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Aviation History
1939
1939 - 0744.PDF
262 FLIGHT. MARCH 16, 1939 T H E O U TLOOK outside his province to say anything about aeroplanes for the Army. None the less, the Army cannot fight without aircraft. We may, we hope, take it for granted that in due course an army co-operation squadron or more will be pro vided for each division of the expeditionary force of the Army. The Air Estimates give no information on that subject because the squadrons allotted for reconnaissance for the Army do not figure as a separate entity, as the Fleet Air Arm has always done, but are buried, most confusingly, in the misleading term "Metropolitan Air Force." As we have remarked many times in the past, these squadrons add nothing to the air defence of the Metropolis or of any other part of the homeland, as they must go overseas when the Army leaves the coun try. Still, we may take it that the nineteen divisions will receive the approved number of reconnaissance squadrons sooner or later. Reconnaissance Not Enough T O provide aircraft which san reconnoitre and spot for the guns is not enough. As Group Capt. A. J. Capel pointed out in his lecture to the Royal United Service Institution last month, the expeditionary force must have bombers to carry out long or strategic reconnaissance, as well as fighters to defend the close- reconnaissance machines, and he gave it as his opinion that without that complement the Army would be un able to proceed overseas. We have not the slightest doubt that on that point Group Capt. Capel was quite right. Now, if our Army were intended only to take part in the defence of our shores, it might be easy enough to find the necessary bombers and fighters without seriously crippling the defensive and counter-offensive policy of the Air Force. Even if the expeditionary force were to consist of only six regular divisions, the diffi culties of providing them with enough aircraft might, with an effort, be overcome—even though that effort entailed departmental wrangling and perhaps increased danger to London. But to equip nineteen divisions with reconnaissance machines, bombers and fighters, all in adequate numbers, is a task of considerable dimensions, and we should very much like to know that this matter is being tackled with energy. Perhaps some Member of Parliament will question the Government on the subject. Sitting on the Slipstream L AST August Flight described and commented on the j Crouch-Bolas system of getting extra lift, better take-off and slower landings by making use of the airscrew slipsteam. We pointed out that these advan tages could be obtained without any material sacrifices in cruising speed. In the meantime Mr. Harold Bolas (who has now returned to this country) and Capt. Goodman Crouch have not been idle, and some interesting developments may be expected in the near future. And now comes, from France, a very startling confirmation of the Crouch-Bolas theories. A Yugoslav engineer, working at the St. Cyr Institute under M. Toussaint, has carried out extensive wind-tunnel tests from which it appears that not only should it be possible, as the two British inventors claim, to improve take-off and landing, but to take off en hclimpterc, hover, and kind at no forward speed! The researches undertaken at St. Cyr by M. Svetopolk (CONTINUED) Pivko were very thorough, as will be gathered from the fact that 3,912 tests were run, with 652 different relative positions and angles of airscrews and wing. A full account of the results are published in the " Scientific and Technical Publications '' of the French Air Ministry. and a summary is given in a recent issue of our French contemporary, Lea Ailes. Like Messrs. Crouch and Bolas, M. Pivko has found that the negative inclination of the airscrews is important. Furthermore, he has determined that the best position of the airscrews is some distance ahead of the leading edge of the wing, and •about one-quarter of the airscrew diameter above the leading edge. As was to be ex pected, the effect is most marked when the airscrews are of as large diameter as possible, and of small pitch. However, it is not, apparently, necessary for the air screws to "cover" the entire wing span in order to get really remarkable results. For minimum drag it was found best to have the airscrews fairly close to the leading edge. Rolling tests indicated that airscrews rotating in opposite directions might be essential for stabilit ' and controllability. Practical Application I N view of the work being done in this country by Crouch and Bolas, it is of interest to note that as a result of the French experiments it is estimated that even the orthodox type of aircraft could benefit materially from the tilted airscrews. Thus without any other change than the angle and position of the thrust lines of the Potez-63, a military aeroplane of 8,000 lb. gross weight and 1,300 h.p., the take-off run would be reduced by 10 per cent. Out of curiosity M. Pivko has calculated that if the Potez-63 were fitted with airscrews of 13ft. 9m. dia meter it would be able to ascend vertically (without take-off run) at 3.6 ft. per sec. In practice the under carriage and tail-wheel would, of course, have to be modified for the greater energy which might have to be absorbed if the pilot did not make quite a perfect landing. The French research work has gone even farther than this and has examined the results theoretically obtainable with an aircraft specially designed. Such an aeroplane would be of perfectly normal appearance, and in high speed flight would not differ from the orthodox. It would have two extra controls: one for changing the angle of engines and/or airscrew shafts, and one for certain control surfaces on the wing, in the slipstream behind the engines. Given these extras, and the larger airscrews capable of being set to a very fine pitch, it has been calculated that a machine, the sketch design of which has been got out, weighing 3,200 lb. and equipped with two engines, running in opposite directions, of 300 h.p. each, could rise vertically, hover, fly extremely slowly or up to 180 m.p.h., and land vertically. By "going the whole hog" in this way, helicopter performances seem to be possible. The obvious snag is that if one engine stops, or even falters, while the machine is close to the ground, serious trouble might result, as the lift and controllability are so absolutely dependent upon the slipstreams. Nevertheless, the idea does appear to call for extensive research in this country. And anyway, as two Englishmen invented the idea, we cannot in all decency ignore its development. DIARY OP FORTHCOMING EVENTS—Page 267
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