Knots to airspeed?

Afternoon y’all, today I was wondering if there is a way to instantly change the “speed” setting from knots to mach. I know that after flying above 280, it changes from knots to mach, but is there any way to change the speed in the autopilot from knots to mach instantly? Thank y’all, have a great day/night.

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Not really, not in IF that I’m aware of.

However a rule of thumb for conversion, is that the speed of sound = 666 knots. (Actually 667, if you really round up the decimals but I like to remember 666 more haha)

Do you know a conversion for one mach to airspeed?

Assuming you are cruising at M0.85
Your speed would be 566kts(But below 28,000ft set your speed to 320kts)

M1.0 is the speed of sound so 666kts like what @CaptainSooraj said

In the HUD view, you can see your speed in Mach during all the flight.

Hope this helps?

You can also view the Mach speed in the Primary Flight Display in live cockpits

I am a little confused by this but ok! 🙂

I dont think there is a way to change it from knots to mach on demand as several people have said above. However you can calculate it as long as you have the OAT(outside air temperature)

Fun fact: speed of sound is solely dependant on temperature. Air pressure, or the change of altitude has no impact on the speed of sound whatsoever.


Speed of sound changes with altitude because temperature changes with altitude. Mach 1 speed is something like 13% less around FL300 than at sea level.

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But even still it’s the temperature changing it, not the altitude

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Yes, it’s because of the temperature changing with altitude, not because of pressure dropping off with altitude. So it’s not true to say speed of sound doesn’t change with altitude. There is a regular decline in temperature that is altitude dependent. Altitude causes a predictable change in speed of sound.

Only for an ideal gas

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