A320 CFDS

[sarius]

Hey guys!

Got a couple of questions regarding the CFDS.

I know that there is a procedure to access the CFDS menu when the aircraft is on jacks (31-32-00-869-003). Is this because the CFDS cannot be accessed when the aircraft is in flight config? Will opening the two LGCIU CBs (1GA & 2GA) simulate a flight config?

During an engine ground run (test no. 8 - vibration survey), there is a procedure for the acquisition of the unbalance data which allows for the printing of PFR (77-32-34-869-010).

One of the subtasks (G) calls for the CFDS to be held in Flight mode for more than 30s before opening and closing the four CBs - FWCs (3WW & 2WW) & CFDIUs (2TW & 8TW).

How is the CFDS held in flight Mode? Is it automatically in Flight Mode after starting both engines? Can the CFDS be accessed when both engines are running?

Why is there a need to enter the flight number for the printing of PFR? Does it have anything to do with the memory zones of the different types of systems?

[Fargoo]

Pulling those 4 c/b's resets the flight number so that you can enter the CFDS system report/test menus.

It's normal on a ground run to enter a flight number to allow the CFDS to produce a PFR, however if you've done this you can't access the Engine Vibration menus hence the 4 mentioned c/b's.

[Fargoo]

p.s. To be clear - if you don't enter a flight number in the INIT page then YES you can access the CFDS menus with both engines running!

[flame_bringer]

*Will opening the two LGCIU CBs (1GA & 2GA) simulate a flight config?*
Yes opening these cbs will simulate an in flight configuration because the ground input thats supplied from the LGCIUs to the CFDS and other computers BITES which informs them that the nose gear is compressed will no longer be there.

The reason this procedure is required in flight is because the CFDS menu in flight gets changed and the BITES of the computers go into the normal mode where the faults get sent to the CFDS such that it generates the PFR, last leg report and last leg ECAM report, You will now have current leg report and current leg ECAM report and no more menu mode aka system reports and test.
When an engine run is performed with the flight number entered before the engine run then the CFDS (as well as other computers BITES) goes into normal mode 3 minutes after the engine run and starts a new PFR hence CFDS access gets limited however as fargoo said if a flight number is not entered prior to the engine run whilst the aircraft is on ground then the CFDS remains in ground mode untill the aircraft accelerates up to 80 knotes hence you will still have menu mode.
And again as fargoo said reseting these CBs resets the flight number and brings the CFDS back to the ground mode.
To be more accurate all of the BITES will enter the normal mode after an engine run with a flight number entered before hand except the type 2 BITES which only enter the normal mode if the aircraft is in flight configuration.

[sarius]

great info guys!

you've just simplified what I've been trying to digest from the AMM D/O for CFDS. And my B1 course notes just don't give enough details regarding this procedure.

So basically these are the 2 scenarios:

After 1st Eng start (+ 3 min), before 80 kts, no Flight number entered
- CFDS remains in Menu mode (aka Ground mode)
- SYS REPORT/TEST can be accessed
- PFR cannot be printed

Flight number entered before 1st Eng start
- CFDS goes into Normal mode (aka Flight mode)
- SYS REPORT/TEST cannot be accessed
- PFR can be printed

[flame_bringer]

Its incorrect to say PFR cannot be printed its just that there wont be any PFR available for a new leg because a new leg was not initiated in the First case but you can still print the PFR of the last leg.
And in the second case you will have a new PFR generated.

[sarius]

ah... ok. thanks :)