Narrative:

I was providing primary flight instruction in a cessna 150. We were inbound to the airport from the south; and were directed by tower to enter left traffic for runway 19.at approximately 1400 feet MSL on the descent to traffic pattern altitude (1300 feet); I encountered a loss in RPM of approximately 500-600 RPM. At the time of the power loss; I had full power (2400 RPM) selected. Due to my low proximity to the ground; and the fact that runway 01 was almost directly in front of me; I elected to request a landing straight in to runway 01. I believed it to be carburetor icing; and I applied full carburetor heat. I knew that the carburetor on the O-200 engine on the cessna 150 is very susceptible to carb icing; and the relative humidity on this day was also unusually high (approx 80%). The conditions to form carburetor icing were set.following my landing on runway 01; I ran the engine up to full power; and the engine ran smooth; both with carb heat on and off. This confirmed by suspicion of carb ice. We taxied to the transient parking to shut down; and call the flight school to report it. We decided to go to the run up area and do another run up to check engine function. Engine ran fine; both with carb heat on and off. It was determined that the carb ice had been eliminated and the engine was running normally. I've encountered carburetor icing before. However; this is the first time I've encountered it at pattern altitude.having noticed that the humidity level was higher than normal; I should have been more proactive with use of the carburetor heat on descent; even while operating the engine within the parameters where the poh says it is normally not required.

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Original NASA ASRS Text

Title: C150 Instructor Pilot reported encountering carburetor ice that resulted in a power loss in the pattern at EMT.

Narrative: I was providing primary flight instruction in a Cessna 150. We were inbound to the airport from the south; and were directed by Tower to enter left traffic for runway 19.At approximately 1400 feet MSL on the descent to traffic pattern altitude (1300 feet); I encountered a loss in RPM of approximately 500-600 RPM. At the time of the power loss; I had full power (2400 RPM) selected. Due to my low proximity to the ground; and the fact that runway 01 was almost directly in front of me; I elected to request a landing straight in to runway 01. I believed it to be carburetor icing; and I applied full carburetor heat. I knew that the carburetor on the O-200 engine on the Cessna 150 is very susceptible to carb icing; and the relative humidity on this day was also unusually high (approx 80%). The conditions to form carburetor icing were set.Following my landing on runway 01; I ran the engine up to full power; and the engine ran smooth; both with carb heat on and off. This confirmed by suspicion of carb ice. We taxied to the transient parking to shut down; and call the flight school to report it. We decided to go to the run up area and do another run up to check engine function. Engine ran fine; both with carb heat on and off. It was determined that the carb ice had been eliminated and the engine was running normally. I've encountered carburetor icing before. However; this is the first time I've encountered it at pattern altitude.Having noticed that the humidity level was higher than normal; I should have been more proactive with use of the carburetor heat on descent; even while operating the engine within the parameters where the POH says it is normally not required.

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.