In order to use engine sync, the engines should be within what percentage?

Using engine synchronization in multi-engine aircraft is crucial for maintaining smooth and efficient operation. For effective synchronization, the engines need to be operating very closely in terms of RPM, as even small discrepancies can lead to vibrations, inefficient fuel consumption, or uneven thrust.

The industry standard for synchronizing engines typically allows a difference of up to 1.5% in RPM. This specific percentage is critical because it strikes a balance between ensuring optimal performance and minimizing potential issues that arise from larger disparities in engine output. Keeping the engines within this narrow range allows the pilot to achieve smoother operations and enhance overall performance, which is why this value is recognized as the correct threshold for engine synchronization.

While other percentage choices might suggest slightly larger tolerances, they would not align with the best practices for engine management, where precision is paramount to avoid complications.