Which engine indicator is likely impacted by engine failure but not typically by PMU failure?

The N1 indicator, which reflects the speed of the fan or low-pressure compressor in a turbofan engine, is the correct choice because it is directly influenced by the engine's operational status. In the event of engine failure, you would expect to see a significant change in the N1 reading, as the engine would not be producing thrust or generating the necessary airflow.

On the other hand, the PMU (Power Management Unit) primarily manages engine performance and operational parameters by controlling fuel flow, ignition timing, and other factors. While PMU failure can certainly cause irregularities in engine performance, it does not directly lead to an engine failure or cause a change in the N1 indicator. Instead, PMU failure might still allow the engine to continue operating at a lower efficiency or with unoptimized settings. The impact of an engine failure would manifest as a loss of N1, distinguishing its direct relationship with engine health compared to other indicators like temperature, RPM, or fuel flow, which may not directly reflect engine failure in the same way.