A320 Brake Pressure & Accum. Indication

[beardedclam]

Day 1 of type rating. I thought the brake pressure / accum. display only showed actual accumulator pressure and alternate (yellow) hydraulic brake pressure. Just reading that on application of parking brake, normal operations, accumulator must be in green on display, and brakes pressure will show around 2000 PSI. Are we not in fact using green system? (I didn't expect to see any indication for brake pressure as thought we were using green.....)

[john_tullamarine]

Perhaps you might let the thread run for more than a day prior to concluding that there is no interest in responding ?

[Goldenrivett]

beardedclam

I thought the brake pressure / accum. display only showed actual accumulator pressure and alternate (yellow) hydraulic brake pressure.

Correct.

on application of parking brake...... Are we not in fact using green system?

No.
The Y accumulator pressure should be in the green sector - nothing to do with the the Green Sys Hyds.

[aanubis]

Read the systems.
Parking brake is not on Green hydraulic.

[Kuchan]

The brake pressure sensor is tapped off from the air side of the accumulator.

Parking brake is using yellow system of which the press is shown on the acc. pointer.

Normal brake is Green system and shown on the 2 pointes moving up as
you apply the foot brakes provided the green pump is on.

Putting brake in PARK position disables the foot brakes.

[Goldenrivett]

Originally posted by Kuchan

Normal brake is Green system and shown on the 2 pointes moving up as you apply the foot brakes provided the green pump is on.

Not according to my FCOM.

DSC 32 30 20
(2) BRAKES and ACCU PRESS indicator
Brake pressure is only indicated when the yellow hydraulic system controls the brake pressure, which means when the : -
Alternate braking system is activated, or -
Parking brake is applied.

ACCU PRESS :
Indicates the pressure in the yellow brake accumulator.
BRAKES :
Indicates the yellow pressure delivered to the left and right brakes, as measured upstream of the alternate servovalves.

[vilas]

Kuchan
On older aircraft as you taxi out brakes check is carried out by applying brakes and checking pressure zero which ensures green system has taken over.

[Kuchan]

Thanks for the correction and to refresh my memory.

Indeed, there is no way to check the amount of normal brake pressure by looking at the brake gauge.

[320busboy]

correct, Only the Yellow applied pressure per side is shown on the triple ind. However you will see a slight flick to about 1000 during rapid brake application on the classic A320 using normal brakes. This is due to the time taken for the BSCU to open the normal selector valve (Green) and then the auto selector valve will move to inhibit the Yellow Alt supply. As you depress the brake pedals the hydraulic signal is sent down the LP lines to the dual valve and simultaneously by the BPTU's to the BSCU. Essentially the ALternate brakes are applied for a fraction of a second while the Normal brakes take over. On the Enhanced Aircraft, you wont see this happen.