Narrative:

After modeling a slip for my student with the airplane in its proper configuration; we experienced engine roughness at 3;000 feet MSL. We were on a 4 mile 45 entry for the downwind for runway 18. I established best glide; called our position; situation and intentions to the two aircraft in the area (which was to proceed inbound for a short approach landing due to engine roughness) then began to troubleshoot. I confirmed that the carb heat was full on; mixture full rich; fuel tanks on both with both being nearly full and fuel gauges checked normal. When we departed; both tanks were full at 26 gallons total and our flight according to the hobbs was 1.1. The mags also checked okay. Despite full throttle; we were in a steady descent with minimal engine power and unable to climb. Approximately 1 mile east of our downwind entry; it was evident we would not make the runway; and with housing between us; I opted to remain to the east; and aim for a field east of the housing. I continued my descent and prepared for a forced landing; while continuing to attempt to regain power. The two aircraft that were in the pattern had visual on our position. At approximately 100 feet AGL; I attempted the throttle one last time. The engine regained full power; was smooth; and I was able to establish a climb. I continued my climb and was able to establish an altitude to safely proceed over the housing which would allow me the option; should it occur again; to glide to either side of the development; at about 800 feet AGL. I was able to enter a short base and land without incident. The engine remained normal.

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Original NASA ASRS Text

Title: C150 instructor reported engine roughness and loss of power after demonstrating a slip at 3;000 feet with a recovery at about 100 feet AGL with a climb to pattern altitude and a successful landing. Instructor reported probable carb icing.

Narrative: After modeling a slip for my student with the airplane in its proper configuration; we experienced engine roughness at 3;000 feet MSL. We were on a 4 mile 45 entry for the downwind for runway 18. I established best glide; called our position; situation and intentions to the two aircraft in the area (which was to proceed inbound for a short approach landing due to engine roughness) then began to troubleshoot. I confirmed that the carb heat was full on; mixture full rich; fuel tanks on both with both being nearly full and fuel gauges checked normal. When we departed; both tanks were full at 26 gallons total and our flight according to the hobbs was 1.1. The mags also checked okay. Despite full throttle; we were in a steady descent with minimal engine power and unable to climb. Approximately 1 mile east of our downwind entry; it was evident we would not make the runway; and with housing between us; I opted to remain to the east; and aim for a field east of the housing. I continued my descent and prepared for a forced landing; while continuing to attempt to regain power. The two aircraft that were in the pattern had visual on our position. At approximately 100 feet AGL; I attempted the throttle one last time. The engine regained full power; was smooth; and I was able to establish a climb. I continued my climb and was able to establish an altitude to safely proceed over the housing which would allow me the option; should it occur again; to glide to either side of the development; at about 800 feet AGL. I was able to enter a short base and land without incident. The engine remained normal.

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.