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Aviation History
1956
1956 - 0676.PDF
676 FLIGHT Perhaps the most clearly defined stage in the evolution of a new aircraft is the moment when first metal is cut. This picture records this stage in the Vanguard's development—milting of the aircraft's integrally stiffened wing-skin. VICKERS VANGUARD . . . An assessment of the Vanguard's payload-range performancemay be gained from Fig. 1. This shows that the design maxi- mum payload of 21,000 lb can be carried over a stage lengthof 2,600 st m with reserves for one hour's holding and a 230 st m diversion. Equivalent still-air range without these fuel allow-ances is 3,150 st miles. Included in both these range figures is a 5 per cent route allowance and a 1,000 lb manoeuvre allowance.Fig. 2 represents the Vanguard's cruising performance—true TABLE III: SPECIMEN FLIGHT PLAN Ib Typical operating weight empty 74,300 Design maximum payload ... 21,000 Reserve fuel 5,700 Landing weight 101,000 Block fuel 27,840 Manoeuvre allowance ... 1,000 Take-off weight 129,840 Climb to 23,500ft Cruise at 23.500ft at 312 kt T.A.S. and 0.075 n.m./lb Climb to 25.500ft Cruise at 25300k at 314 kt T.A.S. and 0.0795 n.m./lb Climb to 27.000ft Cruise at 27,000ft at 321 In T.A.S. and 0.085 n.m./lb Five per cent fuel tolerance ... Block totals ... ' 393 Total block fuel .Block time.. Time (tnin) 35.5 100 7 106.5 7 137 393 39 Distance (n. m.) 130 525 28 556 27 734 2.000 2.000 (Ib) 3,000 7,000 480 7,000 400 8,640 27,840 27 8401b 6 hr 33 min Cruise altitude* assumed in 1. Stage-length, n.m. Cruise altitude, ft 500 27,500 1.000 26,000 to 28,000 S-A. conditions 1.500 24,500to 26.500 2,000 23,500 to 27,000 2.500 22.500 to 28,000 air speed (kt) plotted against nautical air miles per lb of fuel,for weights ranging from 90,000 lb to 140,000 lb and for altitudes of from 5,000ft to 30,000ft. Fig. 3 shows the aircraft's take-off field length plotted againsttake-off weight. This graph, which provides adjustment for temperature, is based on the ability of die aircraft to take-off to50ft, or stop within the length of the runway with engine failure at the critical point. It is in accordance with A.R.B. and C.A.A.requirements. Fig. 4 shows true landing distances from 50ft; under Britishrules this is 70 per cent of the landing field length, and 60 per cent under American rules. A summary of weights and performance is given in Table II. To enable operators to make a quick assessment of the Van-guard over their routes, Vickers have published a specimen flight plan (Table III). This assumes a stage-length of 2,300 st milesin I.S.A. en route conditions, in zero wind and employing the optimum-range technique. OPEN DAY AT N.P.L. 'T'HE work of the National Physical Laboratory at Teddington••• has always been of the greatest interest to engineers in general, and this year's "open day," on Friday last, provided once morea most instructive glimpse of this work—a glimpse which more than compensated for the fatigue of walking through the grounds.The main problem of the visitor, as every year, was in deciding which exhibits to choose from the 223 available. Among the aeronautical items, the development of high liftfor landing and take-off provided a glimpse into the future of the jet flap. It may be recalled that in this scheme, originally de-veloped at N.G.T.E., the efflux from a gas-turbine engine is ejected through a narrow slit extending along the wing trailing-edge or, as in the N.P.L. demonstration, along the knee of a small hinged flap. Without the hinged flap, the jet is inclinedat an angle to the flight path, and not only provides lift and propulsive force by direct jet reaction, but also generates in-creased lift in a rather similar manner to a large trailing-edge flap. The use of a small hinged flap to deflect the jet stream hasthe additional effect of retaining a smooth boundary-layer flow over the flap. As the velocity of the jet is increased, and theboundary layer becomes attached to the upper surface of the flap, the lift increases rapidly and thereafter a further increaseis obtained—rather more slowly—by supercirculation. The de- monstrations in one of the 9ft x 7ft tunnels showed the attach-ment of the boundary layer quite clearly. Experiments with boundary-layer control at the wing nose, combined with jet flapsat the trailing-edge, are also in progress. Further interest was created by the experiments and theoreticalprogramme investigating flow separation at high speed. In the 2.6inx 1.5 in supersonic tunnel, fundamental aspects of the type of separation which is provoked by shock waves are being studied.Recent work includes investigations of the effects of surface curvature, and of heat transfer to and from the surface. Atpresent a study of the factors determining the pressures on a blunt base in supersonic flow is also being made. Interferometry is utilized in N.P.L. experiments investigatingthe influence of leading-edge shape on the change in the type of separation occurring as Mach number is increased and asincidence is changed. The 9in x 3in tunnel, incorporating a Mach-Zehnder interferometer, is being used for this purpose. A high-speed extension of previous low-speed work, using oiland titanium oxide as a means of visualizing the surface flow on swept wings, has shown that the respective flow-patterns aresimilar. Experiments at high speed, and a film illustrating work in a water tunnel, showed that the "tip" vortex on a sweptwing at high incidence originates at some point on the leading edge, this point moving inboard as incidence and sweepbackare increased. This is caused by separation of the boundary layer at the nose of the wing, leading to a "rolling up" of theflow. This forms a vortex which extends outboard at an angle to the leading edge and thereafter forms the "tip" vortex. Measurement of oscillatory forces on finite aspect-ratio wingswith flaps has been made possible by equipment developed at N.P.L. At present this is installed in a 9.5in high-speed tunnel,and is being used in experimsnts on a half-delta wing with a full-span flap. With this apparatus it will be possible to measuredirectly all the forces relating to oscillation of the flap* about its hinge, and to the pitching oscillation of the wing about differentaxes. A Mach number range extending from subsonic to 1.8 with a maximum frequency of 100 c.p.s. is possible.
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