Lesson 14 Precise Piloting

NS100Fundamentals ofNaval Science

Precise Piloting

Objectives:1. Describe shiphandling characteristics.

2. Demonstrate how to calculate advance, transfer, and turn bearings.

3. Determine position in relation to track

4. Demonstrate how to calculate danger bearings.

Handling Characteristics Turning Circle - The path followed by the pivot point of a ship during a 360 degree (or more) turn using a constant rudder and speed.

- The pivot point for most warships is about 1/3 the way aft from the bow when the ship is going ahead. It is important to note that the bow turns inside the path of the turning circle, and the stern swings outside the turning circle.

60

C

DE

U

F

G

AT

HB

P

Typical Ship’s Turning Circle

Handling Characteristics

Advance - The distance gained in the original direction the ship was traveling from the point that the rudder was put over to the point where the ship is steady on the new course.

- The maximum advance will be for a 90 degree turn.

Final Course

End ofTurn

Start ofTurn

Ori

gin

al C

ou

rse

Ad

van

ce

Measured from the point the rudder was put over to the point where the ship is steady on its course

Handling Characteristics

Transfer - The distance gained, perpendicular to the original course from the point where the rudder was thrown over, to the point where the ship is steady on the new course.

Final CourseTransfer

End ofTurn

Start ofTurn

Ori

gin

al C

ou

rse Distance measured

perpendicular to the original course

Handling Characteristics Tactical Diameter - The transfer of a vessel during a 180 degree turn.

Final Diameter - The diameter of the approximate circular path that a ship describes if the rudder is kept over indefinitely.

E

B

A

F

D

Tactical Diameter

C

Tactical Diameter

Final

Diameter

OriginalCourse000

Wheel Over

Handling Characteristics Standard Tactical Diameter - A specified tactical diameter is laid down in tactical publications for naval ship types (i.e., frigates, destroyers, cruisers, and aircraft carriers).

- This data is used when ships are maneuvering in company to ensure all ships turn at the same rate, and the correct spacing between ships is maintained.

Handling Characteristics

Standard Rudder - The amount of rudder required to ensure a warship achieves the ordered standard tactical diameter.

- This rudder amount will vary between warship classes.

E

B

A

F

D

Tactical Diameter

C

Tactical Diameter

Final

Diameter

OriginalCourse000

Wheel Over

Handling Characteristics

Turn Bearings - In order to plot the position at which the ship must put the rudder over (to turn onto a planned track), the figures for advance and transfer must be calculated using interpolation, unless the specific speed and rudder combination is defined in the tables.

50

A

TR TR

- 0

00

T

TR -

050

T

N

ADVANCE AND TRANSFER TABLE

SPEED RUDDER ADVANCE/TRANSFERANGLE 45deg turn 90deg turn

YDS YDS

6KTS STD. 117/55 135/85FULL 67/40 55/55

10KTS STD. 80/45 125/80FULL 45/30 75/50

13KTS STD. 125/85 150/100FULL 100/75 80/55

Handling Characteristics

Turn Bearings - Should interpolation be necessary, the figure for transfer is used first to find the point where the ship will be steady on the new track.

- The figure for advance is then used to determine where the rudder must be put over in order to intercept the new track.

TR

- 0

00

T

TR -

050

T

100 0 100 200 300TR

Scale in Yards

N

Advance and Transfer TableAngle of Turn Advance Transfer15 180 1830 230 3045 270 6060 310 110 75 330 170

For a 50 degree turn:

Advance = 283 yds Transfer = 77 yds

TR

- 0

00

T

TR -

050

T

A

100 0 100 200 300

B

TR

Scale in Yards

N77yds

90º

TR

- 0

00

T

TR -

050

T

A

100 0 100 200 300

B

TRTB 270

2

81 Y

ds

Scale in Yards

N

Turn Point

Steadying Point

TR

- 0

00

T

TR -

050

T

A

100 0 100 200 300

B

TRTB 270

90

CD Scale in Yards

N

Lt Ho

WO

A070

005

Actual Track - 1

Actual Track - 2

Pick a turn bearing navaid close to the beam.

Lt Ho

WO

A070

005

Actual Track - 1

Actual Track - 2

Pick a turn bearing navaid parallel to new course – automatic adjustment to back on track

- Many means are provided to help keep a ship on track (i.e., specially constructed ranges, direction lights,etc.).

- However, should nothing be provided specifically designed for the purpose, it is often possible to select an object that the ship runs towards and use as a head bearing. By knowing what the object should bear, the determine which side of track the ship lies.

Establishing Position

010 020

010 020

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