Under what condition can the Maximum Operating Range (MOR) be used?

The Maximum Operating Range (MOR) can be used above 50% Ng (N1) because at this setting, the engine operates efficiently and within its designed parameters for maximum output and performance. The MOR is specifically defined to ensure that the engine does not exceed operational limitations while still providing optimal thrust for the aircraft. Operating the engine above 50% Ng allows pilots to utilize the engine's capabilities without straining the engine or causing undue wear.

Utilizing the MOR while below 50% Ng could result in reduced performance and potential issues with engine efficiency. Similarly, stating that the MOR is valid at any altitude may not account for specific operational limitations and performance constraints that vary with altitude. The restriction of using MOR during cruise operations only does not encompass the full range of operational contexts where the MOR is applicable, as it can also be utilized in other phases of flight, provided that the Ng condition is met.