If the bleed valve fails to close after engine start, what is the expected change in exhaust gas temperature (EGT)?

• A. EGT Rise
• B. EGT Fall
• C. No Change
• D. EGT Fluctuation

Answer: (A)

When a bleed valve remains open after engine start, air is diverted away from the engine core. That reduces the core mass flow, so to keep the engine developing the same speed or thrust, the fuel control tends to inject more fuel relative to the available air. With more fuel in a smaller amount of air, the combustion temperature rises, causing the exhaust gas temperature to increase. In short, the open bleed path makes the core hotter for the same operating setting, so EGT goes up. If the bleed valve were functioning properly and closed, more air would enter the core and the same fuel would produce a cooler, more normal EGT. A fall or no change wouldn’t align with the situation of continued air leakage from the compressor, and fluctuations would be less predictable than the consistent rise caused by reduced core airflow.