Narrative:

On oct/xa/06; I was PIC of a learjet 35 on a routine far 135 charter. This flight originated and was supposed to end in ZZZ1; with a layover in ZZZ2. Although we left ZZZ1 at XA00L and ZZZ2 at XP45L on the same day; both the sic and I completed the necessary 10 hours rest period in a hotel between flts. The problem our flight incurred did not happen until reaching FL340 while climbing en route back to ZZZ1 (about XQ15L). Upon climbing through FL340; I noticed a low oil pressure light for the left engine. I then looked over to the associated engine gauges and all three looked normal. No increase in itt; N1; or N2. I then looked over to the left engine oil pressure gauge and saw it slowly decreasing. Looking towards the sic; I asked him to pull out the checklist for the low oil pressure light; while simultaneously pulling the left engine throttle to idle. At the time; we were flying in high level icing conditions with nacelle; wing; and stabilizer anti-icing devices on. I then asked ATC to level at FL350; but he suggested that FL360 would be more appropriate. After completing the short checklist; the sic handed me the checklist as I wanted to confirm its completion. By this time; our aircraft was stable and level at FL360. I shut down the left engine as the checklist called for; trying to prevent any aircraft damage that could have followed. I then asked ATC to descend and informed him of the situation. I did declare an emergency and I soon after asked ATC if he could suggest an airport nearby with a relatively long runway and good WX. He came back with ZZZ. I said fine and ATC gave us clearance to fly directly to ZZZ. During our descent to ZZZ; we completed several more checklists; including abnormal single-engine landing. As PIC; I also decided that ZZZ was not the best place for us to divert. 1) it was an air force base. 2) ATC informed us that the ceilings were 1500 ft overcast. 3) I was unsure the location could accommodate any maintenance for the aircraft. And 4) our passenger would not have an ideal way to continue their trip home from ZZZ; I chose to divert to ZZZ3; having previous knowledge of its characteristics and deeming it a safe place to land. We completed our approach and landing into ZZZ3; without any problems; except for our inability to turn on the runway lights using the pilot controled lighting. It took over 10 'clicks' to activate the lights. Having spent the better half of the day trying to rest for our late trip back to ZZZ1; I found that both our early and late hours during the trip was still a factor in my decision making abilities. My performance in shutting down the engine could have been expedited. Our decision to land at an airport without an open tower could be questioned. I can only say that I dealt with the situation as calmly as possible; taking full use of the knowledge of the area and trying to prevent a possible accident. I did not know for sure what other problems could have occurred in relation to the low oil pressure in the left engine. Lack of oil was an obvious reason; but could it have been something else. Could our preflight have missed something? This was my reasoning for not looking longer for a more suitable airport. I can say this experience changed the way I look at aviation; since it was my first encounter with a potentially fatal situation. All my training; whether it be in an actual aircraft or a simulator; did prepare me for this situation. However; one's physical condition always have a tremendous effect.

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Original NASA ASRS Text

Title: A LR35 CAPT RPTS DECLARING AN EMER AND DIVERTING TO A NEARBY ARPT FOLLOWING A LOW OIL PRESSURE WARNING. FATIGUE PLAYED A PART.

