3 ms·
Really depends on the context. Usually things that were designed for pilots to use will display ground speed in knots since it's likely the pilot will be compar
by jcrawfordor 5y ago
Really depends on the context. Usually things that were designed for pilots to use will display ground speed in knots since it's likely the pilot will be comparing against calculations done in knots. Things that were designed for the general public usually show mph since most people don't have a good sense of how fast a knot is.
Taxi speeds are always written in knots, so I suppose you could say it is "official" (in terms of aircraft handbooks, airfield directories, etc) to use knots for ground speed. Of course the situation of an aircraft's ground speed while on the ground is sort of an edge case.
On the topic of odd units, the operating handbooks for jet aircraft often use mach number for limits, which has some of the same properties as KIAS as far as being density dependent but is a little more precisely defined.
- mulmen 5y ago> So that when kph/mph is heard a pilot knows they're referencing ground speed, whereas knots is air speed. Who is using MPH/KPH in the course of flying a plane? Why would this ambiguity resolve to “that must be ground speed”? Why would there be ambiguity in a speed readout at all? Surely context and procedure should disambiguate this rather than units?
- jcrawfordor 5y agoI'm not actually sure where that quote came from, but yes, there's not likely to be much confusion. Ground speed is usually displayed by some kind of computer, could be a glass panel or just an aviation GPS unit, and is usually marked "GS" or "Kts Ground." And it's sort of considered, philosophically, to be more a navigation thing than an actual flight instrument, since you only really pay attention to it in flight if you're doing navigation calculations.
- mulmen 5y agoThat quote came from the post I replied to originally. Beyond that I’m unsure of the source.