Narrative:

Departed ZZZ at XA15 planning a 25 mi roundtrip to highway; circle and return to ZZZ. At around XA27; I experienced an 80% RPM loss about 1 mi north of highway at an altitude of +2500 ft MSL. At XA30 I made an emergency landing on highway approximately 9 mi west of abc. The aircraft did not sustain any damage nor was anyone endangered or hurt. The cause of RPM loss has not yet been determined. The wings were removed and the aircraft was trucked back to ZZZ.

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Original NASA ASRS Text

Title: A C172 PLT EXPERIENCED AN UNEXPLAINED 80% RPM LOSS. AN EMER HWY LNDG FOLLOWED WITH NO DAMAGE OR INJURIES.

Narrative: DEPARTED ZZZ AT XA15 PLANNING A 25 MI ROUNDTRIP TO HWY; CIRCLE AND RETURN TO ZZZ. AT AROUND XA27; I EXPERIENCED AN 80% RPM LOSS ABOUT 1 MI N OF HWY AT AN ALT OF +2500 FT MSL. AT XA30 I MADE AN EMER LNDG ON HWY APPROX 9 MI W OF ABC. THE ACFT DID NOT SUSTAIN ANY DAMAGE NOR WAS ANYONE ENDANGERED OR HURT. THE CAUSE OF RPM LOSS HAS NOT YET BEEN DETERMINED. THE WINGS WERE REMOVED AND THE ACFT WAS TRUCKED BACK TO ZZZ.

Data retrieved from NASA's ASRS site as of January 2009 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.