777 AIRCRAFT MAINTENANCE MANUAL
VOR -ND VOR INVALID DISPLAYS
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VOR -ND VOR TEST DISPLAYS
General
When you do a test of the VOR/MB receiver, the receiver starts a test sequence that lasts approximately 15 to 20 seconds. During the test sequence, the receiver output changes to these conditions:
*
Invalid data for the first three seconds
*
NCD for two seconds
*
Test display for approximately ten seconds.
Invalid Data Test Display
For the first three seconds of the test, the receiver output goes invalid. These are the ND display changes:
*
Remove the selected course arrow
*
Remove the deviation bar and scale
*
Remove the to/from pointer and indication
*
Show the amber VOR flag.
NCD Data Test Display
After the first three seconds of invalid data, the receiver output goes to an NCD condition for two seconds. These are the ND display changes:
*
Remove the deviation bar
*
Remove the to/from pointer and indication
*
Show the selected course arrow
*
Show the deviation scale.
VOR Test Display
After the NCD condition, the receiver shows a valid test display for approximately ten seconds. These are the VOR test displays:
*
Selected course arrow points to 0 degrees on the compass
*
The deviation bar is centered if 000 is the selected course during the test
*
The to/from pointer and indication show a FROM indication.
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777 AIRCRAFT MAINTENANCE MANUAL
VOR -ND VOR TEST DISPLAYS
EFFECTIVITY BEJ ALL 34-51-00
Page 41
D633W101-BEJ Jan 05/2002
VOR -VOR/MB RECEIVER FRONT PANEL TEST DISPLAYS
General
When you do a test of the VOR/MB receiver, you can monitor the receiver test sequence on the NDs and on the VOR/MB receiver front panel LED status lights.
Test Sequence
During the receiver test sequence the LED test displays are:
*
All LEDs come on for three seconds
*
All LEDs go out for three seconds
*
The applicable LED comes on to show a normal or a fault condition.
The green LRU status LED comes on if the receiver test is good. The red LRU status LED comes on if the receiver test fails.
The red control fail LED comes on if the frequency input to the VOR/MB receiver is bad.
The applicable lED stays on until you release the test switch.
Training Information Point
The maintenance manual and the fault isolation manual do not have a task for the line maintenance technician to do a test from the front panel of the VOR/MB receiver. You must do all tests for the VOR/MB receiver from the MAT or a PMAT.
Many LRUs on the 777 are compatible with other model airplanes that do not have a central maintenance computing system (CMCS). For that reason these LRUs have a front panel test feature.
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VOR -VOR/MB RECEIVER FRONT PANEL TEST DISPLAYS
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VOR -GROUND TEST
General
You can test the VOR/MB system from the MAT. These are the tests that are available from the operational test selection on the MAT:
*
Left VOR M/B System
*
Right VOR System.
Operational Test
The operational test for the left VOR M/B system does a test of:
*
Normal operation of the VOR receiver
*
Normal operation of the marker beacon receiver.
The operational test for the right VOR system does a test for normal operation of the right VOR receiver.
The test is the same from the MAT or the receiver front panel test switch. The only difference is that the test from the MAT does not do a lamp test of the receiver front panel LEDs.
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777 AIRCRAFT MAINTENANCE MANUAL
VOR -GROUND TEST
EFFECTIVITY BEJ ALL 34-51-00
Page 45
D633W101-BEJ Jan 05/2002
AIR TRAFFIC CONTROL/MODE S TRANSPONDER SYSTEM
General
The air traffic control (ATC) ground stations interrogate the airborne ATC/Mode S transponder system. The ATC/Mode S transponder replies to the interrogations in the form of coded information that the ground station uses.
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