Category Archimedes

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.

To understand the relationship of science and engineering to aerodynamics in the twentieth-century, we need to examine briefly the completely different relationship that existed during the nineteenth-century.

The history of aerodynamics before the twentieth-century is buried in the history of the more general discipline of fluid dynamics. Consistent with the evolution of classical physics, the basic aspects of the science of fluid dynamics were reasonably well understood by 1890. Meaningful experiments in fluid dynamics started with Edme Mariotte and Christiaan Huygens, both members of the Paris Academy of Science, who independently demonstrated by 1690 the important result that the force on a body moving through a fluid varies as the square of the velocity. The relationship between pressure and velocity in a moving fluid was studied experimentally by Henri Pitot, a French civil engineer in the 1730’s. Later in the eighteenth-century, the experimental tradition in fluid dynamics was extended by John Smeaton and Benjamin Robins in England, using whirling arms as test facilities. Finally, by the end of the nineteenth-century, the basic understanding of the effects of friction on fluid flows was greatly enhanced by the experiments of Osborne Reynolds at Manchester. These are just some examples. In parallel, the rational theoretical study of fluid mechanics began with Isaac Newton’s Principia in 1687. By 1755 Leonhard Euler had developed the partial differential equations describing the flow of a frictionless fluid – the well-known “Euler Equations” which are used extensively in modern aerodynamics. The theoretical basis of fluid mechanics was further enhanced by the vortex concepts of Hermann Von Helmholtz in Germany during the mid-nineteenth-century. Finally, the partial differential equations for the flow of a fluid with friction – the more realistic case – were developed independently by the frenchman Henri Navier in 1822 and the englishman George Stokes in 1845. These equations, called the Navier-Stokes equations, are the most fundamental basis for the theoretical study of fluid dynamics. They were well-established more than 150 years ago.

Thus, by the end of the nineteenth-century, the basic principles underlying classical fluid dynamics were well established. The progress in this discipline culminated in a complete formulation and understanding of the detailed equations of motion for a viscous fluid flow (the Navier-Stokes equations), as well as the beginnings of a quantitative, experimental data base on basic fluid phenomena, including the transition from laminar to turbulent flow. In essence, fluid dynamics was in step with the rest of classical physics at the end of the nineteenth-century – a science that was perceived at that time as being well-known, somewhat mature, with nothing more to be learned. Also, it is important to note that this science was predominately developed (at least in the nineteenth-century) by scholars who were university educated, and who were mainly part of the academic community.

The transfer of this state-of-the-art in fluid dynamics to the investigation of powered flight was, on the other hand, virtually non-existent. The idea of powered flight was considered fanciful by the established scientific community – an idea that was not appropriate for serious intellectual pursuits. Even Lord Rayleigh, who came closer than any of the scientific giants of the nineteenth-century to showing interest in powered flight, contributed nothing tangible to applied aerodynamics. This situation can not be more emphatically stated than appears in the following paragraph from the Fifth Annual Report of the Aeronautical Society of Great Britain in 1870:

“Now let us consider the nature of the mud in which I have said we are stuck. The cause of our standstill, briefly stated, seems to be this: men do not consider the subject of ‘aerostation’ or ‘avia­tion’ to be a real science, but bring forward wild, impracticable, unmechanical, and unmathematical schemes, wasting the time of the Society, and causing us to be looked upon as a laughing stock by an incredulous and skeptical public.”

Clearly, there was a “technology transfer problem” in regard to the science of fluid dynamics applied to powered flight. For this reason, applied aerodynamics in the nineteenth-century followed its own, somewhat independent path. It was developed by a group of self-educated (but generally we//-educated) enthusiasts, driven by the vision of flying machines. These people, most of whom had no formal education at the university level, represented the early beginnings of the profession of aeronautical engineering.

