Normal Design.

n.a., Paris dans 20 ans, 1967 (via NDLR).

But focus on technology as knowledge has ramifications beyond the science-technology question. Hugh Aitken, for example, makes it basic to the historical method adopted in his book The Continuous Wave. To recount the early technical and institutional history of radio, Aitken regards "history of technology as one branch of intellectual history or the history of ideas." From this approach, he explains the origins of the history of inventions crucial to radio by examining "the flows of information that converged at the point and at the time when the new combinations came into existence." As the work of Aitken and other historians makes clear, however, the ideas we deal with are not disembodied - they are, as Layton points out, the ideas of people (and communities of people). Emphasis on knowledge thus brings history of technology into symbiotic relation, not only with intellectual history and philosophy, but with social history and sociology as well. Such emphasis is critical, in particular, for understanding technological change, a fundamental concern in one way or another for all these disciplines. As remarked by Rachel Laudan, "shifts in the knowledge of the practicioners play a crucial role in technological development." People who aspire to understand such development - economists and policy makers, for instance - might do well to focus accordingly when they delve (in Rosenberg's graphic phrase) "inside the black box" of technology. If these ramifications are valid, as I believe they are, laying out the features of engineering knowledge very much needs doing.

In addressing this task, I will structure the inquiry around the goal of design. For engineers, in contrast to scientists, knowledge is not an end in itself or the central objective of their profession. Rather, it is, as illustrated by the quotation from the British engineer, a means to a utilitarian end - actually, several ends. Engineering can, in fact, be defined in terms of these ends, as in the following quotation from another British engineer, C.F.C. Rogers:

Engineering refers to the practice of organizing the design and construction (and, I would add, operation) of any artifice which transforms the physical world around us to meet some recognized need.

Here I take "organize" to be meant in the sense of "bring into being" or "get together" or "arrange". The first end, "design", has to do with the plans from which the artifice is built, as in the many drawings (or computer displays) of an airplane and its components. "Construction" (which I shall call "production") denotes the process by which these plans are translated into the concrete artifice, as in manufacture of the actual airplane. "Operation" deals with the employment of the artifice in meeting the recognized need, the related example being the maintenance and flight operations of the airplanes of an airline. Definitions of engineering sometimes mention other ends such as "development," and "applications" or "sales"; these can usually be subsumed under one of the foregoing three, which will be sufficient for present purposes.

Of the three, design is frequently taken as central. Layton, in treating technology as knowledge, takes it as such (with minor mention of other ends). He adds in a later paper, however, that recent attempts among engineers to "reestablish design as the central theme of engineering" are "not without ideological overtones." Other scholars contend that rhetorical emphasis on design by engineers is primarily an attempt to gain status, that "engineers have seized on design as a way to liken their activity to that of scientists, to assert that they too are engaged in creative activity." Whatever the truth of the situation, I will restrict my focus here almost entirely to design. To attempt more would extend impractically an already lengthy study. Great numbers of engineers do, in fact, engage in design, and it is there that requirements for much engineering knowledge originate in an immediately technical sense. Though extaengineering needs - economic, military, social, or personal - may set the original problem, for many workaday engineers things come into focus at the level of concrete design. My emphasis on design, however, should not be taken to imply anything derogatory about other areas of engineering. For a complete epistemology of engineering, production and operation will require equal attention. For the time being, however, my concern will be limited to engineering design knowledge.

"Design," of course, denotes both the content of a set of plans (as in "the design for a new airplane") and the process by which those plans are produced. In the latter meaning, it typically involves tentative layout (or layouts) of the arrangement and dimensions of the artifice, checking of the candidate device by mathematical analysis or experimental test to see if it does the required job, and modifications when (as commonly happens at first) it does not. Such procedure usually requires several iterations before finally dimensioned plans can be released for production. Events in the doing are also more complicated than such a brief outline suggests. Numerous difficult trade-offs may be required, calling for decisions on the basis of incomplete or uncertain knowledge. If available knowledge is inadequate, special research may have to be undertaken. The process is a complicated and fascinating one that needs more historical analysis than it has received.

Design is important here, however, mainly as it conditions the knowledge required for its performance. Knowledge itself forms the primary focus; while requirements from design must be kept in mind at all times as determining that knowledge, details of how the process takes place are secondary. I have never attempted to design an airplane in my entire career as a research engineer (though I participated in planning and designing large aeronautical research facilities). The atmosphere  in which I worked, however, and the knowledge I helped produce, were conditioned by the needs of airplane designers who visited our laboratory. My colleagues and I were keenly and continuously aware of the practical purposes we served. The situation in this book is somewhat similar. Though only one of the historical studies deals directly with the design process, the needs of design play a determining role throughout. 

To keep matters manageable, I shall further limit attention to what can be called normal design. In The Origins of the Turbojet Revolution, Edward Constant defined "normal technology" - "what technological communities usually do" - as comprising "the improvement of the accepted tradition or its application under 'new or more stringent conditions.'" Normal design (my extension, not Constant's) is then the design involved in such normal technology. The engineer engaged in such design knows at the outset how the device in question works, what are its customary features, and that, if properly designed along such lines, it has good likelihood of accomplishing the desired task. A designer of a normal aircraft engine prior to the turbojet, for example, took it for granted that the engine should be piston driven by a gasoline-fueled, four-stroke, internal-combustion cycle. The arrangement of cylinders for a high-powered engine would also be taken as given (radial if air-cooled and in linear banks if liquid-cooled). So also would other, less obvious features (e.g., tappet as against, say, sleeve valves). The designer was familiar with engines of this sort and knew they had a long tradition of success. The design problem - often highly demanding within its limits - was one of improvement in the direction of decreased weight and fuel consumption or increased power output or both. Normal design is thus very different from radical design, such as that confronting the initiators of the turbojet revolution described by Constant. The protagonists of that revolution had little to take for granted in the way that designers of normal engines could. In radical design, how the device should be arranged or even how it works are largely unknown. The designer has never seen such a device before and has no presumption of success. The problem is to design something that will function well enough to warrant further development.

Though less conspicuous than radical design, normal design makes up by far the bulk of day-to-day engineering enterprise. The vast design offices at firms like Boeing, General Motors, and Bechtel engage mainly in such activity. In the words of one reader of this material, "For every Kelly Johnson (a highly innovative American airplaine designer who will figure in chapter 3) there are thousands of useful and productive engineers designing from combinations of off-the-shelf technologies that are then tested, adjusted, and refined until they work satisfactorily." In addition, knowledge for normal design is more circumscribed and easier to deal with. Though it may entail novelty and invention in considerable degree, it is not crucially identified with originality in the same way as knowledge for radical design. My restriction to normal design thus related to both substance and expedience - there are sufficient matters of importance to confront at this stage without opening the Pandora's box of technical invention.

I do not mean to suggest that normal and radical design, and the knowledge they require, can be sharply separated; there are obviously middle levels of novelty where the distinction is difficult to make. The difference, nevertheless, is sufficiently real to serve as a basis for analysis. I likewise do not mean to suggest that normal design is routine and deductive and essentially static. Like technology as a whole, it is creative and constructive and changes over time as designers pursue ever more ambitious goals. The changes, however, are incremental instead of essential; normal design is evolutionary rather than revolutionary. As we shall see, even within such limits the kinds of knowledge required are enormously diverse and complex. The activities that produce the knowledge, unlike the activity it is intended to support, are also something for from normal and day-to-day. 

W.G. Vincenti, What Engineers Know and How They Know It, Edition : Reprint. Baltimore: John Hopkins University Press, 1993, 5-9.