When reducing power, what is the recommended sequence for using the manifold pressure and RPM controls?

The recommended sequence of reducing power is to lower the manifold pressure first, followed by lowering the RPM. This practice helps to ensure the engine operates within its optimal parameters and protects it from potential damage due to sudden changes in power settings.

When you reduce manifold pressure first, you lower the engine's power output while maintaining a suitable RPM. This prevents the engine from running too lean or too rich, which can happen if the RPM is reduced without first addressing manifold pressure. It also minimizes the risk of engine roughness or potential backfiring, as a sudden drop in RPM with high manifold pressure can disturb the fuel-air mixture, leading to a less stable engine operation.

Reducing RPM afterwards allows for a smoother transition and helps maintain engine health. This sequence is particularly important for aircraft with variable-pitch propellers, where changes in RPM can significantly affect thrust and engine load.

This method not only aids in maintaining better engine efficiency, but it also supports safer flight operations. In certain aircraft, adhering to this sequence aligns with manufacturer's recommendations and standard operating procedures, ensuring pilots are operating within the designed parameters.