Gliding 1950 - Lakes Gliding Club

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CORACYPS SCALE: ~ FI.ILL. S'ZE ....----------- 1:#"'----------1 ~. C.65H. - I Fie;. 4 general arrangement of the aircraft under consideration in this paper. The bird is commonly called a black buzzard or scientifically Coragyl'S atralt's. He is an excellent S03lrer, though not .as goud as the turkey buzzard (Catha/us aura). However, the Coragyps happened to b~ quite plentiful in the autumn skies during the time the research was" made. Fortunately, Coragyps is also 30% heavier in wing loading than the Cathartes. He is therefore easier to track with the sail'plane used for this research. Since the sailpl'ane had a wing loading ne.ady 2.5 times that of Coragyps, he had a distinct advantage in manoeuvrability over the sailplane. Because of this any evasive tactics of the bird were completely SllI;1CesSful İn Fig. 5 are shown the measurements obtained by means of the sailplane tracking a numbet ofdifferent black buaard~. There may have been variations between one bird and the next but in these results the data are treated as· a statistical average representation of the birel's aerodynamics. The wing loading and aspect ratio shown are also averages obtained by numerous bird weighing 2.3 kilograms. This value corresponds to a power loading of 122 kilograms per horsepower. The lowest ornithologists. The captured bird technique may be an improvement in this re~peet, since the specimen (flight test article) can. be weighed at take-off and also measured for its geometry. inspection of Fig. 5 shows that there are two distinct speed polars for the bird's two phases, soaring and gliding. The vertical velocity curve for the soaring phase appears quite similar to that of conventional sailplane.s. However, the gliding phase- curve has a much flatter polar. This is particularly evident if one views the gliding ratio curves. 1n sailplane terminology the bird wouid be said to possess a good speed range when gliding. There 3re a number of other points whi,ch merit emphasjs-the very low minimum sinking speed of the bird in soaring flight and the very low speed at which he can fl,y. If one computes the power required for the bird to sustain level flight at a speed of] 3.8 metres per second cn~ finds the" phenomer. ally low value of ().019 horsepower for a -148-
I I I I - I VUDClrY PIJLAItt· CMMYP$ -/,$- r- W'HVCJ LOAZN/IHJ &.3 1(c/H£T£Ra I~ Cl -I.Z;) A;S~~CT RATIO 5.7 I .~ \ r\ ~ - ~.. / )( u • I ~~ ( ~ .. I ~. l( I.D~ t I 14.8 I ~ ~ , "> "~ I~~ I~J ~ ~ '0111) c? \I)~ ~ ~V i- L ~ 7 ~ /'" r%~_ Z2 t!tI ~£JIO 18 II- ~If' ~.2 If FIG. 5 4- • III I~ If- I~ 18 2.0 1.2 2+ 11. I~ soaring speed, 8.5 metres per second, was determined by timing the bird around a complete circle and measuring the diameter of the circle in terms ,of the known wing span of the bird. The lift coefficient ,at this speed is 1.57, a relatively large value con~dering the Reynold's number at which this lift ~urs, namely 140,000. If the same data shown in Fig. 5 are plotted in terms of the non-dimensional coefficients of lift and drag, there results the so-called drag polar Fig. 6. In this polar the lift coefficient is plotted as the square so that th:: drag polar, normally a parabola, is linearized. 'The reason for the bird's closing his tip feathers for gliding flight is immediately apparent from this plot. He does this to leduce his drag. With slots open he could not attain a lower drag coefficient than 0.019, but with the slots closed he can reach a minimum of 0.0058 in drag coefficient. It is also clear that the dosing of the tip slots reduces the effective aspect ratio. At high speeds (Iow lift coefficients) the bird already has a ver) low mduced drag and strives rather to reduo: his parasite drag. Actual measurements of the induced drag and consequently the effective aspect ratio can best be done at lift coefficients much higher than those measured here. There is still left to be investigated the region 0.7
Page 2 and 3: GLIDING Edited by Alan E. Slater. M
Page 4 and 5: Here and There American Contest The
Page 6 and 7: National Gliding Contests, 1950 HIS
Page 8 and 9: 25th July 26th July. Goal Race to B
Page 10 and 11: Half-Way to Edinburgh by DonaJd Bro
Page 12 and 13: Captain Cook's Monument, went on to
Page 14 and 15: To and from Ingoldmells by Donald B
Page 16 and 17: ~T'HIS was a very surprising flight
Page 18 and 19: Retrieves-Various by K. E. Machin o
Page 20 and 21: From Wave to Wave Across Country by
Page 22 and 23: Lessons of the 1950 Contests N the
Page 24 and 25: Exploiting the Cuniu1 for Speed and
Page 26 and 27: ELLIOTTSOFNEWBURYLTD J A L B E R TW
Page 28 and 29: I stuck it out to 21,500 ft. indica
Page 30 and 31: Courses for Dartmouth Cadets F OR t
Page 32 and 33: '(.6 I I I I I SP~~D PoL.A.1f OF SA
Page 36 and 37: energy f!"Om the wing tip vortex. T
Page 38 and 39: CLUB NEWS Bristol Gliding Club been
Page 40 and 41: Ljmon-on-Ouse Gliding Club T the be
Page 42 and 43: currents over the sea w.as terminat
Page 44 and 45: flight, while Nick, although he had
Page 46 and 47: Aerial view from above Southdown Cl
Page 48 and 49: the Long Mynd, 40 hours were flown,
Page 50 and 51: ?00 the jungle drums sound 011 key
Page 52: ON SIITE REPAIR AND OVERHAUL SERVIC

Gliding 1950 - Lakes Gliding Club

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