Extra Kollsman Altimeter Poimters

wrote in message
oups.com...
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?



Having read and re-read that article several times....

My latest take is that the correct position for them is
zero zero, when the Kollsman window set at 29.92.

From the article, they would appear to do nothing more than show the
estimated "difference" (not the "pressure altitude" as I first surmised, but
just the "difference").... the estimated difference between the *pressure*
altitude of the airport in standard-atmosphere conditions, compared to the
pressure altitude of the airport in the actual conditions of today. By
setting them to show that *difference*, your altitude readout will now show
the field elevation when you are on that field.

Left of zero would be negative (pressure altitude is less than standard,
i.e. actual pressure is higher than standard. Right of zero would be
positive, air pressure is lower than standard. ) The article mentions to
take care when setting negatives.... 900 would actually mean minus 100....


The only use of these markers would be if the station reported altimeter
setting in terms of this "pressure altitude variation", as depicted in the
diagram in the article. ( This seems to be something from a bygone era).
You would set the appropriate difference on the markers ( in the
appropriate plus or minus direction) and your altimeter would now be
adjusted correctly.....

Since pretty much everybody today reports the Kollsman value directly in
"inches of mercury" (or Millibars in Europe), you do that directly with the
Kollsman value, so the markers don't matter... you don't really care about
the "difference" any more.


So the only use today, would be... after setting the Kollsman window, you
could check a table .... or make a mental estimate.... of what the
difference should be ( about 100 feet per .10 inches of mercury away from
29.92).... Also, of course, that it is on the correct side of zero (left
side (negative) if greater than 29.92, right side if less than 29.92)....
and see that the markers correspond, as a double check.



After moving the markers to zero zero at 29.92, then setting your correct
altimeter setting, I would expect:

If, like 29.82, the indicators should show about plus 100, 29.72: plus200,
etc.
If, like 30.02: minus 100, 30.12: minus 200 , etc.

To all:

Dennis emailed me the picture of his altimeter to post to my website
so that all can see it.

http://www.AirplaneZone.com/PubDir/Alt_002.jpg (135 KB)


David Odum - email: David at AirplaneZone dot com

Just from looking at the picture, I'd say the third needle is for 10,000
feet increments.

Look at how the labels line up when each pointer is in the 12:00 position...



"David Odum" MyFirstName@AirplaneZone wrote in message
...


To all:

Dennis emailed me the picture of his altimeter to post to my website
so that all can see it.

http://www.AirplaneZone.com/PubDir/Alt_002.jpg (135 KB)


David Odum - email: David at AirplaneZone dot com

Here's a modern Falcon Gauge unit with the same markings...

http://www.falcongauge.com/images/pr...sitiveALT1.jpg



"David Odum" MyFirstName@AirplaneZone wrote in message
...


To all:

Dennis emailed me the picture of his altimeter to post to my website
so that all can see it.

http://www.AirplaneZone.com/PubDir/Alt_002.jpg (135 KB)


David Odum - email: David at AirplaneZone dot com

"Lakeview Bill" wrote in message m...
Here's a modern Falcon Gauge unit with the same markings...

http://www.falcongauge.com/images/pr...sitiveALT1.jpg



"David Odum" MyFirstName@AirplaneZone wrote in message
...


To all:

Dennis emailed me the picture of his altimeter to post to my website
so that all can see it.

http://www.AirplaneZone.com/PubDir/Alt_002.jpg (135 KB)


David Odum - email: David at AirplaneZone dot com


You guys are missing the little black triangle just to the left of the 1000' label...does it move?

" Blueskies" wrote:


You guys are missing the little black triangle just to the left of the 1000' label...does it move?


Just to be clear, these are the pointers in question and, according to
Dennis, they both move when the Kollsman knob is rotated but do not
move with pressure changes. The other three pointers are the standard
"sensitive altimeter" pointers familiar to most pilots.

http://www.AirplaneZone.com/PubDir/Alt_003.jpg


David - email - David at AirplaneZone dot com

In article ,
MyFirstName@AirplaneZone says...

http://www.AirplaneZone.com/PubDir/Alt_003.jpg

And with the picture, it becomes somewhat clear that the pointers are
the indicating the same as the Kollsman window, but in dial form. The
white pointer is inches divided by 10 and the black pointer is the
tenths. An extra, quick to read, indicator of altimeter setting,
especially when out of range of the Kollsman window.

An experiment, put the Kollsman window on some arbitrary setting, and
see if the dials correlate to what's indicated in the window.

--Carlos V.

"David Odum" MyFirstName@AirplaneZone wrote in message ...
" Blueskies" wrote:


You guys are missing the little black triangle just to the left of the 1000' label...does it move?


Just to be clear, these are the pointers in question and, according to
Dennis, they both move when the Kollsman knob is rotated but do not
move with pressure changes. The other three pointers are the standard
"sensitive altimeter" pointers familiar to most pilots.

http://www.AirplaneZone.com/PubDir/Alt_003.jpg


David - email - David at AirplaneZone dot com



Ha! I didn't see the little white triangle.

The little black triangle look like an altitude bug. It looks like it
can be moved around to whatever position you choose. But then I haven't
read the whole thread to know if that's true.



You guys are missing the little black triangle just to the left of the 1000' label...does it move?

"Lakeview Bill" wrote in message
m...
Here's a modern Falcon Gauge unit with the same markings...

http://www.falcongauge.com/images/pr...sitiveALT1.jpg



Where are they? I cannot spot any markers in your pic other than the 3
indicated-altitude pointers.

The moving indicators that dennise9 is writing about, are the tiny triangles
at the 3, and just to the right of the nine.... reading minus-700 in the
pic, as per the article which I posted about earlier. Since (s)he has
moved them independently of the Kollsman Knob (partly in response to my
speculation, I must confess), they are probably slightly in error for the
altimeter setting shown ( 30.90 )... I would expect closer to -1000 (or the
outer pointers at 0 and the inner on the 9)

So I am recommending putting the Kollsman at 29.92, resetting the markers
independently to zero zero, and then we would see if they go to near -1000
(as I would expect), when the Kollsman is put back to 30.92.

Or, if (s)he has already reset the pointers to zero-zero at 29.92, then -700
might just be a more accurate reflection of the 1.00 inch change in
altimeter setting between 29.92 and 30.92, than is the usual rule-of-thumb:
100 feet per .1 inch in altimeter setting.