Kollsman window question

[gomntwins]

I was asked this by one of my students today: Why is it that you can set the kollsman window to a certain pressure, which moves the needles in the altimeter, but when you climb or descend, the pressure setting in the window does not change. In other words, how does the Kollsman window work? I honestly had no idea, so I thought I'd ask on here. Thanks!

 

[mtsu_av8er]

really, when you set the altimeter setting, you're just calibrating it to the current pressure setting. Think about a bathroom scale. Turn it upside down, and you can adjust the little knob until the dial indicates zero. If you calibrate the scale so that the dial indicates 20 lbs, then when you weigh yourself the dial will indicate your weight plus 20.

Same concept with the Altimeter!

 

[Propilot]

very good analogy.

good teaching!

 

[mtsu_av8er]

[ QUOTE ]
very good analogy.

good teaching!

[/ QUOTE ]

Thanks!

 

[GregCollins2]

Adjusting the Kolsman window setting changes the preload on the aneroid wafers and is not connected directly to the needles. As the aneroid wafers expand and contract with pressure the needles move with no effect on the Kolsman setting.