1
$\begingroup$

As part of the preliminary cockpit preparation in my company’s older A320s we have to perform an alternate brake system check but not in the newer ones as per FCOM Normal procedures as below. I found out that there is a system difference but didn’t fully understand could someone please explain the difference?

ALTERNATE BRAKING SYSTEM
Note: The purpose of this check is to verify, before the first flight of the day, the efficiency of the alternate braking system (absence of “spongy pedals”).
Y ELEC PUMP pb-sw....................................................................................................CHECK OFF CHOCKS..............................................................................................................CHECK IN PLACE PARK BRK handle.......................................................................................................................OFF BRAKE PEDALS.....................................................................................................................PRESS Apply maximum pressure on both pedals.
BRAKE PRESSURE (on BRAKE press indicator).................................................................CHECK Pressure must build up without delay symmetrically on left and right sides for the same application simultaneously applied on left and right pedals. With full pedal deflection, the pressure must be between 2 000 and 2 700 PSI.
BRAKE PEDALS................................................................................................................RELEASE PARK BRK handle........................................................................................................................ON The parking brake must be on during the exterior inspection to allow the flight crew to check brake wear indicators.

$\endgroup$
  • $\begingroup$ Different braking systems, see Alternate Brake Check on A320/321 $\endgroup$ – mins Jan 11 '18 at 9:19
  • $\begingroup$ I still didn’t understand? This is the answer which my company has provided. But I don’t understand the logic. The aircraft is without electrically controlled Alternate Braking Control Unit (ABCU). Alternate braking in turn is controlled by BSCU.As a consequence of this during the preliminary cockpit preparation, it is necessary to check the alternate braking system as it is not automatically monitored. $\endgroup$ – Jai Jan 11 '18 at 9:38
2
$\begingroup$

On the old system the switching between the normal braking using the green circuit to the alternate braking using the yellow circuit is done by an automatic switching valve pressure dependant (Automatic selector).The alternate system being very little used, it happened the valve did not switch from green to yellow when loosing the green circuit

please refer to the old system here below

http://www.a320dp.com/A320_DP/landing-gear/images/braking-schematic-d.jpg

On the new system the alternate brake is activated by a specific computer(ABCU) decision and is automatically tested by the computer at power up as soon as the hydraulic pressures are available, please refer here below to the new circuit

https://m.facebook.com/A320Theory/posts/normal-brakingnormal-braking-is-obtained-when-the-green-hydraulic-pressure-is-av/790898894383508/

Hope this has been useful and explains why it was very important to do the testing on the old system

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.