Checking YBOD handsets

[PrettyFishies]

Some good responses, constructive debates.

Everyone has their own particular "hot buttons" about which risks are acceptable and which aspects require redundancy be it in whatever form.

Underpinning all of the kit rigging and add ons and bells and whistles is the realisation for me, that while all these things add a little feel good comfort factor, I never slump into the complacent mindset that they mean nothing will ever happen or go wrong.

Regardless of any add on systems monitoring handsets, I would still look at the handsets. Even if they're clipped in, it takes 1 second to lift a handset and take a quick look. This is one of the basics of diving any rebreather, know your PO2. It doesn't take a lot of discipline to make it a habit. I find it incredible how many RB divers do a whole dive without looking at the handsets. This is the mentality of waiting for something to happen, like a warning beep, or on non-alarm systems, a problem, rather than checking the handsets and giving yourself more time to respond to a problem.

Regards

AnneMarie

[Drmike]

Personally I think the best way to dive any rebreather is manually with the controller on a lower setpoint.

That way a diver becomes instinctively familiar with how the ppo2 changes during different stages of a dive or different situations and how to maintain it. After a while you know, you feel, instinctively when you need to inject a little O2, or when and how much its going to spike on descent, or drop on ascent

It takes practice but when you get there you are a far safer rb diver IMO. If you only ever dive following the controller its hard to develop an understanding of ppo2 reaction

To help develop this skill and habit Ive always run my units manually on every third dive. I have the setpoint lower and inject manually with min loop.

After a while it becomes so natural running manually that there is no sense of task loading or detraction from the enjoyment of the dive. I check my handsets very often - i find it reasuring

Personally I see good reliable controllers with huds, alarms etc as a double edged sword. To me they should be back up to the brain and not the other way around. Dont get me wrong I use them and I use a HUD but I certainly dont rely on them

In my book if Im alerted to a problem by the HUD or by an audible alarm then Ive failed as an rb pilot. I should have seen the problem develop long before on the handset(s)/secondary.

[uri]

Originally Posted by AnneMarie

Hi AnneMarie

I have watched multiple independent circuits fail, both on land and underwater. I have seen large networks crash and then watched the disaster recovery sites also fail. Redundant systems are not fool proof.

All failures have mechanisms. Complex systems have failure mechanisms that are too complex to model and hence are not usually specified as failsafe. Your examples above are good ones of that.

Simple systems are much easier to specify and their failure modes if simple enough can be shown to failsafe if designed as such. I don't believe in gremlins, I'm an engineer and I know that electronics can fail but I also know that the odds against independent triplicated systems failing in a non-safe mode are much much much higher than any of the other risks we all take daily with our lives such as crossing roads. Without a known failure mechanism to cause such a failure, how can it happen?

Don't get me wrong, I'm not slating the idea of a HUD at all. I am merely pointing out that my own personal experience has proven to me that even multiple systems CAN fail and therefore it is important to continue checking your own handsets instead of becoming complacent because you have another system checking the handsets.

Handset checking is there because suppliers haven't made reliable enough/failsafe equipment and put the onus on the user to make up for it. Handset checking is archaic if unnecessary. I accept that a rebreather is a complex system that is hard to show to be failsafe but rebreather monitoring is a simple system that is much easier to show to be failsafe.

PS - regarding mechanisms of failure, there was a recent episode where a diver had a problem with the mushroom valves and CO2 was coming back through the loop. He was hammered with CO2 and had an epic getting off the loop at depth only to find that his VR3 was failing to show deco info. That is a mechanical failure of one system and an electronic failure of another. My argument does not need to be rational because underwater irrational things happen. Shit happens. I prefer to base my logic on experience rather than "what if" scenarios.

I believe that reduction in task loading and removing the need for a diver to have to remember to keep themselves alive by gauge monitoring as well as getting advance warning of pp02 problems developing have a great contribution to safety, liberation and dive enjoyment and will contribute to avoiding shit happening and getting around it if it does happen in the first place.

No one is slating the HUD here or the concept but it IS important to be aware of your PPO2 at all times.

Agreed, isn't that what a HUD actually buys over a gauge?

To me, this is the cornerstone of diving the unit. Also, being relaxed on the unit is great but complacency kills. It can bite when you least expect it. I still have a very healthy respect for the YBOD.

I too have a healthy respect for mine but I designed the HUD to get around what I saw as its (and most other rebreathers') fundamental weakness and I have had no one yet question the basis for that safety with any reason one can have a sensible discussion about and unfortunately, shit happens is one of them.

Regards

Uri

[Drmike]

Im sorry Uri but I couldnt disagree more with some of what youve said above.

Huds have their place as do controllers but as soon as you start relying on them 100% your days are numbered.

Pilots may fly by wire but they still have manual charts and do checks and can overide

[uri]

Modern fighters are totally unstable in flight and can only be flown with computer support.

[Drmike]

Originally Posted by uri

Modern fighters are totally unstable in flight and can only be flown with computer support.

Exactly. I was reffering to comercial planes that can be.

Lot of dead fighter pilots when their comps do a wobbly

[Decodiver]

Originally Posted by uri

Handset checking is there because suppliers haven't made reliable enough/failsafe equipment and put the onus on the user to make up for it. Handset checking is archaic if unnecessary. I accept that a rebreather is a complex system that is hard to show to be failsafe but rebreather monitoring is a simple system that is much easier to show to be failsafe.

I believe that reduction in task loading and removing the need for a diver to have to remember to keep themselves alive by gauge monitoring as well as getting advance warning of pp02 problems developing have a great contribution to safety, liberation and dive enjoyment and will contribute to avoiding shit happening and getting around it if it does happen in the first place.

Hi Uri,

That is where you and I will agree to differ. I do not see controller checking as task loading and those that do should consider their suitability for CCR diving. I think back to when there was no ADV and we would video on the unit and be like an underwater accordion player.

You definately have the right to your opinions but I am worried by making things so easy and turning CCR diving into a no brainer. If people find remembering to check gauges difficult then they should go knitting.

Just my thoughts.

Dave

[BJ]

Originally Posted by Decodiver

If people find remembering to check gauges difficult then they should go knitting.

Just my thoughts.

Dave

http://www.divernet.com/travel/cocos0300.htm (last part!)

[Decodiver]

If memory serves me right he hadn't even done a proper course!!

This shows the need for disciplined divers on CCR.

[BJ]

Originally Posted by Decodiver

If memory serves me right he hadn't even done a proper course!!

I did the same course Martin Parker and Mike Etheridge did.