Narrative:

Instructor and passenger were traveling northeast from ZZZ on a training flight; approximately 20 miles north-east of ZZZ; a large amount of smoke was encountered in the cockpit. Instructor immediately closed cabin heat vent; and secured all non essential electronics and opened the windows and cabin vents; executed a 180 degree turn; flew back towards ZZZ and [advised ATC]. Upon completion of the initial actions; smoke in the cockpit was vacuumed out of the cabin and whatever component that was causing it seemed to have been secured; as the smoke stopped. No further issues nor injuries occurred. Upon landing; the plane was taxied back to [FBO] where it was secured and evacuated until cleared by the local fire chief. Upon the chief clearing the aircraft; it was tied down; chocked; and is awaiting further action by [FBO] personnel.

Google
 

Original NASA ASRS Text

Title: C-172 Flight Instructor reported encountering smoke in the cockpit and returning to departure airport.

Narrative: Instructor and passenger were traveling northeast from ZZZ on a training flight; approximately 20 miles north-east of ZZZ; a large amount of smoke was encountered in the cockpit. Instructor immediately closed cabin heat vent; and secured all non essential electronics and opened the windows and cabin vents; executed a 180 degree turn; flew back towards ZZZ and [advised ATC]. Upon completion of the initial actions; smoke in the cockpit was vacuumed out of the cabin and whatever component that was causing it seemed to have been secured; as the smoke stopped. No further issues nor injuries occurred. Upon landing; the plane was taxied back to [FBO] where it was secured and evacuated until cleared by the local fire chief. Upon the chief clearing the aircraft; it was tied down; chocked; and is awaiting further action by [FBO] personnel.

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.