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Aviation History
1963
1963 - 0319.PDF
aLlGHT International, 28 February 1963 303 and rotating cylinder, is covered by a black shutter if either auto pilot or instrument fail. BOAC consider that the pilot should not be required to distinguish between instrument and autopilot failure during the tense moments of an automatic approach, at least in the early stages of operation. In the VC10, failure of one monitored autopilot leads, of course, to engagement of the other system and, for this purpose, the second situation display remains in operation. On the right of each display is the radio altitude vertical tape and flare-out check and annunciator panel. Here, Elliotts have decided to display radio altitude from 500ft to zero in complete figures on a vertical tape moving past a fixed pointer so that, during an approach, the tape appears to stand still while the aircraft moves down past it. Three height figures can be seen at all times and the figures pass the datum mark at the rate of approximately one per second during a normal approach. The pilot will probably be able to obtain some rate information from this movement. During cruising flight, the height display is covered by a cross-hatched pattern. When the pilot presses the test button for the altimeter system—probably at 1,500ft —the height panel gives an appropriate check read-out if the alti meter is functioning correctly and then begins to show height figures when the aircraft reaches 500ft, the maximum height indication of the radio altimeter system. When the flare-out phase is initiated, a flag appears next to the height tape. Should the radio-altimeter system fail, the main display is immediately shuttered, because altimeter failure of course causes an automatic changeover to the stand-by system. On the left of the central display is a group of three magnetic- shutter indicators showing the status of the two autopilots and the throttle system. With all working, the symbols "1 T 2" are visible. If either autopilot fails, the appropriate number turns into a striped pattern on both displays and the affected display is shuttered. The same occurs with the throttle symbol but, in addition, the T and striped pattern will oscillate if airspeed deviates by more than 4kt from the preset datum. Rate of oscillation increases if the error becomes larger. Thus the pilot has an attention-getting warning of malfunction prior to complete failure. The magnetic indicators are of a new type designed by Elliotts to incorporate electrical feed-back of indicated position by an in dependent electrical channel. The whole display incorporates input/ output comparison circuitry for self-monitoring. Detail design of mechanics and circuitry is now well under way and it is expected that the associated amplifier for each display will be enclosed in a long § ATR case. Various features of the display are covered by patent applications. Helicopter Flight System AFTER more than a year of development and flight trials in Whirlwinds, both at RAE and the BEA Helicopter Experi mental Unit at Gatwick, Ferranti at Bracknell, Berks, have reached an advanced stage in development of their helicopter flight director and autopilot system. Work with the FHS1, the development background of which was described in Flight for February 24, 1961, has now led to the FHS2A, which makes controlled maneuvering on instruments in a unstabilized helicopter possible at well below minimum-power speed. The associated computer can also be used to control autopilot servos, and systems of varying degrees of complexity could now be offered for production appli cations. The first FHS2A should fly this year. Principal indicators are the director horizon and compass indicator, the latter having two roller-blinds to provide a variety of course director displays. Normal Ferranti remote vertical and directional gyros provide heading and attitude references. Kollsman airspeed indicator and altimeter and a Ferranti lnertial Lead Vertical Speed Indicator, fitted with Synchrotel pick-offs, serve both as panel instruments and as appropriate inputs to the com puter. ILS, Tacan, VOR and other radio aids can be fed to the computer as required by a customer. Ferranti claim that the system is light and simple and facilitates all-weather operation for varying types of helicopter mission. The director horizon presentation has been simplified by com parison with earlier prototypes, though it is still of 5in diameter. An ingenious new feature, subject of a patent application, is the progressive shading of the sky-plate, which remains fixed in the pitch axis and only moves in the roll sense. A white horizon bar traversing the face of the plate gives the optical illusion that the area is clearly divided between light above the bar and dark below it, although the gradation of shading remains unchanged. The complete horizon bar and skyplate rotate together to show roll angles. Two fixed rings, one indicating 2° of pitch attitude and the other 10°, provide quantitative pitch-attitude indications. The two strong vertical lines in the accompanying illustration are in fact the slots for the horizon-bar supports and are not so prominent in the instrument itself. A conventional director dot is suspended on fine cross-wires and manoeuvred to indicate required control- position adjustments to the pilot. For helicopter flying it has been established that control movement, rather than attitude adjustment, are the correct demands to make of the pilot. The dot is a compen sated system, so that as soon as the pilot applies the correct control response, the dot returns to centre, whether or not the aircraft has yet assumed the appropriate attitude or reached the required flight path centre. The additional scales beside and beneath the attitude dial are re spectively a compensated collective-pitch director for maintaining heights or rates of descent with collective lever, and a plain yaw indicator. The latter could have a compass heading function in certain hover or very low-speed applications. The large screw-heads visible beside the central dial are lamp housings which, with appropriate lenses, provide lighting for night flying. They are accessible from the front of the instrument. The compass display follows now-standard practice in having a bearing ring and fixed lubber mark, together with a selected heading mark, surrounding the roller-blind displays. These are selected ferranti FHS2A director horizon Flight system control panel Compass display in approach-beam mode
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