Increased conservatism?

[admikar]

An airliner cabin is pressurized to a minimum of 11psi, or the equivalent of 8000 feet.

Depending on route requirements and aircraft type, the cabin altitude may go up to 10 000 feet on a routine flight.

Partial and total pressure loss are far more common than one might think. Planning a perfectly safe situation and then getting bent because a 20$ valve develops a leak is not how I choose to live, YMM as always V.

Blac, point is, you're planing on 8000 ft cabin altitude, but if your plane suffers a pressure loss at 15k or more likely even higher, you're a goner, no if's and but's. Like RainPilot said, it occurs more than you think.

Not that I ever expect to push the limits of the DAN guidelines, but if you ever felt the onset of DCS on a plane, I wonder how hard it would be to get O2 from a flight attendant?

As far as I know there are no "spare" bottles on aircraft. O2 is part of aircraft's systems, in case of aircraft emergency, not on "one basis".

 

[RainPilot]

There is usually an AED and a small O2 bottle available. There are also oxygen masks at the flight attendant seats, not the drop down ones.

No chamber unfortunately so carefully does it.

 

[admikar]

OK, stand corrected, thank you.

 

[RainPilot]

OK, stand corrected, thank you.

No worries. We generally try very hard not to draw attention to them so easy to miss.

Next time you fly, when you board have a look in the very front overhead lockers. That’s where the first aid stuff is normally kept.

 

[dberry]

I suppose the question is if I told a flight attendant that I had been diving and was feeling symptoms of DCS, would she/he give me the O2? I've seen the green O2 bottles in the overheads in both the front and back, but I doubt they let me just take one down and start breathing from it!

 

[northernone]

Depending on route requirements and aircraft type, the cabin altitude may go up to 10 000 feet on a routine flight.

Partial and total pressure loss are far more common than one might think. Planning a perfectly safe situation and then getting bent because a 20$ valve develops a leak is not how I choose to live, YMM as always V.

In an agreeably redundant fashion I'll highlight this important part of the discussion.

I was at one point under the impression planning a dive @ 8000ft would allow for flying shortly after diving. With the rudimentary barometer I've been watching cabin pressure the last couple years on international flights. I saw 12,000 ft once already and there was no signs of distress that would have alerted the passengers but it would have blown my juvenile 'conservatism' folk lore understanding. Glad I was too poor to fly as a youngster and I didn't test out the theory personally.

Fly safe,
Cameron

 

[lv2dive]

Did anyone else laugh out loud when they read the sentence ???

....I have a moderate understanding of deco, ...
Simon M

 

[northernone]

Did anyone else laugh out loud when they read the sentence ???

A rye smile was enjoyed. His ongoing good natured contribution is delightful.

 

[RayfromTX]

Did anyone else laugh out loud when they read the sentence ???

Yes, it was classic Simon.

 

[rossh]

Using altitude procedures and decompression modelling software I can track and plan for the difference in pressures in my body tissues. An airliner cabin is pressurized to a minimum of 11psi, or the equivalent of 8000 feet. Using my flight times and altitude tables I can create a simulated deco profile within MultiDeco of my flight. I make sure that I don't cross a gf line of 80/80 before I fly, taking into account the rapid off gassing during ascent to cruising altitude.

DAN guidelines are conservative to the point that no one would have to worry about any of this, their dcs risk is near-as-makes-no-difference zero. That's why I called them super conservative though I can see why you would debate that description.

I don't recommend a diver flaunt flight guidelines without thorough understanding and planning. The existing guidelines are extremely safe, but like all incidences of increased conservatism it comes at the cost of decreased efficiency. If one is willing to do the research and planning they will find they can travel safely much soober than Dan guidelines in most cases.

Hi,

From MultiDeco and the supersaturation graphing, you can see how the DAN testing arrived at its results.

This is just one dive to 100 ft for 25 mins on air. Then at the 4 hour mark, we inserted the plane cabin pressure change effects. We are looking at the surface trace for supersaturation (gold line). Note that tissue bubbling and injury risk is present when the gold line is visible.

After 3 hours of SI, the Supersaturation has diminished to 0. At that point you're OK. But jumping on a plane returns the tissue to bubbling and supersaturation. The diver is at a much higher risk than non-divers. Non-divers never enter these supersaturation conditions.

The Time to Fly formula is sometimes made from those features - The time to get initial SS to 0 (3 hours) + the 16 hours time to reduce SS back to 0 again if you had entered the plane - for this dive about 19 hours.

.