Figure 1-4 BDHI

CHAPTER ONE

BASIC INSTRUMENT PROCEDURES

iii.

The BDHI displays aircraft heading and navigational bearing data, and consists

of a rotating compass card and two bearing pointers called the # 1 and # 2

needles. It also displays distance indication (DME) associated with the

TACAN.

iv.

If a malfunction occurs in the compass system or compass card, the ADF

bearing pointer (# 1 needle) will continue to point to the station, displaying

relative bearing: the direction to the NAVAID, relative to the actual (not

indicated), heading of the aircraft. In this situation, the TACAN bearing pointer

(# 2 needle) will not point to the station, but will normally continue to indicate

the correct magnetic radial from the TACAN station. The compass card is

divided into 360 with numbered headings every 30. Located around the

circumference of the compass card are fixed index marks at 45 intervals.

Aircraft magnetic heading is displayed at the top of the compass card.

Figure 1-4 BDHI

Course Indicator (ID-249)

When the course indicator is used to display TACAN information, the intended

course is set in the course selector window with the course set knob

(Figure 1-5).

ii.

The heading pointer, connected to the course set knob and the compass system,

displays aircraft heading relative to the selected course. When the aircraft

heading is the same as the course selected, the heading pointer indicates 0 (zero)

degrees of heading deviation at the top of the course indicator. The heading

deviation scales, at the top and bottom of the course indicator, are scaled in 5

increments up to 45.

iii.

The TO-FROM indicator shows whether the selected course would lead the

aircraft closer TO or further away FROM the tuned TACAN. The course

deviation indicator (CDI) bar displays the location of the selected course

relative to the location of the aircraft. Changing the heading of the aircraft until

1-16 BASIC INSTRUMENT PROCEDURES