Date: 201506
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: M-20 K (231) / Encore
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Initial Climb
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Reciprocating Engine Assembly
Component problem: Improperly Operated
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Instrument; Flight Crew Private
Human factors: Distraction; Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Human Factors

Narrative: I had completed all pre-takeoff checks; VMC and winds were calm; departing RWY XY (no obstacle Departure procedure) and was number 2 for takeoff and taxiing to hold line with tower closed; with intent to pick up my IFR clearance once airborne. The number 1 aircraft was slow to depart; and the tower became active and I stopped in place and requested my IFR clearance.  Tower informed me that I now had to depart on RWY X.  I ground leaned and taxied to RWY X; and picked up a rather involved clearance which included an obstacle Departure procedure and unusual routing involving a transition from one V-way to another without a waypoint at the intersection (something I never had run across; and after questioning; was told was normal procedure). After figuring out how to enter the unusual clearance; entering and then reviewing the Departure procedure and clearance in navigational avionics; I re-did my take-off checklist and reported ready for departure; and was cleared for takeoff.In the Mooney 231; there is no automated engine management system; so close monitoring of manifold pressure is required.  This was done; and the takeoff seemed normal in all aspects. Wheels left the ground at mid-field and once airborne with positive climb; the wheels where retracted and verified; and minimum climb rate of 400 FPM per the Departure procedure was verified to be exceeded and noted to be 700 FPM; which was lower than expected. Normal climb rate is expected to exceed 1000 FPM; and first manifold pressure was checked to be just under the normal 40 inches; then fuel flow was checked and observed to be 12-13 GPH; significantly less than the normal 22-23 GPH. An immediate report was made to tower (at about 200-300 feet AGL on initial climb) indicating a low fuel flow indication; followed by a second request to return for landing to investigate after the cause was not immediately known. Tower was asking questions about my situation when I noticed engine temperatures were now rising above normal levels. With a second indication of an engine related problem; I immediately pulled power back. Simultaneously tower asked if I wanted runway X or XY; and I responded I wanted RWY X since the obstacle Departure procedure had put me in a very favorable position to enter directly into a right downwind for RWY X. Once leveled off and at mid-field with reduced power on downwind; the mixture was observed to be in the ground leaned position and was immediately placed to full rich. Landing was completed uneventfully; and a run up check was requested and granted by Tower. All systems checked out normally. A problem with the mixture setting was reported to the Tower as the cause; and that it had been corrected. Tower reported my IFR clearance was still active; and a normal departure was executed.The chain of events that started with all checklists having been completed; followed by Tower becoming active and ordering a lengthy taxi (which ground leaning was normal procedure); followed by the confusion of sorting out a complex obstacle Departure procedure and clearance involving a transition from one V-way to another without the presence of a common waypoint - all created an extended time frame and distraction that facilitated not recalling the ground leaning - then executing a takeoff checklist that did not include a check that mixture is set to full rich (this check was done at the conclusion of the run up checklist - which was not repeated) all contributed to the event; which ultimately was a case of pilot error. Corrective actions were to add a mixture check to the takeoff checklist; and to closely monitor fuel flow on initial power up; as well as manifold pressure.




Synopsis: M20K pilot experiences a lengthy ground delay during which time the mixture is ground leaned. Once cleared for takeoff the mixture is not returned to full rich; resulting in low power and rising temperatures. During the return the lean mixture setting is detected and corrected prior to landing.