It is claimed that the Decca method of defining the vertical plane of the runway axis by means of low- Aviation Electronics frequency transmissions offers important advantages over landing aids using relatively high frequencies, such as the Instrument Landing System of which high- Details of Electrical and Electronic Apparatus with Applications in the accuracy versions for automatic landing are currently under development. I.L.S. stations, like V.O.R. trans Maintenance and Operation of Aircraft, Missiles and Space Vehicles mitting stations, are sensitive to the nature of the terrain immediately around them and can produce errors which are time dependent, necessitating calibra Electric Signalling for Aircraft Controls and techniques of equipment enabling airliners to land tion. In contrast, experience with Decca stations has on schedule, regardless of weather. A system, which uses electricity instead of push rods shown that their transmissions are extremely stable, The firms will interchange information on all aspects or wires to operate aircraft flying controls, is being especially over the short distances involved in an auto of equipments and systems in advanced engineering developed by the Royal Aircraft Establishment, Farn- matic landing system. The use of low-frequency trans programmes 'aimed at the eventual elimination of borough. missions would eliminate what has become known as weather as a factor in airline operation'. In large and fast aircraft it is becoming increasingly 'site error'; it would also avoid the phenomenon of To implement the Agreement the two Companies difficult to design mechanical links between the control interference from signals reflected from aircraft passing have set up a technical committee, under the joint column and rudder bar and ailerons, elevators and overhead which might occur with an azimuth guidance Chairmanship of Commander H. Pasley-Tyler and Mr rudder or the hydraulic jacks which control them. system of the I.L.S. type. R. P. Lansing, which will meet regularly in the U.S. Among the problems are those of keeping backlash Some of the techniques which have been evolved for and Britain for the purpose of reviewing and co-ordin and friction to a minimum where the control run may the Hi-Fix surveying system will be carried over for use ating the joint programme. be 100 ft. or more and overcoming disturbance of with the Decca azimuth guidance system, and it is control settings through flexing of the airframe or calculated that a lateral accuracy of better than I ft. I.L.S. Installations through temperature changes expanding or contract could be obtained at the runway threshold. Tests are ing the mechanical links. Work on the installation of the new STAN.7/8/9 being carried out with a view to studying the basic Instrument Landing System at Britain's major airports Electric signalling eliminates these mechanical dis behaviour of a system of this type under various is now well advanced. The contract, worth close on advantages. It makes it easier to use automatic environmental conditions. For the first series of tests equipment and opens the way to a sophisticated £400,000, was placed with Standard Telephones & it was planned to install the receiver in a ground manoeuvre demand system which will provide aircraft Cables Ltd. in 1960 by the Ministry of Aviation and vehicle so that an aircraft can be guided throughout responses largely independent of flight conditions, calls for the supply and installation of fourteen dual the length of the ground-roll along the runway as well ranging from those of supersonic cruising speeds to I.L.S. equipments. as to the touchdown point. those of landing. Electric signalling can be of partic Four systems have been installed at London (Heath It is also intended to carry out tests of another Decca ular value for V.T.O.L. aircraft which, because they row) Airport; two at London (Gatwick) Airport; one proposal for automatic landing comprising a pair of have no natural stability, require to be stabilized at the Ministry's training centre at Bletchley; one at stations on the two runway extensions which combine Manchester (Ringway) Airport; one at the Blind artificially. Another possible result of introducing the to generate a pattern giving a highly accurate indica Landing Experimental Unit, Bedford, with further system could be the miniaturization of the pilot's con tion of the aircraft's position along the runway axis. systems in hand at Prestwick and Manchester, and trols leading to a great improvement in cockpit layout. This could provide a very accurate indication of the another two systems planned for Scottish airports. The Royal Aircraft Establishment is now using an aircraft's position, and hence its speed, in that direc The STAN.7/8/9 I.L.S. equipment, comprising a Avro 707C, equipped with electrical signalling, to tion, and might well have a useful application in the Dual Beam Localizer (STAN.7) for azimuth guidance, investigate the characteristics to be preferred in take-off phase of a flight as well as in the landing and a Glide Path equipment (STAN.8) and Marker Beacon manoeuvre demand. ground roll. (STAN.9), fully meets the recommendations for Cate Although there is no difficulty in principle in replac ing the mechanical controls by a simple electrical link, gory 1 and Category 2 performance laid down at a Information Convertor or by a manoeuvre demand system, much work needs meeting in January of the Communication Division of to be done before it can be shown that an electrical the International Civil Aviation Organization. Equipment has now been installed at University control system can offer the very high standard of The I.C.A.O. Category 1 performance permits land College, London, by E.M.I. Electronics Ltd. for use in reliability that is essential. ings with a minimum cloud base of 200 ft. and a the analysis of data obtained from Skylark high-alti visibility of 2,600 ft.; Category 2 performance meets tude research rockets. This information concerns ultra more stringent requirements and allows landings to be violet radiation and soft X-rays from the sun, stars and Delay Generator made with a cloud base as low as 100 ft. and visibility space, and the conditions of ionization in the upper A new Delay Generator, Type TF 1415, is now of ¼ mile. Exact specifications for a Category 3 per atmosphere; its temperature, concentration and available from Marconi Instruments Ltd., St. Albans. formance have not been laid down, but envisage a character. The instrument provides sweep delaying facilities system which will permit 'operation down to and Known as TADIC, the Telemetry Analogue-to- (1Μsec