Altimeter Calibration Height

"Maxwell" wrote in message
...

Maybe I'm missing something here, but would it simplify to say:

That if you mount an altimeter at the 100' level of a 200' tower,
equiped it with a static tube 100' long,
that the altimeter will read the same regardless if end of the tube,
is stationed at the top or bottom of the tower.

?????


Why didn't I think of that?

"Neil Gould" wrote in message
et...

I think the issue is with your use of the term "indicates altitude", which
should be "senses pressure".


It's not an issue with me. Altimeters indicate altitude by sensing
pressure.



The altimeter "indicates" via the display
(dial or digital), and the display is adjustable both during
installation/calibration and by the pilot to adjust for atmospheric
pressure. Consider that when you tell a pilot that the "altimeter is
30.12", the pilot adjusts the _indicated altitude_ by setting the Kollsman
window to that _pressure setting_.


When you tell a pilot "altimeter 3012" the pilot simply adjusts the Kollsman
setting to 3012.



We don't watch the Kollsman (the only
"indication" of "altitude" consistent with the controller's information)
when trying to land. ;-)


Correct.

Recently, Steven P. McNicoll posted:

"Neil Gould" wrote in message
et...

I think the issue is with your use of the term "indicates altitude",
which should be "senses pressure".


It's not an issue with me. Altimeters indicate altitude by sensing
pressure.

Correct, however the "indication" (display) is not the *method* (sensing
pressure). So, your assertion: "In other words, an altimeter indicates
altitude at the level of the instrument itself." is only valid under a few
specific circumstances.

[...] Consider that when you tell a pilot that the "altimeter is
30.12", the pilot adjusts the _indicated altitude_ by setting the
Kollsman window to that _pressure setting_.


When you tell a pilot "altimeter 3012" the pilot simply adjusts the
Kollsman setting to 3012.

Do you see a difference between my statement and yours, other than the
decimal point?

Neil

"Jose" wrote in message
. ..
if you mount an altimeter at the 100' level of a 200' tower,
equiped it with a static tube 100' long,
that the altimeter will read the same regardless if end of the tube,
is stationed at the top or bottom of the tower.

That is a mostly true statement. Conditions inside the tube could differ
from ambient conditions, this would engender a teeny (but real) difference
in readings.

Jose

You mean like pressure loss of the long length or something?

"Neil Gould" wrote in message
t...

Correct, however the "indication" (display) is not the *method* (sensing
pressure).


Who said it was?



So, your assertion: "In other words, an altimeter indicates
altitude at the level of the instrument itself." is only valid under a few
specific circumstances.


What would those few specific circumstances be?



Do you see a difference between my statement and yours, other than the
decimal point?


Yes. You say the pilot adjusts the indicated altitude, I say he adjusts the
altimeter setting.

It's not an issue with me. Altimeters indicate altitude by sensing
pressure.

Yes, but there's a very important step in between, and that step is the
one that answers the original question.

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.

"Matt Whiting" wrote in message
...
Steven P. McNicoll wrote:
"Matt Whiting" wrote in message
...
Show me one that indicates in units of "altitude at the level of the
instrument."


http://www.auf.asn.au/groundschool/altimeter1.jpg

Try again. It is adjustable so I can make it read any altitude I like.

Is that a good way to avoid busting Class Bravo?

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

Recently, Steven P. McNicoll posted:

"Neil Gould" wrote in message
t...

Correct, however the "indication" (display) is not the *method*
(sensing pressure).


Who said it was?

You do when you imply that there is a necessary agreement between what the
altimeter senses and what it displays.

So, your assertion: "In other words, an altimeter indicates
altitude at the level of the instrument itself." is only valid under
a few specific circumstances.


What would those few specific circumstances be?

Jose listed them in response to an earlier post of yours.

Do you see a difference between my statement and yours, other than
the decimal point?


Yes. You say the pilot adjusts the indicated altitude, I say he
adjusts the altimeter setting.

You actually said, "When you tell a pilot "altimeter 3012" the pilot
simply adjusts the *Kollsman
setting* to 3012." (emphasis mine). As we described the same action, this
distinction is without a functional difference.

Neil

Jose wrote:
An altimeter senses pressure in order to indicate altitude.

Now we're getting somewhere. The pressure is sensed based on the laws
of physics. The altitude is indicated based on calibration and Kollsman
setting.

Right and the altitude indicated has little to do with the altitude of
the instrument.

Matt

Maxwell wrote:
"Jose" wrote in message
t...
An altimeter senses pressure in order to indicate altitude.
Now we're getting somewhere. The pressure is sensed based on the laws of
physics. The altitude is indicated based on calibration and Kollsman
setting.


Maybe I'm missing something here, but would it simplify to say:

That if you mount an altimeter at the 100' level of a 200' tower,
equiped it with a static tube 100' long,
that the altimeter will read the same regardless if end of the tube,
is stationed at the top or bottom of the tower.

Yes, that is correct. There might be a slight transient as you moved
the tube, but at steady state the location of the tube would not matter.

Matt