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Aviation History
1949
1949 - 1513.PDF
279 FLIGHT 8 Sept., 1949 DART TURBOPROP Details—and a Colour Illustration—of the Smallest Rolls-Royce Gas Turbine OF the British trio of small turboprops,the quality which perhaps chieflycharacterizes the Dart is a straightfor- ward, robust simplicity, which should earn merited praise from potential users. Some earnest of the popular future which undoubt- edly lies before this excellent little power unit is indicated by the impressive performance— in the widest sense—of the Vickers Viscount. Upwards of 850 engine hours (flying) have now been amassed by this aircraft without trouble; re-lights have been made at varying heights up to 25,000ft, from which it has been established that in re-starting the Dart is, if anything, easier than a piston engine; it has been generally agreed that the smoothness of running will set a new standard in airline travel; and the servicing aspect of the unit has caused no headaches whatever. As this exem- plary record is of a commercial airliner— albeit a prototype—and not a flying test-bed, the manner in which the Dart is fulfilling its promise of being a plain workhorse devoid of fripperies or '' temperament'' is gratifying. When we have dealt with the Dart on pre- vious occasions, the restrictions ruling were such that the giving of anything in the nature of a detailed picture of the internal geography was not possible. Now, however, as so well shown by the full-colour cut-away drawing on the following pages, the visceral layout of this neat little turboprop can be laid bare, and a most attractive piece of work it is. Immediately behind the airscrew blade roots are a concentric pair of annular air intakes, the wider, inner aperture serving the compressor, whilst the narrow, outer annulus gives on to the oil cooler. The latter is mounted on top of the engine immediately above the oil tank which, in point of fact, is cast integrally with the casing. Not only does this feature effect a useful saving in installation weight, but it also constitutes a self-contained lubrication system, whilst the hot oil provides some measure of protection against ice accretion in the intake trunking to the compressor. Rolls-Royce experience with centrifugal superchargers must be virtually unrivalled— the two-stage blowers used on R.-R. piston engines are recognized as the most efficient of their type ever produced—and this experience has been turned to good use in the Dart. Each of the single-sided impellers has 19 vanes smoothly matched with eye-rings of steel guide vanes locked to the impellers proper. Air entrained in the annular entry is swept inward REMtFOHMA \CE DIAMETER 32in. DRY WEIGHT 1,075 Ib. ' LENGTH 98in. Estimated Civil and Military ratings are given below for static conditions at sea-level. Rating Engine I / Aircraft . , „Speed ' ' "" " " ' ' Maximum Take-off and Combat Max. Continuous Cruising Normal Idling Approach Idling .11.1 1.400 1,420 1.475 ,570 715 1,120 1,150 1,205 1,300 1,435 45 60 Although potters in excess of 1,400 s.h.p. are shown a device, will be incorporated in the engine uel svstem to prevent 1,400 s.k.p. being appreciably exceeded.
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