Submarine Torpedo Fire Control Manual, is a training and reference manual from 1952. It describes how to plan a submarine's approach and attack using the fire control systems on Fleet and Guppy submarines with straight running torpedos (without homing, wire guidance, etc.). It represents the submarine fire control problem of WW II and the immediate post war period.

In this online version of the manual we have attempted to keep the flavor of the original layout while taking advantage of the Web's universal accessibility. Different browsers and fonts will cause the text to move, but the text will remain roughly where it is in the original manual. In addition to errors we have attempted to preserve from the original, this text was captured by a combination of optical character recognition and human typist. Each method creates errors that are compounded while encoding for the Web. Please report any typos, or particularly annoying layout issues to the HNSA Feedback Form for correction.

Thank you to the Wisconsin Maritime Museum, USS Cobia for providing a photocopy of the manual.

Richard Pekelney
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COMMANDER SUBMARINE FORCE
UNITED STATES ATLANTIC FLEET
U.S.S. FLYING FISH (SS229), FLAGSHIP

18 April 1950

LETTER OF PROMULGATION

1. The Submarine Torpedo Fire Control Manual is a nonregistered Confidential publication and shall be transported, handled, and stowed as prescribed by U.S. Navy Regulations and the Registered Publications Manual.

2. This Manual has been prepared by officers of the Submarine School to be used as a text for the officers Basic Submarine Tactical and Prospective Commanding Officers courses of the Submarine School. It is issued to the Submarine Force, U.S. Atlantic Fleet as a suitable guide in organizing and operating a Torpedo Fire Control party. The terminology and procedures should be considered as standards wherever material and personnel allowances permit. The doctrine expressed in this Manual is considered to be excellent but not mandatory. Its use, as always, is dependent upon the existing situation and the judgement of the Commanding Officer.

3. Comments and recommendations are invited for correction and revision in 1952.

4. THIS DOCUMENT CONTAINS INFORMATION AFFECTING THE NATIONAL DEFENSE OF THE UNITED STATES WITHIN THE MEANING OF TITLE 18, U.S.C., SECTIONS 793 AND 794. ITS TRANSMISSION OR THE REVELATION OF ITS CONTENTS IN ANY MANNER TO AN UNAUTHORIZED PERSON IS PROHIBITED BY LAW.

5. IT IS FORBIDDEN TO MAKE EXTRACTS FROM OR TO COPY THIS PUBLICATION WITHOUT SPECIFIC AUTHORITY FROM THE CHIEF OF NAVAL OPERATIONS EXCEPT AS PROVIDED FOR IN ARTICLES 9-9 AND 9-10 U.S. NAVY SECURITY MANUAL FOR CLASSIFIED MATTER.

DISTRIBUTION

CNO	50
CinClantFlt	1
ComSubPac	100
ComSubRon TWO	1
ComSubRon FOUR	1
ComSubRon SIX	1
ComSubRon EIGHT	1
ComSubDevGru TWO	1
ConiSubDiv TWENTY-ONE	1
CouiSubDiv TWENTY-TWO	1
ComSubDiv FORTY-ONE	1
ComSubDiv FORTY-TWO	1
ComSubDiv SIXTY-ONE	1
ComSubDiv SIXTY-TWO	1
ComSubDiv EIGHTY-ONE	1
ComSubDiv EIGHTY-TWO	1
Each SS SubLant	1
CO USS ORION (AS18)	1
CO USS H.W. GILMORE (A516)	1
CO USNavSubBase, NewLon	1
CO USNavSubScol, NewLon	400
SubLant Reserve Coordinator	600
Spares, SubLant	286

iv

LIST OF EFFECTIVE PAGES
(Reverse of all sheets blank)

Subject Matter	Changes in effect	Page Numbers
Title Page	Original	i
Letter of Promulgation	Original	ii
Distribution List	Original	iii
Record of Corrections	Original	iv
List of Effective Pages	Original	v
Table of Contents	Original	vi,vi(a)
List of Illustrations	Original	vii
Forward	Original	viii
Chapter 1	Original	1-1 to 1-13
Chapter 2	Original	2-1 to 2-11
Chapter 3	Original	3-1 to 3-4
Chapter 4	Original	4-1 to 4-6
Chapter 5	Original	5-1 to 5-54
Chapter 6	Original	6-1 to 6-11
Chapter 7	Original	7-1 to 7-7
Chapter 8	Original	8-1 to 8-14
Chapter 9	Original	9-1 to 9-11
Chapter 10	Original	10-1 to 10-6
Chapter 11	Original	11-1 to 11-2
Illustrations	Original	PLATES I - XXIV

v

TABLE OF CONTENTS

		Pages
Chapter 1	- Definitions	1-1 to 1-13
Chapter 2	- Phraseology	2-1 to 2-11
Chapter 3	- Submarine Submerged Characteristics	3-1 to 3-4
	Fleet Type Submarine	3-1 to 3-3
	Guppy II Type Submarine	3-3 to 3-4
Chapter 4	- The-Torpedo Fire Control Party	4-1 to 4-6
Chapter 5	- Duties of the Fire Control Party	5-1 to 5-54
	The Approach Officer	5-1 to 5-22
	The Periscope	5-1 to 5-10
	Periscope Ranging	5-3 to 5-8
	Target Length	5-8 to 5-10
	Periscope Technique	5-10 to 5-13
	Periscope Procedure	5-13 to 5-16
	Duties	5-16 to 5-17
	Periscope Observations	5-17 to 5-19
	Plan of Attack	5-19 to 5-21
	Ship Handling	5-21 to 5-22
	Coordination of Fire Control Party	5-22
	The Attack and Sonar Coordinator	5-22 to 5-24
	The TDC Operator	5-24 to 5-29
	The Assistant TDC Operator	5-30 to 5-32
	The Navigational Plotter	5-32 to 5-42
	The Periscope Assistant	5-42
	The Sonar Plotter	5-42 to 5-51
	Bearing Rate Plot	5-43 to 5-46
	Bearing Difference Plot	5-46 to 5-51
	The Firing Key Operator	5-51 to 5-52
	The Gyro Angle Setter	5-52 to 5-54
Chapter 6	- Spreads	6-1 to 6-11
	Types of Spreads	6-7 to 6-8
	Computed Spread	6-8 to 6-9
	4-3-2-1 Spread	6-9 to 6-10
	Spread Policy	6-10
	Determination of Coverage	6-11
Chapter 7	- Firing Methods	7-1 to 7-7
	Check Bearing Method	7-2 to 7-3
	Continuous Bearing Method	7-4 to 7-5
	Constant Bearing Method	7-5 to 7-6
Chapter 8	- Theory of Approach and Attack	8-1 to 8-14
	Basic Fundamentals of the Approach and Attack	8-1 to 8-8
	Determination of Direction of Target Motion	8-1 to 8-4
	Speed Determination	8-4 to 8-5
	Relative Movement	8-5 to 8-8
	Analysis of Torpedo Firing	8-8 to 8-11
	Analysis of Torpedo Track Angles	8-11 to 8-12
	Down the Throat Shot	8-12 to 8-13
	Deflection Angle for Straight Fire	8-13

vi

TABLE OF CONTENTS

		Pages
Chapter 9	- Submerged Approach and Attack Tactics	9-1 to 9-11
	The Contact Phase	9-1 to 9-2
	The Approach Phase	9-2 to 9-5
	The Attack Phase	9-5 to 9-11
Chapter 10	- Theory of the Periscope Approach and Sonar Attack	10-1 to 10-6
Chapter 11	- Submerged Approach and Sonar Attack Tactics Against Surface Targets	11-1 to 11-2

vi(a)

