Category Archimedes

Archibald Black was just one engineering consultant, and one advocate, or even a handful, does not a community of experts make. The aeronautical engineering community had begun to sprout small clusters of “experts” located in the university, industry, and the government. But with the exception of the Model Airways project of the Army, emphasis among engineers was almost entirely on airplanes.30 The powerful political currents swirling around the aviation legislation debates of this period had finally reached a consensus that the federal government had a leading role in stimulating and supporting the development of both military and civil aviation. Through the Air Commerce Act of 1926, Congress put most of the responsibility on the shoulders of the Commerce Department. With regards to airport development, Congress placed a severe handicap on the new Aeronautics Branch. The Air Commerce Act of 1926 expressly prohibited the Commerce Department from providing any financial support for airports. Yet despite having no financial resources or regulatory powers, Congress still included a specific provision in the law requiring the Commerce Department to examine and rate airports.31

Fulfillment of this obligation was not considered a burden, although without the power to mandate that all airport facilities participate in a ratings program the law lacked much punch. Still, the Aeronautics Branch was established amidst the heady intellectual fervor of “Fordism” and “mass production.” Commerce Secretary Herbert Hoover was a leading proponent of standardization in all industries so it is not surprising that department officials would place heavy emphasis on standardization as a crucial first step in transforming commercial aviation into a large scale transportation system. The Airport Rating program, one small part of a much larger regulatory program being initiated by the Department, was animated by similar standardization objectives. Airport Ratings helped ensconce airport engineers as the primary technical experts and deeply influenced the process and outcome of airport design. Thus even without the power of the purse, the Aeronautics Branch managed to become an incubator for the professionalization of airport design.32

The ratings, introduced in 1927, represented neither original nor dramatic reading. The crucial fact was that there was now a single coordinating body in the nation.33 Compliance was strictly voluntary but the Aeronautics Branch had now asserted a role in defining, what Lester Gardner called in his speech to the Fourth International Congress of Aerial Navigation in 1927, “airport excellence.”34 The new federal standards were largely identical with those of the Aeronautic Safety

Code. They included a set of basic minimum requirements for every field under consideration for a rating. The ratings scheme established borrowed the highway engineer’s “stage construction” practice meaning that they allowed for construction to proceed in “stages.”35 This helped address the fact that, because airport construction had been deemed a municipal function, individual airports were never going to be identical. As the Army had discovered, communities did not have the same financial resources or the same degree of interest. But more importantly, the air transportation companies found that 100 percent uniformity was unnecessary – air travel was clearly heavier between certain destinations for reasons independent of the quality of the airport. The primary concern for federal officials, then, was to provide a base-level of uniformity.

The ratings system was greeted warmly but ironically no airports made an application until 1930. The reason was that the system was voluntary. Austin MacDonald summed up the situation as follows: “Those responsible for the destiny of an airport are usually disinclined to accept anything less than the very highest rating issued. Rather than be branded as inferior, they are likely to defer their rating application, hoping that at some future time they will be able to meet all requirements and receive the unqualified approval of the Federal Government.”36 Still the effect of Airport Ratings was almost immediately apparent in airport design.

A stunning example was the Oakland, California, Municipal Airport which was a carbon-copy of the Commerce Department specifications. Oakland was the first major airport designed and built after the Aeronautics Branch had developed its airport ratings. Opening in 1928, in every aspect of its design – from drain tile and grass seed mixtures to hangars, lighting and hospitals, even the painted markings on the building rooftops – the Oakland airport conformed to the specifications listed in the standards for the highest airport rating. Even its physical layout was identical with the sketches of a model airport supplied along with the airport ratings. Oakland’s subsequent success as a working facility became strong testimony on behalf of the “engineered” airport. As an airport construction boom stimulated by Lindbergh’s epochal solo Atlantic crossing got underway, letters began to pour in to the Aeronautics Branch requesting advice on how to locate an airport engineer.37

Unlike the engineers who were involved in aircraft design, there was no laboratory or university environment in which the merits of different kinds of designs could be debated. There was only a very limited public discussion stimulated by the articles which appeared in various journals. When the Branch formed a special Airports Section in February 1929, one of the central functions of the new section was to become a clearing house of technical information (although there was no promise to provide any critical analysis of that information before dissemination). The ranks of airport engineers swelled and an examination of all airports built during this period clearly indicates that there was a general consensus as to what constituted “good” design versus “poor” design.38

Three factors were considered when making such judgments. First and foremost was pilot opinion coupled with the accident rate at a given field. Traffic volume was the second measure. Finally, profitability (or at least the ability to break even) was used to evaluate airport design. The consensus built around these indicators was strengthened with the establishment of professional organizations dedicated to airports. In May 1929 the Aeronautical Chamber of Commerce’s new Airport Section sponsored the first national airport meeting in Cleveland. Over three-hundred attended the Ohio meeting and another three – hundred attended the five regional conferences held in Boston, Atlanta, Los Angeles, and Bridgeport. Somewhat immodestly, though true, the Chamber concluded that “the minutes of the meeting and records of the papers read constitute a compendium of thought and experience on airport development from the best minds in the field.”39

But amidst this expanding professional interest, airport engineers suddenly became aware of a challenge to their fledgling claims of expertise. This challenge appeared not to question the engineer’s skill but rather it resulted from a renewed professional interest within the American architectural community for airports and airport design. City planners, too, began to take a vocal interest in airports. While ultimately it would be understood that airport design was sufficiently complex to require the skills of several different professionals, this was not true at the start.

