Altimeter pilot watch?

The other day I saw a watch advertised as a watch for pilots that
includes an altimeter. While I have seen these before for mountain
climbers this is the first I have seen targeted at pilots. My first
question in seeing it was "Where is the Kollsman window?" I tried to
find more data online but I can't seem to find one of these that can
adjust. I assume they are all set to 29.92 but I am trying to figure
out how useful this feature would be if it can't be adjusted for local
conditions.

"es330td" wrote in message
...
I am trying to figure
out how useful this feature would be if it can't be adjusted for local
conditions.

I have worn one for several years now, but the altimeter has only
limited usefulness. The first thing I noticed is that the altimeter does
not read continuously. Probably to save battery life, it only updates
occasionally. With several button pushes, you can "interrogate" it at will,
but that is not much help when you are busy in (say) a landing pattern.

The other problem, (as you have already guessed) is calibration. There is
no way to set mine according to atmospheric pressure. Instead, you
calibrate the reading to the "proper" altitude in exactly the same manner as
you set your watch to the proper time. This is OK for local flights because
I can just set if for field elevation before I take off, but not so useful
for X-country flying.

Vaughn

es330td wrote:
The other day I saw a watch advertised as a watch for pilots that
includes an altimeter. While I have seen these before for mountain
climbers this is the first I have seen targeted at pilots. My first
question in seeing it was "Where is the Kollsman window?" I tried to
find more data online but I can't seem to find one of these that can
adjust. I assume they are all set to 29.92 but I am trying to figure
out how useful this feature would be if it can't be adjusted for local
conditions.
Yeah. No Kollsman window -- no problem. I use mine religiously.
Mostly to keep an extra instrument to watch the cabin altitude on A320's
that I fly over the Atlantic. It's kinda neat -- watching the cabin
altitude on your wrist, and seeing it match to the highlighted altitude
on the LCD.

(Of course, this is all simulated. Not a real flight. But all them same).

T

"es330td" wrote in message
...
The other day I saw a watch advertised as a watch for pilots that
includes an altimeter. While I have seen these before for mountain
climbers this is the first I have seen targeted at pilots. My first
question in seeing it was "Where is the Kollsman window?" I tried to
find more data online but I can't seem to find one of these that can
adjust. I assume they are all set to 29.92 but I am trying to figure
out how useful this feature would be if it can't be adjusted for local
conditions.


Here is a GPS watch that has altimeter, speed and a lot more.

http://www.aim-sportline.com/mytach/index_eng.htm

On Mar 12, 10:15*am, "Darkwing" theducksmail"AT"yahoo.com wrote:
"es330td" wrote in message

...

The other day I saw a watch advertised as a watch for pilots that
includes an altimeter. *While I have seen these before for mountain
climbers this is the first I have seen targeted at pilots. *My first
question in seeing it was "Where is the Kollsman window?" *I tried to
find more data online but I can't seem to find one of these that can
adjust. *I assume they are all set to 29.92 but I am trying to figure
out how useful this feature would be if it can't be adjusted for local
conditions.

Here is a GPS watch that has altimeter, speed and a lot more.

http://www.aim-sportline.com/mytach/index_eng.htm

Pilots can't use this. GPS altitude (while theoretically correct) is
not the same as pressure altitude because pressure does not vary in a
linear fashion with altitude; if it did, flight levels above 29,920
feet would require liquid oxygen on board for the engines.

"es330td" wrote in message
...
On Mar 12, 10:15 am, "Darkwing" theducksmail"AT"yahoo.com wrote:
"es330td" wrote in message

...

The other day I saw a watch advertised as a watch for pilots that
includes an altimeter. While I have seen these before for mountain
climbers this is the first I have seen targeted at pilots. My first
question in seeing it was "Where is the Kollsman window?" I tried to
find more data online but I can't seem to find one of these that can
adjust. I assume they are all set to 29.92 but I am trying to figure
out how useful this feature would be if it can't be adjusted for local
conditions.

Here is a GPS watch that has altimeter, speed and a lot more.

http://www.aim-sportline.com/mytach/index_eng.htm

Pilots can't use this. GPS altitude (while theoretically correct) is
not the same as pressure altitude because pressure does not vary in a
linear fashion with altitude; if it did, flight levels above 29,920
feet would require liquid oxygen on board for the engines.


