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A comment on Boeing 787 Reaches 801 MPH as a Jet Stream Packs Record-Breaking Speeds. Parent comment

Re:Boeing 787 Reaches 801 MPH as a Jet Stream Packs Record-B... by subhro on Tuesday February 19, 2019 @04:45PM (#19203150)
No you are right. In case of tailwind, it is KIAS + WS whereas headwind is KIAS - WS

KIAS: Knots Indicated Airspeed (i.e. the speed at which air is hitting the pitot tube) WS: Wind speed

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Re:Boeing 787 Reaches 801 MPH as a Jet Stream Packs Record-B... by aeijdenberg on Tuesday February 19, 2019 @05:31PM (#19203549)
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...

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Re:Boeing 787 Reaches 801 MPH as a Jet Stream Packs Record-B... by TylerE on Tuesday February 19, 2019 @05:45PM (#19203669)
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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