Yet, airport engineers did not take long to concede publicly that there was a role for architects in the design of certain airport buildings. Philip Love of Love-Sultan, stated in a paper for the Third National Meeting of the Aeronautic Division of the American Society of Mechanical Engineers that: “At first, airport buildings were hard to treat architecturally, but a definite type of characteristic “airport” design is coming to the fore rapidly, and we are learning that sympathetic treatment of mass and color will give buildings a really pleasing appearance without exorbitant cost, and the whole industry has ascended to a plane where this is not only justified but demanded.”40 That nervous acknowledgment came at an important turning point in the next phase of airport design – the integration of architects into the community of experts that designed airports.

At the end of World War I, a British Design Panel had been formed to investigate stress and aerofoil performance.44 The Panel’s main concern soon came to focus on scale effect. At its second meeting, after a long discussion, the Panel concluded that the scale effect was important. The Panel decided to state its own opinion formally as soon as possible.45 An RAE group under Wood summarized the relevant experimental research on this subject.46 Wood’s preliminary report noted a considerable difference between full-scale and model data for lift, drag, and center of pressure. It was decided, however, to defer a final recommendation while awaiting the arrival of still more comprehensive data.

After a year of preparation, the RAE group submitted its conclusions on scale effect in February 1923.47 By then, Glauert was actively introducing German aerodynamic theory and the International Trials were taking place. The RAE report included Prandtl corrections to its research data. This application triggered a heated debate first with the Design Panel and then with the Aerodynamics subcommittee. Introducing the RAE report as a part of the general investigation into the scale effect, Panel Chairman William S. Farren highlighted this first use of Prandtl corrections by British researchers. Farren himself was not in favor of the correction, because he considered it scientifically more desirable to compare results of full-scale testing with those of wind tunnel testing modified only through “purely experimental corrections.” Before the meeting, he had consulted two Main Committee members on this matter, and reported their disapproval of the correction to his own Panel members.48 Farren clearly recognized that the question concerned a fundamental principle of experimental procedure.

In response to the Chairman’s comment, Wood stated that the Prandtl correction had already been confirmed by the International Trials and was regarded by the RAE as part of routine wind tunnel experiments. Glauert agreed with Wood, and cited as a parallel case those corrections due to the interference of wires, which had long been regarded as valid. But their arguments were not sufficiently persuasive. R. V. Southwell, Superintendent of the Aerodynamics Department of the NPL, contended that the Prandtl correction should have been applied in a different section of the report. Of the four sections of the RAE report, the first two dealt with results of full-scale and model experiments, the third with the comparison of these two results, and the last with some applications of Prandtl’s theory. He suggested that Prandtl corrections should have been used and discussed in Part 3 instead of Part 2. He added that the NPL would soon be in a position to confirm experimentally the values given for the correction.

The Design Panel deferred judgment on the validity of the application of the Prandtl correction.49 The Aerodynamics subcommittee discussed the matter the following month.50 Despite the Chairman’s initial comment that the application of the Prandtl correction was already standard practice at foreign laboratories, most members of the subcommittee disagreed with the manner of presentation employed by the RAE group. These scientists, including Bairstow, Farren, Jones, and Glazebrook were all emphatically of the opinion that it was undesirable to give figures to which “purely theoretical corrections” have applied. Corrections to raw data were sometimes made, they argued, but “such correction was based upon actual observations, and was not of the same nature as the Prandtl correction.” Southwell called attention to the fact that the application of the Prandtl correction was not yet standard practice at the NPL. He announced that their on-going experiment on a biplane in the four-foot wind tunnel could check the validity of this correction.

Lacking Glauert’s support, Wood’s argument in defense of the Prandtl correction was insufficient to persuade all these critics. He merely mentioned that the correction for tunnel walls was usually made in experiments on propellers. Finally, on the chairman’s motion, the following recommendation was approved: the general practice should be to give the actual results both in the form of figures and tables, while results to which the Prandtl correction had been applied could also be added at the discretion of the authors. Further discussion of the validity of the Prandtl correction was postponed until results were obtained from the NPL experiments.

Two months later, however, Southwell wrote to the ARC Secretary that the NPL was not yet in a position to provide decisive results. He asked that the Committee discuss this matter during the summer vacation so that the NPL staff could initiate the program promptly in the fall. Following his request, the Aerodynamics subcommittee decided to initiate two types of experimental investigations, both intended to test experimentally the accuracy of the Prandtl correction.51 The first experiment involved testing a model in both a four-foot and a seven-foot wind tunnel so as to determine the difference in results due to the interference of the tunnel walls. The second experiment was to visualize the air flow behind airfoils of different spans in order to determine to what extent Prandtl’s theory was “substantiated.”52

Based on the results of the NPL testing, Glauert submitted a report in November entitled “Experimental Tests of the Vortex Theory of Aerofoils.”53 The report concluded that the NPL results experimentally confirmed the accuracy of the Prandtl correction when applied to wind tunnel results on certain wings. The agreement between tests done in wind tunnels of different size when the Prandtl correction was applied was indeed much more striking than had been the case with the French results in the International Trials report. At the subcommittee meeting, these positive results impressed every member.

