Narrative:

Departed at XA55. In first officer's pre taxi check, SOP is to switch green and blue hydraulic pumps to the automatic position and note pressure and quantity. Green and blue system were full and in the green range. 15-20 mins into the 50 min flight cruise at FL180, green hydraulic fluid level was noted in yellow arc (very low level) followed by a single chime warning fluid low level. Green system hydraulic pressure still remained in green range (3000 psi). QRH procedure led us to believe that if green system is lost totally, we would lose operation to the landing gear, nosewheel steering, rudder, outboard brake and flaps. Due to this, an emergency was declared, decision was made to continue to seattle, because seattle was the most suitable airport in point of time services, runway length etc. Decision was made to free-fall the landing gear per QRH. We were unable to determine the source of the leak and QRH procedure was to not lower the gear normally in this situation. Free-fall gear extension went normal, 3 greens. At this point, fluid was very low, but pressure still in green. On final to runway 16L at sea, flaps were selected to 25 degrees, came down normally. On landing, full reverse was applied and soon discovered we had nosewheel and braking power. Green system pressure still remained in green range. After engine shutdown, a large amount of hydraulic fluid covered the left wheel and engine cowling. Maintenance later determined the leak was due to a broken hydraulic line.

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Original NASA ASRS Text

Title: AN EMB120 FLC EXPERIENCED A MALFUNCTION OF THEIR GREEN HYD SYS AND CONTINUES ON TO DEST ARPT OF SEA, WA.

Narrative: DEPARTED AT XA55. IN FO'S PRE TAXI CHK, SOP IS TO SWITCH GREEN AND BLUE HYD PUMPS TO THE AUTO POS AND NOTE PRESSURE AND QUANTITY. GREEN AND BLUE SYS WERE FULL AND IN THE GREEN RANGE. 15-20 MINS INTO THE 50 MIN FLT CRUISE AT FL180, GREEN HYD FLUID LEVEL WAS NOTED IN YELLOW ARC (VERY LOW LEVEL) FOLLOWED BY A SINGLE CHIME WARNING FLUID LOW LEVEL. GREEN SYS HYD PRESSURE STILL REMAINED IN GREEN RANGE (3000 PSI). QRH PROC LED US TO BELIEVE THAT IF GREEN SYS IS LOST TOTALLY, WE WOULD LOSE OP TO THE LNDG GEAR, NOSEWHEEL STEERING, RUDDER, OUTBOARD BRAKE AND FLAPS. DUE TO THIS, AN EMER WAS DECLARED, DECISION WAS MADE TO CONTINUE TO SEATTLE, BECAUSE SEATTLE WAS THE MOST SUITABLE ARPT IN POINT OF TIME SVCS, RWY LENGTH ETC. DECISION WAS MADE TO FREE-FALL THE LNDG GEAR PER QRH. WE WERE UNABLE TO DETERMINE THE SOURCE OF THE LEAK AND QRH PROC WAS TO NOT LOWER THE GEAR NORMALLY IN THIS SIT. FREE-FALL GEAR EXTENSION WENT NORMAL, 3 GREENS. AT THIS POINT, FLUID WAS VERY LOW, BUT PRESSURE STILL IN GREEN. ON FINAL TO RWY 16L AT SEA, FLAPS WERE SELECTED TO 25 DEGS, CAME DOWN NORMALLY. ON LNDG, FULL REVERSE WAS APPLIED AND SOON DISCOVERED WE HAD NOSEWHEEL AND BRAKING PWR. GREEN SYS PRESSURE STILL REMAINED IN GREEN RANGE. AFTER ENG SHUTDOWN, A LARGE AMOUNT OF HYD FLUID COVERED THE L WHEEL AND ENG COWLING. MAINT LATER DETERMINED THE LEAK WAS DUE TO A BROKEN HYD LINE.

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.