AUTOGRAPHS, LETTERS & MANUSCRIPTS
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7.4.22
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LOT 928:

WHITTLE FRANK: (1907-1996) English Air Commodore, inventor and engineer, credited with the invention

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WHITTLE FRANK: (1907-1996) English Air Commodore, inventor and engineer, credited with the invention

'One.....matter which I think needs urgent consideration now
is how this development is going to be affected
if the enemy makes strong air attacks on this Country'

 

WHITTLE FRANK: (1907-1996) English Air Commodore, inventor and engineer, credited with the invention of the turbojet engine which culminated in the first British jet-engined aircraft, the Gloster E.28/39, flying on 15th May 1941. An historically important T.L.S., F Whittle, two pages, 4to, Ladywood Works, Lutterworth, Rugby, 18th May 1940, to Air Vice Marshal Arthur W. Tedder. Whittle writes to Tedder following a talk they had together on 10th May, and forwards two memoranda which he hopes will be of interest, continuing ‘That talk did me a lot of good, and had a very beneficial effect on my peace of mind. I did not mean to say by that that I like the arrangements which the Air Ministry have made any better than I did, but I hope that we shall be able to overcome the main potential sources of trouble by making special arrangements to deal with them’, adding that relationships with the Rover Company are as good as he could hope them to be (‘the engineers concerned will have to do the best they can to keep the atmosphere sweet’), expressing his desire to meet Tedder again so that he can explain some difficulties to be guarded against, remarking ‘An example of the sort of thing which causes me a lot of worry is the very serious delay which has occurred with the experimental apparatus for a pressure combustion test set. In this matter we came to the conclusion that such a set was urgently necessary early in February…..and in the meantime we got on with the W.X. idea. We came to the conclusion early in March that the W.X. scheme was the best all-round one for the purpose…..we sent the W.X. layout drawing to the B[ritish] T[homson-] H[ouston] on the 18th April, since when nothing has been settled. I took the law into my own hands two days ago and gave the B.T.H. instructions to proceed on the W.X. scheme, saying at the same time that it was probable that so much experimental work on combustion was contemplated that if they had a suitable motor driven compressor scheme it would be required as well’. In concluding Whittle conveys another concern to Tedder, ‘One quite different matter which I think needs urgent consideration now is how this development is going to be affected if the enemy makes strong air attacks on this Country. It seems to me that if Sheffield were intensively bombed we should be indefinitely held up, as the production of the special steel forgings is the main bottle neck of the job. I do not think it is wild to suggest that the removal of the whole of this development work to the other side of the Atlantic should be contemplated’. Accompanied by the two memoranda prepared and forwarded by Whittle, the first a typed D.S., F Whittle S/L, six pages, folio, n.p. (Lutterworth, Rugby), 22nd April 1940, titled General Memorandum on the Design and Production of Gyrone Engines and providing a brief outline of the design requirements, summarised by Whittle under various headed paragraphs including Performance, Minimum weight, Simplicity in starting and control, Mechanical reliability, Ease of maintenance, Suitability for quantity production and Cheapness of manufacture, in part, ‘The purpose of the engine is to give aircraft the maximum possible performance for their particular duty, i.e. for an interceptor fighter, high rate of climb, high maximum speed, etc, and for a bomber, high speed and load carrying capacity with long range…..The overall efficiency of the engine is extremely sensitive to the efficiencies of the components…..The overall efficiency depends on the thermal efficiency and the propulsive efficiency…..a higher positive-negative work ratio will lead to greater thermal efficiency, but also a higher jet speed, and hence a reduction in propulsive efficiency. In any case a balance has to be struck between the requirement for a high compression ratio and for a high positive-negative work ratio, and higher mass throughput, in order that the stress and temperature imposed on the turbine will be within the capacity of the material employed to withstand them…..the efficiencies of the compressor and turbine are so important that they must not be penalised except in the most minor way by other requirements….For example, it may be said that methods for producing the turbine blades should be adapted to the design requirements, rather than that the design should conform to available standard methods of production…..The all-up weight of the engine is very important….and….certain extra manufacturing processes are often worth while in order to obtain weight reduction. What may be a ‘commercial job’ for normal purposes is not necessarily a commercial job for flight purposes if weight reduction has been subordinated to ease of manufacture to an extent which penalises the aircraft performance…..The Gyrone engine is at present primarily intended for interceptor fighters, and hence the starting arrangements must be such that the time to get off the ground must be an absolute minimum. This requires that starting arrangements should be speedy, and also that the design of the engine should be such that it is capable of being run up to full speed without danger of damage due to thermal expansions…..Control must be simple and reliable, and the engine must be quick in response……the Gyrone engine is mechanically so simple that there are very few parts to go wrong, and provided that all materials used are sound and not unduly overloaded, there should be little fear of mechanical breakdown…..It must be possible for all parts requiring inspection or replacement at intervals to be readily accessible…..the simplicity of the engine is such that maintenance should call for little more than the cleaning of filters…..the engine must be made as easy as possible to remove from the aeroplane, and should be easy to strip and re-assemble…..For aero engine purposes cheapness of manufacture necessarily gives precedence to many over-riding requirements, and in the case of the Gyrone engine the manufacture is basically so much more simple that it is of even less importance. In any case it is very dependent on the quantity turned out from a given set of tools’, and the second a typed D.S., F Whittle, four pages (thin carbon paper), folio, n.p. (Lutterworth, Rugby), 17th May 1940, titled Memorandum on the Design of Gyrone Engines, outlining the general nature of the design and development problems of Gyrones, in part, ‘The Gyrone engine is mechanically simple, but the design engineers require to have an extremely wide range of engineering knowledge and experience because the design covers an unusually large field of problems…..Both turbine and compressor theory overlaps so far into the field of aerodynamic knowledge that a sound grounding in aerodynamics is necessary to the Gyrone designer. This is particularly so as the utmost in the way of efficiency must be obtained, both from the air compressor and the turbine, and it is the writer’s experience that the commercial turbine world has been slow to make use of up-to-date aerodynamic theory, and when they do use it it is often to abuse it. Because of the relative ignorance of commercial designers a vicious circle has been operating in the history of the gas turbine…..the designer must….be familiar with the engine/aircraft combination, and must have in mind many factors of operation which are peculiar to the aeroplane, e, g. centrifugal forces and gyroscopic effects in turns, atmospheric conditions at different heights and in different parts of the world etc. It is here that the turbine designer finds himself on unfamiliar ground…..when he is faced with the problem of a turbine for aircraft purposes he finds himself in a completely strange world where his engine can be subjected to ‘tight’ turns of an order which may black out the pilot and cause appreciable gyroscopic effects etc. He would also find that the range of operating conditions is quite outside his experience, as for example the necessity to start up and get off the ground in less than two minutes……He will not realise the importance of it being possible for the pilot to produce a sudden extra burst of power when he finds himself undershooting the aerodrome, or when finding an enemy aircraft sitting on his tail…..It is of course obvious that these [design] stages overlap very considerably, and the fact that it is an aero engine has to be borne constantly in mind from the earliest moment. Also..manufacturing requirements must be kept constantly in mind throughout the design, though, as with all aero engines, manufacturing requirements must give way to the need for operational efficiency to a degree quite foreign to normal commercial work’. A fascinating and highly important set of documents outlining Whittle’s vision for a jet-engined aircraft, which would finally come to fruition almost exactly one year later. Some light overall age wear, a few minor rust stains to the upper left corners, and the second memorandum with some creasing and a few minor tears and small areas of paper loss. G to VG, 3

