What is indicated airspeed (IAS)?

• A. The speed shown on the indicated altitude gauge
• B. The speed shown on the airspeed indicator, uncorrected for errors
• C. The actual speed of the aircraft relative to the ground
• D. The speed required for takeoff

Answer: (B)

Indicated airspeed (IAS) is defined as the speed shown on the airspeed indicator, without any corrections for errors that may be present due to instrument inaccuracies or other factors such as altitude and temperature. It is an important parameter for pilots as it provides real-time information about the aircraft's performance, enabling adjustments for lift, stall speeds, and other critical flight conditions.

While it provides essential data for operational safety, IAS does not take into account variations in air density or instrument calibration, which may affect its accuracy in different flight conditions. Therefore, it's crucial for pilots to understand that IAS is just the output from the airspeed indicator and does not equate to the actual speed of the aircraft over the ground or its true airspeed.

In contrast, the other options relate to different concepts of airspeed or altitude that do not accurately define what IAS is. For instance, the indicated altitude gauge does not measure airspeed at all, and the actual speed of the aircraft relative to the ground is referred to as ground speed, not IAS. The speed required for takeoff is a separate consideration related to the parameters of takeoff performance, not a direct measure of indicated airspeed.