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Aviation History
1951
1951 - 1903.PDF
382 FLIGHT, 21 September : Given scale by the people near it, the Napier Nomad with its Rotol co-axial airscrews was certainly the largest, one of the latest, and specifically the most economical engine in the show. Vickers Viscount 700. Brian Trubshaw's handling of the 700 showed to advantage its lively take-off. It was also seen to be highly manoeuvrable with both port engines feathered. The Viscount has been ordered by B.E.A. and Air France. A model, in the latter airline's colours, appeared on the Vickers stand. Saunders-Roe Duchess. A model of this medium-range Ghost-powered flying boat was shown on the manufacturer's stand. Helicopters the Bristol 171 Sycamore traced invisible arabesques,and the Westland S-51 demonstrated the latest rescue tech- nique to spectators out on the airfield, inside the exhibition tentrotary-wing aircraft developments were illustrated by models on the Bristol, Fairey and Westland stands. Bristol contented themselves with a large and elegantly finishedmodel of the new twin-engined twin-rotor Type 173; a detailed description of this fine machine appeared in the March 16th issueof Flight. Fairey also confined themselves to showing one model of a rotary-wing type—the new Rotodyne. This aircraft, an artist's impression of which appeared in our September 7th special issue, Mounted in a skeletal box, the Armstrong Siddeley Snarler rocket motor constantly received a great deal of attention. Water/methanol and liquid oxygen are fed by the fuel pumps (right) through the valve assemblies (centre) to the combustion chamber (left). bids fair to become a great success if design logic is a criterionBy scale effect, we judge that the model shown represented a 24-seater and, from the intake grille at the base of the rotor p< ,onit can be inferred that a third (buried) engine will be use > to supplement the outboard units—which will almost certainly beMambas or Darts. The essence of the design philosophy is that for take-off and climb, the Rotodyne will function as a -ruehelicopter, but for normal flight and landing, the aircraft will fly as a fixed-wing machine with the addition of an autorotating rotorAt the tip of each of the four rotor blades, incidentally, are smali jet ducts; presumably air supplied by the compressors of theturboprop units is fed to these tip ducts, together with fuel, and the mixture there burned to drive the blades by jet thrust. Westland had no fewer than five helicopter models on theirstand. The S-51 and S-55 are, of course, familiar to readers, and brief mention has also been made of the future projects W-80'W-81, and W-85 (Flight, June 29th). The first of these is a twin- Leonides-engined single-rotor 2O-seater, which, however, is likelyto serve merely as a stepping-stone to the W-81, a larger (30-seat) aircraft which will employ an internally housed power installationquoted as being "of the Twin-Mamba type driving the four-blade rotor through a right-angle gearbox." Considerably the largest ofthe three projects, the W-85 is designed to carry 100 fully equipped troops or equivalent military load. Its "box-car" fuselage is sur-mounted by a pylon carrying an immense three-blade rotor driven by tip units of "Twin-Adder type or their equivalent indevelopment." New Engines ALTHOUGH in terms of pure spectacle—"glamour appeal" if*» you like—other power units such as the exquisitely sectioned Perspex-cowled Proteus took pride of place, by the more mundaneyardstick of technological novelty the stars among the cast of engines in the static exhibition were, without doubt, the Napier :Nomad composite engine and the Armstrong Siddeley Snarler rocket motor. These two units, as opposed in concept, designedduty and appearance as could well be imagined, were constantly surrounded by interested viewers : what is more, this applied notonly on Tuesday, the day set aside for technicians, but on the following days as well. Before dealing with these units, however, mention must bemade of the exhibit by Alvis of the Leonides 550 b.h.p. nine- cylinder radial. The most completely sectioned engine we haveever seen, it was fully cut-away through the vertical plane of the crankshaft and was, in addition, admirably "show-finished." A high order of glossy enamel and bright-polished metal madethe Nomad glisten and sparkle, too. But one was far more inter- ested in finding which bit lead where and what such and such didand how that must do something else; an intriguing exercise. Differing in detail from the photographs of the unit published inour September 7th issue, the actual Nomad on the Napier stand at Farnborough was also equipped with co-axial Rotol airscrews;although the three blades of each of these were close-cropped, the hubs looked as if they might well suit the Saro Princess—as5 indeed,might the Nomad itself, and to some effective purpose. The power unit comprises a horizontally opposed 12-cylinderdiesel engine which, however, would have given Rudolf Diesel considerably to think for not only is it highly supercharged, it isalso a two-stroke and, what is more, it runs on paraffin. Crankshaft torque is given through a reduction gear to the rear airscrew.Exhaust gases are ducted from the 12 cylinders to one of a pair of turbines which, from the appearance of the shrouding, look to betwo- and three-stage components. A pair of auxiliary combustion chambers serve to burn additional fuel to amplify maximumthrust for take-off and, to this end, feed the other turbine. The front airscrew derives its torque from the turbine shaft, albeitthrough a reduction gear. Supercharging of the engine—or, at least, the gas-generatingpiston-unit part of it—is achieved through the medium of two entirely separate and quite different types of compressor. Firstthere is an axial-flow component which we believe to be a development of that used on the Naiad, but which now operatesat an unusually high compression ratio. This unit is driven by one of the turbines and delivers, without the interposition of an inter-cooler, into the eye of a centrifugal (second-stage) compressor, which is driven by the diesel half of the engine, and which deliversto the induction tract serving the cylinders. Thus, to sum up, the Nomad is a twin-supercharged dieseltwo-stroke which drives one airscrew, and has its exhaust gases delivered to a turbine for driving another airscrew, the airscrewsbeing co-axially mounted. Vital statistics so far publishable are that the Nomad produces 3,000 e.s.h.p. plus 320 lb residualthrust; weighs 4,200 lb dry; has a fuel consumption at maximum continuous power (s.l. static) of 0.36 lb/e.s.h.p./hr; is 10ft 6|»long, 4ft io|in wide and 4ft ijin deep. As observed in the opening paragraph, the difference betweenthe Nomad and the Snarler rocket could scarcely be more marked:
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