Narrative:

Passenger and I first noticed a very faint burning smell on short final. Smell was very faint. During taxi back to runway; smell became slightly more pronounced but still faint. I did not believe that it was coming from the aircraft because we had not smelled it while flying except briefly on short final. I believed it to be coming from an outside source.during takeoff and our left turn out; smell became thicker and stronger. Approximately 2-3 miles south; southwest of the field; I reached to turn off the wing landing/taxi lights. The panel containing the switches for the lights; fuses; and other electrical systems was very hot. I turned off the lights.I then [advised ATC] of possible fire on board; and turned left back to the airport. I was confident that we would be able to make it to the airport with little difficulty. FBO personnel came on frequency and asked if we required a fire truck. I responded yes because I was witnessing faint white smoke drifting from the panel with the lighting switches/fuses. I then turned off the master and alternator. We landed without incident; although we were unable to utilize flaps during our approach due to the master being turned off. I had one window open to vent the smoke in the cabin.after braking hard; I pulled off at the first available taxiway and pulled the mixture to cut; throttle to idle; fuel to off; and mags to off. As soon as we stopped; I ordered my passenger to disembark. I took the keys and fire extinguisher with me and ensured that my passenger had cleared the aircraft before leaving myself.FBO personnel met us at the airplane and waited with us until the airport fire truck arrived. The fire department checked the plane; but were unable to find evidence of an engine fire; or a fire still burning. They advised me that they could not positively determine whether an electrical fire was present; as they could not see behind the panel and did not want to risk [powering] the master again. No fuses appeared to be blown. The fire department concurred that the plane was safe to be around and move on the ground; so long as the master was not [powered].with the assistance of FBO personnel; I moved the plane to the ramp for tie down.

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Original NASA ASRS Text

Title: C150 pilot reported returning to departure airport when fumes from the electrical system filled the cockpit.

Narrative: Passenger and I first noticed a very faint burning smell on short final. Smell was very faint. During taxi back to runway; smell became slightly more pronounced but still faint. I did not believe that it was coming from the aircraft because we had not smelled it while flying except briefly on short final. I believed it to be coming from an outside source.During takeoff and our left turn out; smell became thicker and stronger. Approximately 2-3 miles south; southwest of the field; I reached to turn off the wing landing/taxi lights. The panel containing the switches for the lights; fuses; and other electrical systems was very hot. I turned off the lights.I then [advised ATC] of possible fire on board; and turned left back to the airport. I was confident that we would be able to make it to the airport with little difficulty. FBO personnel came on frequency and asked if we required a fire truck. I responded yes because I was witnessing faint white smoke drifting from the panel with the lighting switches/fuses. I then turned off the master and alternator. We landed without incident; although we were unable to utilize flaps during our approach due to the master being turned off. I had one window open to vent the smoke in the cabin.After braking hard; I pulled off at the first available taxiway and pulled the mixture to CUT; throttle to IDLE; fuel to OFF; and mags to OFF. As soon as we stopped; I ordered my passenger to disembark. I took the keys and fire extinguisher with me and ensured that my passenger had cleared the aircraft before leaving myself.FBO personnel met us at the airplane and waited with us until the airport fire truck arrived. The fire department checked the plane; but were unable to find evidence of an engine fire; or a fire still burning. They advised me that they could not positively determine whether an electrical fire was present; as they could not see behind the panel and did not want to risk [powering] the master again. No fuses appeared to be blown. The fire department concurred that the plane was safe to be around and move on the ground; so long as the master was not [powered].With the assistance of FBO personnel; I moved the plane to the ramp for tie down.

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.