Narrative:

During cruise 'a' hydraulic system quantity was noted to be at zero. There was no other abnormal indication. When the so brought it to my attention he mentioned that he had seen it decrease a little, but thought it was due to cold soaking. He also mentioned the pump low pressure lights were not illuminated. We accomplished action steps of the hydraulic leak or loss checklist, but prior to proceeding with steps which would lead us to a specific checklist for system 'a' loss I called our maintenance coordinator and dispatcher to discuss the situation. After describing the indications I asked the maintenance coordinator if he thought we had a hydraulic failure. He said no, he thought it was an erroneous indication and the system was ok. I asked him a couple of times if I understood him correctly that he thought the system had not failed. He replied that was correct. The dispatcher said nothing. Something did not seem right to me, but I said I would consider the system to be ok unless I called them otherwise. We placed all hydraulic switches in their original position thus repwring the 'a' hydraulic system. I asked the so to give me his procedure book saying this does not seem correct. After reading the procedure a couple of times along with the follow-on conditional statements, it became clear that we had no option, but to consider the 'a' hydraulic system to be failed and follow the 'a' hydraulic system failed procedure. We reaccomplished the original procedure as well as the 'a' hydraulic system failed procedure. I notified the maintenance coordinator and dispatcher of our intentions also stating we would declare an emergency with approach control, stop on the runway, have maintenance pin the gear and tow us to the gate. At this time the dispatcher stated he agreed our only option was to consider the 'a' hydraulic system to be failed. (I thought it would have been helpful if he had entered into the discussion earlier instead of being silent). We descended to a lower altitude and slowed in order to adhere to limitations for 1 yaw damper inoperative. For the approach we lowered the landing gear manually and used an alternate means of extending the flaps and leading edge devices. Everything went as briefed. Approach, landing and tow in were uneventful. Where I made my mistake was giving too much importance to the hydraulic low pressure lights and flight control low pressure lights not being illuminated. That makes no difference in the procedure. When the quantity drops below 2.5 gallons you must assume a hydraulic system has failed or has a leak. This was not my first hydraulic system failure. If we had only read the original procedure in its entirety before calling maintenance control I would not be writing this now.

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Original NASA ASRS Text

Title: B727 HAS HYD LOSS INDICATION. COORD WITH MAINT DELAYS THE PROPER COMPLETION OF APPROPRIATE CHKLISTS AND IRREGULAR PROCS.

Narrative: DURING CRUISE 'A' HYD SYS QUANTITY WAS NOTED TO BE AT ZERO. THERE WAS NO OTHER ABNORMAL INDICATION. WHEN THE SO BROUGHT IT TO MY ATTN HE MENTIONED THAT HE HAD SEEN IT DECREASE A LITTLE, BUT THOUGHT IT WAS DUE TO COLD SOAKING. HE ALSO MENTIONED THE PUMP LOW PRESSURE LIGHTS WERE NOT ILLUMINATED. WE ACCOMPLISHED ACTION STEPS OF THE HYD LEAK OR LOSS CHKLIST, BUT PRIOR TO PROCEEDING WITH STEPS WHICH WOULD LEAD US TO A SPECIFIC CHKLIST FOR SYS 'A' LOSS I CALLED OUR MAINT COORDINATOR AND DISPATCHER TO DISCUSS THE SIT. AFTER DESCRIBING THE INDICATIONS I ASKED THE MAINT COORDINATOR IF HE THOUGHT WE HAD A HYD FAILURE. HE SAID NO, HE THOUGHT IT WAS AN ERRONEOUS INDICATION AND THE SYS WAS OK. I ASKED HIM A COUPLE OF TIMES IF I UNDERSTOOD HIM CORRECTLY THAT HE THOUGHT THE SYS HAD NOT FAILED. HE REPLIED THAT WAS CORRECT. THE DISPATCHER SAID NOTHING. SOMETHING DID NOT SEEM RIGHT TO ME, BUT I SAID I WOULD CONSIDER THE SYS TO BE OK UNLESS I CALLED THEM OTHERWISE. WE PLACED ALL HYD SWITCHES IN THEIR ORIGINAL POS THUS REPWRING THE 'A' HYD SYS. I ASKED THE SO TO GIVE ME HIS PROC BOOK SAYING THIS DOES NOT SEEM CORRECT. AFTER READING THE PROC A COUPLE OF TIMES ALONG WITH THE FOLLOW-ON CONDITIONAL STATEMENTS, IT BECAME CLR THAT WE HAD NO OPTION, BUT TO CONSIDER THE 'A' HYD SYS TO BE FAILED AND FOLLOW THE 'A' HYD SYS FAILED PROC. WE REACCOMPLISHED THE ORIGINAL PROC AS WELL AS THE 'A' HYD SYS FAILED PROC. I NOTIFIED THE MAINT COORDINATOR AND DISPATCHER OF OUR INTENTIONS ALSO STATING WE WOULD DECLARE AN EMER WITH APCH CTL, STOP ON THE RWY, HAVE MAINT PIN THE GEAR AND TOW US TO THE GATE. AT THIS TIME THE DISPATCHER STATED HE AGREED OUR ONLY OPTION WAS TO CONSIDER THE 'A' HYD SYS TO BE FAILED. (I THOUGHT IT WOULD HAVE BEEN HELPFUL IF HE HAD ENTERED INTO THE DISCUSSION EARLIER INSTEAD OF BEING SILENT). WE DSNDED TO A LOWER ALT AND SLOWED IN ORDER TO ADHERE TO LIMITATIONS FOR 1 YAW DAMPER INOP. FOR THE APCH WE LOWERED THE LNDG GEAR MANUALLY AND USED AN ALTERNATE MEANS OF EXTENDING THE FLAPS AND LEADING EDGE DEVICES. EVERYTHING WENT AS BRIEFED. APCH, LNDG AND TOW IN WERE UNEVENTFUL. WHERE I MADE MY MISTAKE WAS GIVING TOO MUCH IMPORTANCE TO THE HYD LOW PRESSURE LIGHTS AND FLT CTL LOW PRESSURE LIGHTS NOT BEING ILLUMINATED. THAT MAKES NO DIFFERENCE IN THE PROC. WHEN THE QUANTITY DROPS BELOW 2.5 GALLONS YOU MUST ASSUME A HYD SYS HAS FAILED OR HAS A LEAK. THIS WAS NOT MY FIRST HYD SYS FAILURE. IF WE HAD ONLY READ THE ORIGINAL PROC IN ITS ENTIRETY BEFORE CALLING MAINT CTL I WOULD NOT BE WRITING THIS NOW.

Data retrieved from NASA's ASRS site as of July 2007 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.