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.

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Original NASA ASRS Text

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

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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.