High altitude low IAS

Why when I’m flying the challenger 350 At flight level 450 my IAS is super slow

Have you tried steep climbing?

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Some times

When you say low IAS what exactly are you at?

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190 kts ias

If your cruise is FL450 I recommend going FL230-> FL300-> FL370 and then FL450. At each altitude check if your speed doesn’t go close to stalling. If at FL450 the problem percists, then lower to an altitude of FL420 or FL410.


Just tested this myself in a solo session. This is completely normal. The indicated airspeed decreases the higher up in altitude you are. This is due to the decrease in air density at higher altitudes. At 45,000ft the Challenger 350 is still capable of staying somewhat close to its average cruise speed of around mach .80-.82. At this altitude the IAS will display around 190kts.


190kts IAS is about right at FL450.


You feel like you’re flying slowly, but it’s normal speed. Btw, I missed the Cessna citation x.

IAS (or indicated airspeed) is measured using air pressure. That means that the higher you go in the atmosphere, the lower your indicated airspeed becomes. True airspeed is your indicated airspeed you are currently flying but at sea level. And your groundspeed is your true airspeed plus or minus the current winds (a headwind decreases groundspeed and a tailwind increases it)

what’s your mach decimal? thats how u can tell whether u doin a normal speed

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Good to know

As others have said, IAS is pressure speed so drops with altitude.

Check out just how thin the air is at FL450 compared to sea level.

It’s dropped to less than 20% of what is was!:

Which of course is why the cabin pressurization system is critical.

Low earth orbiting spacecraft are put high enough that, at the necessary GS of 17,000mph their IAS has dropped to nearly zero (orbits decay because there is still a tiny trace of atmosphere).


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