Yet some reservations continued to be expressed. G. I. Taylor questioned the scientific grounds of this confirmation, asking whether the effect was due to circulation or to the eddying of air around the airfoil. Taylor was asked by the chairman to discuss this matter with the NPL staff.54 The next month, Taylor submitted a paper dealing with this question and with Glauert’s treatment of Prandtl’s circulation theory.55 At the beginning of Glauert’s paper, Glauert had mentioned experimental confirmation very briefly. He cited the measurement of air flow around an airfoil at the NPL, showing that the circulation around the airfoil was independent of the area of the chosen contour; its value was very close to the theoretical value. In discussing this argument, Taylor pointed out in his report that if the contour was selected in a special way, the experimental results cited by Glauert would be obtained no matter whether resulting from the circulatory flow or the discontinuous stream flow. The observed results, therefore, could not be taken as confirmation of the physical hypothesis of Prandtl’s theory. As Taylor stated, his discussion was intended to “see how far evidence of this kind may be taken as confirmatory of Prandtl’s theory,” and added that his comments were “very probably well known to followers of the work of the Prandtl school.”56

After Taylor’s brief comment at the Aerodynamics subcommittee meeting, Bairstow and Horace Lamb expressed their own doubts, stating that they were not certain that the corrections calculated by the Prandtl theory were really accurate. They therefore considered it undesirable to change the method of presentation of wind tunnel results decided upon at the July meeting. Wood responded by referring to analogous corrections which were made for experiments of propellers and airships in wind tunnels of different sizes. Bairstow then made a proposal on the manner of presentation, which was seconded by Lamb. According to this proposal, the following method should be followed:

1. The numerical results of wind tunnel tests should be presented without the Prandtl correction.

2. A statement should be made as to the amount of the Prandtl correction.

3. The diagrams should be drawn from the results obtained after applying the Prandtl correction.57

Farren and Jones, both faculty members at Cambridge University’s Aeronautical Department, suggested that the proposal be amended so that instead of the old method as prescribed in the first term, the numerical results would be presented in a form to which the Prandtl correction was already applied. Farren and Jones thus changed their view on the Prandtl correction, and came to side with Wood and Glauert. Bairstow then slightly modified their proposal so that numerical results without the Prandtl correction were presented together with additional columns containing the same results with the Prandtl correction applied.

The result of the vote was very close, seven to six in favor of Farren’s and Jones’s amendment. The Aerodynamics subcommittee thus agreed to recommend to the Main Committee the following method of presentation:

The authors of reports describing wind tunnel tests should present their results… in a form after the Prandtl correction was applied. A statement would also need to be added as to the amount of the Prandtl correction.58 Glauert’s report was approved for publication.

Shortly afterwards, the Design Panel convened to discuss what manner of presentation it would use for its final report on scale effect. Southwell expressed his strong opinion on “the necessity for dispelling any impression that the Committee thought scale effect should be zero.”59 It was obvious to every Committee member that the statement was a criticism of the previous report of the “Scale Effect” subcommittee and of Bairstow, who had insisted on the insignificance of the scale effect as well as the inclusion of an explicit statement on such evaluation in its final report. Following Southwell’s suggestion, the Design Panel decided to include a brief history of the problem in its final report, pointing out that the application of the Prandtl correction caused “a marked improvement in agreement” between full-scale and wind tunnel tests.60 The controversy over the scale effect was finally settled.

A few years later, the Scale Effect Panel was formed. This time, the scale effect was not enclosed in quotation marks. Ironically, Bairstow was selected for its chairman.61 The task assigned to the panel was twofold: to study the scale effect as well as to examine the advantages of the use of a variable-density wind tunnel. This new type of wind tunnel had been developed by the NACA to reduce the scale effect.62 The tunnel was placed inside an air tight tank to create an aerodynamic condition with the same Reynolds number as in full-scale flight. The construction of this wind tunnel was based on the realization that the scale effect was now a significant factor to be taken into account. The panel was unanimous in recommending the construction of this new wind tunnel, and submitted the conclusion that it be constructed as a project for the program of 1928-29.63 The Main Committee sanctioned the project.

