Where's your buddy?

[bleeb]

I was not diving for several days and knew it would adjust to the lower altitude shortly. For more reason then mentioned above, I always carry my computers on with me now as to not get erroneous altitude readings. I am not knowledgeable about how planes are pressurized but would make the assumption that the baggage compartment is not as pressurized as the passenger compartment.

AFAIK, in all modern commercial passenger jets (including commuters), the passenger and baggage compartments share the same air space, although parts of the baggage compartment may not be well heated or have good circulation. (It can easily be -50F outside.) Same goes for the majority of larger propeller-driver puddle jumpers (i.e. Dash 8s) and even many smaller ones, although there may be more exceptions, especially some of the older and smaller designs.

 

[DandyDon]

AFAIK, in all modern commercial passenger jets (including commuters), the passenger and baggage compartments share the same air space, although parts of the baggage compartment may not be well heated or have good circulation. (It can easily be -50F outside.) Same goes for the majority of larger propeller-driver puddle jumpers (i.e. Dash 8s) and even many smaller ones, although there may be more exceptions, especially some of the older and smaller designs.

I think that is correct. I think that my Oceanic puters that had activated inflight had read the atmospheric pressure equivalent to 8,000 ft + 1,000, but on landing at sea level took the increase as a shallow dive. I could not get them to clear, but they turned off during the night and cleared. I think it's happened to me twice, but I am not sure if how I had them packed; been a long time.

I am not clear how how DD36 thot his puters were reading extremely high elevation at sea level? Indeed, I think Oceanics only read up to 10,000, but his experiences at sea level may have been something like mine. I'm guessing tho, and curious.

Back to the idea of knowing your dive puter well: Very Important! On our last trip together, I learned that my home bud (who wears Oceanics in part so I can help him with batteries and handling) had forgotten some, didn't realize why it beeped when he went 1 minute into deco, etc. Basically he was wearing it so I could read it I guess, but I didn't realize all this until after that dive. It cleared on the Safety Stop anyway, but still - know what your computer is telling you at all times, please. Run various Sim Dives.

 

[DeepDiver36]

AFAIK, in all modern commercial passenger jets (including commuters), the passenger and baggage compartments share the same air space, although parts of the baggage compartment may not be well heated or have good circulation. (It can easily be -50F outside.) Same goes for the majority of larger propeller-driver puddle jumpers (i.e. Dash 8s) and even many smaller ones, although there may be more exceptions, especially some of the older and smaller designs.

I now remember TSA having me turn on both putters to show them NASA was safe from a hack. They would have remain on for at least 24 hours. If I recall they were clear to go in the AM. In retrospect, I guess I could always remove the battery during flight so they will not read anything.

I did check the max altitude reading for the VT3, which is 14k. Bleeb, do you know if that is what they pressurize the cabin at?

 

[bleeb]

I did check the max altitude reading for the VT3, which is 14k. Bleeb, do you know if that is what they pressurize the cabin at?

Not 14k, unless the plane blew out a seal or a window, in which case you'd likely have noticed, since the oxygen masks would probably have been falling from the ceiling and the pilot would be taking the plane down real fast to get to an altitude where most people can breathe comfortably, before the O2 ran out.

Normal pressurization standard for passenger aircraft is to the equivalent of no more than 8,000' or about >0.78 ata. A selling feature of the new 787 is that it's built to withstand an internal pressure of <6,000'. Some business jet models will even pressurize to 1 ata, as long as they fly below certain altitudes. (Those models are the ones that are sometimes used for hyperbaric emergencies or medical transport of patients with certain lung or breathing problems.)

And yes, this means that planes actually do have to let air out in order to open the doors if landing at really high altitude airports.

 

[DandyDon]

I now remember TSA having me turn on both putters to show them NASA was safe from a hack. They would have remain on for at least 24 hours. If I recall they were clear to go in the AM. In retrospect, I guess I could always remove the battery during flight so they will not read anything.

I did check the max altitude reading for the VT3, which is 14k. Bleeb, do you know if that is what they pressurize the cabin at?

Where did you turn them on for TSA? I looked at the specs for the VT3 (and the price :shocked2: ) and that is a lot fancier dive puter than my Versa Pro or VEO 2 and I see that it indeed can adjust to 14,000 ft. I am not going to study the manual enough to understand it and will rely on your understanding, but wouldn't the computer stay at the altitude where it was turned on until it times out? As Bleeb answered, airliners are generally pressurize at atmospheric pressure equivalent to 8,000 ft as I'd referenced in my post.

BTW, if I wanted to pull the battery long enough to reset the puter, I don't think I'd do that on the plane or in an airport even. Some folks might get excited. I think I'd wait until I got to the resort.

 

[DeepDiver36]

Where did you turn them on for TSA? I looked at the specs for the VT3 (and the price :shocked2: ) and that is a lot fancier dive puter than my Versa Pro or VEO 2 and I see that it indeed can adjust to 14,000 ft. I am not going to study the manual enough to understand it and will rely on your understanding, but wouldn't the computer stay at the altitude where it was turned on until it times out? As Bleeb answered, airliners are generally pressurize at atmospheric pressure equivalent to 8,000 ft as I'd referenced in my post.

