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Aviation History
1955
1955 - 0169.PDF
11 February 1955 169 SWITCH TOI.L.S. -SLOPE POINTER 'ES DOWN ^ OUTER ^T MARKER N 4E IN .L.S. 1UENCY \ J "1LOCALIZER COURSE Z7O DEG SELECTED Lr SELECT OMNI-BEARING 2SO DEG-TO" OMNI-RANGE BEACON \ OMNI-BEARING LINE 25 0 DEG-TO" then gradually move over to the other side. When the coursearrow and bar are lined up, he has an exact progress check which will assist him if he wishes in calculating the ground speed madegood and in adjusting his E.TA. accordingly. This type of pictorial indication of position relative to beams and V.O.R.stations is probably one of the most useful qualities of the Integrated Flight System.The course indicator can also be used in conjunction with a visual-aural range (V/A.R.), but in this case it will only give anindication of being on one side or other of the green or red, or amber or blue airways. The particular sectors still haveto be identified aurally. The fart that the course indicator will not show an exact relationshipto a V.A.R. range station is due rather to the characteristics of the range than to the instrumentitself. The V.O.R. coverage in the United States is in any case now complete except for one or two'blind" patches at 20,000ft, and V.A.R. ranges 'need not necessarily be used. While using thesystem for navigation the "LOC" and "G.S." failure warning flags may appear, but can be dis-regarded. I.L.S. Approaches. Throughout the foregoingprocesses of navigation, the pitch bar and horizon bar of the approach horizon function in the sameway as a conventional artificial horizon, using sig- nals supplied by the vertical gyro. The verticalfour-dot scale along which the pitch bar moves "Flight" photograph i ,e9r.ated Flight System instruments installed in the first pilot's panel of the Civil Aeronautics Adminis- tration C-47 Dakota based at London Airport. Besides the I.F.S. the aircraft carries V.O.R., twin A.D.F., D.M.C., duplicated I.L.S., Sperry A.I2 autopilot and approach couple and much else; it must surely be one of the most comprehensively equipped aircraft in Europe. represents a pitch attitude change of 15 deg for eachdivision. In order to assist in instrument flying, the pitch trim knob on the left of the approach horizon canbe adjusted to "zero" the pitch bar on the horizon bar, thus compensating for deviations in the aircraft's pitchattitude arising from variations in loading and trim. Subsequently, during an I.L.S. approach, each divisionon the vertical scale of the approach horizon indicates a 10-deg pitch change. To make an I.L.S. approach at the end of a cross-country flight, the pilot first homes, according to the local procedure in force, to the relevant V.O.R. orT. V.O.R. beacon, using the Integrated Flight System as described above. From the beacon to the I.L.S. outermarker is a procedure leg which can be set up with the heading pointer. Shortly before intercepting the I.L.S.localizer beam, he sets both the course arrow and the heading pointer to the in-bound localizer course andtunes in to the requisite I.L.S. localizer, glide slope and marker beacon frequencies. The red flags marked G.S.and LOC will move out of sight on the approach horizon dial when the aircraft comes within range of, respec-tively, the glide-slope and localizer transmitters. These flags appear when the services are out of range, not usedor unserviceable. The I.L.S./HDG switch is set at HDG and the course bar deflects to show the aircraft's relationto the I.L.S. beam. From this point until the final approach is begun, the steering needle should be ignored.At the outer marker, the pilot flies out-bound along the beam with the lubber line on the tail end of thecourse bar. Using the course indicator as for en route navigation, he makes the required procedure turn tobegin the I.L.S. in-bound leg. Then, just before the outer marker is passed, in-bound, the I.L.S./HDGswitch is set to I.L.S. The steering needle can, if required, be used duringthe procedure turn by setting the heading pointer to coincide with the aircraft heading during the turn; but.while the 180-deg course alteration is being made, the heading pointer should be adjusted in stages, not morethan 90 deg at a time. When "I.L.S." is selected, the glide-slope pointer will,in the normal way, show the aircraft well below the glide-slope until it reaches a point where it intercepts it.Thereafter, with the aircraft in the landing configuration, the pitch bar is matched with the glide-slope pointer,and the approach horizon will provide attitude, steering and glide-slope information. The glide-slope pointergives a direct and not a computed indication. When the aircraft is on the glide-slope, cross-wind correction ismade automatically, and a bank-limiter prevents the application of more than 25 deg of bank. The pilot should aim in all cases to keep the steering needlecentral. Thus when, as in the accompanying chart, he finds him- self to the left of the I.L.S. beam, the needle tells him to steert 0 the right. He then banks to the right and the needle once morecentres, so that it gives an on-course indication as soon as he is closing the beam correctly. The course indicator will, however,show him that he is to one side of the beam. As he closes it, the steering needle will deflect to the left, and by rolling the aircrafthe will return the needle to centre and will join the beam smoothly without overshooting. The steering needle provides steering
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