GA small aircraft diverted to alternate due rough engine at course.

Attributes
ACN	107563
Time
Date	198903
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : avl
State Reference	NC
Altitude	msl bound lower : 8000 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : avl
Operator	general aviation : personal
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : cfi pilot : instrument pilot : commercial
Experience	flight time last 90 days : 60 flight time total : 1500 flight time type : 1000
ASRS Report	107563
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	aircraft : equipment problem dissipated flight crew : declared emergency flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

Engine felt rough prior to crossing mountains from sug to sot to knoxville. I had previously departed gsp in an small aircraft. I have 200 hours on my engine since overhaul and have had one cylinder removed and repaired because of a stuck valve. The engine was overhauled by FBO at cape gorado below st louis. I suspect carburetor ice, but I was not sure it was not a sticking valve. The engine felt rough, I applied full carburetor heat and leaned with mixture. After a minute or so had passed, I pushed the carburetor heat back to 'opp' and the engine appeared to almost quit. I reapplied carburetor heat and the engine came to life again. I requested vectors to a field where I could have the engine checked out, and was vectored to asheville, nc, where I landed. For the first 3000' of descent, the engine ran very rough, then smoothed out prior to landing. A local flight instrument who I presume was more familiar with mountain flying, ran my engine up and suggested that the engine was running smoothly and that maybe I had encountered carburetor ice. I refueled and flew on back to lexington, ky, via knoxville west/O incident.

Original NASA ASRS Text

Title: GA SMA DIVERTED TO ALTERNATE DUE ROUGH ENGINE AT COURSE.

Narrative: ENG FELT ROUGH PRIOR TO XING MOUNTAINS FROM SUG TO SOT TO KNOXVILLE. I HAD PREVIOUSLY DEPARTED GSP IN AN SMA. I HAVE 200 HRS ON MY ENG SINCE OVERHAUL AND HAVE HAD ONE CYLINDER REMOVED AND REPAIRED BECAUSE OF A STUCK VALVE. THE ENG WAS OVERHAULED BY FBO AT CAPE GORADO BELOW ST LOUIS. I SUSPECT CARB ICE, BUT I WAS NOT SURE IT WAS NOT A STICKING VALVE. THE ENG FELT ROUGH, I APPLIED FULL CARB HEAT AND LEANED WITH MIXTURE. AFTER A MINUTE OR SO HAD PASSED, I PUSHED THE CARB HEAT BACK TO 'OPP' AND THE ENG APPEARED TO ALMOST QUIT. I REAPPLIED CARB HEAT AND THE ENG CAME TO LIFE AGAIN. I REQUESTED VECTORS TO A FIELD WHERE I COULD HAVE THE ENG CHKED OUT, AND WAS VECTORED TO ASHEVILLE, NC, WHERE I LANDED. FOR THE FIRST 3000' OF DSCNT, THE ENG RAN VERY ROUGH, THEN SMOOTHED OUT PRIOR TO LNDG. A LCL FLT INSTR WHO I PRESUME WAS MORE FAMILIAR WITH MOUNTAIN FLYING, RAN MY ENG UP AND SUGGESTED THAT THE ENG WAS RUNNING SMOOTHLY AND THAT MAYBE I HAD ENCOUNTERED CARB ICE. I REFUELED AND FLEW ON BACK TO LEXINGTON, KY, VIA KNOXVILLE W/O INCIDENT.

Data retrieved from NASA's ASRS site as of August 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.