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Aviation History
1963
1963 - 0675.PDF
647 FLIGHT International, 2 May 1963 TRI DENT . in the author's view, the Trident flight deck is "unsurpassed, and compares very favourably with any at present in use." In this picture of a mock-up to the full BEA standard the dominant feature is the white square of the Decca Doppler pictorial map display, but this equipment may not be adopted by operators outside Europe. The "barber's poles" of the Smiths PVD instruments are visible at the First Officer's station. Access to the pilot seats is gained round the outside with genuine blind landings with the Trident system suggests that when this stage is reached the PVD "barber's poles" giving pitch guidance should be disconnected, because their indications are so compelling that any PVD failure could lead to disastrous pilot intervention. Design requirement of the triplex system is one failure in 107 landings; its development is assured by the firm RAF requirement for it in the Belfast C.l. Electrics Although main power is generated at 115/200V, 400c/s by an alternator on each engine, the three channels are isolated both physically and electrically and may be paralleled only if the customer so specifies. The Trident uses the new Hobson 403 hydromechanical constant-speed drive, coupled to an AEI 22£kVA brushless gen erator with a 5min rating of 34kVA. An identical fourth generator is driven by the APU. Three TRUs supply 28V d.c. power, a Peto and Radford 25A-hr battery supplies 28V direct, and through a static inverter can supply vital a.c. for 30min in the unlikely event of a total generator failure. Points worthy of note are that the Hobson c.s.d. was designed especially to provide a long overhaul life in civil operation, and can be removed without removing the generator (and vice versa), that standardized US/UK details are employed (Cannon and Hellerman plugs and sockets, and Leach relays), that the main electrical compartment may be entered in flight, and that Page Engineering contribute a centralized warning system discussed later. Hydraulics The three independent systems are filled with Skydrol 500A, and energized to a nominal 3,000 lb/sq in by Vickers Inc pumps made by Sperry in Britain. Emergency power for all systems is provided by three integral pumps, two driven by a.c. motors and one by a Dowty-Rotol drop-out ram-air turbine; the latter unit is provided to enable the aircraft to be landed with all engines stopped. All hydraulic components are outside the pressure hull, those not behind the rear dome being in the main or nose undercarriage bays or, in the Trident 1C, in the APU compartment. The system safe life of 30,000hr is being proved on a rig of the whole hydraulic and control system. Fuel Any turbine fuel, or any mixture, may be used, and all tankage is integral inside the wing box beam. There are five tanks: centre; port and starboard inner; and port and starboard outer. No fuel management is required; each engine is fed from its own tank by two supply pumps, and a crossfeed is provided to enable all fuel to be used in the event of engine failure. Failure of any supply pump has no effect on engine performance, and failure of both pumps in one tank has no effect under average conditions up to 30,000ft. The system is fuelled through two underwing couplings, the rate at 50 lb/sq in being 465 gal/min. In addition, four over- wing gravity fillers are provided. Offload of all fuel is possible in 30min, using the pressure couplings and up to 7 lb/sq in suction, or the power drain coupling and the aircraft pumps. The control panel is in the nose-undercarriage bay. Cabin air Each side engine provides a bleed which is passed through a heat exchanger, a mass-flow controller and a cold-air unit, water extractor and silencer, and ducted into separate supplies for the passenger and flight compartments. Both supplies are controlled from the flight-deck systems panel. Although any one engine can maintain full pressurization, the centre engine is also equipped to feed both systems if either side engine should be shut down. System targets are: dP, 8ilb/sq in; cold day with minimum passengers, 60° to 80T up to 40,000ft; hot day with full economy class, 75°F on climb to 10,000ft and 70 thereafter; ground heating of empty aircraft to 60780° in 30min; ground cooling at 100° ambient with 46 per cent humidity and max passengers, 78:> interior. Warm-wall feeds lead to inlets below the hat-racks, with extraction at roof level to the underfloor discharge valves. System design is by DH Aircraft, with Normalair valves and Kollsman pressure control made by Smiths. Ice Protection Leading edges of wings (including slats or droop) and tail surfaces are heated by h-p and 1-p engine bleeds mixed to give a supply at 190JC. Separate bleed systems serve the side-engine intakes, the whole length of the centre intake duct, and the engines themselves. Distribution is so arranged that the engine intakes and the inboard wing ahead of the engines are protected to a higher standard than other areas. Triplex gold-film electrical heating is used for the windscreen, with even heating over each panel to avoid cooler regions at the edges. Detection is by duplicated Napier scrapers, and visual indication is provided by inspection lamps for the leading edge plus a heated probe outside the captain's window. Flight Compartment The Trident is designed for three-crew operation, with a fourth supernumerary, and the CWS (centralized warning system) already referred to greatly reduces work-load. It provides red or amber warnings within the field of forward vision of any system malfunction, thus indicating "immediate action" or "cautionary" situations to all three crew while the latter remain looking ahead. The system includes warning lights actually in the levers of appropriate hydraulic selectors, fire extinguishers and fuel h-p cocks. In the writer's opinion the flight compartment is un surpassed, and compares very favourably with any at present in use. Minor changes may be seen between the BEA (Series 1) layout, with Decca Doppler pictorial display, and IE instrumentation for use outside Europe. [Concluded overleaf
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