During the summer of 1928, D. R. Lane, a staffer for the new trade publication Airports, made an extensive survey of airports between San Francisco and Chicago. In an article about the trip, he wrote: “On this journey only three airports were seen at which there were real provisions for passengers to wait in comfort for the arrival of planes. These were the ports of San Francisco, Oakland and Detroit (Ford Airport) where there are comfortable waiting rooms in the administration buildings.”41 Of the three, Lane asserted that the terminal building at the Ford Airport was “probably the best airplane passenger station yet built in America.”42 That assessment was often repeated during the next couple of years including in Domestic Air News, the Aeronautics Branch’s bi-monthly publication which published an article that stated unequivocally: “The Ford Airport at Dearborn is one of the few real airports worthy of the name at present in operation in this country.”43

The Ford Terminal, which opened in November 1927, was a two story square white brick building with Spanish tile roof. Almost the entire 2,700 square feet of the first floor was given over to a passenger waiting room. The second floor, which was smaller than the first, housed the offices of Ford Air Transport Service and Stout Air Service. The most admired feature of the building was its wrap­around balcony from which visitors could watch all the action on the field. Pictures and various reports suggest that the passenger space was considered very comfortable with armchairs, tables, and separate lavatories for men and women. Lane made a special effort to point out this last feature, noting that it was “embarrassing to a woman passenger to be required to pass through a hangar where mechanics are at work.”44

There are two things which are historically important about the Ford Airport Terminal building. First, was the fact that it won rave reviews throughout the industry.45 Second, was that the building was designed by an architect. Henry Ford’s main concern was that his airport always be thought of as the best airport. The new business of carrying passengers did not automatically require the construction of a terminal; prior to the 1930s, most passengers simply walked from the airplane into the hanger or administrative offices. Ford Airport did not have even these facilities; it abutted two factory buildings. In fact, when the airport was first opened, passenger-carrying and exhibition flights required special advanced permission. The addition of regular passenger service to the mail service originating from Ford Airport changed this. Henry Ford encouraged those running day-to-day operations at the airport to stay abreast of new developments.46

Supplying a special building for passengers was one of those “new things” that needed to be provided for. However, Ford did not turn to an engineer to design the facility. Nor did he consult with the many ex-Army pilots in his employ. He turned to an architect. Henry Ford was not the first to employ an architect to design an airport building. However, the extremely high profile of the Ford Airport meant that developments taking place in Dearborn were viewed as bellwethers by the aviation community.47

In April 1928, two editorials about airports and architecture appeared – one in Scientific American and the other in the debut issue of Airports. The Airports editorial argued eloquently that “Aviation has found its niche in the activities of man. The airport is a potent factor in aviation’s success. A definite program of design and construction must be followed if we are to build our airports for posterity.”48 Alexander Klemin, writing his debut column on new development in aviation for Scientific American, stated: “We are apt to think of an airport as a large landing field with a group of ugly looking hangars at one end, a runway or two and a system of lighting.”49 Both pieces concluded with a call for an international architectural competition. However, while Klemin (who was greatly impressed by the results of two such competitions in England and Germany) thought this was a great solution to encourage American architects to become interested in airport design, the editors of Airports were more timid in advancing their idea. “There must be many Chambers of Commerce, municipal authorities and private individuals,” they wrote, “who will look with favor upon a plan of this kind. Others may deem it premature, destructive and incongruous.” The final question the editors posed to readers was: “Should it [employing architects to design airports] be encouraged?”50

Architects, no less affected than other Americans by the Lindbergh frenzy, seemed to need little encouragement. In May 1929, Architectural Record published “Airport Design and Construction,” a lengthy feature article by Robert L. Davison.51 Davison’s purpose was to summarize the state-of-the-art as well as to suggest the fundamental principles which would govern an architectural approach to the problem of airport design. While he believed that the flying field was still the province of the engineer, Davison claimed the buildings for the architect. Thus, Davison’s article was largely a primer in aeronautics – incorporating the Department of Commerce airport rating requirements, specifications of airplanes, design information about existing airports, and so forth. And even though the basic facts about aviation and airports constituted nothing new, Davison’s piece was unlike anything ever produced by airport engineers.

One key difference between the architectural and engineering approach to airport development was centered in the design process. Both architects and engineers found it necessary to make assumptions. Among practicing airport engineers, however, assumptions often remained unstated. For example, both architects and engineers discuss the problem of selecting a good site for an airport. Both give extensive descriptions of various features which must be considered before picking a site. Yet almost all of the articles written by engineers are seemingly diffuse. Gavin Hadden wrote that: “It is impossible to describe an exact set of conditions which will govern every airport design. The natural conditions alone – geographical, topographical, meteorological – present widely differing influences on specific problems and if to these are added the manmade conditions, which affect every site and its requirements, and which will further affect present requirements and future predictions, the variations may be multiplied many times.”52

Davison, by contrast, presented a short, succinct listing of requirements – for the flyer and the public. Each item on the list was assigned a point value. To pick a site, one simply checked each item on the list, assigned a value (up to the maximum assigned to that item) and then tallied up the total points. For example, “freedom from dense river fogs” was equal to an “8” so a value might range from “0” (always fogged in) to “8” (never subject to fogs). On the surface, Davison’s table may seem the more rigorously analytical of the two. Yet, the procedural difference between Hadden and Davison was actually a function of priority. Site selection was one of the most important problems of the entire design process for engineers, but far less so for architects. This was because airport engineers were almost exclusively preoccupied with the problems of safe take-offs and landing. Architects were focused on the new problem of transfer – the shifting of passengers and cargo from one mode of transportation to another.53

The story recounted here was, in sum, about the success and the failure of Leonard Bairstow. The whole story turned on the scientific and technological significance of the key instrument for aeronautical research: the wind tunnel. Bairstow made full use of it, defended the validity of the data from it, and argued for the continuation of model research in it. He further promoted the attempt to standardize the performance of wind tunnels all over the world and to accord the NPL a central role. For all these efforts to connect the inside and the outside of the laboratory, I compared him to a laboratory director in Latour’s Science in Action and Pasteur in Pasteurization of France.