For example, this community of self-educated engineers was typified by the following: George Cayley, who in 1799 enunciated the basic concept of the modem configuration airplane; Francis Wenham, who in 1871 built the first wind tunnel; Horatio Phillips, who in 1884 built the second wind tunnel and used it to test cambered (curved) airfoil shapes which he later patented; Otto Lilienthal (who did have a bachelors degree in Mechanical Engineering), who carried out the first meaningful, systematic series of experimental measurements of the aerodynamic properties of cambered airfoils,4 and later designed and flew extensively the first successful human-carrying gliders (1892 – 1896); and Samuel Langley, 3rd Secretary of the Smithsonian Institution, who carried out an exhaustive series of well-planned and well-executed aerodynamic experiments on rectangular, flat plates,5 but who had two spectacular failures in 1903 when a piloted flying machine of his design crashed in the Potomac river.

Langley clearly stated the prevailing attitude in his Memoir published posthumously in 1911.6

“The whole subject of mechanical flight was so far from having attracted the general attention of physicists or engineers, that it was generally considered to be a field fitted rather for the pursuits of the charlatan than for those of the man of science. Consequently, he who was bold enough to enter it, found almost none of those experimental data which are ready to hand in every recognized and reputable field of scientific labor.”

Langley considered himself one of the bold ones. This is particularly relevant because in the United States at the end of the nineteenth century the position of Secretary of the Smithsonian was considered by many as the most prestigious scientific position in the country. Here we have, by definition, Langley as the most prestigious scientist in the United States, and he is turning the tables on the scientific community by devoting himself to the quest for powered flight.

However, the prevailing attitude abruptly changed in the space of ten years, beginning in 1894.

On Sunday, November 25, 1934, a front page article in the New York Times was headlined: “LaGuardia Won’t Land in Newark and Insists Liner Fly Him to City Airport From Rival Field.” “My ticket says New York, and that’s where they brought me,” said the beaming new mayor as he got off the TWA plane at Floyd Bennett Field.64 The whole incident was a carefully planned publicity stunt by Fiorello LaGuardia and his staff who wanted to announce dramatically his intentions to build a major airport in (not near) New York City. Five years later, 325,000 people joined the mayor to dedicate New York City Municipal Airport (renamed LaGuardia one month later) and another 1.5 million people plunked down a dime to inspect the airport operations during subsequent years, lured by the opportunity to see the world’s most modem airport.65

LaGuardia was seen as a kind of “crown jewel” in new national airport plans developed through the joint efforts of the Bureau of Air Commerce and WPA engineers. Describing the development of the LaGuardia, Fortune magazine noted that: “There is no such thing as an ideal airport. It doesn’t exist because the ideal geographic location for it doesn’t exist inside or adjacent to the metropolis it is intended to serve, symmetrical in all directions, possessing full wind coverage, and free from obstructions in its entire periphery. Most airports are a compromise.”66

Still, the site Mayor LaGuardia found in Queens on North Beach, the old Curtiss Airport, was considered nearly ideal. It fit into the city’s massive highway and parkway constmction program; it was on the water; the weather conditions were favorable; and the travel time into the city was projected to be nearly identical with Newark’s. Aero Digest added that “Instead of fitting the airport to its surroundings, handicapped by the terrain or the nearness of buildings, it was possible there to plan runways of ample length to meet the increasing requirements of the modem airliner and a rapidly-expanding air transport industry.”67

The WPA, under the direction of Brehon Somervell, had overall responsibility for the project. The main plans originated with the engineers, architects, and planners of the Design Section of the WPA Division of Operations, but the engineers of the city’s Dock Department were full partners in the effort. For the landfill portion of the project, a special board of consulting engineers from the Army Corps of Engineers was brought in. Private airport engineering firms were also consulted. Bureau of Air Commerce engineers laid out the field design, including lighting and other electrical signal device plans. WPA engineers conducted all the soil borings and topographic surveying. Delano and Aldrich were hired to design all the buildings and develop a landscaping plan.68

There were many contemporary descriptions of the various systems of mnways, drainage, heating, lighting, fire prevention, as well as of the designs for the administration and passenger terminal buildings plus the hangers. Above all, however, the greatest attention was accorded to the control tower and radio equipment. “The electrical wiring and controls in this room comprise one of the most intricate and efficient systems ever installed,” wrote Samuel Stott. There were 21 receiver units which were described as “elaborate as that of any airport in the World, and considerably more flexible.”69

LaGuardia Airport is significant not because the individual technological components represented the “newest” or the “best” of their class (although some were) but because it was the first to integrate these systems (and to do so in the design phase, rather than after the airport was built). This level of integration was only possible through the combined efforts of engineers, architects, and city planners as well as a host of federal, state, and local officials. The potential for chaos was quite high but all agreed that one entity had to have final say.