LIST OF ILLUSTRATIONS

Subject matter	Plate Number
Definitions	I
Periscope Field - TELEMETER SCALE	II
Range Omnimeter - RANGES	III
Stadimeter RANGES	IV
Range Omnimeter - TARGET LENGTH	V
Periscope-Radar PLOT	VI
Stadimeter PLOT	VII
Radar Tracking PLOT	VIII
Bearing Rate PLOT	IX
Bearing Rate Plot Recorder's Form	X
Bearing Difference Plot - Scale 20	XI
Bearing Difference Plot - Scale 10	XII
Bearing Difference Plot Data	XIII
Bearing Difference Plot Data	XIV
Spreads	XV
Relative Movement	XVI
Analysis of Curved Fire - 46 Kt. Torpedo	XVII
Analysis of Curved Fire - 29 Kt. Torpedo	XVIII
Approach and Attack Doctrine	XIX
Situation Analysis, SITUATION I, First Course of Action	XX
Situation Analysis, SITUATION I, Second Course of Action	XXI
Situation Analysis, SITUATION II	XXII
Situation Analysis, SITUATION III	XXIII
Situation Analysis, SITUATION IV	XXIV

vii

FOREWORD

Our submarines during and since the last war have demonstrated their ability to accomplish a variety of special missions of which they had previously been considered incapable. Many of them have been so altered that the accomplishment of these missions have become their primary duties. The primary mission of the true submarine, however, remains, today as it has always been, the delivery of successful torpedo attacks against the ships of an enemy.

The types of targets which a submarine may encounter are many and varied, i.e., single unescorted merchantmen, single destroyers, submerged submarines, unescorted group of ships, convoys, and task forces. The variety of targets and other unpredictable conditions, such as weather and depth of water, render it impracticable to set forth a procedure or doctrine which will apply under all conditions. The submarine Commanding Officer must rely mainly on his own judgement and experience to insure the completion of a successful attack.

There do exist, however, tested and proved procedures and tactics which if followed will assist the submarine Commanding Officer and increase his chances of success. It is the purpose of this book to present to the officers of the Submarine Force under one cover the best known principles of Submarine Fire Control Organization and Torpedo Attack Tactics.

viii

CHAPTER 1

DEFINITIONS

100. ANGLE ON THE BOW: The angle between the line of sight and the target's bow measured to port or starboard of the target's bow from 0 degrees to 180 degrees. Symbol: Ab. See Plate I, figure 1.

101. APPROACH PHASE

The period during which the submarine maneuvers to close to a position for commencing the Attack Phase.

102. APPROACH COURSE

The course or courses taken by the submarine during the Approach Phase.

103. ATTACK PHASE

The period during which the submarine maneuvers for a firing position.

104. COVERAGE

The ratio of the angular or linear distance between the wing torpedoes of a salvo to the angular or linear length of the target corrected for the torpedo track angle.

1-1

105. CRITICAL RANGE:

The range at which the submarine normally passes from the Approach Phase to the Attack Phase. It is equal to a 7 1/2 minute run of the target, and may be easily obtained by dividing the target's speed by 4 and multiplying by 1000. Example: Critical range for a 12 knot target is 3000 yards.

106. DEFLECTION-ANGLE:

The angle between the periscope angle and the component of the gyro angle of the torpedo determined only by track angle, torpedo speed, and target speed. See Plate I, figure 3.

107. DISTANCE TO THE TRACK:

The perpendicular distance from the submarine to the target's track extended. See Plate I, figure 1.

108. DIVERGENT SPREAD:

A spread in which the torpedoes of a salvo intersect the target's track at different points along the target's

1-2

NOTE: This spread is produced by applying an angular offset to each torpedo.

109. FIRING COURSE

The course of the submarine at the instant of firing.

110. GENERATED BEARING

Relative target bearing obtained from TDC position keeper section Relative Target Bearing dial usually given on "Up scope".

111. GYRO ANGLE

The angle between the longitudinal axis of the submarine and the final torpedo track measured right or left of the bow or stern (bow for bow shots, stern for stern shots) of the submarine from 0 degrees to 180 degrees. See Plate I, figure 3.

112. GYRO ANGLE ORDER:

The angle between the longitudinal axis of the

1-3

113. INTERCEPT POINT:

The point at which the torpedo crosses the target track. See Plate I, figure 3.

114. LEAD ANGLE

The angle between the true bearing of the target and the true course of the submarine (or submarine course reversed for stern tube shots).

1-4

A spread in which the torpedoes of a salvo intersect the target's track at different points along the target's length but at the same point on the target's track, and at the same torpedo track angles.

116. NORMAL APPROACH COURSE:

The course which is equal to the true bearing of the target, plus or minus 90 degrees in the direction to close the target's track. See Plate I, figure 1.

117. NORMAL COURSE:

The course at right angles to the target's course in the direction to close the target's track.

1-5

118. OPTIMUM APPROACH COURSE:

The Normal Approach Course with an imaginary target moving along the same course, and at the same speed as the actual target, but on the beam of the actual target at a range equal to the limiting torpedo run on the side closest to the submarine. Symbol: OAC.

119. OPTIMUM TORPEDO TRACK ANGLE:

The torpedo track angle for which expected errors in target course produce the least change in the deflection angle. See Plate I, figure 2.

120. PARALLAX CORRECTION SONAR

The algebraic sum of the angular correction compensating for the longitudinal distances between the sonar equipment and the periscope (P1), the center of the target and its propellers (P2), and the initial and developed positions of the target during the transmission of the sound waves.

1-6

121. PARALLAX CORRECTION TORPEDO TUBE:

The angular correction compensating for the longitudinal distance between the muzzle doors and the periscope. See Plate I, figure 4.

122. PARALLAX HIGH:

The torpedo advance is opposed to the general direction of target motion.

1-7

123. PARALLAX LOW:

The torpedo advance is in the general direction of target motion.

124. PERISCOPE ANGLE:

The angle between the longitudinal axis of the submarine and the computed line of sight at the instant of firing established by the algebraic sum of the

1-8

125. PSEUDO TORPEDO RUN:

The distance in yards between the periscope position at the instant of firing and the point of intercept. (See Plate I, figure 3).

126. REACH:

The initial straight path of the torpedo, measured in yards. Symbol: M. (See Plate I, figure 3).

127. REACH AND TURNING RADIUS CORRECTION:

An angular correction applied to a computed deflection angle, in angled shots, to correct for the reach (N) and the turning radius (z) of the torpedo in proceeding to its final track.

128. SALVO:

A number of torpedoes fired at short-intervals at the same target.

129. SPREAD:

Offset angle or change in target bearing applied to

1-9

130. SPREAD ANGLE:

The additional gyro angle, over that required for hitting the same point of a moving target, applied to successive torpedoes for producing the desired spread.

1-10

The angular motion of the MOT of the target between successive torpedoes. (See sketch on preceding page).

132. TORPEDO ADVANCE:

The perpendicular distance between the torpedo final course and a line through the tube muzzle parallel to the torpedo final course. (See Plate I, figure 3)

133. TORPEDO RUN:

The total distance in yards traveled by the torpedo from the tube to the target. (See Plate I, figure 3)

134. TORPEDO RUN DIFFERENCE:

The actual torpedo run for a given time minus the distance the torpedo would have traveled during the same time at corrected torpedo running speed (final running speed), in yards. Symbol: Uy.

135. TORPEDO RUNNING SPEED CORRECTED:

The uniform running speed in knots of the torpedo under any given conditions after the initial acceleration is completed. Symbol: S'z.

136. TORPEDO TURNING RADIUS:

The radius of the circular track, in yards, of the torpedo from the end of the initial straight path to the beginning of the final straight path. Symbol Z. (See Plate I, figure 3).

