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Aviation History
1960
1960 - 0009.PDF
FLIGHT, 1 January 1960 9 fig. 2. Essentially similar to the BE.53, this fighter engine produces hot and cold flows which can be ejected at any angle between hori- zontal and vertical to provide thrust and/or lift. The assembly shown solid black is from the Orpheus 55,OO01b. The two BE.53 engines will provide adequate cruisingthrust with a low fuel consumption, but there remains the weight penalty of the lifting engines. These will have a thrust/weightratio of about 14 :1, leading to an aggregate weight of about 7501b per engine for the thrust assumed. The total installed-weightpenalty therefore exceeds 3,0001b, but nevertheless such a VTOL aircraft might have a payload of up to 10,0001b and a high sub-sonic speed. For operations from conventional runways, using the two BE.53 engines only, the aircraft could be overloaded to agross weight of 100,0001b with a consequent substantial improve- ment in range and payload.Since the engine thrust is greater than the weight of the air- craft, the question may be asked, "Why are wings necessary?"After all, the helicopter has dispensed with wings. An impression of a jet-sustained wingless vehicle is shown in Fig. 5. If amaximum speed of up to 250kt is acceptable, the fuselage can be of simple construction and a clean aerodynamic form is nota primary consideration. To get some idea of the overall per- formance we can assume that the engine gives a lift of seventons for an installed weight of one ton. After allowing for the weight of the structure, crew ejector seats and a parachute forlanding the whole machine in" the event of engine failure, there is 4i tons available for fuel and payload. These very simplemachines would thus have a lifting capability almost equal to that of the largest helicopters, and roughly twice the speed.On the other hand, a much faster aircraft could be designed if the requirements for simplicity and light weight were notparamount. This fast aircraft (Fig. 6 depicts a strike machine) would have tiny wings which could just support it at itsmaximum speed at sea level. The aircraft would take off and land vertically, and at speeds below the maximum the jets wouldbe deflected downwards through any required angle in order to make up the difference between wing lift and aircraft weight.With this machine a substantial weight saving would be achieved as a result of the abbreviated wing structure and land-ing gear, and the drag would be reduced owing to the smaller and thinner wing. These two factors would together result inan increase in range over a conventional aircraft of the same take-off weight of over 60 per cent.Engines for the Airlines. For civil transports, the ducted fan engine has a threefold advantage over conventional turbojets: alower noise level (noise varies as the eighth power of jet velocity); a lower specific consumption; and a higher thrust/weight ratio. Under the cruising condition of modern jet transports, say500kt at 36,000ft, the reduced jet velocity of ducted-fan engines improves the propulsive efficiency, and yields a lower fuel con-sumption. One can draw curves to compare the specific fuel consumption of jet and ducted-fan engines against the thrustproduced by each lb of air per sec passing through the engine. For a straight jet engine a specific fuel consumption of 0.87 can Fig. 3. Shown for the first time is this Bristol Siddeley double-flow engine designed to provide lift during vertical take-off and landing. Thrust/weight ratios of around 14 : 1 are foreseen be obtained with a turbine entry temperature of 900 °K, and aspecific thrust of about 321b. If, however, the bypass ratio is increased to 2.0 in a ducted-fan engine, then, at about l,050°K,a specific consumption of 0.79 can be obtained at a specific thrust of about 19, showing an improvement of 10 per cent.The fuel load on a non-stop transatlantic jet airliner exceeds 100,0001b. A saving of 10,0001b of fuel not only yields a savingof fuel cost but more important enables 40 more passengers to be carried without additional operating cost. Although themarket for the large intercontinental subsonic jet airliner has been lost to the USA, this market represents only a small per-centage of world airliner requirements. The bulk of airliners with a range of up to 3,000 miles are still propeller driven, in thecoming decade these will be replaced by faster, more comfort- Figs. 4 and 5. A suggested high-subsonic transport with VTOL ability. Power is provided by two BE.53s and four specialized lift engines. The wingless jet-lift machine (right) could lift almost as much as the largest helicopter and fly at 250kt forward speed
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