two-stroke or turbine-the aeronautical research committee and british aero engine

Two-Stroke or Turbine? The Aeronautical Research Committee and British Aero EngineDevelopment in World War IIAuthor(s): Andrew NahumSource: Technology and Culture, Vol. 38, No. 2 (Apr., 1997), pp. 312-354Published by: The Johns Hopkins University Press on behalf of the Society for the Historyof TechnologyStable URL: http://www.jstor.org/stable/3107125Accessed: 12/11/2009 18:12

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Two-stroke or Turbine? The Aeronautical Research Committee and British Aero Engine Development in World War II ANDREW NAHUM

All the ascendancy of the Hurricanes and Spit- fires would have been fruitless but for this system ... which had been devised and built before the war.... It had been shaped and refined in constant action, and all was now fused together into a most elaborate instrument of war, the like of which ex- isted nowhere in the world. [WINSTON CHURCHILL, The Second World War]l

During the 1930s, the growing apprehension in Britain about air attack began to provoke a shift in strategic thinking away from a purely retaliatory posture, which relied on a bomber force to counter the threat of bombers, toward a mixed strategy in which defensive interceptor fighters were to have a vital role. This new per- ception stimulated an intensive program of research and development in radar, in the control of fighters from the ground, and in aero engines. A connection between radar developments and a shift

MR NAHUM is senior curator of the National Aeronautical Collection at the Science Museum, London. He gratefully acknowledges the support of the museum in the conduct of this research, and thanks his colleagues Timothy Boon, Sir Neil Cossons, Dr. Robert Bud, and Dr. Alan Morton for many helpful comments. John Bagley, the author's predecessor as curator of the aeronautical collection, provided a unique insight into the organization of government science from his time at the

Royal Aircraft Establishment (RAE), Farnborough, and gave immense encourage- ment for the undertaking of this work. Dr. David Edgerton at the Imperial College was generous with his comments. Finally, the author is grateful to the editor and referees of Technology and Culture for invaluable suggestions.

1Winston Churchill, The Second World War, vol. 2 (London, 1949), pp. 293-94. This is taken from a description of Churchill's visit to the fighter control center at Northolt on September 15, 1940, the turning point of the Battle of Britain. It conveys his instinctive appreciation of the way in which the functional integration of the British air defense system had created a pivotal strategic asset.

? 1997 by the Society for the History of Technology. All rights reserved. 0040-165X/97/ 3802-0002$01.00

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British Aero Engine Development

in policy in the mid-1930s to support jet engine development has previously been surmised.2 This study goes farther and establishes a direct linkage between early secret knowledge of radar and a wide range of British high-power aero engine work.

The relationship between these programs casts light on contemporary planning for air defense and reveals a remarkably holistic approach to the pressing problem of bomber interception. This gave rise to an integrated defense system which was, at that time, uniquely powerful and on which national survival in the Battle of Britain was to be critically dependent.

There is a conventional stereotype of British defense science in this period. A lone inventor or "boffin," committed, passionate, dis- organized, inspirational, is pitted against the rigidity of officialdom (which is ultimately overcome). It is a scenario that has done great service to motion picture makers, for example in The Dam Busters, where the eccentric genius Barnes Wallis eventually sells his idea for a bouncing bomb to skeptical officials and Royal Air Force (RAF) officers.3

A more purposeful and technocratic vision of British defense research can be found in the official histories of World War II or in a work such as Margaret Gowing's Britain and Atomic Energy. More

recently, there has been an even stronger claim to characterize Britain as a "militant and industrial nation" with the contention that "the English state chose the aeroplane as its key strategic technology."4

The account here differs from these models. It does not seek to locate the roots of British air defense uniquely in government or "the state," nor in the insights of exceptionally inventive engineers. Rather, it portrays these roots as diffused to a remarkable extent through a both formal and informal network of individuals who, for the most part, were already in a social and professional relationship reaching back to World War I. Some were indeed government officials or air force officers, although other key figures were academics,

2Edward W. Constant II, The Origins of the Turbojet Revolution (Baltimore, 1980), p. 191.

3 The Dam Busters, directed by Michael Anderson, 1954. A similar characterization serves for the British aeronautical scientist who predicts metal fatigue in a civil air- liner in the slightly earlier No Highway (U.S. title No Highway in the Sky), directed

by Henry Koster, 1951. 4See, for example, M. M. Postan, D. Hay, andJ. D. Scott, TheDesign and Development

of Weapons (London, 1964); Margaret Gowing, Britain and Atomic Energy 1939-1945

(London, 1964); and David Edgerton, England and the Aeroplane (London, 1991), p. 43.

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314 Andrew Nahum

FIG. 1.-The Rolls-Royce Crecy V-12, two-stroke engine. It was conceived in late 1935 as a "sprint" engine to give exceptional performance to interceptor fighters and to exploit new air defense tactics made possible by radar. (Courtesy of Rolls- Royce PLC.)

industry researchers, and designers. The main focus for this group was the Aeronautical Research Committee (ARC), which will be discussed more fully below.

As another war began to appear increasingly likely, the ARC saw the need for a new priority in engine development and became an

important proponent of new programs intended to bring forward

engines of very high performance. This article initially explores British piston engine development

in the interwar period, when, surprisingly, the influential policymak- ers in the ARC gave high priority to promoting an aircraft diesel

engine program that ultimately failed to fulfill the promise they an-

ticipated. However, in late 1935, the ARC adopted a new strategy and transmuted the design that had been developed for the diesel to produce an ambitious and unconventional two-stroke gasoline piston engine, intended as a very high-power fighter aircraft unit.

The ARC persuaded Rolls-Royce, the most able and technically accomplished British aero engine company, to adopt this converted diesel project, which became known as the Crecy (fig. 1). Thereafter, within the bounds of this single powerful company, a kind of devel-

opment contest ensued among the ever-improving and more conventional Merlin engine, the two-stroke Crecy, which represented a

quite novel departure for the piston aero engine, and the emerging jet engine, which also passed into Rolls-Royce control. The two-


stroke Crecy did not succeed, and although it can be regarded as a "failed innovation," the development program illuminates the social, organizational, and political milieu from which the British air defense system emerged to fight Germany in World War II and helps to characterize the nature of the decision-making process within it.

The processes by which the Crecy two-stroke was brought forward are of general interest to the history of technology, for if there is a single paradigm that seems to typify the process of radical innovation in technology, it is the replacement of the piston aero engine by the jet-a transition that forms the subject of Edward W. Constant's compelling model for revolutionary technological change.5 In the study here, the forces acting on the two-stroke program are compared with those operating on the new gas turbine. Constant's account of the replacement of the piston engine by the jet highlights a tension between technically impressive but incremental changes in the existing paradigm (as best exemplified by the Rolls-Royce Merlin piston engine) and the revolutionaryjet. A study of this contempora- neous Crecy two-stroke program suggests a development process for both kinds of engine that was more pragmatic, less "revolutionary," and perhaps even more complex than his richly textured account implies. Thus, this article relates the development of the jet in Britain more closely to general engine work and provokes questions about mechanisms for technological choice and technological change.

The Aeronautical Research Committee and Its Engine Sub-Committee

The Aeronautical Research Committee (ARC) was founded in 1909 at the instigation of Lord Haldane (secretary of state for war), initially as the Advisory Committee for Aeronautics, to supervise aeronautical work at the National Physical Laboratory (NPL) and "for general advice on the scientific problems... of the work of the Admiralty and War Office in aerial construction and navigation." However, the committee was not directly a government organization and, although numbering government officials and scientists among its members, also included the most eminent academic authorities on aeronautics as well as the directors and senior members of research organizations such as the Royal Aircraft Establishment (RAE), Farnborough, and the NPL. There were also representatives from the industry. It met about once a month and had no full-time members; another curiosity about its status was that it could not directly order things to be done. As Sir Alfred Pugsley, chairman from

5Edward W. Constant II, "A Model for Technological Change Applied to the Tur-

bojet Revolution," Technology and Culture 14 (1973): 553-72.

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316 Andrew Nahum

1952 to 1957, observed, it "never had any direct control of the rele- vant research finances. This did not seem to matter during the early years. The prestige of the Committee ensured that its advice would be followed at the NPL and at Farnborough also."6 Indeed, as Henry Tizard remarked, "One can make almost any scheme work if there is a general desire to do so."7

Detailed business was conducted through subcommittees which

generally contained one or more members of the main ARC but were augmented by other experts. These considered specific areas such as structural strength, fatigue, stability, control, and so on. The deliberations of these groups passed back to the parent ARC and

underpinned the research and development decisions taken by government departments. The director of scientific research at the Air

Ministry and the deputy director would, for example, be members of the main body and several subcommittees.

The Engine Sub-Committee of the ARC had been formed in 1920. Its enduring core, throughout the interwar period and during much of the Second World War, consisted of three individuals: Tizard, Harry Ricardo, and David Pye. A study of their work and influence reveals the personal, often informal connections that were important to the development of the British air defense system.

Through most of the period under consideration, Tizard served as chairman of both the ARC itself and of the Engine Sub-Com- mittee. His influence on defense science, and particularly on the

political birth of the British radar chain in World War II, is well known.8 His role in the aero engine field has been less well appreci- ated.

The Engine Sub-Committee also can be viewed as the formal man- ifestation of a powerful network of personal and social relationships based on bonds formed, in many cases, under special conditions in World War I, for in 1915, Tizard and Pye were among a number of academic scientists to be drawn into the new field of aircraft testing being developed at the Royal Aircraft Factory, Farnborough, and at the Aeroplane Experimental Station at Martlesham Heath in Suf- folk. The station was directed by the charismatic Bertram Hopkinson (in peacetime professor of mechanism and applied mechanics at

6Sir Alfred Pugsley, "A History of the Aeronautical Research Council: A Personal View," The AeronauticalJournal 91 (1987): 343-49.

7Ronald W. Clark, Tizard (London, 1965), p. 76. 8See, for example, C. P. Snow, Science and Government (London, 1961), essays origi-

nally given in 1960 at Harvard University as the Godkin Lectures; and P. M. S. Black- ett, Studies of War (Edinburgh, 1962).


Cambridge), who introduced Tizard to his former student Harry Ri- cardo.9

Ricardo at the time was just beginning his long and successful consultancy career in internal combustion engineering. He already had designed the engine for the British Army Mark V tank and had begun research into the then misunderstood phenomenon of "knock" or detonation in gasoline engines. The importance of knock-an explosive, premature combustion of the compressed fuel-and-air mixture within the engine cylinder-is that heat builds up and leads to a runaway condition which wrecks the engine. The likelihood of its occurrence in a particular engine design increases as the power output is raised. It thus sets a real limit to engine development and particularly to the usual recourse of raising power by increasing the compression ratio. Ricardo had glimpsed that the occurrence of knock might be linked to the characteristics of the fuel and had already begun to compare gasolines from different crude oil sources.10

Ricardo later recalled: "With Tizard ... I found I had many inter- ests in common, and almost at once we developed a very warm friendship that endured to the end of his life. Tizard, like myself, believed that there was a very real need for a thorough investigation into the properties of the available fuels and their influence on the behaviour of the engine."11

9Hopkinson began the scientific testing of aircraft in the early stages of World War I and founded an experimental station on an isolated spit of land at Orfordness on the east coast of England for air gunnery and bombing, with an associated airfield nearby at Martlesham Heath. Tizard was at the time a theoretical chemist who had studied with Nernst in Berlin. Pye had taken the mechanical sciences tripos at Cam- bridge and moved to Oxford in 1909 to help establish the engineering science course.

