Change 3 3-77
doppler (DD) and time difference of arrival (TDOA) infor-
mation received at a ground facility from the aircraft.
CHALS receivers aboard the aircraft will receive and digi-
tize emitter signals. The data will be transmitted over the
data link to the GR/CS integrated processing facility
(IPF). There, CHALS processors will perform the re-
quired computations to produce accurate emitter loca-
tions. The precise navigation required is provided by the
inertial navigation system (INS) and the global position-
ing system (GPS). GPS also provides the primary means
of time synchronizing the CHALS receivers (signal condi-
tioners or SCs) aboard the aircraft. A backup for the GPS
is provided by the data link. The resultant emitter reports
will be sent to GR/CS by CHALS.
b. GPS (and INS) movement. The accurate and time-
ly navigation (position and velocity) is provided by inte-
grating an INS with a GPS, and integrating both (through
a series of intermediaries) with a CHALS ground based
navigation processor (NP). The SC, data link, and
CHALS HSSP (high speed signal processor) form the
communication link. The critical airborne interfaces for
CHALS navigation and time synchronization include the
(1) INS to GPS and CHALS:
(2) GPS to CHALS:
Time mark pulse (time synchronization)
Navigation data block (position, velocity, and time)
Error state vector data block (9 element ESV, time)
TM/covariance data block (time, TM time, covarian-
Status data block (status including DOPs and FOMN)
RADAR AND TRANSPONDER
3-30. RADAR AND TRANSPONDER EQUIPMENT
The radar and transponder group consists of a weath-
er radar, lightning sensor system, transponder, and en-
coding altimeter indicator. The transponder and radar
group includes an identification, position, emergency
tracking system, and a radar and lightning sensor system
to locate potentially dangerous weather areas.
3-31. WEATHER RADAR SYSTEM (WC-650).
The weather radar system is a light weight, X-band
digital radar with alphanumerics designed for weather
detection and analysis and ground mapping. The radar
system is controlled from the radar control panel (fig.
3-29), located on the pedestal extension (fig. 2-12). Ra-
dar information is displayed on the pilots and copilots
The weather radar may display false echoes and
spikes on all ranges when the VHF-FM (SINC-
GARS) transceiver is transmitting.
The primary purpose of the system is to detect storms
along the flight path and give the pilot a color visual indi-
cation of there rainfall intensity. After proper evaluation,
the pilot can chart a course to avoid these storm areas.
Figure 3-30 depicts a typical EFIS weather test pat-
tern (120 degree scan).
The system performs only the functions of
weather detection or ground mapping. It should
not be used nor relied upon for proximity warning
or anti-collision protection.
Output power is radiated during test mode.
If the radar system is to be operated in any mode
other than standby while the aircraft is on the
ground: Direct the nose of the aircraft so that the
antenna scan sector is free of large metallic ob-
jects such as hangars or other aircraft for a dis-
tance of 100 feet (30 meters).
Do not operate during refueling of aircraft or de-
fueling operation within 100 feet (30 meters).
Do no operate if personnel are standing too
close to the 270-degree forward sector of the
aircraft (fig. 3-31).
Operating personnel should be familiar with FAA