Mach V formula

[poorwanderingwun]

OK...I'm listing this here because you guys are more likely to have the info at your fingertips...or have sat the exams recently enough to remember the formula...

When I did my exams 20 years ago ( UK ) we had to know the formula to calculate Mach speed... my brain has suffered over the years ( Beer ) and although I thought that I still remembered it apparantly I've got it wrong....

My obviously mistaken formula was: TAS/LSS.... LSS calculated by: 38.94 x square root of K ( K I thought was -472 or something close....

Anyone out there that can help ?

[jtr]

O deg K = -273 deg C

Formula is correct

ISA S.L

Temp = 288 Deg K

thus LSS = 661 kts

[stuharri2002]

Mach No = V/a
Where:
V is speed in m/s and a is the speed of sound.
a = SQRT(Gamma x R x T)
where:
Gamma = ratio of specific heats (normally 1.4 for dry air)
R = Gas constant (normally 287.0519)
T = temperature (in kelvin)

hope this helps

stu

[poorwanderingwun]

Well done guys....Good luck...and watch out for the beer... :(

[bafanguy]

poor,

What does a pilot do with that formula once he has it ?

[jamestkirk]

Bafanguy

Talk about it to people in bars etc. that you want to get rid off. And relate it to a mach no. of your car on the local A road"

Works every time.

Along with " It's really difficult to find work after getting out of prison".

Hope this helps.

JTK

[bafanguy]

jamest,

...lol...I had my suspicions along those lines...