4,000 feet deep and maneuvering around to 

 place the corer, about 100 pounds of silt were 

 picked up in the fairing cavities. The hy- 

 draulic system failed due to mechanical sei- 

 zure of a face seal and the mercury trim 

 system could not transfer mercury forward 

 to drive in the corer tubes. It was decided to 

 abort the mission and surface. The following 

 events occurred: a) The 186-pound ascent 

 weight could not be released hydraulically 

 and the manual backup release was initi- 

 ated. The weight hung up in its housing and 

 did not drop, b) The small trim weights 

 (about 150-lb capacity) could not be dropped 

 due to the lack of hydraulic power, c) The 

 mercury of the trim system (200 lb) was 

 released using the nitrogen blow system but 

 the vehicle was still heavy, d) In an unre- 

 lated situation, the variable ballast bottles 

 had flooded (80 lb) due to faulty silver brazed 

 piping joints. Weight resources available in- 

 cluded the vehicle brow with its scientific 

 instrument suite (70 lb) and the forward 

 battery (450 lb). Since the exact weight sta- 

 tus of the vehicle was not known at the time, 

 the forward battery was dropped (450 lb) and 

 the vehicle ascended. The up trim angle of 

 the vehicle also shook out the ascent weight. 

 A rapid, safe ascent was made. 



Submersible: PISCES III Date: 1971 Ref- 

 erence (4) 



Incident: During a dive at approxi- 

 mately 600 feet deep, PISCES III experi- 

 enced difficulty in attaining level trim. A 

 check of the emergency warning systems 

 revealed that the aft machinery sphere was 

 flooded. Main ballast tanks were blown but 

 the vehicle merely came to a near-vertical, 

 bow-up position and remained stern-first in 

 the bottom. The Canadian Defense Minis- 

 try's SDL-1 was undergoing sea trials at the 

 same time and at the same location, and 

 carried down a lift line which it attached to 

 PISCES Ill's port motor guard. Some 8 

 hours later the vehicle was winched to the 

 surface. A postmortem revealed that drain 

 plugs in the machinery's sphere were left 

 open during the dive and allowed seawater 

 to enter and flood the sphere. 



Entanglement 



Submersible: DEEP QUEST Date: October 



1969 Reference (1) 



Incident: While conducting a recovery 

 test in 430 feet of water, DEEP QUEST 

 became entangled with a "/g-inch polypropyl- 

 ene line. The line was caught in the port 

 propeller of the vehicle and anchored the 

 submersible to the test object. The submers- 

 ible NEKTON was transported to the scene 

 and, attaching a diver's knife to its manipu- 

 lator, cut DEEP QUEST free. At any time 

 during its entanglement DEEP QUEST had 

 the capability of dropping its batteries which 

 would have brought both the vehicle and its 

 "anchor" to the surface. 



Submersible: JOHNSON SEA LINK Date: 



17 June 1973 Reference (5) 



Incident: Attempting to retrieve a fish 

 trap at 360 feet deep, the submersible be- 

 came entangled in the rigging of a scuttled 

 destroyer. Divers tried to extricate the vehi- 

 cle, but strong currents resisted their efforts. 

 The submersible PCS tried to assist but its 

 obstacle avoidance sonar failed and it was 

 ordered to discontinue efforts. Approxi- 

 mately 32V2 hours later a device holding a 

 television and a grapnel was lowered to the 

 submersible and conned into its final ap- 

 proaches by the submersible's operator using 

 the underwater telephone. The device was 

 hooked onto the JOHNSON SEA LINK and 

 she was jerked free. Two occupants in the 

 aluminum lock-out cylinder perished. The two 

 occupants of the acrylic plastic forward 

 sphere survived. Cause of death was ascribed 

 to carbon dioxide poisoning when the carbon 

 dioxide scrubbing compound (Baralyme) lost 

 its effectiveness due to low temperature 

 (about 40°F) in the cylinder. 



Submersible: PISCES III Date: 29 August 



1973 Reference (6) 



688 



