Skyhawk 172/Cutlass 172
Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Commercial
Aircraft Equipment Problem Critical
Flight Crew Returned To Departure Airport
Aircraft; Equipment / Tooling
While conducting slow flight at 2;500 feet with the carb heat on; the engine began to run very rough suddenly. The crew cycled the magnetos; adjusted the mixture; adjusted the throttle; and cycled the carb heat off then back to the on position. Nothing that the crew did improved the vibration. Given the recent history of the aircraft; the decision was made to immediately return and the PIC contacted ATC; announced his intention and was provided instruction to return to ZZZ. The crew remained at their current altitude at normal cruise power with carb heat on until landing was assured and made an uneventful landing on Runway XXL.
C172 pilot reported rough running engine and returning to destination airport.