An M20C experienced a power loss with a rough running engine. The pilot landed at a nearby airport.

Attributes
ACN	636552
Time
Date	200411
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : wld.airport
State Reference	KS
Altitude	msl single value : 3500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ict.tracon
Operator	general aviation : personal
Make Model Name	M-20 B/C Ranger
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	None
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : multi engine pilot : cfi pilot : atp
Experience	flight time last 90 days : 40 flight time total : 3400 flight time type : 5
ASRS Report	636552
Person 2
Affiliation	government : faa
Function	controller : approach
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : landed in emergency condition
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

En route VFR in IMC, receiving VFR flight following from approach, the aircraft's engine began running rough. Switching fuel tanks, applying carburetor heat, turning on the auxiliary fuel pump, adjusting mixture and individually selecting magneto position did not dampen the roughness and I began to consider a divert. Suddenly power dropped dramatically and I turned toward wld, verified I had a tank with fuel selected, and informed ATC of the power loss and my intention. ATC did not ask nor did I remember to specifically declare an emergency, but the controller performed quite professionally and did ask for the number of 'souls' on board (one). Power seemed to return somewhat, albeit very roughly, with reapplication of carburetor heat (despite the dry air) and I was tempted to continue to destination, but thought the better of it and continued toward wld. I asked ATC for the frequency for the field and was given the AWOS frequency. Suggestion: controllers should have immediate access to all local unicom frequencys. I landed under partial power at wld and phoned approach. I want to commend the professionalism and response of the controller on duty. He had alerted local authorities and began a response should I have not made it to the airport.

Original NASA ASRS Text

Title: AN M20C EXPERIENCED A PWR LOSS WITH A ROUGH RUNNING ENG. THE PLT LANDED AT A NEARBY ARPT.

Narrative: ENRTE VFR IN IMC, RECEIVING VFR FLT FOLLOWING FROM APCH, THE ACFT'S ENG BEGAN RUNNING ROUGH. SWITCHING FUEL TANKS, APPLYING CARB HEAT, TURNING ON THE AUX FUEL PUMP, ADJUSTING MIXTURE AND INDIVIDUALLY SELECTING MAGNETO POS DID NOT DAMPEN THE ROUGHNESS AND I BEGAN TO CONSIDER A DIVERT. SUDDENLY PWR DROPPED DRAMATICALLY AND I TURNED TOWARD WLD, VERIFIED I HAD A TANK WITH FUEL SELECTED, AND INFORMED ATC OF THE PWR LOSS AND MY INTENTION. ATC DID NOT ASK NOR DID I REMEMBER TO SPECIFICALLY DECLARE AN EMER, BUT THE CTLR PERFORMED QUITE PROFESSIONALLY AND DID ASK FOR THE NUMBER OF 'SOULS' ON BOARD (ONE). PWR SEEMED TO RETURN SOMEWHAT, ALBEIT VERY ROUGHLY, WITH REAPPLICATION OF CARB HEAT (DESPITE THE DRY AIR) AND I WAS TEMPTED TO CONTINUE TO DEST, BUT THOUGHT THE BETTER OF IT AND CONTINUED TOWARD WLD. I ASKED ATC FOR THE FREQ FOR THE FIELD AND WAS GIVEN THE AWOS FREQ. SUGGESTION: CTLRS SHOULD HAVE IMMEDIATE ACCESS TO ALL LCL UNICOM FREQS. I LANDED UNDER PARTIAL PWR AT WLD AND PHONED APCH. I WANT TO COMMEND THE PROFESSIONALISM AND RESPONSE OF THE CTLR ON DUTY. HE HAD ALERTED LCL AUTHORITIES AND BEGAN A RESPONSE SHOULD I HAVE NOT MADE IT TO THE ARPT.

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.