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Aviation History
1955
1955 - 0168.PDF
168 FLIGHT COURSE BAR CENTERED STEERING COMPUTER CORRECTS FORCROSSWIND CLOSING ON 270 DEC COURSE WITH NEW HEADING COURSE DEVIATION WIND LOCALIZER TRANSMITTER KEEP NEEDLE CENTERED •KEEP NEEDLECENTERED ACCURATE APPROACH. GLIDE-SLOPE POINTER ANO PITCH BAR MATCHED GLIDE-SLOPE INNERMARKER This chart of a hypothetical I.L.S. approach to a localize: beam bearing 270 deg shows the instrument reactions during en route navigation and final approach. It has been assumed that the pilot wishes to approach the V.O.R. beacon along the 250 deg radial bearing. INTEGRATED FLIGHT SYSTEM . . . steering instructions are provided by the steering needle (1)(painted fluorescent yellow) which can be used either while hold- ing a heading during normal flying or for holding the I.L.S.localizer beam on the approach. In the first case, the I.L.S./HDG switch (2) is set to HDG and in the second it is set to I.L.S. Inthe latter case, automatic correction is made for cross-wind effect. The horizon bar (3) and the bank pointer (4), both paintedfluorescent yellow, together indicate lateral attitude in the same way as does a conventional artificial horizon. The pitch bar (5)(again fluorescent yellow), symbolizing the wings and fin of the aircraft, gives pitch-attitude information, again in the same wayas the artificial horizon. The rotation of the pitch trim knob (6) lowers or raises the pitch bar so that a required pitch attitude canbe "zeroed" on the horizon bar to make attitude holding easier during an instrument approach. Finally, the glide-slope pointer(7) (painted fluorescent green) moves up and down the vertical scale (coloured red and green) to indicate the aircraft's position—by the pitch bar—relative to the guide-slope. Method of Operation. The makers recommend that the Inte-grated Flight System instruments should be centrally positioned in the normal blind-flying panel, with I.L.S. marker and airwaysfan-marker lights, clock and gyro monitor indicator close by. Before take-off, it is possible to perform a complete pre-fiightcheck on both approach horizon and course indicator, making use either of V.O.R. and I.L.S. facilities in the immediate area ofthe airfield, or otherwise of external signal-generating equipment. The checks are quite simple to perform and provide a positiveindication of satisfactory functioning. The use of the system for en route navigation is here divided between the holding of compassheadings, the use of omni-courses and the taking of V.O.R. fixes. In practice, however, the three functions can be used almostsimultaneously. Both the approach horizon and the course indicator can be usedto turn on to and to hold a compass heading. The I.L.S./HDG switch is turned to HDG and the heading selector knob used toturn the heading marker to the desired point on the azimuth ring. Thereafter, so long as the aircraft is on the selected heading andin straight and level flight, the steering needle will remain centered. Any deviation in bank or heading will cause the needle to move tothe left or right and the pilot then follows the needle indication by applying bank to restore the flight-path. To turn smoothlyon to a selected heading, it is simply necessary to follow the steering needle by banking the aircraft with it. So far, only the outer portion of the course indicator has beenmentioned; the central portion, related solely to radio aids, functions in the following manner. With the I.L.S./HDG switchat HDG, the navigation receiver is tuned to the desired V.O.R. beacon. When within range of the station, the red flag in theapproach horizon marked LOC will disappear and the course bar will deflect. If the course arrow is rotated until the course barlines-up with it, it will indicate the bearing of the V.O.R. station. If, on the other hand, it is desired to approach the V.O.R. stationfrom a given direction, the course arrow is set to that direction and the heading pointer set, for example, to a 50-deg cut-off vector.The steering needle will then direct the pilot to apply bank and turn on to the course, giving him instructions which will makehim hold his lateral attitude and heading. When the course bar begins to close the course arrow, the head-ing pointer is rotated to coincide with the course arrow, and the steering needle will then direct the pilot on to the V.O.R. bearing.During this time, the to-from pointer should coincide with the head of the course arrow to ensure that the pilot is flying towards,and not away from, the beacon. When the aircraft is on course towards the beacon, the heading pointer, course arrow, to-frompointer and course bar will all line-up with the lubber line and miniature aircraft to form a straight white line along the aircraftheading. Any deviation from course will appear as a displacement of the course bar, each dot on the transverse scale equalling 2 degerror. If a cross-wind affects the aircraft the heading pointer shouldbe offset in proportion, and in opposition to the drift. The steering needle will then be centered when the aircraft is headed correctlyto maintain the course to the beacon. Station passage is shown by reversal of the "to-from" arrow. It is easy to obtain a fix from anumber of V.O.R. beacons by tuning in successively to each beacon and rotating the course arrow until the course bar linesup with it. The resultant series of bearings can then be plotted on a chart. The two above functions can be combined to provide an indica-tion of progress on a cross-country leg which does not pass directly over a beacon. If a course is plotted from one point to anotherwith no beacon en route, the pilot can select a V.O.R. station some distance to one side of track, at the half way mark for example,and when he approaches it, he can set the course arrow at 90 deg to his heading and tune in to the V.O.R. station. As heapproaches the V.O.R. radial, the course bar will indicate on which side of the radial the aircraft is flying. As it crossesthe radial, the course bar will close the course arrow and
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