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Aviation History
1964
1964 - 0723.PDF
416 FLIGHT International, 19 March Fig 7 Electrical generator drive rig, with the Plessey constant-speed drive unit TESTING THE BAC O N E - E L E VE N . . . ponents correctly spaced and there are facilities for superimposing flight loads, environmental conditions, vibration and simulated faults, together with fluid contamination. In parallel, a flap-operating screw-jack has been working since March 1963 to establish the wear rate as well as the overall endurance and life of the component. An electrical supply and control system rig at Weybridge has all the items and wiring, including the generators and Plessey constant- speed drives, the latter being powered by electric motors which can be controlled to simulate engine behaviour (Fig 7). This rig has been going since April 1963 and will be retained for several years for fault analysis. The constant-speed drive unit is also under test at the Plessey laboratory and on the Rolls-Royce test beds during Spey running trials. The 30kVA generators on the One-Eleven are derated from the 40kVA models fitted on the Boeing 707 and Vickers VC10, being of Westinghouse design made under licence by Plessey. These were chosen because of their good service record and, as standard equipment, they are not being life tested. The air-conditioning system in a new airliner can be the source of much troublesome delay. That for the One-Eleven has been very carefully and extensively proved on the ground before flight (Fig 8). The air-conditioning/pressurization system is supplied by compress- or bleed air and this is also used for anti-icing, the systems being common up to the point where air is ducted away to the wings. The combined systems are tested in four groups: engine bleed and supply temperature control system; air-conditioning and pres- surization units; the whole system without the foregoing; and the anti-icing equipment. Engine bleed air comes from the 1-p and h-p compressors of the Spey, the 1-p air being used to maintain the h-p air temperature at a maximum of 230 °C through a heat exchanger. Engine anti-icing is supplied direct by h-p air at its delivery temperature. Before the One-Eleven flew, Rolls-Royce ran a Spey pod on the bench for 50hr with all the systems connected. Air-conditioning systems are fully duplicated on the aeroplane, with crossover facilities in case of failure. The cold-air unit, two heat exchangers, water extractor, ram-air intake system (to cool the heat exchangers), and a ground cooling-fan form a group; and the makers, Normalafr Ltd, have been testing both the units and the system as a whole since March 1963. The primary heat exchanger receiving the h-p air is being given a thermal fatigue test to evaluate its life and, if necessary, extend it. The pressurization equipment, discharge, safety and inward-relief valves with their controlling devices, have also been under test since March 1963—even though they are similar to those on the VC10, Comet and Trident. A mock-up cabin section and flight deck was used to check the delivery and control of the air system; Fig 9 shows flow-visualization in the cabin. Closely linked with the foregoing is the AiResearch GTCP 85-115 APU, which is mounted in the tailcone. The installation has been under test in a mock-up rear fuselage (Fig 10) since May 1962. This was first used for proving the a.p.u. part of the system, after which it has been tested in conjunction with the full cabin system. Aerofoil anti-icing was investigated as long ago as 1961, using a small section of leading edge in a spray wind-tunnel. This was used to establish the basic requirements for airframe detail design. Aerofoil de-icing is essentially a system which can only be fully tested during flight trials—when the biggest snag, even in British skies, is to find the right type of cloud where and when it is wanted. Since the fuel system of the One-Eleven was virtually scaled down from that of the VC10, it was not considered necessary to have an extensive test programme and pre-flight trials were limited to the following three system checks. A short root-end length of tank (i.e., torsion box section) was put into the VC10 attitude rig so that it and the engine feed system could be tilted through the range of design cases of pitch and roll. The Vanguard fuel system rig was used to assess the venting, refuelling, defuelling and crossfeed systems, which are not affected by the tank shape. Fifth- and tenth-scale models were used for the tank gauging and flow experiments (Fig 11). As the structural layout and flow are interelated, these were early tests and were started in March 1962. Test and development of the Rolls-Royce Spey is a long story in itself. It includes some 14,000hr on the bench—both the bare engine and the complete pod (designed at R-R Hucknall) on ordinary beds and in the altitude cell—plus lOOhr in a Vulcan during 1961. After the first Trident flew, in January 1962, a flying test-bed became superfluous. By February 1964 the Spey -1 had over 7,000hr in the Trident and about 200hr in the One-Eleven. The military Figs 8 and 9 Air-conditioning tests: the full-scale, correctly positioned piping system (left) for air distribution and flow visualization in (below) a cabin mock-up section
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