This color educational/training film is about how to make buoyant ascent in water. This is used to train submariners in making ascents from the 18-, 50-, and 100- foot levels. It was made in 1958 by the U.S. Navy.
Credits: Non Classified, the United States Navy presents Buoyant Ascent Buships 1-57, produced by US Naval Submarine base in Pearl Harbor (:07-:40). A buoyant ascent to escape a submarine. The explanation and the how to do such an ascent is explained and shown (:41-1:47). The British were the first to do this. In the fall of 1956 the USA started doing this. Pacific fleet is trained at Pearl Harbor and in the Atlantic at New London, CT. Pearl Harbor escape training tank is shown and explained, procedurally. Pressure is explained and shown how to deal with it. A doctor is on hand to check on the men, official logs are kept (1:48-4:52). The Buoyant ascent is an ascent where the diver is propelled towards the surface by positive buoyancy. After the pressure check the men leave the chamber and are shown a life jacket, the procedure is explained and then practiced in a mockup. Then the men move to the water (4:53-7:42). After a review of safety procedures, mistakes are corrected and the exercise is practiced. The men are first tested at an 18 foot level in a test tank. One testee among the trainers (7:42-9:58). After two successful 50 foot ascents, the trainee will move on. Practice ascents at 50 feet. If there is a problem, the trainee is put into a 25 foot bell for protection from an air embolism (9:58-11:58). After the two successful 50 foot attempts, the trainee can do the 100 foot attempt. The procedure is explained and shown. After all safety precautions, the 100 foot attempts can begin. What is required and how is explained and shown (11:58-14:17). An Admiral explains why this is good and how it works, successful attempts are shown (14:18-14:52). End credit (14:53-15:02).
Buoyant ascent is an ascent where the diver is propelled towards the surface by positive buoyancy. Generally recommended as a last resort, though a sufficiently skilled diver could control ascent rate by precise dumping from the BC and use this as a low energy alternative to a swimming ascent. In this case weights should not be ditched during the ascent.
Positive buoyancy may be established by inflation of the BC or dry suit, or by ditching weights. Buoyancy from added air can be controlled during ascent by dumping, but the effect of ditched weights is not reversible, and usually increases as the surface is approached, particularly if a thick wetsuit is worn. If weight can be ditched partially, this may be a better option, unless the diver feels that he is about to lose consciousness, in which case a substantial increase in buoyancy may be better.
A method of buoyancy control which will automatically jettison weights if the diver loses consciousness during the ascent is to take them off and hold them in a hand while surfacing. If the diver loses consciousness, the weights will drop and positive buoyancy will take the diver the rest of the way to the surface.
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