What condition will cause a false, high EPR indication, in flight or on the ground?

A false, high Engine Pressure Ratio (EPR) indication can occur when there is a loss of turbine discharge pressure lines. The EPR is calculated using the pressures at the engine's inlet and the turbine discharge. When the discharge pressure line is compromised or lost, it may lead to inaccurate readings being transmitted to the cockpit instruments. This situation causes the EPR gauge to reflect higher pressures than are actually present, resulting in a false high indication.

In proper operational conditions, both pressure lines should function correctly to provide accurate readings. When there is a failure in one or more of these systems, relying solely on the signals from the pressure sensors can mislead crew members regarding the actual performance of the engine. By understanding this relationship, flight engineers can better diagnose potential issues with EPR readings in both flight and ground scenarios.