Aircraft equipment problem. Cylinder exhaust valve.

Attributes
ACN	305800
Time
Date	199505
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : azq
State Reference	KY
Altitude	msl bound lower : 11500 msl bound upper : 11500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Flight Plan	None
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private
Experience	flight time total : 1482
ASRS Report	305800
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

I was level at 11500 ft when engine suddenly sounded rough and vibrated. I heard a few backfire type sounds. I adjusted RPM to lessen vibration and mixture to stop backfire. The engine was putting out good power. I established that #3 cylinder was dead but had no idea why. I determined where I was and notified the FAA controller on 121.5. I was steered to combs but elected big sandy. I landed without incident. A mechanic looked in the cylinder and said he could see part of #3 exhaust valve missing. Both spark plugs were damaged beyond operation.

Original NASA ASRS Text

Title: ACFT EQUIP PROB. CYLINDER EXHAUST VALVE.

Narrative: I WAS LEVEL AT 11500 FT WHEN ENG SUDDENLY SOUNDED ROUGH AND VIBRATED. I HEARD A FEW BACKFIRE TYPE SOUNDS. I ADJUSTED RPM TO LESSEN VIBRATION AND MIXTURE TO STOP BACKFIRE. THE ENG WAS PUTTING OUT GOOD PWR. I ESTABLISHED THAT #3 CYLINDER WAS DEAD BUT HAD NO IDEA WHY. I DETERMINED WHERE I WAS AND NOTIFIED THE FAA CTLR ON 121.5. I WAS STEERED TO COMBS BUT ELECTED BIG SANDY. I LANDED WITHOUT INCIDENT. A MECH LOOKED IN THE CYLINDER AND SAID HE COULD SEE PART OF #3 EXHAUST VALVE MISSING. BOTH SPARK PLUGS WERE DAMAGED BEYOND OP.

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.