777 AMM 飞机维护手册 导航 Navigation 1(33)

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During the test, a self-test frequency generator gives a 75 MHz RF signal that has 400 Hz, 1300 Hz, and 3000 Hz audio signals. The bandpass filters detect the audio signals and send them to the audio amplifier. The audio amplifier sends the audio signals to the AMU. The AMU sends the audio signals to the flight interphone speakers and headsets in the flight deck.
The maintenance access terminal sends a test request signal to the left AIMS CMCF. The left AIMS CMCF sends the test request signal to the BITE circuits in the VOR/MB receiver. The results of the test go to the CMCF. The marker beacon audio tones come on in the flight deck. The LEDs do not come on during the test.
The BITE circuits monitor the status of the output data of the VOR/MB receiver.
Air/Ground Discrete
The VOR/MB receiver gets an air/ground discrete signal from the air/ground relay. The VOR/MB receiver uses this signal to prevent a test in the air.
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MARKER BEACON SYSTEM -FUNCTIONAL DESCRIPTION
An internal nonvolatile fault memory (NVM) in the BITE circuits uses the air/ground discrete signal. The NVM uses this signal as an alternate method to define flight legs if the AIMS CMCF fails.
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MARKER BEACON SYSTEM -FUNCTIONAL DESCRIPTION

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MARKER BEACON SYSTEM -TEST

General
When you do a test of the marker beacon system, you do a test of the left VOR receiver at the same time.
Operation
To do a test of the left VOR/marker beacon (VOR/MB) receiver:
*
Push and hold the test switch on the front panel of the left VOR/marker beacon (VOR/MB) receiver

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The front panel light emitting diodes (LEDs) come on for 3 seconds to show they are good

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The LEDs go out for 2 seconds

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The applicable LEDs come on to show a normal (green), or a fault (red) condition

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The lEDs stay on until you release the test switch.

The primary flight display (PFD) shows FT (functional test) during a marker beacon test.
You must select marker beacon audio on at least one of the audio control panels (ACPs) to hear the audio tones. All the marker beacon audio tones come on in the flight deck during the test. The audio tones come on continuously and all at the same time.
Maintenance Access Terminal
You can also use the maintenance access terminal (MAT) to do a test of the marker beacon system. The LEDs on the VOR/MB receiver do not come on when you do a marker beacon test from the MAT. Other test indications are the same.
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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777 AIRCRAFT MAINTENANCE MANUAL

MARKER BEACON SYSTEM -TEST

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MARKER BEACON SYSTEM -GROUND TEST

General
You can do a left VOR/MB system test from the MAT.
Left VOR M/B System Test
When you do a test of the left VOR system, you also do a test of the marker beacon system.
This test verifies the operation of the marker beacon system. You will see the letters FT on the PFD during the test. The front panel LEDs on the left VOR/MB receiver will not come on during this test.
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777 AIRCRAFT MAINTENANCE MANUAL

MARKER BEACON SYSTEM -GROUND TEST

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777 AIRCRAFT MAINTENANCE MANUAL

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RADIO ALTIMETER SYSTEM -INTRODUCTION

General
The radio altimeter (RA) system measures the distance from the airplane to the ground. The radio altitude shows in the flight deck.
The system has a range of -20 to 2500 feet. The flight crew and other airplane systems use radio altitude during approach and landing.
Abbreviations and Acronyms
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AFDC -autopilot flight director computer
　
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