At first, Bairstow was exceptionally successful. His prewar stability research was applauded at home and abroad. Despite an American request, the British regarded it too important to disclose. Through such accomplishment, Bairstow attained fellowship in the Royal Society, served on the Air Board, and became Professor of Aeronautics at Imperial College. He became an extremely powerful figure in the British aeronautical community.

Bairstow’s position would have been further enhanced had the NPL model of wind tunnel research been standardized around the world. That was one object of the decade-long International Trials project. During this project, however, it turned out that Bairstow’s previous argument for ignoring the scale effect was called into question. Prandtl’s new aerodynamic theory challenged Bairstow’s position. French use of the Prandtl correction sparked a scientific debate on the validity of Prandtl’s aerodynamic theory. Acceptance of the Prandtl correction implied criticism of Bairstow, who had insisted on the negligibility of the scale effect.

While Bairstow served as an excellent middleman between theoretical scientists and practical engineers in conducting model research on stability, he failed to be such a middleman between Teddington and Famborough. He might have been more sensitive and generous to the full-scale experimenters at Famborough, initiating a theoretical and experimental research program on scale effect. Instead, he defended his model research like a lawyer at court by pointing out possible weaknesses in full-scale testing. Perhaps the wartime emergency and the position of the Air Board prevented him from taking a more discreet stance on this matter. In any event, he left himself open to later criticisms and repudiation. In the end, the renamed Scale Effect subcommittee approved the desirability of constructing a new variable-density wind tunnel developed by American engineers. This was a clear judgment that Bairstow had been wrong.

If we take Latour’s argument seriously, we could pose a question. Why did Prandtl’s theory prevail in the postwar world? From 1904, when he arrived at Gottingen, to 1918, the year of armistice, Prandtl succeeded, like Bairstow, in conducting aerodynamic research and expanding his research facilities. But after the war, he was placed in severely limited conditions on poor financial and material bases and with almost no communication with foreign investigators. Yet his aerodynamic theory soon won over aeronautical engineers all over the world. It was mainly not through Prandtl’s own effort but through the efforts of foreign engineers, and his disciple in the case of the United States, that his theory was accepted worldwide. In this connection, we could turn our attention to the RAE engineers who championed the introduction of Prandtl’s theory in Britain. In arguing for the validity of the German theory and specifically promoting the application of Prandtl correction, they succeeded in restoring the position held by their colleagues at Famborough in the wartime scale-effect controversy.64

Vandervoot Walsh, an assistant professor of architecture at Columbia wrote in 1931: “I suspect most engineers believe that the correct method of designing an airport is to let them lay the whole thing out, insuring its practicability: and then, if there is any money left, to call in an architect to spread a little trimming around on the outside of the buildings to make them look pretty.”54 Walsh felt that engineers believed that they could design an airport without an architect. The architect, suggested Walsh, did not share the same conviction about his own skills; the architect “understood” he could not design an airport without the help of an engineer.

Walsh was hardly arguing that an architect was superfluous, rather his article was a strongly-worded declaration of the architect’s rightful place in the design process. The value an architect provided was not in the “trimmings”; in fact, using an architect in this way was surely a waste of money according to Walsh. “Flying will never become generally popular until airports become more than merely practical and safe. They must affect the human emotions, establishing a mental state of ease through a feeling of comfort, safety and other emotions producing pleasure.”55

By the beginning of the 1930s, airport engineers embraced the idea that airport design should pay consideration to psychological factors. They agreed with the architects that the physical appearance of the airport help convey the image of permanence while disguising the very real discomforts and hazards of aviation. The question was to what degree and at which phase of the design process should they be incorporated. Further, there was no established mechanism for coordination between engineers and architects. As Walsh wrote, “practically no engineers have the training which architects have in the technique of keeping the planning in a very plastic condition, capable of quick changes as new and better ideas pass through the mind.”56 On the other hand, few architects understood the dynamics of airplanes and aircraft movement. Architects emphasized in their airport designs the idea of maximizing the functionality of the buildings; airport engineering design emphasized the functionality of the airplane.

It is important to keep in mind that airport design was more complicated than the design of a single facility. What becomes clear is that despite the assertions of the architect, both the architect and engineer were vitally interested in the problems of transfer. However, for the architect “transfer” was a local, small-scale phenomenon – how to get passengers between airplane and car, train, or bus. For the engineer, the problem of transfer was how to get passengers in and out of the air so that they could get from one airport to another.

