Frank Whittle (Icon Science)

The Invention of the Jet

Andrew Nahum

• Publisher: Icon Books
• Year: 2017
• Print ISBN: 9781785782411
• eBook ISBN: 9781785782565
• Topic: Technology & Engineering
• Subtopic: Science & Technology Biographies
• Index: Technology & Engineering

The story of the jet engine has everything: genius, tragedy, heroism, a world war, the individual vs. the state, and an idea that would change the world. Frank Whittle always maintained that he was held back by a lack of government support. At the very moment in 1943 when his invention was unveiled to the world, his company, Power Jets, was forcibly nationalised. Yet Whittle's brilliance, charm and charisma helped him recruit major support from the British government and the RAF, who gave him the green light to build a jet engine at a time when to do so made little sense. Here is a story of what pushing technology to its limits can achieve - and the effect that such achievement can have on those involved.

• CHAPTER 1 •

WHITTLE’S EARLY JET IDEAS

Frank Whittle entered the Royal Air Force as an aircraft apprentice in 1923. The three-year course on which he enrolled was designed to produce the aircraft mechanics and service personnel required to repair and maintain RAF aircraft. However, by exceptional ability and effort, he was one of only five apprentices (out of 600 in the initial intake) selected to go on to train as an officer cadet and pilot at Cranwell, the RAF training college. Whittle took a keen interest in aeronautical developments and in 1928 his contribution for the cadets’ termly thesis was entitled Future Developments in Aircraft Design. He anticipated a large improvement in aircraft speed, coupled with an increase in the heights at which aircraft flew, in order to take advantage of reduced air resistance at high altitude. He recognised that in a conventional piston engine power falls off with altitude and considered in some detail, as part of this overall view of aircraft evolution, the efficiency and thermodynamic design of a gas turbine. He observed that although a steam turbine would be impractical for aircraft owing to the weight of boiler and condenser, nevertheless ‘the turbine is the most efficient prime mover known [so] it is possible that it will be developed for aircraft, especially if some means of driving [it] by petrol could be devised.’

At this time Whittle considered using the internal combustion gas turbine to drive a propeller. In the following year he realised that a gas turbine could be constructed to produce a propulsive jet. This was an independent insight of his, which transformed the gas turbine problem. This jet engine idea had, however, been anticipated in remarkably modern form by Charles Guillaume, who had taken out a French patent in 1921 – something of which Whittle, as well as other jet pioneers, was not aware. He was also, naturally, unaware of (secret) work by the British research scientist A.A. Griffith at RAE Farnborough, on the idea of a gas turbine to drive a propeller – work which went back to 1926. Moreover, the gas turbine, in a heavy, industrial and relatively inefficient form, already existed and was employed in industrial plants where a cheap supply of combustible gas was available. For example, from 1914 the Thyssen company installed them at several steelworks in Germany where they ran on waste blast furnace gas.

However, the jet propulsion idea made the Whittle gas turbine/jet engine conceptually different from the propeller turbine, in which as much energy as possible is extracted as rotary shaft horsepower from the exhaust by the turbine stages. Whittle’s idea instead left as much energy as possible in the gas stream to form a high velocity exhaust jet. This simplification of the gas turbine made Whittle’s jet proposal attractive for development at a time when the combined inefficiencies of the compressor, the turbine and the required reduction gearing and propeller drive seemed, in aggregate, too great to make a propeller turbine unit viable.

The basic turbojet consists of three main elements – the compressor, combustion chamber and turbine (see Figure 1). Unlike the familiar piston engine, where compression, combustion and expansion (the working stroke) happen repeatedly and in succession, the gas turbine performs these same functions but under conditions of continuous flow.

The problems for such an engine, in the inter-war period, were that all the constituent parts seemed inadequate. First, although high-power compressors were increasingly well understood from supercharging high-power piston aero engines, like the Rolls-Royce ‘R’ and, later, the Merlin engines, they were not efficient enough and would rob too much power from a pure gas turbine engine. Second, continuous combustion at a high enough rate and in the high airflow required had not been attempted anywhere. Finally, devising a material for the turbine blades, which must stay intact while literally red hot, under huge centrifugal loads and at high rotational speed, was an unsolved conundrum. The exhaust valves of conventional piston engines, it is true, had to ‘live’ in a flow of combustion gas, but they experienced the worst conditions only intermittently, and for most of the engine cycle were held in the closed position, passing their heat into the cylinder head and engine coolant. In any event, exhaust valve performance was proving at that time to be a limiting factor in piston engine development.

Figure 1: The essential Whittle design. The double-sided compressor (to left) sends air to the double-walled combustion chamber. It reaches the turbine wheel after two 180-degree turns.

