascinating, counterintuitive turn in the account Smith and Mindell provide of the high-bypass jet engine. While one might expect that a radical new design by one company would stimulate equally radical changes in the competition, these authors show quite the reverse took place. In a highly secretive program, General Electric stunned the aviation world with their novel 1957 single-stage, aft-mounted fan. Pratt and Whitney responded, but their counter was a similarly efficient but completely incremental two-stage fan with vastly simpler aerodynamics. In part because of novelty-related start-up problems for GE, P&W triumphed in the marketplace.

Peter Galison describes an entirely different institutional imperative. The National Transportation Safety Board (NTSB) is required by law to investigate technological failure in a particular way. Tom between seeking to understand an accident in all its complexity of contributing causes and the institutional demand to locate a more localized “probable cause,” accident investigation is a vexed enterprise. Under these constraints, the investigating team is often driven to identify point failures, especially point failures that are subject to remedy. Thus an institution that is poised at the very nexus of technological understanding, i. e., at the point where technology fails, is bound by law to view that failure narrowly and instrumentally. This can lead to great technical virtuosity and poor contextual understanding. And so, while trying to preserve a “condensed” notion of causality, the investigators time and again sought to embed the causal account in the wider spheres aimed at by psychological, organizational, and sociological approaches.

Peter Jakab captures the excitement of McCook Field in its early years. Before the U. S. Army knew what it was going to do with aviation, and before its institutional research arrangements settled into routinized patterns, McCook Field was a hothouse of innovative ideas and experiments. Distinguished researchers accepted appointment there and brought their creative energies to a field rich with promise and interest. If anything, there was too much innovation and experimentation at McCook Field in these years, with the research program seemingly running off in many different directions at once. The result was that McCook Field did not itself come to be credited with any great technological breakthroughs, but the people who worked there honed their research skills and gained invaluable experience. As an institution, it turned out to be a better training ground than a proving ground.

Even Deborah Douglas’s account of airport development in the United States suggests the powerful ways in which institutions shape technological development. Commercial passenger travel achieved market viability in the United States in the 1930s. The so-called “airframe revolution” that produced the DC-3 is most often credited. But Douglas reveals that airport design also played a role. Only when the airport came to be envisioned as a user-friendly, comfortable, safe, and aesthetically pleasing nexus between air and land travel could airlines hope to attract the passengers who would make their enterprise profitable. The American decision to make airports local institutions prodded the market toward competitive design and production that pitted cities against one another in their claims to be most progressive and advanced. The results were airports like LaGuardia in New York, which lent a unique stamp to American aviation and helped to foster development of the entire commercial enterprise.

John Anderson attests to the importance of institutions in transferring knowledge and understanding back and forth between scientists and technologists of flight. Nikolay Joukowski, the head of the Department of Mechanics at Moscow University, was the first scientist to take Otto Lilienthal’s work with gliders as a fit subject for scientific investigation. The resulting Kutta-Joukowski theorem, which revolutionized theoretical aerodynamics, gained purchase in part because of the weight of Joukowski’s reputation and his institutional setting. So too did Ludwig Prandtl’s position at Goettingen University lend credibility to his research on the boundary layer. He took up a practical problem, theorized it in a revolutionary scientific concept that transformed modem fluid dynamics, and then gave it back to practical application in his own work and his students’ on the flow of air over wings and fuselage.

The cases of Joukowski and Prandtl serve not only to illustrate the ways in which institutions have shaped the development of flight technology but also to introduce a final way in which these appear to address differences in flight. University research in Russia and Germany influenced aeronautical development long before American and British universities achieved such an impact. In fact the German style of university-based, theoretical research in aerodynamics was spread to the United States by two of Prandtl’s students. As Roger Bilstein makes clear, Max Munk went to the National Advisory Committee for Aeronautics in 1929 and developed there the innovative variable density wind tunnel for which the NACA won its first

Collier Trophy. Even more significantly, Theodore von Karman accepted the invitation of Nobel laureate Robert Millikan to join the faculty at the California Institute of Technology and direct its Guggenheim Aeronautical Laboratory. From that institutional base von Karman went on to exert a formative influence on aeronautical research and development and on the policies of the United States Air Force. American aeronautical development took on a more theoretical turn because of the immigration of this European, especially German, style of research.

