A C182L PLT DID NOT REALIZE HE HAD BUILT UP CARB ICE WHILE FLYING 15 NM N OF THS VOR.

Narrative

I WAS FLYING A C182L ON A PART 91 IFR FLT PLAN FROM BFD TO HGR. WHILE IN LEVEL CRUISE AT 5000 FT IN CLR; UNLIMITED VISIBILITY CONDITIONS; ON V501 APPROX 15 NM N OF THE THS VOR; THE ENG BEGAN TO RUN A LITTLE ROUGH. MANIFOLD PRESSURE WAS DOWN APPROX 1 INCH; AND RPM WITHIN 50 OF THE CRUISE SETTING THAT I WAS USING. I CHKED THE OIL TEMP; OIL PRESSURE; AND CHT; WITH ALL INDICATIONS NORMAL. I PUSHED THE MIXTURE TO FULL RICH AND PULLED CARB HEAT TO FULL ON; AND REDUCED PWR TO APPROX 18-19 INCHES ON THE MANIFOLD. AT THIS TIME; I TOLD THE ZOB CTLR THAT OUR ENG WAS RUNNING ROUGH AND ASKED THE LOCATION OF THE NEAREST ARPT. HE RESPONDED THAT AOO WAS W AT 16 NM. MY FRIEND SAID THAT THE GPS RECEIVER SHOWED MUU AT 040 DEGS AT 9 NM. I BEGAN A TURN IN THAT DIRECTION AND INFORMED THE CTLR THAT OUR GPS SHOWED MUU NE (I MAY HAVE USED THE ACTUAL BEARING) AT 9 MI. SHORTLY; THE CTLR CAME BACK AND CONFIRMED THAT MUU WAS 8 MI AWAY. BY THIS TIME; WE HAD COMPLETED OUR TURN; AND I TOLD MY FRIEND I THOUGHT I HAD THE ARPT IN SIGHT. SLIGHTLY AFTER THAT; I INFORMED THE CTLR THAT I HAD THE FIELD IN SIGHT. HE SAID THAT HE WOULD CALL THE ARPT MGR TO INFORM HIM THAT WE WERE INBOUND. AS WE DSNDED THROUGH ABOUT 3000 FT; BOTH MY FRIENDS AND I NOTED THAT THE ENG WAS NOW RUNNING SMOOTHLY. ALL ENG INDICATIONS WERE NORMAL. I RAN THE THROTTLE UP TO CRUISE PWR; AND IT ACCELERATED NORMALLY AND WAS RUNNING SMOOTHLY. AT THIS TIME; WE AGREED THAT WE HAD CARB ICE; AND THAT IT WAS NOW CLR. BUT WITH AN ARPT RWY IN SIGHT AND BEING ALREADY SET UP FOR A STRAIGHT-IN APCH; I ELECTED TO CONTINUE WITH THE LNDG. I INFORMED THE CTLR THAT WE HAD THE FIELD MADE AND WERE SWITCHING TO CTAF. HE ASKED IF WE WANTED TO CANCEL OUR FLT PLAN; AND I SAID WE'D CALL HIM WHEN ON THE GND; AND HE GAVE US HIS PHONE NUMBER. WE THEN SWITCHED TO CTAF AND BROADCAST OUR POS AND INTENTIONS. THE FLT ENDED WITH AN UNEVENTFUL LNDG. UPON TAXIING TO THE PARKING RAMP; WE DID A COMPLETE POSTFLT INSPECTION OF THE ENG; AND EVERYTHING WAS NORMAL -- OIL WAS AT 9.5 QUARTS AND CLR; NOTHING DRIPPING IN OR FROM THE COWLING; EXHAUST STACK CLEAN; ETC. AFTER APPROX 30 MINS; WE STARTED THE PLANE AND PERFORMED A STANDARD PREFLT RUN-UP WITH ALL INDICATIONS NORMAL. I THEN ACCELERATED THE ENG TO CRUISE AND THEN FULL PWR; WITH ALL INDICATIONS REMAINING NORMAL AND THE ENG ACCELERATING SMOOTHLY AND NORMALLY TO FULL RATED PWR. WE THEN SHUT THE PLANE DOWN; AND AGAIN DID A COMPLETE POSTFLT INSPECTION; WITH EVERYTHING NORMAL. I DECIDED TO DO ONE MORE STANDARD; FULL-PWR RUN-UP; AND IF ALL CONDITIONS WERE NORMAL; WE WOULD CONTINUE WITH OUR FLT TO HGR. WE AGAIN MANNED THE ACFT; DID A STANDARD PREFLT RUN-UP WITH NORMAL INDICATIONS; ADVANCED THE THROTTLE TO FULL PWR WITH; AGAIN; ALL INDICATIONS NORMAL. WE TAXIED OUT TO THE RWY; DID ONE LAST RUN-UP; THEN ACCELERATED TO FULL PWR AND PERFORMED A NORMAL TKOF. THE CLB TO 5500 FT WAS NORMAL; WITH RATE OF CLB OFTEN EXCEEDING 1000 FPM. THE FLT TO HGR WAS UNEVENTFUL WITH ALL ENG INDICATIONS NORMAL AND THE ENG RUNNING SMOOTHLY.