Altn brake check 320

[westinghouse]

hi,

on our 320's (MSN 2000 series) when you perform the altn brake check at the gate before engine start the brake pressure is automatically limited to 1000 psi.
it states also in FCOM3 that the altn brake check is not required.
however there have been times when i have done the brake check ive seen the pressure being limited to 1000psi and sometime it goesto around 2000-2700psi.
any reason as to why this brake pressure varies?
thanx

[OPEN DES]

Hi there,

You're probably operating a 'mixed' fleet of A320's with both the new and old alternate braking system.

The new alternate brake-system employs an ABCU which will modulate the pressure to 1000 psi. The old system does not, so will give you up to 3000psi (if the accumulator is full) during the check. The new system does not require the alternate brake check but is probably still done where there are 'mixed' fleets for SOP harmonisation.


edit: I must add that alternate braking is limited to 1000 psi on alternate braking by the ABCU, only when anti-skid is lost (BSCU lost or off). During the check the NWS switch is off, so will be the BSCU.

[nnc0]

The decision predates me but I understand that given the frequency of rolling aircraft once the parking brake is off, we opted to made this check a maintenance function. Rapid brake applications in the event of a roll tended to knock over folks standing in the cabin and could catch the ground crew by surprise if ramp comms were poor.

I'm still not clear on what the procedure would be if the Alternate braking failed while rolling. Use parking Brake?