INTRODUCTION TO SONAR 



system used, each one has the same purpose— to 

 direct fire to the target. 



Shipboard System 



A shipboard underwater fire control system 

 (representative of the Mk 105) is illustrated in 

 figure 7-14. The system performs the following 

 functions: 



1. Integrates associated fire control equip- 

 ment with own ship components. 



2. Computes sonar and weapon stabilization 

 data, analyzes target motion, and provides a 

 solution to the ASW fire control problem. 



3. Provides ballistic control data for stern- 

 dropped depth charges, hedgehogs (both fixed 

 and trainable), A/S homing torpedoes, and train- 

 able rockets (weapon A). 



Target location information is supplied by the 

 sonar to the ballistic computer (such as the Mk 5 

 attack director). The same information is fur- 

 nished to the position keeper, which uses the data 

 to track (dead reckon) the target. Target track 

 information is fed to the analyzer, which computes 

 target course and speed. 



Target motion data from the analyzer, and 

 target location information from the sonar, are 

 combined in the ballistic computer, whose output 

 is weapon control orders. To compensate for roll 

 and pitch motion of the ship, the stabilization 

 computer provides correction orders to the sonar 

 and to the weapon mounts. 



If sonar contact is lost, the position keeper 

 continues to provide target track information. 

 As long as the target does not change course or 

 speed during lost contact time, the resulting 

 weapon control orders will be valid. 



The latest shipboard underwater fire control 

 system is the Mk 114, which was designed for 

 use with ASROC. The system also can be used 

 with fixed and trainable hedgehog projectors, 

 DASH, and the Mk 43, Mk 44, and Mk 46 A/S 

 homing torpedoes. 



The Mk 53 attack console is the data pro- 

 cessing center for the system. It receives target 

 position information from sonar or radar and 

 combines it with own ship and ballistic data to 

 produce weapon orders. Aided tracking and posi- 

 tion keeping are also functions of the attack 

 console. 



Submarine System 



Torpedo fire control on the surface is rela- 

 tively simple. Wnen the submarine is submerged, 

 however firing torpedoes at a surface target 

 becomes complicated. When the target is another 

 submerged submarine, the fire control problem 

 is even more complicated. The equipment used 

 to solve the submariner's fire control problem 

 is the torpedo data computer (TDC). It is illus- 

 trated in figure 7-15. 



The TDC consists of three sections — position 

 keeper, receiver, and angle solver. Target infor- 

 mation from sonar (usually passive) is fed to 

 the receiver section, along with own course and 

 speed. Sonar bearing and target course and 

 speed are manually set into the position keeper. 

 The position keeper serves the same function 

 as its counterpart in the Mk 105 shipboard 

 system. The output of the position keeper is 

 sent to the angle solver section of the TDC, 

 which continuously computes the correct gyro 

 angle for the type of torpedo used. The TDC 

 then transmits this information to gjTO angle 

 indicator regulators located in the forward and 

 after torpedo rooms. The indicator regulators 

 automatically set the torpedo gyros to the ordered 

 position. If computed target information is cor- 

 rect, the torpedo, after being fired, will come 

 to the course set by the gyro angle indicator 

 regulator and proceed to hit the target. 



FIRE CONTROL SYSTEM TESTS 



Certain transmission, computing, and rate 

 tests must be performed in order to ascertain 

 that the fire control solution is correct, and 

 that values are received correctly at remote 

 stations. Also, frequent operation of a system 

 exercises servosystems, power drives, and com- 

 puting networks, thereby bringing attention to 

 any existing trouble. 



Transmission Tests 



Transmission tests are held to check the 

 accuracy of automatically controlled devices at 

 remote stations, and to check their response 

 to changing signals. When running these tests, 

 the first step is to establish voice communica- 

 tions between stations. Next, the man at the 

 transmitting station must read the exact output 

 value of the quantity being checked. In turn, the 

 man at the receiving station must adjust the 

 receiver to correspond to the reading from the 

 transmitting station. 



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