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    Flight 19 route
    From: Paul Hirose
    Date: 2009 Sep 17, 21:52 -0700

    This is about the "Bermuda Triangle" incident in December 1945, when
    five U.S. Navy torpedo bombers took off from Florida on a training
    mission and disappeared. I don't have any new insight on what happened,
    just some comments on the intended route.
    
    The Wikipedia article
    (http://en.wikipedia.org/wiki/Flight_19#Authorized_overwater_navigation_training_flight) 
    
    
    says, "With a trainee pilot in the role of leader out front, the
    exercise was called 'Naval Air Station, Fort Lauderdale, Florida,
    navigation problem No. 1,'[1] and it involved the Avengers negotiating a
    triangular course from and returning to Fort Lauderdale. After take off
    they would fly almost due east for 56 miles (90 km) until reaching Hens
    and Chickens Shoals where bombing practice was planned. The flight was
    then supposed to continue east another 67 miles (108 km) before turning
    onto a course of 346 for 73 miles (117 km), in the process over-flying
    Grand Bahama Island. Finally, Flight 19's last turn was a course of 241
    degrees for 120 miles (193 km), bringing it back to NAS Ft. Lauderdale.[2]"
    
    Footnote [1] is a Web page which appears to be an excerpt from the Navy
    investigation report. The pertinent part says,
    
    "2. That the organized overwater navigation training flight assigned to
    Flight 19 on 5 December 1945 was Naval Air Station, Fort Lauderdale,
    Florida, navigation problem No. 1 is as follows; (1) depart 26 degrees
    03 minutes north and 80 degrees 07 minutes west and fly 091 degrees (T)
    distance 56 miles to Hen and Chickens Shoals to conduct low level
    bombing, after bombing continue on course 091 degrees (T) for 67 miles,
    (2) fly course 346 degrees (T) distance 73 miles and (3) fly course 241
    degrees (T) distance 120 miles, then returning to U.S. Naval Air
    Station, Fort Lauderdale, Florida."
    
    It's a safe bet that a Navy report would use nautical miles. Therefore,
    the Wikipedia article should say "nautical miles", not simply "miles",
    and use the correct conversion to kilometers. Also, the courses should
    be clearly identified as true courses, as in the Navy document.
    
    Another problem is not so obvious: the triangular route doesn't close on
    itself. I discovered that when "flying" it in Microsoft Flight
    Simulator. Despite using the autopilot to hold headings, and even
    turning early by a calculated amount at each course change to allow for
    the finite turn radius of the plane, I finished about 10 miles from the
    departure point.
    
    N26°12.7' W080°08.8'  sim result, first flight
    N26°11.8' W080°10.2'  sim result, second flight
    
    In these flights I simply combined the first two legs into one. I.e., 
    the combined leg was 123 NM nonstop on TC 091, no bombing practice in 
    the middle.
    
    My first theory for the failure to connect to the departure point was 
    inaccuracy in the sim, so I computed the end point of the route two 
    different ways:
    
    N26°13.6' W080°07.4'  Mercator sailing
    N26°13.6' W080°07.4'  Lambert grid
    
    These computations confirm the flight simulator result. Flying the
    correct courses and distances puts you 10.6 miles away at a bearing of
    358° from the departure point.
    
    I believe that was intentional, to show the students a classic dead
    reckoning landfall technique. By aiming definitely north of the
    destination they could simply turn south at landfall, follow the coast,
    and be sure of getting home. There is no doubt the route worked, since 
    many students successfully flew it, including another flight the same day.
    
    The navigation exercise waypoints:
    
    N26°03.0' W080°07.0'  departure point
    N26°02.0' W079°04.8'  Hen and Chickens Shoals
    N26°00.8' W077°50.4'  turn to 346° true
    N27°11.9' W078°10.1   turn to 241° true
    N26°13.6' W080°07.4'  end
    
    Except for the first (which comes from the Navy report), I calculated
    those points on both a Mercator grid and a Lambert conformal conic grid,
    the latter with standard parallels N25°20' and N30°40'. At every point
    the results agreed within .001°.
    
    The coordinates for the end of the first leg (Hen and Chickens Shoals) 
    are within a mile northeast of Great Isaac Island, with its big lighthouse
    (http://www.biminisands.com/bahamas/island/great-isaac-lighthouse.htm).
    And four miles southwest of the island is the concrete ship SS Sapona,
    wrecked in a 1926 hurricane
    (http://www.concreteships.org/ships/ww1/sapona/). I suspect Flight 19
    "attacked" the hulk, used Great Isaac Island as their departure point
    for the 67 NM leg on true course 091, then became disoriented after the
    turn to TC 346.
    
    If they had started the second nav leg from SS Sapona instead of the 
    island, that would have offset the rest of the flight a few miles to the 
    south, and put the end point closer to the airfield. This may very well 
    have been the intent of the exercise.
    
    However, my calculation assumes the second leg began where the first leg 
    ended.
    
    All that is a lot to say about a trivial anomaly in an old Navy 
    navigation exercise, but as far as I've seen nobody has ever pointed out 
    that the route (depending on how you interpret the directions) can fail 
    to close on itself by 1 part in 30. And since I did all this work, it 
    may as well be preserved on the Web.
    
    Before I say anything on the Wikipedia Flight 19 talk page, I'll see if
    anyone here has any comments.
    
    -- 
    I filter out messages with attachments or HTML.
    
    
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