How can I calculate the ground speed in a specific height if I have only the mach number (and flight level)?

Question

... And of course no wind....

So, if I know that I wanna fly with mach .86 at FL390, how much would the ground speed be with no wind (I know that it must be something around 500 knots)....

Is there a diagram somewhere (online), or is there a formula for this?

Answer 1

http://givinganswers.simpler.at

you can get much information in this website, If you will check anyone blue link in website.

Answer 2

mach number =TAS / (38.94 x SAT^1/2)

so rearrange this to get your TAS which is the same as your GS if there is no wind. (SAT needs to be in Kelvins). good luck.

Answer 3

you can't. varies with temperature wind speed and direction which you did not  provide. but calculating gs from mach is a useless exercise at such altitudes. tables are available in the AFM that will give you true airspeed at specific flight levels, temps and mach numbers. then TAS can be used with wind to  figure ground speed. but 500 kts? eh, i'll go with your guess. TLAR.

what's TLAR you ask? it's the single most important skill a pilot can ever learn. a skill that cannot be taught but you better get it if you want to master the trade. That  Looks About Right.

Answer 4

I have no idea. Im not that smart.

Answer 5

Here are few links that answers in few different ways.

http://www.flightsimaviation.com/rule-of...

http://www.csgnetwork.com/e6bcalc.html

http://en.wikipedia.org/wiki/Airspeed

And finally , in this link for laymen like me http://virtualskies.arc.nasa.gov/weather...

with no wind as i understand , they should be same..!!

Answer 6

Its long but not so complicated.

Mach No is the ratio of True Airspeed(TAS) to the Local Speed of Sound(LSS)

Formula: Mach No=TAS/LSS

LSS varies with the square root of absolute temperature.

Formula: LSS=38.945 x Square root of (OAT+273)

And assuming ISA conditions then each FL has a temp.

FL390= -63*C

Put -63*C into LSS formula and you get LSS= 564.4kts

Mach .86 = TAS/564.4

Rearrange the formula and you get TAS= 485.4 kts

You said no wind, therefore.............GS= 485.4 kts

And by the way, wind has NO EFFECT on any of the above formulae! It would only affect groundspeed...