an appropriate hydrophone, the support 

 craft may also determine the submersible's 

 bearing relative to itself and may elect to lay 

 off from the vehicle rather than stay directly 

 overhead. 



Transponder: 



Attached to the submersible's topside, the 

 transponder is an automated receiver/trans- 

 mitter which transmits an acoustic signal 

 when interrogated by the surface craft. By 

 accurately timing the interval between the 

 outgoing and incoming signals, the 2-way 

 slant range between support ship and sub- 

 mersible can be computed, and, by knowing 

 the submersible's depth, the horizontal dis- 

 tance from one to the other may be derived. 

 By increasing or decreasing this distance, 

 the support craft can maintain its desired 

 position relative to the submersible. 



Underwater Telephone: 



The submersible's underwater telephone 

 can function as a transponder when a 

 "mark" signal from the surface is answered 

 by "mark" from the submersible. By timing 

 the interval between the surface mark and 

 sub-surface return mark the slant range is 

 calculated. Similarly, by transmitting peri- 

 odic impulses the telephone may function as 

 a pinger. 



Buoys: 



The towing of a surface buoy has been 

 discussed previously. It is sufficient to note 

 that some shallow vehicles are tracked from 

 the surface by towing a surface float. 



EMERGENCY CORRECTIVE 

 SYSTEMS (SUBMERGED) 



In the event of a submerged emergency, 

 the operator may have several options. The 

 nature of different emergencies and the var- 

 ious options are shown in Table 14.3 and 

 discussed below. 



Loss of Normal Surfacing Ability 



Submersibles surface through a variety of 

 procedures: They may power up, drop 

 weights or blow ballast. In the event that 

 none of the normal procedures operate, other 

 options are available to the occupants for 



regaining the surface either with or without 

 the submersible. 



Weight Drop: 



The most widespread emergency surfacing 

 procedure is the dropping of a lead or steel 

 weight attached to the submersible's keel 

 (Fig. 14.4). Depending on the submersible, 



Fig. 14.4 The200-lb lead weight (lop) on Sf/< OTTOTs keel is manually dropped by 



a "T" bar wrench (bottom) from in the hull. Both ends of the weight are recessed and 



indexed into the keel to assure it will not rotate while being unscrewed 



659 



