Question on Altitude

D

Dreampilot

Well-Known Member
Hi, everyone

I was wondering if somebody could help me on this attitude problem.

I have to find the Pressure Attitude and Density Attitude for the following senario.

Alitimter Setting in plane 30.35
Current Altimeter Setting 30.58
Surface Elevation 1723
Temperature 15 C
Indicated Altitude 1723

If anyone knows the answer it would be great.
 
Dreampilot said:
Hi, everyone

I was wondering if somebody could help me on this attitude problem.

I have to find the Pressure Attitude and Density Attitude for the following senario.

Alitimter Setting in plane 30.35
Current Altimeter Setting 30.58
Surface Elevation 1723
Temperature 15 C
Indicated Altitude 1723

If anyone knows the answer it would be great.
Click to expand...

Is this homework?
 
Is the homework intended to determine if you can find the answer to that particular problem, or to determine if you can use the methods taught to determine the answer to any problem like it?


There's a saying that if you give a man a fish, he eats tonight, but if you teach him how to fish, he eats for a lifetime.



Tell us, what method did your teacher explain to answer questions like this? Is there a part of that process that you don't understand?




.
 
Yeah, I cant understand how to determine the Pressure altitude. I thought it was current alitmeter setting minus IAS (29.92) and density attitude i have no idea how to find.
 
Here's a hint to find pressure altitude:

Pressure altitude = the altitude the altimeter reads when set to 29.92
1 inch mercury = 1000 feet of altitude
In the Kohlsman (sp?) window of the altimeter..."increase inches, increase altitude"

Imagine what the altimeter would read in this scenario if you you reset it to 29.92

Hopefully that wasn't too cryptic. I'll let you figure out the rest of the homework on your own. ;)
 
Dreampilot said:
Yeah, I cant understand how to determine the Pressure altitude. I thought it was current alitmeter setting minus IAS (29.92) and density attitude i have no idea how to find.
Click to expand...

The Pressure Altitude is what is indicated in the altimeter if the correct value is set in the Kollsman Window, i.e., the "altimeter setting."


You have an indicated altitude of 1723 feet, but the altimeter setting is incorrect. While you have 30.35, the actual value should be 30.58.

Scratch that - - that's what I get for relying on old brain cells. For pressure altitude, you want the altitude that would be indicated were you to set 29.92 in the Kollsman window.


So, what would happen to the altitude pointer were you to turn the knob to change 30.35 to 29.92? Which way would it go, and how much?






.
 
Dreampilot said:
im gonna say it is 2300 ft
Click to expand...

I'm gonna say that you'd be incorrect.

The pressure altitude is going to be less than indicated altitude, not more, because the altimeter setting > 29.92 inches of mercury.

Try again!
 
Im sorry i was looking at the wrong surface elevation, the correct surface elevation is 4444 and it is 25 C outside with an indicated altitude of 7500. the altimeter parts are correct so the correct problem is...

Altimeter Setting in Plane 30.35
Current Setting 30.58
Surface Elevation 4444
Temp 25 C
Indicated Altitude 7500

Sorry Guys
 
Dreampilot said:
wouldnt it increase about 230ft
Click to expand...


If you rotate the Kollsman Window from 30.35 to 30.58, 230 feet would be correct.


For Pressure Altitude, though, the question is, what would happen if you went from 30.35 to 29.92?





Ooops - - you changed the problem on us...

:)
 
TonyC said:
Hmmmm...
Care to show your work?.
Click to expand...
Show all of it, and start at the very beginning with how you got the pressure altitude.

I'll be waiting and just watch this 2:30 hour stupid standoff. It's funny because you hear part of the conversation between the camermen in the chopper.
 
First of all, it doesn't matter what the kolsman window is showing at the moment, to get pressure altitude take the current altimeter setting and subtract 29.92 away from it. If the difference is a negative number, then using the 1"Hg/1000' rule, you take away that number from the field elevation. If the difference is a positive number, then you add the value to the altitude.

ex. :
Current alt. setting= 30.42
Standard alt. = 29.92
Field elevation = 1000'

30.42"
- 29.92"
--------
.50" x 1000 = 500'

Pressure altitude = Field elevation (1000') + Pressure difference value (500)
= 1500'

another ex. :
Current alt. setting = 29.42
Standard alt. = 29.92
Field elevation = 1000'

29.42"
- 29.92"
--------
-.50" x 1000 = -500

Pressure altitude = 500'

From there, you use the small window on the E6-B matching the Pressure altitude with the current temperature. Voila, you have Density altitude!

-ColM
 
ColMustard said:
First of all, it doesn't matter what the kolsman window is showing at the moment, to get pressure altitude take the current altimeter setting and subtract 29.92 away from it. If the difference is a negative number, then using the 1"Hg/1000' rule, you take away that number from the field elevation. If the difference is a positive number, then you add the value to the altitude.
Click to expand...

Well, you see, you have to make an assumption there, and the assumption is that you want the Pressure Altitude of the field. I thought we wanted the Pressure Altitude of the airplane. Either of us could be wrong or right, as it's not stipulated in the question.


Hmmmm....




:(




.
 
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