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Radio Magnetic Indicator (RMI)

in Navigation

The RMI [Figure 15-31] is a navigational aid providing aircraft magnetic or directional gyro heading and very high frequency omnidirectional range (VOR), GPS, and automatic direction finder (ADF) bearing information. Remote indicating compasses were developed to compensate for errors in and limitations of older types of heading indicators.

Figure 15-31. Radio magnetic indicator.

Figure 15-31. Radio magnetic indicator.

The remote compass transmitter is a separate unit usually mounted in a wingtip to eliminate the possibility of magnetic interference. The RMI consists of a compass card, a heading index, two bearing pointers, and pointer function switches. The two pointers are driven by any two combinations of a GPS, an ADF, and/or a VOR. The pilot has the ability to select the navigation aid to be indicated. The pointer indicates course to selected NAVAID or waypoint. In Figure 15-31 the green pointer is indicating the station tuned on the ADF. The yellow pointer is indicating the course to a VOR of GPS waypoint. Note that there is no requirement for a pilot to select course with the RMI, but only the NAVAID is to be indicated.

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