Narrative:

Departed for a flight to syr. Takeoff and climb phase of flight were normal. WX was clear with few cloud build-ups; no turbulence encountered. Leveloff at FL410 was normal; cruise checklist completed; and trend monitoring was completed. Cruise power was set at 795 itt and normal crew monitoring of flight continued. At 1 hour into flight a very noticeable (sudden) sound change started. A quick walk to rear lavatory section of aircraft confirmed sound appeared to be located in tail area of aircraft. Movement of left and right thrust levers confirmed noise was engine induced and idented as the left (#1) engine. A time span of about 5 mins from when noise started; a noticeable itt fluctuation started caused both an increase and decrease; but manly a decrease in itt. A flight level change was requested from FL410 to FL310; and preparation was begun for diverting to an alternate airport; and precautionary in-flight shutdown of the #1 engine. When power was reduced on both engines for start of descent; left engine stabilized to normal indication; same as engine #2. Engine noise from #1 engine reduced to a level that was not heard. Descent rate was set at 1500 FPM; all indications of engine now normal. Descending and passing FL370; left (#1) engine itt again began to swing; increase to decrease; but more to decrease which lasted about 5-10 seconds; at which time engine began to roll back to shutdown condition. Center was informed of the problem we had and an emergency was declared. Vectors were given for ZZZ. Flight crew performed checklist as appropriate from the QRH; and prepared the aircraft for landing. Landing was made on runway 5L and was uneventful. Aircraft was taxied to the ramp; initial inspection by flight crew showed nothing abnormal and no other information is available at this time.

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Original NASA ASRS Text

Title: LJ40 SUFFERS FAILURE OF LEFT ENGINE. DIVERTS TO NEAREST SUITABLE ARPT.

Narrative: DEPARTED FOR A FLT TO SYR. TKOF AND CLB PHASE OF FLT WERE NORMAL. WX WAS CLR WITH FEW CLOUD BUILD-UPS; NO TURB ENCOUNTERED. LEVELOFF AT FL410 WAS NORMAL; CRUISE CHKLIST COMPLETED; AND TREND MONITORING WAS COMPLETED. CRUISE PWR WAS SET AT 795 ITT AND NORMAL CREW MONITORING OF FLT CONTINUED. AT 1 HR INTO FLT A VERY NOTICEABLE (SUDDEN) SOUND CHANGE STARTED. A QUICK WALK TO REAR LAVATORY SECTION OF ACFT CONFIRMED SOUND APPEARED TO BE LOCATED IN TAIL AREA OF ACFT. MOVEMENT OF L AND R THRUST LEVERS CONFIRMED NOISE WAS ENG INDUCED AND IDENTED AS THE L (#1) ENG. A TIME SPAN OF ABOUT 5 MINS FROM WHEN NOISE STARTED; A NOTICEABLE ITT FLUCTUATION STARTED CAUSED BOTH AN INCREASE AND DECREASE; BUT MANLY A DECREASE IN ITT. A FLT LEVEL CHANGE WAS REQUESTED FROM FL410 TO FL310; AND PREPARATION WAS BEGUN FOR DIVERTING TO AN ALTERNATE ARPT; AND PRECAUTIONARY INFLT SHUTDOWN OF THE #1 ENG. WHEN PWR WAS REDUCED ON BOTH ENGS FOR START OF DSCNT; L ENG STABILIZED TO NORMAL INDICATION; SAME AS ENG #2. ENG NOISE FROM #1 ENG REDUCED TO A LEVEL THAT WAS NOT HEARD. DSCNT RATE WAS SET AT 1500 FPM; ALL INDICATIONS OF ENG NOW NORMAL. DSNDING AND PASSING FL370; L (#1) ENG ITT AGAIN BEGAN TO SWING; INCREASE TO DECREASE; BUT MORE TO DECREASE WHICH LASTED ABOUT 5-10 SECONDS; AT WHICH TIME ENG BEGAN TO ROLL BACK TO SHUTDOWN CONDITION. CTR WAS INFORMED OF THE PROB WE HAD AND AN EMER WAS DECLARED. VECTORS WERE GIVEN FOR ZZZ. FLT CREW PERFORMED CHKLIST AS APPROPRIATE FROM THE QRH; AND PREPARED THE ACFT FOR LNDG. LNDG WAS MADE ON RWY 5L AND WAS UNEVENTFUL. ACFT WAS TAXIED TO THE RAMP; INITIAL INSPECTION BY FLT CREW SHOWED NOTHING ABNORMAL AND NO OTHER INFO IS AVAILABLE AT THIS TIME.

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.