B767 aircraft had hydraulic leak, but maintenance was unable to find source. Suspecting the leak was...

Attributes
ACN	371916
Time
Date	199706
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : fra
State Reference	FO
Altitude	agl bound lower : 0 agl bound upper : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B767 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	371916
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Aircraft had reported center system hydraulic leak at fra. Maintenance unable to find source of leak and suspected a seal in the right landing gear had cold soaked and later resealed itself at warmer temperature. Aircraft was svced and departed at approximately 390000 pounds. After about 90 mins of flight, all 3 hydraulic system quantities had decreased slightly. #1 system quantity remained the same for balance of flight. #2 and #3 system continued to slowly decrease. WX was good at kef sfj yfb yyr yul yyz and ord. Based on timed very slow fluid loss rate flight continued to ord. Aircraft does not have a fuel dump system. A heavy overweight 20 degree flap landing in event of center system failure was considered. Flight landed at ord with 3 normal hydraulic system. Center system quantity was above refill tick. Right system was below refill tick. The landing was planned for possible center system failure when the gear was lowered and for possible right system failure if there was a brake problem. As the brakes were parked at the gate the right system went to zero. The first officer and international officer performance was outstanding as we considered all possible options. The decisions were mine.

Original NASA ASRS Text

Title: B767 ACFT HAD HYD LEAK, BUT MAINT WAS UNABLE TO FIND SOURCE. SUSPECTING THE LEAK WAS FROM LNDG GEAR SEAL WHICH RESEALED, ACFT WAS DISPATCHED FOR OVERWATER FLT. ENRTE HYDS LEAKED SLOWLY, BUT NOT ENOUGH TO DIVERT.

Narrative: ACFT HAD RPTED CTR SYS HYD LEAK AT FRA. MAINT UNABLE TO FIND SOURCE OF LEAK AND SUSPECTED A SEAL IN THE R LNDG GEAR HAD COLD SOAKED AND LATER RESEALED ITSELF AT WARMER TEMP. ACFT WAS SVCED AND DEPARTED AT APPROX 390000 LBS. AFTER ABOUT 90 MINS OF FLT, ALL 3 HYD SYS QUANTITIES HAD DECREASED SLIGHTLY. #1 SYS QUANTITY REMAINED THE SAME FOR BAL OF FLT. #2 AND #3 SYS CONTINUED TO SLOWLY DECREASE. WX WAS GOOD AT KEF SFJ YFB YYR YUL YYZ AND ORD. BASED ON TIMED VERY SLOW FLUID LOSS RATE FLT CONTINUED TO ORD. ACFT DOES NOT HAVE A FUEL DUMP SYS. A HVY OVERWT 20 DEG FLAP LNDG IN EVENT OF CTR SYS FAILURE WAS CONSIDERED. FLT LANDED AT ORD WITH 3 NORMAL HYD SYS. CTR SYS QUANTITY WAS ABOVE REFILL TICK. R SYS WAS BELOW REFILL TICK. THE LNDG WAS PLANNED FOR POSSIBLE CTR SYS FAILURE WHEN THE GEAR WAS LOWERED AND FOR POSSIBLE R SYS FAILURE IF THERE WAS A BRAKE PROB. AS THE BRAKES WERE PARKED AT THE GATE THE R SYS WENT TO ZERO. THE FO AND INTL OFFICER PERFORMANCE WAS OUTSTANDING AS WE CONSIDERED ALL POSSIBLE OPTIONS. THE DECISIONS WERE MINE.

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.

B767 aircraft had hydraulic leak, but maintenance was unable to find source. Suspecting the leak was from landing gear seal which resealed, aircraft was dispatched for overwater flight. En route hydraulics leaked slowly, but not enough to divert.