Airspeed

An aircraft's speed is measured in one of three ways:

• Indicated Airspeed (IAS): This shows the speed of the aircraft as measured by onboard instruments. IAS is influenced by air density and wind. As an aircraft climbs and the air becomes less dense, the same amount of air molecules passing over the pitot tube results in a lower IAS. It's the most relevant speed for determining aerodynamic behavior of the aircraft, like stall speeds, takeoff, and landing speeds.

• True Airspeed (TAS): This shows the speed of the aircraft against the wind, but compensated for density. This can be calculated based on the IAS and the altitude.

• Ground Speed: This shows the speed of the aircraft against the ground. In other words, it shows how fast your aircraft is moving on the NAV page. This measurement ignores the effects of wind. This is the same speed that would be measured by GPS.

In reality, some of these measurements are also affected by air temperature, as well as the rotation and curvature of the Earth. However, these are not modeled in VTOL VR.

In VTOL VR, the speed gauge in the cockpit and on the HUD show IAS, whereas the Mach indicator on the HUD is based on ground speed. TAS is generally not used.