How does a speed indicator differ from a mach meter?

• A. The speed indicator shows ground speed
• B. The speed indicator measures airspeed
• C. The mach meter shows altitude
• D. The mach meter measures true airspeed

Answer: (B)

The speed indicator is primarily designed to measure airspeed, which is the speed of an aircraft relative to the surrounding air. This measurement is crucial for flight operations as it helps pilots assess performance, control the aircraft, and maintain safety margins. Airspeed is indicated in knots or miles per hour and is essential for determining stall speed, climb performance, and other aerodynamic characteristics.

In contrast, a mach meter measures the speed of the aircraft relative to the speed of sound, allowing pilots to understand how fast they are traveling compared to that critical threshold. The Mach number is dimensionless and is relevant at higher altitudes and speeds, where changes in pressure and temperature can significantly affect performance. Understanding both airspeed and Mach is vital, but the core distinction lies in airspeed measurement being tied to the flow of air around the aircraft rather than the conditions or altitude.

Overall, the ability of the speed indicator to display airspeed directly supports vital operational parameters that are critical for safe flying, which is why the correct answer focuses on that aspect.