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Aviation History
1961
1961 - 0234.PDF
234 FLIGHT, 24 February 1961 GENERATOR COOLING AIR EXHAUST TRUNK INTAKE CASING INTAKE VANES EHTRT DUCT FOR GENERATOR COOLING AIR GENERATOR DRIVE OIL SEPARATOR L.P. COMPRESSOR DRIVING SHAFT BEARING-SEAL AIR PIPE ' INTAKE ANTI-ICING VENT OIL DRAIN FROM L.P. COMPRESSOR FRONT BEARING RETAINING BOLT AND LOCATING DOWELS OIL SUMP MAIN SCAVENGE OIL FILTER \ STARTER LOCAT OIL RETURN FROM COOLER TO TANK AUXILIARY SCAVENGE PUMPS VERTICAL DRIVE SHAFT FUEL DRAI This drawing of the Olympus Mk 104 has been prepared by Bristol Sic'deley Engines Ltd who manufacture the Olympus at their Aero Division at Patchway, Bristol. The engine differs in many important respects from ths earlier unit described in "Flight" fcr December 9, 7955 Olympian Heights higher turbine entry temperatures which have been adopted tobring the dry rating up to the present Mk 104 value of 13,5001b, the engine has retained its reputation as a paragon of reliability.For example, last November two 104-powered Vulcans completed a 26,000-mile round-the-world-tour, taking part in the openingceremony of Rongotai Airport at Wellington, New Zealand. The engine maintenance required was, as at other times, almostnegligible, consisting of a visual inspection and filter check after 25 hours' flying (a job which can be done by one man in half anhour). On some global flights the Vulcans have been supported by a Britannia or Hastings (both Bristol Siddeley powered) ofTransport Command, but the engine spares carried have invari- ably been brought back to base intact. This exceptional reliability—combined with an overhaul lifevery high by military standards—is hrsely the result of progres- sive development of different mirks of Olympus before their entryinto service. The original BO1.1 made its first run on May 6, 1950. It led to the Mk 101, the first production version, ratedat 11,0001b and first run in October 1952. The 101 was fitted with N.90 first-stage and N.80A second-stage turbine blading, and wastype-tested in December 1954. Derated to 10,0001b, it flew in a Vulcan in February 1955; it operated at the full rating in July ofthit year, and entered RAF service with 230 OCU at Waddington, Lines, in July 1956. Next to enter production was the 12,0001b-thrust Olympus 102.Compared with the 101, its main difference was the addition of a zero stage to the low-pressure compressor, resulting in increasedmiss flow. The 102 was improved mechanically, but used the same turbine-blade materials as the 101. It was type-tested in November 1955 and entered RAF service with 83 Sqn at Wadding-ton in July 1957. After overhaul, Mk 102 engines return to the RAF converted to Mk 104 standard, with new turbine discs and bladesand burners of increased flow number to allow for the higher fuel flow. The 104 was initially rated at 13,0001b at 6,500 1-p r.p.m. anda j.p.t. of 645°C, and it was type-tested at this rating in December 1956. The first flight of a 104 took place in Vulcan XA 889 :tWoodford in July 1957. In addition to the work with this aircraft, flight testing was carried out by Bristol Siddeley's flight develop-ment team, using a Canberra and an Ashton. One problem was to ensure that the handling of the 104 didnot fall short of the standard set by the 102, of which it was stated in an official report that it "sets a standard of handling at altitudewhich has never been equalled by any other turbine engine. . . Initial flight tests of the 104 showed that there was a severe r.p.m.drop at high altitude while climbing. It was found that the air/ fuel ratio control (intended to operate only during acceleration, inorder to limit the extra fuel flow as a function of compressor delivery pressure), was controlling during steady running andoverriding the speed governor. The solution was to introduce a device which automatically isolated the AFRC at altitude. It wasalso found that the idling speed at 50,000ft was too low, and so the full-range flow control was recalibrated. Another respect in which the 104 differs from earlier marks isin having "mice," of a total area of 6 sq in, in the final nozzle for trimming purposes. This reduction of nozzle area ensuresoptimum handling characteristics at altitude. The engine is cleared for operation under icing conditions without any limitation, exceptfor a time limit on the use of low r.p.m. in such circumstances. The Mk 104 Described Starting at the front, the intake casing is a magnesium-zirconium casting, anti-iced by bleed air. Its hub
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