Scuba 'no fly time'

[kokomo]

Please help me explain the 'no fly time'

What have i missed when Im flying commercial air lines and the cabbin is pressurised to 1 ATM? how can bubbles form?

why do all the books suggest waiting 12 hours+

cheers..

 

[trux]

Cabines of planes flying above 3500m are typically pressurized to 0.75 bar. Cabins of smaller planes, often flying to smaller airports at diving destinations, may not be pressurized at all (though they do not ascend so high). And then you also have the risk of depressurization, where it would probably cause serious troubles even to a diver past his no-fly time - much worse than to the other passengers.

 

[kokomo]

Thanks Trux..

so whats the Maths behind it..... is 12 hours just a generic very conservative guide...

are there a list of tables or dive computers that will give a more reasonable no fly time? assuming 0.75ATM

 

[trux]

You need to desaturize pretty well before flying. Sure, the time is probably rahter conservative, probably taking in view multiple pressure changes (when leaving the diving destination, you often take a small island hopper plane, where the changes of altitude and pressure may be quite a few and quite quick) and/or possible partial depressurizing of the cabin in a bigger plane (which indeed happens).

12 hours after a short shallow dive is pretty standard. If you need leaving quicker, you may breathe oxygen for some period of time when on surface. DAN recommends 24 hours no-fly time even for single short dives, so in your place I would really not try reducing the time, unless urgently necessary

DAN (Diver's Alert Network) has revised their recommendation to the 24 hour no fly unless it's absolutely unavoidable. That's for even a single, within NDL dive. More no fly time advised for repetitive and multi day dives. Up to a minimum of 48 hours for anything even smacking of violating NDL.

 

[samdive]

best thing is to get a decent dive computer, it will tell you when you can fly. If you don't have one, I'd always recommend 24 hours minimum.

 

[Atlantis Fire]

Yeah, aircraft (especially commercial jets) are not actually kept at 1.0 atmosphere of pressure. They are kept at a lower pressure equivalent to being around 8000 ft of elevation when the plane is at cruising altitude. This corresponds to about 0.70 atm of pressure. Remember the special rules for diving at altitude etc. Aircraft also do not ascend and descend at a steady rate. They use a "step-up, step-down" approach, where they descend/ascend to a certain altitude at certain distance points from the airport. This means you change elevation a lot faster in a short amount of time compared to scuba diving. Either way, the high elevation pressure combined with the relatively rapid ascent/descent could cause all sorts of problems for scuba divers with extra nitrogen in their blood.

On a side note, Boeing's new 787 Dreamliner will be pressurized equivalent to about 6000 ft of elevation (0.77 atm) due to its sturdier composite body, so composite aircraft in the future may cause fewer problems for flying after diving. In addition, the step-up step-down approaches will be replaced by steady ascents/descents as computerized air traffic control systems improved. Numerous airports in the US are expected to begin adopting the improved systems within the next 5 years. But in the meantime we divers have to leave a pretty high margin for error.

 

[Melski]

Get a dive computer and follow the manufacturer recommendations. Stay well beyound 24 hours if possible. Consider skipping that last dive if you know you've screwed up one or more of the last few dives you've done.
Remember; no one else can do this for you - you have to do it yourself.

 

[Rip Tide]

I dove Tuesday, Thursday and Saturday last week. Each day two dives. All three times based upon my MOD and TAD I would say, based upon my computer, average of 28 hours 'No Fly Time".

It's physics and you can't beat it. If you need to fly the day after diving, it's probably better to just not dive. When we dive overseas we get all the dives out of the way toward the beginning of the week.

Stay safe.