Narrative:

In cruise at FL350 we got an ECAM for yellow system hydraulic fluid quantity low. We performed the ECAM checklist; QRH and follow up. Initially we fixated on the yellow electric hydraulic pump switch on/auto positions not the ptu on/off switch. The ptu was subsequently intermittent and then failed. We performed the loss of yellow system pressure ECAM/QRH procedures. We declared an emergency in perfect VMC conditions; descended and turned back toward the airport. The green system intermittently indicated overheat during the turn. The flight attendants and cabin were notified of the upcoming precautionary landing and time. Distance and speed adjustments from the QRH were checked for the approach and landing. When flaps were selected; only slats 3/flaps 0 were available. We made a left turn in the pattern as green/blue pressures were still good to recheck new distance requirements and reference speed adjustments. When turning final again the gear did not release from the uplocks when selected down; so we manually released it and it quickly extended and locked. The aircraft was over the fence at adjusted va with a good touchdown and near normal deceleration. We were rolling slowly by 5;000 ft; and continued slowly to near a far end turnoff and set brakes. We made a P/a to the passengers and flight attendants that we were fine but that we would be towed into the gate. We instructed the emergency crews to stay away from the landing gear until the tires cooled. The left pair (with reverser and upwind) was less than 300 degrees C. The right pair (no reverser and downwind) was in the mid 500 degrees C. The fans were turned on and the right pair came down to the mid 300s C prior to tug arrival. The aircraft was towed to the gate. The passengers were upbeat during deplaning and there was no immediate apparent injury or mental trauma. During our post-flight debrief we both looked up at the hydraulic panel at the ptu on/off switch where it had been the whole time and realized our procedural error.enroute an o-ring in the yellow hydraulic system failed rapidly dumping all yellow system fluid overboard. Needless to say; I will probably live the rest of my life with heightened hydraulic system awareness. Two thoughts come to mind; however: 1. If desired; a following note could be placed in the QRH after the loss of yellow system fluid checklist directing the crew to perform the loss of yellow system pressure ECAM; indicating that if this ECAM checklist was not present that the loss of fluid checklist was not complete. 2. A spot event could be flown during recurrent training; not involving the whole hydraulic system loss scenario; but merely the initial step of selecting the ptu off; so the crews have a look at that never-used switch. The electric yellow hydraulic pump switch is used once or twice per leg during normal operations to inhibit ptu operation. This might be of some value to other crews.

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Original NASA ASRS Text

Title: An A320 experienced Yellow Hydraulic Reservoir low level ECAM at FL350. ECAM procedures were complied with except the PTU switch was not turned off. The flight diverted. During approach only slats extended and the gear was extended manually. A no flap landing ensued with a tow to the gate.

Narrative: In cruise at FL350 we got an ECAM for yellow system hydraulic fluid quantity low. We performed the ECAM checklist; QRH and follow up. Initially we fixated on the yellow electric hydraulic pump switch on/auto positions not the PTU on/off switch. The PTU was subsequently intermittent and then failed. We performed the loss of yellow system pressure ECAM/QRH procedures. We declared an emergency in perfect VMC conditions; descended and turned back toward the airport. The green system intermittently indicated overheat during the turn. The Flight Attendants and cabin were notified of the upcoming precautionary landing and time. Distance and speed adjustments from the QRH were checked for the approach and landing. When flaps were selected; only slats 3/flaps 0 were available. We made a left turn in the pattern as green/blue pressures were still good to recheck new distance requirements and reference speed adjustments. When turning final again the gear did not release from the uplocks when selected down; so we manually released it and it quickly extended and locked. The aircraft was over the fence at adjusted Va with a good touchdown and near normal deceleration. We were rolling slowly by 5;000 FT; and continued slowly to near a far end turnoff and set brakes. We made a P/A to the passengers and Flight Attendants that we were fine but that we would be towed into the gate. We instructed the emergency crews to stay away from the landing gear until the tires cooled. The left pair (with reverser and upwind) was less than 300 degrees C. The right pair (no reverser and downwind) was in the mid 500 degrees C. The fans were turned on and the right pair came down to the mid 300s C prior to tug arrival. The aircraft was towed to the gate. The passengers were upbeat during deplaning and there was no immediate apparent injury or mental trauma. During our post-flight debrief we both looked up at the hydraulic panel at the PTU on/off switch where it had been the whole time and realized our procedural error.Enroute an o-ring in the yellow hydraulic system failed rapidly dumping all yellow system fluid overboard. Needless to say; I will probably live the rest of my life with heightened hydraulic system awareness. Two thoughts come to mind; however: 1. If desired; a following note could be placed in the QRH after the loss of yellow system fluid checklist directing the crew to perform the loss of yellow system pressure ECAM; indicating that if this ECAM checklist was not present that the loss of fluid checklist was not complete. 2. A spot event could be flown during recurrent training; not involving the whole hydraulic system loss scenario; but merely the initial step of selecting the PTU off; so the crews have a look at that never-used switch. The electric yellow hydraulic pump switch is used once or twice per leg during normal operations to inhibit PTU operation. This might be of some value to other crews.

Data retrieved from NASA's ASRS site as of April 2012 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.