Definition
A cockpit airspeed instrument that displays true airspeed directly, automatically correcting indicated airspeed for pressure altitude and outside air temperature. The pilot sets the current pressure altitude opposite the outside air temperature on a small subscale, and the instrument's inner scale then reads true airspeed without the need for a separate flight computer calculation.
Plain English
An airspeed gauge that shows your real speed through the air, not just what the simple airspeed dial reads. You set the altitude and temperature on a small dial, and it does the math for you.
Context Anchor
Seen when studying types of airspeed and when comparing cockpit airspeed indications with flight planning speeds.
Derivation
True airspeed is called "true" because it is the actual speed of the aircraft through the surrounding air mass, as opposed to indicated airspeed, which is what the basic instrument shows before corrections.
Why Pilots Care
Accurate true airspeed supports navigation, performance planning, and fuel management especially at altitude.
Grounding Statement
As the airplane climbs into thinner air, the basic airspeed indication may stay the same while the airplane’s actual speed through the air is higher.
Intuition Check
Do not read “true” as meaning “more legal” or “more important.” Here it means the airspeed corrected to show the airplane’s actual speed through the surrounding air.
Example Sentence 1
After leveling off in cruise, the pilot set the pressure altitude against the outside air temperature on the TAS indicator and read the true airspeed directly.
Example Sentence 2
With the TAS indicator set for current temperature the crew calculated precise groundspeed for the leg.