TM 1-1520-238-10
Table 3-22.19. HSI Controls and Indicators
Control/Indicator
Compass Card
Function
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 he 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
HDG knob
The digital distance display in (KM) to the FLY-TO-location.
(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
NAV flag
Works with VOR. Not applicable.
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.
Change 4 3-65
TM 1-1520-238-10
Section IV. TRANSPONDER AND RADAR
3.17 TRANSPONDER RT-1295/APX-100(V)1(IFF) AND
RT-1557/APX-100(V)(IFF).
The transponder set (fig 3-26) provides automatic radar
identification of the helicopter to all suitably equipped
challenging aircraft as well as surface or ground facilities
within the operating range of the system. The
RT-1296/APX-100(V) and the RT-1557/APX-1000 receives,
decodes, and responds to the characteristic
interrogation of operational MODE 1,2,3/A, C, and 4.
Specially coded identification of position (IP) and emergency
signals may be transmitted to interrogation stations
when conditions warrant. The transceiver can be
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