Narrative:

Flight XXX a charter flown by xyz airlines, from ewr to nassau. About 30 mins after takeoff, the so informed me that the #1 engine oil quantity was decreasing slowly. We consulted the flight manual which referred no action until oil temperature or pressure reacted. Since all engines were svced prior to departure, we suspected a bad oil quantity gauge or bad sending unit. At this time the so and I decided a potentially serious problem or a catastrophic engine loss could be averted if we knew whether the gauge was bad. With my ok, he switched the #1 and #2 oil quantity gauges, a simple procedure involving 1 screw and a knurled knob connector. This troubleshooting indicated that the gauge was accurate and we were indeed losing oil quantity. Gauges were returned to their original position and shortly thereafter we began preparation for loss of that engine. Because we were able to eliminate the possibility of a bad gauge we were not surprised when the oil pressure dropped and following flight manual procedures the engine was shutdown. An emergency was declared and an uneventful 2 engine landing was made. My point of this report is that possibly swapping oil quantity gauges may be construed by the FAA as unauthorized maintenance when our intent was merely to analyze the situation and to be prepared in the event of loss of the engine. I feel our troubleshooting was correct and never an attempt at unauthorized maintenance.

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Original NASA ASRS Text

Title: ACR PIC 'FESSES UP TO SWAPPING OIL INDICATOR GAUGES TO SEE IF A FAULT LIES WITHIN THE ERRANT GAUGE.

Narrative: FLT XXX A CHARTER FLOWN BY XYZ AIRLINES, FROM EWR TO NASSAU. ABOUT 30 MINS AFTER TKOF, THE SO INFORMED ME THAT THE #1 ENG OIL QUANTITY WAS DECREASING SLOWLY. WE CONSULTED THE FLT MANUAL WHICH REFERRED NO ACTION UNTIL OIL TEMP OR PRESSURE REACTED. SINCE ALL ENGS WERE SVCED PRIOR TO DEP, WE SUSPECTED A BAD OIL QUANTITY GAUGE OR BAD SENDING UNIT. AT THIS TIME THE SO AND I DECIDED A POTENTIALLY SERIOUS PROBLEM OR A CATASTROPHIC ENG LOSS COULD BE AVERTED IF WE KNEW WHETHER THE GAUGE WAS BAD. WITH MY OK, HE SWITCHED THE #1 AND #2 OIL QUANTITY GAUGES, A SIMPLE PROC INVOLVING 1 SCREW AND A KNURLED KNOB CONNECTOR. THIS TROUBLESHOOTING INDICATED THAT THE GAUGE WAS ACCURATE AND WE WERE INDEED LOSING OIL QUANTITY. GAUGES WERE RETURNED TO THEIR ORIGINAL POS AND SHORTLY THEREAFTER WE BEGAN PREPARATION FOR LOSS OF THAT ENG. BECAUSE WE WERE ABLE TO ELIMINATE THE POSSIBILITY OF A BAD GAUGE WE WERE NOT SURPRISED WHEN THE OIL PRESSURE DROPPED AND FOLLOWING FLT MANUAL PROCS THE ENG WAS SHUTDOWN. AN EMER WAS DECLARED AND AN UNEVENTFUL 2 ENG LNDG WAS MADE. MY POINT OF THIS RPT IS THAT POSSIBLY SWAPPING OIL QUANTITY GAUGES MAY BE CONSTRUED BY THE FAA AS UNAUTHORIZED MAINT WHEN OUR INTENT WAS MERELY TO ANALYZE THE SITUATION AND TO BE PREPARED IN THE EVENT OF LOSS OF THE ENG. I FEEL OUR TROUBLESHOOTING WAS CORRECT AND NEVER AN ATTEMPT AT UNAUTHORIZED MAINT.

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.