What are some indications of an engine failure in flight?

The choice that highlights loss of power or airspeed as an indication of engine failure in flight is significant because it directly correlates with the performance and functionality of the aircraft's propulsion system. When an engine fails, there is often a noticeable decrease in thrust, which leads to a commensurate drop in airspeed. Pilots are trained to recognize these critical changes during flight as they signal that something may be wrong with the engine, making this observation crucial for maintaining control of the aircraft.

Visual indications like smoke and fumes, while they may also indicate an issue, are often secondary signs that may not occur in all engine failures. Similarly, a lack of Np (propeller speed) indication can be a consequence of engine failure or other factors, and excessive turbine temperature can indicate engine stress but does not directly confirm a failure. Thus, the loss of power and airspeed serves as the most immediate and clear indicator of engine malfunction, making it vital for pilots to be alert to these changes during flight.