'1Knock or "pinking" is sometimes briefly heard in automobile engines when pulling slowly at high throttle opening. In an aero engine running at constant high power, it is far more damaging. The sound is caused by the high-velocity pressure wave reaching the cylinder walls. Guided initially by Hopkinson, Ricardo had established that knock was not the same as preignition (as then supposed) and could be mitigated by fuel composition and cylinder head design. Ricardo was to show that heat radiated from the expanding flame front caused the detonation of the residual charge.

' "He was, I think, the most brilliant of my contemporaries, a delightful compan- ion, with a pretty sense of humour .... His wit charmed us all and my two young daughters adored him." Sir Harry Ricardo, Memories and Machines: The Pattern of My Life (London, 1968), p. 195. (Reprinted by the Society of Automotive Engineers as The Ricardo Story, 1992.) Ricardo's contemporaries have recorded his courtesy, fair- mindedness, and mastery of technical exposition. Pye, perhaps because he was in- nately self-effacing, has been hardest to glimpse at this distance in time. A colleague

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318 Andrew Nahum

When the war finished, they began a study using purpose-built research engines at Ricardo's new laboratory at Shoreham, on the south coast near Brighton. Tizard brought Pye into the work, and

they prepared "a monumental analysis of the physical and thermal

properties of all available volatile liquid fuels."12

Eighteen months of research showed that detonation was the sin-

gle most important factor limiting gasoline engine performance, rather than the calorific value of the fuel or its other properties. As Tizard put it, "At a given compression ratio the nature of the fuel did not materially influence the maximum power developed. In

practice, the best fuel was that which showed the least tendency to knock."

To compare fuels quantitatively, he devised a comparative rating in terms of a "toluene number" (toluene was the fuel least prone to

detonating that they had found), and this system was used in engine research until it was superseded by the octane scale.13

In 1920, Tizardjoined the newly formed government Department of Scientific and Industrial Research (DSIR), where he dealt with a wide range of scientific policy matters; he became a member of the ARC in the same year. Ricardo continued engine research at Shore- ham, his company becoming the foremost internal combustion en-

gine consultancy in Britain and acquiring an international reputa- tion. Pye became deputy director of scientific research at the Air

Ministry in 1925 (and director in 1937). All three stayed in close contact, both socially and through membership on the Engine Sub- Committee, and their participation led the Engine Sub-Committee to take a strong interest in detonation problems.14

The Engine Sub-Committee also looked at strategic directions for

long-range engine research, commissioning in 1920 a report by W. J. Stern of the Air Ministry Laboratory, South Kensington, on

from his later years as provost of University College, London, characterized him as "a charming and civilized man.... It was in part because he seemed without ambi- tion to lead that we trusted his leadership."

12 Sir Harry Ricardo, quoted in W. S. Farren, "Henry Thomas Tizard," Biographical Memoirs of Fellows of the Royal Society 7 (1961): 322. Research engines for fuel and knock study have a variable compression ratio that is gradually increased until detonation is detected with a given fuel.

13Devised by Graham Edgar at the Ethyl Gasoline Corporation in 1926. See R. Schlaiffer and S. D. Heron's essential account, TheDevelopment ofAircraft Engines and Fuels (Cambridge, Mass., 1950).

'4For example, in 1923, shortly after the first tests by the U.S. Army, the Engine Sub-Committee was studying a report on the antidetonation properties of tetraethyl lead when used as a fuel additive.


the gas turbine and accepting his (correct) conclusion that progress could be made only from metallurgy and improved "blower" effi-

ciency.15 Nevertheless, when A. A. Griffith, as a member of the En-

gine Sub-Committee, proposed turbine research in the light of his research at the RAE, the construction of a test rig was recommended.16

The experience of the group in detonation research also led to its promotion of the sleeve valve, for piston engines, which was to have a major effect on national aero engine policy. Ricardo discov-

ered, in the course of research on cylinder head shapes, that a sleeve valve in the cylinder wall remained far cooler than the mushroom head of a conventional poppet exhaust valve, delaying the onset of detonation and allowing an engine to sustain higher powers for a

given fuel. As a result, all Bristol air-cooled radial engines in World War II used sleeve valves, as did the liquid-cooled Napier Sabre and a variety of experimental Rolls-Royce engines that were under devel-

opment at the end of the war.17

The British Aircraft Diesel Engine

Throughout the 1920s, the development of the aircraft diesel en-

gine consumed much of the Engine Sub-Committee's attention. Ri-

cardo, Tizard, and Pye had established, through their research, the doctrine that the knock rating of fuel was the crucial limiting factor in the power output of gasoline engines. Contemporary gasoline possessed, by that time, an octane rating of about 67, and there was not any expectation of the continuing improvement in fuel that was in fact to occur. The individuals at the heart of long-range engine planning in the ARC therefore believed, on the basis of their own

15W. J. Ster, "The Internal Combustion Turbine," ARC Engine Sub-Committee Re-

ports, no. 54, September 1920 (Science Museum archive). The report achieved noto-

riety since Whittle blamed it for his initial negative reception from the Air Ministry. '6A. A. Griffith, "An Aerodynamic Theory of Turbine Design," RAE Report H. 11,

July 7, 1926. In 1930, the Engine Sub-Committee recommended that ?1,000 should be allocated for construction of an experimental turbine "if it would provide an

unequivocal check on the theory." File DSIR 22/68, Public Record Office, London. The panel included W. J. Stern, who agreed.

17Ricardo's advocacy of the sleeve valve and its adoption for a large proportion of British aero engines is an important subject that will form a separate study. The decision to use it was always contentious; development was expensive and troubled.

Pye observed that "the sleeve valve had been a sickly child ever since it was brought to birth. ... It was a serious criticism ... that no one had made a success of it." He would not be drawn to it "if it were not the only way out of this impasse of the red hot exhaust valve." Journal of the Royal Aeronautical Society (July 1930): 597.

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320 Andrew Nahum

research, that scope for the development of gasoline engines was limited.18

Compression ignition engines, on the other hand, were immune to knock. The character of the fuel is less critical, and the pattern of combustion and the rate of pressure rise in the cylinders are gov- erned largely by the rate of injection of the fuel. But although the rate of pressure rise in a diesel is controlled, the ultimate cylinder pressures attained are higher. The engine must be stronger and so must weigh more than a gasoline engine. But Ricardo believed that diesel power outputs would continue to rise through development, overtaking the output of gasoline engines as they reached the ceiling imposed by the knock rating of their fuel. At his laboratory, he conducted research to force up the power output of the diesel by supercharging and by increasing the engine speed.

At this time, the British airship program was in progress, and the fact that the ships were filled with hydrogen gave the safety arguments in favor of diesel even more force. Not only was diesel fuel less inflammable than gasoline, but the exhaust was cooler (because of the excess air present in the diesel cycle), and there was no need for high-voltage spark ignition equipment.

The crash of the R101 in 1930 put an end to British rigid airship work and might have brought a reduction of work on the diesel, but the efforts of the Engine Sub-Committee to adapt it to heavier-than- air craft were undiminished, even though, on a power-to-weight basis, the power output remained stubbornly poor. The problem was that advocates of the diesel were pursuing a moving target. The power output of gasoline engines defied the earlier expectations of Ricardo, Tizard, and Pye and increased steadily during the period largely as a result of improvements in the octane rating of gasoline fuel.19

During this period, Ricardo acquired two Rolls-Royce V-12-cylinder Kestrel aero engines of 21 liters capacity (the company's standard service type) and adapted them to diesel, while at the same

1ARC Engine Sub-Committee Minutes for November 6, 1928. Minutes of the En- gine Sub-Committee between 1920 and 1936 are in files DSIR 22/58 to 22/62 at the Public Record Office, London.

'9In 1930, Ricardo estimated that there had been a 40 percent increase in gasoline engine power. H. R. Ricardo, "The Development and Progress of the Aero Engine," Eighteenth Wilbur Wright Memorial Lecture, Royal Aeronautical Society, May 30, 1930. The octane rating of fuel consistently improved in the period under review through the use of tetraethyl lead, the selection of crude oil stocks, and chemical

manipulation of the refining process. Engine development also reduced the detonation problem by better design to control the temperature in cylinder heads and valves.

British Aero Engine Development time the engines were converted to single sleeve-valve operation- the valve mechanism Ricardo had come to favor. The result was dis- appointing. The "RR/D" produced only 350 horsepower compared with some 500 for the standard Kestrel. Furthermore, cracks began appearing in the cylinder block and connecting rods, the big ends proved inadequate, and there were piston failures.

Faced with such problems, Ricardo decided to turn to the two- stroke cycle as the best way to increase the power output from a given weight of engine structure and to give the diesel a better chance of competing with the gasoline engine. The double number of firing impulses in a two-stroke does not, of course, necessarily improve power pro rata over a four-stroke, particularly in a simple piston- ported two-stroke engine, and for this reason Ricardo, since 1926, had been testing a more complex two-stroke (called the E40 in the Ricardo company classification) using a sleeve-valve to allow a uniflow or "end-to-end" scavenge of the cylinder (fig. 2) and indepen- dent optimization of the inlet and exhaust valve timing.20

Ricardo's next experimental two-stroke sleeve-valve diesel (the E44) was able to run at the then high speed of 2,500 rpm, and he predicted outstanding power outputs. An engine of Kestrel size built to this system should develop 735 horsepower, considerably more than the gasoline version, and Tizard even referred to the prospect of the compression ignition engine superseding the petrol engine in the near future and of fuel "dopes" for gasoline engines, such as tetraethyl lead, being no longer required.

Ricardo also anticipated "excellent wearing qualities," particularly because of the fact that in a supercharged two-stroke, the piston is always subjected to positive pressure, giving a cushioning effect on the crankshaft and connecting rod bearings and mitigating "the smashing effect of load reversals" met with in the four-stroke. Pye, however, confessed to some misgivings about "the stability of running" of an experimental Ricardo two-stroke unit, which, he noted, had needed to be opened up five times in a sixty-eight-hour test. "There were still some fences to be crossed," replied Ricardo, "but the goal was well worth it."21

The goal of the Engine Sub-Committee was that a major engine manufacturer should take up the development of the two-stroke diesel. In 1930, Pye had observed that "when Sir Henry Royce [of Rolls-

20This arrangement gave a ring of inlet ports at the bottom of the cylinder and exhaust ports at the top, helping to reduce the mixing of inlet and exhaust gas streams, which is such a poor feature of the simple two-stroke.

21Engine Sub-Committee Minutes, February 2, 1932.

321

FIG. 2.-Single sleeve valve for the Ricardo design of the E44 two-stroke diesel. The sleeve, which functions both as the cylinder liner (in which the piston runs) and as exhaust and inlet valve, rises and falls with a circular motion, dropping to allow exhaust to flow over the top of the sleeve, and then allowing the row of ports in the "waist" area to communicate with the inlet air supply. (Courtesy of Rolls- Royce PLC.)


