Narrative:

I was maneuvering in the practice area and had just taken the control from the student when the engine began to run very rough. Realizing it was an engine problem I immediately turned towards the airport and pitched for the best glide airspeed the engine tachometer with full power was only making 2100 RPM or just inside the green arc. Realizing that I was unable to hold my altitude of 2;600 ft MSL; I held my best glide airspeed and continued towards the airport. I contacted approach control and advised them that I was having engine problems; was unable to maintain altitude; and that I was declaring an emergency. We continued towards the airport while continuing to lose altitude. Once reaching an altitude of 1;500 ft MSL we were able to hold altitude with full power. We continued to the airport at 1;500 ft MSL and had a quite uneventful landing.when I was unable to hold altitude with full power I knew one of two things was going to happen. Either I was going to be descending down to an altitude that I could maintain level flight or I was going to be forced to do an off airport landing. Knowing that a cessna 150 can have some performance issues when it is producing full power; especially with the density altitude that can occur in the middle of the day in [a warm climate] not helping the issues. I wanted to be talking to some controlling agency that would have an idea of where we were if we had to execute an off airport landing and at least make them aware of my situation. Everyone that helped with the emergency was very accommodating and they were very helpful. I just felt at the time not knowing what was going on with the engine and not being able to hold altitude declaring an emergency was the best course of action.

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Original NASA ASRS Text

Title: A C150 lost engine power in the practice area. The Instructor assumed control; declared an emergency; and was able to safely return to the airport.

Narrative: I was maneuvering in the practice area and had just taken the control from the student when the engine began to run very rough. Realizing it was an engine problem I immediately turned towards the airport and pitched for the best glide airspeed the engine tachometer with full power was only making 2100 RPM or just inside the green arc. Realizing that I was unable to hold my altitude of 2;600 FT MSL; I held my best glide airspeed and continued towards the airport. I contacted Approach Control and advised them that I was having engine problems; was unable to maintain altitude; and that I was declaring an emergency. We continued towards the airport while continuing to lose altitude. Once reaching an altitude of 1;500 FT MSL we were able to hold altitude with full power. We continued to the airport at 1;500 FT MSL and had a quite uneventful landing.When I was unable to hold altitude with full power I knew one of two things was going to happen. Either I was going to be descending down to an altitude that I could maintain level flight or I was going to be forced to do an off airport landing. Knowing that a Cessna 150 can have some performance issues when it is producing full power; especially with the density altitude that can occur in the middle of the day in [a warm climate] not helping the issues. I wanted to be talking to some controlling agency that would have an idea of where we were if we had to execute an off airport landing and at least make them aware of my situation. Everyone that helped with the emergency was very accommodating and they were very helpful. I just felt at the time not knowing what was going on with the engine and not being able to hold altitude declaring an emergency was the best course of action.

Data retrieved from NASA's ASRS site as of July 2013 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.