What does the secondary fuel flow cater to during operation?

The correct answer highlights that the secondary fuel flow is designed for more direct fuel usage around 38% Ng, indicating its operational efficiency in specific engine power settings. In this context, "Ng" refers to the gas generator speed, which is a crucial parameter for turbofan engines and indicates how well the engine is operating.

At approximately 38% Ng, the engine achieves a stable operating condition where the secondary fuel flow can optimize fuel delivery to the combustion chamber, enhancing combustion efficiency and engine performance. This is particularly relevant for maintaining engine stability and ensuring that the power output remains consistent and reliable during various phases of flight.

Understanding this relationship between fuel flow and Ng is essential for proper engine operation and management, particularly in Part 135 operations, where efficiency and safety are paramount. By utilizing the secondary fuel flow effectively, pilots can ensure that the engine operates within its designed parameters, promoting longevity and performance under different operational situations.