Date: 202104
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: Government
Operating under: Part 91
Flight plan: IFR
Flight phase: Initial Climb
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Reciprocating Engine Assembly
Component problem: Malfunctioning
Reporter organization: Government
Reporter function: Captain; Single Pilot
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Preflight inspection of the aircraft started at approximately XA:45 am; where fuel was requested from the local FBO. Oil was checked; where 1.5 quarts were put in the aircraft to give it approximately 6.5 quarts of oil. All sumps were drained after the fuel was added; with no water or contaminates noted. The instrument flight plan was filed through foreflight. All control surfaces were examined and shown to be in working order. Engine startup was nominal; with no issues or indications of engine trouble. Taxi clearance was given from the north ramp to Runway X; via taxiway. While taxing out; because of opposite direction traffic on Runway XY; the ground controller asked if I could accept a Runway XY intersection departure; which I agreed to. Takeoff roll was uneventful with full power; and mixture all the way in. Aircraft rotated at approximately 60 kts; after 900 foot takeoff roll. During initial climb out from ZZZ Runway XY; on an assigned 330 heading; passing through 2;500 feet MSL; I noticed a drop of approximately 1000 RPM; with associated engine roughness. I immediately leveled the aircraft; pulled carb heat; and notified ATC with Departure. Engine power did resume while level to it's normal state; but when directed to Runway X by the Departure Controller; followed by a 5 degree descent; the engine roughness and loss of RPM's recreated itself. Due to the engine running rough; I shut down the aircraft after landing where I was met by Airport Fire Rescue personnel; and ZZZ Airport Ops. Aircraft was towed to Maintenance here at the ZZZ; where a thorough inspection of the engine; fuel; oil was conducted. No anomalies were detected or identified; leading to the probability of carb water or carb ice on departure. The weather at the time of the incident was: Temp 68 F; Dewpoint 64 F; Humidity 87%; Wind SSE 3 mph. Baro 29.94 in. Mostly Cloudy. ZZZ Tower and Departure were amazing as always; I consistently fly missions across the state; and appreciate their constant professionalism and willingness to help. A lot of my flights require a lot of coordination with local ATC's; and ZZZ is always top notch!




Synopsis: C152 pilot reported after takeoff that the engine lost power and elected to return to the departure airport and make a precautionary landing.