Navigation

Glideslope deviation scale To/From indicator Course deviation scale Compass card Compass warning flag NAV warning flag Lubber line DC 5 2I I GS 2 NAV HDG 2 4 GS I 3 6 0 3 33 Course select knob Symbolic aircraft Course deviation bar Heading select bug Course select pointer Heading select knob Figure 16-30. Horizontal situation indicator. N OBS Figure 16-29. VOR indicator. 16-24 E S W needle is centered, the radial (magnetic course “FROM” the station) or its reciprocal (magnetic course “TO” the station) can be determined. The course deviation needle also moves to the right or left if the aircraft is flown or drifting away from the radial which is set in the course selector. By centering the needle, the course selector indicates either the course “FROM” the station or the course “TO” the station. If the flag displays a “TO,” the course shown on the course selector must be flown to the station. [Figure 16-29] If “FROM” is displayed and the course shown is followed, the aircraft is flown away from the station. Horizontal Situation Indicator The HSI is a direction indicator that uses the output from a flux valve to drive the compass card. The HSI [Figure 16-30] combines the magnetic compass with navigation signals and a glideslope. The HSI gives the pilot an indication of the location of the aircraft in relation to the chosen course or radial. In Figure 16-30, the aircraft magnetic heading displayed on the compass card under the lubber line is 184°. The course select pointer shown is set to 295°; the tail of the pointer indicates the reciprocal, 115°. The course deviation bar operates with a VOR/Localizer (VOR/LOC) or GPS navigation receiver to indicate left or right deviations from the course selected with the course select pointer; operating in the same manner, the angular movement of a conventional VOR/LOC needle indicates deviation from course. The desired course is selected by rotating the course select pointer, in relation to the compass card, by means of the course select knob. The HSI has a fixed aircraft symbol and the course deviation bar displays the aircraft’s position Course index Unreliable signal flag 3 3 relative to the selected course. The TO/FROM indicator is a 3 triangular pointer. When the indicator points to the head of the course select pointer, the arrow shows the course selected. If 6 3 0 N A TO properly intercepted and flown, the course takes the aircraft CDI needle V to the chosen facility. When the indicator points to the tail of the course, the arrow shows that the course selected, if properly intercepted and flown, takes the aircraft directly away from the chosen facility. Approximately 2 degrees 1 in th 4 e VOR mode TO/FROM2 indicator When the NAV warning flag appears, it indicates no reliable 2 signal is being received. The appearance of the HDG flag 1 indicates the compass card is not functioning properly. 1 5 2 Radio Magnetic Indicator (RMI) The RMI is a navigational aid providing aircraft magnetic OBS knob or directional gyro heading and very high frequency omnidirectional range (VOR), GPS, and automatic direction