A320 Brake loss

[tarik123]

A question for A320 pilots, did any of you ever lose brakes on the A320
while pedals were depressed at around 70 kts or less, without any warning, as this happened to me twice on 2 different airplanes during my last 10 years on the A320.

[sergejv]

It's very strange!
And what did you in these situations?
Can you give same more information about brake systems, configuration and indications (position of Autobrake and A/SKID switch, pressure of Yellow accumulator)? I think it was problems with BSCU unit and brake systems don't switch to alternate.

[tarik123]

Everything was normal, autobrakes off, brakes were lost passing
70 kts, luckily in both cases there was enough runway remaining
to stop by switching NWS/Anti skid switch off and apply 1000psi
of brakes.

[sergejv]

Yes your procedures were correct. By switching NWS/Anti skid switch off brake systems goes manually to alternate but it must go automatically.
Did the brakes pressure was ~2600 psi after engines start when you check manually brakes before takeoff?

[TowerDiamond]

what about the brake temperature? How come you didn't use autobrakes?

[tarik123]

Auto brakes were initialy used, This only happens at low speed.

Brake temp was normal, I think it has to do with the Tachometer signal
to the antiskid.

[sergejv]

Loss of braking
(Source: A320 FCOM, 3.2.32, QRH 1.13)

If no braking available:
• REV MAX
• BRAKE PEDALS RELEASE
Brake pedals should be released when the A/SKID & N/W STRG selector is switched
OFF,since the pedal force or displacement produces more braking action in alternate
mode than in normal mode.
• A/SKID & N/W STRG OFF
Braking system reverts to alternate mode.
• BRAKE PEDALS PRESS
Apply brake with care, since initial pedal force or displacement produces more braking
action in alternate mode than in normal mode.
• MAX BRK PR 1000 PSI
Monitor brake pressure or BRAKES PRESS indicator. Limit brake pressure to
approximately 1000 psi and, at low ground speed, adjust brake pressure as required.
If still no braking :
• PARKING BRAKE USE
Use short successive parking brake applications to stop the aircraft. Brake onset
asymmetry may be felt at each parking brake application. If possible, delay the use of the
parking brake until low speed, to reduce the risk of tire burst and lateral control difficulties.

[tarik123]

Thank you, but I think their is a temporary revision about this
subject talking about certain types of tires that might cause
loss of brakes at low speeds.