Narrative:

I was flying with the owner of the aircraft during an instrument proficiency check. A precautionary landing was made because of engine roughness due to carburetor ice and probably some spark plug fouling from 2 hours of non leaned operation. The owners (2) of this aircraft request instrument proficiency instruction approximately every 6 months. It had not been unusual for this aircraft engine to develop carburetor ice in the past. It is equipped with a carburetor temperature gauge. On this day, we were operating on eastern long island in good VFR with isolated snow showers aloft to the south of long island and to the west of isp. After some instrument air work, holds and approachs, we decided to do 2 ILS runway 24 approachs at isp and then proceed to frg. On the first missed approach, the engine became rough. Evidently the lower power setting on the approach added to the carburetor ice. Facing a rough engine and either flying approximately 20 mi for another approach or 20 mi to frg while navigating around snow aloft, I elected to make a precautionary landing at isp. The corrective action for this day was a cup of coffee, ground instruction and a delay to let the carburetor ice melt and wait for the snow showers to pass. On future flts in this aircraft, when engine roughness occurs, a break in training to apply carburetor heat and lean the mixture to avoid fouling will be the procedure. Supplemental information from acn 571578: we intended to do 2 approachs at isp. After the first, we were on the missed approach when the engine started sounding rough. We determined there was carburetor ice and, appropriately, applied carburetor heat. Since there were snow showers in the area, we decided to land at isp and made such request. The engine began to run smoothly again shortly after applying the carburetor heat. There was no problem with the engine after that.

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Original NASA ASRS Text

Title: A PA24-250 TRAINING FLT IS CUT SHORT AFTER THE FIRST APCH AND MISSED APCH AFTER THE ENG STARTS RUNNING ROUGH DUE TO CARB ICING. CREW STAYS ON GND FOR A BREAK IN THE WX AT ISP, NY.

Narrative: I WAS FLYING WITH THE OWNER OF THE ACFT DURING AN INST PROFICIENCY CHK. A PRECAUTIONARY LNDG WAS MADE BECAUSE OF ENG ROUGHNESS DUE TO CARB ICE AND PROBABLY SOME SPARK PLUG FOULING FROM 2 HRS OF NON LEANED OP. THE OWNERS (2) OF THIS ACFT REQUEST INST PROFICIENCY INSTRUCTION APPROX EVERY 6 MONTHS. IT HAD NOT BEEN UNUSUAL FOR THIS ACFT ENG TO DEVELOP CARB ICE IN THE PAST. IT IS EQUIPPED WITH A CARB TEMP GAUGE. ON THIS DAY, WE WERE OPERATING ON EASTERN LONG ISLAND IN GOOD VFR WITH ISOLATED SNOW SHOWERS ALOFT TO THE S OF LONG ISLAND AND TO THE W OF ISP. AFTER SOME INST AIR WORK, HOLDS AND APCHS, WE DECIDED TO DO 2 ILS RWY 24 APCHS AT ISP AND THEN PROCEED TO FRG. ON THE FIRST MISSED APCH, THE ENG BECAME ROUGH. EVIDENTLY THE LOWER PWR SETTING ON THE APCH ADDED TO THE CARB ICE. FACING A ROUGH ENG AND EITHER FLYING APPROX 20 MI FOR ANOTHER APCH OR 20 MI TO FRG WHILE NAVING AROUND SNOW ALOFT, I ELECTED TO MAKE A PRECAUTIONARY LNDG AT ISP. THE CORRECTIVE ACTION FOR THIS DAY WAS A CUP OF COFFEE, GND INSTRUCTION AND A DELAY TO LET THE CARB ICE MELT AND WAIT FOR THE SNOW SHOWERS TO PASS. ON FUTURE FLTS IN THIS ACFT, WHEN ENG ROUGHNESS OCCURS, A BREAK IN TRAINING TO APPLY CARB HEAT AND LEAN THE MIXTURE TO AVOID FOULING WILL BE THE PROC. SUPPLEMENTAL INFO FROM ACN 571578: WE INTENDED TO DO 2 APCHS AT ISP. AFTER THE FIRST, WE WERE ON THE MISSED APCH WHEN THE ENG STARTED SOUNDING ROUGH. WE DETERMINED THERE WAS CARB ICE AND, APPROPRIATELY, APPLIED CARB HEAT. SINCE THERE WERE SNOW SHOWERS IN THE AREA, WE DECIDED TO LAND AT ISP AND MADE SUCH REQUEST. THE ENG BEGAN TO RUN SMOOTHLY AGAIN SHORTLY AFTER APPLYING THE CARB HEAT. THERE WAS NO PROB WITH THE ENG AFTER THAT.

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.