Navy Dive Tables

[bc214]

Hello All.

I was ordering a few items from Dive Gear Express, and noticed that they had Navy Air Dive Tables (And deco tables on the back). Being that I hear lots of people carry these with them in place of their specific tables, and that all of the name brand tables are basically "born" from the Navy data, I ordered up a set to check it out.

I have my training from SSI and understand that each brand of training is a little different, but now I look at the cards and see some differences on how to work through them. Also, the decompression table on the back is greek to me.

Does anyone have a link perhaps to a video explaining the "US Navy Air Dive tables" and/or the decompression tables? I would like to get an idea of where the tables originated, and a basic idea of how the decompression table is set up.

Anyway, it's not a pressing matter, I'm just curious in the differences between the SSI tables and the US Navy tables, and also about the deco side of the card.

Thanks,
-BC

 

[redacted]

A little light reading: http://docs.lib.noaa.gov/noaa_docum.../SEALAB/us_navy_diving_manual_rev5 Part 1.pdf

 

[Doc]

The USN Tables (chapter 9, page 437 in the 12# manual) were assembled by trial and error. They work perfectly on squared dive profiles, typical of commercial divers who go down quickly, work at one specific depth for a duration (truly a "bottom time"), then ascend.

They work really well, for a perfect specimen of a 20 year old male with 2% body fat.

Commercial training agency dive tables were not signed-off on by a Master Chief, they were given final approval by attorneys.

 

[Basking Ridge Diver]

Here is some information I have used as resources in the past -
Not pertaining to Navy Tables but overall good information sources.

Decompression Theory | Links and Resources | Technical Scuba Diving

TUTORIAL: Use of Decompression Dive Tables

Good luck with your search.

 

[LeadTurn_SD]

PSDiver.com

Revision 6 of the USN Dive manual in pdf form is available on the page linked above I believe.

I "grew up" using the USN Dive Tables in the 1970's and 1980's, including staged deco dives. I have no formal "tech" certifications since those really did not exist back then.

I was "mentored" by an ex-USN Navy diver. He was emphatic about never "pushing the envelope" of the USN tables, at least in those days, for the same reason Doc alludes to: You could get bent, even following the Tables.

There are better alternatives these days (tables generated on your PC; the V-Planner software is a popular example).

But most importantly training is widely available these days.

Don't use the USN tables unless you fully understand how to use them.

Best wishes.

 

[Akimbo]

The USN Tables (chapter 9, page 437 in the 12# manual) were assembled by trial and error...

That is a bit of an overstatement. The first USN tables in 1916 were based on Haldane’s work in the UK. Yes, slide rules were involved from the beginning. Like Haldane’s tables in the UK, there was still a great deal to learn.

A lot of stories make it sound like a bunch of sailors sat around and said “well, he got bent on that one so add decompression next time” — not true. The USN Experimental Diving Unit in Washington DC did a great deal of work refining tables based on tissue algorithms and verified by human testing supervised by diving medical officers. Statistics compiled from the fleet further refined tables and modified the tissue theory. All that experience fed back into refining the algorithms.

Even the first saturation diving decompression tables were developed by Dr. Mazzone on a slide rule in the late 1950s.

Today’s US and Royal Navy tables are based on tissue theory and algorithms as modern as any in our dive computers. Recreational training agencies and their attorneys don’t know squat about decompression theory. All they care about is that their tables are defendable in court.

Edit: You can download the entire Navy manual from Scubaboard:
US Navy Diving Manual Rev. 6 with Change A

---------- Post added September 4th, 2014 at 04:55 PM ----------

…I was "mentored" by an ex-USN Navy diver. He was emphatic about never "pushing the envelope" of the USN tables, at least in those days, for the same reason Doc alludes to: You could get bent, even following the Tables...

How is that different now? People get bent all the time following their computers.

 

[Nemrod]

Can anyone provide a (link or reference) peer reviewed study that compares bends incidence of sport divers using tables vs computers or pre-computer vs. post computer?

While we are at it, of bends incidence using the exact same dive profile but with and without the "safety" stop?

N

 

[Akimbo]

Can anyone provide a (link or reference) peer reviewed study that compares bends incidence of sport divers using tables vs computers or pre-computer vs. post computer?...

That has been a problem since the advent of recreational diving. Navy and commercial surface supplied divers could supply vary accurate dive profiles because there was a diving supervisor with a pneumo-fathometer and a stop watch. The world navies not only have precise dive profiles but also the total number of dives.

The total number of dives is a still a major WAG in recreational diving, but at least we are now getting accurate profiles from divers that get treated for DCS thanks to computers.

 

[LeadTurn_SD]

.... How is that different now? People get bent all the time following their computers.

Yep. Point well taken.

It isn't any different really, but my memory of the instruction I received from my mentor as I moved into "lite" deco diving was that flirting with the limits of the Navy tables invited a "hit", even if you remained on the happy side of the NDL's. He urged all of us not to test the table limits in any way shape or form.

And yes, the exact same thing can be said with "riding the limits" on a computer today. But my point was that in most (many??) cases, recreational tables and computers have generally become a bit more conservative over the past 30 years for a single square profile dive.

We (you, I, Nemrod, and others "of a certain age") were likely taught "Sixty for sixty" (60 feet deep for 60 minutes, with an ascent rate of no faster than 60 feet per minute). Sixty for sixty and "120" were memory aids for NDL's on a single dive... "60 for 60, 70 for 50, 80 for 40, 90 for 30".... all equal "120", and all were the NDL's in the tables, and worked well for single dives.

Today those depth and time combo's might trigger your computer (or dive table) to scold you, but I believe the Navy and NOAA say they're are still "ok"? Which means they are probably still "ok", but a bit less conservative than other dive tables?

Best wishes.

 

[Nemrod]

That has been a problem since the advent of recreational diving. Navy and commercial surface supplied divers could supply vary accurate dive profiles because there was a diving supervisor with a pneumo-fathometer and a stop watch. The world navies not only have precise dive profiles but also the total number of dives.

The total number of dives is a still a major WAG in recreational diving, but at least we are now getting accurate profiles from divers that get treated for DCS thanks to computers.

I want to know, has the incidence of bends increased, decreased or remained unchanged per X number of dives, computer vs. tables and before and after the advent of computers? Not anecdotal opinions or supposings but peer reviewed studies/data. Hard to get to truth because one must dig through layers of BS and the diving equivalent of urban legend.

N