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Density Altitude definition...

 
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jncameron
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Joined: 29 Oct 2004
Posts: 89

PostPosted: Wed Jun 01, 2011 10:55 pm    Post subject: Density Altitude definition... Reply with quote

I'm trying to put together a decent simple definition for desnity altitude. There's lots
of definitions out there...some are reasonably easy to comprehend; others are
not so simple... I've yet to find one that I can easily understand...no doubt my own fault.
But if anyone has an idea,I'd be glad to hear from folks.
Thanks...

dagneil
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Pete
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Joined: 04 Jun 2004
Posts: 11851
Location: Mt Maunganui, New Zealand

PostPosted: Thu Jun 02, 2011 12:03 am    Post subject: Reply with quote

It's so simple ... really Laughing


Density altitude is the altitude in the International Standard Atmosphere at which the air density would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground. "Density Altitude" is the pressure altitude adjusted for non-standard temperature.

Both an increase in temperature and, to a much lesser degree, humidity will cause an increase in density altitude. Thus, in hot and humid conditions, the density altitude at a particular location may be significantly higher than the true altitude.


http://en.wikipedia.org/wiki/Density_altitude

http://wahiduddin.net/calc/density_altitude.htm
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Pete
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Pete
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Joined: 04 Jun 2004
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Location: Mt Maunganui, New Zealand

PostPosted: Thu Jun 02, 2011 12:19 am    Post subject: Reply with quote

Pressure and Density Altitude

http://www.langleyflyingschool.com/Pages/Flight%20Operations--Pressure%20and%20Density%20Altitude.html


The simple Rule of Thumb is ......

Firstly.

Calculation of pressure is done by calculating the difference between the current altimeter setting and the standard altimeter setting

For Pressure Alt ...... add or subtract 30 feet / Hp ( Hectapaskal ) for the difference between ISA 1013.

Greater pressure .... the P Alt is lower than standard.

Then for Density Alt ..... add or subtract 120' / *C for the difference between Actual Temp and that of ISA .

ISA temp at sealevel is 15*C

Higher temp means higher Density Alt.

Confused Confused
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