Example XXIV-B 



GIVEN: Fleet Guide is on course 340°, speed 16.0 knots, and at 0800 is 20.0 miles bearing 250° from chart point A. 

 At this time a destroyer leaves point A to scout a chart line in direction 000° to maximum distance so as to join the Guide at 

 1300, using a speed of 25.0 knots on the first leg and a speed of 20.0 knots on the second leg. 



Required. — (a) Destroyer's course on first and second legs, (b) Length of chart line scouted, (c) Time Destroyer 

 turns to second leg. (See Fig. 35.) 



Procedure. — Locate the chart point at any point, A, and the 0800 position of the Guide at G. 



Lay out the Guide's vector, e . . . . g, and the vector of the first leg for the Destroyer, e . . . . d x . Lay off from g 

 the vector g . . . . f, equal in length to the rate obtained by dividing the distance .A .... G by the 5.0 hours available, and 

 parallel to the slope A . . . . G. From c?i draw a Time Line through /.intersecting the 20.0 knot speed circle at d 2 . e . . . . d 2 

 is the vector for the second leg of the destroyer's run. 



From A, in direction parallel to g . . . . d u lay off a line A . . . . X, of extended length. From G, lay off a line parallel 

 to, but in opposite direction to, g . . . . d 2 , intersecting A . . . . XatP. A. . . . P and P . . . . G represent the Relative 

 Lines run by the destroyer on its first and second legs respectively. 



The time on first leg may be found either by dividing the Relative Distance A .... P by the Relative Speed g . . . . d u 

 or by proper use of the Time Diagram. Time to change to second leg is this time added to 0800. 



The chart distance run on course 000° is found by multiplying the speed of 25.0 knots by the time on the first leg. 



Answer. — (a) First course 000°; second course 272°. (b) 67.0 miles, (c) 1041. 



NOTE. — A Navigational Plot of this example is shown in half scale for illustrative purposes, but is not required for the solution. 

 A comparison of this example of surface vessels with the previous example using airplanes, will further emphasize the superiority of aircraft 

 for covering large areas in scouting exercises. 



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