Date: 201903
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Airspace: Class B ZZZ
ATC / advisory: Ramp ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown; Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: Flight Crew Returned To Gate; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: Aircraft was pushed back and towed out to the end of the alley. Engine 1 was started. Parking brake was set per push crew request and per SOP the accumulator pressure was noted and found to be at appx. 2000 lbs. Push crew was requested to remain hooked to the aircraft since brake pressure was not 'normal.' Maintenance was notified via ACARS and over the radio. The local maintenance controller asked us to call [Maintenance Control] and verify with them that a return to the gate was required to service the brake accumulator at a minimum. [Maintenance Control] concurred and a return to gate was coordinated. Aircraft was towed back to the gate.Eventually mechanics made it to the aircraft and the accumulator was serviced and seemed to be holding pressure. Since the brake accumulator is part of the hydraulic system; the crew checked hydraulic levels on the ECAM [ Electronic Centralized Aircraft Monitoring] as the mechanic was leaving. The yellow system now showed greatly over serviced and the mechanic was called back and shown the problem and was asked to correct the issue that the servicing of the accumulator seemed to have caused.At this point all hell broke loose and the serious lack of understanding of Airbus hydraulic systems by the mechanics at [this] gate went on full display. Instead of simply de-pressurization of the yellow system and draining the over-serviced system; a process that takes normally 15 minutes or so; the mechanics attempted multiple items in what appeared to be an attempt to transfer fluid between systems; like the technique used to transfer fluid between systems on the 737. Flight controls were cycled and 'dual input' calls were heard coming from the flight deck. At some point the yellow system was pressurized intermittently via some other source than the flight deck electric pump control; and pressure on the yellow system could be witnessed to rise to 400-600 lbs and a bit of a whining sound could be heard on the flight deck as this occurred. This is also something that I have never witnessed on the Airbus and would have no effect on yellow system quantity to the best of my systems knowledge and might in fact be a very unsafe thing to do.[Maintenance Control] was consulted again as what was going on was nothing that I had ever seen done to fix a simple hydraulic over service condition. [Maintenance Control] agreed that whatever was going on made no sense and that all that needed to be done was drain the fluid from the over serviced yellow system. Draining a hydraulic system requires absolutely no flight deck access by competent mechanics other than to verify readings and to put out placards to ensure hydraulics aren't operated. I've seen it done multiple times at multiple other stations. Why did we need mechanics in both flight deck seats manipulating who knows what in a vain attempt to transfer fluid between systems?Eventually; at some point the decision was made to give us another aircraft and as we were on the jet bridge to leave the agent opened the door and said 'we're boarding.' What? No; I'm not satisfied with the maintenance status of this aircraft. Don't board. I called the [Flight Operations Manager] and was told that the aircraft had been signed off and that I couldn't refuse an aircraft that had been properly signed off by licensed [Company] mechanics. Well; whoever told the [Flight Operations Manager] that the aircraft was signed off was lying; as when I went to flight deck; the gear door ECAM was still present and the brake pressure was at 0. I have no idea who at maintenance was pushing to sign off an un-airworthy aircraft; or who chose to lie and say that an un-airworthy aircraft was signed off; but this was clearly a majorly unsafe and illegal situation.Furthermore; not once during the entire operation did I see a mechanic at that gate with an iPad out referencing the iPad or the Tech Order. It seems to me that there was a very cavalier attitude amongst the mechanics at that gate and that really exacerbated the unsafe and incompetent handling of the hydraulic over servicing.After I pointed out to the [Flight Operations Manager] that the aircraft was actually not signed off or airworthy; the decision to change aircraft was again put in place. I have no idea what ever was finally done to the original aircraft; but I shudder to think of how it may have been eventually signed off; and if that sign off was correct or legal.


Second narrative: After a normal pre-flight and pushback; the brake accumulator gauge was not in the green upon the setting of the parking brake after completion of the pushback. The Captain noticed the problem after when confirming that the 'brakes set; pressure... not normal'.He did not allow the tug/ground crew to go anywhere and we coordinated with ramp to stay where we were while evaluating the problem and possible solutions. While he was on the phone ZZZ line MX (Maintenance); the gauge dropped from out of the normal range to zero. We wrote up the problem and returned to the gate. The real issue started when the first mechanic boarded. He immediately suggested deferring the gauge and said it was an item in the MEL. While this is true; the problem as we saw it wasn't the gauge but the accumulator not holding pressure. It took some convincing of the mechanic that they actually had to troubleshoot the problem instead of pencil whip it. He left the flight deck an unhappy camper. Later; as we were waiting and trying to coordinate with ZZZ line MX; a second mechanic came up and tried to convince us of the same thing. He turned on the electric pump; which pressurized the yellow system and recharged the accumulator. He did stay on the flight for the 4-5 minutes it took for the accumulator to reach zero again. At this point it seemed he understood the problem was in the accumulator. He said he would service the accumulator. This apparently was accomplished. The accumulator pressure; with the electric pump off and no other hydraulic system on; the gauge read in the green. The mechanic came up we said it was good and that was that. We then checked the hydraulic fluids. The yellow system fluid had been over serviced so much that the indicator was literally touching the fire valve icon on the systems display. We asked maintenance to bring the yellow system back to normal levels. We saw this the night before and it took around 5 minutes to accomplish; we were expecting the same. After 15-20 minutes; the mechanics came up to the flight deck to check the fluid levels. Nothing had changed; except the brake accumulator valve now read zero; again. They then started turning on / off packs and hydraulic pumps; and at one point during this visit the mechanic got into the left seat and started manipulating the side stick. Nothing worked. The mechanic left the flight deck. The brake accumulator was then serviced again back into the normal range. The mechanics returned to the flight deck. I was in the forward galley at the time; allowing them room to do whatever it was they needed. Twice I heard the 'DUAL INPUT' flight control aural warning; meaning they were manipulating the side sticks; but this time it was both. We had started the process of swapping aircraft; the Captain was on the phone with the [Flight Operations Manager] out on the jet bridge. The first mechanic who showed up stormed out the jet bridge door muttering something about 'He's just got an axe to grind'. At this point the Captain told me that it had been relayed to the [Operations Control] that the aircraft had been signed off. That was interesting in that the yellow system was still over serviced. We collected our things and headed to the new aircraft.Throughout this entire process; one that took conservatively 60 minutes; at no point did I see a mechanic with an iPad; iPhone; or paper documentation with a procedure to service either the accumulator; the yellow system; trouble shoot the problem or test to see if it was fixed. Even at the initial flight deck visit; where the mechanic told us he was deferring the gauge; we had to look up the MEL as he didn't have the number or a way to look it up with him.


Synopsis: A320 flight crew reported maintenance technicians improperly servicing the hydraulic system.