 

Arthur Tedder (1890-1967) 1st Baron Tedder. British Marshal of the Royal Air Force. At the outbreak of war in 1939, and at the time of the present letter, Tedder was posted to the newly created Ministry of Aircraft Production. Later he would serve as Air Commander-in-Chief Middle East Command 1941-43 and as Air Commander-in-Chief Mediterranean Allied Air Forces 1943-44. Immediately after World War II Tedder was Chief of the Air Staff 1946-50.

 

Whittle had the original idea for jet propulsion in 1928 and made it the subject of his thesis, while at RAF College Cranwell the same year. He was so certain of his calculations that in January 1930 he filed a patent for his turbo-jet engine idea (granted in October 1932). In 1939 the British Air Ministry placed a contract for the W.1 engine to be flight tested on the new Gloster E.28/39 aircraft. At this point Whittle realised that it would be some time before Rover could deliver an engine and, unwilling to wait, cobbled together an engine from spare parts, creating the W. 1X which ran for the first time in December 1940, the same month in which Whittle suffered a nervous breakdown and left work for a month. During taxiing tests on 7th April 1941, the W.1X non-airworthy engine powered the E.28/39 where it unofficially became the first British turbojet to be airborne, taking to the air for two or three short hops of several hundred yards at about six feet from the ground. The W.1 flew officially in the E.28/39 on 15th May 1941.

 

The present documents are of great importance in the history of aviation, the jet engine’s invention being one of the most important of the 20th century.

 

Provenance: Acquired by our vendor from John Wilson (Autographs) Ltd., Witney, Oxfordshire, on 24th June 1980. The documents have not been offered for sale or appeared at auction at any time since, until now.