Narrative:

After practicing simulated engine out procedure to a field; student leveled off at 1300 ft MSL with satisfactory maneuver completion. I restored power to student and set carburetor heat back to off. Student smoothly advanced throttle to full power and initiated a climb at about 10 to 8 degrees nose up pitch. About 30 seconds into climb; the engine suddenly began a continuous vibration of moderate intensity. Aircraft controls were transferred to me the CFI and I began a slow circling climb to 1500 ft MSL at which point the climb arrested. The observed power output with throttle fully in was 1800-2000 rpm...not full power. I proceed to select nrst on GPS receiver and identified ZZZ as nearest field as I confirmed that we had partial engine power only. Maintained altitude. I navigated towards field while maintaining 1500 ft and about 70-80 KIAS. I began trouble shooting: mags check; fuel selector checks; throttle control check; fuel mixture check; and carburetor heat check. No remedy was made and so proceeded in direction to ZZZ which has 1800 ft runway with displaced threshold. I transmitted distress comms on the frequency commonly used by other aircraft in the practice area. With the airfield visually made and the visual approach set up; I set transponder and reported souls on board; fuel remaining. The pattern was visually clear and I made a short field landing with partial power on [the] runway. After landing and after landing checks completed I transmitted to alert airport. The FBO/pilot shop personnel notified me that tracon was on the phone. I coordinated with tracon to report that we were safe; then I contacted the flight school owner for further guidance. Aircraft was secured at the airport and my student and I [drove] home after debriefing the experience.

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Original NASA ASRS Text

Title: C172 Instructor Pilot reported landing at a nearby airport after experiencing engine power loss and vibration.

Narrative: After practicing simulated engine out procedure to a field; student leveled off at 1300 FT MSL with satisfactory maneuver completion. I restored power to student and set carburetor heat back to off. Student smoothly advanced throttle to full power and initiated a climb at about 10 to 8 degrees nose up pitch. About 30 seconds into climb; the engine suddenly began a continuous vibration of moderate intensity. Aircraft controls were transferred to me the CFI and I began a slow circling climb to 1500 ft MSL at which point the climb arrested. The observed power output with throttle fully in was 1800-2000 rpm...not full power. I proceed to select NRST on GPS receiver and identified ZZZ as nearest field as I confirmed that we had partial engine power only. Maintained altitude. I navigated towards field while maintaining 1500 FT and about 70-80 KIAS. I began trouble shooting: mags check; fuel selector checks; throttle control check; fuel mixture check; and carburetor heat check. No remedy was made and so proceeded in direction to ZZZ which has 1800 FT runway with displaced threshold. I transmitted distress comms on the frequency commonly used by other aircraft in the practice area. With the airfield visually made and the visual approach set up; I set transponder and reported souls on board; fuel remaining. The pattern was visually clear and I made a short field landing with partial power on [the] runway. After landing and after landing checks completed I transmitted to alert airport. The FBO/Pilot shop personnel notified me that Tracon was on the phone. I coordinated with Tracon to report that we were safe; then I contacted the Flight School owner for further guidance. Aircraft was secured at the airport and my student and I [drove] home after debriefing the experience.

Data retrieved from NASA's ASRS site 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.