Narrative:

During cruise flight hourly check of system parameters; both flight crew members noticed the yellow system quantity declining. At pushback yellow system quantity was 'in the green' range. Monitored affected system over the course of the next 1/2 hour and it showed a steady decline. Captain opted to review QRH as well as flight manual and contacted maintenance control via ACARS. We elected to continue towards our destination as we did not have any ECAM warnings or cautions at that time. Factors for this decision included time in-flight left (about 1:30) and the availability of many suitable airports in the immediate area. We also considered maintenance availability and the fact that we still had 2 other hydraulic system operating normally and displaying normal quantity indications. About 350 mi from the destination airport we received an amber ECAM for low yellow system pressure; low Y system quantity and a ptu fault. Captain again determined no action required by QRH and performed ECAM actions while I continued to fly towards destination. Captain tried to contact maintenance control and dispatch without any success. ACARS was used slowing down the communication process. Captain and I discussed declaring an emergency at that point and agreed that it was important to have equipment standing by in case of another hydraulic system failure. I notified center who in turn notified approach control and the tower. The captain communicated our plan with the flight attendants and made a very well thought out PA to the passenger. Related to human factors; I must say that the captain provided an excellent example of how to manage an abnormal situation. He was very proactive in reviewing the ECAM procedures even before the ECAM occurred. He took everyone's information and made a clear and concise decision which resulted in a normal landing and taxi in to the gate. Great job! On the other side; during my communication with ATC; I was asked for fob (in hours) and souls on board. I communicated this information to the high sector and when switched to the low sector controller was asked for the nature of the emergency; fob and souls onboard again. This occurred again with approach control. Also approach control held us up too high to make a normal descent because of traffic. When an aircraft declares an emergency they should be given priority over all traffic. In our slightly degraded mode this was not an issue; however; it is not the responsibility of the approach controller to assess our situation. ATC needs to do better communicating information about flts who declare emergencys because after giving fob in min/hours; souls on board and the nature of the emergency 3 times to 3 separate controllers (high sector; low sector and approach control) providing this information became a distraction to the flight crew at a time when our attention needed to be focused on the situation.

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Original NASA ASRS Text

Title: A320 FLT CREW AT FL350 NOTICE YELLOW HYDRAULIC SYSTEM QUANTITY DECLINING. APPROACHING DESTINATION; SYSTEM FAILS AND THE FLT CREW DECLARES AN EMERGENCY. A NORMAL LANDING ENSUES AT DESTINATION.

Narrative: DURING CRUISE FLT HRLY CHK OF SYS PARAMETERS; BOTH FLT CREW MEMBERS NOTICED THE YELLOW SYS QUANTITY DECLINING. AT PUSHBACK YELLOW SYS QUANTITY WAS 'IN THE GREEN' RANGE. MONITORED AFFECTED SYS OVER THE COURSE OF THE NEXT 1/2 HR AND IT SHOWED A STEADY DECLINE. CAPT OPTED TO REVIEW QRH AS WELL AS FLT MANUAL AND CONTACTED MAINT CTL VIA ACARS. WE ELECTED TO CONTINUE TOWARDS OUR DEST AS WE DID NOT HAVE ANY ECAM WARNINGS OR CAUTIONS AT THAT TIME. FACTORS FOR THIS DECISION INCLUDED TIME INFLT LEFT (ABOUT 1:30) AND THE AVAILABILITY OF MANY SUITABLE ARPTS IN THE IMMEDIATE AREA. WE ALSO CONSIDERED MAINT AVAILABILITY AND THE FACT THAT WE STILL HAD 2 OTHER HYD SYS OPERATING NORMALLY AND DISPLAYING NORMAL QUANTITY INDICATIONS. ABOUT 350 MI FROM THE DEST ARPT WE RECEIVED AN AMBER ECAM FOR LOW YELLOW SYS PRESSURE; LOW Y SYS QUANTITY AND A PTU FAULT. CAPT AGAIN DETERMINED NO ACTION REQUIRED BY QRH AND PERFORMED ECAM ACTIONS WHILE I CONTINUED TO FLY TOWARDS DEST. CAPT TRIED TO CONTACT MAINT CTL AND DISPATCH WITHOUT ANY SUCCESS. ACARS WAS USED SLOWING DOWN THE COM PROCESS. CAPT AND I DISCUSSED DECLARING AN EMER AT THAT POINT AND AGREED THAT IT WAS IMPORTANT TO HAVE EQUIP STANDING BY IN CASE OF ANOTHER HYD SYS FAILURE. I NOTIFIED CTR WHO IN TURN NOTIFIED APCH CTL AND THE TWR. THE CAPT COMMUNICATED OUR PLAN WITH THE FLT ATTENDANTS AND MADE A VERY WELL THOUGHT OUT PA TO THE PAX. RELATED TO HUMAN FACTORS; I MUST SAY THAT THE CAPT PROVIDED AN EXCELLENT EXAMPLE OF HOW TO MANAGE AN ABNORMAL SITUATION. HE WAS VERY PROACTIVE IN REVIEWING THE ECAM PROCS EVEN BEFORE THE ECAM OCCURRED. HE TOOK EVERYONE'S INFO AND MADE A CLR AND CONCISE DECISION WHICH RESULTED IN A NORMAL LNDG AND TAXI IN TO THE GATE. GREAT JOB! ON THE OTHER SIDE; DURING MY COM WITH ATC; I WAS ASKED FOR FOB (IN HRS) AND SOULS ON BOARD. I COMMUNICATED THIS INFO TO THE HIGH SECTOR AND WHEN SWITCHED TO THE LOW SECTOR CTLR WAS ASKED FOR THE NATURE OF THE EMER; FOB AND SOULS ONBOARD AGAIN. THIS OCCURRED AGAIN WITH APCH CTL. ALSO APCH CTL HELD US UP TOO HIGH TO MAKE A NORMAL DSCNT BECAUSE OF TFC. WHEN AN ACFT DECLARES AN EMER THEY SHOULD BE GIVEN PRIORITY OVER ALL TFC. IN OUR SLIGHTLY DEGRADED MODE THIS WAS NOT AN ISSUE; HOWEVER; IT IS NOT THE RESPONSIBILITY OF THE APCH CTLR TO ASSESS OUR SITUATION. ATC NEEDS TO DO BETTER COMMUNICATING INFO ABOUT FLTS WHO DECLARE EMERS BECAUSE AFTER GIVING FOB IN MIN/HRS; SOULS ON BOARD AND THE NATURE OF THE EMER 3 TIMES TO 3 SEPARATE CTLRS (HIGH SECTOR; LOW SECTOR AND APCH CTL) PROVIDING THIS INFO BECAME A DISTR TO THE FLT CREW AT A TIME WHEN OUR ATTN NEEDED TO BE FOCUSED ON THE SITUATION.

Data retrieved from NASA's ASRS site as of January 2009 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.