No technology for vertical flight existed and the armed helicopter was still many years off. The best that could be done was a fighter that could operate off grass fields. This led to a NATO specification resulting in the Fiat G91, powered by Bristol’s Orpheus engine, and in working relationships between NATO and Bristol which were to be crucial to the birth of the Pegasus.
    One of the four hot colonels, Pierre Gallois, was the senior air assistant to the French Defence Minister. It was one of Pierre Gallois's jobs to be in close contact with the French aviation industry, and from time to time he met a USAF Colonel called John Driscoll, who was the senior air officer in a NATO organisation based in Paris, the Mutual Weapons Development Agency (MWDA), funded by the Pentagon in support of NATO. Another contact was a former French aircraft manufacturer, of a particularly inventive turn of mind, called Michel Wibault.
    Wibault was about 56 or 57 when he was made aware of the NATO requirement for truly dispersible high performance aircraft. Wibault was highly creative and in 1919 built his own aeroplane and the following year created his own company. He remained in business until 1934 when he sold the company to Louis Breguet. He then worked as a consultant until the invasion of France in 1940 when he and his wife Marie Rose escaped to England. Marie Rose was very much a society woman in pre-war Paris and she had something of a reputation among wealthy men. Among her many friends was Thomas Hamilton, who spent a lot of time in Paris to promote his propellers.
    In London General de Gaulle appointed Wibault Technical Director of ‘France Forever‘, an organisation aimed at galvanising American support for occupied France; so the Wibaults moved on to New York. Michel got a job with Republic Aviation and joined Alexander Kartveli on the design of the XC-12, later known as the Republic Rainbow, and on the little Seabee amphibian. Thomas Hamilton introduced Marie Rose to Winthrop Rockefeller, and she in turn introduced him to Michel. That resulted in Rockefeller supporting Michel as an aviation consultant for the rest of his life.
    In the early 1950s, while still in America, Wibault started to look at vertical flight and over the next few years took out four patents, funded by Winthrop Rockefeller's Vibrane Corporation which provided support to Wibault. In his fourth 1955 patent application Wibault arranged his machine to have four centrifugal compressors, two in tandem each side, mounted on transverse horizontal axes. The compressors were arranged around the centre of gravity of the aircraft and were contained in casings which could be turned on their axes so that the exit nozzles could discharge down, or to the rear, or at any angle between. (ie what we now call vectored). The engines were shaft turbines, driving through gearboxes, with provision for one engine to drive pairs of compressors. He had a look at the Rolls-Royce RB109, which was to become the Tyne, but later realised that a single BE25, the Bristol Orion, would provide all the power that he needed. As a result he had exchanges with Bristol on its performance.
    By this time, John Driscoll of MWDA had met Wibault and advised him to concentrate on combat aircraft. This advice was timely, because not only was the need for a vertical take-off fighter emerging from the work of the four hot colonels, but Wibault had by then made a fundamental breakthrough in powerplant geometry. So he set about designing a realistic aircraft and seeking support for it. He talked to the French Defence Ministry, and although Colonel Gallois and René Pleven supported him, they made no progress because the Air Staff seemed more impressed with the work at Rolls-Royce Derby on lift jets. He also went to French aircraft manufacturers but they were more interested in what the Air Staff wanted, and to Charles de Gaulle, who had yet to become President of France but who Wibault thought could influence things, but de Gaulle told him that there wasn't any money.
    When eventually he had come up with a firm proposal, Wibault went back to John Driscoll who was spending MWDA money on the Bristol Orpheus for the G91 and having frequent meetings with Stanley Hooker and Bernard Massey, the designer of the Orpheus. So Driscoll invited Wibault to one of those meetings and had each make a presentation: Hooker on his engines and Wibault on his VTOL concept. That was the moment at which the partnership was formed: Wibault of the inventive, imaginative mind, and Bristol Aero Engines, purveyor of powerful lightweight engines.  