Royce] was at Shoreham he appeared keener about two-cycle operation than anything else, on account of the reduction in torque variation." Royce was certainly excited by the possibility. At this time, he had moved from Derby to the south coast, not far from Shoreham. He exchanged visits with Ricardo, seeing the diesel- ized RR/D Rolls-Royce Kestrel on test and discussing the prospects for the aircraft diesel.22 Ricardo also visited him in the south of France, where he spent the winters and from where Royce wrote to his company in May 1930 urging more speed in compression ignition experiments, aiming toward a 1,000-horsepower unit for the Air Ministry. By September 1931, he was clearly frustrated, writing, "We are not making sufficient progress and we are on the way to missing our chance-My impression is that this type of engine is of the utmost importance to us-All aeroplane pilots would welcome enor- mously the absence of highly volatile inflammable fuel-Our aero engine position is precarious unless we keep right in front." At Derby, Rolls-Royce schemed out a two-stroke diesel engine on the lines sketched out by Royce, and in 1932, Pye asked him formally to work on an engine.23

Rolls-Royce formed a diesel team at Derby, but no production aero diesel appeared, while the octane rating of gasoline continued to improve, making the diesel (even a supercharged two-stroke version) seem increasingly unattractive. Signs of dissent began to appear in the Engine Sub-Committee in 1934, when Tizard stated that "there did not appear to be any engine development at present so promising as this," although Andrew Swan, head of the Engine Ex- perimental Department at the RAE, Farnborough, pointed out that "the new petrol" would allow higher compression ratios, giving improved fuel consumption and power. By the following year, Pye, too, had turned against the two-stroke diesel in view of the results with gasoline then being obtained, declaring that he was against locking up skill in diesel research.24

However, Tizard clung to the diesel dream with tenacity, referring to the "increasing body of opinion that the engine of the future

22Because of illness, Royce left Derby in 1911 and divided his time between West

Wittering near Chichester and the Villa Mimosa at Le Canadel, near St. Tropez. Up to his death in 1932, he had a personal staff in attendance of about six designers, a secretary, and a technical author.

23Minutes from Royce, Compression Ignition Engines, September 1, 1931; and letter and sketch by designer Albert Elliott interpreting Royce's scheme for the en-

gine to Rolls-Royce colleagues, September 1, 1930, Rolls-Royce Heritage Trust and

Engine Sub-Committee Minutes, February 2, 1932.

24Engine Sub-Committee Minutes, June 25, 1935.

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324 Andrew Nahum

may be of the compression ignition type," although his remarks acquired an increasingly plaintive tone. "If petrol fuel stopped developing," he suggested, "compression ignition might have a great competitive advantage," and he argued that "as the risks of flying become less those that remain would receive greater prominence and hence the fire risk with petrol might no longer be tolerated. ... Although it would hardly be safe to predict that [its] performance would exceed that of the petrol engine some one in authority must have the courage, or the foolishness, to say we must have the compression ignition engine."25 Ricardo also kept faith with the diesel, arguing that the rate of development of the two types pointed in the diesel's favor. Judged by his experimental results, the power-to- weight ratio of the diesel had doubled in the last two years, and he foresaw scope for more improvement.

This continuing advocacy of the diesel may seem, with hindsight, obsessive, but it can be traced clearly to the insights Tizard, Ricardo, and Pye had gained into gasoline engine detonation in 1919.26 Nev- ertheless, after 1936, a new imperative-the search for sheer power-made this diesel work seem increasingly irrelevant. How- ever, the two-stroke diesel experiments were to be the jumping-off point for something quite different-the Rolls-Royce Crecy, a gasoline engine of, potentially, exceptional power which embodied the most unconventional design solutions attempted during the whole of the "late piston engine" period.

New Objectives: The Need for Power

By the end of 1935, the attention of the ARC became focused on a major new objective: the search for high-power engines for interceptor fighters. This change in emphasis, it will be shown, derived from a change in thinking about air defense, provoked by the secret knowledge that the emerging technology of radar might be capable of giving an early warning of attack.27

The new direction was quite suddenly signaled by Tizard at the

25Engine Sub-Committee Minutes, September 24 and October 29, 1935. "The diesel is widely held to be the safest engine obtainable," Tizard had observed.

26Unease over the availability of high-octane gasoline in wartime also helped to prolong research. Part of the interest in the Whittle jet as war approached also derived from its tolerance of low-grade fuel.

27The initial British terminology for the system was RD.F. (radio direction find- ing), to disguise the technique under the name of an existing technology. For simplicity, radar is used here. Tizard noted: "When I went to Washington in 1940 I found that radar had been independently invented in America about the same time as ... in England." Science and the Services, Journal of the Royal United Service Institution 91 (August 1946): 333-46. However, because of the absence of an air threat in the United States, radar had not then been integrated into a fighter control system.


meeting on December 3, 1935. The discussion initially concerned the provision of sufficient high-octane fuel in wartime, a requirement estimated by Tizard at a million tons a year. This very high requirement seemed to lead to the conclusion that if all engines were to be designed for high octane, a dual fuel system would be

necessary, so that the more easily procured 87 octane could be burned until high combat power was required. Andrew Swan, from the RAE, suggested that an alternative policy would be to design and build "a limited number of high octane engines for sprint purposes."

Tizard "remarked that if it was the desire of the Air Ministry to

develop a type of sprint engine for home defence . . . there was ... the question as to how far fuel consumption could be disre-

garded. Mr. Ricardo had raised this point in a recent conversation

by enquiring whether a high fuel consumption might not be permis- sible under certain circumstances for, if so, an investigation of the

possibilities of the two-stroke petrol engine appeared to be attractive."

This exchange is interesting for the implication that development of a new type of engine of very high power, or "sprint" engine, had

already been the subject of private discussion between Tizard and Ricardo. The reason for an interest in such an engine derived from Tizard's chairmanship of the newly formed Committee for the Scien- tific Survey of Air Defence (usually called the Tizard Committee), created in response to the growing alarm about the threat of the bomber. This committee was, of course, nursemaid to the emerging system of radar-directed interception.28

With the exception of these Engine Sub-Committee discussions, the shift in engine policy was achieved without written policy papers or minuted arguments, and if the formulation of an unwritten en-

gine policy between these protagonists seems odd, the closeness and trust of the relationship among these men, going back to their role in World War I, should again be recalled.29 This informal, personal

28"Formation of a Scientific Committee on Air Defence," File AIR 2/4481/ S34763 (minute of 12/11/ 34), Public Record Office, London. The brief of the Com- mittee for the Scientific Survey of Air Defence (more usually known as the Tizard

Committee) was to study "how far recent advances in scientific and technical knowl-

edge can be used to strengthen the present methods of defence against hostile aircraft." Tizard was a trusted intermediary between the world of science and the armed forces, and Wimperis suggested that "an excellent Chairman might be found in Mr. Tizard, the present Chairman of our Aeronautical Research Committee and a former R.F.C. pilot."

2The contacts in this circle could be described, without flippancy, as "clubland at war." Thus, Tizard wrote to Air Marshal Dowding on October 19, 1937: "I have

arranged for Blackett to come to lunch with me at the Athenaeum on Thursday

325

326 Andrew Nahum

action on engines parallels what was being done at high levels of

government to bring into being the radar chain. Edward Bridges, the immensely influential official at the Treasury with deep responsibility for rearmament, wrote to a colleague elliptically about radar: "I should be happy to pass on orally such parts of the explanation as I was capable of understanding, but I should be sorry to have to write them down. I gather that ... this line of research is certainly worth pursuing."30

The reaction of Ricardo to discussion of a sprint engine for home defense in December 1935 was improbably quick, and it is further evidence that the sprint engine was already under consideration by him, for on January 10, 1936, he submitted his paper "High Power

Two-Cycle Engine for Special Purpose Machines," which proposed "an aero-engine of very high performance for short flights only without the usual regard for fuel and oil consumption but with high specific output and small frontal area."31 He estimated that 80 to 90

horsepower per liter could be achieved. The new (four-stroke) Rolls-

Royce Merlin was then coming into production with a power of 955

horsepower, so Ricardo's projections implied that a two-stroke of the same size (27 liters) would be able to deliver some 2,400 horsepower. At the meeting in February, the committee was exclusively occupied with this and other strategies for developing high-power engines.32

During the discussion, Tizard observed disingenuously that "the

subject provided not only an interesting research problem but a

question of very great practical importance. Defence machines were

likely to be in the air for comparatively short periods and hence fuel

consumption was of less importance than . . . the utmost possible

... would you like to join us? Blackett is, as you know, a member of the Committee and is interested in the Biggin Hill work." Tizard Papers, HTT 131, Imperial War Museum (IWM). Ricardo also has recalled that "we were members of the United

University Club where we frequently lunched together." Ricardo, Memories (n. 11 above).

3?Edward Bridges to Alan Barlow and Sir Richard Hopkins, March 1935, File T.161/891/s.26350/01, Public Record Office, London. See also G. C. Peden, British Rearmament and the Treasury (Edinburgh, 1979), essential to an understanding of prewar British rearmament. He quotes SirJohn Simon, chancellor of the Exchequer, on Bridges's departure to the Cabinet Office in 1938: "A fearful loss to me and to the Treasury, for he has every aspect of rearmament at his finger tips."

31File DSIR 23/5441, Public Record Office, London. 32The sense of urgency was reflected in an RAE inquiry into raising the power of

existing RAF engines by special fuels and supercharging, if a shorter life was ac-

cepted, taking the example of the 2,330-horsepower Rolls-Royce R racing engine for the Supermarine S.6B seaplane in the 1931 Schneider Trophy contest. "Engines of Specially High Power," January 1936, File DSIR 23/5511, Public Record Office, London.


power output and the maximum excess of speed over that of the

opposing machine." The phrase "the maximum excess of speed" in this context is conclusive evidence for the influence of radar on

engine planning and echoes exactly a conclusion in the minutes of the first report of the Tizard Committee some months before, which noted: "The maximum possible excess speed of fighter over bomber aircraft is required." This was almost certainly an insight of Tizard himself, and it underscores how power plant development was seen

by him as an essential part of the development of an integrated air defense system.33

These perceptions of Tizard's concerning maximum excess speed of fighters and that "defence machines were likely to be in the air for comparatively short periods" were not, at the time, as unsurpris- ing as they may seem now. Prior to the use of radar, good fuel con-

sumption was an equally important requirement for fighters. The

warning period of bomber attack was short, and interception relied on "standing patrols" of fighter aircraft, ready at height (fig. 3). These patrols would be relieved periodically as their fuel became exhausted, and only a proportion of the defending force could be in the air at one time.34 However, with radar, the efficacy of the

fighter force could be enhanced greatly. Fighters could be hus- banded on the ground, climbing to interception when called, but an

analysis of this scenario in terms of aircraft speed and performance reveals that the window for a successful interception is quite small. The technical imperatives are shifted; engine power, to give good climb rate, and speed advantage become critical.35

The two-stroke engine that Ricardo proposed for these new circumstances was highly unusual. It was a sleeve-valve two-stroke, with uniflow scavenge in which fresh mixture was admitted through ports when the piston reached the bottom of its travel, while the exhaust

33First interim report of the Committee for the Scientific Survey of Air Defence, in "Formation of a Scientific Committee" (n. 28 above).

34How little speed advantage had been seen as a priority can be seen by the 1930 Air Exercises, when the streamlined Hawker Hart two-seat day bomber had proved faster than the single-seat fighters. A squadron was then equipped with Harts

adapted to serve as fighters, and in the 1931 Air Exercises, these were the only inter-

ceptors able to catch the attackers as they dropped tennis balls marked "Bomb" on RAF Northolt.

