ATC Altimeter Settings

Well, I thought it was 0.5 inches, but I am not absolutley certain...it
was a while back. But, I do not think this changes my point
substantially. Even a 0.25 inch change is substantial, and if there is
not a standard of when one changes settings, it seems like a risk,
albeit small.

My experience is that ATC does not give me settings of nearby airports.
For example, I recall entering Chicgo Center airspace from the south.
I was just north of Lafayette, Indiana. The controller gave me the
altimeter setting for Chicago Midway. That is a long way away.
Lafayette airport was at least 0.1 inches different. I used ATC's
setting, because I figure they must have some standard reference point
in a region, or sub-region, so that all the planes are at least on the
same relative setting.

-Sami
N2057M, Piper Turbo Arrow III

A Lieberman wrote:

On 1 Apr 2005 13:56:42 -0500, Roy Smith wrote:


0.5 inches is a HUGE altimter setting change. Are you sure about
that?


I have to agree with Roy here.

I just finished coming back from Ohio to Mississippi, and I experienced a
very large altimeter setting adjustments in my journey southbound north of
Bowling Green KY, but I sure did not experience .50 inches adjustments en
route. I did end up .25 inch less over the whole trip though.

If I remember correctly on one ATC hand off, I went from 29.96 to 29.88
which lowered my altitude by 80 feet. This really alarmed me as I sure
don't like deviating more then 20 feet from assigned altitude. Needless to
say, I made a quick climb to my assigned altitude!

There was a rather steep pressure gradient even in my trip I just did this
week, but as Roy says, .5 inch altimeter change in a flight range distance
in planes I fly is probably indicative of weather I wouldn't / shouldn't be
flying in anyway.

Allen