An MD80 pilot report of a left engine oil leak was checked and found ok for service. Engine oil/air ...

Attributes
ACN	639585
Time
Date	200412
Day	Thu
Place
Locale Reference	airport : zzz.airport
State Reference	US
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	ground : parked ground : maintenance
Person 1
Affiliation	company : air carrier
Function	maintenance : technician
ASRS Report	639585
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment other aircraft equipment : left engine oil quantity other flight crewa other flight crewb
Consequence	other other
Supplementary
Problem Areas	Flight Crew Human Performance Maintenance Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

During routine walkaround, technician noted evidence of oil on the bottom of cowl. Nothing to make me think we had anything other than the typical MD80 oil on the lower cowl. The captain said it was noticed on the walkaround and he was going to write it up. I told him it was 'typical.' he stated he was obligated to put it in the book. A quick check of the cockpit oil quantity indicators showed both engines full at 16 quarts. I went to the computer terminal and checked history for 100 days. No reports of oil leaking on the #1 engine. I opened the cowling, visually inspected the components for obvious leaks, none noted, I also checked the CSD oil quantity sight gauge and it indicated full. A partner ran the engine at idle for several mins, no leakage found. The engine was shut down, the cowling closed and wiped off. The logbook was signed off by myself. The MD80 has an air-oil separator that emits an oil mist overboard. The MD80 also has a vent to cowl drain seal that provides a poor seal, thus venting much of the oil mist into the cowling which to the uninitiated could be perceived as an oil leak. Often the plate that matches up to the engine vent gets distorted and further exasperates the poor fit of the cowl seal.

Original NASA ASRS Text

Title: AN MD80 PLT RPT OF A L ENG OIL LEAK WAS CHKED AND FOUND OK FOR SVC. ENG OIL/AIR SEPARATOR VAPOR COLLECTS ON ENG VENT COWL SEAL AND APPEARS AS A LEAK.

Narrative: DURING ROUTINE WALKAROUND, TECHNICIAN NOTED EVIDENCE OF OIL ON THE BOTTOM OF COWL. NOTHING TO MAKE ME THINK WE HAD ANYTHING OTHER THAN THE TYPICAL MD80 OIL ON THE LOWER COWL. THE CAPT SAID IT WAS NOTICED ON THE WALKAROUND AND HE WAS GOING TO WRITE IT UP. I TOLD HIM IT WAS 'TYPICAL.' HE STATED HE WAS OBLIGATED TO PUT IT IN THE BOOK. A QUICK CHK OF THE COCKPIT OIL QUANTITY INDICATORS SHOWED BOTH ENGS FULL AT 16 QUARTS. I WENT TO THE COMPUTER TERMINAL AND CHKED HISTORY FOR 100 DAYS. NO RPTS OF OIL LEAKING ON THE #1 ENG. I OPENED THE COWLING, VISUALLY INSPECTED THE COMPONENTS FOR OBVIOUS LEAKS, NONE NOTED, I ALSO CHKED THE CSD OIL QUANTITY SIGHT GAUGE AND IT INDICATED FULL. A PARTNER RAN THE ENG AT IDLE FOR SEVERAL MINS, NO LEAKAGE FOUND. THE ENG WAS SHUT DOWN, THE COWLING CLOSED AND WIPED OFF. THE LOGBOOK WAS SIGNED OFF BY MYSELF. THE MD80 HAS AN AIR-OIL SEPARATOR THAT EMITS AN OIL MIST OVERBOARD. THE MD80 ALSO HAS A VENT TO COWL DRAIN SEAL THAT PROVIDES A POOR SEAL, THUS VENTING MUCH OF THE OIL MIST INTO THE COWLING WHICH TO THE UNINITIATED COULD BE PERCEIVED AS AN OIL LEAK. OFTEN THE PLATE THAT MATCHES UP TO THE ENG VENT GETS DISTORTED AND FURTHER EXASPERATES THE POOR FIT OF THE COWL SEAL.

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.

An MD80 pilot report of a left engine oil leak was checked and found ok for service. Engine oil/air separator vapor collects on engine vent cowl seal and appears as a leak.