Threat symbols (except for U) shown on indi-
cator illustrations are for illustration purposes
only. Actual threat symbols are classified.
The indicator displays threat symbols corresponding
to threat signals detected and identified by the system.
Threat relative position from the helicopter is shown on the
indicator. Symbol position relative to the center of the indica-
tor shows the threats lethality. The highest priority threats
(most lethal) are shown nearest the center. The 12 outer
edge markings on the indicator graticule represent clock
positions relative to helicopter heading. The system displays
a maximum of seven threat symbols. If the number of
threats in the environment exceeds the number the system
can display, only the seven highest priority threats will be
displayed. If a detected threat cannot be identified as a
specific threat type, it is displayed as an unknown (symbol
U). Search radars and fire control radars operating in search
mode are displayed as strobes at the edge of the indicator.
The position of the strobe on the display represents the
relative bearing of the search radar from the helicopter. New
threats appear in boldface on the display. Threats that drop-
out of the environment are ghosted on the display for 10
seconds before being dropped. A ghosted symbol appears
as though drawn with a dotted line.
Threats are announced by voice messages over
the helicopter ICS. Either of the two voice message for-
mats can be selected using page 2 of the CDU ASE
control layer. RWR AUDIO 1 or normal (full message
format) selects full audio. RWR AUDIO 2 or terse (short-
ened message format) provides shorter audio messages
and reduces the audio clutter in dense signal environ-
ments. Both modes provide specific threat type or threat
position voice messages.
When dense signal environments cause the sys-
tem to operate in a degraded (less sensitive) mode, the
system informs the operator by flashing the plus (+) sym-
bol on the RSDS indicator and the voice message
Threat Detection Degraded will be heard over the ICS.
When the system sensitivity returns to normal, the plus
(+) symbol in the center of the RSDS indicator stops
flashing and the voice message Threat Detection Re-
stored will be heard over the ICS.
The RSDS, LDS, and MWS all execute periodic
built-in-test (PBIT) routines during normal operation to
verify operational status with the results of these tests
being reported to the digital processor. Failures of PBIT for
these three systems are indicated by the presence of an F
replacing the plus (+) symbol in the center of the RSDS
indicator. The F informs the operator that one or more of
the systems has failed at least some portion of their respec-
tive PBIT routines. This prompts the operator to perform
initiated built-in-test (IBIT) to determine what system(s) has
failed and the extent of the failure(s)..
IBIT may be selected by the operator. If the RSDS
interface circuitry within either RTU fails the self-test, the
RWR TEST FAIL advisory is displayed on the MFD.
Faulty receivers are shown on the indicator as blinking
symbols and the voice message APR-39 Failure will be
heard over the ICS. If the test is good, the voice message
APR-39 Operational will be heard over the ICS. The
RWR FAIL caution is displayed if the RSDS interface
circuitry within both RTUs fails while in its normal operat-
ing state. Self-test of the laser detecting set (LDS) and
the missile warning system (MWS) are incorporated in
the RSDS self-test.
The system interfaces with the Interference
Blanker Unit (IBU) in an attempt to prevent other aircraft
systems, which operate in the same approximate fre-
quency range, from interfering with it. The lo-band portion
of the RSDS is blanked by the IBU when either the IFF
transponder system or the TACAN system is transmitting.
The hi-band portion of the system is blanked by the IBU
when the radar altimeter system, radar beacon transponder
system, multimode radar system, pulse radar jammer sys-
tem, or the CW radar jammer system is transmitting. This
blanking is accomplished to prevent the possible detection
of false threats as a result of interference induced by these
systems. Because the RSDS is a passive system, it does
not provide any input to the IBU for the potential blanking of