Solved

Another density altitude question

Posted on 2013-06-29
4
446 Views
Last Modified: 2013-06-29
I asked a similar question to this on experts exchange. I am trying out a few more just to make sure I am doing the calculation correctly. I am close to the answer but not getting the exact answer:

"You are planning your departure from your regular aerodrome at 1032ft elevation. The temperature is quite high at 30 degrees Celsius. The QNH is 1014mb. What is the approximate density altitude"


1. I need to calculate the pressure altitude.
PA= airfield elevation +(30x(1013-1014))
PA=1032 + (30x-1)
=>1002

2. Calculation of density altitude
DA=PA + (120xISA deviation)

When calculating ISA deviation, should I use the calculated pressure altitude or the aerodrome altitude(I think it should be the pressure altitude, just wanted to check).

15 degrees at sea level and -2 for every 1000 feet so isa temperature should be 13 degrees but in fact it's 30 degrees giving a difference of 17 degrees.

DA = 1002 + (120x17)
1002 + 2040
=>3042

I wanted to check that my calculation is correct as the book is 3000 feet giving a difference of 42 feet?

Cheers,

Ross
0
Comment
Question by:ross13
  • 3
4 Comments
 
LVL 24

Expert Comment

by:aadih
ID: 39286764
Use the formula:

DA=1.24 PA + 118.8 OAT - 1782

where DA=density altitude and PA=pressure altitude where PA=Hgt+30(1013-QNH)

Reference:

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

You do the calculation. ;-)
0
 
LVL 24

Accepted Solution

by:
aadih earned 500 total points
ID: 39286818
Got it yet?

The differences in answers are because of approximations (used in the formulas).

Your answer (3042), my answer (3024), and the book answer (3000) are all correct. :-)

The ~1.5% difference is within the acceptable margin for approximation errors.
0
 

Author Closing Comment

by:ross13
ID: 39286840
I downloaded an app onto my ipad and got a slightly different answer as well:-)

Thanks for the help.

Cheers
0
 
LVL 24

Expert Comment

by:aadih
ID: 39286845
Great.  A good (re)learning experience for me also.  So the pleasure is all mine, i.e., ours.  :-)
0

Featured Post

DevOps Toolchain Recommendations

Read this Gartner Research Note and discover how your IT organization can automate and optimize DevOps processes using a toolchain architecture.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
[week] - duration other than 7 days? 8 65
Decrease number proportionately 20 91
Proportion 4 48
Cumulative Distribution 2 37
This article provides a brief introduction to tissue engineering, the process by which organs can be grown artificially. It covers the problems with organ transplants, the tissue engineering process, and the current successes and problems of the tec…
When we purchase storage, we typically are advertised storage of 500GB, 1TB, 2TB and so on. However, when you actually install it into your computer, your 500GB HDD will actually show up as 465GB. Why? It has to do with the way people and computers…
Although Jacob Bernoulli (1654-1705) has been credited as the creator of "Binomial Distribution Table", Gottfried Leibniz (1646-1716) did his dissertation on the subject in 1666; Leibniz you may recall is the co-inventor of "Calculus" and beat Isaac…
Finds all prime numbers in a range requested and places them in a public primes() array. I've demostrated a template size of 30 (2 * 3 * 5) but larger templates can be built such 210  (2 * 3 * 5 * 7) or 2310  (2 * 3 * 5 * 7 * 11). The larger templa…

822 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question