What is the limitation of using the Maximum Operating Range (MOR)?

The correct option highlights that the Ng, or the gas turbine engine speed expressed as a percentage, must be above 50% when operating within the Maximum Operating Range (MOR). This limitation is crucial because running an engine below this threshold can lead to insufficient airflow and fuel delivery, potentially causing the engine to stall or perform inefficiently. Maintaining Ng above 50% ensures the engine operates within optimal parameters, maximizing performance and reliability during specific flight regimes.

Understanding the significance of Ng ensures that pilots comply with the operational limits set by the manufacturer and regulatory bodies, maintaining safety and efficiency throughout the operation.