Air integrated computer and tec diving

[packrat12]

DevonDiver and Nasser - Both of you have yet to understand my statements. DevonDiver you even directly quoted on your last post what I have stated from the beginning and the point in ALL of my posts on this thread. Given a dive plan and computer, the computer WILL have the more accurate representation of the actual dive profile. It is that simple. All of the other points you stated has not ever been disagreed with. I have from post 1 called the dive profile in control of the actual dive, limits of Max Depth and Max time. On ascent, Deco obligations become the controlling factor. How you arrive at your decompression schedule (dive plan/computer) is up to you but it still is the controlling factor! Try surfacing with out meeting them to tell me if they are in control or not...

If I ascend early without a planned contingency, the dive plan is by default IS obsolete. It still may be a backup if the computer fails but will NOT AT ALL resemble the actual dive profile once on the surface! Since the dive plan does not match the computer, it is also obsolescent during the ascent phase. It still may be used as a backup if the computer fails but you cannot do anything about short comings such as gas supply (ignoring team assistance here). Only if the computer fails does a diver need to fall back to it.

Neither of you seem to have grasped the concept that when the ascent begins, the planned dive profile WILL be different then the actual profile and the computer WILL have the more accurate representation of the dive. Because we have not exceeded either the max depth or the max time, the deco obligations will almost always either match the dive profile or be less then the dive profile. If not, the dive plan during the dive phase was not followed. The dive plan does not control the ascent and if it was not followed, it also is inaccurate.

Now, I do not dive nor advocate but there are significant number of technical dives with deco safely done without pre-plans or dive plans. The same factor is in control of their ascent - Deco obligations. Same for recreational diving without plans, except the deco ceiling is the surface. Yes gas supply is a consideration but if you have it, it is not in control.

Not once in any post have I commented on what good contingencies are, what constitutes good gas planning etc. It is beyond my original scope in the statement made to DevonDiver that the computer has the most accurate representation of the actual dive profile.

Whether or not you choose to accept the 2 statements I have repetitively made is up to you but the fact is:

1. Deco Obligations are the controlling factor in your ascent absent any other higher priority issue.
2. The functional dive computer will have the closest actual representation of your dive profile.

And as an aside, around here I have yet to see an actual dive match the pre-planned profile, especially on wrecks!

As for too much deco - I agree and do generally stay down longer then my computer but you should pad your last stop (computer) or your dive profile deco schedule after the fact. So a profile plan with a RT of 60, I might stay around for +5 so 65. My deco schedule still will have a RT of 60. My computer says that deco is complete, I may stay around +5. That still does not mean the the deco schedule from the dive profile is more accurate. If I am advocating padding my computer then I must also advocate padding my dive profile generated deco schedule.

 

[DevonDiver]

John, isn't this just a case of training? I keep mentioning precision.

1. Most bottom timers display max depth. If our planned bottom depth is 45m... I brief students that I don't expect to see anything deeper on their log afterwards. Focus the mind on it. If they venture deeper (and, as you say, we don't know really how long for), then they apply their 'just deeper' contingency.

2. Ascent rates need to be trained. It takes demonstration and practice. I do this extensively. 9m per minute is much faster than most (rec) divers are accustomed to. Students tend to be slow... It has to be corrected. If a qualified tech diver is too slow, they weren't adequately trained. The good thing about runtime is that you can immediately see you're running behind. If that happens before the first stop then it's a 'delay in ascent'... and there's a standard protocol to apply for that contingency too.

3. Following a runtime provides its own motivation - it gets more complicated if you drop off a runtime and have to ascend on timed stops instead. I use that motivation, because students have to apply contingency procedures if they fail to dive the plan.... exceed depth, bottom time, ascent speed errors etc.

Knowing... and applying... those contingencies is a good lesson you only get from diving tables.... not from a computer that silently does all the contingency recalculation for you.

Once you've learned / dived on tables you appreciate what's happening when you fail to 'dive the plan'. You know you've dropped into a contingency situation... a 'no-no'.

If all you learn is to dive a computer, you only appreciate that your convenient device juggled some numbers. It doesn't look, or feel, like something actually 'went wrong'. Thus we have an insidious normalisation of deviance of the highest order...

Personally, I enjoy the 'art' of technical diving. You don't get that feeling diving a computer... it strips away that fine element of satisfaction.... of striving for perfection. But that's just me..

 

[boulderjohn]

John, isn't this just a case of training? I keep mentioning precision.

All people perform better with training, but further training does not bring on perfection. All of the people I just described had quite a bit of training before making the errors I noted.

In almost all of my decompression instruction, we follow a written plan with contingencies. We always have computers along for backup. When I am in a situation where we all have compatible computers, we will also do dives following the computers, with the written plans as backup. Whatever we do, though, we will have a computer along, if only for a reality check.

BTW, it is my observation that most people who say they are following the written plan with the computer as a backup will almost always tweak their deco stops to match the computer, which to me means they are actually diving the computer with the written plan as a backup.

 

[Centrals]

BTW, it is my observation that most people who say they are following the written plan with the computer as a backup will almost always tweak their deco stops to match the computer, which to me means they are actually diving the computer with the written plan as a backup.

Pretty correct observation and I resent that if we are diving as a group. The "written plan" is the ONLY plan, all the rest is the back up unless there is emergency.