National variations in research styles are evident in other papers as well. Eric Schatzberg reveals the impact of national tastes for materials in his discussion of the wooden airplane in the 1930 and 1940s. The United States’ preference for metal as an aircraft building material flowed from preconceptions about the modernity of aluminum, not from a judicious evaluation of the merits of wood. For equally nationalistic reasons, Canadians preferred wooden aircraft and developed them with great success during World War II. And the Americans, under the pressure of World War II developed modes of exchange between competing airframe manufacture that fundamentally altered the character of the industry.

Hashimoto uses the International Trials of the early 1920s to demonstrate the differences in national research styles and practices and the difficulties involved in standardization. The Trials also revealed the parochialism of the British and contributed to their movement toward continental practice. Roland demonstrates the ways in which specific national experience in the United States differentiated the impact of patent practice from that in other countries. The introduction of a patent pool in 1917 was driven by the legal logjam surrounding the Wright patent. The government intervened to buy out the Wright interests and the interests of their leading competitor, Glenn Curtiss. The resulting patents pool lasted for 58 years and distinguished United States patent experience from that of any other nation. This history cries out for a comparative study of aircraft patenting experience in other nations to see what conclusions might be drawn about the impact of patents in general and the comparative efficacy of the American model.

Bilstein’s paper is the most self-consciously international and comparative. It both reinforces and challenges the general perception of aviation as a parochial and nationalistic technology. Bilstein notes, for example, that American aeronautical development really was different from that in other countries, a fact that no doubt helps to account for America’s remarkable domination of this industry for so many years. But Bilstein also notes that ideas and innovations from other countries were constantly finding their way to America, undermining the stereotypes of native American genius that have plagued the field since the remarkable achievement of the Wright brothers.

But Bilstein’s paper also helps to point up one of the great generalizations that may be applied to this quintessential twentieth-century technology. As the century has proceeded, the technology has become more universal and homogeneous, less parochial and nationalistic. Japan is licensed to produce a version of the American F-16. American airlines fly European-manufactured Airbuses. American aircraft manufacturers mount Rolls Royce engines on their planes. Virtually every large

airplane in the world uses fundamentally the same landing gear. Airports, navigation, and ground support equipment the world over are becoming increasingly standardized. The differences between aircraft remain stark and obvious, and the variations from country to country continue to reflect idiosyncrasies of national style and infrastructure. But all this diversity persists in the midst of a general trend toward uniform and standardized technology. This, too, is a mark of the twentieth century.

Alex Roland Peter Galison

NOTES

1 John H. White, American Locomotives (Baltimore: Johns Hopkins University Press, 1968), p. 115.

2 J. David Bolter, Turing’s Man: Western Culture in the Computer Age (Chapel Hill: University of North Carolina Press, 1984), p. 11.

3 Paul Edwards, The Closed World: Computers and the Politics of Discourse in Cold War America (Cambridge, MA: MIT Press, 1996).

4 Peter Fritzsche, A Nation of Fliers: German Aviation and the Popular Imagination (Cambridge, MA: Harvard University Press, 1992); Joseph J. Com, The Winged Gospel: America’s Romance with Aviation, 1900-1950 (New York; (Oxford University Press, 1983).

The propulsion efficiency advantage of turbofans was well-known nearly as long as turbojets themselves. In 1936, before he actually built a working turbojet, Frank Whittle patented a scheme to compress more air than was necessary for the turbine and to force it rearwards as a cold jet. Whittle wished to “gear down the jet” to make it more efficient, maintaining the overall mass-flow while reducing exhaust velocity.10 During the next decade, as Whittle developed the first successful turbojets, he patented several other configurations of bypass engines, including ones with a fan both fore and aft of the rest of the engine (he did not use the term ‘fan’ or ‘bypass’ for any of these designs).11

Whittle was not alone among the British in putting preliminary designs of bypass engines on paper. A. A. Griffith of Rolls-Royce devised a multistage axial fan in 1941.12 Figure 4 shows a cutaway of a Metropolitan Vickers turbofan engine from just after World War II in which the fan, consisting of two counter-rotating stages, is located downstream of the core engine, using its exhaust to drive turbine stages to which the fan blades are connected. Figure 5 shows a drawing of a De Havilland bypass engine in which the flow leaving the last stage of the axial compressor is split, with the outer portion bypassing the rest of the core engine and the inner portion proceeding on to a centrifugal compressor, then a combustor, and finally a pair of turbines. We have been unable to determine whether either of these engines was ever built and tested and, if they were, why they died in their infancy.13 Counter-rotating stages are notoriously difficult to make work in anything but the

precise conditions for which they were designed – a significant drawback for an operational engine. The De Havilland engine, however, did not reach so far beyond the state of the art. From the perspective of hindsight, the main question about it is whether its compressors, combustor, and turbines performed well enough to provide the energy demanded by the bypass flow in its axial compressor.

