Definition
Indicated airspeed (IAS) is the speed of an aircraft as shown directly on the airspeed indicator, before any corrections for instrument error, installation error, air density, or compressibility. It is derived from the difference between ram air pressure (from the pitot tube) and static air pressure, and is calibrated to read true airspeed under standard sea-level conditions. In the context of aircraft approach categories, IAS values such as VREF or 1.3 VSO at maximum certificated landing weight are used to assign each aircraft to a category (A through E) that determines applicable approach minimums.
Plain English
It's the airspeed number you actually see on the cockpit dial. It's not corrected for anything — it's the raw reading. For approach categories, the FAA uses this raw landing-approach speed to sort aircraft into groups that determine which approach minimums apply.
Context Anchor
Seen in instrument procedure charts and approach-category discussions, where aircraft are grouped by speed for approach planning.
Derivation
‘Indicated’ comes from the Latin indicare, meaning ‘to point out’ or ‘show.’ It’s literally the speed the instrument is pointing to — what it indicates — with no corrections applied. That helps distinguish it from calibrated, true, and groundspeed, which are all derived by adjusting the indicated value.
Why Pilots Care
Aircraft approach categories, minimum speeds, and many performance limits are defined using indicated airspeed.
Intuition Check
Do not read “indicated” as “actual in every way.” Here it means “shown on the airspeed indicator,” not corrected speed and not speed across the ground.
Example Sentence 1
The aircraft’s VREF is 120 knots indicated airspeed, placing it in approach Category B.
Example Sentence 2
Aircraft approach category is based on the maximum IAS at maximum landing weight.