Which instrument is crucial for measuring the speed of an aircraft?

The airspeed indicator is essential for measuring the speed of an aircraft. It specifically provides the pilot with information about the speed of the aircraft relative to the surrounding air, which is critical for safe operation during takeoff, flight, and landing. The reading on the airspeed indicator helps the pilot make necessary adjustments to ensure optimal performance of the aircraft, enhancing safety and efficiency.

In contrast, the altimeter measures the aircraft's altitude above sea level, which is vital for maintaining safe vertical separation from terrain and other aircraft. The attitude indicator shows the aircraft's orientation relative to the horizon, helping pilots understand whether the wings are level, climbing, or descending. The heading indicator provides information on the aircraft's current direction relative to North, ensuring that the pilot can navigate effectively. While all these instruments are important for flight operation, the airspeed indicator is specifically designed to gauge the speed of the aircraft, making it the most crucial for that purpose.