35The 1923 Steel-Bartholomew plan had established in southeast England an "aircraft fighting zone" partly ringing London and divided into sectors. Outside this was an artillery zone and, farther seaward, a belt of "advanced observer posts." See Basil Collier, TheDefence of the United Kingdom (London, 1957). These observers could

give generalized warnings, but there was no intention (or capability) to guide fighters accurately to an interception.

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328 Andrew Nahum

FIG. 3.-The proposed air defense map of southern England prior to the introduc- tion of the radar chain. The boxes A to Z were designated "aircraft fighting zones" in which fighters would patrol. Antiaircraft guns were to operate in another belt nearer the coast. (Courtesy of the Science Museum, London.)

exited at the top of the cylinder through the head. Thus, the ineffi- ciency of the common piston-ported two-stroke would be avoided. The engine was to be fueled by direct petrol injection into the cylinder head, and it was intended that all power control would be achieved by an ambitious technique: varying the fuel quantity injected, as with a diesel, and not by air throttling, as is usual with gasoline engines (figs. 4 and 5).

British Aero Engine Development 329

//Z

'i l I ,1 /

FIG. 4.-The Crecy stratified charge fuel injection system. At high power (left), sufficient gasoline was injected to fill the whole cylinder. At low power, since the air supply was not throttled, it was arranged that a reduced "dribbling spray" would be retained in the specially shaped bulb head, making the mixture there rich enough to support combustion. (Courtesy of the Science Museum, London.)

Support for this experimental path seemed, therefore, an act of considerable boldness for the committee, but in reality the ground for it had been prepared over many years by Ricardo. All the design strategies he had recruited to try to enable the diesel to rival the

gasoline engine were to be employed, and the new test engine, designated E65, was in all its essentials mechanically identical to the two- stroke diesel (E44) design that was intended to catch up with gasoline engine output. Provoked by Tizard to find a high-power configuration for the radar-directed interceptor, Ricardo converted his "ultimate" diesel design to a spark-ignition fuel injection gasoline sprint motor.36

36Sir Harry Ricardo, The High-Speed Internal-Combustion Engine, 4th ed. (London, 1953), p. 364. "We ... converted one of the existing [diesel] two-cycle sleeve valve

330 Andrew Nahum

An Elaborate Instrument of War

The ensuing R&D effort to improve the performance of interceptor fighters must be seen in the context of a national resolution to create an adequate air defense system. This resolution can be

glimpsed through official communications as well as personal memoirs, and it reflects a unity of purpose that spanned government de-

partments, including the Air Ministry, the Treasury, the DSIR, and the Post Office.

The first hint, in Britain, that a long-range detection system might work dated from January 1935, when Robert Watson-Watt, superin- tendent of the Radio Division at the National Physical Laboratory, responded to an inquiry from H. E. Wimperis, director of scientific research (DSR) at the Air Ministry, to investigate the possibility of a

"Death-Ray" defense against aircraft. His negative assessment ended with the low-key statement that "meanwhile attention is being turned to the still difficult but less unpromising problem of radio detection as opposed to radio destruction."37

In August 1935, Wimperis recommended further experiments, noting that "the discovery of this means of detecting and locating hostile aircraft promises a revolutionary improvement in defence measures.... Mr Tizard ... strongly supports them and regards their authorization as urgent." The political head of the Air Ministry, the

secretary of state for air, Lord Londonderry, added: "This must be done. Treasury are as anxious as we are to pursue this investigation." In August of the same year, an Air Ministry official, J. S. Ross, discussed with Edward Bridges the finance for extensions to the Orford- ness experimental station for radar research. He noted: "I discussed the whole tentative programme of air defence with Mr. Bridges of the Treasury, to prepare the way. He was entirely receptive and helpful." Bridges wrote in confirmation: "I gave oral authority for the immediate extensions at Orfordness."38

engines [to gasoline] and almost at once obtained a very high output, far in excess of that of any contemporary aero-engine." "Final Report on the Two-Cycle Petrol Injection Sleeve Valve Units," Ricardo & Co., Ministry of Supply 1947, Science Mu- seum archive.

37 "Formation of a Scientific Committee" (n. 28 above). The original request from Wimperis has been regarded as naive, Watson-Watt referring to the "low-brow Death-Ray." The Star Wars program has made it seem less fantastical. Wimperis observed that "one of the coming things will be the transmission by radiation of large amounts of electric energy .... No avenue however seemingly fantastic must be left unexplored." He sought advice from physiologist A. V. Hill (who also had worked in air defense in World War I) and learned that "in a laboratory experiment on these lines the skin was burnt off the tail of a rat."

38"Formation of a Scientific Committee."

-f I ) /j

FIG. 5.-The valve operation cycle in the Crecy. Fuel injection and ignition occur at the top of the stroke as shown in figure 4. Then (left), as the piston descends the sleeve is moved, by its own drive link, to drop and uncover the exhaust ports at the top. Cylinder pressure falls (center), and the sleeve then moves to allow the inlet ports to open. Inlet air flows in while exhaust ports remain open, giving a "uniflow" scavenge of the cylinder. Sleeve movement (right) closes the exhaust ports while supercharged inlet air continues flow and boosts cylinder pressure. The cycle relies on an external supercharger (not shown) and is quite unlike the common two-stroke, which uses the crankcase as a pump. (Courtesy of the Science Museum, London.)

332 Andrew Nahum

Such actions, as G. C. Peden notes, are very far from the "tight- fistedness" or "Treasury meanness" that has been identified in

many accounts of rearmament.39 In the period from 1935 to 1939, the Air Estimate (in effect, the total RAF budget for research, procurement, and operations) went from ?17.5 million (1934-35) to ?56.5 million (1937-38) and reached ?74.5 million in 1938-39. (Over the same period, the proportion of GNP devoted to military purposes rose from 3 percent to 18 percent.) Such a rate of increase would have been inconceivable without wholehearted support from the Treasury. Indeed, Treasury activity went beyond merely fiscal duties and took on a surprising strategic dimension. Thus, we find

Bridges in July 1936 commenting on intelligence reports of the weakness of the French Air Force and Sir Warren Fisher, permanent secretary to the Treasury, annotating the paper: "All the more reason for a strong air force ourselves."40 The Treasury also used its influence to favor RAF expansion at the expense of the army and

navy claims in order to gain "a greater degree of security than we would get from the other two services" and prevailed on the Air Staff to alter the balance between bombers and fighters in favor of

fighters. Indeed, Warren Fisher's formal approval of the order for 1,000 Hurricane fighters at the height of the Munich crisis in Sep- tember 1938 bore the rider: "I hope I may infer that the Air Staff are seriously reconsidering the relationship between bombers and

fighters."41 The tactical implications of radar were absorbed by the Tizard

Committee with striking speed, and government officials showed themselves eager to help in its development. C. P. Snow has recalled

39Peden, British Rearmament (n. 30 above). Tizard also has noted that in this period "the Treasury was a very different place from that which I had been led to expect. It had departed from the practice of saving candle ends [and] never failed to take the bigger side of things into account." Sir Henry Tizard, "A Scientist in and out of the Civil Service," Haldane Memorial Lecture, Birkbeck College, London, March 9, 1955.

4Industrial Intelligence Reports on France, File T161/842/541152, Public Rec- ord Office, London. In the following year, Bridges noted on another report on French aircraft production, "an intensely depressing paper."

41Quoted in Peden, British Rearmament, pp. 128-33. The general strategic view, which was beginning to change, had been that a successful fighter force could only buy time. Thus, even Dowding questioned rhetorically the long-term value of fighter defense: "What do we gain? A respite only.... The enemy pauses while he armours his bombers ... and then returns ... unless in the meantime [our] bombers are

systematically destroying [his] machines, reserves, factories, and fuel supplies." Air Chief Marshal Sir Hugh Dowding, "Employment of the Fighter Command in Home Defence," lecture at the RAF Staff College, May 24, 1937, File AIR 16/260, Public Record Office, London.


that "within a very short time the Tizard Committee were asking for millions of pounds, and getting it without a blink of an eye. Two successive secretaries of the Cabinet, Hankey and Bridges, did much more than their official duty in pushing the project through."42

At the end of May 1935, the committee was bold enough to antici-

pate radar detection at 60 to 100 miles (although the initial trial three months earlier had been carried out at only 8 miles range) and recommended moving the Aircraft Fighting Zone farther east. It also asked for more realism in interception exercises.43

A crucial element in learning to make the best use of radar was the appreciation that "the interception problem was different to the detection problem."44 Even given successful radar detection, the

control, position plotting, and direction of fighters to their targets constituted a quite new set of operational procedures that needed to be developed. So vital to success did Tizard judge this element to be that he persuaded the RAF to undertake trials to develop the

technique even before the radar chain was in place, and, at his direct

instigation, a series of exercises was set up from February 1936 (the Biggin Hill Interception Trials), in which an aircraft flying a known track was used to simulate an intruder, and its position plots were

passed to the embryonic fighter control system as if they had come from actual radar detection. This information was then used to

guide the fighters involved in the exercise by radio.45 Tizard pressed, too, for a plotting table map of the type that, in

fact, became indispensable for conducting the eventual Anglo-Ger- man air battle in 1940, noting that "the ideal would be to obtain, on the ground, a complete picture of the positions and movements of all hostile bombers and defending aircraft ... to enable fighter aircraft to be directed by radio telephony, towards particular hostile bombers."46 Indeed, he took an active interest in the design and

progress of the interception trials and was frequently present in the

operations room. He also was credited with devising the geometrical procedure used by ground controllers for redirecting intercepting

42Snow, Science and Government (n. 8 above). 43By March 1936, the new 240-foot aerial towers at Bawdsey Manor, near Orford-

ness, located an aircraft at 75 miles range. This installation was the prototype for the Chain Home stations, which were built to ring the coast of southern England by 1940.

4R. V. Jones, "Tizard's Task in the War Years," in Farren, "Henry Thomas Ti- zard" (n. 12 above).

45"The Biggin Hill Interception Trials," File AIR 2/2642, Public Record Office, London; also Farren, "Henry Thomas Tizard."

46Minutes of May 23, 1935, and First Interim Report, May 16, 1935; "Formation of a Scientific Committee" (n. 28 above).

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334 Andrew Nahum

fighters when the bomber target changed course.47 This simple algo- rithm for vectoring the fighter was known by controllers as the

"Tizzy Angle." Tizard's approach to the use of radar, in conjunction with a con-

cern for the development of power units to suit the new role, shows an extraordinarily sophisticated and holistic view of the integration of fighter aircraft, radar detection, and control by radio, long before the term weapons system became current. Virtually every element of the ensemble concerned him-even the aircraft guns, so that we find him, for example, asking the RAF for particular ballistic tests: "The Chairman specified his requirement for the next test as how

many shots, within what group, were required to get lethal damage on a wing. The relative advantage of the .303 inch, 20 mm and 35 mm guns were discussed" with a comment from him on the omis- sion that so far "single shots had been considered, not the effect of a burst proportional to the rate of fire of a gun."48

A few months later, Tizard intervened to attack a problem with the supply of radar sets by Metropolitan Vickers, noting to the Air

Ministry: "I have written privately to the Firm suggesting that where

they feel they have a grievance it would be much better for one of their representatives to see you rather than to bottle it up." Through his mediation, the Air Ministry quickly reached agreement with the

company about price.49 The correspondence with serving RAF officers preserved in Ti-

zard's own papers for the period shows a tremendous interest and enthusiasm for the experimental interception program and acceptance of Tizard's central role in the development of the new systems. Thus, Air Marshal Joubert wrote in February 1936 to ask "if there are any special experiments that you would like carried out? These

47"'The tendency at first was to design complicated scientific instruments to ... solve the various triangles of velocities in three dimensions, but practical experience has shown that the technique of plotting courses on a black-board, and directing the fighters by R/T from the ground, has produced results of rather unexpected accuracy." Dowding, "Employment of the Fighter Command" (n. 41 above).