In the case of LaGuardia, the temptation is to identify the airport’s namesake, the mayor, as a driving, dictatorial force that brought about cooperation by coercion. Fiorello LaGuardia was certainly the local power behind the New York airport’s creation. The mayor assumed day-to-day responsibility for oversight of the airport (it was perhaps one of his proudest boasts that his rival Robert Moses, head of the New York Parks Department, had nothing to do with the airport). But LaGuardia Airport was not simply a local project. President Roosevelt was equally interested in the construction of this airport as were a bevy of federal officials. They saw New York’s new airport as the first of many major new metropolitan airports which would form the crucial links in the nation’s air transportation system. Right on its heels was the construction of Washington National Airport. Newark, Chicago, Los Angeles had all undergone major transformations compliments of New Deal relief dollars. All of these projects (and several hundred others) turned to the federal government for more than money. The airport sections of the WPA and the Bureau of Air Commerce working in tandem were, in fact, the main organizing force behind a national system of airports. It is these organizations that truly coordinated the design and construction of LaGuardia.

Airports were not islands unto themselves. They were part of a national system of airports. Air transportation was about the purposeful movement between geographically separate locations. Creating one “perfect” airport was of little value unless there were many others just like it. The federal airport engineers, especially W. Sumpter Smith, Jack Gray and Alexis McMullen, helped communities throughout the nation coordinate their efforts with each other. The federal engineers tapped into the new professional identity of engineers, architects, and city planners. During the opening decades of the 20th century the professional associations representing these three groups fashioned strong bonds that transcended local associations. The Commerce Department under the Coolidge, Hoover and Roosevelt Administrations all encouraged associational activities (albeit for different reasons and under different names).

No one wanted airplanes to crash but until the mid-thirties this happened with shocking regularity. Federal aviation officials used the fear-and-safety factor as initial leverage to promote the coordination of efforts among design professionals. All three groups were responsive to this appeal. However, it was also used to extract funds from Congress for the development of a radio-based air traffic control system. That system helped make the Bureau of Air Commerce, and its successor agency the Civil Aeronautics Authority in particular, the focal point for every airport project.

For small communities this was often the only technical consultation accomplished. For major airport projects like LaGuardia or Washington, the participation of the Bureau of Air Commerce representatives was considered vital. The centrality and importance of the federal leadership initiatives in airport development became apparent during the Congressional hearings for new civil aeronautics legislation in 1937 and 1938. Members of Congress were taken aback by the emphatic pleas of aviation advocates to strike out the airport exclusion clause of the Air Commerce Act of 1926.

Despite considerable trepidation, Congress was ultimately responsive to these concerns and the resultant Civil Aeronautics Act of 1938 expanded federal authority over the airways to include the development and operation of air navigation facilities at airports. Following the completion of the National Airport Survey in the spring of 1939, it was clear that a new era had begun. “Normal” airport design meant a process undertaken by several different types of technical specialists whose work on a specific local technological system was coordinated by the federal government (specifically the new Civil Aeronautics Authority) with responsibilities for the creation and maintenance of a national system. The role of the Federal government has endured to this day, as has the core design concept of both the airport and the network of airports and the tripartite relationship of airport engineers, architects, and city planners.

Between 1891 and 1896, Otto Lilienthal in Germany made over 2000 successful glider flights. His work was timed perfectly with the rise of photography and the printing industry. In 1871 the dry-plate negative was invented, which by 1890 could freeze a moving object without a blur. Also, the successful halftone method of printing had been developed. As a result, photos of Lilienthal’s flights were widely distributed, and his exploits frequently described in periodicals throughout Europe and the US.

