A320 Dual Hyd Inop Sys (braking question)

[100.above]

Hi There,

G + Y hyd failure, ecam inop systems: ALTN BRK not listed.

BRAKES: accumulator braking only.


B+Y hydraulic failure, ecam inop systems: ALTN BRK listed.

BRAKES: normal brakes and accumulator only braking as a backup.

This is ambiguous as airbus is saying that accumulator only braking is a form of alternate braking in the first case, and in the second it is saying that it is not a form of alternate braking.

Any one care to clear up the reasoning why they dont remove it from the ecam inop system screens considering ALTN BRK is still available if needed by accu only pressure in the case of a B+Y failure. Or even better put it as inop for both scenarios and treat accu only braking as another form of braking altogether.

[Cough]

I know what you are saying....but!

You should have figured out exactly what brakes you have on the wheel page prior to getting anywhere near the status page - The status merely confirms it.

The statement on one 'BRAKES: accumulator braking only' gives the game away:- Land, using 1000psi stop, shutdown and get towed in.

The other doesn't major on it as you have lots else to think about - Basically you have fully working brakes....

[mototopo]

Hi,
The reason could be using the same ECAM abbreviation "ALTN BRK" for 2 alternate braking systems:
Alternate braking with antiskid
Alternate braking without antiskid (brakes being supplied by accumulator only)
AND, depending on A/c's MSN, some other differences, given the presence of ABCU or not.

In fact going through the FCOM DSC-32-30-10 (landing gear section) you can see a description how normal and alternate braking, with or without antiskid, work.

To answer your question, I would sah that a B+Y hyd failure doesn't prevent the use of normal braking, being the main and only method of braking; even if it's still a backup, there is nothing you can do to use the accumulator, hence the alternate braking without antiskid, unless you depresurize the Green system too or switch OFF the A/SKID & N/W STRG.

With a G+Y hyd failure you lose both normal and alternate braking with antiskid; the remaining one is the accumulator, or alternate braking without antiskid; if you look at the status page (or FCOM PRO-ABN-29) it's specified you can brake with the accumulator, hence with an alternate braking without antiskid. To put it inoperative it would be a nonsense..

Just my 2 cents, hope it can help.

Ciao!
Moto

[100.above]

Thanks guys I agree with both of you.

Just strange the way they put things as technically if you switched off the antiskid & nws switch when landing with a B+Y failure if 1 in a million chance the green brakes bugged out while you were using them, if you had accumulator pressure it should work and therefore the alternate brakes are not exactly a completely inop system.

As in the case of the G + Y... ALTN BRK is not listed as inop and we are on accumulator only hehe.

Of course we would know what systems we have from reviewing the system pages as well, it is just interesting the way they put things on the ecam screens when they don't make any sense at all.

thanks guys!

[vilas]

100.above
A 320 has two independant braking systems. Normal on green and Alternate on yellow. Both are with antiskid. Accumutor is not alternate braking but a form of emergency back up. You only have seven applications and no antiskid. The landing distance required with only accumulator as brake would not be same as previous two. However in G+Y fail it would make sense to add alternate brake in inop system.

[100.above]

brakes

Vilas
A 320 has two independant braking systems. Normal on green and Alternate on yellow. Both are with antiskid. Accumutor is not alternate braking but a form of emergency back up. You only have seven applications and no antiskid. The landing distance required with only accumulator as brake would not be same as previous two. However in G+Y fail it would make sense to add alternate brake in inop system.

I Disagree with you on the above, the accumulator is a form of alternate braking as it is part of the alternate braking system.

2 Braking Systems:

• Normal Green Hyd System
• Alternate Yellow Hyd System and/or Accumulator.

4 Braking Modes:

• Normal Braking
• Alternate + Anti-Skid
• Alternate – Anti-Skid
• Alternate on Accumulator Only

It would make even more sense the other way round, if they removed it from the inop systems list in a B+Y hyd failure case, is a form of alternate braking.

Just look at the DSC 32-30-10 p1 and the diagram on p9; the ABCU is responsible for:

• Alternate Braking with A/SKID (BSCU controls the A/Skid)
• Alternate Braking without A/SKID
• Alternate Braking without A/Skid on accu only

so really they shouldn't even list it as an inop system at all!

This is really a trivial thing, however it does not make sense so it was worth discussing.

[rudderrudderrat]

Hi 100.above,

so really they shouldn't even list it as an inop system at all!

It depends on why you have low system HYD pressure.
If it is due to a failed pump, then ECAM will ask you to turn on the Y HYD ELEC pump to restore the pressure and ALTN BRKS Inop will not be listed.
"If yellow sys lost by ENG 2 PUMP LO PR:
YELLOW ELEC PUMP ..... ON"

If it is because you've lost all the fluid, then ALTN BRKS Inop will be listed because you won't even have anything useful in Y Accumulator.