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Aviation History
1962
1962 - 1129.PDF
53 FLIGHT International, 12 July 1962 Testing the VC10 THE VC10 was, of course, designed from the outset to spend 90 per cent of its normal operating time under autopilot control and it will be the first airliner delivered with a fault- survival flight control system, that is an FCS which will continue monitored automatic control after a failure in one part of the overall system. Elliott Brothers (London), who have designed the monitored duplicate autopilot, ultimately intended to allow automatic landing, have actually delivered a complete system to Vickers and much of it was installed at the first flight. One of the yaw dampers and part of the flight instrument system were actually engaged. The autopilot should be used as a flight test aid by September and formal autopilot testing should begin at the end of the year. Automatic landing trials may start at the end of 1963, but automatic landing is not expected to become a routine airline operation until the end of this decade. Few modern airliners will demand such an intensive flight and systems testing programme as the VC10, not only because of its size, but also because of its automatic landing capability. This programme is aimed at obtaining a full C of A for airline operation in the autumn of 1963, and some idea of the complexity of the testing pro cess is conveyed by the fact that the weight of test instrumentation in the prototype—15 tons—nearly equals the gross weight of Vickers' first post-war airliner, the Viking. Information on resonance and vibration will be stored by a 14- channel magnetic tape recorder and a 10-channel oscilloscope, fitted with Polaroid cameras. Four 50-channel trace recorders wfll gather measurements of strains, vibrations, stick forces, control positions and so forth, while a 270-channel Midas ejectable flight recorder will collect data to be used in determining fatigue life. Other equipment includes a 500-channel Solartron data logger, with a scanning rate of 100 channels a second. Beneath the fuselage floor are six tanks holding a total of 600gal of water. The water will be electrically pumped from tank to tank to alter the position of the VClO's centre of gravity during certain tests. The water tanks also act as heat sinks to absorb the power generated by 12 3kVA immersion heaters, which are used to impose a resistive load on the aircraft's alternators. Power for the pumps is derived from an independent flight test electrical system. In the event of its failure, emergency batteries provide sufficient power to move the water back and so restore the centre of gravity to its correct position before landing. The emergency power supply can also be used, at the master observer's discretion, to operate a selection of instruments. Half way along the fuselage is a digital recording system for engine speed, fuel flow, temperature and other data. This is housed in a series of temperature-controlled cabinets. Close temperature control is essential to ensure the extreme accuracy demanded in the VC10 flight test programme, since small fluctuations in temperature as a result of changing climatic and operating conditions have an effect on digital recording systems. A similar cabinet contains an instru ment which measures 192 temperatures every 27 seconds, stores the information on punched tape and also prints it for the flight observer. Outside the fuselage, three television cameras will photograph different sections of the airframe. One, mounted in the bullet nose of the tailplane, scans tufts which provide a visual check on the airflow over the wings and the engine nacelles. A second, on one of the outboard engine nacelles, looks up at the intersection of the fin and tailplane 30ft above it, while a third, retractable camera scans the underside of the fuselage. During stalling tests, the VC10 will trail behind it a "bomb"—a streamlined container housing a pressure transducer made by Bristol Aircraft's Industrial Products Group, which will accurately measure the free stream airspeed. Three VClOs will share the flight test programme. The first will be mainly concerned with airframe testing and, on completion of flight tests, will be retained by Vickers-Armstrongs. The second, destined for BOAC, will prove the systems, and the third will be used mainly for tropical trials. In addition, a fourth airframe is being used for ground structural tests. On complet- tion of a full series of static tests the same test specimen will undergo a fully representative fatigue programme followed by fail-safe tests. A life of 30,000 flying hours has been the design objective.
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