figure 4

Patent No. 5,610,600


Issued: March 11, 1997

Inventor: Robert H. Koenig, 3651 Coats Road, Burdett, New York 14818


The inventor's previous patents, "Radio Receiver Operational Checking Method and System including Reactive Coupling", U.S. Patent 5,241,698, and "Radio Receiver Noise Squelching and Operational Indicating Alarm", U.S. Patent 4,996,717, addressed the problem of checking the operation of radio communications receivers. This invention relates to the checking of navigation equipment in a similar manner.

The invention presents an instrument verification system which causes the instrument needles to "bob" periodically - a sharp deviation from center. If desired, the flags can also be "bobbed", verifying their operation as well. The pilot can easily distinguish the momentary deflection of the needles from the more gradual changes caused by deviation from true course, and is assured that the centered needles mean perfect flying and not instrument failure.

Several methods are described which achieve the navigation instrument testing by bobbing the needles and dipping the flags. The preferred method operates into the antenna input of the navigation (NAV) receiver using special T-couplers. This has the advantage of not requiring internal connections to the instrument, and testing the entire system, but requires more parts.

An alternate embodiment capacitively induces the bobbing voltage pulses onto internal control points to test the needle mechanism and the solid state drivers.

A third embodiment inductively couples test pulses onto wires to the needle and flag mechanisms by means of transformers where the needle-moving current flows through the secondary windings, and pulses imposed on the primaries cause the needle and flag deviations. A stuck needle or flag, or an open connection, is indicated by the lack of the periodic bobbing or dipping.

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