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Aviation History
1947
1947 - 1479.PDF
SEPTEMBER Fl/GHT X45- The Anglo -American Conference and the experimental resea*;h of Rodert and the N.A.C.A. Ames Labora- torv Group on heat de-icing, have estab- lished methods for aircraft ice prevention on a sound engineering footing. Require- ments for maintaining ice-free surfaces on wings, airscrews, -windshields, and carburettors are briefly discussed in the report, and the status of "the icing prob- lem for the turbine engine inlet is reviewed. Whereas it is now possible to design with reasonable assurance of successful operation ice-prevention equipment for specified icing conditions, it is not pos- sible to specify the icing conditions that may be encountered in •all-weather opera- tions over world-wide transport routes. Limited data obtained from recent flights ft) the United States relating to the water content and drop size in icing clouds are presented. Emphasis is placed on the necessity for the accumulation of statistical data in the characteristics of icing clouds, so that basic design condi- tions may be accurately specified. Controi in Low-speed Flight By M. B. Morgan, R.A.E. THE lecturer, confined himself tostability and control problems offlight at moderate speeds, uncom- plicated "by Mach number and distortion effects. He began by =>howi-ig how wing loadings have increased and power load- ings have decreased between 1930 and the present time, the former from 14 to 70 lb/sq ft and the latter from 16 to 10 lb/h.p. Concurrently the "classical" take-ofi distance from rest to 50 It has risen from 500 to 1,500 yards. Safety after engine-cutting had in- creased this distance. In 1940 it was 1,500 yards, but since then it had risen . to an average value of 2,700 yards. " We cannot go on in this way," Mr. Morgan ..said. "Closer attention to wing loading, • to aerofoil and flap design, and to critical engine -failure speed is obviously indi- cated." In connection with the engine-cut case, ' the lecturer pointed out that the average safety speed rose from 100 m.p.h. in 1939 to 135 m.p.h. ^in 1947. It would be FLAP TYPE 4Ci NAC A DOUBLE SLOTTED FOWLER BLACKBURN SLOTTED SPLIT FOWLER + SPLIT DOUBLE FOWLER DOUBLEFOWLER +WING SLAT 60% SPAN 1-11 115 1-32 1 32 1-54 2-35 2-61 42-7 2-65 282 2-B2 3-85 434 higher but for the very large fins and rudders, which had in some cases brought the safety speed down to stalling speed. But on some multi-engined transports these large fins and rudders were not used to the fall, sinoe safety speed was determined not by rudder power but by the force the pilot could exert at climb- ing speed. Reduction in safety speed had been achieved by power-boosting of the rudder control. Since increase in size slowed-up the response to control movement, it might have been feared that the very large air- craft now being built would call for drastic alteration in relative control areas. Recent response calculations, however, indicated that, surprisingly enough, none of the parameters which really matter +0 the pilot are so affected by sizes up to 500,000 lb as to make manoeuvres difficult. These parameters were : height of start at hold-off ; forward distance covered when shifting track sideways by S-turns; and time to raise a dropped wing. Turning to the subjects of the stall, maximum lift coefficients and control at high lift, Mr. Morgan examined methods •of increasing maximum lift coefficients. Unless wing loadings were stabilized it might become necessary to resort to de- vices more ambitious than those, now in use. Some of these are shown in the accompanying diagram. A "peak" is reached with full-span double Fowler flap and full-span leading-edge slot, the value of maximum lift coefficient being then 4.56. There were many practical ob- stacles in the way before such a figure could be achieved, notably lateral con- trol and longitudinal trim difficulties. The lecturer foresaw little difficulty iii providing adequate lateral control at a lift coefficient of 3.0 for heavily loaded aircraft. He favoured the backward- moving flap which, in the intermediate position, would also give improved take- off due to its high lift and low drag. Longitudinal stability was the handling problem which gave designers the most trouble. The lecturer pleaded for de- signing aircraft with the e.g. well for- waTd and placing the undercarriage accordingly. This was by far the most economical method of avoiding longi- tudinal stability trouble. It should be coupled with a tail somewhat larger than was really thought necessary. American de- signs showed tails some 2 s per cent larger than British, while working to about the same e.g.-aft limits, but to a much farther forward e.g.-for- ward limit. ACi 46* 46-2 504 49-8 630 100% SPAN 1-61 1-67 1 91 1 93 306 311 3-17 3-41 2 25 3-75 456 50-9 51-9 55-8 3-43 56-2 61-4 74-7 Advanced schemes for achieving high lift coeffi- cients, ^sowing-loading in Ibjsq ft to give stall- ing speed of 80 m.p.h. All flaps have a chord of 0.4 of the wing chord. Slat chord—0.31 wing chord. Ratiotarl arm: wing chord =1 Aspect ratio = 9. Tapemratio=2:I.CL wir>g = 1.5. Kxitiowmg thick- ness: wing chords 0.16. Mr. Morgan next <lealt with some of the difficulties encountered with tailless aircraft, particularly near the stall. Some of these might be overcome by what he termed "ersatz stability." Quite large yawing moments could be generated on an all-wing type of aircraft by applying drag at the wing tip—given by spoilers, double flaps, and so on. Sideslip could be measured by a wind-vane, rate of yaw by a spring-restrained gyro. It should be possible, he thought, to feed such measurements into a servo-mechanism, thus increasing sideslip and rate-of-yaw values until they equalled or even hand- somely exceeded those appropriate to conventional aircraft. This was not new.. During the war it was found that four- engined bombers could be flown more accurately if the aircraft were flown by the automatic pilot, the human pilot being given a small " stick " whereby he could manoeuvre the aircraft via the automatic pilot. Much further work was needed on the best method for bringing the pilot's con- trol into play while the automatic pilot was working continuously. Development was proceeding along three lines: (1) Using a common surface for the "ersatz'' stability mechanism and the pilot, so that when the pilot moves his stick, he merely feeds signals into the automatic pilot. (2) Splitting the control surface, coupling the pilot's stick directly to one half, the automatic pilot to the other. (3) Keeping the pilot's stick directly coupled to the controls, as on conven- tional aircraft, and making the auto- mafic pilot merely operate a tab on the control surface. Power-operation would provide consistently light stick forces. This might lead to the pilot overstrain- ing the machine, and it was vital that work -on the development of suitable " g-restrictors " should proceed in parallel with power-operation develop- ment. Mr. Morgan concluded his paper with an examination of gust-alleviation devices and stalling at high altitudes. Economics of Personal Aircraft By G rover AMONG the American pioneers ofaviation the name of GroverLoening stands high. He is now a member of the National Advisory Committee for Aeronautics. The first part of his paper deals with the produc- tion and use of privately-owned aircraft in America. In the banner year 1946 some 35,000 personal aircraft were de- livered in the U.S. Production in other countries may have brought that figure up to 40,000 private aircraft—less than one week's production of American auto- mobiles Mr. Loaning comes to the coaclusioB that the most serious obstacle to private flying, and one about which we must be particularly realistic, is that of cost. There is no denying the figures, nor is there any denying of the very evident fact—at ieast in the U.S.—that the high cost of operation, in relation to the results obtained, in the use of personal aircraft is to-day, by far, the roost serious obstacle in this picture. To attain a mass production market, the airplane must of course biend itself into the life of an individual the way the automobile did. An average American ust of an automobile will be aifoout 10,000
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