These flights caught the attention of Nikolay Joukowski (Zhukovsky) in Russia. Joukowski was head of the Department of Mechanics at Moscow University when he visited Lilienthal in Berlin in 1895. Very impressed with what he saw, Joukowski bought a glider from Lilienthal, one of only eight that Lilienthal ever managed to sell to the public. Joukowski took this glider back to his colleagues and students in Moscow, put it on display, and vigorously examined it. This is the first time that a university-educated mathematician and scientist, and especially one of some repute, had become closely connected with a real flying machine, literally getting his hands on such a machine. Joukowski did not stop there. He was now motivated about flight – he had actually seen Lilienthal flying. The idea of getting up in the air was no longer so fanciful – it was real. With that, Joukowski turned his scholarly attention to the examination of the dynamics and aerodynamics of flight on a theoretical, mathematical basis. In particular, he directed his efforts towards the calculation of lift. He envisioned bound vortices fixed to the surface of the airfoil along with the resulting circulation that somehow must be related to the lifting action of the airfoil.

Finally, in 1906 he published two notes, one in Russian and the other in French, in two rather obscure Russian journals. In these notes he derived and used the following relation for the calculation of lift (per unit span) for an airfoil:

L = pVT

where L is the lift, p is the air density, V is the velocity of the air relative to the airfoil, and Г is the circulation, a technically-defined quantity equal to the line integral of the flow velocity taken around any closed curve encompassing the airfoil (Circulation has physical significance as well. The streamline flow over an airfoil can be visualized as the superposition of a uniform freestream flow and a circulatory flow; this circulatory flow component is the circulation. Figure 1 is a schematic illustrating the concept of circulation.) With this equation, Joukowski revolutionized theoretical aerodynamics. For the first time it allowed the calculation of lift on an airfoil with mathematical exactness. This equation has come down through the twentieth-century labeled as the Kutta-Joukowski Theorem. It is still taught today in university-level aerodynamics courses, and is still used to calculate lift for airfoils in low-speed flows.

The label of this theorem is shared with the name of Wilhelm Kutta, who wrote a Ph. D. dissertation on the subject of aerodynamic lift in 1902 at the University of Munich. Like Joukowski, Kutta was motivated by the flying success of Lilienthal. In particular, Kutta knew that Lilienthal had used a cambered airfoil for his gliders, and that, when cambered airfoils were put at a zero angle of attack to the freestream, positive lift was still produced. This lift generation at zero angle of attack was counter-intuitive to many mathematicians and scientists at that time, but experimental data unmistakenly showed it to be a fact. Such a mystery made the theoretical calculation of lift on a cambered airfoil an excellent research topic at the time – one that Kutta readily took on. By the time he finished his dissertation in 1902, Kutta had made the first mathematical calculations of lift on cambered airfoils. Kutta’s results were derived without recourse to the concept of circulation.

Only after Joukowski published his equation in 1906 did Kutta show in hindsight that the essence of the equation was buried in his 1902 dissertation. For this reason, the equation bears the name, the Kutta-Joukowski Theorem.

This equation became the quantitative basis for the circulation theory of lift. For the first time a mathematical and scientific understanding of the generation of lift was obtained. The development of the circulation theory of lift was the first major element of the evolution of aerodynamics in the twentieth century, and it was in the realm of science. The objective of Kutta and Joukowski – both part of the academic community – was understanding the nature of lift, and obtaining some quantitative ability to predict lift. Their work was not motivated, at least at first, by the desire to design a wing or airfoil. Indeed, by 1906 wings and airfoils had already been designed and were actually flying on piloted machines, and these designs were accomplished without the benefit of science. The circulation theory of lift was created after the fact.

