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Aviation History
1952
1952 - 0651.PDF
FLIGHT, 14 March 1952 Martin PB5M-1 Martin, with water flaps (under-water rudders). These combine the functions of water brakes and water rudder. Consolidated-Vultee XP5V-1, turboprop-powered, reconnaissance and transport flying-boat. A number will be supplied to the US. Navy. THE FUTURE OF THE FLYING-BOAT The Bleriot Lecture: Saunders-Roe Chief Designer Foresees Far-reaching Advances PARIS, which alternates with London as the venue for the Louis Bleriot Lecture, seemed certain to attract a large assembly of aeronautical technicians on Wednes day last, March 12th, when Mr. Henry Knowler, A.M.I.C.E., F.R.Ae.S., director and chief designer of Saunders-Roe, Ltd., was due to deliver the fifth lecture of this important series. The lecture was to be read in French by M. I'lng6nieur en Chef Benoit, director of POmce National d'Etudes et des Recherches A6ronautiques, and a cocktail party and dinner were to follow. Mr. Knowler introduced his paper in retrospective vein, recal ling that Louis Bleriot's epic flight across the Channel in 1909, was "the inspired inception of a new era of travel." He then went on to describe representative contemporary flying-boat types—for ocean patrol, civil flying, fighting and amphibious operation— before turning to recent technical development. First he discussed air drag, remarking that the high air drag of flying-boats relative to landplanes was not inherent in the type, though it was admitted that up to and during the Second World War flying-boat hulls were poor aerodynamically. Analysis had shown that the most serious cause of drag was the main step, although a badly shaped bow could also contribute seriously to the increase. A step which retracted in flight was obviously the solution to the problem; it had been tried, but the weight and difficulty of maintenance had ruled it out as a practical proposi tion. Another solution used with considerable success was the addition of a fairing behind the main step. Mr. Knowler summarized by stating that model tests indicated that without sacrificing hydrodynamic qualities, by the application of the various possible means of drag reduction, the basic drag of the ideal streamline body need not be increased more than 10-12 per cent in converting it to a suitable hull form. This cost in drag could be compared with approximately 4-5 per cent increase which must be accepted for a typical landplane fuselage. Discussing water resistance, the lecturer said that because of the inter-action of the various components of the resistance, a change benefiting one item would almost certainly have a detri mental effect on the others; therefore the modern flying-boat hull tended to be a well-balanced compromise. Improvement in the hydrodynamic lift of flying-boat hulls had been subject to con siderable research, and work was still being done to this end, since the lowering of the hump drag could pay high dividends. One method explored was the use of hydrofoils by the use of which it should be possible to provide additional lift at low speeds for low cost in resistance. The most successful experiments had included two sets of foils, one at the bow and the other—the main lifting foils—just aft of the e.g. "Ladder" systems, which might include pronounced dihedral, had also been used. In their application to a flying-boat a possible solution was to use hydrofoil lift up to medium speeds and, after the foils had cavitated, to use the plan ing lift from the lower surfaces. Subsequently the foils would retract completely into the streamline body. The subject, in the lecturer's opinion, was worthy of further research because of the advantages offered in reducing both air drag and water resistance. Somewhat allied to the hydrofoil was the hydro-ski. This obtained its lift from the water pressure on its lower surface in a similar manner to the planing lift of a beat's planing-bottom; but a considerably higher loading could be used and, in con sequence, a higher attitude of the planing surfaces was necessary. The efficiency was poor compared with a normal boat form, but the system had the advantage that complete retraction into a streamline body was relatively simple. Hydro-skis were a com paratively recent development but considerable research had already been done in England and America in which their applica tion to high-speed designs had been investigated. The possibility had been shown of having a highly stable hydro-ski system which was capable of lifting an aircraft body off the water at relatively low speed. The hydrodynamic efficiency of a hydro-ski was low but, because of the possibility of total retraction, the system was very suitable for water-based fighters. Probably the most important factor in determining the general configuration of a flying-boat was the propagation of spray. Spray occurred in two forms: that emanating from the forward contact of the planing bottom with the water surface (ribbon spray) and the heavier form of spray—"blister"—which left the chine at its point of contact with the water. Both forms were due to the peak pressure developed in the stagnation area where the planing bottom intersected the solid water. Ribbon spray was fairly light and although it might cause inconvenience in misting up the wind screen and so on, it had no damaging effect on the structure, and since it first travelled forwards over the bottom surface, it could be directed downwards by curvature below the bow chine. On the other hand, blister spray had free release laterally and rose in a hollow cone of heavy spray. The height to which it rose deter mined the relative position of the airscrew tips and, in some cases, the position of the wing and tailplane above the water. There were various methods of estimating spray height, but perhaps the most Saunders-Roe Princess long-range transport, with Bristol Proteus turbo- props. The first flight is due this year. Saunders-Roe S.R./A.1 experimental jet-propelled flying-boat fighter (two Metrovick Beryls), precursor of a transonic design by Saunders-Roe.
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