New aircraft =shorter fly time?

[Frosty]

The new 787 Dreamliner advertises that the cabin is now pressurised to 6000 feet /1800m rather than the traditional height of 8000feet. I still prefer to stick to a 24 hour no fly after vacation diving but in theory does the "lower" height translate to theoreticaly shorter no fly times?

 

[DENLASCUBA]

This is an article from DAN that I cover with students about flying after diving.

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

 

[Rhone Man]

The new 787 Dreamliner advertises that the cabin is now pressurised to 6000 feet /1800m rather than the traditional height of 8000feet. I still prefer to stick to a 24 hour no fly after vacation diving but in theory does the "lower" height translate to theoreticaly shorter no fly times?

Theoretically. But people don't actually calculate the no fly period (otherwise theoretically its length would be based upon your time/depth of the preceding dives). So I am guessing no one will interfere with the 24 / 48 hour rule (depending upon which agency's rules you prefer). Shows inflation though - when I first learned to dive it was just 4 hours!

My computer calculates a no-fly time based upon a projected altitude (don't know what) but it rarely comes out much longer than 19 hours unless I have been doing some really heavy diving. 24 hours keeps you pretty safe as a rule of thumb.

 

[Diver0001]

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..

 

[Hickdive]

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"

 

[dreamdive]

It costs the airline money to pressurize their aircraft. On long flights, it is not unusual to drop as low as 10000 ft (0.7 ATA) = <15% oxygen. Ever wondered why you get so sleepy?

Just because they can pressurize to 6000 ft, does not mean that they will.

 

[tbone1004]

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.

fwiw, I'm ok with 6 hours if I do an extended deco stop, but typically it is more like 8-12 since I tend to take morning or late night flights.

 

[DENLASCUBA]

It costs the airline money to pressurize their aircraft. On long flights, it is not unusual to drop as low as 10000 ft (0.7 ATA) = <15% oxygen. Ever wondered why you get so sleepy?

Just because they can pressurize to 6000 ft, does not mean that they will.

As this did not sound correct I consulted a friend who is a pilot and has been in aviation safety for sometime this is his response to that.

Comercial airliners generally pressurize to a maximum height of 8000 feet. Any higher and it becomes dangerous. The FAA says the passengers can go to 10000 max but some will be sick at that altitude. We can go legally from 10 to 12 for up to half an hour only.

No cost savings whatsoever. How high the aircraft flies will affect costs. But not how high it pressurizes. But when you pressurize higher the pax will fall asleep quicker.

 

[Searcaigh]

All fine and dandy until some drunk or long bearded fundamentalist opens a door

 

[Hickdive]

All fine and dandy until some drunk or long bearded fundamentalist opens a door

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.