Narrative:

I chose to not shut down an engine when I should have. We were on approach into msp on the eau 7 arrival just outside of zaske descending from 11000 ft to 10000 ft and slowing from 290 KTS to 210 KTS. The oil low pressure light for #2 engine illuminated. We immediately looked at the oil pressure gauge and noted that it was ticking, fluctuating between approximately 35-60 psi. We consulted the QRH which, for that light, asks one question: is the oil pressure gauge in the red sector or below 50 psi when N1 is above 80%? If you answer yes, you are directed to shut down engine. If you answer no, it states to continue, monitoring engine parameters. I answered no and felt that all engine parameters were normal (N1, egt, N2). We were less than 10 mins from landing. Thus, I continued with approach and we made the landing without incident. However, it was determined by our maintenance department that because the oil pressure light illuminated and was on for more than 60 seconds, it was safest to replace the entire engine. Had I shut down the engine in-flight, we may have saved an engine replacement. Also, the 2 remaining oil gauges (temperature and quantity), although not mentioned in the QRH, should have been considered. Oil temperature remained normal throughout, but oil quantity was nearing zero. In hindsight, because 3 of the 4 oil indications were abnormal, I should have shut down the engine, although the QRH suggested to continue based on oil psi. Although fluctuating, I never noted oil psi outside the green range and with each power adjustment, oil psi would correspond (higher power, higher psi, lower power, lower psi). In addition with power increases, the oil low pressure light would extinguish. With an intermittent low pressure light and a ticking gauge, my initial thought was malfunctioning gauges rather than a true engine problem. It turns out, my instinct and interpretation of the QRH were both a little skewed.

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Original NASA ASRS Text

Title: BA46 PIC FAILS TO SHUT DOWN #2 ENG AFTER THE LOW OIL PRESSURE LIGHT ILLUMINATES WITH ASSOCIATED LOW OIL SUPPLY ON APCH TO MSP.

Narrative: I CHOSE TO NOT SHUT DOWN AN ENG WHEN I SHOULD HAVE. WE WERE ON APCH INTO MSP ON THE EAU 7 ARR JUST OUTSIDE OF ZASKE DSNDING FROM 11000 FT TO 10000 FT AND SLOWING FROM 290 KTS TO 210 KTS. THE OIL LOW PRESSURE LIGHT FOR #2 ENG ILLUMINATED. WE IMMEDIATELY LOOKED AT THE OIL PRESSURE GAUGE AND NOTED THAT IT WAS TICKING, FLUCTUATING BTWN APPROX 35-60 PSI. WE CONSULTED THE QRH WHICH, FOR THAT LIGHT, ASKS ONE QUESTION: IS THE OIL PRESSURE GAUGE IN THE RED SECTOR OR BELOW 50 PSI WHEN N1 IS ABOVE 80%? IF YOU ANSWER YES, YOU ARE DIRECTED TO SHUT DOWN ENG. IF YOU ANSWER NO, IT STATES TO CONTINUE, MONITORING ENG PARAMETERS. I ANSWERED NO AND FELT THAT ALL ENG PARAMETERS WERE NORMAL (N1, EGT, N2). WE WERE LESS THAN 10 MINS FROM LNDG. THUS, I CONTINUED WITH APCH AND WE MADE THE LNDG WITHOUT INCIDENT. HOWEVER, IT WAS DETERMINED BY OUR MAINT DEPT THAT BECAUSE THE OIL PRESSURE LIGHT ILLUMINATED AND WAS ON FOR MORE THAN 60 SECONDS, IT WAS SAFEST TO REPLACE THE ENTIRE ENG. HAD I SHUT DOWN THE ENG INFLT, WE MAY HAVE SAVED AN ENG REPLACEMENT. ALSO, THE 2 REMAINING OIL GAUGES (TEMP AND QUANTITY), ALTHOUGH NOT MENTIONED IN THE QRH, SHOULD HAVE BEEN CONSIDERED. OIL TEMP REMAINED NORMAL THROUGHOUT, BUT OIL QUANTITY WAS NEARING ZERO. IN HINDSIGHT, BECAUSE 3 OF THE 4 OIL INDICATIONS WERE ABNORMAL, I SHOULD HAVE SHUT DOWN THE ENG, ALTHOUGH THE QRH SUGGESTED TO CONTINUE BASED ON OIL PSI. ALTHOUGH FLUCTUATING, I NEVER NOTED OIL PSI OUTSIDE THE GREEN RANGE AND WITH EACH PWR ADJUSTMENT, OIL PSI WOULD CORRESPOND (HIGHER PWR, HIGHER PSI, LOWER PWR, LOWER PSI). IN ADDITION WITH PWR INCREASES, THE OIL LOW PRESSURE LIGHT WOULD EXTINGUISH. WITH AN INTERMITTENT LOW PRESSURE LIGHT AND A TICKING GAUGE, MY INITIAL THOUGHT WAS MALFUNCTIONING GAUGES RATHER THAN A TRUE ENG PROB. IT TURNS OUT, MY INSTINCT AND INTERP OF THE QRH WERE BOTH A LITTLE SKEWED.

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.