What is mach speed (explained)

What is mach speed and why don’t we use kilometres or miles when talking about the speed of sound
Well first of all why don’t we use kilometres/miles per second because the speed of sound can change in different climates and can cause the actual speed of sound to change, so let’s say the speed of sound is 900 kilometres per second in Sydney but in Denver Colorado it could be 600 kilometres per second (this scenario is probably not likely)
So why does mach speed work if the speed of sound can change ? Well think of it as percentage of the speed of sound so 0.85 mach speed is 85% of the speed of sound at any time climate
Thanks for reading and I hope you learned something


These links can also assist with the explanation in your topic.

Keep in mind that you can also find lots of resources on Google. :)

He actually posted it so that others would know what Mach Speed is. He wasn’t asking.


Here’s a helpful link with further explanation: https://aviation.stackexchange.com/questions/35408/what-is-the-reason-for-changing-the-speed-reference-ias-or-mach-number-with-al


The aircraft climbs at 250 kias from sea level. An acceleration from 250 to 300 kias is included at 10,000 feet. You can see that as IAS is held constant, TAS (True Airspeed) and Mach both increase.

The switch from 300 IAS to Mach 0.76 is done at FL280. You can see the Mach speed is approaching its MMO. From this point, both TAS and IAS decrease. After the tropopause, around 35000 feet, temperature stops decreasing and TAS remains nearly constant.

At FL400 the aircraft levels off and cruises at Mach 0.765, and a step climb to FL410 is included at this speed to show the trends there.


Minor thing - speed is measured kilometres per second not kilometres :)

You may also want to add that the primary reason for this is that aircraft operational and structural limits are defined as a Mach number not an IAS number.

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