A320 Accumulator check. Is the 7 Full Brake Application needed to be checked?

[r0w]

Here’s the thing..



eng 1 provides green Hyd; Normal braking

eng 2 provides yellow Hyd; Alternate braking



when engines are shutdown/OFF, and we put the Parking Brakes to ON, or step of the foot brakes, then the ACCU PRESS on the triple indicator will slowly go down or be reduced.



in case of a dual engine failure, we loss both normal and alternate braking (kinda). And all we are left is the supposed 7 Full Brake Applications (at least 7) that the aircraft can give from the Accumulator Tank, which automatically regulates pressure to 1000PSI both on the left & right side.



in case of a Loss of Braking, we do the procedure and it leaves us with the Alternate Braking. But not necessarily with only 7 applications (since we still have Yellow HYD continuously from engine 2, correct (Q#1)? But if we have a Loss of Braking together with a problem of losing Eng 2 or the Yellow Hyd, then it leaves us again with only the 7 Full Applications (Q#2)?



Lastly, when we do the Preliminary Cockpit Preparations, on the Parking Brake part, 3 things are done:



ACCU PRESS inidcator — Check

PARK BRK handle — ON

BRAKES PRESS indicator — CHECK



during this time, I know that its the Accumulator Pressure that we are using.



Now, at times, after setting the Parking Brakes to ON, the ACCU PRESS indicator of the triple indicators falls halfway or more than halfway (even almost to Zero). Followed by an ECAM.



Question is, is this Acceptable (Q#3)? coz when I also recharge the Brake Accumulator using the Yellow Electric Pump so it reaches green band, then I turn the yellow elec pump OFF and wait for awhile, then I step on the brakes after, it gives less than 7 Full Brake Applications that reaches 1000PSI (lets say on the 3rd or 4th time. It doesnt reach 1000PSI anymore; recently, it didnt even reach 1000PSI on the first try).



Is there somewhere that says that the Accumulator MUST BE ABLE to give 7 Full Brakes Application, OR ELSE it will be a NO GO (Q#4)?



Thank you for inputs, clarifications, or any corrections in any of the details/info I posted that may be wrong.

[ahramin]

ACCU PRESS inidcator — Check
You're checking (or ensuring with the yellow electric pump) that the ACCU PRESS indicator is in the green band (your accumulator is charged)

PARK BRK handle — ON
nothing here about waiting for a while and then stepping on the brakes multiple times

BRAKES PRESS indicator — CHECK
When you apply the parking brake, you are CHECKing for "normal indications" in the triple indicator.

So if you are doing the test as it is written, are you getting normal indications or not? If I was doing this test and I lost a large amount of pressure in the ACCU PRESSURE gauge and got an ECAM warning, I would not consider it a normal indication. Normal is a small decrease in pressure.

[vilas]

Originally Posted by r0w

Here’s the thing..



eng 1 provides green Hyd; Normal braking

eng 2 provides yellow Hyd; Alternate braking



when engines are shutdown/OFF, and we put the Parking Brakes to ON, or step of the foot brakes, then the ACCU PRESS on the triple indicator will slowly go down or be reduced.



in case of a dual engine failure, we loss both normal and alternate braking (kinda). And all we are left is the supposed 7 Full Brake Applications (at least 7) that the aircraft can give from the Accumulator Tank, which automatically regulates pressure to 1000PSI both on the left & right side.


in case of a Loss of Braking, we do the procedure and it leaves us with the Alternate Braking. But not necessarily with only 7 applications (since we still have Yellow HYD continuously from engine 2, correct (Q#1)? But if we have a Loss of Braking together with a problem of losing Eng 2 or the Yellow Hyd, then it leaves us again with only the 7 Full Applications (Q#2)?



Lastly, when we do the Preliminary Cockpit Preparations, on the Parking Brake part, 3 things are done:



ACCU PRESS inidcator — Check

PARK BRK handle — ON

BRAKES PRESS indicator — CHECK

during this time, I know that its the Accumulator Pressure that we are using.

Now, at times, after setting the Parking Brakes to ON, the ACCU PRESS indicator of the triple indicators falls halfway or more than halfway (even almost to Zero). Followed by an ECAM.

Question is, is this Acceptable (Q#3)? coz when I also recharge the Brake Accumulator using the Yellow Electric Pump so it reaches green band, then I turn the yellow elec pump OFF and wait for awhile, then I step on the brakes after, it gives less than 7 Full Brake Applications that reaches 1000PSI (lets say on the 3rd or 4th time. It doesnt reach 1000PSI anymore; recently, it didnt even reach 1000PSI on the first try).

