Slight, but important (if you don't want to run out of fuel) nit, indicated airs... | Hacker News

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		aeijdenberg on Feb 19, 2019 \| parent \| context \| favorite \| on: Boeing 787 Reaches 801 MPH as a Jet Stream Packs R... Slight, but important (if you don't want to run out of fuel) nit, indicated airspeed (KIAS) is not the same as true airspeed (KTAS). To calculate ground speed (as required for navigation and fuel planning) you need true airspeed (not indicated) as well as wind direction and speed. See some discussion here: https://www.quora.com/In-aviation-what-is-the-difference-bet...

TylerE on Feb 19, 2019 [–]

Not so slight. At airliner altitudes they can differ by 50% or so.

IAS is what the pilots care about while flying because it’s what matters for aerodynamics (ie stall speed)

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