Your absolutely correct, Bill. I had
the 1/2 in the formula but failed to include it in the math
{:<(
So the dynamic pressure at sea level would
be around 0.25 psi rather 0.51 psi.
That in turn would require less true airspeed at
20,000 feet to generate only 0.25 psi dynmaic pressure for the same IAS
reading as at sea level which in turn would generate less mass flow since the
true airspeed require (163 mph) is quite a bit less than my erroneous figure
of 232 mph.
So, of course, that means the mass flow is about
27% less for the same indicated airspeed as it was at sea level or only 73% of
the sea level mass flow whichever way you want to look at it.
So using indicated airspeed would put you almost
30% off at 20,000 rather than the 3% I initially calculated. So IAS it turns
out does not provide that good an estimate of mass air flow and therefore
cooling at different altitudes. Air density still rules
{:>)
Appreciate you catching the error,
Bill
Ed Anderson