On the VT3 is you hit any of the three buttons the computer will turn on and stay on for 24 hours. I would assume this feature is so it will keep track of 'no-fly' time. Literally speaking, there is no 'off' button.

Since it stays on for the duration of the flight, it will read the altitude while you fly. Like I mentioned in an earlier post, I do not recall exactly what altitude it read after the plane ride to sea level but I do remember that I could not dive with it like that as it would adjust my depth reading, no-decon time and dive plan accordingly. I would not feel safe diving with it in that state. The computer is doing what it is designed to do but in this rare circumstance, it would provide misinformation.

BTW, if I wanted to pull the battery long enough to reset the puter, I don't think I'd do that on the plane or in an airport even. Some folks might get excited. I think I'd wait until I got to the resort.

The best way is to not have TSA make you turn it on. If it is off, then it does not read the altitude. Once it is on, as mentioned above, it stays on for 24 hours. I would retreat to a stall to uninstall the batteries. I have never tested it like that, I wonder if it would recall the last altitude it was at or if taking the battery our resets it all together, in which case, just taking the battery out after landing would solve the problem. I will have to research that.

UPDATE: Talked to the wonderful peeps at Oceanic and they confirmed that talking the battery out will reset the altitude. All to worry about nothing!

On a side note. I live in Salt Lake City and when I made a dive at the homestead I had turned my watch on before I left to check battery levels. Upon arriving at the Homestead, I noticed it gave me an altitude of 7,200 where the dive site was only at 6,000. I was confused until on the way home it dawned on my that it was adjusting for the highest altitude that I would pass through on my drive to and from.

It would make since that you could have some complications from driving to a higher altitude then what you dove at. Could you imagine if you dove in Cali at sea level and then immediately headed into the mountains. I would imagine you could experience some of the same problems mountaineers do when they move up to face and do not acclimatize properly. Anyone help me with that?

 

[DandyDon]

On the VT3 is you hit any of the three buttons the computer will turn on and stay on for 24 hours. I would assume this feature is so it will keep track of 'no-fly' time. Literally speaking, there is no 'off' button.

Yes, my Oceanic puters come on with a touch of any button. I think mine go off in 12 hours if nothing else happens, but if I dive them then they stay on to count down the time to fly and 24 hours both to give the diver a choice of which to use.

Since it stays on for the duration of the flight, it will read the altitude while you fly. Like I mentioned in an earlier post, I do not recall exactly what altitude it read after the plane ride to sea level but I do remember that I could not dive with it like that as it would adjust my depth reading, no-decon time and dive plan accordingly. I would not feel safe diving with it in that state. The computer is doing what it is designed to do but in this rare circumstance, it would provide misinformation.

Okay, that's one of the features in which your Oceanic puter is fancier. Mine will read air pressure when turned on, then set the diving at altitude calculations at that pressure and stay there until they turn off. Mine do not give actual elevation readings; you just get less dive time.

The best way is to not have TSA make you turn it on. If it is off, then it does not read the altitude. Once it is on, as mentioned above, it stays on for 24 hours. I would retreat to a stall to uninstall the batteries. I have never tested it like that, I wonder if it would recall the last altitude it was at or if taking the battery our resets it all together, in which case, just taking the battery out after landing would solve the problem. I will have to research that.

UPDATE: Talked to the wonderful peeps at Oceanic and they confirmed that talking the battery out will reset the altitude. All to worry about nothing!

On a side note. I live in Salt Lake City and when I made a dive at the homestead I had turned my watch on before I left to check battery levels. Upon arriving at the Homestead, I noticed it gave me an altitude of 7,200 where the dive site was only at 6,000. I was confused until on the way home it dawned on my that it was adjusting for the highest altitude that I would pass through on my drive to and from.

Fancy little computer you got there. More to know too.

It would make since that you could have some complications from driving to a higher altitude then what you dove at. Could you imagine if you dove in Cali at sea level and then immediately headed into the mountains. I would imagine you could experience some of the same problems mountaineers do when they move up to face and do not acclimatize properly. Anyone help me with that?

It is a common consideration for divers traveling to higher altitudes after diving. Albuquerque and Colorado divers have to keep such in mind after diving Santa Rosa NM; I don't as I head down hill from there. The NOAA diving manual has a section of that, but it sounds like your puter covers it for you.

 

[bleeb]

It would make since that you could have some complications from driving to a higher altitude then what you dove at. Could you imagine if you dove in Cali at sea level and then immediately headed into the mountains. I would imagine you could experience some of the same problems mountaineers do when they move up to face and do not acclimatize properly. Anyone help me with that?

The issues most of concern are slightly different. Mountaineers are worried about altitude sickness, which is caused (massively simplifying) mainly by not enough oxygen. I think what you have in mind is the same thing divers are always concerned about: excess nitrogen and DCS.

It is a common consideration for divers traveling to higher altitudes after diving. Albuquerque and Colorado divers have to keep such in mind after diving Santa Rosa NM; I don't as I head down hill from there. The NOAA diving manual has a section of that, but it sounds like your puter covers it for you.

For the sake of the discussion, NOAA guidelines for controlling ascending in altitude can be found here: Required Surface Interval Before Ascent to Altitude after Diving
using the letter pressure groups are from the NOAA No-Deco Air Table.