In 1929 Whittle’s commanding officer arranged for him to discuss his jet engine ideas at the Air Ministry, where he met W.L. Tweedie, a technical officer in the Department of Scientific and Industrial Research (DSIR), and A.A. Griffith of the RAE. The result, Whittle recorded, was ‘depressing’ and he subsequently received a letter stating that the engine was impracticable (for the time being) because materials did not then exist capable of withstanding the high temperatures and stresses that would occur in the turbine stage of the engine. The widespread impression of Air Ministry prejudice against the gas turbine at this time derives from Whittle’s account of this episode, in which he blamed his reception on ‘a very unfavourable report … that had been written some years before’.

Almost all subsequent authors have repeated Whittle’s impression of this report, by W.J. Stern, of the Air Ministry Laboratory, South Kensington, blaming poor Stern for holding back turbojet development by several years. In fact, Stern’s report was a professional piece of work which actually anticipated a successful aircraft gas turbine (rather than rejecting it out of hand) but noted that contemporary compressor efficiency was too poor to support a gas turbine cycle while heat-resisting materials for the turbine stage were not yet available. He suggested that ‘the internal combustion turbine will not be rendered practical by the revolutionary design of some lucky inventor. The steam turbine engineer and the metallurgist … are the people with whom the future development of the turbine rests.’ Incidentally, Stern, as a member of a special panel of the Aeronautical Research Committee (ARC) in 1930, did recommend construction of a turbine to the design of A.A. Griffith ‘if it would provide an unequivocal check on the theory.’

The important point about this episode is that Whittle had been taken seriously enough to be invited to discuss his proposals at high level. Although the letter (probably written by A.A. Griffith) intimated that the Air Ministry did not wish to pursue Whittle’s scheme at that time, it observed that ‘the internal combustion turbine will almost certainly be developed into a successful engine, but before this can be done the performance of both compressors and turbines will have to be greatly improved. However it has been of real interest to investigate your scheme and I can assure you that any suggestion submitted by people in the Service is always welcome.’ It was, an RAE turbine worker later observed, ‘a kind letter’.

Whittle, in his memoir, appears not to realise how exceptional such access must have been for a newly commissioned Pilot Officer: Griffith was then one of the most eminent Air Ministry scientists, a member of the Aeronautical Research Committee and had an important voice, through the ARC’s Engine Sub-Committee, in the national direction of aero engine policy. Griffith had also proposed his own gas turbine project (to drive a propeller) as early as 1926, which derived from his new, and highly influential, aerodynamic theory for axial flow turbine and axial flow compressor design. Griffith’s paper indicated that the then current axial flow compressors were inefficient because they operated with the blades in a stalled condition. Designing them in the light of aerodynamic theory (treating them, in effect, as rotating wings) would, he argued, allow a large increase in efficiency and make possible a practical gas turbine.

It is an important historical point, usually ignored in conventional jet histories, that from 1937 workers at the RAE (in particular Hayne Constant) began a parallel ‘government’ gas turbine programme. For speed of results, however, Whittle chose the single-stage centrifugal compressor, since it was relatively well understood from piston aero engine supercharging, while the RAE team concentrated on the theoretically more demanding, and then imperfectly understood, axial flow compressor (see Figure 2, and Plate 3 for a comparison of the two types of compressor). But this project was given less priority than Whittle was to receive, and indeed, some of the most able RAE personnel were seconded to the Whittle programme.

However, the RAE work proved highly influential, and ultimately the main axial flow development of post-war British aero engines was to flow from this work. Griffith’s ideas led to a line of transmission through the wartime RAE turbine work, which was the basis of an engine built by Metropolitan-Vickers, the ‘F2’ or Beryl, to its successor, the post-war Armstrong Siddeley Sapphire, and thence to Avon and the main post-war Rolls-Royce engines. Griffith, in fact, joined Rolls-Royce as Chief Scientist in May 1939. From this perspective, the Whittle engine, with its use of a centrifugal compressor, could be regarded merely as a temporary expedient. Intriguingly, in Germany, Pabst von Ohain, like Whittle an inventor from outside the aero engine mainstream industry, also used a centrifugal compressor for rapid results in association with Heinkel, but the German air ministry directed Junkers and BMW to use axial flow compressors developed in consultation with aerodynamicists at the Aerodynamische Versuchsanstalt (AVA) – in some respects the German equivalent of Farnborough.

Figure 2: An axial flow engine. This is unlike the basic Whittle centrifugal engine (see here), in which a vaned rotor ‘slings’ the air outwards to accelerate and compress it. Axial flow engines (most aircraft units today) compress the incoming air in stages as it passes through a series of rotors with wing-like rotating blades. (See Plate 3 for further comparison.)