There was no real resolution of competing claims for technical expertise over airport design in 1931 and 1932, just an acceptance that the amount of money being spent and the increase in passenger traffic had dictated a much more complex set of solutions to the problems of airport design. There was a consensus that airport design had to address two fundamental problems – takeoff-and-landing and transfer. As the matter of take-off and landing still was seen as the more pressing of the two problems, the engineers enjoyed the upper hand; but their visibility, if not their influence, was waning. Architects spoke more eloquently and effectively and captured public imagination. Architects proved much more adept at embedding the rhetoric of the American cultural ideals of progress and modernity in their descriptions of airport design. Again, Vandervoot Walsh provides a good (if lengthy) example:

Since we must admit that one of the grandest achievements of the human race is its newly acquired power to fly, then no airport is worthy of its existence if it does not express in its form the poetry of this great event. … There are others who say that the days of story-telling in archi­tecture are over, that all buildings have essentially become machines – cold, inhuman, efficient, doing their work with precision and speed. Let us hope, though, that the builders of airports will have a bigger vision than this, that engineers will realize that with human beings there is a spirit as well as body that must be satisfied. And that they will be willing to cooperate with architects to make these places of embarkation into the skies worthy of the great science of aviation.57

The reduced visibility of airport engineers was not really due to a lack of poetry but rather the fact that their profession was undergoing significant change. In 1931, Archibald Black expressed his concern for the “vanishing airport engineer” in a brief polemic published in The American City. Black was correct when he noted that there were fewer airport engineers but what was disappearing was the airport engineer who functioned in the same manner as the medical general practitioner – student of all the major airport systems but true expert in none. That airport engineer was about to be replaced by a new type – one more fully engaged in the technological problems of making an individual airport system function within a national system of airports and air transportation. That change was a direct consequence of the new involvement of architects in airport design.58

INTRODUCTION

The field of aerodynamics is frequently characterized as an applied science. This appellation is simplistic, and is somewhat misleading; it is not consistent with the engineering thought process so nicely described and interpreted by Vincenti.1 The intellectual understanding of aerodynamics, as well as the use of this understanding in the design of flight vehicles, has grown exponentially during the twentieth – century. How much of this growth can be called “science”? How much can be called “engineering”? How much falls into the grey area called “engineering science”? The purpose of this paper is to address these questions. Specifically, some highlights from the evolution of aerodynamics in the twentieth-century will be discussed from an historical viewpoint, and the nature of the intellectual thought processes associated with these highlights will be examined. These highlights are chosen from a much broader study of the history of aerodynamics carried out by the author.2

For the purpose of this paper, we shall make the distinction between the roles of science, engineering, and engineering science as follows.

Science: A study of the physical nature of the world and universe, where the desired end product is simply the acquisition of new knowledge for its own sake.

Engineering: The art of applying an autonomous form of knowledge for the purpose of designing and constructing an artifice to meet some recognized need.

Engineering Science: The acquisition of new knowledge for the specific purpose of qualitatively or quantitatively enhancing the process of designing and constructing an artifice.

These distinctions are basically consistent with those made by Vincenti.3

There is perhaps no better example of the blending of the disciplines of science, engineering science, and pure engineering than the evolution of modem aerodynamics. The present paper discusses this evolution in five steps: (1) the total lack of technology transfer of the basic science of fluid dynamics in the nineteenth century to the design of flying machines at that time (prior to 1891); (2) the reversal of this situation at the beginning of the twentieth century when academic science discovered the airplane, when the success of Lilienthal and the Wright brothers

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proved the feasibility of the flying machine, and when academicians such as Kutta and Joukowski developed the seminal circulation theory of lift and Prandtl introduced the concept of the boundary layer, all representing the introduction of engineering science to the study of aerodynamics (1891 – 1907); (3) the era of strut and wire biplanes, exemplified by the aerodynamic investigation of Eiffel, who blended both engineering science and engineering in his lengthy wind tunnel investigations (1909 – 1921); (4) the era of the mature propeller-driven airplane, characterized by the evolution of streamlining, representing again both engineering science and engineering; (5) the era of the modem jet propelled airplane, including the revolutionary development of the swept wing (see also the companion paper in this volume, “Engineering Experiment and Engineering Theory: The Aerodynamics of Wings at Supersonic Speeds, 1946 – 1948,” by Walter Vincenti). In the final analysis, we will see that the naive “engineering versus science” alluded to in the title of this paper fails to hold up, because the evolution of aerodynamics in the twentieth century was characterized by a subtle integration of both.

Part of the reconciliation between airport engineers and architects was stimulated by their mutual confidence in the utility of city planning in the design process. In a commentary on a paper presented by Donald Baker at a major meeting in 1928 of the American Society of Civil Engineers’ City Planning Division, John Nolen, one of the nation’s preeminent city planners, wrote: “As an outstanding feature of modem transportation the airport has an effect upon the city or urban community as a unit. To choose a site without consideration of all the elements of the community composition may mean that either the city may be injured by the location given over to the airport, or, in turn, the airport may not be so situated as to serve the city economically; or still worse, it may be so placed that it cannot develop business either from the city or serve as an adequate and safe stopping point on an airway for traffic from outside.”59

What Nolen and others were suggesting was a new way of understanding the specialized contributions of engineers and architects. In the minds of city planners, neither the engineering nor the architectural treatment of an airport facility

constituted the only issues guiding airport development. Good airport design, according to Nolen, necessarily incorporated “mastery not only of the physical conditions, but also a firm grasp on their financial and economic relations under appropriate statutes, laws and regulations.”60

