Terry Hunter
Silence!
- Joined
- Nov 22, 2004
- Posts
- 297
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Generally, aircraft that cruise at FL300 and above, and normally cruise at .75M and above have an indicated speed in the low to mid 200kt range. As they descend, they fly a constant Mach number, but the indicated speed increases. Once that Mach number matches a particular indicated speed, then that indicated speed is maintained.
The Mach number cannot be maintained at some point because it eventually will increase above the barber pole. There's no flying above that of course.
Typical indicated speeds that are maintained range from 280-340kt. If ATC wants a particular speed, so be it. Hope that helps.
macdu is correct, between FL270 and FL280. Technically a mach number can be assigned lower than that, and an indicated airspeed higher than that, but it's usually only if they're climbing/descending into the preferred regime.
PilotYip, not sure where you get FL240 from but that's a bit low to be used as a "standard". There isn't an arbitrary transition altitude between high and low sectors.