137. TRACK ANGLE:

The angle at the point of intercept between the

1-11

138. TORPEDO TRACK ANGLE:

The angle at the point of intercept between the target ships course and the reverse of the torpedo's course, measured to port or starboard of the target's bow. Symbol: TTa.

139. TORPEDO TUBE PARALLAX BASE LINE:

The longitudinal distance between the tube muzzle and the periscope. Symbol: P. (see Plate I, fig. 4)

1-12

The offset angle or linear distance along the target's length or track between adjacent torpedoes of a salvo. (See sketch on preceding page).

141. VOLUME OF FIRE:

The number of torpedoes in a salvo.

1-13

200. STAND BY FOR OBSERVATION (LOOK AROUND (LOOK AT ESCORTS):

A preliminary order given by the Approach Officer to alert the Fire Control Party and inform them of the reason the periscope is to be raised.

201. UP SCOPE:

An order from the Approach Officer to the Periscope Assistant to raise the periscope. This may be combined with a hand signal should the Approach Officer so desire.

202. PUT ME ON:

An order from the Approach Officer to the Periscope Assistant to place the periscope on the generated target bearing.

203. BEARING - MARK:

A phrase used by the Approach Officer or by one of the Radar or Sonar Operators indicating to all members of the Fire Control Party that the target bearing as read on the various repeaters is correct. This is usually paralleled by a buzzer and mark light.

2-1

A phrase which when used by the Approach Officer during a periscope observation directs the Periscope Assistant to read the stadimeter or telemeter range and informs the Fire Control Party of the time of the range. When spoken by the Radar Operator it indicates that the radar is on the target and the range repeaters are reading correctly. It is usually paralleled by a buzzer and a mark light in the latter case.

205. TDC MATCHED:

A phrase used by the TDC Operator during the initial observation to inform the Approach Officer that the TDC is matched in bearing and range.

206, ANGLE ON THE BOW PORT (STARBOARD):

A phrase used in stating the angle on the bow of some designated ship, whether it be target or escort. It is usually spoken by the Approach Officer after an observation arid while the periscope is being lowered. Note that the side of the angle is stated before its value.

207. TARGET HAS ZIGGED TO HIS RIGHT (LEFT):

A phrase used to notify all members of the Fire Control Party that the target group has changed course. When spoken by the Approach Officer following a periscope observation it should be followed by a statement of the new Angle on the Bow.

2-2

A phrase used to notify all members of the Fire Control Party that the target group is changing course. Then spoken by the Approach Officer following a periscope observation it is an order to the TDC Operator to change the target course in the TDC thirty degrees in the indicated direction.

209. GENERATED ANGLE ON THE BOW IS ____:

Report of TDC Operator after the Approach Officer has announced the observed angle on the bow when the generated angle on the bow is within 10 degrees of the observed angle on the bow.

210. INDICATES A ZIG OF ____:

Report of TDC Operator after Approach Officer has announced the observed angle on the bow if the difference between the observed and generated values is more than 10 degrees.

211. DOWN SCOPE:

An order from the Approach Officer to the Periscope Assistant directing him to lower the periscope all the way. In order to reduce conversation in the conning tower during an approach the order may be given by merely raising the periscope handles.

2-3

An order from the Approach Officer to the Periscope Assistant directing him to lower the periscope until the periscope head is under water. This may be given by holding the hands in a horizontal position following a hand signal to lower the periscope.

213. PIP - NO PIP:

A phrase used by the ST radar operator when the periscope breaks water to inform the members of the Fire Control Party and the Approach Officer that he can or cannot obtain a range of the target.

214. SET DEPTH ____ FEET SPEED HIGH (LOW):

An order from the Approach Officer, relayed by the Firing Key Operator, to the Torpedo Tubes directing that the depth and speed spindles on the tubes be set as directed and the spindles withdrawn. The two orders are usually given as one but may be given separately.

215. TUBE ORDER FORWARD (AFT) IS ____:

An order from the Approach Officer to the Firing Key Operator designating the order in which the torpedo tubes are to be fired. It is also relayed by the Firing Key Operator to the Torpedo Tubes for their information.

2-4

An order from the Approach Officer, relayed by the Firing Key Operator to the Torpedo Tubes directing that the designated torpedo tubes be flooded from WRT Tank and be made ready to fire in all respects except for opening the outer doors.

217. OPEN THE OUTER DOORS:

An order from the Approach Officer, relayed by the Firing Key Operator to the Torpedo Tubes directing that the outer doors of tubes previously flooded be opened. The tubes should then be ready in all respects to fire.

218. GYROS FORWARD (AFT) MANNED:

A report from the Gyro Angle Setter to the assistant TDC Operator that his station is manned, gyro angle order is set on 000 (180 aft) and the gyro setter is in automatic.

219. GYROS FORWARD (AFT) MATCH GYROS IN AUTOMATIC:

An order from the Assistant TUC Operator to the Gyro Angle Setter to check his gyro setter in automatic and see that gyro angle order is matching.

2-5

A report from the Gyro Angle Setter to the Assistant TDC Operator, informing him that the gyro setting indicator regulator is matching the indicated value of gyro angle order.

221. GYROS FORWARD (AFT) STANDBY FOR GYRO CHECK - MARK:

An order from the Assistant TDC Operator to the Gyro Angle Setter to note the indicated gyro angle and report its value on the work "MARK".

222. GYROS FORWARD (AFT) SET GYROS _____:

An order from the Assistant TDC Operator to the Gyro Angle Setter to set the torpedo tube gyro spindles at some specific value. This is used only in an emergency caused by TDC failure and is given as a value between 000 and 360.

223. GYROS FORWARD (AFT) MATCH GYROS BY HAND:

An order from the Assistant TDC Operator to the Gyro Angle Setter to operate the gyro setting indicator regulator by hand and match gyros by the "follow the pointer method".

224. SECURE THE GYROS FORWARD (AFT).

An order from the Assistant TDC Operator to the Gyro Angle Setter to position the gyros on 000 (180 aft), place the gyro setter in automatic, and await further orders.

2-6

An order from the Approach Officer to all members of the Fire Control Party in the conning tower which designates the type and amount of spread desired in a salvo of torpedoes.

226. SHOOTING WILL BE BY (CONSTANT BEARING)(CONTINUOUS BEARING)(CHECK BEARING) METHOD, BEARNG EVERY ___ TORPEDO:

An order from the Approach Officer to all members of the Fire Control Party in the conning tower which designates the firing method to be used.

227. CHECK BEARING:

An order from the Approach Officer to the Fire Control Party not to shoot another torpedo until another periscope bearing of the target has been observed and set in the TDC.

228. BEARING ON:

A phrase used by the Approach Officer when firing by the Continuous Bearing method to inform the Fire Control Party that the periscope is on the point of aim. When used by the TBT Operator it informs the TDC Operator that the TBT is on the designated target.

2-7

A phrase used by the Approach Officer when he desires to inform the Fire Control Party that the periscope is not trained on a previously designated point of aim. When used by the TBT Operator it informs the TDC Operator that the TBT is off the designated target.

230. FINAL BEARING AND SHOOT:

This is an order from the Approach Officer to all members of the Fire Control Party to commence shooting as soon as the next bearing (and range if immediately available) is obtained, set in the TDC, and the TDC "correct solution" light is on.

231. STANDBY FORWARD (AFT):

An order from the Approach Officer to the Firing Key Operator who relays it to the Torpedo Tubes, informing them that the tubes are to be fired and to be prepared to fire any tube by hand that does not fire electrically. This order is also relayed to the Control Room to alert the Diving Officer.

232. SET:

A phrase used by the TDC Operator to inform the assistant TDC Operator that the latest and best target information is set in the TDC and be is ready to commence shooting.

