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  1. #11
    Captain MadamBreakneck's Avatar
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    Feb 2009
    Essex UK
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    Quote Originally Posted by Randombloke View Post
    ... PV raised to power gamma equals nRT.
    but is it ideal?

    Quote Originally Posted by jetlag View Post
    If one has temperature inversion at the same time how would that effect the results...
    In responding to this, I now find that my numbers were arwry - it should be 4% per 10C, not as I recalled incorrectly in my previous post.

    So to calculate the altimeter error in your hot inversion you just need two temperatures: the actual outside air temperature where you are at the time and the ISA standard temperature for that altitude - the difference gives you the error (4% alt per 10C). So roughly in your example at 3000ft ISA temp is ~ 15C - 3x2C = 9C . Local OAT is, you say, 32C thus 23C above ISA; you would be 3000 x 4% x 23/10 = about .gets calculator out. 276-ish feet higher than your altimeter (set to QNH) shows you to be. Digging out my old whizz-wheel to check, I find it says true alt under those conditions is 3250ft, so the rule of thumb's not too bad.

    By similar working on my whizz-wheel, your true altitude at 2000ft indicated with 29C OAT would be about 2120ft physically.

    Last edited by MadamBreakneck; 27-07-19 at 14:44 PM. Reason: Spelling + added words to make a bit more sense

    Back to just bimbling in the TST.

    No longer instructing - just pontificating..
    and now a Tai Chi instructor

  2. The Following 2 Users Say Thank You to MadamBreakneck For This Useful Post:

    Gentreau (27-07-19), jetlag (27-07-19)

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