    Wibault produced a brochure, dated March 1956 and a copy was sent to Hooker who passed it to Gordon Lewis, his projects man, for his comments. On 27 July 1956 Hooker, Massey and others attended a meeting in Paris with Wibault, at which Hooker said that he was so convinced of the correctness of Wibault's proposals that he was having specifications and drawings produced on the design for a centrifugal compressor engine as proposed by Wibault, on condition that the subsequent development programme was conducted by Bristol.
    However, Lewis disagreed with the four centrifugal compressor scheme and favoured an axial Olympus compressor/fan, with its own intake, driven by the Orion via a gearbox and discharging through just two nozzles, one each side. Hooker looked at Lewis’s scheme and told him to go to see Wibault. Lewis found Wibault friendly and helpful, and he quickly produced a sketch of the Gyropter with Lewis’s proposal embodied.
    A copy of Wibault's March proposal had gone to Winthrop Rockefeller who asked Professor John Markham of the Massachusetts Institute of Technology to examine it. On 9 August Hooker and others met Markham in Paris and explained that Bristol now wished to take the route proposed by Lewis. When he was told of this, Wibault’s reaction was that, while he still thought his layout was more efficient, he felt sure that an association with Bristol was the best possible solution for common benefit.  
    Things moved quickly. Towards the end of September Hooker and John Innes of the Business department went to talk terms with Wibault and they also discussed the prospects of external funding for the work Bristol was to undertake. MWDA was thought to be one of the possibilities but there were others. After some discussion it was agreed that Bristol should prepare a patent specification. This was done by Robert Jaggard, the company's patents administrator, and Lewis, and was filed on 29 January 1957 in the names of Michel Wibault and Gordon Lewis. At Jaggard’s insistence a second pair of nozzles was added at the end of the jet pipe.
    The Project team in Bristol at that time, under Neville Quinn, consisted of Gordon Lewis, Basil Blackwell, Freddie Pitts, Pierre Young, and Charles Marchant. Neville Quinn played a vital role in persuading the others that this was a good project, and in persuading Lewis that he should pursue it. It soon resulted in project BE48, complete with gearbox. But thinking moved on. More engineers, such as Ralph Denning, Arthur Sotheran, Darrell Williams and Mike Williams joined the effort. The BE48 was drawn on 26 August 1956, three weeks after Lewis's first proposal, but it was soon realised that the Olympus fan would be better if driven by its own power turbine. This could not be done if the Orion was retained.
    The Orpheus was seen as a suitable replacement, not least because it had a large diameter shaft through which the shaft of a new turbine, to drive the Olympus fan, could pass. The resulting engine, designed under the leadership of Charles Marchant, was called the BE52 with the Olympus fan as the low pressure system and the Orpheus as the high pressure system. The gearbox was now not needed and much weight was saved. The first design scheme was drawn up on 17 December 1956.
    An important matter was to define the performance of the engine well enough to tell potential airframe companies what was being proposed. An Advanced Performance Folder (APF) was prepared for the BE52. Several copies went out, to Wibault who was undertaking discussions with various French airframe companies, and among British companies to Short Brothers, who at the time were developing the SC1, and were seen as experts in jet VTOL. However, Shorts used a meeting with the MWDA to argue that vectored thrust was a bad idea and that money should instead be put into jet lift!!
    The BE52 design study was soon superseded, in February 1957, by the BE53. Among many changes, it incorporated an increase in mass flow but more importantly it provided for the fan to supercharge the high pressure core of the engine. A single air intake was proposed. This was now the basic engine layout upon which the Pegasus was founded. A new performance statement was produced in March 1957, and a Project Study in June. These were circulated in the industry, in this country (although almost certainly not to Shorts) and in France and America. A copy of the new APF is thought to have gone to Hawker's head office but it did not filter down to Kingston. However, the Project Study (PS17) did reach Kingston, as a direct result of Sir Sydney Camm asking Stanley Hooker what he was doing about VTOL. When he did so, he observed that he was not impressed by the inefficiency of Rolls-Royce's proposals for lift jets.
