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Density altitude aviation

Posted on 2013-06-23
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Last Modified: 2013-06-29
I wanted to check my logic for the following question:

"You are contemplating a take-off at a high aerodrome(1460ft elevation) on a hot day(temperature 29 degrees Celsius). Approximately what is the current density altitude if the QNH is 1013mb?

The answer is 3500?

Density altitude= pressure altitude + (120x (OAT-ISA))

So taking isa at sea level as 15 degrees Celsius and -2 for every 1000 feet then isa at say 1500 feet 12degrees Celsius.

29-12= 17 x 120->2040

2040 + 1013= 3053

Am I just being to approximate with my answer or am I doing something wrong?

Thanks for the help.

Regards,

Ross
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Question by:ross13
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Expert Comment

by:ChloesDad
ID: 39269328
I think that your in the right ball park with your answer.

Using this calculator  http://wahiduddin.net/calc/calc_da_rh.htm I get 3400ft

You dont give a figure for dew point or RH, so I used 0% RH
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Flyster earned 500 total points
ID: 39276497
You made a slight error. You are using the pressure and not the altitude. The pressure ALTITUDE is 1460 feet, so the formula is 1460 + (120(29-12)) or 1460 + 2040 or 3500 feet.

Flyster
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Author Comment

by:ross13
ID: 39286720
Thanks for that. When I was thinking pressure altitude as you said I took the pressure of 1013 and not 1460.

Thanks for the help.

Cheers,

Ross
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Expert Comment

by:Flyster
ID: 39287003
You're welcome. Happy Flying :)
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