Partial power loss in #1 engine.

Attributes
ACN	103776
Time
Date	198901
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : hnw
State Reference	CA
Altitude	msl bound lower : 9500 msl bound upper : 9500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 2 Eng, Retractable Gear
Flight Phase	cruise other cruise other
Flight Plan	VFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 2000 flight time type : 60
ASRS Report	103776
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Partial power loss experienced on left engine. Vibration noticed but not excessive. No loss of oil pressure or rise in oil temperature. Continued operation on affected engine to destination rhu approximately 30 mins en route. Aircraft was able to maintain altitude. I elected to not shut down and feather the affected engine because the partial power it produced seemed reliable to continue the flight. After disassembly of the cylinder affected discovery of a broken exhaust valve. The head of the exhaust valve was never found.

Original NASA ASRS Text

Title: PARTIAL POWER LOSS IN #1 ENGINE.

Narrative: PARTIAL PWR LOSS EXPERIENCED ON LEFT ENG. VIBRATION NOTICED BUT NOT EXCESSIVE. NO LOSS OF OIL PRESSURE OR RISE IN OIL TEMP. CONTINUED OPERATION ON AFFECTED ENG TO DEST RHU APPROX 30 MINS ENRTE. ACFT WAS ABLE TO MAINTAIN ALT. I ELECTED TO NOT SHUT DOWN AND FEATHER THE AFFECTED ENG BECAUSE THE PARTIAL PWR IT PRODUCED SEEMED RELIABLE TO CONTINUE THE FLT. AFTER DISASSEMBLY OF THE CYLINDER AFFECTED DISCOVERY OF A BROKEN EXHAUST VALVE. THE HEAD OF THE EXHAUST VALVE WAS NEVER FOUND.

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.