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....