In article ,
"Ash Wyllie" wrote:

Ari Silverstein opined

On Mon, 20 Sep 2010 06:10:02 -0700 (PDT), Mark wrote:

On Sep 19, 7:24*pm, "Ash Wyllie" wrote:

How high can you fly? 95,000ft?
This will soon be a real consideration.

I don't have the figures available at the moment, but I can tell you what
to look for and what to do.

Find the Vs for a C152.

Find the Mmo, likely about M.75.

Your max altitude is where the true Vs == Mmo.

* * * * * * * * * * * * *-ash
* * * * * * * * * * * * *Elect Cthulhu!
* * * * * * * * * * * * *Vote the greater evil.

Thank you so much! Can't wait to run the numbers.

Had this been a contest, you just walked off with a
new trophy.

---
Mark

How'd those numbers come out there, Mark(ie)? It's only been a week.

*ROFL*

Markie seems to be too busy to do his homework. Poor guy.

So I'll do it for him, and give him an F.

Formulae Units mks

TAS = exp(alt/15150) * CAS

Vsound = 340 * sqrt(1 - alt/86400)

Assume a Mmo of .6 and Vs of 25m/s (50kts) your coffin corner is about 28500m
(95000').

What the real figures for a C152, I don't know.


Ash,

I don't know where you got your formula, but MY "Elements of
Gasdynamics" book says that:

Vsound = sqrt(gamma*R*T),
where (for air):
gamma = 1.4 universal gas constant
R = 1715 ft-lb/slug-deg F
T = absolute temperature in Rankine

Nonetheless, the hypothetical C150 would encounter coffin corner before
it gets to 95Kft.