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Aviation History
1949
1949 - 1419.PDF
AUGUST I8TH, 1949 FLIGHT 183 The Zero Reader panel. (Left to right) Selector control switch, cross-pointer indicator and heading selector. cordings taken more recently indicate that a pilot flying manually and aided by the Zero Reader is able to attain much more nearly the performance of the modern gyro- pilot. Various reproductions of I.L.S. localizer flight re- cordings are on the opposite page. The very incon- sistency of consecutive recordings made in smooth air by a most proficient pilot using the conventional crossed- pointer meter gives some indication of the problem to be faced to achieve all-weather operation. What the Zero Reader was intended to, and does in fact, achieve, is the elimination of the complicated mental process required of a pilot in absorbing continuously changing indications from five separate instruments—artificial horizon, directional gyro, magnetic compass, sensitive altimeter and approach indicator—and converting the information into the requi- site control movements. According to the makers, the use of the Zero Readerby experienced pilots will permit further advances in the art of all-weather operation. An important point affectingthe introduction and general acceptance of automatic approaches is that pilots have found that, should theyhave cause to take over manually during an automatic approach, they can, with the aid of the Zero Reader, doso quickly and confidently without any need for an over- shoot OJ second attempt. Moreover, that period of apilot's training which is at present necessary to enable him to learn to convert bank, pitch, compass heading,altitude and other readings into terms, of control move- ments may be eliminated. The Sperry company believes that all-weather operation must place the stabilizing gyropilot on an equal footing with the airframe and power plant if future plans for air- traffic control are to be realized. The Zero Reader remains FLYING "ZERO" an independent unit but supplements the gyropilot by per-mitting efficient manual flying. Two good reasons for the Zero Reader remaining an independent unit rather thanone dependent upon the pitch, bank, altitude and compass signals from the gyropilot are that as a manual stand-byfor the gyropilot it is a reserve, and should not therefore use the same source of signal information, and secondly,that the instrument may be required for installation in an aircraft that has no gyropilot. The flight panel for the Zero Reader carries the crossed-pointer indicator, the heading selector or Gyrosyn com- pass (taking the place of magnetic compass and directionalgyro) and the selector switch (see illustration). Operation of the Indicator The crossed-pointer indicator has its two needles mutu- ally perpendicular. Deflection of the vertical pointer is controlled by the sum of bank, stabilized heading and localizer signals. FuD-scale deflection is equal ix> maximum localizer signal of 30-deg heading departure or 30-deg roll displacement. The sum of heading and localizer is limited so that a predetermined maximum angle of bank—20 deg when I used the instrument—will always cancel it. The horizontal pointer is controlled by the sum of pitch and altitude. Limitations are again in force to prevent the maxi- mum pitch angle from being exceeded. "Off" flags show at 3 and 6 o'clock when the instrument is not functioning. Other units, in particular the heading selector and selector switch, are described by the makers with com- mendable clarity as follows: "The heading selector con- sists of an azimuth repeater driving the pointer, and a concentric heading selector synchro, the rotor of which is fixed to the parallel-line course setter. This, in turn, is o T BEIOW BELOW REFERENCE ALTITUDE GLIDE PATH The three conditions which will cause up and down movement of the pointer. * 5 Relationship of yaw and bank and radio signal when steering zero. Yaw signal plus bank signal always equal radio track signal. Hunting and overshooting are avoided. Three conditions which will cause thepointer to indicate steer right or left.
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