Looks to me that you have a new product to invent!

On Mar 12, 2:00*pm, es330td wrote:
On Mar 12, 10:15*am, "Darkwing" theducksmail"AT"yahoo.com wrote:



"es330td" wrote in message

...

The other day I saw a watch advertised as a watch for pilots that
includes an altimeter. *While I have seen these before for mountain
climbers this is the first I have seen targeted at pilots. *My first
question in seeing it was "Where is the Kollsman window?" *I tried to
find more data online but I can't seem to find one of these that can
adjust. *I assume they are all set to 29.92 but I am trying to figure
out how useful this feature would be if it can't be adjusted for local
conditions.

Here is a GPS watch that has altimeter, speed and a lot more.

http://www.aim-sportline.com/mytach/index_eng.htm

Pilots can't use this. *GPS altitude (while theoretically correct) is
not the same as pressure altitude because pressure does not vary in a
linear fashion with altitude; if it did, flight levels above 29,920
feet would require liquid oxygen on board for the engines.

You're correct that GPS altitude will differ from pressure-based
altitude, but it's not because of the non-linearity. That's taken
into account when the altimeter converts from pressure to the
equivalent altitude. The difference is that the pressure-based
altimeter assumes the standard atmosphere model (and above the
transition altitude also assumes a fixed sea-level pressure of 29.93
"Hg). If the actual atmospheric conditions differ from the standard
model then any pressure-based altimeter will differ from the actual
value. Of course the GPS measurement also suffers from its own error
sources and generally has greater random fluctuations - but it's not
affected so directly by atmospheric variation from the standard model.

But pressure-based altimeter watches are commonly available. I used
to have a pretty cheap ($30) Casio with this function and I could
calibrate it either based on a currently known altitude or by setting
the sea-level pressure (i.e. the Kollsman window 29.92 setting when
appropriate). It updated the reading every 6 seconds and worked well
but I never used it for aviation other than for curiousity.

I have a Suunto Vector altimeter watch, and though I usually just set
it to ground level before taking off, it also has a "sea level
pressure mode" which is equivalent to setting the Kollsman window.

Before that I had an Avocet altimeter watch; I don't really recall but
I think it had a similar setting.

If find it most useful for paragliding; I don't use it in the plane.

-Dana

On Wed, 11 Mar 2009 22:49:30 -0700 (PDT), es330td
wrote:

The other day I saw a watch advertised as a watch for pilots that
includes an altimeter. While I have seen these before for mountain
climbers this is the first I have seen targeted at pilots. My first
question in seeing it was "Where is the Kollsman window?" I tried to
find more data online but I can't seem to find one of these that can
adjust. I assume they are all set to 29.92 but I am trying to figure
out how useful this feature would be if it can't be adjusted for local
conditions.

--
In the 60's people took acid to make the world weird. Now the world is weird, people take prozac to make it normal.

On Mar 13, 4:43 am, Dana M. Hague wrote:
Before that I had an Avocet altimeter watch; I don't really recall but
I think it had a similar setting.

If find it most useful for paragliding; I don't use it in the plane.

And that's about how much I used any fancy watches I had. Most
of these watches are just expensive ways to impress non-pilots (and
they usually don't care) and they're so big and thick that they're
forever in the way or catching on something.
The one I wear now is a $30 Timex "turn and pull" analog watch
that lets me set the alarm real quick and easy. No tiny numbers or a
multitude of buttons and modes to get confused with when I want to set
the thing, or reset when I want to sleep for another half hour. And
it's not so ridiculously big.

Dan

What he said, Casio, years ago. I wore it flying and mountain hiking
several times, too. It was reasonably accurate to about 10,000', then
it started running lower than either the aircraft altimeter or the trail
elevation signs said. Its barometric setting was by setting it to a
known altitude.

David

Peter Rathmann wrote:
On Mar 12, 2:00 pm, es330td wrote:
But pressure-based altimeter watches are commonly available. I used
to have a pretty cheap ($30) Casio with this function and I could
calibrate it either based on a currently known altitude or by setting
the sea-level pressure (i.e. the Kollsman window 29.92 setting when
appropriate). It updated the reading every 6 seconds and worked well
but I never used it for aviation other than for curiousity.