What engine fault could cause high EGT, low RPM, and high fuel flow at all engine pressure ratio settings?

What engine fault could cause high EGT, low RPM, and high fuel flow at all engine pressure ratio settings?

• A. Compressor surge
• B. Possible turbine damage and/or loss of turbine efficiency due to excessive wear.
• C. Fuel control malfunction
• D. Battery failure

Answer: (B)

The situation points to a turbine that isn’t able to extract energy effectively from the hot gas flow. When the turbine is damaged or worn, its efficiency drops, so less power is transferred to drive the compressor. With the compressor not spinning up as it should, the engine can’t maintain normal speed, so RPM falls. The fuel-control system will respond by increasing fuel flow in an effort to boost speed, which shows up as high fuel flow across all engine pressure ratio settings. Meanwhile, because the turbine isn’t absorbing as much energy, the turbine inlet temperature rises, which shows up as high EGT. So the combination of high EGT, low RPM, and high fuel flow that persists regardless of engine pressure ratio is characteristic of turbine damage or loss of turbine efficiency.

The situation points to a turbine that isn’t able to extract energy effectively from the hot gas flow. When the turbine is damaged or worn, its efficiency drops, so less power is transferred to drive the compressor. With the compressor not spinning up as it should, the engine can’t maintain normal speed, so RPM falls. The fuel-control system will respond by increasing fuel flow in an effort to boost speed, which shows up as high fuel flow across all engine pressure ratio settings. Meanwhile, because the turbine isn’t absorbing as much energy, the turbine inlet temperature rises, which shows up as high EGT.

So the combination of high EGT, low RPM, and high fuel flow that persists regardless of engine pressure ratio is characteristic of turbine damage or loss of turbine efficiency.