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Altimeters: Sensitive vs. Non-Sensitive

Posted By:
Glen Wilcox
Homebuilder or Craftsman
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#1 Posted: 5/5/2011 22:46:07

Can anyone explain the difference between these two altimeters? Thanks.



Peter Weiskopf
Warbirds of America MemberHomebuilder or Craftsman
22
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#2 Posted: 5/6/2011 08:05:26

A sensitive altimeter has a Kollsman window for displaying and a knob for setting local sea level reference pressure. Otherwise (1) as the aircraft flew into different conditions they would have inaccurate altitude. And (2) aircraft flying in the flight levels , above 18,000 feet, would not be able to set the 29.92 standard setting necessary for separation.

 

Pete



Jim Heffelfinger
Homebuilder or Craftsman
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#3 Posted: 5/7/2011 01:03:36 Modified: 5/7/2011 01:05:00

Based on this page from AS catalog I see both instruments having pressure adjusting features.

http://www.aircraftspruce.com/menus/in/altimeters_falcon.html

I believe the difference is the clockworks of the two - insensitive having a single pointer and the sensitive having 2 or three hands with the much more complex gearing.  

 

 



Darrell Whiteaker
Homebuilder or Craftsman
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#4 Posted: 5/10/2011 18:17:00

Hmm....now i'm confused. Anybody have the correct answer?

 

skeeter

 



Nick Myers
96
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11
#5 Posted: 5/11/2011 08:45:51

My C140 had an "insensitive" altimeter and my newer Davis has a sensitive altimeter.  The only difference I could find is with the "insensitive" altimeter, I could get close to the correct setting, but had to basically guess where the exact seting was.  For example, it might have a line at the 29.9 mark, but to get 29.92 you are basically guessing.

On my sensitive altimeter, there are lines for every 0.02, so I can pretty much hit a resolution of 0.01.

I do not know if this is officially the definition difference, but it is one thing I noticed (and makes a reasonable amount of sense).



Peter Weiskopf
Warbirds of America MemberHomebuilder or Craftsman
22
Posts
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#6 Posted: 5/11/2011 20:19:53 Modified: 5/11/2011 20:26:28

 

"A sensitive altimeter is one with an adjustable barometric scale

allowing the pilot to set the reference pressure from which the

altitude is measured. This scale is visible in a small window

called the Kollsman window. A knob on the instrument adjusts

the scale. The range of the scale is from 28.00" to 31.00"

inches of mercury (Hg), or 948 to 1,050 millibars."

 

 

 

From the FAA instrument training handbook  FAA-H-8083-15A  Chapt 3,