Narrative:

While cruising at 6500 ft MSL in my C150H, the engine began running rough. I applied full carburetor heat and full throttle trying to maintain level flight. After a couple mins and no improvement, I thought I should lean the mixture further to compensate for the carburetor heat. (I had already leaned for cruise.) when even the slightest additional leaning caused the engine to cut out, I went to full rich. The engine was still running (though very rough), but not developing enough power to maintain altitude. Having tried everything else, I pushed the carburetor heat in (to full cold). At this point, the engine quit altogether. I returned the carburetor heat to full hot, pushed the nose down and the engine started running again, still at less than normal power and very rough. I was on a VFR flight plan and had asked augusta approach for radar TA's. They had given me a transponder code and radar vectors. I was within their TRSA, but well away from their class D area. Since I was on their frequency when the engine problem occurred, I declared an emergency. The controller offered me a choice of bush field (controled) and daniel field (uncontrolled). I had never landed at either and there were a couple of exchanges on the radio (during which I confused the 2 names) before I realized that I should land at daniel which was the airport that I had in sight at the time. Once I was committed to daniel field, the controller said the usual, 'radar service terminated, frequency change approved, squawk VFR.' on the way down, when I had the airport made, I pulled the throttle back to idle, it seemed smoother, but then it was at idle. I made a normal landing. After landing, I cut off the carburetor heat (out of habit) and added power to taxi. No problem. Once stopped, I did a run-up which was totally normal. It occurred to me that the intake air filter might have iced over, but the air was clear and well above freezing, even at 6500 ft. There was a fairly impressive shop at daniel field. (I had never landed at that airport before.) apparently, ATC had told them to expect me. They were able to put a mechanic on it right away. He did a ground run-up and found no problem. He then checked it over visually pretty thoroughly. He checked the filter and removed it to inspect the air box. All was ok. Finally, he decided that one of the intake pipes was not lined up properly and that it had probably been leaking. He removed the pipe and replaced it, properly aligned. After the repair, everything checked out ok (as it had before the repair). Having signed off the repair, he sent me on my way. Incidentally, about 5 mins after I landed, while I was describing the problem to the mechanic, the local city fire department showed up. Apparently, ATC had also called them. I do not know what caused the problem or what could have been done to prevent it. The controller was professional and handled the situation well.

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Original NASA ASRS Text

Title: ACFT EQUIP PROB MANDATES THAT A PVT PLT IN HIS C150H DIVERT TO ANOTHER ARPT AFTER DECLARING AN EMER WITH APCH CTLR AT AUG, GA.

Narrative: WHILE CRUISING AT 6500 FT MSL IN MY C150H, THE ENG BEGAN RUNNING ROUGH. I APPLIED FULL CARB HEAT AND FULL THROTTLE TRYING TO MAINTAIN LEVEL FLT. AFTER A COUPLE MINS AND NO IMPROVEMENT, I THOUGHT I SHOULD LEAN THE MIXTURE FURTHER TO COMPENSATE FOR THE CARB HEAT. (I HAD ALREADY LEANED FOR CRUISE.) WHEN EVEN THE SLIGHTEST ADDITIONAL LEANING CAUSED THE ENG TO CUT OUT, I WENT TO FULL RICH. THE ENG WAS STILL RUNNING (THOUGH VERY ROUGH), BUT NOT DEVELOPING ENOUGH PWR TO MAINTAIN ALT. HAVING TRIED EVERYTHING ELSE, I PUSHED THE CARB HEAT IN (TO FULL COLD). AT THIS POINT, THE ENG QUIT ALTOGETHER. I RETURNED THE CARB HEAT TO FULL HOT, PUSHED THE NOSE DOWN AND THE ENG STARTED RUNNING AGAIN, STILL AT LESS THAN NORMAL PWR AND VERY ROUGH. I WAS ON A VFR FLT PLAN AND HAD ASKED AUGUSTA APCH FOR RADAR TA'S. THEY HAD GIVEN ME A XPONDER CODE AND RADAR VECTORS. I WAS WITHIN THEIR TRSA, BUT WELL AWAY FROM THEIR CLASS D AREA. SINCE I WAS ON THEIR FREQ WHEN THE ENG PROB OCCURRED, I DECLARED AN EMER. THE CTLR OFFERED ME A CHOICE OF BUSH FIELD (CTLED) AND DANIEL FIELD (UNCTLED). I HAD NEVER LANDED AT EITHER AND THERE WERE A COUPLE OF EXCHANGES ON THE RADIO (DURING WHICH I CONFUSED THE 2 NAMES) BEFORE I REALIZED THAT I SHOULD LAND AT DANIEL WHICH WAS THE ARPT THAT I HAD IN SIGHT AT THE TIME. ONCE I WAS COMMITTED TO DANIEL FIELD, THE CTLR SAID THE USUAL, 'RADAR SVC TERMINATED, FREQ CHANGE APPROVED, SQUAWK VFR.' ON THE WAY DOWN, WHEN I HAD THE ARPT MADE, I PULLED THE THROTTLE BACK TO IDLE, IT SEEMED SMOOTHER, BUT THEN IT WAS AT IDLE. I MADE A NORMAL LNDG. AFTER LNDG, I CUT OFF THE CARB HEAT (OUT OF HABIT) AND ADDED PWR TO TAXI. NO PROB. ONCE STOPPED, I DID A RUN-UP WHICH WAS TOTALLY NORMAL. IT OCCURRED TO ME THAT THE INTAKE AIR FILTER MIGHT HAVE ICED OVER, BUT THE AIR WAS CLR AND WELL ABOVE FREEZING, EVEN AT 6500 FT. THERE WAS A FAIRLY IMPRESSIVE SHOP AT DANIEL FIELD. (I HAD NEVER LANDED AT THAT ARPT BEFORE.) APPARENTLY, ATC HAD TOLD THEM TO EXPECT ME. THEY WERE ABLE TO PUT A MECH ON IT RIGHT AWAY. HE DID A GND RUN-UP AND FOUND NO PROB. HE THEN CHKED IT OVER VISUALLY PRETTY THOROUGHLY. HE CHKED THE FILTER AND REMOVED IT TO INSPECT THE AIR BOX. ALL WAS OK. FINALLY, HE DECIDED THAT ONE OF THE INTAKE PIPES WAS NOT LINED UP PROPERLY AND THAT IT HAD PROBABLY BEEN LEAKING. HE REMOVED THE PIPE AND REPLACED IT, PROPERLY ALIGNED. AFTER THE REPAIR, EVERYTHING CHKED OUT OK (AS IT HAD BEFORE THE REPAIR). HAVING SIGNED OFF THE REPAIR, HE SENT ME ON MY WAY. INCIDENTALLY, ABOUT 5 MINS AFTER I LANDED, WHILE I WAS DESCRIBING THE PROB TO THE MECH, THE LCL CITY FIRE DEPT SHOWED UP. APPARENTLY, ATC HAD ALSO CALLED THEM. I DO NOT KNOW WHAT CAUSED THE PROB OR WHAT COULD HAVE BEEN DONE TO PREVENT IT. THE CTLR WAS PROFESSIONAL AND HANDLED THE SIT WELL.

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.