SF340 FLT CREW FINDS PAPER STUCK TO INLET GUIDE VANE ON POST FLIGHT INSPECTION.

Narrative

AFTER LNDG; THE CAPT FOUND A PIECE OF PAPER IN THE L ENG INLET STUCK TO ONE OF THE INLET GUIDE VANES. THIS PIECE OF PAPER WAS NOT THERE DURING PREFLT AND WAS THEREFORE INGESTED SOMETIME DURING THE TAXI OR FLT. A REDUCED PWR TKOF WAS USED OUT OF ZZZ; TKOF WAS NORMAL; BOTH ENG TEMPS STAYED SOMEWHERE IN 800'S SO NO LIMITATIONS WERE EXCEEDED. AFTER COMPLETION OF THE AFTER TKOF CHKLIST; IT WAS NOTICED THAT THE CHARTED TORQUE COULD NOT BE REACHED DUE TO THE L ENG REACHING 840 DEGS ABOUT 3% SHY OF THE CHARTED TORQUE VALUE. THIS IS FAIRLY COMMON AND THE ACFT WAS PERFORMING NORMALLY SO I DIDN'T THINK ANYTHING OF IT. UPON REACHING A CRUISE ALT OF 12000 FT; I GAVE THE CAPT A PWR SETTING FROM THE CHARTS AND AGAIN IT WAS NOTICED THAT THE PWR COULD ONLY BE SET APPROX 4 OR 5 PERCENT BELOW CHARTED TORQUE TO COMPLY WITH THE 840 DEG LIMIT ON THE L ENG. ONCE AGAIN; NOT THAT UNCOMMON. A TREND CHK WAS NOT ACCOMPLISHED BECAUSE WE WERE ONLY AT OUR CRUISE ALT FOR A VERY SHORT PERIOD OF TIME BEFORE CTR GAVE US A DSCNT TO 10000 FT FOR TFC AVOIDANCE AND AN ON-COURSE CLRNC. IT WAS NOTICED DURING THE CRUISE CHKLIST THAT THE DELTA T WAS APPROX 50 DEGS TO THE L. BUT SINCE THE CAPT INFORMED ME DURING PREFLT THAT IT WAS RUNNING ANYWHERE FROM 19-33 DEGS TO THE L IN THE LAST FEW TREND CHKS IT DIDN'T SEEM UNREASONABLE. I JUST FIGURED THE ENG WAS GETTING CLOSE TO DERIVATIVE. NO ABNORMAL INDICATIONS; NOISES; OR PERFORMANCE ISSUES WERE NOTICED DURING THE ENTIRE FLT. NO LIMITATIONS WERE EXCEEDED. THE WHOLE FLT WAS NORMAL UNTIL THE CAPT FOUND THE PIECE OF PAPER IN THE ENG INLET DURING THE POSTFLT. MAINT WAS NOTIFIED; OUTSTATION MAINT SHOWED UP AND TOOK OUT THE PIECE OF PAPER. THE PIECE OF PAPER WAS PARTIALLY MISSING AND APPEARED TO BE A LUGGAGE DOCUMENT LIKELY PICKED UP WHILE ON THE GND IN ZZZ. MAINT ASKED THE FLT CREW IF WE AVOIDED THE NG AVOIDANCE RANGES; SINCE WE COULD NOT CONFIRM WHETHER OR NOT WE HAD; THE FLT DATA RECORDED WAS PULLED FOR ANALYSIS. THE EVENT OCCURRED BECAUSE FOD WAS INGESTED INTO OUR L ENG INTAKE; LIKELY WHILE CONDUCTING GND OPS.