If front engine EPR probes are blocked, the take-off EPR gauge will indicate what relative to actual thrust?

• A. Gauge Reads Lower Than Actual Thrust
• B. Gauge Reads Equal To Actual Thrust
• C. Gauge Reads Higher Than Actual Thrust
• D. Gauge Cannot Provide A Reading

Answer: (C)

Engine pressure ratio gauges estimate thrust by comparing downstream pressure with upstream pressure measured by probes near the engine face. If the front EPR probes are blocked, the upstream pressure reading becomes lower than the actual pressure. The downstream pressure reading remains correct, so the ratio shown by the gauge increases. In other words, the gauge will indicate more thrust than the engine is actually producing. This bias happens because the denominator (the upstream pressure) is reduced by the blockage, making the overall ratio appear larger.