Hurricane6,
It seems you're in the process of winding up your thread, a pity, I was enjoying it.
Before you wind it up, a word or two here which may shed light on your search for P/S, presumably P0 and Ps, as applicable to the Mach number calculation. P0 and Ps show up in all of the normal Mach number calculations, as highlighted below -
CAS to Mach Number (Given CAS and Ps for the Pressure Height)
M = SQR (5 * (( P0 / Ps * (1 + Vc^2 / a0^2 / 5)^3.5 - 1) + 1)^(2/7) - 1))
Mach Number to CAS (Given Mach No. and Ps for the Pressure Height)
Vc = a0 * SQR(5 * (( Ps / P0 * ((1 + M^2 / 5)^3.5 - 1) + 1)^(2/7) - 1))
CAS / Mach Changeover Height (Given CAS and Mach Number)
Ps / P0 = (((Vc / a0)^2 / 5 + 1)^3.5 - 1) / ((1 + M^2 / 5)^3.5 - 1)
Where -
a0 = ISA Sea Level Speed of Sound (661.4787442 Kt)
Vc = CAS in Knots
M = Mach Number
P0 = ISA Sea Level Pressure (1013.25 hPa)
Ps = Static Pressure at Flight Altitude (hPa)
So we see the Pressure Ratio (Ps/P0) in the second and third examples, and the inverse Pressure Ratio (P0/Ps) in the first
.
Liked the thread Hurri6, keep them coming.
Best Regards,
Old Smokey