About Us

Icarus Instruments Incorporated
7000 Carroll Ave., Suite 200,
Takoma Park MD 20912
Phone: (301)891-0600 Fax: (301)891-0666

Icarus Instruments, Inc. was founded in 1987 to manufacture the AltAlert 3070 altitude alerter. The AltAlert 3070 was the first low-cost, full- functioned altitude alerter available for general aviation aircraft. The 3070 carries both an STC and a PMA.

Steve Silverman

The key design criteria for the 3070 was to minimize the pilot workload when a new altitude is assigned. Two concentric knobs were used to set in a new Target altitude, one knob for 1,000's of feet and the other knob for 100's of feet. Since setting in the current barometric pressure is essential for good accuracy, this function was also achieved with minimal knob twisting. Over 800 of the 3070's were delivered.

The 3070 has a standard 2.25" round instrument form factor. Some aircraft could not accommodate the AltAlert due to panel space limitations, so the AltAlert 6200 was developed. This model has three pieces, a small display module, a knob module, and a remote-mounted computer module. The display is sufficiently small that it can be mounted in a very small area on the panel. Crowded panels such as Cessna 210's and 340's, Aerostars, and Beech Barons were especially suitable for the 6200. The knob usage on the 6200 is identical to the 3070. Over 200 of the 6200's were delivered.

In 1991 when the first panel mounted aviation GPS receivers were delivered, the GPS constellation included about 12 useful satellites. This resulted in less than 24 hours/day coverage, which severely hampered the usefulness of GPS. However, by telling the GPS receiver how high it was, only two satellites were necessary to establish a reliable location. Since entering altitude manually into a GPS receiver was hardly convenient, Icarus developed the 3000U altitude serializer. This small device converts the standard Grey code that the altitude encoder produces to an ASCII serial string that is fed into the GPS receiver.

When the whole group of 24 satellites was in place, the need for the Serialzier decreased until the FAA approved GPS non-precision approaches. The TSO required a calculation called RAIM to determine if the geometry of the satellites would be adequate to provide reliable position data when the approach was in progress. The availability of the aircraft's altitude to these calculations would fill in for a missing or poorly positioned satellite. Thus all GPS approach approved receivers must have altitude input. This can come from the Grey code lines directly on receivers that have this capability or from a serial connection being fed by the Serializer.

Many very popular GPS receivers use the Serializer to provide altitude data for the RAIM calculation and all VNAV displays. Since GPS altitude is based on a center of the earth model, it does not do a very good job of knowing your actual height based on the barometric pressure. A real pressure altitude input corrected for local barometric pressure does a much better job.

In 1997, Icarus introduced the NavAlert, the smallest piece of avionics ever built. Only one inch in diameter, the NavAlert provides a remote display of important GPS data such as distance to waypoint, time to waypoint, waypoint ID, ground speed, ground track, and track angle error.

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