to 500 m/sec.) when used in conjunction with along the surface of the runway unrestricted by cloud Digital Information Convertor, it is claimed to be the the Company's TF 1330 (series) or similar oscillo base and visibility conditions with a high probability first fully transistorized equipment of its kind in this scopes. Alternatively, it may be used independently as of landing success'. country, and the telemetered information from Sky a general-purpose delay generator. It generates a sweep The STAN.7/8/9 employs a dual beam localizer, lark shots in Australia, is recorded on magnetic tape, voltage commencing at a selected point on an applied providing a narrow course beam which results in a on coded frequencies in the range 35-65 kcs. TADIC waveform, a trigger pulse delayed by up to 500 m/sec., substantial reduction in course bending due to site is used to convert this analogue tape recording into a and a bright-up pulse coincident with the trigger pulse. imperfections; while retaining the all-round clearance form in which it can be analysed on a digital computer. The various uses to which the generator and an path required to fully meet Category 2 performance The magnetic tape is first replayed into a frequency oscilloscope may be put depend upon two basic opera requirements. Many advanced engineering improve discriminator, to produce a voltage output of the same ting conditions. In the first, the oscilloscope is switched ments have been incorporated, and overall system form as the time division multiplexed input to the to operate from an external time base, and the X-de- reliability is ensured by a comprehensive, fully transis telemetry transmitter. This waveform is fed to a fast flection waveform is supplied by the sweep output torized fail-safe monitoring system linked to a fully analogue-to-digital convertor and the digital output from the TF 1415. The waveform to be examined is automatic changeover unit. recorded on a secondary magnetic tape. then displayed with the T F 1415 adjusted to a suitable At the same time as data are replayed from one time-base setting. Z modulation by the bright-up pulse Azimuth Guidance for Automatic Landings track, time of flight to millisecond accuracy is replayed produces a bright region on the display to indicate the from another. This time is digitized and recorded on The Vickers VC10 and the de Havilland Trident are relative position of the delayed pulse. In addition to the secondary magnetic tape at periodic intervals. the first civil transport aircraft to be designed from the providing an accurate method of time measurement, At present, the computer being used by University outset to accommodate automatic landing systems.* adjustment of the calibrated delay controls enables, the College requires a punched paper tape input. It is These systems are based upon the work carried out by pulse to be set to the precise starting position on the therefore necessary to replay the digital magnetic tape the Ministry of Aviation's Blind Landing Experimental waveform where more-detailed examination is re on TADIC at a reduced speed, to produce another Unit at Bedford, which employs a pair of leader cables quired. recording on punched paper tape. which extend about a mile from the runway threshold The second operating condition is then used, in and along some or all of the runway itself, to provide which the oscilloscope's internal time base is triggered azimuth guidance during the final stages of the auto Astro-Sextant Development Contract by the delayed pulse, and adjusted to an appropriate matic landing. The magnetic fields generated by these A contract for the development of automatic speed to give the desired display detail. cables serve to hold the aircraft on the centre line very astro-navigational equipment has been placed with By using the TF 1415 in the above manner, it is accurately, but the method has the obvious disadvan Kollsman Instrument Ltd. by the Ministry of Aviation. possible to: (i) make accurate incremental measure tage of requiring a great deal of clear space beyond the This device is a development of the K.S-85 photoelec ments along a complex waveform, (ii) measure pulse- runway to take the leader cables. These leader cables tric sextant, standard installation on the B.57 aircraft. to-pulse intervals and amount of jitter on computer are also prone to interference from metallic objects. This type of sextant contains a small photoelectric signals, or any train of pulses, (iii) display any selected Much thought is being given at the present time to telescope that automatically searches for, acquires and individual line of a composite television signal, and the possibility of finding a suitable alternative to the tracks pre-selected celestial bodies. These bodies in (iv) utilize calibrated sweep magnification up to the leader cable system for azimuth guidance, and among clude, in the daytime, the sun and the planets and at highest practical limit. the techniques under consideration is a variant of the night, all stars equal to or brighter than Polaris. In addition, delayed sweep is particularly valuable in Decea Navigator comprising a pair of very small trans Kollsman Instrument Ltd., Bracknell is the British specialized studies such as ballistics, wind tunnel re mitting stations sited astride the runway threshold. subsidiary of Kollsman Instrument Corporation, Elm- search, rocket and plasma propulsion, computer stor This arrangement serves to define a plane standing hurst, U.S.A., who claim to be in the forefront of the age research, ultrasonics, and in many other fields. vertically on the runway axis; the airborne receiver development and production of manual, semi-auto would issue right/left signals to the automatic pilot so and auto-navigational aids for celestial navigation. as to hold the aircraft in that plane throughout the U.S./British Agreement on All-weather Flying Past and present production includes an astro- approach and landing. Developments tracker system which is an integral part of the B.58 An Agreement has been reached between the Bendix Hustler navigational system; automatic astro-compass * See 'Trident Flight Control System*, AIRCRAFT ENGINEERING, Corporation of America and Elliott Brothers (London) for B.57 aircraft and an astro-tracker system used to January 1962, pp. 12-19. 'VC10 Automatic Landing System', Ltd. for technical collaboration in the development AIRCRAFT ENGINEERING, June 1962, pp. 172-178. help guide the Hound Dog missile on B.52 aircraft. July 1962
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Jul 1, 1962
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