City planners believed their endeavors to constitute a “scientific profession,” derived from a fundamentally different basis from that of engineering or architecture. John Nolen, wrote that “successful town planning cannot be the work of a narrow specialist, or of a single profession. The call is for versatility, special knowledge and cooperation. For town planning is engineering plus something; architecture plus something; or landscape architecture plus something….”61 Nolen was keenly interested in airports. He wrote several papers about city planning and airports, was an active public speaker on the subject, and most importantly was hired by several cities to design their airports. Nolen’s philosophy of city planning was that excellent results could only be achieved if social and economic factors were considered as seriously as demographic, aesthetic, and technical criteria. This produced a strikingly different outlook on airport design than existed in the aviation community. For example, when Commerce Department officials were in the midst of their crusades to persuade American cities to build airports, John Nolen stated unequivocally to a meeting of the Aeronautic Section of the Society of Automotive Engineers that the locations of the nation’s most important airports had already been determined. Simple “boosterism” was not particularly useful to Nolen’s way of thinking.62

Most city planners shared Nolen’s assessment. Airports were like bridges, connecting formerly-separated regions and like real bridges, they had the potential to alter the economic geography of the nation. The “bridge” had little value if it was not integrated with all other modes of transportation. The third part of airport design then, was identified as connecting the airport with the local systems of ground transportation.63

By the mid-1930s, engineers, architects and city planners were all engaged in the problems of airport design. Each profession viewed the technological possibilities of an airport from very different perspectives. This might have resulted in vigorous professional competition yet, instead the engineers, architects and city planners came to embrace each other (albeit warily) in a way that resulted in a synthesis of airport design concepts. There were several diverse factors contributing to this result including the full integration of radio into airport technology; the introduction of an entirely new type of aircraft, the so-called “modem” airliners; the political and economic circumstances of the 1930s that led to the Roosevelt Administration’s dramatic increase in federal investment in airports; and an abiding American fascination with aviation and its seductive promise of speed. How these factors helped bring together these three groups of professionals is perhaps best shown through a brief recounting of the development of LaGuardia Airport in New York.

Before a new engine or airframe achieves its first flight much prior ground testing has been done in wind tunnels or engine test cells. Ground and flight tests are run to establish performance characteristics and to aid in design development and refinement. This requires collection and analysis of relevant test data from test runs in specially instrumented engines, scale models, and aircraft.

The fundamental task of such tests is collecting performance and reference data. What data are collected depends upon the purpose of the tests:

Development testing to refine the final production design;

Type or endurance testing as precursor to military or civilian acceptance of the basic design;

Flight tests demonstrate aircraft or engine ability to operate under realistic circumstances, uncover design difficulties, and establish maintenance schedules for production aircraft or engines;

Acceptance tests to show that individual production engines meet minimum contractual performance characteristics.[2]

Some development, acceptance, and engine endurance testing can be done in wind tunnel and engine test stand ground facilities; the others invariably are airborne.

Instrumentation, which is the source of data from tests, tends to be most extensive in development testing and flight test – which are my focus. Airborne tests technically are the most demanding. For data to be useful, they must be recorded and processed into interpretable forms.

Instrumentation, recording, and processing of aircraft data have evolved substantially since the latter 1800s. These developments do not sort themselves into nice periodizations, but can be construed as three contrasting testing styles, overlapping for as much as 40 years, but each dominating different periods.

In the first style the primary airborne instrument is the test pilot’s subjective judgments augmented by notes on a knee pad and whatever readings of basic flying instruments could be jotted down. This style is important from the beginning of flight until about 1945, though a remnant today is the test pilot controlling what parts of the test flight are recorded at what data density.

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P Galison and A. Roland (eds.), Atmospheric Flight in the Twentieth Century, 67-105 © 2000 Kluwer Academic Publishers.

The second style emphasizes enhanced instrumentation recorded by something/ someone other than the test pilot, where recorded data, not the pilot’s reactions, are the primary data. Instrumentation can include an observer taking manual readings, gun cameras recording duplicate instrument panels, recording barographs, photopanels, transducer fed oscillographs, and telemetering to ground stations. Another defining characteristic is that data recording does not allow direct computerized analysis of the data. This style begins in the 1920s and dominates in the 1950s and 1960s.

The third style emphasizes very extensive automated instrumentation using transducers and probes, automatic pre-processing of data and digital data recording for computer analysis. This first comes in with the XB-70 and dominates high-end flight test subsequently – though style two continues in lower-end testing today where oscillographs continue to be used.

My story concerns evolution of instrumentation and data from style one to three. On the eve of World War II pilot reports, limited recording of data, and hand-analysis of recorded flight test data were typical. During the next three decades, automated data collection and digital computer reduction and analysis of data became the norm,2 with as many as 1200 channels of data being recorded and analyzed. The transformation essentially was complete with the instrumentation and data handling systems of the XB-70.1 will discuss the main transformations and changes in flight – test and ground-test instrumentation, data reduction, and analysis during that pivotal thirty-year period. Consideration will be given to wind tunnel testing, engine test-cell investigations, and flight-testing of both engines and airframes. I focus on turbojet – powered aircraft.

