Altimeter Calibration Height

Tangential question for Steven:

I think you work in a control tower. If you work in a center in a
building at ground level, pretend you work in a tower.

You have a barometer there that tells you the sea-level pressure at
the airport. (That is, what a pressure gauge would read if you dug a
hole down to sea level and read the pressure down there.) That's the
pressure you announce on ATIS.

When the barometer was calibrated, did the calibration take into
account the height of the control tower?

Don

"Don Tuite" wrote in message
...

Tangential question for Steven:

I think you work in a control tower. If you work in a center in a
building at ground level, pretend you work in a tower.


I presently work in a tower, I used to work in a center.



You have a barometer there that tells you the sea-level pressure at
the airport. (That is, what a pressure gauge would read if you dug a
hole down to sea level and read the pressure down there.) That's the
pressure you announce on ATIS.

When the barometer was calibrated, did the calibration take into
account the height of the control tower?


We don't have a barometer in the tower. We have an ASOS on the field,
that's the source of the altimeter setting we put on the ATIS.

Don Tuite wrote:



You have a barometer there that tells you the sea-level pressure at
the airport.

Yes, every tower has one.


(That is, what a pressure gauge would read if you dug a
hole down to sea level and read the pressure down there.) That's the
pressure you announce on ATIS.

Some facilities use their ASOS some use their instrument in the tower.

I'd have to do it in a vacuum to eliminate the drag force.

Huh? Drag force isn't logical. It is an empirical observation.

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

"Jose" wrote in message
. net...

Huh? Drag force isn't logical.

It is to me.

"Jose" wrote in message
. ..

No, it is merely consistant with your experience. That is empirical, not
theoretical. Drag force can be derived in theory, but that requires
knowledge of atoms and molecules, which themselves are not logical. The
universe could be made up of wiggly strings, for all we know. That it is
made up of atoms is another =experimental= result.

That they are governed by quantum mechanics is yet =another= experimental
result, which is most =definately= not logical.


Nope, it's logical to me.

... quantum mechanics [...] is most =definately= not logical.
Nope, it's logical to me.

That explains a lot.

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

"Jose" wrote in message
et...

That explains a lot.


Glad I could help!

Steven P. McNicoll wrote:
"Jose" wrote in message
t...
Poor logic. An altimeter indicates whatever it is set to indicate. It
senses pressure, and moves hands on a dial. Take the case where you are
in a one hundred foot tall aircraft with the altimeter right at the top of
the cockpit with you, a hundred feet in the air. (We'll neglect the tail
for now).

If you don't get an altimeter setting, you will (likely) set the altimeter
so that the hands indicate the airport elevation as indicated on your
charts, even though you and the instrument are a hundred feet higher.

If you do get an altimeter setting, you'll set it for that. Then the
question becomes (since the altimeter doesn't know that it's in a tall
airplane) whether, at calibration in the shop, it was set to indicate
actual instrument altitude or to indicate something else (like instrument
altitude minus a hundred feet). I bet there are standards for that. I
don't know what they are, but they may well incorporate the hundred feet
deviation, since it is the =installation= that is certified.

Also, even if the static port and the instrument themselves are separated
in altitude, it would be the instrument altitude's pressure that is
sensed, since the "column of air" is connected, and ends at the
instrument.


In other words, an altimeter indicates altitude at the level of the
instrument itself.

No, it indicates a pressure differential at the level of the instrument.

Matt

Steven P. McNicoll wrote:
"Stefan" wrote in message
...
Message-ID: . net:
An altimeter indicates altitude at the level of the instrument itself.

Message-ID: nk.net:
In other words, an altimeter indicates altitude at the level of the
instrument itself.


Did you write this or was I just hearing voices?


Yes, I wrote that. What is your point?



I think his point is that if you turn the knob and change the setting in
the Kollsman window, you can indicate any altitude you want. Since the
altitude of the instrument hasn't changed, but the altitude indicated by
the instrument has changed; it isn't possible then that the altimeter is
indicating the altitude at the level of the instrument. Is it
indicating whatever altitude you tell it to indicate.

Matt