Date: 202011
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Climb
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Reciprocating Engine Assembly
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Instructor; Pilot Not Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument; Flight Crew Flight Instructor
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Aircraft Aircraft Damaged; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: During a clear day; and after long taxi; we conducted a standard engine Run Up and the aircraft performed flawlessly with strong power output. We were eventually cleared for takeoff and after an uneventful takeoff from Runway XX. Runway XY was CLOSED at ZZZ. Approximately 7 miles north I began to notice that the engine was performing slightly lower than usual. Within moments I saw the RPM drop to 2100 and the engine was 'rumbling'. I executed the emergency checklists at this time; mixture rich; carburetor heat on and power forward and it provided only slightly better performance but not much. I immediately called the Tower and advised them of the engine problem. The tower immediately acknowledged and I continued to bring the aircraft to best glide speed and trouble shoot. I know my aircraft usually likes to run lean so I tried leaning the mixture and it got worse so I immediately enriched the mixture and held it full forward as much as possible and the engine was performing better. In addition I saw that carburetor heat was producing no result so I turned off the carburetor heat and with Throttle; Mixture full forward and carburetor heat off; I was able to sustain over 2300 RPM without any engine shaking. I did a quick scan of the area; and calculation of winds aloft and looked back and saw that indeed I could likely make the ZZZ airport and at worst would have to land on XZ or runway XY; the closed runway but which was mostly vacant. I also calculated and knew; that the winds aloft were quite strong over 3000 ft. so I used full power to climb; catch the southerly winds and return immediately for the airport. I advised ZZZ of my intentions and they said that they would clear the area for me. At all times I was able to climb and if I touched the power controls to reduce them; there would be a decrease in power with more vibration; but at full power I was able to sustain good engine power. My climb worked and stronger winter winds aloft indeed pushed me back into downwind; albeit well above pattern altitude. Nonetheless; I determined that altitude would be the safest option since it would ensure ability to glide to the airport. I was cleared to land and the tower reiterated that the airport would be cleared for me.It is possible during this climb I may have slightly penetrated Class B area above ZZZ but it is not likely as the FlightAware and my handheld GPS did not indicate I reached that altitude. During the process I was always in contact with ZZZ and they had positive ID of my aircraft; so I did not squawk 7700 as I was concerned about moving my hands from the console. Eventually; when I was on a close downwind with landing assured and the only way to slow down to VFE would be to point the nose up as I did not want to risk pulling power and not regaining it. This technique worked and I safely deployed the flaps within operating limitations. I turned base and then final as I eventually deployed additional flaps and cut power. I advised the tower I would be landing and doing some S turns to descend. Landing was uneventful; on the runway just after the numbers. I was able to taxi under my own power however; my mechanic told me he was later unable to restart the engine; most likely due to engine failure. I believe the tower did an amazing job. I also did not hesitate to tell them my intentions. If at any time I thought I would not be able to circle back to Runway XX; I would have easily made Runway XZ or Runway XY if necessary. I do not believe that there were any deviations whether it be owner/operator/pilot related; or mechanical or ATC. It is my belief that everyone did what they had to. My mechanic did run compression checks and other diagnostic tests which are still in progress and the most likely issue was fuel starvation caused by the carburetor. I have acquired a refurbished one recently which will be inspected and installed and; once installed a complete diagnostic will be done once again to determine whether there were other issues.




Synopsis: Flight Instructor reported precautionary landing due to engine problems.