2-8

An order from the Assistant TDC Operator to the Firing Key Operator to fire a torpedo. It also informs the Approach Officer that the designated spread is applied to the torpedo to be fixed and that the TDC correct solution light is on.

234. FIRE:

An order from the Approach Officer to the Firing Key Operator to fire the tube previously designated. It is used only when the torpedoes are being fired by the "Constant Bearing" method.

235. FIRE ONE (TWO) (THREE) (ETC):

An order from the Firing Key Operator to the Torpedo Tubes informing them that the designated tube is being fired in the Conning Tower and directing that it be fired by hand if it does not fire electrically.

236. ONE (TWO) (THREE) (ALL) TUBES FIRED FORWARD (AFT):

A phrase used by the Firing Key Operator to inform the Fire Control Party the number of torpedoes which have been fired,

237. CHECK FIRE:

An order from the Approach Officer to the Fire Control Party not to shoot any more torpedoes until directed to do so.

2-9

An order from the Approach Officer directing that the torpedo tube outer door or doors be closed and that the pressure be vented off the tube or tubes. No other changes in the condition of the tubes are to be made.

239. SECURE THE TUBES FORWARD (AFT)(DESIGNATED TUBE):

An order from the Approach Officer to the torpedo tubes directing that the tubes be placed in the normal cruising condition.

240. TRACK TARGET BEARING (RIGHT HAND)(LEFT HAND):

An order from the Approach Officer or Sonar Coordinator directing a Radar or Sonar Operator to track the target designated.

241. TRACK IN HAND (ATF)(GTT):

An order from the Sonar Coordinator to a Sonar Operator directing him to place the training controls of the sonar head in the position indicated and keep the sonar head trained on the target.

242. SHIFT TO HAND (ATF)(GTT):

An order from the Sonar Coordinator to a Sonar Operator directing him to shift the training controls or the sonar head to the position indicated.

2-10

An order from the Sonar Coordinator to a Sonar Operator directing him to count and report the propeller RPM of a designated target.

244. GET A PING RANGE:

An order from the Approach Officer or the Sonar Coordinator to a Sonar Operator directing him to obtain a sonar range of the target.

245. TAKE A SWEEP AROUND:

An order from the Approach Officer or the Sonar Coordinator to a Radar or Sonar Operator directing him to conduct a 360 degree search and report all contacts.

246. CONDUCT A FREQUENCY SEARCH:

An order from the Sonar Coordinator to a Sonar Operator directing him to conduct an all around listening search on all frequencies to determine if any vessels in the vicinity are conducting a supersonic search.

247. KEEP THE BEARINGS COMING:

An order from the Sonar Coordinator to a Sonar Operator directing him to report the bearing of the target as frequently as possible.

2-11

300. GENERAL:

Submerged submarines are very much slower in their reaction to changes of speed and course than surface ships. This characteristic greatly affects the tactics of the approach and attack. For this reason all submarine officers should know the characteristics of their ship.

301. SUBMARINE TYPES:

The following discussion is divided into two parts, namely the Fleet Type Submarine and the Guppy II Type Submarine.

302 - 309. BLANK

310. FLEET TYPE SUBMARINE:

(a) The Fleet Type Submarine will make the following speeds submerged for the length of time indicated, if it starts with a full battery charge:

Knots	Time
3.0	48 hours
6.0	3 hours
8.0	1 hour
9.0	1/2 hour

(b) Thus it can readily be seen that a major consideration when making an approach is conservation of the battery capacity.

3-1

Speed	Time
6.0	1:45 minutes
8.0	2:15 minutes
9.0	2:30 minutes

(a) In order to decelerate to 1/3 speed from the speeds indicated it will take the following time:

Speed	Time
4.0	1:30 minutes
6.0	1:45 minutes
8.0	2:15 minutes
9.0	2:30 minutes

(e) It is interesting to note that it takes about the same amount of time to decelerate from 4 knots and 6 knots to 1/3. Thus when necessary to use speed it is just as well to use 6 knots as 4 knots as far as deceleration is concerned.

(f) The time it takes to decelerate may be decreased by backing the screws one third. The screws will act as a brake. The use of full rudder will tend to slow the submarine and may be used very effectively when decelerating. Full rudder decreases the speed through the water to about 3/4 of what would be made with the rudder amidships.

3-2

Speed	Rate
4 knots	.45 deg/sec
8 knots	1 deg/sec

(h.) The tactical characteristics of a submerged fleet type submarine at 4 knots using 30 degrees rudder are as follows:

Advance	290 yards
Transfer	226 yards
Tactical Diameter	467 yards

311 - 319. BLANK

320. THE GUPPY II TYPE SUBMARINE:

(a) The Guppy II Type of submarine has characteristics different from the Fleet Type. The primary difference is submerged speed. The Guppy II will make the following speeds for the time indicated with a full battery, charge:

Knots	Hours
4.3	48
5.3	36
6.3	20
8.2	10
9.4	6
9.9	5
11.8	3
15.7	1
17.8	30 minutes

3-3

Speed	Time
8 knots	1:00 minute
12 knots	1:40 minutes
15 knots (series)	1:00 minute
17 knots (series)	1:40 minutes

(c) Deceleration to the following speed from flank will take the following time:

Speed	Time
3 knots	4 minutes
8 knots	1:10 minutes
12 knots	0:15 minutes

(d) For approach work insofar as acceleration and deceleration are concerned it is of advantage to go to full speed. rather than standard if speed is desired for acceleration is faster and deceleration is almost equivalent to the point where the periscope may be used. The boat will decelerate faster by going to 1/3 speed (screws act as brake) rather than stop.

(e) At slow speeds turns are slightly faster than those made by the fleet type submarine. There is a marked improvement in ability to turn at the higher speeds.

Speed at Start	Tactical Diameter	Time to turn 90 degrees
4.8 knots	350 yards	2:21 minutes
7.3 knots	350 yards	1:30 minutes
11.7 knots	330 yards	1:00 minute
15.3 knots	380 yards	0:50 minute

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400. GENERAL:

The Submarine Organization provides in its battle bill for the condition known as "Battle Stations Torpedo". This is an all hands evolution requiring specific stations for every member of the ship's complement. The ship's complement at "Battle Stations Torpedo" is divided into three groups: (a) The Fire Control Party, (b) the ship handling and maneuvering party, and, (c) the torpedo handling party. This chapter enumerates the members of the Fire Control Party and lists their primary duties. Their detailed duties and procedures are covered in Chapter VI.

401. APPROACH OFFICER:

The Approach Officer is the officer conducting the approach and the attack. Except in special training exercises he is the Commanding Officer of the submarine. His station is normally in the conning tower at the periscope. When a night attack on the surface is being conducted he may take station either in the conning tower or on the bridge.

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402. ATTACK AND SONAR COORDINATOR:

The Attack and Sonar Coordinator is usually the Executive Officer and is the number two member of the Fire Control Party. His station is in the conning tower. His primary duty is to be informed in detail regarding sonar conditions in order to direct and coordinate the efforts of all the Sonar Operators. His secondary duty is to assist the Approach Officer in coordinating the work of all members of the Fire Control Party.

403. TDC OPERATOR:

The TDC Operator is an officer whose station is in the conning tower at the position keeper section of the TDC. His primary duty is to operate the position keeper and, using all available information, obtain the most accurate values of target course, speed, and range that can be determined.

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The Assistant TDC Operator is an officer whose station is in the conning tower at the angle solver section of the TDC. He has two primary duties: (a) to assist the TDC Operator in obtaining the course and speed of the target, and (b) to insure that the proper gyro angle is set on each torpedo when it is fired.

