New aircraft =shorter fly time?

[Altamira]

If you find yourself in an unpressurized aircraft at cruising altitudes, you have bigger problems than the bends..

Normally not true. If you lose cabin pressurization at altitude, even a rapid decompression, it normally is not that big of a deal (assuming that the aircraft has not had some other catastrophic structural failure). Aircrews routinely practice loss of cabin pressurization during simulator training and evaluations, and hyperbaric chamber crew members routinely ride in the chamber while training military pilots. The recovery procedure involves getting on 100% oxygen, declaring an emergency for a rapid, but controlled, descent, and flying the airplane to an altitude below 10,000 ft or minimum obstruction clearance altitude. While the descent procedure may frighten the passengers, it really is not that big of a deal as far as inflight emergencies are concerned. I would rather have a rapid decompression once a month than a single episode of DCS.

 

[Frosty]

Who recommends 24 hours?Neither DAN nor PADI do. Where is this recommendation coming from?

Sorry dude 24 hours works for ME. Vacation diving for me involves a lot of diving and I dive my own gear.
24 hour no fly gives me time to rinse my gear.dry it (to reduce weight) FIND it all and pack it all away
keep in mind in my family there are 6-7 of us diving and 5 of em are kids--its ol dad that has to pay for overweight and any lost gear

 

[boulderjohn]

Sorry dude 24 hours works for ME. Vacation diving for me involves a lot of diving and I dive my own gear.
24 hour no fly gives me time to rinse my gear.dry it (to reduce weight) FIND it all and pack it all away
keep in mind in my family there are 6-7 of us diving and 5 of em are kids--its ol dad that has to pay for overweight and any lost gear

I see--I think. Your rationale for the 24 hour wait before flying seems to have less to do with aircraft pressure than I would have expected. Are you arguing that with a higher cabin pressure you will be able to fly sooner than 24 hours because your gear will dry faster before you pack it?

I dive my own gear, too, and I sometimes have uncooperative drying conditions. Here is a tip. On my last trip (a month ago), I did not have a lot of time , and it was raining a lot the last day. We were staying in a place that gave us pool towels. We could trade in old towels for new ones any time we wanted. We used a steady parade of pool towels to get our gear dry. Wrap up the wet suits in a big towel and walk on it until the towel is soaked. Then go get a new towel. That will work pretty darn well for most of your gear. Perhaps using such techniques will allow you to fly within the DAN and PADI specified limitations.

 

[Scared Silly]

FWIW DAN uses 8k feet for their studies:

Scuba Diving Health & Fitness | Dive Medicine | Flying & Diving | Ask DAN | Scuba Diving

Flying After Diving -- Cracking the DCS Code ? DAN | Divers Alert Network ? Medical Dive Article

 

[KeithG]

Not sure why, but I've long been under the impression that the long time before flying is significantly conservative, and partially related to the possibility of exposure to cabin pressures below the typical 8000'. The lower pressure could be be from flying in non-pressurized craft, as well as a mishap in pressurized craft.

The pressure at 8000' is about 75% of sea level pressure. I don't know a lot about deco theory, but I'm pretty sure that 12 hours will let a 720 minute tissue lose half of its N2 load, and that offgassing 50% will allow you to further reduce ambient pressure by 50%. Thus if you weren't bent at 1ATA on the surface you shouldn't get bent by flying 12 hours later even if the cabin pressure drops to 60% of sea level pressure. OTOH, lose cabin pressure anywhere above about 18,000 and pressure may drop below 0.5ATA. Even then, unless that slowest tissue was close to saturation you should have a bit more leeway. Of course it's called deco theory, and not everyone reacts the same way to any given compression/decompression cycle.

As noted above, planes lose cabin pressure on a fairly regular, though infrequent basis, usually with fairly minor consequences. Typically the problem is easily and quickly solved by a rapid descent, and that means that pressure will be restored to 8000' (or something close) pretty quickly. That would mean that getting bent is still pretty unlikely. Like all the non-diver passengers the bigger risk is that an abrupt depressurization could result in the sort of barotrauma we normally avoid by not holding our breath.

That was my impression as well, but we were wrong. DAN tested to 8000 ft. Their guidance is based upon a max altitude of 8000 ft. If your plane loses pressure, then it sucks to be you, even if you thought you were totally safe by following the DAN guidelines.