Situational Awareness
Aircraft Equipment Problem Critical
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution
Aircraft
During run up plane showed no signs of malfunction; both mags were [within] standards. After takeoff at about 1100 ft crew contacted Departure and were instructed to climb at or below 2500 ft and resume navigation. As soon as the student added power and started climbing; IP (Instructor Pilot) heard a noise like something popped. Immediately IP looked at the RPM gauge and saw it drop to 2300 first and then to 2000. At that point IP took controls [and] tried to climb as much as [possible] since the aircraft was at a good distance from the airport. At the same time IP contacted Departure and requested to go back to [departure airport]. They asked if any assistance was required and IP said negative just need to be back. At that point Departure asked if we needed a straight in. The plane had started to lose altitude and the RPM kept dropping. At that time IP told Departure we need direct [to the airport] and we were fully aware that [the airport] was using [west runways] at the time but IP requested to use [east runway] since it was the closest and the plane kept shaking and was hard to maintain altitude. They cleared us and then Tower cleared us to land. As soon as the plane feels abnormal turn to an airport and land as soon as practical.
C172 Instructor Pilot reported returning to departure airport after the engine began to lose power.