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    Flight 19 route: wrong course
    From: Paul Hirose
    Date: 2009 Nov 25, 14:56 -0800

    Flight 19 (of "Bermuda Triangle" fame) was supposed to fly true course
    091 to begin their navigation exercise, according to many Web sites. In
    fact, I've never seen anything to the contrary.
    However, there's some evidence that the true courses widely quoted on
    the Web are wrong. See the image of a chart (said to be from the
    official report) on this Web page:
    Obviously, the first two legs cannot be true course 091. The angle of
    the blue line with respect to the nearby parallel of latitude is much
    greater than one degree.
    By opening that image in an application such as Windows Paint it's
    possible to read pixel coordinates of any point in the image. Then with
    plane trigonometry you can determine the orientation of the course
    lines and meridians. With respect to "image north", I calculate that the
    meridians are oriented to 357�, and the three sides of the route are
    94�, 345�, and 238�. Therefore, with respect to the meridians, the true
    courses are 097, 348, and 241. Compare those figures to the conventional
    values widely given on the Web: 091, 346, and 241.
    In an earlier posting I noted that the conventional courses and
    distances, when plotted, fail to close on the start point. The
    discrepancy is 10.6 NM, or 3.4% of the total distance. But if the
    courses I measured on the picture are used instead, this is reduced to
    2.2 NM, or .7% of the distance. That's excellent when you consider that
    all courses and distances were rounded to 1 degree and 1 mile. (The plot
    was actually done mathematically on a Mercator grid to simulate an
    aircraft flying rhumb lines.)
    The Web page with the chart has something else which tends to confirm my
    theory. It says the planned route went to Great Stirrup Cay. Well,
    with course 091 you'd miss the cay by 32 NM. But course 097 takes you
    within a mile at closest approach, and at my calculated turn point
    you're just 3 miles away.
    Flying my courses (but using the conventional distances), the endpoints
    of the legs are:
    N26�03.0' W080�07.0'  start; depart on TC 097
    N25�56.2' W079�05.3'  Hen and Chickens Shoals; depart on TC 097
    N25�48.0' W077�51.5'  turn to TC 348
    N26�59.6' W078�08.4   turn to TC 241
    N26�01.2' W080�09.2'  end
    The point I labeled "Hen and Chickens Shoals" is 4 NM from the wreck of
    the concrete ship Sapona, which was probably a target for Flight 19's
    bombing practice. (This route goes right through the present day airway
    intersection BAHMA, depicted on the Miami Sectional Aeronautical Chart.)
    All these computations are based on one small image on a Web site, so
    I'm not going to claim there's something wrong with the widely quoted
    courses. It's hard to believe that such a discrepancy could have escaped
    detection. But it's interesting that when the new courses are plotted,
    the former misclosure in the route practically disappears.
    Finally, none of this gets us any closer to the reason for Flight 19's
    disappearance. It's strictly about two possible garbles in the
    description of the navigation problem, as it has been passed down to us.
    I filter out messages with attachments or HTML.
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