Narrative:

While en route from annapolis, md, to camden, sc, I began noticing a slight decrease in RPM's. It was intermittent. Because I had found some dirt in the carburetor several months before, I told flight following I would return to petersburg for a precautionary landing. A mechanic listened to the engine and drained fuel but found nothing wrong. I asked what he would do and he said he would test fly and if nothing occurred, keep going. I did this and the flight continued uneventfully for another hour and 50 mins. Nearing rockingham, nc, the same thing happened again. This time I landed again and left the aircraft pending removal of the carburetor for inspection, since more drained fuel revealed no water or other contamination. On occasion I have not fully tightened the throttle lock and noticed a slow decrease in RPM's because vibration was slowly closing the throttle. This produced momentary anxiety until I realized what I had neglected to do. Later I wondered if this is what had happened over petersburg, but in the second half of the flight, I rechked the throttle lock several times. At no time did I feel there was an emergency since I had sufficient fuel, plenty of altitude and an airport close at hand. I made it clear in my xmissions to flight following that I was making a precautionary landing and that no emergency existed. However, I should have listened to my own judgement, and not the mechanic who, after all, was not the responsible authority/authorized in deciding to continue the flight. Even after many yrs and many sound judgements, 'get homeitis' can still influence experienced pilots and in this case I would have been better off by remaining at ptb and getting the carburetor torn apart instead of continuing on with an unknown problem.

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Original NASA ASRS Text

Title: PVT PLT OF A C170A MADE A PRECAUTIONARY LNDG AFTER NOTICING A DECREASE IN ENG RPM. CARB PROB IS SUSPECTED.

Narrative: WHILE ENRTE FROM ANNAPOLIS, MD, TO CAMDEN, SC, I BEGAN NOTICING A SLIGHT DECREASE IN RPM'S. IT WAS INTERMITTENT. BECAUSE I HAD FOUND SOME DIRT IN THE CARB SEVERAL MONTHS BEFORE, I TOLD FLT FOLLOWING I WOULD RETURN TO PETERSBURG FOR A PRECAUTIONARY LNDG. A MECH LISTENED TO THE ENG AND DRAINED FUEL BUT FOUND NOTHING WRONG. I ASKED WHAT HE WOULD DO AND HE SAID HE WOULD TEST FLY AND IF NOTHING OCCURRED, KEEP GOING. I DID THIS AND THE FLT CONTINUED UNEVENTFULLY FOR ANOTHER HR AND 50 MINS. NEARING ROCKINGHAM, NC, THE SAME THING HAPPENED AGAIN. THIS TIME I LANDED AGAIN AND LEFT THE ACFT PENDING REMOVAL OF THE CARB FOR INSPECTION, SINCE MORE DRAINED FUEL REVEALED NO WATER OR OTHER CONTAMINATION. ON OCCASION I HAVE NOT FULLY TIGHTENED THE THROTTLE LOCK AND NOTICED A SLOW DECREASE IN RPM'S BECAUSE VIBRATION WAS SLOWLY CLOSING THE THROTTLE. THIS PRODUCED MOMENTARY ANXIETY UNTIL I REALIZED WHAT I HAD NEGLECTED TO DO. LATER I WONDERED IF THIS IS WHAT HAD HAPPENED OVER PETERSBURG, BUT IN THE SECOND HALF OF THE FLT, I RECHKED THE THROTTLE LOCK SEVERAL TIMES. AT NO TIME DID I FEEL THERE WAS AN EMER SINCE I HAD SUFFICIENT FUEL, PLENTY OF ALT AND AN ARPT CLOSE AT HAND. I MADE IT CLR IN MY XMISSIONS TO FLT FOLLOWING THAT I WAS MAKING A PRECAUTIONARY LNDG AND THAT NO EMER EXISTED. HOWEVER, I SHOULD HAVE LISTENED TO MY OWN JUDGEMENT, AND NOT THE MECH WHO, AFTER ALL, WAS NOT THE RESPONSIBLE AUTH IN DECIDING TO CONTINUE THE FLT. EVEN AFTER MANY YRS AND MANY SOUND JUDGEMENTS, 'GET HOMEITIS' CAN STILL INFLUENCE EXPERIENCED PLTS AND IN THIS CASE I WOULD HAVE BEEN BETTER OFF BY REMAINING AT PTB AND GETTING THE CARB TORN APART INSTEAD OF CONTINUING ON WITH AN UNKNOWN PROB.

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.