Is there somewhere that says that the Accumulator MUST BE ABLE to give 7 Full Brakes Application, OR ELSE it will be a NO GO (Q#4)?



Thank you for inputs, clarifications, or any corrections in any of the details/info I posted that may be wrong.

Loss of braking in dual engine fail is due to loss hydraulics but with both engines operating there can be other reasons for loss of braking. If normal brake doesn't work it automatically switches to Yellow alternate brake with anti skid but when that doesn't work then you force it in alternate brake by switching off NWS/ASKID off then comes down to seven applications and if that doesn't work then parking brake in short bursts.
After switch off, Parking brake on accumulator pressure supposed to hold for 12hrs. Pilots don't do 7 application check during preparation, may be maintenance does.

[r0w]

Originally Posted by ahramin

ACCU PRESS inidcator — Check
You're checking (or ensuring with the yellow electric pump) that the ACCU PRESS indicator is in the green band (your accumulator is charged)

PARK BRK handle — ON
nothing here about waiting for a while and then stepping on the brakes multiple times

BRAKES PRESS indicator — CHECK
When you apply the parking brake, you are CHECKing for "normal indications" in the triple indicator.

So if you are doing the test as it is written, are you getting normal indications or not? If I was doing this test and I lost a large amount of pressure in the ACCU PRESSURE gauge and got an ECAM warning, I would not consider it a normal indication. Normal is a small decrease in pressure.

the FCOM is not detailed about “normal indication”. But yes, I know that the drop should only be little or small, and it would have to take several (give and take 5 or more) applications before the indication of the ACCU PRESS drops to a point where it is low enough to give an ECAM.

On the other hand, if the pressures drops and gives an ECAM with only 1 try / 1 application. This is NOT normal. But is there a reference we can point to or refer to, to say that this is not normal?

and to add… if this is the case, what assurance or other checks/procedures can we do to see if the ACCU PRESS would be able to give us 7 Full Brake Applications if needed later on given certain failure scenarios?

thanks Ahramin

[r0w]

Originally Posted by vilas

Loss of braking in dual engine fail is due to loss hydraulics but with both engines operating there can be other reasons for loss of braking. If normal brake doesn't work it automatically switches to Yellow alternate brake with anti skid but when that doesn't work then you force it in alternate brake by switching off NWS/ASKID off then comes down to seven applications and if that doesn't work then parking brake in short bursts.
After switch off, Parking brake on accumulator pressure supposed to hold for 12hrs. Pilots don't do 7 application check during preparation, may be maintenance does.

okay, thank you for these.

anyway, the point im trying to derive is. I’ve had ACs where, when you set the parking brakes to ON during the cockpit prep, the ACCU PRESS drops really low and gives an ECAM. This is not normal. But I have no reference to refer to what is Normal and What is not.

And whenever the ACCU PRESS drops significantly, followed immediately by an ECAM. I recharge it with the Yellow ELEC PUMP. After which, I try to see if it can give 7 Full Brake Applications [when the scenario comes] as per the manual, (FCOM/DAC/32/30/10), and if the left & right indicator reaches 1000PSI, by stepping on the foot brakes.

Although I know that there is no procedure in the manual that the foot brake application should be done, I am doing this just to see if the AC will be able to provide the 7 applications (that reaches 1000PSI). This is because maintenance would release the AC even if the ACCU PRESS drops significantly, as long as when it is recharged using the YEP, the pressure holds to the green band after recharging. And if a scenario later would happen that would leave me with the 7 Full Brake Applications only to use, im sure I dont have those already given the scenario during the cockpit preparation (correct me if Im wrong here).

I’d like to assure myself that even if the maintenance release the AC despite having a “Not Normal” decrease in the ACCU PRESS during the cockpit prep, it will still later give the 7 FBA.

thanks again Vilas

[Goldenrivett]

Originally Posted by r0w

I’d like to assure myself that even if the maintenance release the AC despite having a “Not Normal” decrease in the ACCU PRESS during the cockpit prep, it will still later give the 7 FBA.

Hi r0w,
It sounds like you may have found an aircraft which doesn't have the correct pre-charge pressure in the brake accumulator. (see video "youtu.be/cqDOnAQCe4c" on how engineers check it) You should get 7 brake applications like this : "youtu.be/J31OyM78nOk" But it's not a routine check for pilots.

If you charge the Y hydraulics to 3,000 psi first and then press and release the foot brakes once (to close the distance between the pads and discs) then turn off the Y hyd pump - then apply the foot brake to 1,000 psi, the accumulator pressure gauge should ideally show in the green (or very close to) after one application. (see video at around 2.30.) If you observe a big drop in accumulator pressure after just one application - then I would suspect the accumulator pre-charge pressure is outside limits.