Narrative: ON OCT/XA/06; I WAS PIC OF A LEARJET 35 ON A ROUTINE FAR 135 CHARTER. THIS FLT ORIGINATED AND WAS SUPPOSED TO END IN ZZZ1; WITH A LAYOVER IN ZZZ2. ALTHOUGH WE LEFT ZZZ1 AT XA00L AND ZZZ2 AT XP45L ON THE SAME DAY; BOTH THE SIC AND I COMPLETED THE NECESSARY 10 HRS REST PERIOD IN A HOTEL BTWN FLTS. THE PROB OUR FLT INCURRED DID NOT HAPPEN UNTIL REACHING FL340 WHILE CLBING ENRTE BACK TO ZZZ1 (ABOUT XQ15L). UPON CLBING THROUGH FL340; I NOTICED A LOW OIL PRESSURE LIGHT FOR THE L ENG. I THEN LOOKED OVER TO THE ASSOCIATED ENG GAUGES AND ALL THREE LOOKED NORMAL. NO INCREASE IN ITT; N1; OR N2. I THEN LOOKED OVER TO THE L ENG OIL PRESSURE GAUGE AND SAW IT SLOWLY DECREASING. LOOKING TOWARDS THE SIC; I ASKED HIM TO PULL OUT THE CHKLIST FOR THE LOW OIL PRESSURE LIGHT; WHILE SIMULTANEOUSLY PULLING THE L ENG THROTTLE TO IDLE. AT THE TIME; WE WERE FLYING IN HIGH LEVEL ICING CONDITIONS WITH NACELLE; WING; AND STABILIZER ANTI-ICING DEVICES ON. I THEN ASKED ATC TO LEVEL AT FL350; BUT HE SUGGESTED THAT FL360 WOULD BE MORE APPROPRIATE. AFTER COMPLETING THE SHORT CHKLIST; THE SIC HANDED ME THE CHKLIST AS I WANTED TO CONFIRM ITS COMPLETION. BY THIS TIME; OUR ACFT WAS STABLE AND LEVEL AT FL360. I SHUT DOWN THE L ENG AS THE CHKLIST CALLED FOR; TRYING TO PREVENT ANY ACFT DAMAGE THAT COULD HAVE FOLLOWED. I THEN ASKED ATC TO DSND AND INFORMED HIM OF THE SITUATION. I DID DECLARE AN EMER AND I SOON AFTER ASKED ATC IF HE COULD SUGGEST AN ARPT NEARBY WITH A RELATIVELY LONG RWY AND GOOD WX. HE CAME BACK WITH ZZZ. I SAID FINE AND ATC GAVE US CLRNC TO FLY DIRECTLY TO ZZZ. DURING OUR DSCNT TO ZZZ; WE COMPLETED SEVERAL MORE CHKLISTS; INCLUDING ABNORMAL SINGLE-ENG LNDG. AS PIC; I ALSO DECIDED THAT ZZZ WAS NOT THE BEST PLACE FOR US TO DIVERT. 1) IT WAS AN AIR FORCE BASE. 2) ATC INFORMED US THAT THE CEILINGS WERE 1500 FT OVCST. 3) I WAS UNSURE THE LOCATION COULD ACCOMMODATE ANY MAINT FOR THE ACFT. AND 4) OUR PAX WOULD NOT HAVE AN IDEAL WAY TO CONTINUE THEIR TRIP HOME FROM ZZZ; I CHOSE TO DIVERT TO ZZZ3; HAVING PREVIOUS KNOWLEDGE OF ITS CHARACTERISTICS AND DEEMING IT A SAFE PLACE TO LAND. WE COMPLETED OUR APCH AND LNDG INTO ZZZ3; WITHOUT ANY PROBS; EXCEPT FOR OUR INABILITY TO TURN ON THE RWY LIGHTS USING THE PLT CTLED LIGHTING. IT TOOK OVER 10 'CLICKS' TO ACTIVATE THE LIGHTS. HAVING SPENT THE BETTER HALF OF THE DAY TRYING TO REST FOR OUR LATE TRIP BACK TO ZZZ1; I FOUND THAT BOTH OUR EARLY AND LATE HRS DURING THE TRIP WAS STILL A FACTOR IN MY DECISION MAKING ABILITIES. MY PERFORMANCE IN SHUTTING DOWN THE ENG COULD HAVE BEEN EXPEDITED. OUR DECISION TO LAND AT AN ARPT WITHOUT AN OPEN TWR COULD BE QUESTIONED. I CAN ONLY SAY THAT I DEALT WITH THE SITUATION AS CALMLY AS POSSIBLE; TAKING FULL USE OF THE KNOWLEDGE OF THE AREA AND TRYING TO PREVENT A POSSIBLE ACCIDENT. I DID NOT KNOW FOR SURE WHAT OTHER PROBS COULD HAVE OCCURRED IN RELATION TO THE LOW OIL PRESSURE IN THE L ENG. LACK OF OIL WAS AN OBVIOUS REASON; BUT COULD IT HAVE BEEN SOMETHING ELSE. COULD OUR PREFLT HAVE MISSED SOMETHING? THIS WAS MY REASONING FOR NOT LOOKING LONGER FOR A MORE SUITABLE ARPT. I CAN SAY THIS EXPERIENCE CHANGED THE WAY I LOOK AT AVIATION; SINCE IT WAS MY FIRST ENCOUNTER WITH A POTENTIALLY FATAL SITUATION. ALL MY TRAINING; WHETHER IT BE IN AN ACTUAL ACFT OR A SIMULATOR; DID PREPARE ME FOR THIS SITUATION. HOWEVER; ONE'S PHYSICAL CONDITION ALWAYS HAVE A TREMENDOUS EFFECT.

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