Fuel-oil cooler failure results in oil loss on B777-200.

Attributes
ACN	809256
Time
Date	200809
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B777-200
Operating Under FAR Part	Part 121
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	maintenance : technician
ASRS Report	809256
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : eng oil qty
Resolutory Action	flight crew : diverted to another airport
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

At the time of filling out this report the outcome is not known. Oil service was required. I serviced oil because it was below minimum. I received word of the aircraft diverting back to ZZZ due to loss of oil quantity on engine that was serviced. At this point the outcome is not known. The aircraft is still enroute back.callback conversation with reporter revealed the following information: reporter stated the B777-200 oil quantity loss on #1 engine was due to a failed fuel-oil cooler. Reporter also stated there seems to be a problem with the engine fuel-oil coolers leaking internally; where the oil will leak into the fuel side of the cooler. That's why; whenever an engine is showing increasing oil consumption; an engine will be run and checked for oil leaks. If no visible external oil leak can be found or noticed; even in the exhaust section; and can't find reason for the continued oil loss; then maintenance will change the cooler. Reporter stated; in many cases; this seems to correct the condition.

Original NASA ASRS Text

Title: FUEL-OIL COOLER FAILURE RESULTS IN OIL LOSS ON B777-200.

Narrative: AT THE TIME OF FILLING OUT THIS RPT THE OUTCOME IS NOT KNOWN. OIL SERVICE WAS REQUIRED. I SERVICED OIL BECAUSE IT WAS BELOW MINIMUM. I RECEIVED WORD OF THE ACFT DIVERTING BACK TO ZZZ DUE TO LOSS OF OIL QUANTITY ON ENGINE THAT WAS SERVICED. AT THIS POINT THE OUTCOME IS NOT KNOWN. THE ACFT IS STILL ENROUTE BACK.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THE B777-200 OIL QUANTITY LOSS ON #1 ENGINE WAS DUE TO A FAILED FUEL-OIL COOLER. RPTR ALSO STATED THERE SEEMS TO BE A PROBLEM WITH THE ENGINE FUEL-OIL COOLERS LEAKING INTERNALLY; WHERE THE OIL WILL LEAK INTO THE FUEL SIDE OF THE COOLER. THAT'S WHY; WHENEVER AN ENGINE IS SHOWING INCREASING OIL CONSUMPTION; AN ENGINE WILL BE RUN AND CHECKED FOR OIL LEAKS. IF NO VISIBLE EXTERNAL OIL LEAK CAN BE FOUND OR NOTICED; EVEN IN THE EXHAUST SECTION; AND CAN'T FIND REASON FOR THE CONTINUED OIL LOSS; THEN MAINT WILL CHANGE THE COOLER. RPTR STATED; IN MANY CASES; THIS SEEMS TO CORRECT THE CONDITION.

Data retrieved from NASA's ASRS site as of May 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.