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

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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.