Narrative:

While climbing through about FL270; the number 1 hydraulic system quantity rapidly dropped to zero. We accomplished the hydraulic qty low 1 checklist which basically has you 'continue normal operation'; with the decision of running the backup demand pump up to the crew. We conferred with dispatch; maintenance control as well as the fleet technical specialist; to determine if we were ok to continue to [destination] and see what we were able to run with the remaining demand pump when we descended into [destination] . The concerns - as addressed in the hydraulic press system 1 checklist include no center autopilot; left outboard elevator being inoperative as well as the trailing edge flaps operating in secondary mode. Also we may have no nose and body gear steering and have to drop the gear using the alternate method and no number 1 thrust reverser.we were concerned with the inability of the demand pump for the number one hydraulic system to handle all of these functions and expressed our concern to maintenance control. The answer back was that the remaining 1.2 gallons of fluid below the standpipe would adequately supply the demand for the flaps/gear/steering/etc as long as we had standpipe fluid. We appeared to have adequate standpipe fluid since the demand pump maintained 3;000 psi when it was selected on. Fleet technical said there was 'no limitations on the demand pump'; and 'that following the checklist would be best and turn the pumps back on prior to landing and the system should operate as indicated'. He also cautioned about configuring too late.we knew we had about three potential scenarios when we started out descent for landing at [destination]. The weather was a gusty crosswind with light rain with 1000 feet; ceiling for our arrival. We briefed the flight attendants as to our potential scenarios and said we would let them know which one it was going to be upon approach into [destination] . Scenario 2; which indeed played out; was the inability of the demand pump to provide adequate pressure for nose/body gear extension and steering as well as alternate gear extension and trailing edge flap movement in secondary mode. We accomplished the hydraulic press system 1 checklist on approach and landed normally except for the requirement to get towed clear of the runway. We let [destination] control know when we were in our holding pattern and told them we had the fuel to place us in the landing sequence so as to cause the least amount of disruption to their operations. Dispatch quickly arranged for a tow off the runway and we landed after configuring and accomplishing all required checklists.all sops were complied with; the aircraft was exceptionally flown by the first officer and he configured absolutely perfectly so as to conduct a safe; stabilized approach. The passengers were informed as to our remaining on the runway for an abnormal period and tow to the gate. We fully debriefed [destination] maintenance upon our arrival.

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Original NASA ASRS Text

Title: B747 Captain experienced the loss of the number one hydraulic system climbing through FL270 due to fluid loss. After conferring with Maintenance Control the crew elects to continue to destination. A normal landing ensued with inoperative nose wheel steering and the aircraft is towed to the gate.

Narrative: While climbing through about FL270; the number 1 hydraulic system quantity rapidly dropped to zero. We accomplished the HYD QTY LOW 1 checklist which basically has you 'continue normal operation'; with the decision of running the backup demand pump up to the crew. We conferred with Dispatch; Maintenance Control as well as the fleet technical specialist; to determine if we were OK to continue to [destination] and see what we were able to run with the remaining demand pump when we descended into [destination] . The concerns - as addressed in the HYD PRESS SYS 1 checklist include no center autopilot; left outboard elevator being inoperative as well as the trailing edge flaps operating in secondary mode. Also we may have no nose and body gear steering and have to drop the gear using the alternate method and no number 1 thrust reverser.We were concerned with the inability of the demand pump for the number one hydraulic system to handle all of these functions and expressed our concern to Maintenance Control. The answer back was that the remaining 1.2 gallons of fluid below the standpipe would adequately supply the demand for the flaps/gear/steering/etc as long as we had standpipe fluid. We appeared to have adequate standpipe fluid since the demand pump maintained 3;000 psi when it was selected on. Fleet technical said there was 'no limitations on the demand pump'; and 'that following the checklist would be best and turn the pumps back on prior to landing and the system should operate as indicated'. He also cautioned about configuring too late.We knew we had about three potential scenarios when we started out descent for landing at [destination]. The weather was a gusty crosswind with light rain with 1000 feet; ceiling for our arrival. We briefed the flight attendants as to our potential scenarios and said we would let them know which one it was going to be upon approach into [destination] . Scenario 2; which indeed played out; was the inability of the demand pump to provide adequate pressure for nose/body gear extension and steering as well as alternate gear extension and trailing edge flap movement in secondary mode. We accomplished the HYD PRESS SYS 1 checklist on approach and landed normally except for the requirement to get towed clear of the runway. We let [destination] control know when we were in our holding pattern and told them we had the fuel to place us in the landing sequence so as to cause the least amount of disruption to their operations. Dispatch quickly arranged for a tow off the runway and we landed after configuring and accomplishing all required checklists.All SOPs were complied with; the aircraft was exceptionally flown by the First Officer and he configured absolutely perfectly so as to conduct a safe; stabilized approach. The passengers were informed as to our remaining on the runway for an abnormal period and tow to the gate. We fully debriefed [destination] Maintenance upon our arrival.

Data retrieved from NASA's ASRS site 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.