405. NAVIGATIONAL PLOTTER:

The Navigational Plotter is an officer whose station is in the conning tower at the DRT. His primary duty is to maintain a navigational plot of the target or targets designated by the Approach Officer. He furnishes the TDC Operator and the Approach Officer the values of target course and speed obtained from the plot. In addition he furnishes predicted data regarding the target's position based on best known target course and speed, if requested.

406. PERISCOPE ASSISTANT:

The Periscope Assistant is an enlisted man, usually a quartermaster, whose station is at the periscope being used by the Approach Officer. His primary duty is to assist the Approach Officer as directed in his operation of the periscope.

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The Sonar Plotter is an officer whose station is in the control room. His primary duty is to obtain the course of the target from information furnished by sonar.

408. SONAR PLOT RECORDER:

The Sonar Plot Recorder is an enlisted man whose station is in the control room. His primary duty is to record the sonar bearings of the target as directed by the Sonar Plotter and assist him in obtaining the course of the target.

409. SONAR OPERATORS:

The Sonar Operators are enlisted men who are specially trained in the operation of sonic and supersonic sonar equipment. Their primary duties are to provide bearings end ranges of ships designated by the Sonar Coordinator in the manner and when directed by him. There are at present three sonar stations in a fleet or guppy submarine, as follows:

Sonar I	- JT in forward torpedo room.
Sonar II	- WFA or WCA in conning tower.
Sonar III	- WFA or WCA in conning tower or in forward torpedo room.

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The ST Radar Operator is an enlisted man whose station is at the ST console in the conning tower. His primary duty is to furnish the Approach Officer and other members of the Fire Control Party the ranges of targets designated by the Approach Officer. He may also be directed by the Approach Officer to furnish approximate bearings.

4.11. FIRING KEY OPERATOR:

The Firing Key Operator is an enlisted man, usually a Fire Controlman, whose station is at the firing panel in the conning tower. His primary duties are to relay orders from the Approach Officer to the torpedo tubes and to fire the torpedoes when directed to do so.

412. GYRO ANGLE SETTERS:

The Gyro Angle Setters are enlisted men. They are stationed one in each torpedo room, at the gyro setting indicator regulators. Their primary duties are to see that the correct gyro angles are being set on the torpedo tubes as directed by the Assistant TDC Operator.

4.13. SS RADAR OPERATOR:

The SS Radar Operator is an enlisted man whose station is at the SS Radar Console in the conning tower. His primary duties are to provide the Approach Officer and other members of the Fire

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414. SV RADAR OPERATOR:

The SV Operator is an enlisted man. He may be stationed at the SS console in the conning tower or the SV console in the control room depending upon the tactical situation. His primary duties are to provide ranges and bearings of aircraft or surface targets as directed by the Approach Officer.

415. TBT OPERATOR:

The TBT Operator is an officer whose station is at either the forward or after TBT on the bridge. His primary duty is to furnish the Fire Control Party bearings of the target and other information regarding the movements of the target or targets designated by the Approach Officer. This station is manned only during surface attack.

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500. THE APPROACH OFFICER

(a) The Periscope The periscope is the most important instrument at the command of the Approach Officer. It is by his use of the periscope that he is able to furnish the members of the Fire Control Party the information they need to compute and set the proper gyro angle on the torpedoes as they are fired. Let us, then, before discussing his duties, review briefly the salient features of the periscopes now in use and the techniques of their use.

(b) The two periscopes presently installed in fleet submarines are the type IV in the number one position and the type II in the number two position. Although these are alike in many respects the most outstanding difference is that the type IV contains a radar by means of which ranges may be obtained. The main characteristics of the two periscopes are as follows:

	Type II	Type IV
Magnification high power	6.0X	6.0X
Magnification low power	1.5X	1.5X
Maximum elevation of line of sight (above horizontal)	74.5 degrees	45 degrees

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An examination of the above tables reveals that in order to obtain radar ranges we have had to sacrifice: (a) about six feet of periscope depth, (b) the ability to conduct a visual search above 45 degrees, and (c) 2.3 inches in the size of the tapered section of the tubs. These facts should be borne in mind when selecting the periscope to be used in different tactical situations.

The field of the periscope in low power (32 degrees) is four times the field in high power (8 degrees), but at the same time objects appear only 1/4 as big in low power as in high power with consequent reduction in detail. This can be clearly seen in Plate II.

Referring to Plate II we see that the reticule of the periscope has inscribed on it a series of vertical end horizontal lines. In low power each small division represents one degree while in high power each all division represents 1/4 degree. If the Approach

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R(range) = (19.1 h / n) R(range) = (76.2 h / N)

R = range in yards h = height in feet n number scale divisions low power N number scale divisions hi power

Plate III is a picture of one type of scale ("range omnimeter") which may be constructed. In the figure the masthead height of the target is 100 feet. The arrow of the sliding scale is set opposite the masthead height and the range is read opposite the number of divisions. In this case 1550 yards is read opposite 5 divisions high power and 1 1/4 divisions low power. Ranges obtained in this manner are commonly referred to as "telemeter ranges". Estimates of

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(c) The second method of obtaining ranges is by means of the stadimeter installed in the Type II periscope. The stadimeter relies for its operation upon the formation of two identical images which can, by means of a handwheel on the periscope, be vertically displaced with relation to each other. Normally the handwheel is at the limit of its counter-clockwise travel. To obtain a range, the handwheel is turned clockwise until the target masthead in one image coincides with the target waterline in the other image. The range is then read on the stadimeter scale opposite the appropriate masthead height. In Plate III, a picture of a stadimeter scale, a masthead height of 60 feet gives a range of 2300 yards. Note that the scale is constructed for high power observation. When ranges are measured in low power the computed value must be divided by four.

(d) The third method of obtaining ranges is by use of the radar installed in the Type IV periscope. In this method the range of the selected target is measured directly by the ST Radar Operator when the periscope is raised and trained on the target.

(e) Of the three methods the radar ranges are the most accurate and depend primarily upon the adjustment of the radar which is usually plus or minus 35 yards. The accuracy of telemeter or stadimeter

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ranges depend first, upon the skill of the observer and second, upon the accuracy of the estimate of target masthead height.

(f) The value of the masthead height of the target may be obtained by intelligence, estimate, or by a method referred to as "radar stadimeter" (telemeter) estimate. The latter of course is the most accurate and is accomplished as follows; assuming that the target has been tracked using the ST periscope, the Type II periscope is raised immediately following an ST periscope observation, a stadimeter range observation is made as described above, but instead of reading range on the scale, the masthead height is read opposite the value of the TDC generated range.

(g) When radar ranges cannot be obtained the Approach Officer must rely upon his ability to correctly estimate the height of the funnel or masthead, or other prominent mark on the ship's structure above the water line. If the target ship can be properly identified an accurate value may be obtained from intelligence information supplied the ship. If this is not available the following procedure will he of assistance:

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(h) The following points should be kept in mind in height determination:

Regardless of the methods employed by the individual Approach Officer, skill in estimating masthead heights, and ability to obtain accurate ranges can

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be acquired and maintain only by constant practice. Even when radar ranges are available daring an approach the Approach Officer should also obtain telemeter ranges as a means of improving and maintaining his skill.

501. TARGET LENGTH

(a) The length of the target may be obtained by estimate based on intelligence, by observation with the horizontal telemeter scale, or by observation with the stadimeter. As in estimating masthead height accurate identification of the target make it possible to obtain its length from available intelligence information. There is, however, no yardstick which may be used as a guide.

