[Info-vax] OT: Aircraft pitot tubes and clustering.

[John Reagan]

"JF Mezei" <jfmezei.spamnot at vaxination.ca> wrote in message 
news:00e4e770$0$6712$c3e8da3 at news.astraweb.com...

>
> Which is why there should be sources of speed which are independent from
> air pressure. The problem is that other sources of speed (GPS which
> gives ground speed, and inertial systems which calculate speed based on
> acceleration) do not give "air speed".
>
> Air speed is critical to determine if you are flying of falling out of
> the sky.
>

And it just isn't air speed.  It is air density as well.  Lighter air gives 
less lift.  So altitude helps determine density but different air masses 
have different densities at the same altitude.  It all factors into the 
pressure readings from the pitot tubes.

John