18-3.3 DOPPLER/GPS NAVIGATION SYSTEM OPERATIONAL CHECK
Electrical Repairers Tool Kit,
Aircraft Electrician (2)
Electrical Power Off
Hydraulic Power Off
Doppler/GPS Navigation System Visual
Remove aircraft from overhead cover.
CHECK CIRCUIT BREAKERS
Check that DOPPLER breakers (1) on No. 1
and 2 pdp are closed.
If circuit breakers are open, close them.
Start APU. Refer to task 15-1.4.
APU ON capsule shall come on.
CHECK DGNS LIGHTING
Turn aircraft CTR CSL LTG control (2) clock-
wise and counterclockwise while checking
CDU (3) Edge lighting is illuminated and all
keyboard keys are illuminated.
Set CDU (3) MODE switch (4) to LAMP TEST.
CDU MAL LAMP and all LED segments on four-line
Enter GPS mode M. Verify that MAL LAMP
display are illuminated. If CDU MAL LAMP and all LED
and ail LED segments on four-line display are
segments are not illuminated go to task
Press CDU (3) DIM (5) pushbutton several
times, the BRT (6) pushbutton several times.
CDU (3) panel Edge light and all keyboard lights shall
vary with the changing setting of the aircraft dimmer
control (2). If CDU (3) panel Edge and keyboard lights
are not visible or intensity level does not vary with air-
craft dimmer control (2) go to task 18-3.4
The LED display will grow dimmer then brighten. If the
intensity of the LED display does not vary replace
Set CDU (3) MODE switch (4) to TEST.
After Doppler and/or GPS self tests have been com-
pleted (approximately 15 seconds for Doppler, up to 2
minutes for GPS) one of the following indications will
be observed in left and right displays. If the display is
not GO ALL go to task 18-3.6.
In the event TEST mode display is not GO ALL the system should be recycled through
OFF to verify that the failure is not momentary one.
C, R, S or H fol-
lowed by a nu-
A failure has occurred in the Computer Display Unit or the Signal Data Con-
verter Power Supply. The operator should not use the System.
GPS failure code
GPS has failed but operator can use Doppler to perform all navigation.
Doppler has failed. GPS is still performing self test.
Doppler has failed but operator can use GPS to perform all code navigation.
Doppler has completed Built In Test (BIT) and is operating satisfactorily,
GPS is still performing BIT (GPS has a 2 minute BIT cycle maximum). Note
that a rotating bar in the display indicates that the GPS is still performing self
The entire system has completed BIT and is operating satisfactorily.
Pitch or Roll data is missing or exceeds 90 degrees. In this case, pitch and
roll in the computer are both set to zero and navigation in the Doppler mode
continues with degraded operation. Problem may be in the vertical gyro or
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18-70 Change 19