Which symptom indicates the compressor may be contaminated or damaged when attempting to reach takeoff thrust?

Which symptom indicates the compressor may be contaminated or damaged when attempting to reach takeoff thrust?

• A. Uncommanded large EPR rise
• B. Normal operation
• C. No effect
• D. Unable to reach takeoff EPR before EGT limit

Answer: (D)

When you’re trying to reach takeoff thrust, the engine should develop the specified thrust level by achieving the takeoff EPR while staying within the EGT limit. If the compressor is contaminated or damaged, airflow to the compressor is restricted, so the engine can’t generate the required pressure ratio to hit the takeoff EPR. As a result, you’ll hit the EGT limit before the takeoff EPR can be reached. This combination—unable to reach takeoff EPR before reaching the EGT limit—signals an issue with the compressor’s airflow, consistent with contamination or damage.

When you’re trying to reach takeoff thrust, the engine should develop the specified thrust level by achieving the takeoff EPR while staying within the EGT limit. If the compressor is contaminated or damaged, airflow to the compressor is restricted, so the engine can’t generate the required pressure ratio to hit the takeoff EPR. As a result, you’ll hit the EGT limit before the takeoff EPR can be reached. This combination—unable to reach takeoff EPR before reaching the EGT limit—signals an issue with the compressor’s airflow, consistent with contamination or damage.