Which instrument helps pilots maintain airspeed during IFR operations?

The airspeed indicator is a critical instrument for pilots, particularly during IFR (Instrument Flight Rules) operations. It provides real-time information about the aircraft's current speed relative to the surrounding air. Maintaining the correct airspeed is vital for safe flight, especially as it directly influences aircraft performance during various phases of flight, such as climbing, descending, and performing maneuvers.

In IFR conditions, where visibility may be limited, relying on instruments for navigation and control is essential. The airspeed indicator allows pilots to ensure they are flying at a speed that is safe for the aircraft's configuration, such as during climbs or descents, and that they are within the operational limits specified for the aircraft type.

Other instruments, while important for various aspects of flight, do not directly assist in maintaining airspeed. For instance, the altimeter measures altitude above sea level, the vertical speed indicator shows the rate of ascent or descent, and the heading indicator helps pilots maintain a specific course. None of these instruments provide feedback on airspeed, which is why the airspeed indicator is the primary tool used for this purpose.