48"The DSR should provide scientific assistance for the tactical experiments shortly to be undertaken at RAF Northolt." Minutes, March 13, 1938, Committee for the Scientific Survey of Air Offence, File AIR 20/17, Public Record Office, London.

49 "I think it is a pity that the Air Ministry did not consult [the managing director] at an early date so that by now a firm order could have been reached for all the sets and an agreement as to price reached." Sir Henry Tizard to A. H. Self, Air

Ministry, October 28, 1937; and reply of November 8. Self replied that "the price position with Metropolitan Vickers has now been satisfactorily cleared ... this con- firms the oral representations you made as to the basis of the firm's quotation." Tizard Papers (n. 29 above), 140.


experiments would, of course, be additional to those we are already doing for you ... we shall be glad to do anything you may require."50 As R. V. Jones has put it, "there was in the Royal Air Force in 1935 a cadre of officers of exceptional outlook, who were prepared to work with the scientists with the utmost urgency towards development of the new air defence system."51 For example, it is sometimes overlooked that as air member for supply and research from 1935 (and subsequently as Joubert's successor as commander in chief of

Fighter Command), Hugh Dowding had responsibility for the devel-

opment and deployment, from the RAF side, of this system, which he was later to control in 1940 during the Battle of Britain-a back-

ground that, in part, must explain his effective and measured command of the British forces in the battle (for which he was much criticized) .52

The enormous reliance placed on Tizard can be glimpsed in an

exchange from Lord Swinton, successor to Lord Londonderry as

secretary of state for air, who wrote to thank him for agreeing to serve as chairman of another new body, the Committee for the Scien- tific Survey of Air Offence, in December 1936: "My Dear Tizard, I am terribly grateful to you. I seem to put more and more on you, and you always come up smiling; but you have got the confidence of all the services in a unique way." Tizard's letter of acceptance returned to the air defense problem, reporting, "I was at Biggin Hill

50Air Marshal Joubert, Officer Commanding the Fighting Area (subsequently Fighter Command), to Tizard, February 11, 1936, Tizard Papers, 64. Posted to India in the following year, Joubert wrote to Tizard: "I miss the contacts with people who are really alive and doing things in a most incredible degree . . . how I wish I was with you."

51R. V. Jones, "Tizard's Task in the War Years," in Farren, "Henry Thomas Ti- zard" (n. 12 above). The ground had been partly prepared, for by 1934, the RAF became concerned that if enemy bombers flying at 200 mph were detected when

crossing the coast, they could not be intercepted before reaching London. Joubert described interception attempts during the Air Exercises in the summer of 1934 as "a catastrophic failure." Joubert de la Ferte, Fun and Games (London, 1964), p. 88.

Study confirmed the problem was not in technique or training, and so moderniza- tion of operations rooms with dedicated telephone lines began before the possibility of radar was glimpsed. See Interim Report of Brooke-Popham Committee, File AIR 2/1386-95, Public Record Office, London.

52In his prophetic 1937 lecture (n. 41 above), Dowding observed that "the initia- tive rests inevitably with the enemy.... Will he send over single machines or very small formations.... Will he send formations in medium strength capable of self-

protection, and at intervals calculated nicely to find the defenders on the ground refuelling? Or will he depend on monstrous hammer blows delivered once every twenty-four hours by every available machine? . . . All I can say is that we must be

prepared for anything, and that our dispositions and tactical methods must be flexi- ble and adaptable." All these things came to pass.

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336 Andrew Nahum

yesterday. They are making excellent progress there-better than I had hoped."53

Personal Connections and High-Power Engines The putative connection between the growing promise of radar

and Tizard's support for the Whittle engine has been noted by Ed- ward Constant in The Origins of the Turbojet Revolution, where he

quotes from A. A. Griffith's 1937 "Report on the Whittle Jet Propul- sion System" these adverse comments: "In its present form, the proposed jet propulsion system cannot compete with a conventional

power plant in any case where economical flight is demanded.... It is only of value for special purposes, such as the attainment of

high speed or high altitude for a short time." Constant goes on to

suggest that with his secret knowledge of radar, "for Tizard, perhaps more than for any other man in England, the proposition of a very fast, high altitude fighter with a rapid rate of climb, even at the ex-

pense of sharply limited load and endurance, was not absurd."54 The progress of the two-stroke project and the overt linkage

shown here between radar and a high-speed interceptor engine demonstrate that Constant's supposition was entirely correct. In a 1938 paper, Tizard amplified this argument: "A fighting machine is of no use unless it has a substantially greater performance than any possible long-distance bombing machine. To get such a substantially greater performance we have one thing to rely on, namely that air endurance of the fighting machine need be quite small.... Hence fuel economy is of great importance for the bombing machine and of little importance for the fighting machine. Hence in trying to get very high-powered engines for the fighting machines we may disregard the importance of extreme fuel economy. This may well lead to the development of a special type of engine."55

More informally, Tizard wrote to Ricardo: "what I want is an engine which gives a terrific power for its size and weight ... through a high consumption so that long distance bombing machines could not compete."56

The two-stroke and the jet engine both met these criteria. "Our best friend was Sir Henry Tizard, Chairman of the Aeronautical Re- search Committee," noted Frank Whittle.57 Tizard was also influen-

53"Formation of a Scientific Committee" (n. 28 above). 54Constant, Origins of the Turbojet Revolution (n. 2 above), pp. 190-91. 55Sir Henry Tizard, "Future Designs of Fighting Machines," September 1938, Ti-

zard Papers (n. 29 above), 10/11. 56Tizard to Ricardo, letter of May 25, 1938, Tizard Papers, 77. 57Frank Whittle,Jet (London, 1953). Tizard had a great sense for energy in people

and projects. He noted later of the rival "government" axial flow jet engine based


tial in encouraging the separate gas turbine work undertaken by government scientists. Hayne Constant at the Imperial College, London, had worked at the RAE under A. A. Griffith and was to return there to take up the mantle of Griffith's work on axial flow gas turbines. Constant wrote: "I remember a conversation with Mr. Tizard, the rector of the Imperial College, probably early in 1936, in which he asked me what was the most worthwhile research to be done in the engine field. I told him of my hopes of the turbine and he gave an encouraging reply .... It was Tizard's imagination and enthusiasm that provided the drive during those critical days."58 In March 1937, at the request of the Engine Sub-Committee, Hayne Constant submitted an RAE paper, "The Internal Combustion Tur- bine as a Power Plant for Aircraft." It concluded that an efficient gas turbine was now attainable, and in May 1937, the Sub-Committee recommended that "the Air Ministry should take up the ... development of the Internal Combustion Turbine as a matter of urgency." Official support for both Whittle's project at PowerJets and the government work at the RAE stems from this.59

To return to radar, this direct personal intervention parallels Ti- zard's conversations with another research worker at the Imperial College, Robert Hanbury Brown. "The year was 1935 ... I told him I was working for a Ph.D. in radio engineering ... and hoped to combine an interest in radio with an interest in flying, perhaps in the RAF. 'Aha!' said the Rector, 'in that case I think I have ajob for you. Come and see me in a year's time,' and off he went like a rocket. . .. Three months later he pounced on me at a conversazione ... the Air Ministry was starting some new research.... He had already sent my name in.... He told me to present myself at the Air Ministry for an interview in ten days time. There would be no paper work, no applications forms-it was all very mysterious."60

on the RAE aerodynamic design that "Metropolitan Vickers were making progress but only slowly. There was no real drive behind it." Tizard Papers, 11/27.

58Hayne Constant, "Influence of the R.A.E. on the Early History of the Gas Tur-

bine," Engine Department, R.A.E., September 10, 1942, Science Museum archives.

Hayne Constant became director of the new National Gas Turbine Establishment, near Farnborough, after World War II.

59Hayne Constant, "The Internal Combustion Engine as a Power Plant for Air-

craft," March 1937, File DSIR 23/6149, Public Record Office, London. Constant was a late convert to pure jet propulsion, believing, with Griffith, in the more fuel- efficient propeller turbine, but now made the telling point that "in comparison with an airscrew the jet becomes more attractive as the speed of flight increases, for not

only does the propulsive or Froude efficiency increase but the efficiency of the airscrew decreases." Hayne Constant, "Memorandum on Jet Propulsion and the Gas

Turbine," File DSIR 23/7577, Public Record Office, London.

60R. Hanbury Brown, Boffin: A Personal Story of the Early Days of Radar (Bristol, 1991).

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338 Andrew Nahum

It might be argued that this history is curiously contingent on events, personal encounters, and a network of friendships as much as on agencies, formal relationships, and procedures-a symptom, some might adduce, of the "British amateurism" that has been the

subject of comment by various writers. And this style of loose, individ- ualistic organization even operated in more established areas of de-

velopment, where it had outstanding achievements to its credit. The modification of the North American P-51 Mustang to become the

preeminent Allied fighter of the latter part of the war arose not from an official requirement but because a Rolls-Royce test pilot, Ronnie Harker, flew one under evaluation by the RAF in 1942 and considered that it would be much improved with a Merlin powerplant. Through informal channels the trial conversion was done at the Rolls-Royce flight test establishment in two months. The reengined Mustang proved 50 mph faster with greater rate of climb and extended range.

If this was amateurism, it was amateurism of a sublime kind-self- aware, self-deprecating, perhaps ironical, and masking immense dedication and ability. Sir William Hawthorne has recalled that for the first British jet flight in 1940, the fuel pump calibration on the Whittle W.1 engine was done with a milk bottle ("up to the 'U' in United Dairies"). When Hanbury Brown was sent to join the team

developing radar at Bawdsey Manor, near Orfordness, in 1936, he noted that there were no books on electronic circuitry "except Ra- dio Amateur's Handbook, the property of a colleague."61

Such anecdotes hint at a sense of play, and an attitude with links to what might be termed "the cult of cleverness" in prewar British academic science-a cast of mind that took pride in ingenious and critical experiments in which the quality of thought involved in their design allowed definitive results to be obtained from cheap appara- tus. This "string and sealing wax" tradition in British science took thrift as an intellectual virtue. Its equivalent in the field of engineering can be detected in the assertion that "if you need expensive production equipment, you are not very skillful."

