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Aviation History
1941
1941 - 1842.PDF
FLIGHT AUGUST 14TH, 1941. EVOLUTION OF THE VARIABLE PITCH AIRSCREW ;pgmg®aj£?i>s~' A British Invention in the Development of Which Dr. Hele-Shaw, Mr. T. E. Beacham and Mr. H. L Milner Played Major Roles By G. GEOFFREY SMITH FEW people realise to what extent aero-engine designand aircraft performance have been affected by theform of airscrew available. At one ^period not so many years ago engine and aircraft design had definitelyoutstripped airscrew progress ; it is not going too far to say that aircraft and aero-engine performance would have ad-vanced more rapidly if a free choice of suitable propellers had existed. For many years extending even prior tothe Great War of 1914-18 designers had plotted, discussed and examined the possibilities of the variable pitch air-screw mainly to increase engine speed during the take-off. Fixed pitch airscrews cannot possibly give the best results under all flying conditions, and with the advent of super-charged engines it became obvious that a variable pitch airscrew was indispensable if full advantage was to be takenof such a unit. But it cannot be said that this check upon progress was due to lack of foresight of aircraft designersbut rather to the tardy acceptance of a principle which was evolved by three British scientists nearly twenty years-ago, the late Dr. H. S. Hele-Shaw and Mr. T. E. Beacham (the patentees) and Mr. H. L. Milner who developed thedesign. It is interesting to trace the evolution of the variablepitch airscrew as we now know it, since the critical reception accorded to the original design has its counterpart in manyother spheres of engineering progress, and a chronicle ol the facts may serve as encouragement to those who to-dayare busily evolving progressive schemes which may, and probably will, encounter setbacks before general accept-ance. The way of the pioneer is indeed hard! It was in the Midlands recently, while inspecting fourblade and contra-rotating Rotol airscrews, that the writer encountered Mr. H. L. Milner and discussed with him theearliest days of the hydraulic variable pitch airscrew in common use to-day. He told me that before the GreatWar of 1914 the late Professor Petavel arranged that an aero-engine should be sent to Manchester University, wherehe was a student under the Professor, in order that they should carry out aero-engine research. V-s. •>£:.. Early Research Full consideration of this proposal, however, revealedunexpected difficulties, and it was finally decided that Mr. Milner should go to the R.A.E. at Farnborough, wheremaintenance and other facilities for research existed. In this way he came in contact with, and began to take aninterest in, aeronautical problems. Even in those early days the desirability from an all-round utility standpoint of avariable pitch airscrew was recognised and discussed, although it was difficult to present a convincing case forvariable pitch at the time, since the speed range of existing types of aircraft was so low, and, in any event, even theweight of a fixed pitch airscrew was a burden which would have been discarded if such a course had been possible.Nevertheless, the problem of varying the pitch of an air- screw continued to receive attention on account of the (Left) Mr. H. L. Milner, Wh.Sc. (Heading photograph) The Hele-Shaw-Beacham airscrew of1928, now preserved as a museum piece.
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