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<dmackay@cg*.wa*.ca*> writes: > ... Quite a few large aircraft, contrary to popular misconception, cannot > be flown without electronics. When crashes occur they often produce high > mortality rates. Does this stop you from flying? No. Why? The aviation > industry has done a marvellous job of reducing the risk of failure to an > acceptable level. The key here is acceptable level. A big part of achieving an acceptable level is that the electronics were replacing mechanical and/or hydraulic systems that were far from being perfect themselves. If you can achieve a reliability level as good as or better than what came before, you're doing alright. Going from OC, you're eliminating the rapidity with which one can exhaust a gas supply (minutes become hours), and reducing the level of regulator demand that leads to freeflow situations in colder water. Both of those have led to fatalities in the past. That buys you a bit of manouvering room. However, another relevant area to consider is electronic pressure gauges. Like probably almost every other technical diver, I've been leery of these things, but a bit of analysis indicates they could potentially be safer even without being more reliable than analog gauges. As I see it, there are three possible failure modes: A) something can burst open and lose gas. Analog gauges require a flexible HP hose, and it's more a question of when rather than if these fail. Anything that requires you to shut down a post is taking away a huge chunk of safety margin. A digital transducer tucked away under a first stage on your back should be much less susceptible to such failures. B) analog needles stick, and you could overswim thirds or otherwise get a false reading and base a wrong decision on it. This is a second failure mode that could try to kill you. Even George says he had one stick on him due to external pressure 18,000 feet back, and he uses the best. I'm not certain how well digital transducers stack up in this area, though. Does anyone have any evidence of them giving false readings? C) simply failing to give any reading at all is the more likely failure mode of electronics: something floods, or a battery dies, and the display goes blank. Assuming you've been looking at it frequently enough, though, you can't be past thirds at this point and you can safely turn the dive without having to know how much you actually have going out. Meanwhile, analog gauges give no reading in no-viz situations; having an electronic "heads-up" display in your mask could solve that. So my point is that electronics don't have to be perfect, they just have to be less likely to try to kill you than the systems they're proposing to replace. I have no evidence that any particular systems have actually reached that point, but I'll keep my ears open. -- Anthony DeBoer <adb@on*.ca*> -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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