Narrative:

I was flying cross country from sat to rkp at 5500 ft. Approximately 35 mi southeast of san antonio, engine lost 1400 RPM and then surged back to cruise power setting of 2400 RPM. The drop and surge continued for the next 10 mins. I contacted ZHU and advised them of my intentions to make a precautionary landing at connally ranch, a private airstrip 25 mi south of san antonio. ZHU asked me if I wanted to declare an emergency, I said yes. I landed safety at connally without incident. On inspection by an a&P engine tested normal. The anomaly could not be duplicated.

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Original NASA ASRS Text

Title: A COMMERCIAL FIXED WING SMALL ACFT IN CRUISE AT 5500 FT DECLARED AN EMER AND DIVERTED DUE TO LOSS OF ENG PWR CAUSE UNKNOWN.

Narrative: I WAS FLYING XCOUNTRY FROM SAT TO RKP AT 5500 FT. APPROX 35 MI SE OF SAN ANTONIO, ENG LOST 1400 RPM AND THEN SURGED BACK TO CRUISE PWR SETTING OF 2400 RPM. THE DROP AND SURGE CONTINUED FOR THE NEXT 10 MINS. I CONTACTED ZHU AND ADVISED THEM OF MY INTENTIONS TO MAKE A PRECAUTIONARY LNDG AT CONNALLY RANCH, A PVT AIRSTRIP 25 MI S OF SAN ANTONIO. ZHU ASKED ME IF I WANTED TO DECLARE AN EMER, I SAID YES. I LANDED SAFETY AT CONNALLY WITHOUT INCIDENT. ON INSPECTION BY AN A&P ENG TESTED NORMAL. THE ANOMALY COULD NOT BE DUPLICATED.

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.