It is also an attitude that implies a highly cohesive society in which this ironical style contributed to a shared rapport but which may, with hindsight, be misread. This was a group in which common objectives could be taken for granted, which inhabited a world founded

61Speech by Sir William Hawthorne to the Reactionaries (former PowerJets personnel), May 1991. Hawthorne came to the Whittle team via the RAE, and his academic background included First Class honors from Cambridge followed by a doc- torate taken at the Massachusetts Institute of Technology. R. Hanbury Brown, Boffin.


on trust and on personal recommendations, and where it would be assumed that individuals would act both professionally and in a private capacity for the national interest. This note from Tizard to Lord Swinton, secretary of state for air, in 1936 can be taken as typical of the nature of communication and the assumption of joint purpose within this group: "H. R. Ricardo, of whom I expect you have heard, has just returned from Germany where he has been shown the German engine developments. I think that it would be helpful to you if you had a talk with him. His news is very reassuring in some ways."62

The Development of the Rolls-Royce Crecy The engine that was being tailored by Ricardo to a new age of

reactive air defense was, as we have seen, a gasoline development of the Ricardo E44 diesel research unit, adapted to spark ignition.63 The proposed engine was a cocktail of exotic features that had never before been combined in a gasoline engine (and have not been since). These were, to recapitulate, two-stroke operation, uniflow

scavenge by single sleeve valve, and direct fuel injection into the

cylinder. In a gasoline engine, the control of power is normally achieved by restricting both fuel and air supply together ("throttling"), although this inevitably produces pumping losses. Power

regulation by controlling the fuel supply alone offers theoretically greater efficiency but is problematic, since the fuel-and-air mixture must be kept within narrow limits to allow combustion. As power is reduced by cutting the injected fuel quantity, the mixture rapidly becomes too "lean" to support combustion, and misfiring occurs. Ricardo proposed, therefore, a novel stratified charge system with

injection of fuel into a special bulb-shaped cylinder head so that at low power a rich enough local mixture would still occur near the

spark plug (figs. 4 and 5).64

62Committee for the Scientific Survey of Air Offence, File AIR 2/1866, Public Record Office, London.

63Nomenclature: the basis of the two-stroke was the Ricardo E65 cylinder design, and the project was often referred to as the E65, as well as simply "two-stroke." At

Rolls-Royce, the engine was also known as the P.I. or "petrol injection" engine, although the name "Crecy" was selected in 1940, when the first full engine was ordered. If other two-strokes had emerged, the names would have followed on from the Crecy in a series drawn from famous battles.

64This strategy had been tried by Ricardo many years previously, and it is an inter-

esting feature of the E65/Crecy concept that it embodied many elements that he had experimented with since boyhood. In 1902, he modified a home-built pumping engine, which raised water from a well, to operate with a bulb head and stratified

charge, as a result of attending a series of lectures by the eminent engine theoretician Sir Dugald Clerk. The low-power engine ran beautifully. "I became an enthusi-

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At Shoreham, Ricardo converted his E44 diesel single-cylinder test unit to gasoline and built new E65 experimental units. As encouraging results accumulated and the likelihood of war increased, enthusiasm grew at the Air Ministry for the two-stroke, and in February 1939, Pye (as DSR at the Air Ministry) wrote to Ernest Hives, now at the head of Rolls-Royce, to tell him that the E44 two-stroke diesel cylinder was being used as the basis for a very high-power gasoline en-

gine.65 Rolls-Royce converted its own experimental Ricardo-type single-

cylinder E44 unit to gasoline operation, and the diesel experimental staff was put to work on the new project. However, progress stalled. Three months before the outbreak of war, in May 1939, Ricardo wrote to Tizard in distress: "I was expecting to run across you at the Athenaeum.... I am afraid that Rolls are not doing anything about [the two-stroke], nor do I think they are really the right people to tackle it ... They are, I think, too cautious and slow and too meticu- lous."66

Provoked by this, Pye wrote to Hives at Rolls-Royce, noting: "I was

surprised and disappointed to learn recently that you had not been

getting on with the two-stroke petrol injection project, as was agreed during our discussion at Derby on Feb. 1st." Hives countered that "the position is not anything like as bad as you imagine," but a few weeks later he wrote that there were problems with the Ricardo pattern open-ended (expansion) sleeve and proposed moving to the Bristol type with a piston ring seal in the head.67 Pye responded with

astic advocate of stratified charge operation, for so far it had worked like a charm. It was not until later that I discovered its limitations." Ricardo, Memories and Machines (n. 11 above).

65"With reference to our discussion yesterday about... the sleeve-valve two-stroke

petrol engine, I understand you are very anxious to try out the full possibility of this as a very high output engine. You are already acquainted with the type of cylinder on which very high outputs have been obtained by Ricardo .. . the Engine Sub- Committee consider that the development of engines on the two-stroke petrol injection principle should be given the highest priority." D. R. Pye, Air Ministry, to E. W. Hives, Rolls-Royce, February 2, 1939, Rolls-Royce Heritage Trust archive. An Air Ministry paper noted that "running was so successful that ... the firms of Rolls-

Royce, Napier and Bristol were asked whether they were willing to initiate development work on units and engines based on the E65 design." Bristol had no capacity, but Napier and Rolls-Royce both started work.

6"I have boundless admiration for their ability and their thoroughness, but ...

they are insistent that nothing short of perfection should leave their Works or bear their name and years roll by while they paint the lily." Ricardo to Tizard, May 9, 1939, Tizard Papers (n. 29 above), 78. Ricardo proposed that a prototype be transferred to

Douglas Pobjoy, the designer and maker, prewar, of a neat air-cooled radial for light aircraft, with Armstrong-Siddeley to build the production series.

67The normal sleeve valve, as employed by Bristol, used a "junk head," a cylindri- cal projection of the cylinder head with piston rings inside the top end of the sleeve

British Aero Engine Development the veiled threat that he "must consider what other possibilities there are for the development of a petrol two-stroke based on the Ricardo results with the expanding sleeve."68

Rolls-Royce did then set out to make the expansion sleeve func- tion reliably, but there must have been many such clashes, for the company culture of Rolls-Royce was certainly unique-isolated, con- fident, almost arrogant in technical capability. In 1945, a government review of engine production during the war observed that "Rolls-Royce ... never failed to show their peculiar mixture of engineering ability and intransigence."69 On the other hand, a letter from Ernest Hives to Major G. P. Bulman at the Air Ministry on the preceding diesel experiments shows the company's view of the quality of Air Ministry control: "The last thing that has happened is that we had a visit from Griffiths of the R.A.E. who asked to call in to go over our proposals. We are naturally always pleased to see Griffiths and have a talk to him, but if he is another member of a Committee to decide whether we are sensible or capable, then we shall not get very far."70

In 1940, the supply departments of the Air Ministry were combined into a new agency, the Ministry of Aircraft Production (MAP), to maximize production for the air war, but this administrative change did not reduce interest in the two-stroke. In 1941, according to a Ricardo account, MAP asked Bristol to try it, as well as Arm- strong-Siddeley.71 This urgent desire to extend two-stroke work stemmed from excellent results reported by Ricardo from the E65 units, while performance calculations by government scientists at the RAE at Famborough on hypothetical aircraft installations were highly encouraging. These indicated that an aircraft of Spitfire type fitted with a Rolls-Royce two-stroke engine would achieve "very high top speeds; speeds showing a considerable improvement over the best possible performance with a four-stroke engine of similar di-

which sealed it as it rose and fell. Ricardo's two-stroke used an open-ended or

"expansion" sleeve, a "cheeky" mechanical design without ajunk head which relied

simply on the fit of the sleeve in the cylinder for sealing. The sleeve clearance was, to a certain extent, self-regulating because of the effect of thermal expansion and was described by the Ricardo company as "a real breakthrough."

68"I remember that we were all very delighted when it was found possible to work with the expanding sleeve, and thought it would mean an all-round improvement in power and endurance." Letters between Pye and Hives, Rolls-Royce Heritage Trust.

69D. A. Parry, "The Production of Reciprocating Aero Engines 1935-1945," File CAB 102/51, Public Record Office, London.

70E. W. Hives to G. P. Bulman, Air Ministry, March 9, 1938, Rolls-Royce Heritage Trust.

71E. N. Soar, The History of Bridge Works (privately published, Shoreham, 1975).

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mensions," providing that the engine exhaust could be utilized effi-

ciently in a propulsive jet.72 Part of the reason for the importance of exhaust thrust was the

Crecy's huge throughput of air. The engine was highly supercharged both for power and to ensure a thorough scavenge of exhaust, since, in the two-stroke, there is no separate piston stroke to achieve this clearance of exhaust products. In addition, the two-stroke Crecy had twice the number of exhaust periods of the four-stroke and more than twice the net airflow. The efficient utilization of the energy in the exhaust promised the recovery of much of the work expended in supercharging. The simplest solution was to use the exhaust as a

propulsive jet, although the exhaust noise was so high that some wondered if it might be unsuitable even for military duties. However, this jet thrust element was important, for it helped to offset the reduced efficiency of the propeller at high speed. The large airflow

through the engine and its tolerance of exhaust back-pressure also

suggested the possibility of exhaust turbocharging, a proposal that

originated in late 1939 or early 1940 from the gas turbine pioneer A. A. Griffith.

A surprising facet of the two-stroke revealed by the RAE studies and not anticipated in the original sprint engine proposal was a good fuel consumption at high power outputs. A report in September 1942 compared the two-stroke with the gas turbine for a six-cannon

fighter of four-hour endurance and noted that the (then) high fuel

requirements of the gas turbine would give "a very cumbersome

aeroplane ... certainly not an efficient fighter," and the two-stroke would be better.73

This discovery that the unit did not suffer from high fuel consumption, the typical defect of the ordinary two-stroke, was a great at- traction, particularly after 1940, when the Battle of Britain was over and the threat of invasion had receded, for a large number of different roles and missions for aircraft came under scrutiny by military planners. Many of these seemed to suit the Crecy, and a 1943 RAE paper concluded that "compared to the Merlin 14 S.M. four-stroke engine the 2-stroke gives a small improvement in the top speed,

72A. W. Morley and C. M. Fougere, "Estimated Performance of a Spitfire (Rolls- Royce Two-stroke Engine)," RAE Report E.3962, March 1942, Rolls-Royce Heritage Trust.

73R. Smelt and A. W. Morley, "Comparison of Fighter Designs Utilizing the Rolls- Royce Two-stroke Engine or aJet-propulsion Unit," RAE Report, September 1942, File DSIR 23/11940, Public Record Office, London. "The conditions under which the engine appears most promising will be the same as those under which the pure jet... can be most usefully applied, i.e. at high speeds and great altitudes."


range and take-off distance of almost any aircraft. It would have its best application in long endurance fighters (escort and naval), in long range fighter bombers, heavy bombers and civil aircraft."74

Thus, the two-stroke was developing its own performance profile, which was rather different from the role originally planned for it and also distinct from either the four-stroke or the gas turbine. In May 1944, Ben Lockspeiser, Pye's successor as DSR at the MAP, had a meeting with Rolls-Royce in Derby on two-stroke work. He noted "M.A.P.'s keen desire to back up this . . . development to the maximum possible extent" and referred to the "advantageous position [of the two-stroke] as a link between the piston and jet engines."75 This implied a concern that there would be an operational gap between the new short-range, high-speed jets and slower, long-range, piston-engined aircraft, which it seemed the two-stroke could fill.

The encouraging performance studies for the Crecy were theoretical projections based on the experimental running of the single- and twin-cylinder engines by Ricardo, at Rolls-Royce, and at the RAE. They may well have proved accurate, but the development of a ser- viceable engine was proving difficult with problems in many areas.

Much of the development work was done on V-twin units. Eight V-twins were built by Rolls-Royce, of which one was supplied to Ri- cardo and another to the RAE, Farnborough (figs. 6 and 7).76 Six full twelve-cylinder engines were built at Derby and between them completed something under 2,000 hours of running-a small total for a project of which so much was expected.

