Slant range (in nautical miles) to the beacon is displayed by the digital DME (Distance Measuring Equipment) display in the top left of the instrument.

The course set by the rotary CRS control is displayed by the digital COURSE display in the top right of the instrument and also indicated by the yellow track index that registers against, and rotates with, the compass card.

The current aircraft heading is indicated by a rotating compass card registering against a fixed lubber mark at the top of the display.

The selected heading (set by the rotary HDG control) is displayed by the yellow heading index (or heading bug) that registers against, and rotates with, the compass card.

Deviation of up to 10 degrees left or right of the course (indicated by the yellow track index) is indicated by the yellow deviation bar central to the display. The deviation bar registers against a scale of dots that each represent 5 degrees of deviation.

To centralise the deviation bar, the aircraft should be flown towards the bar.

The ‘To’ and ‘From’ indicators identify which sector the aircraft is in relative to a line 90 degrees off the selected course. Therefore the ‘To’ indicator will be displayed only when the bearing is less than 90 degrees off the selected course and the ‘From’ indicator will be displayed when the bearing is greater than 90 degrees off the selected course. The ‘To’ indicator is a filled white triangle whilst the ‘From’ indicator is a white triangular outline.

Note that the indicators do not confirm that the aircraft is heading towards or away from the VOR beacon as the logic disregards aircraft heading.

When HSI power is deselected a red and white warning flag will appear. The compass card will continue to rotate.