What are the visual indicators of a possible engine failure during flight?

The visual indicators of a possible engine failure during flight are characterized by specific symptoms that can be directly observed or inferred from the aircraft's performance and instrument readings. Loss of power is a primary indication of engine failure; a sudden decline in thrust can be felt by the pilot through the lack of acceleration or a decrease in climb rate. Unusual vibrations may also accompany an engine failure, often signaling mechanical issues or instability within the engine. Abnormal readings on engine instruments, such as tachometer, manifold pressure, or temperature gauges that deviate from normal limits, further support the possibility of an engine malfunction.

Recognizing these signs is crucial for pilots as they must react swiftly and effectively to ensure safety and manage the situation appropriately. The other choices do not provide raw indicators of immediate engine failure. For example, an increase in fuel consumption may not directly indicate an impending failure, and steady altitude and airspeed would suggest normal operation rather than an issue. Unexpectedly high oil temperature could signal an issue but isn't as definitive or comprehensive as the broader range of symptoms enumerated in the selected answer.