Date: 202105
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Bellanca Aircraft Corp Undifferentiated or Other Model
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Climb
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Reciprocating Engine Assembly
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Pilot Flying; Instructor
Reporter qualification: Flight Crew Flight Instructor; Flight Crew Commercial; Flight Crew Multiengine; Flight Crew Instrument
Human factors: Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Procedure; Aircraft
Primary problem: Aircraft

Narrative: I arrived to the airport of departure (ZZZ) with the owner for a reposition flight. I was referred to this owner within the Bellanca Crusiair community since I had recent time in make and model; and I am an active tailwheel CFI. The day prior to this flight I met with a very competent and experienced Cruisair owner/pilot; who has 600 hours in make and model to refresh me on systems and flying characteristics of the aircraft. 	The new owner and I had briefed the route of flight and pertinent details over the phone the days before; as well as in person prior to pushing the aircraft out of the hangar that morning. I conducted a thorough preflight in accordance with the 'Bellanca Crusiair Senior 13-14 Handbook of Instructions.' I also discussed recent maintenance that was conducted on the aircraft with the local mechanic and owner. I found no discrepancies with Aircraft X and proceeded to enter the aircraft along with the owner for our flight. Engine start was normal; as I saw a prompt rise in oil and fuel pressure. Oil temperature closely followed. Soon after I proceeded to taxi to the run up area for the active runway at ZZZ. A run up showed instruments; flight controls; and the engine to be performing as expected and normally. The aircraft was properly configured for takeoff and I made a radio call on CTAF to indicate we would be departing Runway XX straight out. The take off and climb were normal given the high altitude and density altitude conditions that existed. Upon climb out; and at a safe height; I performed the procedure to switch tanks. Switching the tanks resulted in no issues and fuel pressure and engine power was maintained. Shortly after this time I had leaned the mixture to provide adequate power as we ascended in our climb.	After 5-8 minutes in a cruise climb configuration and on the left tank we experienced an unprovoked gradual reduction in power. This was indicated by a loss of RPM; thrust; and fuel pressure. I quickly enriched mixture; suspecting that the mixture may have creeped out and the engine was running too lean. This did not completely restore the loss of power; but it did not make the situation worse. I lowered the nose and promptly swapped to the right hand tank; which completely fixed the issue. I turned back towards ZZZ so that I would be closer to an adequate landing area and to decide on the continuation of our flight. Another power loss event occurred; this time with the right tank selected; with a slightly more profound loss in power once I was enroute to the airport. After running the engine in this configuration at a safe altitude and within ample gliding distance of the airport I swapped back to the left tank. I was unable to replicate the issue over time and deemed that it could have been a random anomaly; perhaps air in the fuel lines; and proceeded on course. It was also at this time when I received flight following to ZZZ1; from Center. 	After 5-8 minutes in a cruise configuration we experienced the issue again; except this reduction in power was longer and more severe. From this point forward several things happened consecutively in order to keep the engine running. I was swapping tanks to hopefully remedy the issue; excising the wobble pump whenever power loss or fuel pressure was nonexistent; and exercised the mixture and throttle controls. We experienced the power loss events regardless of which fuel tank was selected. I was operating each of these systems independently and deliberately; actively attempting to keep the engine running and hopefully avoiding a possible prolonged power failure. Over time the loss of power was random and increasing in severity. It was also during these actions I informed Center of our situation; but not [requesting priority] at that time. After repeated engine failures that seemed to be gradually increasing in frequency and intensity; where at least two of which caused complete power loss for at least 1-2 seconds; I decided to notify ATC in fear of landing in the barren terrain between us and ZZZ. ZZZ3 Approach provided an accurate heading back ZZZ and timely ASOS information; all of which contributed to the safe outcome of this event. Upon reaching the airport; and after deeming a safe altitude; I performed a deliberate power to idle approach since I could not rely on on-demand power. I performed a tight pattern and landed smoothly on the runway. We taxied off the runway under our own power. I contacted ZZZ3 Approach via the local clearance delivery phone number and by radio to inform that we safely landed. We then proceeded to taxi to the hangar of origination and informed the mechanic of what we just experienced.




Synopsis: Pilot reported engine power loss and elected to return to the departure airport.