    Hooker sent a copy of the Project Study to Camm, and it was his covering letter that included the memorable statement that "I should need a lot of convincing that there is any advantage in giving the take-off and landing engines a free ride round the countryside." It was the receipt and analysis of PS17 that caused Ralph Hooper to go down to Bristol to talk to Gordon Lewis. July 26 1957 was an important date, for it marked the true start of the remarkable and wholly constructive relationship between Gordon Lewis and Ralph Hooper. At the time Hooper had produced a proposal with a three-nozzle version of the BE52, complete with aerodynamic balances on the two front nozzles.
    One of the matters that Hooper was keen to raise was the hot exhaust, which he understood was still proposed only as a single cascaded nozzle. He wanted to propose that the hot exhaust should be split, and that it, and its nozzles, be placed much further forward. This was both a problem and an opportunity for Lewis who knew that the engine layout proposed in the Project Study relied upon the lever-arm effect of the hot exhaust to balance the fan discharge which would be lost if the hot nozzle was brought forward. He was also concerned that having the nozzles too close to the turbines could cause vibration problems upstream, and events proved him right on this. He was still reluctant to propose changes from the Olympus and Orpheus components, as a means of containing cost.
    But here was a potential, respected and serious customer who wanted something different. Hawker was seen as markedly different from Shorts, who had been treacherous, and it is unlikely that Bristol knew much about the various paper studies being undertaken by French companies. Hawker was seen as very real, and of course there had been a good relationship between Hawker and Bristol for very many years. As a result of this first discussion the engine was redesigned to bring the rear nozzles forward, and place them at the end of a very short jet pipe, alongside the fuselage. This could only be done if the hot thrust could be increased to more or less the level of the cold thrust, because the net vertical thrust of the whole engine still had to pass as closely as possible through the aircraft's centre of gravity.  
    Gordon and Pierre Young had already realised that the hot thrust could be increased by sending fan air into the core, thus supercharging it. This was a crucial step in the evolution of the engine, and to do this they had to get away from using existing parts. It gave them the chance to make the Olympus fan in mirror-image, to rotate anti-clockwise when seen from the front, and thus incorporate contra-rotation. This was not a new idea, and it is true that Ralph Hooper raised the matter with Gordon Lewis. Once Gordon realised that the engine was going to have to be redesigned, and that the presence of Hawker as a potential customer was a good reason for committing that expenditure, the decision was far easier than if it had been just a paper project. This permutation was called the BE53/2 and in its first incarnation was eventually to be called the Pegasus 1. Any design that preceded it was not a Pegasus. With this new configuration a decision was made to manufacture two engines in No. 4 Shop.
    In summary, the evolution of the engine can be seen to have taken four steps from Michel Wibault's Gyropter proposal:
The BE48 replaced the centrifugal compressors with the axial Olympus l.p. compressor, using it as a fan;
The BE52 replaced the Orion and its gearbox with the Orpheus, but retained the separate intakes for the core engine;
The BE53 did away with the separate intake and used the fan to supercharge the core, giving more power;
The BE53/2, the first Pegasus, introduced contra-rotation and confirmed the use of four nozzles rather than three.
    All of the discussion between Bristol and Hawker was characterised by a complete absence of not-invented-here problems. In this sense the Pegasus, in its evolution, was very fortunate. It is not a characteristic that has enhanced all engine programmes. By this time, Michel Wibault had little involvement in the evolution of the design. He was still retained as a consultant by Bristol, and as he once declared in one of his letters to Rockefeller, he was better equipped to pursue airframe companies. This he did, particularly in France, educating as many as possible in the virtues of vectored thrust. George went on to cover more of the early history of the Pegasus but space does not allow it to be included and this is as good a place as any to stop. If you want the full story, buy George’s splendid book reviewed in Newsletter No.25; highly recommended.
    The vote of thanks was given by the editor who thanked George for his superbly researched work.