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Aviation History
1963
1963 - 0793.PDF
764 FLIGHT International, 23 May 1963 INDUSTRY International Flight Systems Products Company News Great Britain FLIGHT SYSTEMS Extended Range VHF That the timing of International Aeradio's symposium on extended range VHF met the requirements of the airlines, the manufacturing industry and the various international and govern mental agencies was evidenced by the attendance of no fewer than 200 delegates, representing 93 organizations, in London on May 7 and 8. Such an attendance provides a measure of the general awareness of the need to improve air/ground communications on many segments of the world's air routes. HF radio-telephony is now generally considered to be incapable of meeting the growing operational requirement for direct pilot/controller communications, because of overloading and misuse of the existing mobile networks, and the unreliability of such systems because of their inherent radio propagation characteristics. This unrelia bility is also considered to inflict excessive work-load on flight crews, because repeated attempts are often needed to pass operation ally significant messages. Single side-band HF, which once appeared to be a possible solution to the problems, is now no longer regarded as such, although it may eventually be used on those long over-desert or over- water routes where the provision of VHF links would be impracticable. Throughout much of Europe and North America, repeater stations and well-developed land- line systems provide good general coverage. It is for the other areas of the world that extended range VHF is proposed. Seventeen papers were read to the IAL symposium and each was discussed. Papers by Aeronautical Radio Inc, FA A, Pan American Airways and IAL provided evidence of the increased range made possible by special radio stations at carefully- chosen sites. The stations discussed were Cape Cod, Mt Washington, Lookout Mountain, San Francisco and Honolulu within the USA, and Beirut, Bangkok, Bahrein, Puerto Rico, and Okinawa else where. Comparisons made it apparent that results vary widely from station to station, seasonally and according to weather con ditions, particularly with temperature dis tribution within the atmosphere. The "ducting" phenomenon associated with temperature inversions are assumed to account for the astonishing occurrence of San Francisco communicating with an aircraft on the ground at Honolulu. This San Francisco station considers communi cations over 500-mile ranges to be "poor," although similar performance would be unusually good elsewhere. Honolulu achieves 400-mile ranges with 90 per cent reliability. The IAL station at Bahrein shows marked seasonal changes with ranges better than 450 miles throughout January, but less than 300 in November. Papers contributed by IAL, Standard Telephones and Cables and Marconi discussed the need for improvements in aircraft equipment, radios and aerials, in order to achieve maximum performance. Some astonishing figures were quoted for db losses in leads, connectors and "feeds" in typical existing aircraft equipment. Proposals for improving the performance of aircraft aerials were also made. Spokes men for aircraft manufacturers pointed out the difficulty of adding further aerials to those needed for existing communication, navigation and autolanding equipment. The airlines indicated that they do not favour the provision of special equipment for extended range VHF, but the possibility of removing HF equipment is very attrac tive to the regional and medium-haul airlines. BOAC believes that the ultimate require ment is for the automation of routine communications, by data link or other means. The BALPA spokesman pointed out that pilot experience with airborne radio-teletype using LF frequencies had caused IFALPA to state a requirement for the wider implementation of such systems. The possibility of combining RTT and extended-range VHF was attractive to several delegates. Toward the end of the symposium the problems of implementation were examined. IAL demonstrated that the provision of extended range VHF at only seven locations, when used in conjunction with existing VHF systems, would provide complete VHF cover over the London to Johannes burg route. Only five 450-mile range stations within the North Atlantic region would allow 65 per cent of the existing communications load to be transferred from the HF networks. On other routes, extended range VHF could similarly effect a sub stantial reduction in HF communications. This would avoid the otherwise inevitable and enormously difficult task of providing additional HF facilities. There are, for example, already 54 HF facilities listed in the ICAO AFI regional plan. Statements made during the meeting by IATA, ICAO and BALPA indicated strong support for extended range VHF, and the existing operational and trial installations have demonstrated the feasibility and economy of such systems. It may be concluded therefore that the IAL sympos ium was both timely and constructive, and that extended range VHF systems may soon be making an effective contribution to the safety, reliability and economy of air transport operations. PRODUCTS New Nimonic Applications Wiggin Nickel Alloys is the journal of Henry Wiggin & Co Ltd, whose vast new plant at Holmer Road, Hereford, was described in this journal on July 6, 1961. The current edition (No 70) reveals that the Bristol Siddeley Pegasus vectored-thrust turbofan incorporates Nimonic 115, 105 and 90 creep-resisting alloys, Nimonic 75 and PE11 heat-resisting alloys and Nimocast PE10 and PK24 heat-resisting casting alloys. This publication invariably contains several articles of aeronautical interest. No 70 describes, within the limits imposed by security, the ducting system of the Venezuelan Visitor to the Avro factories at Woodford and Chadderton earlier this month was the Minister of Communications, Capitan de Fragata Pablo Miliani. In addition to seeing the design, research and production facilities, he was given a full presentation on the Avro 748. L to r in the picture are: Dr D. Nicete; Mr M. W. Davies Board of Trade); the Minister; Sir Harry Broadhurst, Avro managing director; Mr M. J. Brennan, chief engineer, aircraft; Mr J. E. Farrand, technical sales engineer
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