Extra Kollsman Altimeter Poimters

I have an old Square D Kollsman 3 pointer altimeter that I think it's
about 50 or more years old and seems to be in working condition. The
body is about 2 13/16 diameter. The label on the back says part no.
371K-05

The three altitude pointers give the usual altitude readout. The little
Kollsman barometer window works and I know how to synchronize a known
altitude with the known barometer pressure by removing the little screw
and pulling the Kollsman knob out for the 'calibration'.

Now here's my question. There are two extra little visible pointers on
this altimeter that both rotate around concentric circles centered on
the instrument face. What are these pointers for. One is on the outer
circumference of the dial and the other one is on a smaller inner
circle with a radius of about 1 inch. Both pointers rotate when the
Kollsman knob is turned. They do NOT respond to air pressure changes.
The outer one moves at the same rate as the hundreds altimeter pointer
when the knob is turned. The inner pointer increments 100 feet when the
outer pointer makes one complete revolution around the face.

What are these "extra" pointers for???? They seem to serve no other
purpose than measuring the rotation of the Kollsman knob.

Dennis

wrote in message
oups.com...
I have an old Square D Kollsman 3 pointer altimeter that I think it's
about 50 or more years old and seems to be in working condition. The
body is about 2 13/16 diameter. The label on the back says part no.
371K-05

The three altitude pointers give the usual altitude readout. The little
Kollsman barometer window works and I know how to synchronize a known
altitude with the known barometer pressure by removing the little screw
and pulling the Kollsman knob out for the 'calibration'.

Now here's my question. There are two extra little visible pointers on
this altimeter that both rotate around concentric circles centered on
the instrument face. What are these pointers for. One is on the outer
circumference of the dial and the other one is on a smaller inner
circle with a radius of about 1 inch. Both pointers rotate when the
Kollsman knob is turned. They do NOT respond to air pressure changes.
The outer one moves at the same rate as the hundreds altimeter pointer
when the knob is turned. The inner pointer increments 100 feet when the
outer pointer makes one complete revolution around the face.

What are these "extra" pointers for???? They seem to serve no other
purpose than measuring the rotation of the Kollsman knob.

Dennis


Is it possible that they correspond to hundreds and thousands of feet of
*pressure*-altitude? Do they both go to zero and zero, when you set the
Kollsman to 29.92???

Is it possible that they correspond to hundreds and thousands of feet
of
*pressure*-altitude? Do they both go to zero and zero, when you set
the
Kollsman to 29.92???

No. When the Kollsman is set to 29.92, the little pointers indicate
1,740 feet. I almost think they may be for some sort of maintenance
purpose.

Then somebody got the little setscrew loose from the bottom of the Kollsman
knob and dicked the hands to read 1740. Or YOU are at 1740 density
altitude, one of the two.

When the Kollsman is set to 29.92 the hands should read your MSL altitude
corrected for nonstandard temperature and nonstandard pressure, or density
altitude (which is the same thing). You can readjust the altimeter by
calculating the density altitude at the altimeter's location, removing the
setscrew from the bottom of the Kollsman knob, pulling the knob out, and
making the altimeter read the density altitude with the window remaining at
29.92.

If you don't want to go through the hassle of doing all the calculations,
go into the FBO to the calibrated altimeter they use to give the altimeter
setting, set it to 29.92, put your altimeter on the same bench or table, and
adjust your altimeter to read exactly what the FBO's altimeter reads.

In either case, don't forget to replace the setscrew.

Don't ever make the mistake of telling somebody you reCALIBRATED your
altimeter because calibration requires an instrument shop to do the
calibration. You ADJUSTED it, which is quite legal to do.

Jim



wrote in message
oups.com...
Is it possible that they correspond to hundreds and thousands of feet
of
*pressure*-altitude? Do they both go to zero and zero, when you set
the
Kollsman to 29.92???

No. When the Kollsman is set to 29.92, the little pointers indicate
1,740 feet. I almost think they may be for some sort of maintenance
purpose.

"RST Engineering" wrote in message
...
Then somebody got the little setscrew loose from the bottom of the
Kollsman knob and dicked the hands to read 1740. Or YOU are at 1740
density altitude, one of the two.

When the Kollsman is set to 29.92 the hands should read your MSL altitude
corrected for nonstandard temperature and nonstandard pressure, or density
altitude (which is the same thing). You can readjust the altimeter by
calculating the density altitude at the altimeter's location, removing the
setscrew from the bottom of the Kollsman knob, pulling the knob out, and
making the altimeter read the density altitude with the window remaining
at 29.92.


Uh... excuse me?

Are you saying that the main "altitude" pointer that we all know and love is
what is indicating a *density* altitude?

Or are you saying that the *second* (unknown) set of pointers referenced by
the OP should be indicating a density altitude?