Thus the attitude of the Air Ministry to Whittle can hardly be seen as negative or discouraging. In fact, its actions showed recognition and appreciation of Whittle’s aptitude and potential. This can also be seen in the Ministry’s decision to allow him to attend Cambridge University. Whittle completed the Officer’s Engineering Course in 1933 with distinction. The Air Ministry had, in the past, sent one or two outstanding officers from this course on to Cambridge to take the Mechanical Sciences Tripos but this scheme had been officially terminated in the preceding year. However, Whittle wrote formally asking for special consideration and, in view of his excellent results in the RAF engineering course, the Air Ministry, exceptionally, revived the scheme for him. Additional evidence of sympathetic and favourable treatment can be seen following his First Class Honours in the examinations in June 1936 at Cambridge, when the Air Ministry approved an application from his tutor for him to spend an additional postgraduate year there working with the eminent aerodynamicist Sir Bennett Melvill Jones.

• CHAPTER 2 •

THE FORMATION OF POWER JETS LIMITED

While at Cambridge Whittle received, in May 1935, a letter from a former RAF colleague, Ralph Dudley Williams,¹ c/o General Enterprises Ltd, Callard House, Regent Street (Manufacturers of Genterprise All British Products). Williams wrote:

Just a hurried note to tell you that I have just met a man who is a bit of a big noise in an engineering concern and to whom I mentioned your invention of an aeroplane, sans propeller as it were, and who is very interested … Do give this your earnest consideration and even if you can’t you might have something else that is good.

General Enterprises, the unlikely bridgehead for the ‘turbojet revolution’, in fact marketed an unglamorous and technically undemanding product – a coin-operated cigarette vending machine – and had been formed by Williams and his partner, J.C.B. Tinling, also a retired RAF officer, with a loan of £1,500 from Williams’ sister. Williams recalled that the spur to his contacting Whittle again was a chance meeting at lunch with Tinling’s father, a consulting engineer (‘very able’) who observed, ‘there’s a war coming – why don’t you chaps get into the aircraft business.’ (After the war Tinling’s father, J.A. Tinling, attempted to claim a share of credit for the development of the jet, writing in 1944 that ‘an entirely false impression had been given to the world at large’, while his second wife, Daisy Tinling, claimed that ‘it should be known and publicly acknowledged that it was primarily my husband’s vision and foresight in 1934 which led to the discovery of Whittle … my step-son was merely an interloper who evidently set out from the start to crib his father’s idea and only made a success through his father’s financial connections. That may be very clever but it’s not cricket … But for my fancying a lobster at Verrey’s [a well-known Regent Street restaurant], on that particular day, … the Whittle plans would still be in the bottom drawer.’

R.D. Williams had been a fellow cadet with Whittle at the RAF College, Cranwell, in the September 1926 intake. Their batman introduced them, as they were to share ‘digs’. Williams, in a striking phrase that echoed the impact Whittle had on many of his associates, recalled later, ‘I just fell for him’, and that ‘I was the person who got on with Frank best.’ They remained lifelong friends and, after the war, Whittle even gave an ‘eve of poll’ address for Williams who was standing as Conservative parliamentary candidate, although Whittle then was a socialist.

Whittle struck a deal with Williams and Tinling, whereby they would seek commercial backing for the engine and would finance further patents. In return, they were to have each a quarter share of the commercial rights in the engine. They also agreed, at Whittle’s insistence, that they would not approach any firms connected with the aircraft industry, because he feared that a big firm might take over the idea, and a patent battle would be too costly to fight. Various approaches to financiers and industrialists failed, until Tinling’s father put them in touch with an able consulting engineer and patent agent, Mogens Bramson, who took the engine proposal to the City investment bank O.T. Falk.

Little has been written about the firm of O.T. Falk, but its particular quality of unconventionality, compared with other merchant banks, and the personalities of its members, which included Lancelot Law Whyte and Sir Maurice Bonham Carter, forms a crucial part of the British jet engine story. The founder, Oswald Falk, had been Treasury Delegate to the 1919 Paris Peace Conference and had been described as ‘the only high-brow in the city’. Whyte considered Falk personally to be ‘one of the Englishmen best informed on the political and military developments in Germany’ and the partners and senior employees as ‘all exceptionally intelligent men, ethically liberal, and intellectually radical’. The bank was, he believed, ‘one of the important nuclei of anti-Hitler and pro-Churchill opinion in London at that time’, and it derived additional impetus for this stance since, it was said, Violet Bonham Carter, one of the most influential anti-appeasement campaigners (and wife of Maurice), was conducting a menage à trois with her husband and ‘Foxy’ Falk.

