[Boatanchors] Re: Boatanchors Digest, Vol 17, Issue 20

[w4okw]

Message: 12
Date: Fri, 17 Jun 2005 02:05:16 -0400
From: "J. Forster" <jfor at quik.com>
Subject: Re: [Boatanchors] Radio transmitter ranges
To: Dan Arney <hankarn at pacbell.net>
Cc: boatanchors at mailman.qth.net, Grant Youngman <nq5t at comcast.net>
Message-ID: <42B2681B.11B8E468 at quik.com>
Content-Type: text/plain; charset=us-ascii

I would have thought you use those measurements to trim attitude and engine
settings, but use INS and/or GPS to figure out where you are and how fast 
you
are really going over the ground.

-John


Dan Arney wrote:

> We do that in 707's and 747's by air blowing into the Pitot tube and
> indicating in KPH until changeover at about 26 to 28,000 feet then to 
> Mach.
> Still comes speed over the surface of the earth.
> Hank
> KN6DI

-------------------Tom sez---------------------------

This has taken a bizarre twist!

Mach number is the ratio of the speed of the aircraft to the speed of sound 
in the gas ( air/atmosphere).

KPH (as in kilometers) might be seen on European aircraft.  Knots per hour 
would be a measure of acceleration and not normally seen in aircraft 
instrumentation.

Most large/modern aircraft airspeed indicators are calibrated in Knots.  The 
odd J-3 or Cessna will show MPH.  Some light aircraft show both - so take 
yer choice!

Quite correct, the INS, GPS or the good old whiz wheel will tell you how 
fast and where you are going!

The only time speed over the earth would be equal to the speed indicated by 
the pitot stat system is when IAS=TAS and there is no wind.  Very unusual 
conditions indeed.  I suppose a standard day at zero feet pressure altitude 
would do it if you could find a no wind situation.

Someone made a comment the other day after having his first ride in a 
"glass" cockpit ( an E-6 /B707 BTW) that pilots aren't pilots anymore, they 
are system managers!
Ya need to get up in a Cub to do real visual nav and "stick and rudder" 
flying. (-:

73 de Tom/W4OKW