A320 FMGC reset on ground
Dear all.
I have some questions about FMGC reset proc on ground.
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On ground:
‐ Apply external power or APU generator power
‐ Wait 2 min before resetting the FMGC circuit breakers
‐ FD 1(or 2) (OFF)
‐ Pull the C/B of the affected FMGC and reset it after 10 s.
The circuit breakers for the FMGCs are:
• AUTO FLT/FMGC 1 B2 ON 49 VU (Overhead Panel)
• AUTO FLT/FMGC 2 M17 ON 121 VU (Right Rear Maintenance Panel)
CAUTION Always wait 1 min after the "PLEASE WAIT" message
disappears from the MCDU, before engaging or
reengaging the FDs and the AP of the reset FMGC.
Note: Due to electrical transient, MANUAL FMGS RESET procedure
may be unsuccessful. If so, the flight crew may attempt the same
procedure with engines not running.
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Do we have to turn on APU even we have running engs? why?
"note" says "Due to electrical transient. What is electrical transient? Does it mean electrical source change from eng to APU or something?
Thank you in advance.