[Milsurplus] [ARC5] OT: What is the purpose of the 4th pointer on my Kollsman 671CLU-4-038 pressure altimeter?

[Clare Owens]

It was Ebay #201615219209? and in the picture for the listing the edge
pointer is at about 4.3 and the In. Hg is set to 30.55.  I did a
recalibration last night and noticed that although the three altitude
pointers stayed stationary, the edge pointer moved along with the inches of
mercury dial, so now it's at 8.4, with the In, Hg set to 30.10.  It moves
along with the In. Hg dial but the numeric relationship escapes me...

Thanks to all of you for the replies,

Clare

On Tue, Jul 12, 2016 at 2:06 AM, Sheldon Daitch <SDAITCH at bbg.gov> wrote:

> Looking at eBay item 351778486635, it makes sense, now.
>
> The  orange triangle is a reference altitude marker and is set with the
> lower right know.
>
> This unit is a high end altimeter system, and as noted, from a B737/747
> system.  Looks like it is from the older systems, steam gauges as some
> pilots call them.
>
> I've never flown an aircraft with that high end equipment, not on my
> budget, and I have to make some guesses.  I don't think the orange triangle
> marker is settable other than somewhere in the 1000 foot range, and usually
> set per one B-737 ops manual for the minimum descent altitude on an
> instrument approach.  I also suspect that altimeter pictured also has an
> output to an alerter in the  cockpit to tell the pilots they are at MDA.
>
>
>
> 73
> Sheldon
>
>
>
> ------------------------------
> *From:* ARC5 <arc5-bounces at mailman.qth.net> on behalf of Clare Owens <
> clare.owens at gmail.com>
> *Sent:* Tuesday, July 12, 2016 1:18 AM
> *To:* Discussion of AN/ARC-5 military radio equipment.;
> armyradios at yahoogroups.com; Milsurplus
> *Subject:* [ARC5] OT: What is the purpose of the 4th pointer on my
> Kollsman 671CLU-4-038 pressure altimeter?
>
> Hi All,
>
> The altimeter has the usual three pointers in its center, for
> 100/1000/10000 feet.  But it also has a little triangular pointer that
> rotates around the edge of the dial and moves at about the same speed as
> the 100 foot pointer.  When the three normal pointers are at zero, the one
> on the edge ia pointing to just a little below 6.8.  Seems odd and I can't
> find any reference to the edge pointer on line.
>
> It looks like this unit needs to be recalibrated and I've found
> instructions for that.
>
> The altimeter has the typical Navy "US with anchor" stamp on its back.
>
> Any Navy aviators out there?
>
> Thanks,
>
> Clare
>
>
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