B777-200 flying overwater in class ii airspace; indicated low hydraulic quantity in left system. Fli...

Attributes
ACN	744077
Time
Date	200706
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 32000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc
Operator	common carrier : air carrier
Make Model Name	B777-200
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 170 flight time total : 15000 flight time type : 3000
ASRS Report	744077
Person 2
Affiliation	company : air carrier
Function	flight crew : relief pilot
Experience	flight time last 90 days : 200 flight time total : 18000 flight time type : 3000
ASRS Report	743927
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment other aircraft equipment : eicas other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : landed as precaution flight crew : declared emergency other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

During cruise with relief crews already on rest break; a hydraulic quantity left message appeared. Fluid level indicated 0.35%. We immediately contacted company maintenance via dispatch and elected to turn off the left hydraulic pumps to conserve fluid. In consultation with dispatch and maintenance; a decision was made to divert to ZZZ. A request for clearance direct to ZZZ was made via HF and eventually confirmed via VHF with ZZZ1 center. No emergency was declared at this time; as we anticipated being able to repower the left hydraulic system with the remaining fluid prior to landing. Maintenance concurred. While en route to ZZZ we continuously monitored the hydraulic quantity; and noticed a slow but steady decrease in quantity despite the pumps being turned off. The center and right system operated normally. When our computations indicated that we might not have enough time to arrive in ZZZ before the left hydraulic quantity reached a level that could preclude regaining normal power to the system; we declared an emergency with ZZZ center. Men and equipment were standing by; and we made a normal approach; landing; and taxi to the gate with the left hydraulic system shut down. Left hydraulic system quantity reached zero just prior to landing. Center and right system remained normal.

Original NASA ASRS Text

Title: B777-200 FLYING OVERWATER IN CLASS II AIRSPACE; INDICATED LOW HYD QUANTITY IN LEFT SYSTEM. FLT CREW RETURNED AND DECLARED EMER FOR APCH AND LNDG.

Narrative: DURING CRUISE WITH RELIEF CREWS ALREADY ON REST BREAK; A HYD QUANTITY L MESSAGE APPEARED. FLUID LEVEL INDICATED 0.35%. WE IMMEDIATELY CONTACTED COMPANY MAINT VIA DISPATCH AND ELECTED TO TURN OFF THE L HYD PUMPS TO CONSERVE FLUID. IN CONSULTATION WITH DISPATCH AND MAINT; A DECISION WAS MADE TO DIVERT TO ZZZ. A REQUEST FOR CLRNC DIRECT TO ZZZ WAS MADE VIA HF AND EVENTUALLY CONFIRMED VIA VHF WITH ZZZ1 CTR. NO EMER WAS DECLARED AT THIS TIME; AS WE ANTICIPATED BEING ABLE TO REPOWER THE L HYD SYS WITH THE REMAINING FLUID PRIOR TO LNDG. MAINT CONCURRED. WHILE ENRTE TO ZZZ WE CONTINUOUSLY MONITORED THE HYD QUANTITY; AND NOTICED A SLOW BUT STEADY DECREASE IN QUANTITY DESPITE THE PUMPS BEING TURNED OFF. THE CTR AND R SYS OPERATED NORMALLY. WHEN OUR COMPUTATIONS INDICATED THAT WE MIGHT NOT HAVE ENOUGH TIME TO ARRIVE IN ZZZ BEFORE THE L HYD QUANTITY REACHED A LEVEL THAT COULD PRECLUDE REGAINING NORMAL PWR TO THE SYS; WE DECLARED AN EMER WITH ZZZ CTR. MEN AND EQUIP WERE STANDING BY; AND WE MADE A NORMAL APCH; LNDG; AND TAXI TO THE GATE WITH THE L HYD SYS SHUT DOWN. L HYD SYS QUANTITY REACHED ZERO JUST PRIOR TO LNDG. CTR AND R SYS REMAINED NORMAL.

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.

B777-200 flying overwater in class ii airspace; indicated low hydraulic quantity in left system. Flight crew returned and declared emergency for approach and landing.