(b) When the length is to be obtained from a telemeter observation the number of divisions subtended by the target on the horizontal scale is measured in the same manner as when obtaining ranges. In Plate II the target subtends about 12 divisions in high power and therefore 3 divisions in low power. Since we see a foreshortened length of the target we must correct the computed length for angle on the bow. The horizontal and vertical telemeter scale are identical so we may set up the following relation:

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(c) Since these formulas are identical with the ones for obtaining range except that L is substituted for h and the value sin Ab added we may obtain the value of the foreshortened length by setting the number of scale divisions opposite the radar, observed, or TDC generated range and read the foreshortened length opposite the arrow on the masthead height scale. We now need to correct this value for angle on the bow. Plate V shows the scale set for the conditions shown in Plate II assuming an angle on the bow of 40 degrees. Note that in this case the number of telemeter divisions, 12 high power or 3 low power, is set opposite 1/2 the range, 920 yards. This is done because the masthead scale does not go above 200 feet. The foreshortened target length is then 290 feet or twice the value read opposite the arrow. On the second sliding scale the angle on the bow 400 is set opposite the target length 290 feet and opposite the arrow at 90 degrees we read 450 foot the full target length.

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Just as is true in ranging with the periscope the accuracy of the target length determined depends upon the skill of the Approach Officer.

502. PERISCOPE TECHNIQUE

(a) Good periscope technique may be simply defined as the ability to obtain the maximum amount of accurate information, with the minimum length exposed, in the minimum time. The Fire Control Party is directly dependent upon information obtained from periscope observations for a correct solution of the problem. For this reason Approach Officers should devote thought and time to the perfection of their periscope technique to insure that they are able to provide the Fire Control Party all the

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(b) There are no set rules which can be laid down which will apply under all conditions. The following, if followed, however, should be of assistance:

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503. PERISCOPE PROCEDURE

The procedure employed in all periscope observations

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is essentially the same. However, since the range may be obtained in three different ways there are slight variations in the procedure depending on how the range is to be obtained. For purposes of clarity the complete procedure for each type of observation will be given:

(a) ST Periscope Observation
Approach Officer	Standby for observation
TDC Operator	Bearing (range and angle on the bow, if desired)
Approach Officer	Up periscope
Periscope Assistant	Raises periscope and places it on the bearing announced by the TDC Operator
ST Radar Operator	When periscope breaks water announces PIP or NO PIP
Approach officer	Bearing ____ Mark! Down Scope
Periscope Assistant	On bearing _____ Mark! rings the bearing buzzer or if the bearing transmitter is out of order, announces the bearing. Lowers the periscope.
ST Radar Operator	Obtains range and immediately following the bearing buzzer rings the range buzzer
Approach Officer	Angle on the bow _____ or target has zigged angle on the bow ____or target is zigging to his right (left)
TDC Operator	Generating ____ or indicates a zig of ____ degrees

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(b) Stadimeter Observation
Approach Officer	Standby for observation
TDC Operator	Bearing ____ (angle on the bow, if desired)
Approach Officer	Up Periscope
Periscope Assistant	Raises periscope and places it on the bearing announced by the TDC Operator
Approach Officer	Bearing ____ mark!
Periscope Assistant	Rings the bearing buzzer or if transmitter is out announces the bearing
Approach Officer	Range ___ mark! (Masthead ____feet). The Approach Officer may announce a masthead height should he desire to use a value different from that previously decided upon.
Periscope Assistant	Range ______ .
Approach Officer	Down scope. Angle on the bow ____ or (see ST observation.
TDC Operator	Generating or indicates a zig of _____ or indicates a zig of _____ degrees.

(c) Telemeter Observation
Approach Officer	Standby for observation
TDC Operator	Bearing _____ (angle on the bow, it desired)
Approach Officer	Up periscope
Periscope Assistant	Raises periscope and places it on the bearing announced by the TDC Operator
Approach Officer	Bearing Mark!

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Periscope Assistant	Rings the bearing buzzer or if transmitter is out announces the bearing
Approach Officer	RANGE MARK, DOWN SCOPE, Range ____ Divisions ____ Angle on the bow ____ or (see ST observation)
Periscope Assistant	Range yards. This value of range is obtained from the range omnimeter. Some Approach Officers prefer to operate the range omnimeter themselves. Either procedure is acceptable.
TDC Operator	Generating _____ or Indicates a zig of ____ degrees

NOTE: Regardless of type of observation the Approach Officer, at the initial observation, should not give the order DOWN PERISCOPE until the TDC Operator has announced MATCHED, Procedure may require TDC Operator to announce own speed on STANDBY FOR OBSERVATION when It exceeds 3 knots should the Approach Officer desire.

(d) Since the accuracy of the ranges is variable when using the stadimeter or telemeter the Approach Officer should inform the Fire Control Party when he considers the range accurate or doubtful. When approaching the firing point the phrase "FINAL OBSERVATION" should never be used. It has no special significance and will almost invariably confuse the Fire Control Party.

504. DUTIES

The duties or the Approach Officer are to:

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505. PERISCOPE OBSERVATIONS

At the initial observation following contact with the target the Approach Officer should furnish the Fin Control Party all details which are available to him at that time regarding the number and type of ships in the target groups This information should be sufficiently detailed to make it possible to identify the target in available intelligence publications so that an estimate of the target masthead height, length, and major characteristics may be available. He should furnish the Fire Control Party a careful description of the disposition of the target group, the approximate location and activity of air cover and screens if present. If time is available a rough sketch and out

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Although it is not possible to determine target speed merely by observation, general information indicating whether the target appears to be making high, or low speed will be helpful to the Fire Control Party. During

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The Approach Officer will err more times in not providing his Fire Control Party with sufficient information than he will in giving them too much information. In training himself he should endeavor to conduct his approach in such a manner that the members of the Fire Control Party will not have to request from him any information which he has not already given to them.

506. PLAN OF ATTACK

(a) As early In the approach as possible the Approach Officer should inform his Fire Control Party of the target or target be to be attacked, whether the attack is to be made upon a single target, whether it is to be divided fire from a single tube nest against 2 or more targets, or whether he is to fire both the bow and the stern tubes. he should inform the Fire Control Party of the number of torpedoes to be fired at the target or targets, the depth and speed setting to be

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(b) He should inform the Torpedo Rooms of the firing order of the torpedoes. When a full load of one type torpedo is being carried on board the order in which the tubes are fired is not or great importance, If, however, a mixed load of torpedoes is being carried a definite tube firms order is the Approach Officer's only insurance that the torpedoes fired are the ones he planned to fire. For this reason it is good training to indoctrinate the Fire Control Party and the Torpedo Rooms to expect the designation of a firing order.

(c) The Approach Officer should direct that the tubes be flooded before it may be necessary to rely on sonar information so that the sonar equipment will not be blocked out at a critical time by the noise which occurs when the tubes are flooded.

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(d) There are various methods of firing. These are described in detail in Chapter 7. It is extremely important that all members or the Fire Control Party know which method of firing the Approach Officer intends to use and that he train himself and the Fire Control Party until they are proficient as a team in the selected method. Much confusion will occur at the firing point if the Fire Control Party is not thoroughly drilled in this phase of the attack. All the work and the risk involved in a careful approach and attack is wasted if errors are introduced in the TDC at the moment of firing.

507. SHIP HANDLING:

The Approach Officer issues all orders to the helm, all changes in depth and attitude of the submarine. It is advisable for an inexperienced Approach Officer to make a conscious effort to check off in his own mind prior to an observation the actual depth of a submarine, the

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508. COORDINATION OF FIRE CONTROL PARTY:

All members of the Fire Control Party rely upon the Approach Officer for information and for decisions during the course of an approach. In a well coordinated Fire Control Part: there is never any doubt in the minds of the individual members as to what is expected of them at any given time and under any given conditions. This situation cannot be arrived at over night or by any "quick and easy method". It will exist only if the Approach Officer devotes much thought and time to self training and the establishment of set phraseology and procedures which are carefully followed and meticulously adhered to.

