(6)  
Monitor or BITE circuits in the DFDAC and FDR provide status signals to alert the captain and first officer to a failure by sending a discrete signal to the three EIUs. After receiving the discrete from the DFDAC, the EIUs generate the status message FLIGHT RCDR SYS on the lower EICAS display.

 (7)  
The CMC can command the DFDAC to carry out a power-up test. The CMC transmits a Command Summary Word to the DFDAC to perform the power-up test. The results of the power-up test are sent back to the CMC. A commanded power-up test includes the following functions:

 (a)  
Check the internal health of the DFDAC and report card status.

 (b)  
Check input busses for activity and report each busses status. Bus inactivity is defined to be no GMT updates for 4 seconds.

 (c)  
Set the FDR Power Control discrete output true. The DFDAC shall read and report the status of the FDR System Status and the FDR Maintenance Flag analog input discretes before resetting the Power Control discrete false.

 (8)  
The DFDAC shall inhibit commanded power-up testing if the airplane is in the air or if one or more engines are starting or running. A BITE Test Inhibit discrete is set to indicate to the CMC that power-up testing cannot be performed.

 B. Control
 (1)  
The DFDAC receives 5 volts dc and |12 volts dc from the MAWEA power supply units. The DFDR receives 115 volt ac from AC BUS 3 through the FLT REC AC circuit breaker.

 (2)  
The DFDAC turns the FDR on by energizing a relay in the MAWEA chassis. An analog discrete output by the DFDAC is used to control a relay providing 115 volts ac to the FDR. The discrete is set true when any of the following conditions exist:

 (a)  any engine is being started
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747-400 MAINTENANCE MANUAL
 (b)  
any engine is running

 (c)  
the AIR/GND Relay is indicating air

 (d)  
a command for a Power-up Test is received from the CMC.

 (3)  The flight data recorder system can be tested using the CMC. Using any of the CDUs, select the <GROUND TEST line select key from the CMC MENU. Pressing the <GROUND TEST key will bring up the GROUND TESTS SYSTEMS menu. Scroll through the GROUND TEST SYSTEMS menu page until <31 RECORDING line is displayed. Pressing the <31 RECORDING line select key will bring up a GROUND TESTS menu. The DFDR system is tested from this GROUND TESTS menu by pressing the <FLIGHT RECORDER line select key. After the system is finished being tested, a PASS or FAIL message will be displayed. If FAIL> is displayed, the corresponding maintenance message can be accessed by pressing the FAIL> line select key.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 FAULT ISOLATION/MAINT MANUAL
FLIGHT DATA RECORDER SYSTEM
FIG.  AMM 
COMPONENT  102  QTY  ACCESS/AREA  REFERENCE 
SHT 
ACCELEROMETER - THREE AXIS, X393 2  1  751, WING LANDING GEAR WELL  31-31-03 
BEACON - UNDERWATER LOCATOR  3  1  AFT EQUIP CTR, E8, DFDR  31-31-09 
CARD - DIGITAL FLIGHT DATA ACQUISITION, 2  1  117AL, MAIN EQUIP CTR, MAWEA  31-31-06 
YMXA18  CARD FILE, M7952 
CIRCUIT BREAKER - 1  117AL, MAIN EQUIP CTR, P180 P415 
FLT RCDR AC, C775 1  180J26  * 
FLT RCDR DC, C10243 1  415L36  * 
COMPUTER - (FIM 45-10-00/101) 
L CENTRAL MAINTENANCE, M7373 
FILE - (FIM 31-51-00/101) 
MAWEA CARD, M7952 
RECORDER - DIGITAL FLIGHT DATA, B579 3  1  AFT EQUIP CTR, E8  31-31-01 
RELAY - (FIM 31-01-39/101) 
　
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