Fig. 14.3 ALUMINAUTs CTFM sonar traces ot a box canyon al 800 leet deep oft 

 Vieques Island. Puerto Rico (NAVOCEANO) 



odic intervals. No reported emergencies have 

 evolved through this procedure in the his- 

 tory of submersible diving. Most submers- 

 ibles do not dive for much longer than 8 

 hours, which may account for this high 

 safety record. On long duration dives, e.g., 

 BEN franklin's 30-day Gulf Stream Drift, 

 automatic monitoring and warning devices 

 may be more advantageous in view of opera- 

 tor fatigue or involvement with other duties. 

 Included within the life support monitoring 

 devices on several submersibles are those 

 which measure internal pressure and trace 

 contaminants. An aircraft altimeter or ba- 

 rometer is quite often used to serve the first 

 function, and portable testing kits are avail- 

 able to measure trace contaminants. 



Surface Traffic and Inclement 

 Weather 



It is impossible for the submersible's pilot 

 to assess surface traffic conditions prior to 

 surfacing. In the open sea the chance of 

 surfacing under or within the path of an 

 oncoming vessel is quite slim, but in water- 

 ways or coastal traffic lanes it is considera- 

 ble. While an upward viewing capability in 

 the submersible might exist, it is not always 

 possible to stop the submersible during as- 

 cent and lack of water clarity might preclude 



visual observations. Surface weather condi- 

 tions can deteriorate during a 6- to 8-hour 

 dive and generate a sea state in excess of 

 that considered safe for retrieval. Some 

 ocean areas, the Santa Barbara Channel for 

 example, are subject to rapid weather 

 changes which can close in on a dive site 

 with little advance notice. The only safe- 

 guard against both potential hazards (traffic 

 and sea state) is a surface tending craft 

 capable of communication with the submers- 

 ible. As a general operating procedure, the 

 surface vessel has the ultimate control re- 

 garding safe and timely surfacing. Though 

 the likelihood of collision with a military 

 submarine or another submersible is slim, 

 communication between two underwater ve- 

 hicles may be carried out providing the fre- 

 quencies of both telephones are the same. 

 There is no standard frequency for underwa- 

 ter telephones, and they have ranged from 8 

 kHz to 100 kHz. Purely by chance, 8.0875 kHz 

 is found on a great number of vehicles. This 

 is the frequency selected for the first Naval 

 underwater telephone and designated as AN/ 

 UQC and is used on U.S. Navy submarines. 

 The reason for the choice of 8 kHz on small 

 submersibles is simply that it was all that 

 was commercially available in the fifties and 

 early sixties. Now, a number of different 

 models and frequencies are available and 

 can be found on various submersibles. From 

 a safety/rescue point of view, it is advisable 

 that the operator includes a carrier fre- 

 quency of 8.0875 kHz because it is compatible 

 with the majority of his sister vehicles and 

 all U.S. Naval potential rescuers. 



Separation From Surface Ship 



For a number of reasons (retrieval, surfac- 

 ing, rescue) the surface support craft must 

 know the submersible's position relative to 

 itself. Several methods are available and are 

 discussed at length in Chapter 10. 



Fingers: 



Self-powered acoustic pingers may be 

 mounted on top of the vehicle which emit an 

 acoustic impulse every 2 seconds or less. 

 With a frequency compatible listening device 

 (hydrophone) the surface ship stays over the 

 submersible during its dive by assessing the 

 strength of the incoming signal. By carrying 



658 



