Nitrox Class Without Tables or Math...OK?

[Swan1172]

Here we go again with changing the scope of the argument because you cannot support your initial argument.

if your AI computer breaks the same thing happens as if your SPG breaks, only I would argue it can be easier to tell that your AI computer broke because it would likely display something clearly erroneous (or not display anything at all) while a SPG could "stick" at a given pressure thereby making you believe you have more air than you really do.

If you have no idea how deep you are or how long you have been down, you have not: a) been diving with a buddy, b) been monitoring your depth and time AT ALL, and c) been following safe practices for diving with a computer or with tables.

First of all, I am not changing the scope of the argument because we are talking about the importance of contingency planning for a computer failure. As I said before, every dive computer manufacturer tells you explicity to have some kind of back-up instrumentation available in case of a failure. The most common kind of back-up for a computer is tables, an SPG and a timing device. If you don't know how to use the tables, you are SOL, which is one of the reasons I have a problem with classes that only teach you to use a computer. I think you need to teach both.

Also, there are an awful lot of people that trust the computer to beep to tell them what to do. They don't actively monitor their computer during their dive, but rather use it like auto pilot. Look at the number of people who have out-of-air problems because they forget to look at their SPG. It is exactly the same thing.

 

[MikeFerrara]

ok...

AND

you guys talk about computers as though they spontanously break down
every other dive. i have been diving for six years and i am yet to see
a computer malfunction, either mine or a buddy's. yes it could happen,
but it's a rather remote possibility. and if it DOES happen, your awareness
of your plan (70 feet for 40 minutes) should get you out ok.

methinks you exagerate the "risks" of diving with a computer and not knowing
math or the tables.

I've seen quit a few computer failures. I've seen more in cold conditions that warm and the most common failure was that they just didn't work at all but some of those failures were mid-dive wich still isn't very dangerous on most recreational dives...you just go home. For a long time, when I was diving with computer I wouldn't use anything but one of the single button models because they always seemed to work and I knew so many people who showed up for our winter dives with their fancy new computers only to find out that they didn't work. Maybe the newer models are more reliable but this wasn't too many years ago. At least we always had plenty of pewople to tend the fire and take care of the cooking.LOL

As I mentioned before I've seen quit a few display incorrect depths and most of those failures were intermittant. The first time I saw that was in a pool. The alrgest error I've seen was almost 20 ft...which might get you in trouble if you don't catch it.

I had a Zeagle computer that kept going into surface mode during dives. Sometimes it would just stay in surface mode when you got in the water which was just a pain but several times it switched from dive mode to surface mode during the dive.

I can't say that I've ever seen a computer display the wrong PPO2 but on the nitrox computers I've had the PPO2 display is way too small and fine for me to read very easily anyway especially underwater.

 

[Kim]

I have had my Suunto Vyper fail on me once. It made a complete reset (wiped out dates and everything!) half way through my dive. I continued using my Casio dive watch (displays depth and time) which I wear on my other wrist.

 

[DivesWithTurtles]

And they call "us" clowns! Sheeesh!

Tech divers, do you carry redundant fins? You're up the creek if your fins break? What's your sanity check to know if your fins are moving you at the correct speed to get you out of that overhead environment at the right time?

Actually, I see and understand the need for redundancy and extreme reliability for your type of diving. You are performing technical dives that have stringent requirements to keep you reasonably safe. I am doing rec dives that are inherently multitudes safer than what you do. You seem to be totally blind to my type of diving.

BTW, in my very limited personal experience, I have seen more SPGs stick (3) than I have seen computers fail (1). And when that computer failed, it displayed all 9s. I guess I needed to know an approximation of my deco status (NDL, not staged) to know that it wasn't telling the truth.

 

[Swan1172]

Uwatec had a problem a few years back with its Aladin Air X Nitrox computer performing improper calculations. A lawsuit was filed by four divers who claimed that they suffered bends as a result of using Uwatec's 1995 Aladin Air X Nitrox. The divers, led by Robert Raimo - a former Uwatec distributor, claimed that a fault on the computer meant that surface intervals were credited as if the diver was breathing the mix of nitrox used on their first dive while on the surface. This led to an underestimation of decompression obligations for repetitive dives, and, they claim, resulted in their decompression injuries. From what I can tell, the lawsuit was settled in early 2005.

 

[Dragon2115]

Andy,

We're just going to have to disagree. I feel that the students aren't being done a service by not being taught the math equations that go along the course.

One of the things I realized shortly after getting certified was just how lacking the OW class, and AOW for that matter, can be. I feel that we are involved in a sport that has serious consequences for error and therefore divers should be capable of thinking rather than just performing a task by rote. Understanding the equations gives an understanding of the relationships and how changes in one variable will effect the rest of the equation. Without that understanding the class is producing divers that are incapable of doing that.

Btw, I'm on my third Oceanic ProPlus2 in just under a year. And that's why I also have an analog SPG and depth gauge with me at all times.

 

[limeyx]

And they call "us" clowns! Sheeesh!

Tech divers, do you carry redundant fins? You're up the creek if your fins break? What's your sanity check to know if your fins are moving you at the correct speed to get you out of that overhead environment at the right time?

Actually, I see and understand the need for redundancy and extreme reliability for your type of diving. You are performing technical dives that have stringent requirements to keep you reasonably safe. I am doing rec dives that are inherently multitudes safer than what you do. You seem to be totally blind to my type of diving.

BTW, in my very limited personal experience, I have seen more SPGs stick (3) than I have seen computers fail (1). And when that computer failed, it displayed all 9s. I guess I needed to know an approximation of my deco status (NDL, not staged) to know that it wasn't telling the truth.

SPG sticking is not a huge problem though. Since you know your SAC rate, you can calculate how many PSI you expect to breathe every 5 mins at the depth of your dive.

So you check your SPG every 5 mins (or whatever interval you choose). If the gauge hasn't changed in the last couple of times you looked, you know something is up.

Also, after a while of diving, you know what the gauge ought to read, and if it's off, you can tell.

Besides, part of dive planning is reserving enough gas to get two divers out of the dive (be it Open water rec dive, tech dive or cave dive) if one person loses their primary gas source, right?

So again, you should be "OK" in that case.

Same again with the computer -- some people carry two bottom timers. Also your buddy(s) have their own, so you can ask your buddy to take over leading the dive and exit. Pretty easy.

 

[Jason B]

As for computer malfunctions, I wish all of your home computers would malfunction so this crap can end.

 

[H2Andy]

As for computer malfunctions, I wish all of your home computers would malfunction so this crap can end.

:lol:

 

[JHodgeCMI]

Well PADI told me that their Online Nitrox course test does not have ANY dive planning questions...