TM 1-1520-238-10
Change 4
3-65
Table 3-22.19.
HSI Controls and Indicators
Control/Indicator
Function
Compass Card
The compass card is a 360-degree scale that turns to display heading data obtained from the
HARS. The aircraft headings are read at the upper lubber line.
Bearing pointer
No. 1
The pointer operates in conjunction with the doppler. It indicates relative bearing to the active
FLY-TO-location. The No. 1 bearing pointer ‘‘parks’’ at the 3 o’clock position when the
doppler ‘‘bearing-to-destination’’ signal is invalid.
Bearing pointer
No. 2
This pointer operates in conjunction with the ADF receiver. The pointer is read against the
compass card and indicates the magnetic bearing to the ADF station (nondirectional
beacon).
Course deviation bar
This bar indicates the lateral deviation from the desired navigation course. When the
helicopter is flying the desired navigation course, the course bar will be aligned with the
course set pointer and will be centered on the fixed aircraft symbol.
CRS knob
(CRS) knob and the course set counter operate in conjunction with the course pointer and
allow the pilot to select any of 360 courses. Once set, the course pointer will turn with the
compass card and will be centered on the upper lubber line when the helicopter is flying the
selected course, providing there is no wind to blow the helicopter off course.
KM indicator
The digital distance display in (KM) to the FLY-TO-location.
HDG knob
(HDG) knob operates in conjunction with the heading select marker and allows the pilot to
select any one of 360 headings. Seven full turns of the knob produce a 360-degrees turn of
the marker.
To-from arrow
Works with VOR. Not applicable.
NAV flag
The NAV flag, on the HSI course carriage, turns with the compass card. The flag retracts
from view when a reliable course deviation signal is available from the doppler.
HDG flag
The HDG flag retracts when a reliable heading signal is available from the HARS. During
HARS alignment, retraction of the heading flag indicates that HARS is aligned (ready-to-fly).
Distance shutter
The distance shutter (upper left corner) retracts when the ‘ ‘the distance-to-destination’’
signal from the doppler is valid.
