not begin operating until it is dropped. To 

 drop the pinger the solenoid is energized; 

 this draws the plunger into it and causes the 

 latch arm to move about the pivot. The 

 movement of the latch arm draws out the 

 latch pin and releases the pinger. The coiled 

 spring assists in releasing the pinger. No 

 electrical power is required to hold the pin- 

 ger, only to release it. 



For quick deployment of a pinger from the 

 surface, WHOI developed the free-fall bottom 



Fig, 10.29 Tn-plane steel acoustic reflector- (WHOI) 



ji^Ji RELEASE MECHANISM 



LATCH PIN i-v J 



used experimentally (23) and the flashing 

 light was clearly visible at 310 feet with 

 ALVIWs lights off and dimly visible at 175 

 feet with lights on. 



Virtually anything that will reflect sound 

 sufficiently to produce a return with a favor- 

 able signal-to-noise ratio will serve as a pas- 

 sive marker. In a 1969 search for an air- 

 craft's flight data recorder package at 350 

 feet deep, the tail section of the crashed 

 plane was used as a central navigation 

 marker for DEEP QUEST's search of the 

 area as well as a point on which the vehicle 

 homed from the surface to commence the 

 search (31). 



Fingers — Acoustic pingers can be dropped 

 by the submersible or the surface ship. In 

 the former case, it would serve to mark a 

 specific point on a survey (or search) line to 

 which the vehicle would return and continue 

 the survey, or it might mark the location of 

 an object to which the vehicle would return 

 for retrieval. Figure 10.30 shows a solenoid- 

 actuated pinger release mechanism and a 37- 

 kHz salt-water activated pinger which will 



PINGER 



Fig. 10,30 A "salt-water" activated pinger and solenoid release mechanism on 

 ALVIN. (WHOI) 



515 



