1. Field of the Invention
The invention relates to altitude, speed and direction sensing and display apparatus primarily for light aircraft.
2. Background of the Invention
While the present invention is generally directed to sensing and displaying altitude, speed and direction in a digital form, a principal aspect of the invention is that of providing an improved means for displaying direction in digital form on the artificial horizon instrument as found in light aircraft.
The pilot of a conventional light aircraft is required to scan a multitude of instruments in order to be continuously aware of the altitude, speed and direction of the aircraft as well as its relation to the horizon. Vertigo has been known to be induced in these circumstances. A principle object of the present invention thus becomes that of consolidating the display of altitude, speed and direction in digital form on the face of the artificial horizon instrument so that the pilot has effectively only one instrument to scan and one location to observe particularly when critical weather conditions are being encountered. Since another primary object of the invention is that of providing an improved compass for light aircraft which allows the directional sensing unit to be remotely located and the directional signal to be sent by wire to a digital display on the artificial horizon instrument, reference will next be made to certain aspects of the prior art related to compasses.
In the conventional light aircraft a wet compass is used in conjunction with a directional gyro that is either vacuum or electrically operated. When the standard wet compass is used as the sensing unit an associated remote indicating compass is employed to display direction. However, the traditional wet compass has the disadvantage of tending to wobble and give inaccurate readings when the aircraft makes a turn. A further object of the invention thus becomes that of replacing the wet compass system with more reliable instrumentation as well as with instrumentation which is more accessible to the pilot.
A recent development in both the automobile and marine industry is the availability of a solid state compass. For example, a solid state electronic compass for automobile use is made by Zemco, Inc. of Taiwan as Model DE 700. A solid state compass for marine use is also available. In addition, there is also now available a solid state compass having a flux gate sensor with a digital display of direction for use by campers and hikers. Such a compass is made by Nautech, Ltd, Anchorage Park, Portsmouth, Hampshire, England.
While the described available automobile, marine and hiking solid state compasses provide a means for producing a digital display of direction, none of such compasses are useful for indicating aircraft direction since none of such compasses are capable of adapting to coordinated turns as encountered in aircraft flying. While flux gate sensors have been mounted on gimbals for marine applications, a gimbal support, unlike a gyroscope, is unable to maintain itself on a perfect axis parallel to the ground as happens with a gyroscope and as is required for aircraft operation. Further, none of such instruments are easily calibrated for aircraft use and none are immediately adapted to provide a digital display on or in an aircraft instrument panel. Gimbal supports also introduce acceleration and deceleration errors. The present invention on the other hand recognizes the need for utilizing modern solid state compass technology for light aircraft navigation.
In the relatively complex and expensive inertial navigation system used for large aircraft, a digital readout is obtained. Such digital readout may be obtained for air speed, altitude and direction. However, for light aircraft, digital readouts of air speed, altitude and direction are generally not available and it has not been previously known to provide a digital readout of the air speed, altitude and direction, and particularly direction, on the face of the artificial horizon or altitude instrument which is the primary instrument for use when flying under instrument flying conditions in light aircraft since it gives a visual indication of the relation of the aircraft to the horizon. The achieving of this type instrumentation thus becomes an object of the invention.