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Best way to explain Kollsman window?

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ceo_of_the_sofa

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Joined
Sep 25, 2002
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618
What's the best way to explain Kollsman (pressure) window to a student? I get the concept, but can't seem to be able to explain it, and others around the school have failed as well

Thanks
 
Hi...

How have you been trying to explain it?

Simply put, it's a small window on the dial face of an aircraft pressure altimeter in which the altimeter setting in inches of mercury is indicated.

Regards
 
ceo_of_the_sofa said:
What's the best way to explain Kollsman (pressure) window to a student? I get the concept, but can't seem to be able to explain it, and others around the school have failed as well

Thanks

Simple, compare it to a clock. Before you can accurately read a clock, you must first set the standard you want it to work from. For example, if I set my clock to PST it will tell me the answer I have told it to tell me. That answer may be wrong for the current situation because I live in EST. The pressure window is the same. It will give you the information that you tell it to give you.

If the problem is understanding the confusion of altitude in flight, (and your student has very good altitude control) try taking him up to an area w/o alot of traffic and move the dial around showing how the altimiter changes (while still at a constant altitude) by changing the Kollsman window.

Ali
 
Flymach2 said:
Hi...

How have you been trying to explain it?

Well, lets see...I tell 'em, We're setting up a baseline with this pressure, from which we go up (to lower pressure, hence the altitude change). So, in the perfect world, at 15C and 2992 Hg, we're at 0 feet, and by the time we get to 2892 Hg, it will (theoretically) read 1000 feet (1 inch per thousand feet)...Right? Well, theoretically :(...
Then we set the Kollsman up with, lets say, 3008 Hg(reported), and the field elevation still reads 20 feet, although it ought to read about -146 feet? Now, I know that we're at 20 feet MSL, and that it negates the -146 (from the datum plane), but how do I explain that so it flows better? Just looking for some old instructor's tricks or what not???

Arrrrgh :mad:
 
Back in 1929

Back in 1929, as an active duty US Armypilot, with a doctor's degree in Aero Engineering from MIT, Jimmy Dolittle (sp.?) flew the first blind approach to simulated 0/0 conditions. He had three important pieces of equipment to help him 1. a gyro attitude indicator designed by Sperry, 2. an electronic guidance system designed by Bendix, and 3. a pressure sensitive altimeter that could be adjusted for changes in the atmospheric pressure to always indicate field elevation when the airplane was on the ground, desinged by Mr. Kollsman
 
Hi...

Why would we set the current barometric pressure in the Kollsman window? Because we are adjusting the instrument for non-standard pressure.

If we were at a location where it was standard pressure, the instrument would indicate the appropriate field elevation. (Within 75 feet of field elevation for IFR flight.)

For example if we are at a field with an elevation 1000 ft. MSL and it was a standard pressure day, the Kollsman would be at 29.92 and the altimeter would indicate 1000 ft.

On a non-standard day at that same 1000 ft. MSL field, let's assume the current pressure is 30.15 and we mistakenly have 29.92 set in the Kollsman window. The altimeter would indicate approximately 230 ft. lower than the field elevation.

If we then set the Kollsman to 30.15, the altimeter would indicate the proper field elevation.


Regards
 
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