What sensory indication is associated with engine fire in flight?

The presence of smoke and fumes is a direct and observable sensory indication of an engine fire during flight. Visual cues are often the first indicators pilots can recognize, as smoke can fill the cockpit or be seen trailing from the aircraft. This immediate observation alerts the crew to a potential fire, prompting them to take emergency procedures to ensure safety.

Other options might indicate irregularities in engine performance or system malfunctions, but they would not specifically point to an engine fire as clearly as visual indications do. For instance, a lower Np might suggest a performance issue but is not definitive for fire; similarly, the PMU FAIL light indicates a system malfunction, and a power step change could be associated with various operational issues. However, none of these provide the unmistakable and urgent clue that visual signs of smoke and fumes do, making them less relevant in identifying an engine fire in flight.