Narrative:

When I arrived back in the cockpit; the first officer's briefed me that the center hydraulic system quantity had started dropping slowly just prior to the top of descent. They had performed the irregular operation for low hydraulic quantity; and had shut off the center hydraulic pumps with the quantity at .22. They had also reviewed the loss of the center hydraulic system irregular procedure. We discussed a diversion versus continuing to ord; and decided continuing would be the safest course of action by giving us enough time to thoroughly troubleshoot and brief the problem. We discussed attempting to lower the landing gear with the remaining fluid; and what would happen should that fail. We then briefed the remaining items on the loss of center system procedure; the alternate gear extension and the alternate flap extension procedures. First officer; the PF; and as I had just been sound asleep; I decided that having him continue to fly the approach and landing would probably be the safest option. At this point; first officer contacted dispatch and maintenance to brief them on the situation; and I briefed the flight attendants. I did declare a cabin advisory; and told the flight attendants to expect a normal landing with the exception that the landing gear would be lowered earlier than usual and that the approach speed would be slightly faster than normal. I decided that declaring an emergency with ATC was not necessary; but did inform them of the situation and asked for a slightly extended downwind/final in order to have time to electrically lower the flaps. Approximately 20 mi from touchdown we attempted to lower the gear normally. Turning the center system pumps on resulted in a continuation of the slow leak and putting the gear handle down resulted in the extension of only the nose gear. At this point; we shut the center system off and performed the alternate gear extension procedure. Some center system fluid was regained after gear extension; but we elected to extend the flaps with the alternate system and finished the items on the loss of center system procedure. The flap 20 degree landing and taxi-in were uneventful.

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Original NASA ASRS Text

Title: B767-3 FLT CREW HAS LOSS OF THE CTR HYD SYS DURING DSCNT INTO ORD.

Narrative: WHEN I ARRIVED BACK IN THE COCKPIT; THE FO'S BRIEFED ME THAT THE CTR HYD SYS QUANTITY HAD STARTED DROPPING SLOWLY JUST PRIOR TO THE TOP OF DSCNT. THEY HAD PERFORMED THE IRREGULAR OP FOR LOW HYD QUANTITY; AND HAD SHUT OFF THE CTR HYD PUMPS WITH THE QUANTITY AT .22. THEY HAD ALSO REVIEWED THE LOSS OF THE CTR HYD SYS IRREGULAR PROC. WE DISCUSSED A DIVERSION VERSUS CONTINUING TO ORD; AND DECIDED CONTINUING WOULD BE THE SAFEST COURSE OF ACTION BY GIVING US ENOUGH TIME TO THOROUGHLY TROUBLESHOOT AND BRIEF THE PROB. WE DISCUSSED ATTEMPTING TO LOWER THE LNDG GEAR WITH THE REMAINING FLUID; AND WHAT WOULD HAPPEN SHOULD THAT FAIL. WE THEN BRIEFED THE REMAINING ITEMS ON THE LOSS OF CTR SYS PROC; THE ALTERNATE GEAR EXTENSION AND THE ALTERNATE FLAP EXTENSION PROCS. FO; THE PF; AND AS I HAD JUST BEEN SOUND ASLEEP; I DECIDED THAT HAVING HIM CONTINUE TO FLY THE APCH AND LNDG WOULD PROBABLY BE THE SAFEST OPTION. AT THIS POINT; FO CONTACTED DISPATCH AND MAINT TO BRIEF THEM ON THE SITUATION; AND I BRIEFED THE FLT ATTENDANTS. I DID DECLARE A CABIN ADVISORY; AND TOLD THE FLT ATTENDANTS TO EXPECT A NORMAL LNDG WITH THE EXCEPTION THAT THE LNDG GEAR WOULD BE LOWERED EARLIER THAN USUAL AND THAT THE APCH SPD WOULD BE SLIGHTLY FASTER THAN NORMAL. I DECIDED THAT DECLARING AN EMER WITH ATC WAS NOT NECESSARY; BUT DID INFORM THEM OF THE SITUATION AND ASKED FOR A SLIGHTLY EXTENDED DOWNWIND/FINAL IN ORDER TO HAVE TIME TO ELECTRICALLY LOWER THE FLAPS. APPROX 20 MI FROM TOUCHDOWN WE ATTEMPTED TO LOWER THE GEAR NORMALLY. TURNING THE CTR SYS PUMPS ON RESULTED IN A CONTINUATION OF THE SLOW LEAK AND PUTTING THE GEAR HANDLE DOWN RESULTED IN THE EXTENSION OF ONLY THE NOSE GEAR. AT THIS POINT; WE SHUT THE CTR SYS OFF AND PERFORMED THE ALTERNATE GEAR EXTENSION PROC. SOME CTR SYS FLUID WAS REGAINED AFTER GEAR EXTENSION; BUT WE ELECTED TO EXTEND THE FLAPS WITH THE ALTERNATE SYS AND FINISHED THE ITEMS ON THE LOSS OF CTR SYS PROC. THE FLAP 20 DEG LNDG AND TAXI-IN WERE UNEVENTFUL.

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.