509. BLANK

510. THE ATTACK AND SONAR COORDINATOR:

(a) The aided emphasis that has been placed upon sonar by new developments in anti-submarine warfare and the use of submarines is anti-submarine warfare ships have brought to light many deficiencies in our present submarine sonar equipment and the need for increased efficiency in obtaining and processing available sonar information. In the past the executive officer has been

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(b) As the Sonar Coordinator of a submarine his duties should include the supervision and training or the Sonar Operators according to sane planned schedule with the end that he should be intimately acquainted with their capabilities and limitations. He should be charged with the development of set operating procedures and the indoctrination of the Fire Control Party in standard sonar phraseology and orders.

(c) During torpedo attacks and torpedo evasion he should integrate the Sonar Operators into the Fire Control Party and supervise their operations. He should see that the best available sonar bearings are being supplied the TDC, designate to the various sonar operators the targets which they are to track and assist them with additional information from time to time to insure that they do not become confused and track the wrong targets. He should supervise the tracking of the sonar plotting party and see that they are supplied with the information necessary to properly fulfill their mission as members of the Fire Control Party.

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(e) He should be familiar with the sonar conditions existing during the approach, such as the optimum listening range of the day, the optimum range of the day, the location of layers and the optimum evasion depth so that he may properly advise the Captain and furnish him this information when desired.

(f) As the attack coordinator he should be alert to remind the Approach Officer when routine orders and procedures have been inadvertently neglected and assist the approach officer in any other manner he may desire.

511 - 519. BLANK

520. THE TDC OPERATOR:

(a) Details of Operation

The details of the operation of the TDC are discussed in OP1442A. The information presented here will consist only of the duties of the TOC operator as a member of the Fire Control Party.

(b) Manning the TDC

1. Check to see the proper power and own ship's inputs (course and speed) are available and being received correctly.

2. Check timer reset to zero and start the problem upon the order of the Approach Officer or Other designated. officer. Also check to see that the TDC timer is synchronized

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(c) Initial Speed Setting

1. At the beginning of the problem set target speed to a value obtained from the Approach Officer or to a value determined by experience. In lieu of a better estimate an initial analyzing speed of 15 knots, which is a good. average speed determination is to be used.

2. If radar tracking is being conducted set target speed on the value determined by Plot, or to zero if the speed zero method of speed determination is to be used.

(d) Initial Observation Procedure

1. See chapter 5, para. 503, Periscope Procedure.

2a. Match the observed values in the receiver section of the TDC for an ST observation.

b. Enter the observed values as announced by the respective members of the Fire Control Party for a stadimeter or telemeter observation.

3. When the observed values are set in the TDC report "MATCHED".

(e) Successive Observation Procedure

1. See chapter 5, para. 503, Periscope Procedure.

2. On the order "STANDBY FOR OBSERVATION", announce the generated target relative bearing, own ship's speed (if desired), angle on the bow (if desired) and the generated range (except for stadimeter and telemeter observations).

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b. For a stadimeter or telemeter observation read and announce the bearing correction and match the observed value in the receiver section of the TDC. When the Assistant TDC Operator has computed the range correction, enter the correction in the TDC.

4. After the periscope has been lowered the TDC Operator carries out the angle on the bow procedure which follows:

a. If the observed angle on the bow is within 10 degrees of the generated value announce GENERATING _____, and reset or leave the angle on the bow as directed by the Approach Officer.

b. If the observed angle on the bow is not within 10 degrees of the generated value announce INDICATES A ZIG OF ____ DEGREES, and set the angle on the bow called by the Approach Officer.

c. if the Approach Officer reports THE TARGET HAS ZIGGED TO HIS RIGHT (LEFT), ANGLE ON THE BOW IS ____ set the new angle on the bow.

d. If the Approach Officer reports THE TARGET IS ZIGGING TO HIS RIGHT (LEFT), zig the target 30 degrees in the indicated direction and await further observation of the angle on the bow to adjust the TDC.

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(f) Speed Determination

The TDC Operator must coordinate the determination of target speed through his own analysis and that of the Assistant TDC Operator and Plot. After the angle on the bow has been set on each observation the TDC Operator must mentally calculate the speed and angle on the bow. This he must do primarily to act as a check against mistakes made by the Assistant TDC Operator. Methods of mental calculation are discussed in OP1442A. When the solutions for target course and speed by the TDC Operator, the Assistant TDC Operator, and Plot are not in close agreement the Approach Officer should be so informed. During firing the TDC Operator must maintain a close check on the target data in conjunction with Plot. Any pronounced deviations in target data should be announced to the Approach Officer. It is to be emphasized that Plot and Assistant TDC Operator are aids to the TDC Operator and the responsibility for correct target course and speed rests upon the TDC Operator.

(g) Radical Changes in Range

Similar to the angle on the bow procedure, radical changes in range should be brought to the attention of the Approach Officer prior to entering in the TDC.

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(h) Utilization of Sonar Data

Between periscope observations in the approach phase the TDC Operator should evaluate the TDC solution with the sonar information available. Particularly, zig indications and angle on the bow errors should be announced. In the attack phase and in pure sonar attacks the TDC Operator should keep the generated TDC target relative bearing matched with the sonar bearings. At all, times the target length dial should be properly set in order to keep the generated target star bearing corrected.

(i) Critical Range

When a target speed has been obtained it should be announced with the critical range. As the target, speed changes in the solution the new speed and critical range should be announced.

(j) Supplying the Approach Officer Information

Since the Approach Officer often does not have satisfactory access to the position keeper section of the TDC, the TDC Operator must provide him with same or all of the following:

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(k) Masthead Height Check

The TDC Operator should announce the generated range when the Approach Officer orders STANDBY FOR MASTHEAD HEIGHT CHECK. See chapter 5, Approach Officer, Masthead Height.

(1) Firing Point Procedure

521 - 529. BLANK

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530. THE ASSISTANT TDC OPERATOR:

The detailed duties of the Assistant TDC Operator are discussed in OP 1442A. The information presented here will consist of the duties of the Assistant in relation to the Fire Control Party.

531. MANNING THE ASSISTANT TDC STATION:

The Assistant will man the Assistant TDC station and put on the JA head phones. This circuit has the Forward and After gyro setting indicator regulator operators on it. The Assistant should make a communication check with the respective GSIR Operators. He should check the TDC Gyro Angle Indicating and Regulating switches in the OFF position.

532. ANALYZING:

Using the standard analyzation form the Assistant TDC Operator makes a comparison between the generated and observed values and computes speed and angle on the bow. This information is given to the TDC Operator for use in the TDC. The Assistant should keep the PDC Operator advised of each new computed speed and from his computations advise the Approach Officer of the computed angle on the bow.

The methods of analyzing are described in Mk. 4 TDC Operating Procedure .

533. GYRO ANGLE ORDER CHECK:

At approximately the critical range the Assistant should stop analyzing. At this time he should be able to determine whether it will be a bow or stern tube shot and he should use, the following procedure in engaging the Gyro Setting Indicator Regulator.

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Assistant TDC Operator	Gyro Setter
A. If gyros are less than 150 degrees Gyros forward or aft match Gyros in automatic. Turn switch to IND-REG position.	A. When gyros match and settle down, report TDC Gyros Forward (or Aft) matched in automatic.
B. Gyros Forward or Aft Standby for Gyro check.	B. Gyros Forward (or Aft) Standing By.
C. Standby - Mark!	C. Reads gyro angle order to the closest 10' and reports.
D. Check.

If the gyro angle order does not check within 10' the above procedure should be repeated. If it does not check again the transmission should be checked by the Fire Controlman if time permits. If time is not available it will be necessary to set gyros by hand.