By April 1942, writing to Air Vice-Marshal Linnell, controller of research and development at the MAP, Tizard noted that "the history of [Crecy] development is an unhappy one."77 At the Engine

74C. M. Fougere, "Note on Applications of the Rolls-Royce 2-stroke Engine," RAE Report, November 1943, File DSIR 23/13222, Public Record Office, London.

75Engine Sub-Committee, Minutes of Meeting at Derby on May 31st on 2-stroke Engine Development, June 8, 1944, File DSIR 23/13629, Public Record Office, London.

76The V-twin configuration (rather than the single-cylinder types usually employed for initial experiment) was chosen to test the sleeve drive mechanism for the full twelve-cylinder engine in which each pair of cylinders shared a common drive from an eccentric on the crankshaft.

77Ricardo objected that "Rolls-Royce do not pay enough attention to other people's experimental work, and instead of developing along lines which have been shown to be profitable, vary the conditions for no particular reason." Linnell replied that "you would naturally expect Rolls to have another side to the story. This is to the effect that while Ricardo does his extremely valuable work on a laboratory basis at modest coolant, oil and boost temperatures, Rolls-Royce very properly carry out their work under conditions representative of the engine as it will be used by the Royal Air Force." Although Tizard pressed for a 2,000-horsepower engine from

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FIG. 6.-One of the Rolls-Royce V-twin two-strokes on which much of the development running was done. (Photo courtesy of the Science Museum, London.)

Sub-Committee in September, he commented that he "had hoped at one time that it would take the place of the Merlin. This was not to be, it seemed, since the two-stroke was not ready." Rolls-Royce stated that the main problems were now mechanical-in particular, the use of austenitic steel sleeves which were difficult to wet with oil (fig. 8).78

Rolls-Royce in 1943, preferably the Crecy, the MAP view, based mainly on Rolls- Royce advice, was that it was not far enough advanced to be included in the production program for 1944. Tizard Papers (n. 29 above), 317.

78InJanuary 1943, Tizard wrote to Stanley Hooker at Rolls-Royce: "I shall certainly be surprised if you do not come to the conclusion that the two-stroke should be

British Aero Engine Development ?

rt r..~.r

FIG. 7.-A Rolls-Royce V-twin unit on dynamometer brake test at the RAE during World War II. The engine can just be discerned among the pipework at left. It is receiving supercharged air from a Rolls-Royce Merlin supercharger and intercooler (right) powered by an electric motor. (Photo courtesy of the Science Museum, London.)

By July 1943, the committee heard that the sleeve problem had been solved but that "piston cooling was still an unsolved problem. The piston required 35-40 gal./hr./piston, and so far, it had not been possible to get this quantity of oil up the hollow connecting rods." At this meeting Stanley Hooker, in charge of supercharger development at Rolls-Royce, discussed the relative power of Merlin and Crecy, suggesting that the Crecy would be 25 to 30 percent more

powerful than a Merlin, when both were fitted with the most effective

type of ejector exhaust manifolds, though Spike Corbitt, one of the senior development engineers on the Crecy, took an even more opti- mistic view, looking to improvements in valve timings, ports, and

turbocharging to lift the Crecy advantage. A comparison in Septem- ber 1944 by Corbitt offered the promise of a 50 percent power advan-

tage for the Crecy and a 15 percent improvement in fuel consumption at 15,000 feet, when turbocharged, compared with a similarly equipped Merlin. However, his paper also revealed the dispiriting fact that in actual tests, the Crecy had so far been worked up only

strenuously developed but I hope I am scientific enough to change my mind if the right evidence is produced." Tizard Papers, 426/1.

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* . i . . ,:

' ., :

FIG. 8.-A pair of Crecy sleeves with a large ring eccentric, which ran on the eccentrically machined crankshaft web to control the motion of the sleeves. (Cour- tesy of Rolls-Royce PLC.)

to 1,600 brake horsepower at 2,600 rpm, compared to 2,340 brake horsepower from the current Merlin at 3,000 rpm.79

The many development problems included cracking and structural failures in big ends, crankcase, and cylinder heads. At one point, following a series of failures, no engines were run for eight months-an extraordinary gap in a wartime program. Most of these problems were solved, but random piston failure remained the most serious unexplained occurrence and was probably caused by an air- lock and supply failure for the oil cooling spray onto the underside of the pistons. Other problems involved the magneto ignition and the high-speed fuel injection equipment, for these accessories derived from four-strokes and ran at twice their design speed in the two-stroke application.

Fuel injection and ignition trouble may have been responsible for the elusive problem of unstable running for which no cause was often found. In 1946, the RAE noted that their Rolls-Royce V-twin unit "with the exception of only two occasions ... never ran really steadily." The unpredictable nature of the performance of the E65 units is also dwelt on in a 1945 MAP report, which commented that "it should have been possible for a unit or engine to complete a type test to any schedule within the framework of the tables shown... Many lengthy uninterrupted runs at fairly high powers have been made successfully but attempts to repeat them under apparently identical conditions usually failed."

79Meeting at Derby (n. 75 above); and "Comparison of Merlin & Crecy Engines," internal Rolls-Royce paper, October 14, 1944, Rolls-Royce Heritage Trust.

British Aero Engine Development In December 1944, a full twelve-cylinder Crecy (with mechanically

driven supercharger) reached 1,798 brake horsepower, the highest power achieved on the testbed, and 2,500 brake horsepower was ex- trapolated from this for a flight-configured turbocharged engine. These figures appear to vindicate Ricardo's initial assumptions in his 1936 paper, which launched the "sprint engine for special purpose machines," although, at the outset, no one thought that development would take so long. But we should also note that at the end of the war, one Merlin variant was certificated for flight at 2,340 horsepower-virtually the same power output that Ricardo had promised from the unconventional two-stroke, but won by patient incremental development of the regular four-stroke. The Crecy passed two 112-hour flight approval tests in 1945, but it was never flown.

By the end of the war, the two-stroke had revealed itself to be a far more subtle and taxing device than the deceptively simple "hot rod" engine concept devised by Ricardo in 1935 to counter the threat of aerial bombardment. However, the great progress being made with the gas turbine was making it the clear choice for future development effort. In July 1945, Rolls-Royce prepared a report for the MAP which was effectively the death knell of the Crecy:

It has always been the Rolls-Royce policy to place the whole of their technical facilities at the disposal of the Air Ministry for the purpose of maintaining the superiority of the Royal Air Force. ... We have undertaken the basic development of practically every type of aircraft power unit, including liquid- and air- cooled four-stroke engines, two-stroke engines with turbine combinations and a variety of complete turbine engine projects. At the commencement of these projects each had its particular merit, but during the process of development some were bound to go ahead of others as the general picture became more clear. ... As a result of this work we are convinced that the turbine engine will eventually replace reciprocating types for aircraft and it is just a question of how long the time will be.

Had the Crecy ... reached the stage of proven reliability [it] might have filled the gap whilst the turbine engine was being fully developed. A good deal of development remains to be done ... and we are convinced a better turbine engine will be in production before the two-stroke. Taking all these factors into account... we feel it would be a mis-direction of effort for us to continue further with any two-stroke development.80

80"The advantages [of] the turbine engine on the score of weight, power output, reliability, simplified installation, reduced maintenance and fire risk cannot be achieved on any types of reciprocating engines and we believe there are potential possibilities of competing favourably in fuel consumptions." "Crecy Two-Stroke En-

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For Ricardo, the end of the war encouraged a series of extreme

high-power runs on a single-cylinder unit since a breakdown was now of less consequence. Using very high boost and water-methanol in-

jection to suppress detonation, the results seemed to show that the full twelve-cylinder turbocharged Crecy could have produced more than 5,000 brake horsepower, a figure that has led many to hold an extreme view of the potential of the engine. However, as we have seen, the two-stroke had proved an elusive device in development, and this extrapolation, though interesting from a technical point of view, must be regarded as contentious. The Aeronautical Research Committee, the godfather of the Crecy, in its review of work over the period observed, "Research had revealed that the two-stroke sleeve valve cylinder was capable of a maximum power output of

nearly double that of contemporary four-cycle engines," and offered an interesting counterfactual epitaph: "It seems probable that, had the turbine not materialised, the two-stroke would have proved the next step in the development of the aero engine."81

Conclusions

The two-stroke Crecy did not succeed. Although the initial performance projections were outstanding, it took too long to develop, and, like its progenitor, Ricardo's aircraft diesel, it was pursuing a

moving target of performance. Its relatively poor rate of progress compared to four-stroke engines did not give Rolls-Royce or government planners the confidence to increase the resources devoted to it. "It was never," one wrote, "sufficiently far in advance of the com-

parable Merlin production engines to be worth the risk of far greater effort being spent on it."82

By contrast, the gas turbine, even in its early state of development, was suggesting a massive change in aircraft potential. The persuasive

gine," paper by Rolls-Royce Ltd.,January 14, 1946, File DSIR 23/15147, Public Rec- ord Office, London.

81Aeronautical Research Council, Reviewfor the Years 1939-1948 (London, 1950). Rolls-Royce tests with its V-twin units indicated 3,000 horsepower might be possible-still an impressive figure. The mechanical endurance of the full engine was never established at these high outputs.

82A. W. Morley, Performance of a Piston-Type Aero Engine (London, 1951). During the war, the RAE had made the observation that "in any final assessment of the Rolls-Royce 2-stroke engine it must be remembered that the present rate of development is much less rapid than that of the 4-stroke. The 2-stroke's present margin ... may well be bridged by the 4-stroke by the time the 2-stroke reaches the manufac- turing stage."


point for contemporary development engineers, as Stanley Hooker recounts, was that the Whittle turbojet, in its crude early incarnation for the first jet flight in Britain, gave 800 pounds of thrust-almost equivalent to that of the highly refined Merlin engine and propeller ensemble at 300 mph.83 The Crecy had promised an incremental improvement to the piston engine, but this improvement was continually deferred.

Several historians of technology have suggested that issues of this type are susceptible to explanation by generalized theories of technological change, and in some ways the fate of the Crecy can be seen as evidence for the "variation-selection" model developed by Walter Vincenti.84 However, since to some the term selection implies a rather simple contest-a coarse trial of strength-it is worth noting that the neo-Darwinian model of biological evolution, from which Vin- centi's model is ultimately drawn, envisages a complex process in which the constant changes in all competing and coexisting species contribute to a continually changing milieu, making selection a subtle, coordinated, and mutual "game."

Surely this can be no less true for the process of technological change, with the added complication that, unlike selection in the biological world, selection between technological possibilities occurs partly on the basis of human judgment in anticipation of expected or hoped-for outcomes and test results. From the point of view of a formal evolutionary theory, this recursive element makes "blind" selection in biological systems rather different from that which oper- ates between devices engineered by humans. This also may help to show why engineering development can be highly contested and underlines the view that the history of technology must bring equal insight and analysis to the technical story, as well as the human and social one, in order to claim a special place as a powerful and informative system of study.

