Narrative:

Lost hydraulic system a quantity on climb out. Notified dispatch and ATC. Declared an emergency and decided to return to ZZZ. Followed irregular procedure checklist. I was the PF at the time the problem was noticed. Xferred flight controls to the captain after completion of the checklist. Approach and landing was uneventful. Cleared the runway and taxied to the gate under our own control and power.

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Original NASA ASRS Text

Title: B737-500 EXPERIENCES LOSS OF A SYS OIL QUANTITY AND PRESSURE. DECLARE EMER AND RETURN TO DEP ARPT.

Narrative: LOST HYD SYS A QUANTITY ON CLBOUT. NOTIFIED DISPATCH AND ATC. DECLARED AN EMER AND DECIDED TO RETURN TO ZZZ. FOLLOWED IRREGULAR PROC CHKLIST. I WAS THE PF AT THE TIME THE PROB WAS NOTICED. XFERRED FLT CTLS TO THE CAPT AFTER COMPLETION OF THE CHKLIST. APCH AND LNDG WAS UNEVENTFUL. CLRED THE RWY AND TAXIED TO THE GATE UNDER OUR OWN CTL AND PWR.

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.