Case V 



TO PEOCEED FROM ONE RELATIVE POSITION TO ANOTHER, REMAINING WITHIN GIVEN RANGE OF THE 



GUIDE FOR A SPECIFIED TIME ENROUTE 



GIVEN: COURSE AND SPEED OF THE GUIDE, INITIAL AND FINAL RELATIVE POSITIONS OF THE 

 MANEUVERING UNIT, AND TIME TO REMAIN WITHIN A GIVEN RANGE OF THE GUIDE. 



TO DETERMINE: COURSE AND SPEED FOR MANEUVERING UNIT AND TRUE BEARINGS FROM GUIDE 

 WHEN ENTERING AND LEAVING REQUIRED RANGE. 



Example. — Guide on course 200°, speed 15.0 knots. Ship M, now 35° on the starboard quarter of the Guide and distant 

 8.0 miles, receives orders take station 8.0 miles dead ahead of the Guide, remaining within 6,000 yards of the Guide for 45 

 minutes for the purpose of signalling. 



Required. — (a) Course and speed for M. 



(b) Time to come within required range and true bearing of Guide at that range. 



(c) True bearing of Guide when passing beyond required range. 



(d) Time to arrive at new station. (See fig. 7.) 



Procedure. — Plot Guide at G and locate initial and final positions of M at M x and M 2 respectively. M u being 35° on the 

 starboard quarter of G, bears 145° relative or 345° true from G. Join M x . . . . M 2 . 



About G draw a circle with radius of 6,000 yards (3.0 miles), intersecting Mi . . . . M 2 at K and K>. Measure the 

 distance K . . . . K}. 



Lay out e . . . . g, the vector of G. Transfer slope Mi . . . . M 2 to g. Along this slope, from g, lay off the Relative 

 Speed which is equal to the Relative Distance K .... K} divided by the time that M is to remain within the specified range. 

 This is most readily done by utilizing the Logarithmic Scale, and thus m is located. Vector e .... m indicates the course 

 and speed for M to reach its new station while fulfilling the required conditions enroute. 



Distance Mi .... K, divided by Relative Speed g . . . . m gives the time of arrival at the given range. Mi .... M 2 

 divided by g . . . . m gives the time to arrive on final station. 



Directions K . . . . G and X 1 .... G are the true bearings of the Guide from M when M reaches and passes beyond 

 the given range respectively. 



Answer.— (a) Course 196°, speed 19.7 knots, (b) 73 minutes, bearing of Guide 129y 2 °. (c) 056°. (d) 190 minutes or 3 

 hours and 10 minutes. 



NOTE. — Had the slope Mi .... M 2 been outside the required range, the obvious action indicated would have been to close to 6,000 yards 

 in the most expeditious manner, take up the course and speed of the Guide for 45 minutes, and then proceed to the new station by another Maneu- 

 vering Board set-up. 



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