I also make some systematic philosophical remarks on data and modeling and offer concluding observations. 1

far enough to ensure reliable performance, the now proven new engine could be put into the unproven airframe.6

Before an engine ever is taken aloft, it undergoes a great deal of testing on the ground in test cells. Similarly, before a new airframe is taken aloft, it has undergone extensive aerodynamic testing in wind tunnels. A general rule of thumb is to use flight test primarily for what cannot be studied in ground testingfacilities.

The NACA research on transonic and supersonic compressors remained classified until the late 1950s. (Even the design “bible,” which focused on more conventional stages, was classified until 1958.) Consequently, the results of the research were not generally disseminated to those outside the United States, and even in this country they were not readily accessible. Moreover, unlike the “bible,” the reports themselves were aimed more toward providing a record of what had been done than toward instructing those outside NACA how to exploit the results. Even today, when read from the perspective of our far greater knowledge of transonic and supersonic stages, the reports are not always easy to assess. A large fraction of the knowledge that the NACA had gained on high Mach number stages remained in the heads of the engineers who had conducted the research.

This knowledge diffused out of the NACA through more than publications, however. Many engineers who had worked on high-Mach-number stages throughout the decade left NACA in 1955 and 1956. The Committee curtailed compressor research when Lewis, believing no fundamental problems remained in air-breathing engines, turned its attention to nuclear and rocket propulsion.46 Langley’s Jack Erwin and Lewis’s John Klapproth, Karl Kovach, and Lin Wright moved to General Electric. Kovach and Wright joined the company’s axial compressor aerodynamic design group, headed by Richard Novak, where they shifted their primary focus from research on airfoil shapes and parameters to design.

In some respects this timing was opportune. NACA research had produced the compressor design bible and had achieved sufficient success with transonic stages to turn the future over to the engine companies. The decade of research on supersonic compressors, the promising results in the last years notwithstanding, had yet to yield flight-worthy designs, making it hard to argue for continued funding. General Electric proved the beneficiary of the NACA’s change in focus, for GE offered the NACA engineers the chance to apply their experience with advanced, experimental designs to real engines. The knowledge Kovach and Wright brought from the government research establishment into the industry immediately began having an impact on the advanced designs GE was then developing. Wright’s knowledge, in particular, proved crucial to GE’s development of a radically advanced fan that formed the basis of their first flight-worthy turbofan engine, to which we now turn.47

Wood was the dominant structural material for airplanes from the pre-history of flight until the early 1930s. By the late 1930s, however, wood was rapidly disappearing, especially in the structures of high-performance military aircraft and multi-motored passenger airplanes. Metal succeeded as a result of intense efforts to develop all-metal airplanes, efforts that began in Germany during World War I and quickly spread to Britain, France and the United States after the Armistice.4

In both Europe and the United States, national aeronautical communities maintained a powerful commitment to developing metal airplanes between the world wars. As I have argued elsewhere, this commitment cannot be explained by the technical advantages of metal. The technical choice between wood and metal remained indeterminate between the world wars; wood had advantages in some circumstances, metal in others. Claims for metal’s superiority in fire safety, weight, cost, and durability all proved equivocal throughout the 1920s.5

Despite the questionable advantages of metal in the 1920s, national governments and private firms concentrated their research and development programs on improving metal airplanes, while shortchanging research and development on wood structures. This bias was especially strong in the United States, where the Army Air Service began shifting research funds from wood to metal as early as 1920. Nevertheless, successful metal aircraft proved quite difficult to design, and the U. S. Army remained heavily dependent on wooden-winged aircraft until the mid-1930s. After about 1933, however, new all-metal stressed-skin structures proved competitive with wood, especially in larger airplanes. Even with the substantially increased production costs required by the new all-metal stressed-skin structures, wood quickly disappeared from most high-performance airplanes in both the United States and Europe.6

One cannot, however, invoke metal’s eventual success to explain why this path was chosen in the first place. Metal’s success resulted from years of intensive development before the predicted advantages of metal became manifest. Proponents of metal advanced no clear-cut technical arguments to justify continued support for metal in the 1920s, when experience with metal failed to corroborate claims for its superiority to wood.7 In the United States, at least, the embrace of metal was driven not so much by technical criteria as by the symbolic meanings of airplane materials.

Metal’s supporters openly articulated these symbolic meanings in the 1920s. They insisted that the shift from wood to metal was an inevitable aspect of technical progress, arguing that the airplane would recapitulate the triumph of metal in prior wood-using technologies, such as ships, railroad cars, and bridges.

Advocates of metal drew upon pre-existing cultural meanings to link metal with progress, modernity and science, while associating wood with backwardness, tradition and craft methods. These symbolic associations gained their evocative power from the ideology of technological progress, a set of beliefs deeply embedded within the aviation community. By linking metal with progress, advocates of metal were able to construct a narrative of technological change that predicted the inevitable replacement of wood by metal in airplane structures. This narrative provided more than rhetoric; it also inhibited expressions of support for wood while insuring that metal received a disproportionate share of funds for research and development.8