Contemporary with the advent of the circulation theory of lift was an equally if not more important intellectual breakthrough in the understanding and prediction of aerodynamic drag. The main concern about the prediction of lift on a body inclined at some angle to a flow surfaced in the nineteenth-century, beginning with George Cayley’s concept of generating a sustained force on a fixed wing. In contrast, concern over drag goes all the way back to ancient Greek science. The retarding force on a projectile hurtling through the air has been a major concern for millenniums. Therefore, it is somewhat ironic that the breakthroughs in the theoretical prediction of both drag and lift came at almost precisely the same time, independent of how long the two problems had been investigated.

What allowed the breakthrough in drag was the origin of the concept of the boundary layer. In 1904, a young German engineer who had just accepted the position as professor of applied mechanics at Gottingen University, gave a paper at the Third International Mathematical Congress at Heidelberg that was to revolutionize aerodynamics.7 Only eight pages long, it was to prove to be one of the most important fluid dynamics papers in history. In it, Prandtl described the following concept. He theorized that the effect of friction was to cause the fluid immediately adjacent to the surface to stick to the surface, and that the effect of friction was felt only in the near vicinity of the surface, i. e., within a thin region which he called the boundary layer. Outside the boundary layer, the flow was essentially uninfluenced by friction, i. e., it was the inviscid, potential flow that had been studied for the past two centuries. This conceptual division of the flow around a body into two regions, the thin viscous boundary layer adjacent to the body’s surface, and the inviscid, potential flow external to the boundary layer (as shown in Figure 2), suddenly made the theoretical analysis of the flow much more tractable. Prandtl explained how skin friction at the surface could be fundamentally understood and calculated. He also showed how the boundary layer concept explained the occurrence of flow separation from the body surface – a vital concept in the overall understanding of drag. Since 1904, many aerodynamicists have spent their lives studying boundary-layer phenomena – it is still a viable area of research

today. This author dares to suggest that PrandtTs boundary layer concept was a contribution to science of Nobel prize stature. Perhaps one of the best accolades for Prandtl’s paper was given by the noted fluid dynamicist Sydney Goldstein who was moved to state in 1969 that: “The paper will certainly prove to be one of the most extraordinary papers of this century, and probably of many centuries.”8

As in the case of Kutta and Joukowski, Prandtl was a respected member of the academic community, and with the boundary layer concept he made a substantial scientific contribution to aerodynamics. This was science; the boundary layer concept was an intellectual model with which Prandtl explained some of the fundamental aspects of a viscous flow. However, within a few years this concept was being applied to the calculations of drag on simple bodies by some of PrandtTs students at Gottingen, and by the 1920s, research on boundary layers had become focused on acquiring knowledge for the specific purpose of drag calculations on airfoils, wings, and complete airplanes. That is, boundary layer theory became more of an engineering science.

In retrospect the beginning of the twentieth-century was the time of major technological breakthroughs in theoretical aerodynamics. These events heralded another breakthrough – one of almost a sociological nature. Wilhelm Kutta, Nikolay Joukowski, Ludwig Prandtl were all university-educated with Ph. D.s in the mathematical, physical, and/or engineering sciences and all conducted aerodynamic research focused directly on the understanding of heavier-than-air flight. This represents the first time when very respected academicians embraced the flying machine; indeed, the research challenges associated with such machines absolutely dictated the direction of their research. Kutta, Joukowski, and Prandtl were very much taken by the airplane. What a contrast with the prior century, when respected academicians essentially eschewed any association with flying machines, thus

causing a huge technology transfer gap between nineteenth-century science and the advancement of powered flight.

What made the difference? The answer rests in that of another question, namely, who made the difference? The answer is Lilienthal and the Wright brothers. Otto LilienthaTs successful glider flights were visual evidence of the impending success of manned flight; we have seen how the interest of both Kutta and Joukowski was motivated by watching Lilienthal winging through the air, as seen either via photographs or by actual observation. And when the news of Wilbur’s and Orville’s success with the Wright Flyer in 1903 gradually became known, there was no longer any doubt that the flying machine was a reality. Suddenly, work on aeronautics was no longer viewed as the realm of misguided dreamers and madmen; rather it opened the floodgates to a new world of research problems, to which twentieth-century academicians have flocked. After this, the technology transfer gap, in the sense that occurred over the previous centuries, began to grow smaller.