Lancelot Law Whyte was himself an unusual figure – a philosopher and an intellectual who had worked in, and kept up with, theoretical physics and who had a powerful interest in and sense of historical process. After Cambridge, where he worked for a time in the emerging field of atomic physics in Rutherford’s laboratory, he travelled to Göttingen in 1924, becoming friendly with Max Born and hearing Neils Bohr lecture on the new theory of the atom. Subsequently, in Germany, he met and had discussions with Einstein before deciding to leave academic life. He entered merchant banking through the mediation of Montagu Norman, Governor of the Bank of England. Norman sent him to see Sir Maurice Bonham Carter, a partner at O.T. Falk. According to Whyte, Norman broke his rule not to use his influence in City appointments because Whyte’s sister and Norman’s mother were both Christian Scientists. The City appealed to Whyte intellectually because ‘in the City one saw human desires being expressed in quantitative form. … Did stock market prices quantify human lusts in the same way as the clinical thermometer converted human pathology into a numerical temperature?’

Through his scientific training Whyte became the member of the bank most concerned with venture capital for proposals with a scientific or technical element, ‘raising money for the rare deserving cases’. Thus he became a director in the early 1930s of Scophony, the company established to exploit John Logie Baird’s television system, but nursed ‘a secret hope … that something wonderful would turn up for which I would throw over everything else.’ And although at first reluctant to meet, when told by Bonham Carter that ‘a young flight lieutenant had invented a new aero-engine’, he found this in Whittle. He wrote:

It was like love at first sight, the impression he made was overwhelming. I have never been so quickly convinced, nor so happy to find one’s highest standards met. Whittle held all the winning cards: imagination, ability, enthusiasm, determination, respect for science, and practical experience – all at the service of a stunningly simple idea: 2,000 h.p. with one moving part. This was genius, not talent. … That night I told my wife that I had met one of the great inventive engineers of our time. … it was like what I imagined was the experience of meeting a saint in a much earlier religious epoch: one surrendered to the enchantment of a single-minded personality born to a great task.

Whyte’s background in physics, his semi-mystical personality and his historical overview of the subject were crucial in conditioning his response to the Whittle jet. His reaction was more that of a historian of science and a physicist than that of a banker for, in evaluating it, he transferred directly to aero engineering the concept of ‘elegance’ which so often is advanced as a touchstone for the evaluation of mathematical proofs and scientific theories. ‘The elegance of the idea won me. Every great advance replaces traditional complexities by a new simplicity. Here it was in the iron world of engineering.’

Armed with a favourable report from Bramson, whom the bank had now formally asked to analyse the Whittle scheme, Whyte set out to raise capital and contacted Sir Henry Tizard for a supporting opinion. Tizard was, at that time, an important figure in the Aeronautical Research Committee, the body responsible for the overall direction and evaluation of research work done in the government research establishments, such as RAE Farnborough, and within the firms on Air Ministry contracts. He also chaired the Engine Sub-Committee of the ARC. Tizard was a scientist who was uniquely trusted by the Air Ministry and the RAF. This reliance on him resulted, in part, from his work in the early development of the technical and scientific testing of military aircraft in the First World War, when he came from Oxford as a research chemist, learned to fly and began systematic testing of aircraft performance and behaviour at the Martlesham experimental station in Suffolk.

However, the respect in which he was held also derived from his wide scientific understanding and his highly incisive and pragmatic judgement. In the period immediately after the First World War he did important pioneering work with the most notable independent British piston engine researcher and consultant (and influential member of the ARC Engine Sub-Committee), Harry Ricardo, and with David Pye (subsequently Director of Scientific Research at the Air Ministry) on the ‘detonation’ properties of fuels, leading to an understanding of how fuel quality limited piston engine output, and anticipating the standard ‘octane rating’ for petrol/gasoline that was established a few years later in the USA.

At the time of Whyte’s approach Tizard was deeply immersed in the development of the revived air defence system for the UK and in the debate about the possibility of German bombers delivering ‘a knock-out blow’ to Britain. The Committee for the Scientific Survey of Air Defence (more usually known as the Tizard Committee) had first met in January 1935 and, from the outset, became the nursemaid for...

Table of contents

• Cover
• Contents
• Title Page
• Copyright
• List of Figures and Plates
• Acknowledgements
• Dedication
• About the Author
• Foreword
• Introduction
• 1 Whittle’s Early Jet Ideas
• Endnotes
• Notes
• Bibliography