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    Re: Contrail and Aircraft distance
    From: Antoine Couëtte
    Date: 2021 Oct 13, 07:40 -0700

    Dear Lars,

     

    Thank you for your reply.

    Obviously we get the same results.

    With "R" being the Earth Radius, "a" the Observer's altitude, "αthe A/C elevation above the true horizon, then the slant range "s" from A/C is given by the full formula as:

    s / (R+a)  = -sinα + sqrt {  sin²α + [ (h-a)/(R+a)] * [2+[(h-a)/(R+a)] ]  }  (see one of the enclosures)

    Hence with R = 6,378,137 m, a = 0 m : For α = 0.78° get s = 176.4 NM and α = 0.78° - (19/60)° = 0.466666...° get s = 192.2 NM.

    Frank, you mentioned this site. If using their exact R value, i.e. 6,371,009 m, then I am deriving exactly the same values as they are publishing for all and any configuration.

    And finally, for all, from a second enclosure, you will see how I accurately measured my "local horizon". T'was fun in that windy day.

    Antoine M. "Kermit" Couëtte

    antoine.m.couette[at]club-internet.fr

    File:
    211010b-Aircraft-Distance-vs.-Height-Elevation-.pdf
    File:
    211011-Measuring-the-height-of-the-apparent-local-horizon-.pdf
       
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