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Aviation History
1943
1943 - 1995.PDF
AUGUST T2TH, I943 FLIGHT 169 fteflections The Work of the Rotol Test Department , O By BRYAN GREENSTED (Chief Test Pilot) F-& MR. GREENSTED has been responsible for the fight-testing of Rotol airscrews since the company first decided to establish such a department. That his work has played an important part in the remarkable development which lies between the ipiing of 1939 and the present time goes without saying. His whimsical review of that four-year period is written in a style which will appeal greatly to readers. WrHEN seated in a comfortable chair in a well-heatedoffice, and armed with the knowledge that not onlyare all the aircraft unserviceable but the Cotswoldsare covered with impenetrable fog, I am not averse to quiet reflection. In fact, I am definitely given to it. My reflections range from beer to Barracudas, income tax, fillet steak (with French fried and mushrooms, of course), and to places away beyond the hills of Idaho. It is not altogether surprising, therefore, that I should occa- sionally review, mentally and at my leisure, the work of the Rotol Flight Test De,gartment since it \ was formed in May, 1939. As I sit here reflecting like anything, what strikes me most is that we seem just at this moment to have arrived at a milestone in the development-flying of airscrews. Milestone is, perhaps, not a very fortunate choice of word, since even the most prejudiced have not yet got around to describing the contra-rotating airscrew as a piece of masonry. However, let me explain. When the Department flew its first aircraft for the first tiiae, that aircraft was a Gloster Gauntlet fitted with a three-bladed adjustable-pitch metal airscrew. Since that d3f Tve have been through the whole range of airscrews— from two hl&aes to as many as we can put into a single hub, constant-speed and feathering—and we are now flying the six-blade contra-rotating, constant-speed airscrew for engines of over 2,000 h.p. It appears, then, that although the airscrew is now "split into two counter-rotating halves, and its speed is governed by a constant-speed unit, we are back at the beginning again with two three-blade airscrews instead of one, and are being confronted with all the problems of efficient contra-rotation. Sticky Flying The adjustable-pitch airscrews on the Gauntlet were used for paint adhesion tests; it took no more active part in our saga of airscrew development than that. The tests, how- ever, resulted in a drastic re-orientation of our carefully matured attitudes towards flying in bad weather since one of the requirements was that the flying should be carried out under the most adverse flying conditions possible in order to subject the blades to a very severe test. Altogether,! with various airscrews and various tests, we flew about 300 hours in rain, hail, snow and sleet. The replacing of the Gauntlet by a Gladiator set an interesting and, so tar, insoluble problem. Would you rather be wet over a large area by a spray of constant density, or wet °y« a small area (eye, left foot, ear, etc.), by one of those high velocity, high-capacity jets which seem always to fipdP' their way through the cracks between hood -and wind- screen? (if I appear to digress, you must remember I am reflecting, and that we may at any moment talk about the hills of Idaho aforementioned.) t The flying development of the various constant-speed The author and one of his " milestones "—the four-blader. airscrews has been continuous and progressive, with the exception of the two-bladed C.S. feathering type, which was flown after the four-blader. As they are naturally intended only for comparatively small engine powers and therefore presented undei test none of the operational diffi- culties of modern Service types, the continuity of testing of the larger sizes was not affected; and each type, w^filst presenting its own peculiar problems, has added to that store of knowledge which has been applied to the next stage of development. At the same time as these basic types of bomber and fighter airscrews weie undergoing vigorous endurance, per- formance and operating tests, all sorts of special investi- gations were being carried out. These included such items as hydraulic pitcti locks; devices to prevent over-speeding ; suitability and simplification of controls; de-icing and a hundred-and-one other refinements which are still officially "off the record." Nor must I forget all the intensive development carried out with our electricyairscrews, which series of tests formed a programme of tireir own. In fact, when I review them all, and remember also that we have flown approximately 5,000 hours since the beginning of the war, I begin to feel that, though I sit in a comfortable chair at this moment, there must have been times when we have been fairly busy. , The New Phase It is therefore all the more pleasant to feel that we have now started a new (and more complicated ?) phase of air- screw development: flying with an airscrew which contri- butes largely to the ease and comfort of the pilot. I have always resented the necessity of preventing those violent swings- which are associated with the throttle movements of our hitherto conventional engines—swings which threaten to convert a correctly exe/zuted turn into a sideslip, merely because the pilot wishes to throttle back during his circuit. I also resent the efforts of high powered aircraft to make sudden dashes off the runway during the take off. They have caused me many anxious moments. Nor do I like the feeling of putting one wing down during the take-off, particularly when this attitude is associated with a strong adverse cross-wind and a narrow-track undercarriage. Again, during the take-off, I object to the feeling of the aircraft skating along on the outside edge of one tyre. (You haven't considered that the cancellation of torque equalises the load on the tyre, thereby reducing the wear, have you ? Don't tell the salvage authorities.) The contra rotating airscrew, therefore, finds me a very willing admirer. If we could go back again to May, 1939, armed with our present knowledge of the behaviour of the [Continued at foot of next page)
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