These two British engines call attention to one of the two fundamental problems in designing practical bypass engines capable of realizing their theoretical promise. For high-subsonic flight the bypass flow needs to be pressurized to a level around 1.5 times the inlet pressure. The De Havilland design employed 6 axial compressor stages to achieve the requisite pressure in the bypass stream. The Metro-Vick design used counter-rotating stages to try to achieve the requisite pressure in merely two stages, saving weight, but with the risk of being unable to coordinate the flow in the two stages. Thus, one fundamental problem in designing a bypass engine for high-subsonic flight was to achieve the needed pressure rise in the bypass stream without incurring an excessive weight penalty. The later successful turbofan engines shown in Figure 2 used an aerodynamic design technology that did not exist in the late 1940s.

The other fundamental problem in designing a bypass engine was the need for more powerful core engines. The greater the bypass airflow, the more energy that is needed to pressurize it. The core engine must generate this energy using only the air passing through it. Whether the overall engine is a turboprop, turbofan, or turbojet, its core engine consists of a gas generator that converts chemical into mechanical energy. One of the basic performance parameters of gas generators is called specific-power – the power produced per unit of airflow. The specific-power of the aircraft gas turbines of the late 1940s was low, limiting the amount of bypass airflow. As a consequence the most anyone could even hope to achieve in a bypass engine at the time was a small incremental gain over turboprops or turbojets.

Realizing the promise of bypass engines required core engines with significantly higher specific-power. Higher specific-power calls for higher overall engine compression ratios.14 In other words, to make a working bypass engine, the core engine compressor had to achieve markedly higher pressures than the engines of the late 1940s were able to do.

The State of Axial Fan and Compressor Technology These two problems share the common demand of achieving a pressure-ratio, in the one case across a fan and in the other across a compressor. An axial fan stage, however, amounts to nothing but an axial compressor stage. An axial compressor stage consists of a row (or cascade) of rotating blades followed by a row of stationary blades, as shown schematically in Figure 6. Energy is added to the flow in the rotating blade row, while the stationary blade row redirects the flow and recovers the kinetic energy imparted by the rotor, in the process converting the velocity head into pressure. In contrast to a turbine stage, a compressor stage tries to make air do something that it does not want to do, namely flow against an opposing or adverse pressure gradient. The effects of the adverse pressure gradient ultimately limit the pressure-ratio that can be achieved in a single stage; above this limiting

point, which varies from one airfoil type to another, irreversible thermodynamic losses become excessive. This is why the axial compressors in the engines shown in the earlier figures all had several consecutive stages. It is also why more than one stage was used to pressurize the bypass flow in both the De Havilland and the Metro-Vick engines.

Despite its critical role, axial compressor technology was in its infancy in the 1940s. Not only was the pressure-ratio that could be achieved in any one stage quite low, but also “many early axial compressors worked more as stirring devices”15 instead of achieving compression. Although a base point in axial compressor design technology had emerged in 1945, lending some rationality to the design process, designers remained restricted in the performance demands they could place on the compressor.16 These restrictions in turn limited the performance that one might hope to achieve in a bypass engine by limiting both the pressure-ratio per stage achievable in a fan and the specific-power achievable in the core engine. These same restrictions were limiting the performance of turbojet engines as well. The military was rapidly converting to turbojet-powered aircraft in the late 1940s, with increasing emphasis on supersonic flight. Turbojets for supersonic flight required higher specific-power than the turbojets already flying were achieving.

Because of its role in dictating performance limitations, no component received more research and development effort between 1945 and 1955 than the axial compressor. This effort had three goals: (1) to achieve considerably higher overall compressor pressure-ratios at high thermodynamic efficiency; (2) to increase the predictability of axial compressors, especially at off-design operating conditions, so that fewer compressor designs would turn out to be unacceptable on test; and (3) to increase the pressure-ratio achievable in a single stage so that higher overall compression ratios could be achieved without exacting a penalty in the thrust-to – weight ratio of the engine.17 Although most of this research and development effort was applicable to fans as much as to compressors, the turbofan engine largely disappeared from view during these years. R&D funds went into developing better turbojets, not into transforming the promise of the bypass concept into successful engines.

From the perspective of hindsight, however, this was appropriate even from the point of view of the bypass engine, for the gains that were achieved in gas generator performance in the late 1940s and early 1950s ended up contributing crucially to the first turbofan engines to enter flight service. Moreover, as we shall see below, the advances that were made in compressor aerodynamic design technology during these same years contributed no less crucially to the aerodynamic design of the fans of these engines.

