Date: 201701
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Emergency Brake System
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General Maintenance Action
Contributing factors: Manuals; Procedure
Primary problem: Procedure

Narrative: During preflight; maintenance responded to the aircraft based on my concern with a previous write-up: 'With aircraft parked and parking brake set aircraft moved forward then lurched to stop with ECAM. OPS normal to gate.' This was signed off as ops normal by maintenance in the corrective action block. On the first flight of the day preflight; after the FO checked that the chocks were in place; I accomplished the Alternate Brake Check below when I noted the following:1. I turned on the Y hydraulic pump; after making sure it was clear on the ground. The Y pump recharged the accumulator. I did not turn off the Y pump and started my alternate brake check; knowing the alternate brakes needed the Y system pressure. I got a pressure indication of 0 for both the left and right brake. Before writing up the alternate brake system I called out maintenance in case I was missing something. Maintenance; initially; could not figure out why I wasn't getting any brake pressure on the alternate system; so we wrote it up in the logbook. We called Maintenance Control who was reading the maintenance manual and said the Green system has to be depressurized for the alternate system to work correctly. A second mechanic arrived on board our aircraft and said turn off the PTU (Power Transfer Unit); even though neither our checklist nor MX checklist said to shut off the PTU. After shutting off the PTU the Green system was depressurized and the alternate brakes checked good with good pressure. So I asked the mechanic where it said in either checklist to shut off the PTU. Even though neither checklist stated to turn off the PTU; so the Green system and normal brakes were unpressurized; this was the only way to depressurize the Green system.2. I called the Chief Pilot on Duty to discuss the Alternate Brake Checklist. I told him there was nowhere on our Alternate Brake Checklist to turn off the PTU to depressurize the Green system in either checklist. After further analyzing the checklist; the checklist does not require the Y pump to be on for the check. The step above the alternate brakes checklist does say the Y pump MAY be needed to recharge the accumulator. So; since the checklist did not call for the Y pump to be on; we turned the Y pump off and accomplished the Alternate Brake Check successfully.3. So without the Y pump on; we are checking the Alternate Braking System on accumulator; which I'm not sure that is what Airbus and our company want. This brings up a couple of safety items; with the accumulator being bled down to check the Alternate Braking System without the Y pump on; there is a chance ground personnel would remove the chocks getting ready to depart without the flight crew knowing it. The tug may; or may not; be hooked up to the aircraft with its parking brake on. After the parking brakes are reset after the check on accumulator; the crew would have to ensure the accumulator had not been bled down; or turn the Y pump back on to recharge the accumulator. 4. I'm not sure if the Alternate Brake System check is designed to be done with Y system pressure or accumulator pressure. The accumulator braking is supposed to be a backup to the Alternate Braking system; as a last resort.5. I suggest looking at the checklists to see if they both can be improved; with a brief note and/or a step added on the Y pump position for the check.Change the checklist to state exactly how to check the Alternate Brakes with new notes. Also; consider the safety ramifications of bleeding down the accumulator for the check without the Y pump on. A review of the checklist; in regards to; ground personnel removing the chocks for departure prior to the check being completed with the accumulator. I believe the check should be done with normal Yellow system pressure with the PTU off. The check can only be accomplished in this manner with the PTU off. At the end of the Alternate Brake Check; the PTU could be turned back on to ensure operation of the PTU/Green hydraulic system/normal brakes. Check the parking brake on; then turn off the pump. The alternative is to use the accumulator to check the Alternate Brakes; then recharge the accumulator with the Y pump.




Synopsis: A321 Captain reported a possible error in the company's Alternate Brake Check procedure which is to be accomplished before the first flight of the day.