Which combination of engine instrument indicators may shift when the anti-icing bleed system is activated?

Which combination of engine instrument indicators may shift when the anti-icing bleed system is activated?

• A. Tachometer, Fuel Flow Indicator, And EGT
• B. Fuel Flow Indicator, EGT, And EPR
• C. Tachometer, EPR, And Fuel Flow
• D. Tachometer, EGT, And Fuel Flow

Answer: (D)

Activating the anti-ice bleed draws air from the compressor, which reduces core airflow and slightly alters the engine’s operating point. That change shows up most clearly in indicators tied to the engine’s speed, temperature, and fuel scheduling. The tachometer reading can shift because spool speed responds to the altered mass flow and compressor characteristics. The exhaust gas temperature changes because the combustion conditions and turbine inlet conditions are affected, and the fuel flow shifts as the engine control adjusts to maintain the desired thrust under the new bleed-loaded condition. EPR, while it can be influenced by changes in compressor discharge pressure, is usually less sensitive to this bleed-induced shift in typical anti-ice operation, so the combination most likely to move is the tachometer, EGT, and fuel flow.

Activating the anti-ice bleed draws air from the compressor, which reduces core airflow and slightly alters the engine’s operating point. That change shows up most clearly in indicators tied to the engine’s speed, temperature, and fuel scheduling. The tachometer reading can shift because spool speed responds to the altered mass flow and compressor characteristics. The exhaust gas temperature changes because the combustion conditions and turbine inlet conditions are affected, and the fuel flow shifts as the engine control adjusts to maintain the desired thrust under the new bleed-loaded condition. EPR, while it can be influenced by changes in compressor discharge pressure, is usually less sensitive to this bleed-induced shift in typical anti-ice operation, so the combination most likely to move is the tachometer, EGT, and fuel flow.