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Aviation History
1961
1961 - 0245.PDF
1LIGHT, 24 February 1961 247 SYSTEM SURVEY. may De set up. Basically, the Ferranti unit is rather like the navi-gation display of the Smiths roller blind Flight Data System for fixed-wing aircraft. It has a rotating compass card surroundinga plan-position display made up of roller blinds which can be positioned relative to the central fixed datum ring for fourdifferent modes, mid-course navigation, ILS, hover and land. The mid-course display, Fig 2c, provides range rings and bearinginformation. For ILS, Fig 2d, the arrow-shaped pointer appears and provides not only angular but positional information relative tothe localizer beam. Glide-slope displacement is shown on the height deviation indicator on the navigation display. Collective-pitch demands for glide-slope following appear beside the attitude display. There is a possibility that a glide-slope needle on the navi-gation plan-position display could appear almost parallel to the localizer arrow in cross-wind landings with high drift. Simulator trials by the Institute of Aviation Medicine indicatedthat a suitable type of pattern for a hovering display was the rectangular lattice pattern shown in Fig 2b. It is formed in theinstrument by two roller blinds—the upper one being transparent —each carrying a set of parallel lines. The lattice has no geo-graphical significance and is related only to movement relative to ground or water surface. It naturally depends on Doppler signalsfor its surface contact. The purpose of this mode is to tell the pilot, as he monitors the autopilot, exactly when the helicopter is Figs 2a, 2b, 2c and 2d show, respectively, the landing, hover, mid-course and ILS modes tor the navigation display X DATA SOURCESj AIITOPIinT fOMPIITFR LONG-TERM STABILITY FLIGHT DIRECTOR COMPUTER (LONG-TERM STABILITY) SHORT-TERM STABILITY COMPUTER Fig 3. Schematic layout of combined flight director and autopilot with duplicated automatic stabilization equip- ment. Stabilizer inputs are in series and autopilot inputs in parallel with the pilot's controls LOCALIZER (GLIDE SLOPE /DISPLACEMENT APPEARS ONHEIGHT DEVIATIONINDICATOR) o V 2a LANDING MODE 2b HOVER MODE 2c MID-COURSE MODE 2d ILS MODE stationary. After he has pressed the hover demand control of theautopilot in forward flight the transition begins, but he has no indication when he is actually hovering. The compass ring willcontinue to indicate his heading; and the track pointer on the compass card will show the Doppler-derived track. The landing display, Fig 2a, is intended for operation with aprecision approach aid giving both centre-line and range informa- tion. The parallel "tramlines" would indicate position relative tothe approach centre-line (localizer) and the single transverse bar would indicate range from the touchdown point. Tramline andrange bar always remain at right angles to each other and where they cross represents the touchdown point. The range signals arelinear so that some range-rate information can be derived. Beside the compass dial is the height deviation scale and, below,the height datum setting, the purpose of which is self-evident. The scale is long enough to provide some rate information and it ispossible to tell when the helicopter is settled at a given height. Radio altimeter, Doppler height sensing or barometric altimeterwould provide the basic information. If a flight director is to be used for monitoring an autopilot it isobviously necessary that both systems should produce the same control demands at any moment; and the computers for the twosystems will therefore be very similar if not identical. Ferranti might therefore contribute to the helicopter autopilot field with anintegrated instrument and control system in which individual data sources could be arranged to feed either of two computers, oneserving the flight director and the other the autopilot. Duplicated autostabilizers with a changeover could be integrated with thecontrol system and an advanced degree of duplication and standby would result. Fig 3 shows a layout of this kind. All-weather Helicopter Research in the United States IN terms of time and resources, the American helicopter andinstrument manufacturers, the Services and the Federal Avia- tion Agency are all some way ahead of their counterparts inBritain in achieving helicopter instrument flight and all that goes with it Particular examples are the helicopter anti-submarinesystems such as the IN, by Lear, and its successor the 2N, being developed by Hamilton Standard; the FAA helicopter operationsprogramme, now well into its second phase; and the extremely ambitious and uninhibited thinking involved in the helicopterportion of the Army/Navy Instrumentation Programme (ANIP) for which Bell Helicopter Co has the co-ordinating authority. Phase I of the FAA helicopter programme was designed toproduce an initial estimate of the problems of operation in and around a large city, with emphasis on the navaid to be used. Allfive of New York Airways Vertol 44Bs were fitted with Decca Navigator, which was operated for some months during normalpassenger-carrying flights. NYA did not, however, depart from its VFR, map-reading type of flying. New York is a very-high-density air traffic area, it has weather which varies from heat-wave summers to blizzard winters, and it includes ground obstructions•about as high as are likely to be found anywhere. The final report
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