It could still be argued, of course, that the failure of the Crecy is an illustration of a "contingent and malleable path" for technology, and that the outcome depended less on its technical merits than on the allocation of personnel, resources, and funds. This kind of argument is hard to refute, and, indeed, almost everyone working in the Crecy team believed it could have yielded a powerful and effective aero engine if enough priority had been assigned to it, but a study of the culture at Rolls-Royce during this period shows that

83Sir Stanley Hooker, Not Much of an Engineer (London, 1984). s4Walter G. Vincenti, What Engineers Know and How They Know It (Baltimore, 1990),

pp. 241-57.

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both measurable technical results (testbed data) and anticipated performance were merged to provide a "sense" among senior engineering managers of the ultimate potential of this engine in relation to other projects.85

At the head of engineering direction for Rolls-Royce, Ernest Hives, who "believed in Rolls-Royce the way some people believed in God," could be described from our perspective today as a deter- minist.86 A tough, highly pragmatic engineer, but not without a vi-

sionary streak, he had a powerful instinct for engineering development, was quite open-minded about what the company would try, and explored sleeve valves, two-strokes, diesels, the classical twelve

cylinders in V formation, twenty-four cylinders in a double flat-twelve

configuration, like the Napier Sabre, and both Whittle and Griffith

gas turbines. In a sense, he did preside over a kind of Darwinian

struggle among the various company teams working on each engine project.87

These groups competed for services such as prototype manufac-

turing and for test facilities, and the allocation of these was a result of interplay of long-range policy and short-term necessity. As in most

organizations, the power relationship among these rival groups was often invisible, though real, and derived in part from how peers per- ceived the progress and likely success of a project. For example, when A. A. Griffith's contra-flow, contra-rotating CR.1 gas turbine

project encroached on time for Merlin supercharger tests, the CR.1

85We should note David Noble's persuasive argument that technical viability is

"rarely if ever ... put to the rigorous tests of any disciplined natural selection." David F. Noble, Forces of Production (New York, 1984), p. 145. Of course, "disciplined natural selection" would require even-handed allocation of funds and engineering talent-a most improbable event. We might accept, though, that a process quite close to this was operating in Rolls-Royce, admittedly under the simplifying conditions of wartime and subject to the proviso that part of this selection is "anticipated."

86Lord Kings Norton (who, as Harold Roxbee-Cox, administered the Whittle program for MAP), conversation with the author, June 1990. Sir Alec Cairncross, one of the economists who planned production in the MAP, described Hives as "an

engineer who had an extraordinarily accurate judgement of the potentialities for

development. We could trust him for an honest and competent opinion.... On these difficult technical issues we never found hisjudgement at fault." Sir Alec Cairn- cross, Planning in Wartime (Oxford, 1991), p. 19.

87The sections set up at Rolls-Royce to develop the Crecy and other engines were

relatively autonomous. The Crecy group was made up of about fifty people, includ-

ing designers, draftsmen, gas flow specialists, development engineers, testers, and fitters. The relationship with other teams was partly adversarial, but this should not be overstated, for the great impression of Rolls-Royce at the time was of tremendous

spirit. "I never remember an argument about getting the job done." Dick Foster-

Pegg, reminiscences for the Rolls-Royce Heritage Trust.


turbine parts and test fixtures were summarily moved outside and into the yard by night.88

These development engineers were themselves continually reeval-

uating the programs, and there was more discretion and "elasticity" in their own allocation of effort than might be thought. Stanley Hooker, for example, as the main supercharger theoretician in

Rolls-Royce, could certainly have swung more effort from his group behind the Crecy if he had sensed that it was worthwhile.89

This pragmatic approach seems at odds with a process of "Kuh- nian revolution" or paradigm shift as advanced by Edward Constant for the replacement of the piston engine by the turbojet and which, since its original formulation in Technology and Culture, has been an appealing analysis of these events.90 It is worth noting that this prag- matism also is revealed at the higher level of policy and program direction by Tizard, Pye, and Ricardo in spite of many years im- mersed in piston engine development. This does not suggest a belief structure that Kuhn has compared to "orthodox theology," and nei- ther is it at all apparent that the transition by engine professionals from piston to jet work demanded anything as profound as what has been termed a "conversion experience."91 Thus, Ricardo, whose

8Geoffrey Wilde, who worked under Stanley Hooker on Merlin supercharger development, arranged this. "My responsibility ... was to allot time for them to do the CR.1 component testing on the Supercharger rig.... When ... test time far exceeded what had been agreed . . . the only way I could deal with the problem was to bring in the millwrights on the night shift to move their test equipment out into the yard-rough tactics I admit. They complained to SGH [Hooker], but he left me to deal with it." Geoffrey Wilde, "Dr. Griffith's CR.1," The Archive (Rolls- Royce Heritage Trust) 35: 85-92.

890f course, it always can be argued that innate conservatism may prevent full commitment to novel designs, but the culture at Rolls-Royce would be better regarded as ruthlessly pragmatic, rather than conservative. When the Whittle production program finally passed to them, Hives declared, "we do not look on the turbine engine as a new secret weapon, it is just another way of pushing an aeroplane along, except that at the present time it is not as good as the conventional engine." Postan, Hay, and Scott, The Design and Development of Weapons (n. 4 above), p. 222.

90Constant, The Origins of the Turbojet Revolution (n. 2 above). 91See, for example, J. W. N. Watkins, "Against Normal Science," in Criticism and

the Growth of Knowledge, ed. I. Lakatos and A. Musgrave (Cambridge, 1970), pp. 25- 37. It could be argued that the phenomenon of explanatory failure, which is at the heart of Kuhn's model, is inappropriate in any case to technological systems. The piston engine did not fail in a profound sense, and viable technological systems rarely do, as evidenced by the survival of technologies in particular niches, such as windmills and piston-powered aircraft, even after putative revolutions. However, to state Constant's argument fairly, he suggests that the failure was "presumptive"- that Whittle and others anticipated the future inability of the piston engine to keep up with aerodynamic advances that would make high-speed flight feasible.

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career had been utterly interwoven with the piston engine, writing to Tizard in 1940 (more than a year before a British jet was to fly), observed that "in the long run the turbine will be more reliable than the reciprocating units."92

In the light of this account, and of the eclipse of the piston engine, it might be tempting to regard the two-stroke attempt as misguided. Various commentators have attempted to identify the moment of

incipient "design impasse" when further investment of effort in a mature system becomes unproductive. The two-stroke Crecy perhaps could be characterized as baroque-offering relatively low performance returns in relation to the R&D effort expended, and at the

expense of the accretion of clumsy supporting technological "fixes."93 Constant has characterized another complex Ricardo piston engine scheme in a similar way, reflecting that "there is the echo ... of late Ptolemaic astronomy, the weary addition of epicycle to

epicycle to produce an increasingly complex and clumsy, if still functional, system."94 The analysis has an intuitive appeal.

And yet, if there had been no turbojet, might the Crecy still seem "Ptolemaic"? There are numerous examples of "successful" tech-

nologies in which one ad hoc solution or system has been added after another. Chemical process plants, for example, are constantly modified and extended examples of "inelegant" technik from which it would be rash to draw the conclusion of imminent obsolescence.

It also can be argued that notions of "simplicity" or "elegance" in engineering are misleading. Are they analogous to the concepts of elegance and economy in a scientific theory, or do they derive from a mere aesthetic standpoint? Certainly, Whittle's new jet en-

gine did seem deceptively simple in geometric arrangement, with a

compressor and turbine mounted on a single shaft, giving, in effect, one moving part. But this simplicity is illusory, for another order of

complexity is concealed within it; new, higher-order technologies such as combustion aerodynamics, high-temperature metallurgy, and compressor theory are subsumed within the design.95

92Ricardo to Tizard, February 26, 1940, Tizard Papers (n. 29 above), 78. The Ri- cardo company made a large contribution to the fuel control system of the Whittle jet.

93M. C. Duffy has characterized engineers attempting to improve complex ensem- bles reaching the end of their design potential as "dissipating their energies on

pseudo-innovations which they failed to interpret as warnings of the imminence of

design impasse." His concept of design impasse was devised overtly to argue for "a utilitarian role for history." M. C. Duffy, "Technomorphology and the Stephenson Traction System," Transactions of the Newcomen Society 54 (1982-83): 55-78.

94Constant, The Origins of the Turbojet Revolution, p. 150. 95The Wankel engine makes a thought-provoking parallel. Like the gas turbine,

it was promoted on the semimystical merits of "pure rotary motion" and the alleged


A helpful model for considering the conduct of research planning may be to regard wartime industrial managers and government planners, such as Hives, Pye, and Tizard, rather like investment or fund managers. They knew that the future of engineering development at the limits could not easily be predicted. Circumstances and requirements might change, informed predictions could turn out to be wildly wrong, and at the same time the planners and sponsors of advanced research were involved in a relationship of delicate tension with the protagonists of each development group, who, naturally, were committed to them and sincerely expected their own projects to succeed.96

The "currency" the planners were able to invest was, in effect, a precious quantum of the national aeronautical research and development effort, and they ran a portfolio of projects which ranged from high-risk experiments promising high returns, in terms of performance, as well as "blue chip" investments such as the Merlin, in which incremental and painstaking development might be expected to offer less, with less chance of failure. Both the two-stroke and the gas turbine promised this balance of high risk and return, although the strategic value of both turned out to be negligible for Britain, and it was the relatively conventional Merlin that proved the outstanding achievement, viewed purely in terms of the war itself.

A further striking feature of British wartime engine development is how much of it ended up in the control of Rolls-Royce. The ruthlessly optimized conventional Merlin engine, the two-stroke Crecy (a "failed innovation"), and the new turbojet, which came to be identified by Hives and his engineers as the natural successor to the piston engine. These three programs are, in a sense, paradigmatic examples of types of engineering development, and the relationship

simplicity and small number of its parts. This analysis ignored the new nature of combustion dynamics within it and the taxing materials problem of gas seals. The regular automobile piston engine, supported currently by catalyst, exhaust gas sens-

ing, and electronic control of fuel injection, has departed from the simplicity and almost naked "state of grace" in which De Dion and Olds applied it to vehicles at the turn of the century and yet shows little sign of becoming displaced.

96This kind of intriguing relationship can be glimpsed through the recollection of Lord Kings Norton (n. 86 above) that Air Chief Marshal Tedder, from the RAF side, wanted Whittle's program to be hidden from Lord Beaverbrook, minister for aircraft production. Although production was vitally needed in 1940, influential officers would not forgo the possibility of a radical improvement in aircraft performance. The polarization between vision and production, exemplified by Whittle and Beaverbrook here, is atypical; most engineers and administrators in the aircraft procurement program wanted to optimize production and performance-a posture that has been characterized by Postan, Hay, and Scott (n. 4 above) as "the doctrine of quality."

353

354 Andrew Nahum

between them is extraordinarily informative. But in studying such developments, we should not underestimate the simple creative desire among engineers to make something "better."97 Historians of technology have expended considerable effort in attempting general theories of the process of innovation, but perhaps we should consider more closely the views, actions, and emotions of these prac- titioners at the time. To reach the new and elusive plateau of performance and to manage their efforts and finances, inventors, engineers, businessmen, and government planners navigate a complex matrix comprised of threads of utility, economy, practicality, expedi- ency, engineering elegance, and hope.

97This creative desire can explain why new developments are sometimes pursued in apparent defiance of rational business strategy. Development engineers and even the heads of engineering companies are often more interested in performance than in profit, as Noble has observed of the machine tool industry. Forces of Production (n. 85 above), p. 9.

two-stroke or turbine-the aeronautical research committee and british aero engine

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