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Ground guidance system for airplanes

  • US 5,027,114 A
  • Filed: 08/15/1988
  • Issued: 06/25/1991
  • Est. Priority Date: 06/09/1987
  • Status: Expired due to Fees
First Claim
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1. A ground guidance system for airplanes in an airplane taxiway divided in a plurality of control sections, which comprises a plurality of loop coils in which the side parallel to the direction of advance of airplanes has a length larger than the length of an automobile but smaller than the length of an airplane and which are arranged in the direction of advance of airplanes in the control sections at intervals smaller than the length of an airplane, a plurality of airplane-detecting means arranged for the respective loop coils to generate detection outputs indicating the presence or absence of an airplane based on changes of self-inductances of the corresponding loop coils, display means for displaying admission of advance or inhibition of advance in the control sections for an airplane, and control means of controlling said display means based on detection outputs of a plurality of said airplane-detecting means,wherein the airplane-detecting means is constructed so that a high-level output is generated at the time of non-detection of an airplane and a low-level output is generated at the time of detection of an airplane, and at the time of a failure, the output errs to a voltage corresponding to said low-level output at the time of detection of an airplane,said airplane-detecting means comprising a high-frequency signal generator, a bridge circuit including three resistors and a resonance circuit consisting of one said loop coil and a capacitor, which becomes substantially resonant with the output frequency of the high-frequency signal generator, an alternating current amplifier for amplifying the output of the bridge circuit, a wave-detecting circuit for detecting an envelope of the amplified output of the alternating current amplifier, a window comparator having such a window characteristic that the output signal of the wave-detecting circuit is received as the input signal, the output level of the wave-detecting circuit obtained when an airplane is not present in the taxiway is within the window and the output level of the wave-detecting circuit obtained when an airplane is present and the self-inductance of the loop coil is changed is outside the window, and generating an output when an input signal of the level within the window is put in, and a voltage multiplying rectifying circuit for rectifying the output of the window comparator.

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