With these questions in mind, we ask, why did the turbofan engine, once it emerged, so totally dominate commercial aviation? P&W’s JT8D low-bypass turbofan engine, which went into service in 1964, is still powering Douglas’s DC-9 and Boeing’s 727 and 737. High-bypass turbofans, like P&W’s JT9D, GE’s CF6, and Rolls-Royce’s RB.211, have powered virtually all wide-body aircraft since the late 1960s. (The high-bypass turbofans required once more the same sort of steps in core-engine specific-power and fan tip Mach number as the initial low-bypass engines had required, and hence they need a separate analysis.85) The economics of the turbofan engine helped shape commercial jet aviation and stabilize it technologically and economically, putting air travel within the reach of a much larger segment of the public than it would otherwise have been. In other words, the turbofan engine has dominated high-subsonic flight because these two were mutually constitutive and emerged in parallel. Until the latter became important, the former did not make sense, technically or economically.

The turbofan responded to the decline of the notion that commercial jet flight would continually progress along the axis of speed. Much of the technology underlying turbofans had developed for entirely different purposes. Compressors received a great deal of attention in both industry and government, but none of that effort specifically sought a turbofan; it focused on turbojets. Immediately after World War II it seemed obvious that the continued progress of commercial flight would move, like military flight, toward higher and higher speeds. The only real customer for aircraft gas turbine engines before the mid-1950s, especially in the U. S., was the military, and they rightly pursued speed, and hence supersonic flight, above all else. More than a decade of supersonic flight and jet engines were required before it became clear that commercial air travel would follow many pathways, but increasing speed would not be one of them. Until the late 1950s, engineers simply did not see high-subsonic flight as a technical, or commercial, frontier. (Military flight leveled in speed as well: the aircraft that holds the world speed record, even today, was developed in the years just before and after 1960.) High-subsonic jet flight emerged as a dominant category, and ever increasing speed declined in importance as a category of problems, simultaneously with GE’s and P&W’s efforts to develop turbofan engines. Progress scarcely came to an end at this point, however.

The turbofan episode illustrates a dramatic, yet subtle shifting, we might even say a turning, in the parameters of progress in the narrative of aviation. The ever – increasing advance of the raw, physical parameter of speed ended in the 1950s, as commercial aviation settled into the high-subsonic regime. As an indicator of this shift, consider the proliferation of performance parameters in this story: stage pressure-ratio, thrust-to-weight ratio, propulsion efficiency, specific fuel consumption, cost per passenger mile. Significant progress was made in each of these measures with the emergence of the turbofan and in the years since, but they are less visible to the naked eye, less viscerally physical than speed. (An engineer, though, might argue that thrust-to-weight ratio is as “natural” a physical parameter as Newtonian mass and velocity.) Today’s airliners, to the untrained eye, look much like the 707 of four decades ago; for comparison, consider that forty years before the 707 were the biplanes of World War I. Of course, appearance is misleading. Stability in configuration masks substantial changes in engines (as we have shown), as well as in wing design, materials, control systems, and numerous other systems. Hence, the progress narrative in commercial aviation remains, but embedded in newer, seemingly more artificial measures that define “success” for advanced technologies, measures that embody social assumptions in machinery. The significance of the turbofan engine, and its intricate history, derives from this turning: from outward parameters of physics to internal parameters of systems.

This turning is evident not only in the broad parameters which evaluate aircraft performance, but also in the fine-grained texture of engineering practice. Engineers, in the story we have told, relied heavily on non-dimensional parameters of performance. Vincenti has characterized such “dimensionless groups” as useful in relating the performance of models to the performance of working prototypes.86 We here identify two additional categories of such parameters. One, typified by the diffusion factor, provided independent variables for empirical correlations. Such parameters enable a great deal of complexity to be digested into a form that allows designers to interpolate and extrapolate reliably from past experience. Another category consisted of performance parameters like the pressure-ratio and efficiency of compressor and fan stages and the thrust-to-weight ratio and specific fuel consumption of engines. These parameters provide a generic way of characterizing the state of the art and advances in it; by decoupling issues of performance from issues of implementation, they allow such thoroughly different approaches to turbofan design as GE’s and P&W’s to be meaningfully compared. One way in which engineering research has contributed to the turbofan has been through identifying and honing parameters that enable past successes to be repeated and that open the way to processes of continuous improvement.