Either, if true, implies that this instrument has outdoor temperature
sensing???

wrote in message
oups.com...
I have an old Square D Kollsman 3 pointer altimeter that I think it's
about 50 or more years old and seems to be in working condition. The
body is about 2 13/16 diameter. The label on the back says part no.
371K-05

The three altitude pointers give the usual altitude readout. The little
Kollsman barometer window works and I know how to synchronize a known
altitude with the known barometer pressure by removing the little screw
and pulling the Kollsman knob out for the 'calibration'.

Now here's my question. There are two extra little visible pointers on
this altimeter that both rotate around concentric circles centered on
the instrument face. What are these pointers for. One is on the outer
circumference of the dial and the other one is on a smaller inner
circle with a radius of about 1 inch. Both pointers rotate when the
Kollsman knob is turned. They do NOT respond to air pressure changes.
The outer one moves at the same rate as the hundreds altimeter pointer
when the knob is turned. The inner pointer increments 100 feet when the
outer pointer makes one complete revolution around the face.

What are these "extra" pointers for???? They seem to serve no other
purpose than measuring the rotation of the Kollsman knob.

Dennis


Does this sound right?
http://ww2airfronts.org/Flight%20Sch..._deadreck.html

(then search the page for "reference markers")

Have you tried turning the Kollsman past its high limit (31.00??) or below
its lowest limit???

The implication of the article is that the reference markers are used to set
the altimeter setting when it is out of the range of the Kollsman window.
In other words, if you know your airport is 7,000 feet, and the pressure is
very high, say such that your altimeter setting would be 31.15.

You cannot set 31.15 in the Kollsman, but if you are sitting on the ground
at a known 7,000 feet, you can turn the reference markers to 7,000, and your
altimeter is now set correctly....

As I read the article, anyway....

Presumably, those markers would be a double check of the altimeter's
calibration. If on the ground, setting the markers to the station elevation
should give you the correct elevation of the station on both the read-out
and the reference markers. When in the air and obtaining an Altimeter
setting, setting the value should move the markers to the station's
elevation... a double-check that you did not mis-set a digit.

..... again, that's my understanding of the article....

Icebound,

I think you are getting close to the answer and thanks for the link to
a pretty good site. Indeed if I turn the Kollsman setting below 29.70,
a black shutter comes across the little window making any setting lower
than 29.70 impossible. If I turn it above 31.00, the Kollsman dial
markings go blank until they resume again at 28.10. But I'm still
confused.

I am at an actual known altitude of about 20 feet above sea level here
where the altimeter sits on my desk beside me. If I set the Kollsman
window to the current barometer setting, then the hands show nearly 20
feet as expected. The "reference pointers" indicate an altitude that
is dependent on the Kollsman window setting.

For example, today the barometer setting is 30.10, the hands say 20
feet and the reference pointers show about 1,580 feet. Now what
exactly is 1,580 feet telling me?

wrote in message
ups.com...
Icebound,

I think you are getting close to the answer and thanks for the link to
a pretty good site. Indeed if I turn the Kollsman setting below 29.70,
a black shutter comes across the little window making any setting lower
than 29.70 impossible. If I turn it above 31.00, the Kollsman dial
markings go blank until they resume again at 28.10. But I'm still
confused.

I am at an actual known altitude of about 20 feet above sea level here
where the altimeter sits on my desk beside me. If I set the Kollsman
window to the current barometer setting, then the hands show nearly 20
feet as expected. The "reference pointers" indicate an altitude that
is dependent on the Kollsman window setting.

For example, today the barometer setting is 30.10, the hands say 20
feet and the reference pointers show about 1,580 feet. Now what
exactly is 1,580 feet telling me?


Well, if we *are* correct, it could be something as simple as:

....you would think that the reference-indicators, too, would have some sort
of adjustment screw hidden away somewhere. Perhaps somebody before you
wondered about it and fiddled with them. If you can find it and "correct"
the indicators to 20 feet independently of the Kollsman knob.... that may be
the answer.

Well, I removed the innards and (independently) reset the reference
pointers to agree with the altitude hands at the correct Kollsman
setting. (I'm pretty handy at tinkering with delicate instruments.)

But I still don't really know what those little markers are for. If, as
you have suggested, they are used to set the altimeter to the correct
barometric pressure when the Kollsman window is blanked out, how does
one know where to set the markers? Let's say one is in an area where
the altitude-barometer combination there renders the Kollsman window
useless. If one is given the barometric pressure there, one would then
need a table or have to make a calculation to get the correct setting
for the reference markers. Does this sound correct?

Dennis

Dennis

Dennis,

Can you post a photo of this altimeter's dial to, say,
alt.binaries.pictures.aviation?

Jon