Airspeed Indicators

The airspeed indicator relies on two essential components: the pitot tube and the static port. The pitot tube is mounted on the aircraft's exterior and faces forward into the relative wind. It measures the pressure created by the airspeed. The static port, also mounted on the exterior but typically on the side of the aircraft, measures the static air pressure.

As the aircraft moves through the air, the pitot tube captures the dynamic pressure created by the airspeed. This dynamic pressure results from the difference between the total pressure (captured by the pitot tube) and the static pressure (measured by the static port).

Inside the airspeed indicator, the dynamic pressure from the pitot tube is compared to the static pressure from the static port. The instrument uses this pressure differential to calculate and display the indicated airspeed (IAS) on the airspeed indicator's dial.

Different speeds are required for various stages of flight, such as takeoffs, climbing, cruising, and landing. Accordingly, the pilot must remain within safe speed limits during each of these stages to avoid stalling and to ensure proper lift generation. The airspeed indicator generates a real-time reading of the aircraft's speed, which helps pilots adjust accordingly.

In addition, flying at optimal airspeeds for the specific aircraft and current conditions helps optimize fuel consumption. Airspeed is also a key factor in calculating distances and time over ground, which helps pilots navigate effectively.

There are two main types: analog airspeed indicators and digital airspeed indicators.

Analog airspeed indicators – also called mechanical airspeed indicators – use diaphragms and linkages to translate pressure differences into needle movement on the airspeed gauge.

Digital airspeed indicators – sometimes called electronic airspeed indicators – use sensors and computer processing to display the airspeed on a digital display. These readings may also be integrated into a multifunction display.