What does the airspeed indicator measure?

• A. The speed of the aircraft relative to the surrounding air
• B. The altitude of the aircraft
• C. The vertical speed of the aircraft
• D. The heading of the aircraft

Answer: (A)

The airspeed indicator measures the speed of the aircraft relative to the surrounding air. This measurement is crucial for pilots as it provides essential information regarding the aircraft's performance and helps in ensuring safe operation. The indicated airspeed (IAS) is derived from the dynamic pressure of the air entering the pitot tube, which is then compared to the static pressure of the surrounding atmosphere.

This information allows pilots to assess their flight conditions, such as stall speed and maneuverability. Understanding the relationship between airspeed and how it relates to airflow around the aircraft is vital for effective control and safety during all phases of flight. Other choices, such as altitude, vertical speed, or heading, are measured by different instruments and do not pertain to the function of the airspeed indicator.