Incident Overview
On 17 August 2012, a Cirrus SR22 operated by a single professional pilot with a Commercial Pilot License (CPL(A)) experienced an in-flight engine irregularity shortly after departing from Poznań-Ławica Airport (EPPO). The pilot, who had accumulated approximately 1200 flight hours including 300 hours on type, was conducting a cross-country flight.
Sequence of Events
After reaching cruise altitude, the pilot performed a mixture leaning procedure in accordance with the Pilot's Operating Handbook (POH) to achieve an economy cruise setting. Immediately after leaning, the engine began running rough. In response, the pilot enriched the mixture, initiated a descent, and returned to the departure airport. As no further anomalies occurred, a normal landing was executed without incident.
Investigation Findings
Post-flight analysis of the engine monitor data revealed no abnormalities. A subsequent in-depth analysis involving a service station in Schönhagen, Germany, determined that the pilot had reduced the fuel flow to the value specified in the POH while simultaneously maintaining a disproportionately high manifold pressure. This combination caused the engine to run unevenly. The pilot had aimed to achieve a turbine inlet temperature (TIT) of 1600°F or lower, which the operator had recommended as an additional verification step rather than a target parameter. The investigation classified the pilot's action as a piloting technique error that did not pose a safety risk, noting that the pilot's decision to return and land given the concerning symptoms was correct.
Cause
The incident was caused by the pilot reducing fuel flow to the POH-indicated value while maintaining a disproportionately high manifold pressure, leading to rough engine operation.
Preventive Actions
Following the incident, the pilot received additional training on thermodynamic parameter dependencies for engines. The event was discussed during a periodic safety meeting of the operator's flight department.