New aircraft =shorter fly time?

[HungoverDiver]

I don't know about you, but I've never been able to predict, let alone dictate which type of aircraft I'll be flying on.

R..

You can make some predictions based on the airline and flight, e.g. Virgin Australia SYD->LAX is always Boeing 777, LAX->SAN will never be a Boeing 787, etc. assuming no unpredicted aircraft changes.

 

[Diver0001]

Dude, I'm just happy that I get to the airport on time. They could fly me there on the back of an albatross and I probably wouldn't notice the difference.

R..

 

[Dr. Lecter]

They could fly me there on the back of an albatross and I probably wouldn't notice the difference.

Assumes a paucity of aged, crossbow-wielding seafaring men that may or may not hold true.

 

[Altamira]

My recommendation: Don't even think of basing your time to fly on what kind of airplane you are scheduled to have for your flight leg, or what you think the cabin pressure is going to be on that flight. As a retired military and commercial airline pilot, I can assure you that cabin pressurization system problems and failures are not that uncommon. You do not want to be at 35,000ft (cabin pressure of 8,000ft), see the O2 mask drop down, and suddenly realize that grabbing the mask is going to be the least of your problems.

 

[Searcaigh]

Passenger doors on a pressurised aircraft open inward and are held closed against the seal and door frame by the internal pressure. Pressurised to 8,000ft but flying at 35000ft creates a pressure differential of just under 0.5 kg/cm2. A door 1 metre wide and 2 metres tall would have over 9 tonnes of pressure holding it shut, well over 20,000 lbs and that assumes a flat door, not a curved one with even greater surface area.

A aircraft flying at 35000ft but pressurised to 6000ft will have an even greater pressure differential holding the door closed.

Despite what you see in the movies (or worse still, hear reported in prosecutions of drunks on aircraft) there's no way you're opening the door just by turning the handle and giving it a pull.

When you're on the ground the cabin staff open the door inwards, turn it through 90 degrees and then push it back out through the door way so it can lie against the outside of the plane.

Good to know as I am usually flying in planes with a few long bearded fundamentalists sitting around the cabin, and the drunks are usually locals heading back to Riyadh. Witnessed a few fights with respect to the latter requiring some restraint by the cabin crew, thankfully none of them sitting next to me.

 

[boulderjohn]

Who recommends 24 hours?

Neither DAN nor PADI do. Where is this recommendation coming from?

 

[dumpsterDiver]

According to this Air Pressure and Altitude above Sea Level the difference in cabin pressures between 6000 and 8000 ft is around 0.6 bar. Similar to the pressure difference between being at 6 metres depth or the surface.

Theoretically, that should make a difference. However, you have no way of being certain that you will be travelling in a specific type of aircraft or that it will be pressurised to the altitude you require.

On balance I think I'd stick to the usual 24 hour rule of thumb rather than picking up the emergency card from the seat pouch, looking at the aircraft type and thinking "oh dear, this isn't a dreamliner"

No you are not correct. Check the references you posted. the difference is like 1.1 psi maybe 0,08 bar.

 

[Rhone Man]

However, you have no way of being certain that you will be travelling in a specific type of aircraft or that it will be pressurised to the altitude you require.

I don't know about you, but I've never been able to predict, let alone dictate which type of aircraft I'll be flying on.

Am I like the only guy in the world who selects his seats by using Seatguru (www.[B]seatguru[/B].com/) - tells you exactly what type of aircraft (and its configuration) for your flight.

Rhone, I actually see the opposite, generally on longer/deeper dives my tissue loading at the end is much lower than when I'm doing NDL diving because I'll do an extra few minutes on my O2 stop and it lowers the N2 loading considerably. That being said, I'm not going to base anything off of what the cabin pressures say they're going to be. I base it all off of 0.5ata/16000ft just to be safe. Having worked with DAN quite a bit on the FAD, I have a bit more liberal times for myself than the agencies do, but I've also done working dives in the chambers then been flown, so I have a bit more real world experience in controlled environments.

Fair point. Account for fast tissue / slow tissue analysis.

 

[mjrob]

I don't know about you, but I've never been able to predict, let alone dictate which type of aircraft I'll be flying on.

R..

You can if you fly out of general aviation.

i pick my commercial seats when I buy tickets and they'll tell you the aircraft they PLAN to fly...but that's not always the one they DO fly. Haven't flown a Dreamliner yet but would like to...

 

[Hickdive]

No you are not correct. Check the references you posted. the difference is like 1.1 psi maybe 0,08 bar.

Apologies, I calculated the difference between 8000 and 35000ft instead of 8000 and 6000ft.