534. SPREAD COMPUTATION:

The Approach Officer will give the Assistant TDC Operator the following information as soon as it is available:

The Assistant TDC Operator should compute the spread in accordance with chapter 6.

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At the firing point, after the TDC Operator announces SET for the first torpedo, the Assistant TDC Operator announces SHOOT, if he has the correct spread set in the TDC and the correct solution light is on. The Assistant TDC Operator then waits for a period of five seconds or until he is sure that the torpedo has left the tube and he repeats the above procedure for the remaining torpedoes. If there is no check bearing between successive torpedoes he announces SHOOT when the above conditions are met, namely spread set, correct solution light on, and he is certain that the preceding torpedo has left the tube.

536-539 BLANK.

540. THE NAVIGATION PLOTTER:

The Navigational Plot is one of the most important stations in the submarine fire control party. It is the only source from which a picture of the entire approach can be obtained. The Navigational Plot furnishes valuable information on target speed, target course, times of target zigs, average length of zig legs, and predicted target range when the submarine is below periscope depth. In order to furnish the Fire Control Party with this valuable information the Navigational Plotter must strive for accuracy, neatness, and speed. This may be accomplished only with

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The most important tools of the Navigational Plotter are the Dead Reckoning Tracer (DRT), the Parallel Motion Protractor (PMP), the Bearing and Range Indicator, and speed scales or speed dividers. Before describing the plotter in action let us consider the proper use of these instruments.

541. DEAD RECKONING TRACER (DRT)

The Dead Reckoning Tracer on submarines is a glass topped table with a light "bug" under the glass. The "bug" with its projected spot of light indicates own ship's position at any time from inputs supplied by the ship's gyro and underwater log. Two switches on the point of the table energize the North-South, East West component motors. The scale of the "bug" travel is determined by the scale setting device. This device may be set on 500 yd/in., 1000 yd/in., and 1-8 mi/in. (Later modifications also have 200 yd/in.), The 1-8 mi/in, scale has an additional scale for selection of scales between 1-8 miles/in. The scale of 1000 yd/in. Is normally used for submerged approach plotting and the DRT table should be set up on this scale for normal cruising. The "Bug" on the DRT is moved to any position by two handwheels located on the front of the table.

The Parallel Motion Projector is normally used in

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542. THE PARALLEL NOTION PROTRACTOR (PMP)

The Parallel Motion Protractor, sometimes called a drafting machine, is a protractor cammed by a parallel-motion linkage which is fastened to the upper edge of the DRT table. The linkage permits the movement of the protractor to any part of the table with out loss of orientation. The graduated protractor rim

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(a) Direct Plotting:

(b) Indirect Plotting:

Indirect plotting makes use or the reciprocal

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543. THE BEARING AND RANGE INDICATOR:

The Bearing and Range Indicator is the source from which the plotter gets the information to Plot. He must insure that the proper selector switches are energized for the stations from which he is to receive his information. The Bearing and Range Indicator indicates True Bearing and Range in thousands of yards.

544. SPEED SCALES OR DIVIDERS:

There are numerous aids for the plotter for converting distance run in a length of time to target speed. Rulers properly calibrated are issued by BuShips. Curves and tables may be made up by the individual plotter, or speed dividers may be obtained. The individual Navigational Plotter must try them all and select the one which he considers best for his own use.

There are three types of plot that the Navigational

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545. THE PERISCOPE RADAR PLOT (Refer to Plate VI):

The Periscope Radar plot is made from optical bearings and radar ranges. This information is the most accurate that can be obtained on a submarine. Since the information is accurate the plot is easy to make and analyze. Referring to Plate VI we will trace the plot out point by point and see what information was obtained by the plotter and how he obtained it.

At problem time 0:15 an observation is taken. The Plotter records on a convenient place on his plot the time, true bearing, range and angle on the bow. He then plots this observation, drawing the angle on the bow relative to the bearing line. Since this is the initial observation the plotter has no intonation to

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(a) Target Speed - The plotter finds the leg speed to be 17; this is not, however, the speed he gives to the Approach Officer. He goes beck to time 0:15 and from there measures the speed made good along the targets courses to time 6:30. This speed, called the overall speed, he finds to be 15 1/2 and announces it.

(b) Target course - Since the new target course at this time is merely that estimated by the Approach Officer's angle on the bow, the plotter does not announce a new course at this time.

(c) Zig time - To find the first estimate of zig time the plotter extends the angle on the bow line back to the intersect with the target's old course line. This intersects at the four minute DR. The plotter

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At time 8:00 an observation was plotted and the plotter announces the following information:

Target Speed:	OVERALL TARGET SPEED 15 1/2
Target Course:	NEW COURSE 150
Angle on the Bow:	ANGLE ON TIME BOW OVERESTIMATED BY 20 degrees
Zips Tie:	CORRECTED ZIG TIP 5 MINUTES

This corrected zig time was found by running the target's new course line and back to the old course line and taking the thee at the point of intersection.

Immediately after this observation the Approach Officer had to go below periscope depth. The plotter by making a DR track of the target is able to give the Approach Officer the present range at any time until the target zigs. At time 10:00 the Approach Officer asked for the range. The plotter calls out RANGE ____; the DR range at that time.

546. STADIMETER PLOT:

The source of information for the stadimeter plot is the periscopes Optical bearings, and stadimeter ranges are supplied by the Approach Officer together with his estimate of angle on the bow. Since the errors in stadimeter ranges may be great and variable the plot is much harder to make and analyze than the

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A system of fairing in the target's course through the observed points must be used. The plotter must lean heavily on the Approach Officer's angle on the bow in arriving at the proper course line. In general the smaller angles on the how and the shorter ranges will he the most accurate. This must be taken into account when fairing in the target's course line. Overall target speed is, always, used in this type plot. The overall speed is taken along the faired in course line from the first bearing line to the last.

Zig time is computed in the same way as for the periscope radar plot. First estimate is obtained using the Approach Officer's angle on the bow. When new faired in course line is constructed a better estimate should be found. Plate VII is a typical stadimeter plot.

517. THE RADAR PLOT

The source of information for the radar plot is either the surface search or aircraft search radar. The information may be received with any frequency desired by the plotter. Since a great number of points may be plotted in a short time a very good course and speed may be determined quickly. Since no angle on the bow is received the target's course is wholly dependent upon the accuracy of the plotter. The plotter should select a time interval between

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The points in a radar plot are plotted in the same manner as the other plots. Since there will be many more points a solid bearing line from own ship through the target position should be plotted every fourth or fifth observation to keep the plot oriented. Plate VIII is a sample radar plot.

548. THE NAVIGATIONAL SONAR PLOT

When the approach is being made with the aid of sonar bearings only the Navigational Plot can still furnish much valuable information to the TDC. Using a known or assumed speed the Navigational Plotter can fit this speed in between bearing lines and furnish TDC with reasonably accurate courses and ranges. This type plot is particularly valuable when the entire approach is made on sonar information only.

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549. BLANK

550. PERISCOPE ASSISTANT:

The duties of the Periscope Assistant are as follows:

1. Raises and lowers the periscope in use on orders from the Approach Officer.

2. When the periscope is raised places it on the bearing designated by the TDC Operator.

3. Announces the relative bearing on the order BEARING MARK from the Approach Officer, when required, or rings the bearing buzzer.

4. Reads and announces the stadimeter range on the order RANGE MARK from the Approach Officer or operates the range omnimeter if telemeter ranges are being used. Computes the target length with the range omnimeter when required.

5. When the Approach Officer is observing the target group informs him when the keel depth of the submarine varies 1 foot or more from the ordered depth.