On 12 November 1975, ten lawyers from nine different law firms appeared in U. S. District Court, Southern District of New York. They represented twenty clients – nineteen of the largest aerospace firms in the United States and a curious legal and business entity known as the Manufacturers Aircraft Association, Inc. (MAA). All the aerospace firms were members of the MAA; some had been members since the MAA was founded in 1917. All ten lawyers agreed with the court’s finding that the MAA violated Section One of the Sherman Anti-Trust Act of 1890. The MAA was, in short, “a contract, combination… or conspiracy in restraint of trade or commerce.”1 On behalf of their clients, the assembled lawyers agreed to “wind up the affairs and terminate the existence” of the MAA.2 They further agreed to “terminate and cancel the Amended Cross License Agreement,” the legal instrument defining the purpose and operation of the MAA.3

The consent decree captures none of the historical irony hanging over this decision. The federal government had directed aircraft manufacturers in 1917 to enter into a cross-licensing agreement and to form the MAA to administer the agreement. In spite of protests at the time and repeated challenges in the 1920s and 1930s, the Justice Department consistently found that the cross-licensing agreement did not violate the Sherman Anti-Trust Act. In 1972, however, that same Justice Department brought suit in District Court, arguing, in effect, that it had been mistaken for 55 years. During that time, the United States aircraft manufacturing industry had been arguably the most successful in the world, dominating a market in which other nations, beyond the reach of the MAA, were free to compete. Half the companies represented in District Court had joined the MAA since its founding, a membership pattern suggesting openness and inclusivity, not combination and conspiracy. The MAA had been good for its members and good for America.4

Still more ironically, termination of the cross-licensing agreement had no discernible impact on American aircraft development. The MAA went out of business in 1975. All the patents licensed by the MAA and controlled by its members were made available to any applicant. The Court arranged to adjudicate disputed royalties arising from the new dispensation. Yet American aircraft manufacturers went right on dominating the free world market for this product, just as they had done under the protection of the cross-licensing agreement. In fact, the termination of the MAA coincided with the introduction of the European Airbus,

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which, in the words of author John Newhouse, appeared at first “to be an even more dismal failure than most of Europe’s other jet transports had been.”5 The Airbus went on to be more competitive, but the United States still dominates the world market for commercial airliners more than twenty years after the dissolution of the MAA.

The many ironies of this case have attracted scholars of patent law, economists, and even sociologists.6 They have not, however, stimulated much study by historians of technology, not even historians of aviation. In most histories of American aviation, patents are noted by their absence.7 Even in my own study of the National Advisory Committee for Aeronautics (NACA), patents find little place after the cross-licensing agreement of 1917, which the NACA brokered.8 The NACA formed a patents committee in 1917, but discharged it with thanks when the cross-licensing agreement was signed. The Air Commerce Act of 1926 directed the NACA to form a patents committee, but the following year the NACA converted it to a committee on “Aeronautical Inventions and Design.” Congress may have thought of aviation development in terms of patents, but the NACA did not. Even in the 1930s, when the NACA found itself under congressional pressure to be of greater service to industry, it was proprietary information, not patents, that proved the sticking point.

The importance of aircraft patents to economists and legal scholars and their apparent irrelevance to aviation historians raises several nagging questions. Have historians simply overlooked the importance of patents in aviation history? If, as historians seem to believe, patents were not important, why was there a patent pool? And why did the Justice Department believe that the patent pool restrained trade? Finally, if patents do not shape an innovative industry, such as aircraft manufacture, what do they achieve? And what, then, does drive innovation in aircraft manufacture?

This paper will attempt to answer those questions. It will first summarize the history of aircraft patents in the United States. Then it will explore the theory of patents and the application of that theory to this particular case. Next it will seek the reasons for the success of the American aircraft industry, looking especially for ways in which patents might have played a role. In conclusion, it will attempt to explain the invisibility of patents in previous accounts.