When is the "Reference RPM" of an engine established?

The "Reference RPM" of an engine is established by the engine's manufacturer during "Type Testing." This process involves thorough evaluations and performance assessments of the engine to determine its operational characteristics, including the RPM at which it achieves optimal performance. During Type Testing, various parameters are documented, ensuring that the engine meets safety and performance standards before being approved for use in aircraft. Once established, the Reference RPM serves as a benchmark for pilots and maintenance personnel to monitor engine performance during operation.

Setting the Reference RPM during the initial installation of the engine would not provide the necessary data derived from comprehensive testing under controlled conditions. Therefore, it is recognized that manufacturers specify this function based on their in-depth testing and validation processes.