Commercial Pilot License (CPL) Practice Exam

Leaning the mixture for optimal engine performance is a crucial aspect of managing fuel efficiency and engine temperature. The correct approach is to lean until power peaks and then enrich slightly to ensure smooth operation. This method allows the pilot to find the ideal fuel-to-air ratio, maximizing combustion efficiency and power output while preventing engine roughness.

When the mixture is leaned to the point where the engine reaches its peak performance, the pilot can then enrich the mixture slightly to provide a margin that promotes smoother engine operation and prevents the risk of engine knocking or roughness that could occur if the mixture is too lean.

Other options provide less effective strategies. For instance, leaning until the engine stops can lead to damage or incomplete combustion, while leaving the mixture unchanged during flight can result in suboptimal performance and fuel usage. Leaning continuously during ascent may not be appropriate as it can lead to improper fuel-to-air ratios that vary with altitude and engine demands. Therefore, the method that involves leaning to the power peak and then enriching for smoothness offers the best balance of performance, efficiency, and engine health.