Precautionary landing on highway when engine runs rough.

Attributes
ACN	211377
Time
Date	199205
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : mtw
State Reference	WI
Altitude	msl bound lower : 2500 msl bound upper : 2500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : instructional
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other
Flight Plan	None
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial pilot : cfi
Experience	flight time last 90 days : 100 flight time total : 500 flight time type : 80
ASRS Report	211377
Person 2
Affiliation	Other
Function	observation : observer
Qualification	other other : other
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other other : unspecified cockpit
Resolutory Action	flight crew : declared emergency other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

The problem arose while en route to a spray area. Which I and a state of wi, observer were engaged as an aerial chase plane. Just southwest of kewaunee I noticed the engine began to run very rough. After checking the emergency procedures for roughness of an engine I tried pwring the engine back to a lower RPM. The engine ran smoothly at 1700 RPM. Not wanting to ruin the engine totally or chancing a total failure in a worse position I decided to land the aircraft. One of the spray pilots suggested a landing on any of the ew running roads. This is what I opted for taking precaution of traffic on the highway of choice. After landing on highway 29, 3 mi southwest of kewaunee I taxied into a farmers driveway and shut down. During the entire time I had oil pressure on the engine and after landing still had 5 quarts in the sump and found a bent pushrod for the valve that froze causing the roughness. I feel that I took the proper action and made a good decision, that being landing while still having partial power instead of the possibility of the engine seizing and not having any choice on landing.

Original NASA ASRS Text

Title: PRECAUTIONARY LNDG ON HIGHWAY WHEN ENG RUNS ROUGH.

Narrative: THE PROBLEM AROSE WHILE ENRTE TO A SPRAY AREA. WHICH I AND A STATE OF WI, OBSERVER WERE ENGAGED AS AN AERIAL CHASE PLANE. JUST SW OF KEWAUNEE I NOTICED THE ENG BEGAN TO RUN VERY ROUGH. AFTER CHKING THE EMER PROCS FOR ROUGHNESS OF AN ENG I TRIED PWRING THE ENG BACK TO A LOWER RPM. THE ENG RAN SMOOTHLY AT 1700 RPM. NOT WANTING TO RUIN THE ENG TOTALLY OR CHANCING A TOTAL FAILURE IN A WORSE POS I DECIDED TO LAND THE ACFT. ONE OF THE SPRAY PLTS SUGGESTED A LNDG ON ANY OF THE EW RUNNING ROADS. THIS IS WHAT I OPTED FOR TAKING PRECAUTION OF TFC ON THE HIGHWAY OF CHOICE. AFTER LNDG ON HIGHWAY 29, 3 MI SW OF KEWAUNEE I TAXIED INTO A FARMERS DRIVEWAY AND SHUT DOWN. DURING THE ENTIRE TIME I HAD OIL PRESSURE ON THE ENG AND AFTER LNDG STILL HAD 5 QUARTS IN THE SUMP AND FOUND A BENT PUSHROD FOR THE VALVE THAT FROZE CAUSING THE ROUGHNESS. I FEEL THAT I TOOK THE PROPER ACTION AND MADE A GOOD DECISION, THAT BEING LNDG WHILE STILL HAVING PARTIAL PWR INSTEAD OF THE POSSIBILITY OF THE ENG SEIZING AND NOT HAVING ANY CHOICE ON LNDG.

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.