General
The TEST switch on the front panel of the transponder starts a test of the ATC system. During test, the transponder BITE circuits do this:
*
A test for normal operation
*
Memory tests
*
A simulated interrogation test of the receiver circuits
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A test of the antenna impedance
*
A test of the TCAS interface
*
A check for valid control and altitude inputs.
Test from the Front Panel
Push and hold the test switch to and all front panel light emitting diode (LED) status indicators come on for three seconds. Then all the LEDs go off for two seconds. Continue to hold the test switch to see the applicable LEDs come on to show the condition of the ATC/Mode S transponder system.
These are the LED status indicators and their related conditions:
*
TPR green, if there are no LRU failures
*
TPR red, if there is an LRU failure
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ALT, if the altitude input from the AIMS cabinets fail
*
DATA IN, if the transponder input fails
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TOP, if the top antenna fails
*
BOT, if bottom antenna fails
*
TCAS, if the interface with TCAS fails
*
MAINTENANCE, not used
* RESERVED(2), not used.
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 ATC/mode S transponder. You must do all tests for the ATC/mode S transponder 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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ATC/MODE S TRANSPONDER SYSTEM -SELF-TEST
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ATC/MODE S TRANSPONDER SYSTEM -GROUND TESTS
General
You can do a system test of the ATC/Mode S transponder system from the MAT.
System Test
There is a system test for the left ATC/Mode S transponder system and the right ATC/Mode S transponder system.
The system test for the ATC/Mode S transponder system does a check of these functions:
*
Transponder for correct operation
*
Transponder panel for correct control data
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Antennas for correct impedance
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TCAS interface for valid inputs
*
Altitude input for correct altitude data.
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ATC/MODE S TRANSPONDER SYSTEM -GROUND TESTS
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777 AIRCRAFT MAINTENANCE MANUAL
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DISTANCE MEASUREMENT EQUIPMENT SYSTEM -INTRODUCTION
Purpose
The distance measuring equipment (DME) system supplies slant range (line of sight) distance between the airplane and the ground station.
The DME system supplies station audio and identifier signals to the flight interphone speakers and headsets.
Abbreviations and Acronyms
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ACP -audio control panel
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AIMS -airplane information management system
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ALTN -alternate
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ARINC -Aeronautical Radio, Incorporated
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ATE -automatic test equipment
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auto -automatic
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BITE -built-in test equipment
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CDU -control display unit
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CMCF -central maintenance computing function
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CMCS -central maintenance computing system
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DME -distance measurement equipment
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EFIS -electronic flight instrument system
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FMCF -flight management computing function
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LED -light emitting diode
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MHz -megahertz
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NCD -no computed data
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RF -radio frequency
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DISTANCE MEASUREMENT EQUIPMENT SYSTEM -INTRODUCTION
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DME SYSTEM -GENERAL DESCRIPTION
General
The DME system has two interrogators and two antennas.
The DME interrogator transmits a signal to DME ground stations. The ground stations send a reply signal back to the interrogator. The interrogator measures the time between the transmit signal and the reply signal and calculates distance to the station.
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