Bearing Distance and Heading Indicator (BDHI)

A BDHI is on the right side of the pilot and RIO instrument panels, see Bearing Distance Heading Indicator (BDHI). It displays aircraft magnetic heading with navigation bearing data and range information. The controls on the compass panel set the BDHI compass card to operate in a slaved or nonslaved (FREE DG) compass mode. A fixed index marker at the 12-o’clock position indicates the magnetic heading.

Two servo-driven bearing needles show magnetic bearings to the selected UHF (ADF) and TACAN stations. The No.1 (single bar) needle receives signals from the UHF (ADF) system, the No.2 (double bar) needle receives signals from the TACAN coupler.

The No.1 needle will continue to point toward the signal source, even if the compass card is misaligned or a malfunction exists, but the bearing to the station is displayed on the indicator as a relative bearing and the top of the indicator bezel will show 000°. The No.2 needle will also continue to show the magnetic bearing to the selected station or may revert to the search mode.