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Aviation History
1957
1957 - 0198.PDF
198 PLIGHT, 15 February 195t 16,000 lb THRUST —and Ready for Production: Bristol's Olympus 6 The Olympus 6 presents a singularly clean exterior. BETWEEN January 10 and 23 a Bristol Olympus 6 turbojetwas subjected to a series of trials under type-test conditionsin order to prove the brochure performance of 16,000 1b thrust. As we reported last week, the results have been out-standingly successful. There is no reason to doubt that the engine is now ready for production, and it is certain that there is noforeign engine of similar size or weight and in a comparable state of development which can match the Olympus 6 in its combinedvirtues of high thrust and low consumption. There are many who still think of the Olympus as a unit of9,750 lb thrust—the rating established by the original BOLL It takes time to appreciate that the same family of engines has nowthrust forward to almost double that figure—and, what is equally That modern engine test-houses can be fine architectural achieve- ments is emphasized by the facade of the new Olympus installation. important, is nearing the fully developed state at the vastlyincreased output. Clearly, Bristol Aero-Engines have achieved something monumental in the way of extracting more power froma given compass; and yet the Olympus 6 is a long-life engine, with easy-going temperatures and with every prospect of building upa reputation for reliability fully as good as that established by its predecessor, the Olympus 100 series. The first prototype Olympus was started on the bench for thefirst time in May 1950. At that time it was the only two-spool, or split- (or compounded-) compressor engine in the world, apartfrom the first experimental Pratt and Whitney J57s. As we explained in our full description of the early Olympus in Flightof December 9, 1955, the work of compression was so divided between the two spools as to enable each to be driven by a singleturbine stage. There were, in fact, six stages on the low-pressure compressor and eight on the high-pressure spool. Starting off at9,140 lb thrust, the "first generation" of the Olympus family passed into production early in 1955 at a rating of 11,000 1b dry.As an indication of the general level of performance achieved by the first production model—the Olympus 101—the maximumcontinuous cruising rating is 9,650 lb at a specific fuel consump- tion of about 0.75, and the engine has demonstrated its ability toaccelerate from idling to 11,000 lb thrust in five seconds. Although there has been no official disclosure, it is a safeassumption—for the very good reason that there is no alternative application—that the Olympus 101 was supplied for the firstproduction batch of Avrq Vulcan bombers. It may be supposed that Vulcans at present being delivered are fitted with the Olympus102, or BO1.11, which went into production rather more than a year ago at 12,000 lb thrust. Two of these engines, fitted to theelderly Canberra test bed WD952, established a world record for absolute altitude of 65,889ft in August 1955, beating the 63,668ftlevel achieved by the same aircraft (with earlier Olympus) in May 1953. Compared with the 101 the 102 has a lower hub/tip ratio inthe compressor intake—denoting a greater mass flow—and an added zero-stage, suggesting a higher pressure ratio. In spite of this impressive development it has long been appre-ciated that Bristol's knowledge was adequate to plan a completely new engine, of much greater thrust, around the original Olympusdimensional envelope. Known as the Olympus 6, the project began in 1952 and the first of the new Olympus family went on tothe bed on September 27, 1954. Into this new engine is built a truly massive experience gainedwith a remarkable variety of earlier Olympus, some fitted with afterburners or other appurtenances, and flown under all kinds ofconditions. Throughout their work the Bristol design team, led by Dr. Stanley Hooker, progressed more surely, and more rapidly,than had been possible with the original members of the family. Walking round the BO1.6 one is struck by the fact that it is nolarger than any other Olympus; in the form in which it is pictured here it is fractionally over 40 inches in diameter and has anoverall length of some 150in. An even more remarkable fact is that, by examining the ribbing on the casings of the two com-pressors, one can arrive at the startling conclusion that each spool has one fewer stage than the corresponding part in the Olympus101, i.e., five and seven, respectively. That this should denote a lower pressure-ratio is most improbable, and so it can be assumedthat Bristol have achieved excellent values for work per stage. As an outcome of this fact one is faced with the contentionthat, as far as the main rotating assemblies are concerned, the new engine is actually shorter than its forbears; and thus it is in allprobability no heavier. A typical dry weight for a first-generation engine was 3,650 lb with full equipment. It is possible, therefore,to arrive at a thrust/weight ratio of some 4.5, and also to calculate that the thrust per unit frontal area is roughly 1,850 lb/sq ft— To muffle the thunderous efflux from the Olympus 6 the test-house has bifurcated Detuners with upturned outlets. The installation is equipped for running a pair of Olympus-size engines simultaneously.
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