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Aviation History
1971
1971 - 0851.PDF
752 FLIGHT International, 27 May Ml Avionics By T. M. B. WRIGHT T HE NAME FERRANTI has for many years been associated with the development of advanced military elec tronic systems, of which the terrain- following radar for TSR.2 was one of the most significant pieces of equip ment of its type in the past 25 years. The Edinburgh team is currently work ing on a new project which could well represent an equally significant ad vance; a helicopter radar known as Seaspray. This is a lightweight X-band system relying heavily on experience gained with equipment built by the firm for the Lightning and Buccaneer. It is designed to search for and track small, high-speed navel targets which, when equipped with surface-to-surface missiles, have formed a significant threat to ships ever since the Israeli destroyer Eilat was sunk by a Styx- equipped Egyptian ship in 1967. Sea- spray could also have application for general surveillance duties, for ex ample, Coast Guard rescue and fishery protection, or even (having regard to the recent Anglo/French agreement on shipping in the English Channel) for keeping a check on tankers. The equipment makes use of a new tech nique, frequency agility, which largely overcomes the adverse performance resulting from bad weather and sea conditions. The immediate application, and the one for which Seaspray is being de veloped under an MoD contract, is the Westland-Aerospatiale Lynx helicopter The radar has two main modes of operation, search and track, and trans ponder or IFF beacon. In the first mode, wide-angle (±90°) or limited- range scans may be used, automati cally selected pulse-lengths enabling the best performance to be obtained on each of three range scales. The fre quency-agility technique improves the performance by combating clutter, re ducing target glint and being resistant to electronic counter-measures. Infor mation is displayed on a bright flicker- free television display, the data appear ing in alpha-numeric form. The cathode-ray tube is designed to be readily adaptable to inputs from alter native low-light television sensors as well as radar. When used for tracking, the azimuth monopulse technique en ables high angular accuracy to be secured without problems due to coni cal scanning or sequential lobing. When used in the transponder or IFF beacon mode, the equipment can display data out to the maximum range at which it can operate. The actual range is classified, but bearing in mind normal operating heights it might be expected that small surface vessels could be detected at 50-75 n.m. Seaspray has been designed around the main precepts of small-ship opera tion : hard usage and limited main tenance facilities. It has built-in test circuits which enable first-line main tenance to be rapidly undertaken. Total weight of the equipment, which comprises transmitter, receiver, scanner, processing and display and control units, is only 1251b, a remark ably low figure in view of the com plexity inherent in the scan-conversion process. Ferranti reports that considerable interest is being shown overseas, in cluding the United States where, of course, the Lynx is a contender for the US Navy's Lamps utility helicop ter competition. • Sheila Scott's Arctic Aztec SHEILA SCOTT was due to take off yesterday, May 26, to position at Nairobi for a record-breaking attempt at a flight from equator to equator over the north pole. Her familiar Comanche "Myth Too" has been replaced by an Aztec D ("Mythre") supplied by CSE Aviation, who have also completed the avionic installation; the Aztec has long-range fuel tanks in the wingtips in addition to a fuselage tank which occupies the cabin from immediately behind the pilot's seat. As well as the navigation equipment, which includes lightweight Loran equipment, space has been found in the Aztec for a balloon interrogation package which has been supplied by the General Instrument Corporation under contract to Nasa. Throughout the flight the equipment will be interrogated by a Nimbus satellite in polar orbit and it Additional avionics pack the panel of the Aztec and the pilot's "busy box" can be seen on the extreme right. The large aerial is required for the Nimbus interrogation trial being run in conjunction with Nasa mi will relay six parameters including the air craft position. Mental response time will be recorded by a simple command which will require the actuation of a switch to cancel. Data will be fed from the aircraft via the satellite to a ground station at Fairbanks, Alaska. Miss Scott's transpolar route was not finally settled at the time of going to press but it is likely to be Nairobi, London, north Norway, Anchorage, San Francisco and Honolulu. The choice of the Norwe gian airfield is governed by the extreme all-up weight at which the Aztec will take off for the polar leg of the flight—a weight which is expected to exceed 6,5001b, 2,948kg.
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