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Aviation History
1949
1949 - 0825.PDF
54° FLIGHT MAY 5TH, 1949 Lift and Drag gained by increasing the aspect ratio above 10, the optimum lift coefficient in this case being about 3.5. On the basis of these estimates, it appeared that a maximum lift coefficient of from 2.5 to 3.0 in the take-off condition was desirable on four-engined aircraft. The lecturer stressed that, witJi moderate power loadings, full advantage of high lift coefficients could be taken only if the drag on the climb was kept low by using high aspect ratios and high-lift devices which were inexpensive in drag. Turning to high-lift devices for swept-back wings, Air. Duddy observed that the increment in lift coefficient which could be obtained by a trailing-edge flap was reduced as the angle of sweep was increased until, at large angles of sweepback (e.g., 60 deg) there might be no increase in maximum lift. It had been suggested that for a given flap, the ratio of the increment in maximum lift coefficient with sweep to that without sweep was given approximately by :— AC, may _ 3 /JCL max at x - O where a = angle of sweepback. Tests with simple split flaps had shown that the stalling incidence was always reduced by at least two or three degrees when the flaps were deflected, and this partly explained the small increase in maximum lift coefficient. Some of this loss could be regained by moving the hinge point of the split flap back to the trailing edge. With large angles of sweep (42 deg and 60 deg) the increase amounted to about 50 per cent. In one particular case, with a flap chord of 0.184 c extending half the span of a wing with 42 deg sweepback, the increment in maximum lift coefficient due to the flap was increased from 0.2 to 0.3 by moving the flap hinge point from 0.816 c to i.oe. This suggested that the best type of slotted flap for a swept wing would probably be a Fowler, which also included a large amount of rearward extension. Probably the most troublesome characteristic of the swept-back wing was the stalling of the tip sections at a considerably lower incidence than the root sections. This caused serious longitudinal stability problems; it also caused large reductions in maximum lift. Leading-edge slats were effective in delaying this stall and there was a resulting increase in maximum lift coefficient. Mr. Duddy suggested that, as an alternative to a leading-edge slat, the leading-edge flap appeared to be equally effective, both in delaying the stall and in increasing the maximum lift. To obtain appreciable increases in CL max by a slat on an unswept wing, it was necessary to make the slat cover the entire wing span, but with a 40 deg swept wing, a 50 per cent-span leading-edge flap (or slat) could increase the stalling incidence by five or six degrees, causing a corre- sponding increase in CL max. With a swept-back wing, sonuTslight relief on the pitching moments due to a flap could be obtained by limiting the span of the flap approximately to half that of the wing. By concentrating the flap oa the inboard half of the wing, the centre of pressure of the increased loading due to the flap was kept farther forward relative to the aircraft's centre of gravity than was possible on an unswept wing. With 40 deg sweepback and an aspect ratio of 3.5, the increment in pitching moment due to the flap would be 60 to 70 per cent of the value for an unswept wing, provided that the flap was only half span. If the flap was full span, the increment would probably be about the same as that obtained on a wing without .sweepback. R.Ae.S. MEDALS and AWARDS BEFORE Dr. Hugh L. Dryden's delivery of theWilbur Wright Lecture to the Royal Aero- nautical Society iast Thursday, the customarydistribution of medals and prizes—made each year an the occasion of the Wilbur Wright Lecture—took place, and the list of recipients is given tielow. A summary of the lecture-itself appeared in last week's issue of Flight. *._ MEDALSBritish Gold Medal for Practical Achievement in Aeronautics (tor outstanding practical achievementleading to advancement in aeronautics).—Mr. S. Camm, director and chiet designer, Hawker Aircraft,Ltd., "for his outstanding work in the design and development of fighter aircraft.British Silver Medal for Practical Achievement in Aeronautics (for practical achievement leading toadvancement in aeronautics).—Lt. Cdr. (A) E. M. li'.mra, K.N., for his outstanding achievements inadvancing the technique of deck-landing. . Society's Bronze Medal (lor work leading to anadvance in aeronautics).—Capt. R. N. Liptrot for his work on helicopters.Wakefield Gold Medal (awarded to the designer or inventor of any apparatus tending towards safety inflying),—Mr, E. S. Calvwt ivt his work in the develop intnt of airport lighting.George Taylor (of Australia) Gold Medal (for the most valuable, paper read during the previous session).—Mr. G. R. Edwards, chief designer, Vickers Arm- strongs, Ltd., W'eybridge. Works, for his paper on" Problems in the Development of a New Aeroplane." PRIZES Edward Busk Memorial Prize (for the most valuablepaper on applied aerodynamics).—Mr. VV. Stewart for his paper on the "Flight Testing of Helicopters."Herbert Ackroyd Stuart Memorial Prize (for the most valuable paper on applied thermodynamics).—Mr.W. H. Lindsey for his paper on " Development of the Armstrong Siddeley Alamba Engine."Usborne Prize (for the best contribution to the Society's publications written by a graduate or studenton some subject of a technical nature in connection with aeronautics).—Mr. D. R. Maguire for his paper on " EnemyJet History." R. P. Alston Memorial Prize (for practical achievement associatedwith the flight-testing of aircraft).—Mr. B. A. G. Mcgowan for his work in the flight-testing of gliders.Baden-Powell Memorial Prize (awarded to the best entrant in Medallist, Mr. Sydney Camm Dr. Rcxbee Cox presents the silver medal to Lt. Cdr. E. M. Brown, R.N. (top le t): and the bronze medal to Capt. R. N. Liptrot (bottom right). Dr. Hugh Dryden (bottom left) is seen delivering his lecture. ii the R.Ae.S. Associate Fellowship lixamination).—Mr. R. J. Starling. HONORARY FELLOWSHIPSIt was announced during the course of the evening that honorary fellowships had been conferred upon Sir Frederick Handley Pageand Lord Brabazon of Tara. D 16
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