Question about flying after diving

[BigJetDriver]

If the cabin altitude is 2000-8000 feet, how high up will the plane be? For example if my jet flies at 30,000 feet what will the cabin altitude be? Also, how does one know how high the jet will fly on any given day? Thanks.

These are both good questions. I'll take them in order.

(1) These days the 8000 ft msl cabin altitude figure is an outside limit. New aircraft pressurization systems are better at keeping the pressure up inside. Remember folks, there are many holes in the aircraft. We keep the pressure up by pumping more air in than leaks out. For the sake of general information, I have been checking the cabin pressure on various flights. At FL410, which is much higher than most aircraft fly generally, the cabin pressure is right at 7200 ft msl. At FL390 it is around 6300 ft msl as a maximum. At FL300 the cabin altitude will be around 5200 ft msl.

(2) We don't know how high the aicraft will be on any given day. The flight plan will be based on routing (Is it, for instance, over mountains?), and on the weight of the aircraft and winds. It will vary.

Uncle Ricky made a good point about un-pressurized aircraft. See the NOAA table that he cites for those cases. (Table 4.3 Page 4-28 NOAA Dive MANUAL).

Arctic Diver also made a goood point in stating that these are not hard and fast rules, nor are they guaranteed. They're like the "Pirate's Code", i.e. more of a set of "guidelines"!!

 

[Rick Murchison]

There have been cases of DCS associated with flying in people who have never made a Scuba dive in their entire lives.
With that as a baseline, realize there is a DCS risk in flying, period. Any additional nitrogen load you have prior to a flight increases that risk.
Following the guidelines from DAN and NOAA and others will reduce that risk to statistically insignificant, but cannot eliminate it. If you are the unlucky one-in-a-zillion that's no consolation, but the bet's still a good one for each of us on any given day.
That's life
Rick

 

[BigJetDriver]

There have been cases of DCS associated with flying in people who have never made a Scuba dive in their entire lives.
With that as a baseline, realize there is a DCS risk in flying, period. Any additional nitrogen load you have prior to a flight increases that risk.
Following the guidelines from DAN and NOAA and others will reduce that risk to statistically insignificant, but cannot eliminate it. If you are the unlucky one-in-a-zillion that's no consolation, but the bet's still a good one for each of us on any given day.
That's life
Rick

Rick,

You make an excellent point here, and it is one that most people do not take into account when thinking about DCS statistics.

The point is simple, really. The results for any given DCS avoidance procedure are actually stated in a ratio or percentage. It is as if you said to yourself, if I do this particular thing 10,000 times, I will get hurt once.

The problem with statistics is that, as Mark Twain once said: "There are liars, damn liars, and then there are statistics!" Nothing in this world states that you have a ZERO percent chance of this happening to you. It is just that, with the right amount of caution, your chances are very, very, very small. For this reason, we have gone away from calling unusual cases of DCS "un-deserved", and started using the description "un-expected". It is a more accurate description.

For those individuals who insist on pushing the envelope, such as MHK for instance, with his recommendation that one can actually do decompression diving and then "fly with your hair wet", I like to defer to our very own Doc Deco's comment. As he states, ANY time you change the parameters of the situation (i.e. do something other than what is recommended), you negate the results of the study. (In other words, your chances of bad things happening just went WAY up.) As Doc puts it, you might get away with it for a while, but when the failure occurs, it will be spectacular.

Nothing in life that we do is totally without risk, even staying IN bed. There are, however, things that we can do to REDUCE the risk level, and give us a better chance of returning safely to our significant other, or to yak about how the dive went on the Scuba Board.

Rob

 

[joed]

Thank you all so much, you all have been a terrific help. I was offered a spot on a boat last week and I knew I was flying the next day. The instructor told me about the 12 hour limit for diving above 60 feet. The first thing that happened in my mind was, what if for some reason I dive deeper than 60 feet, for a rescue perhaps or to retrive a piece of equipment such as my bifocal mask that may have been kicked off. My second brain flash was, what if we are on "Jamacian time" and the dive lasts longer than it is suppose to. The 3rd bright thought that I had was my instructor in 1973 telling us to wait 24 hours before flying.
I now know that according to studies 12 hours is probably ok but 24 hours is a safer bet. Thanks, again.

Rick,

You make an excellent point here, and it is one that most people do not take into account when thinking about DCS statistics.

The point is simple, really. The results for any given DCS avoidance procedure are actually stated in a ratio or percentage. It is as if you said to yourself, if I do this particular thing 10,000 times, I will get hurt once.

The problem with statistics is that, as Mark Twain once said: "There are liars, damn liars, and then there are statistics!" Nothing in this world states that you have a ZERO percent chance of this happening to you. It is just that, with the right amount of caution, your chances are very, very, very small. For this reason, we have gone away from calling unusual cases of DCS "un-deserved", and started using the description "un-expected". It is a more accurate description.

For those individuals who insist on pushing the envelope, such as MHK for instance, with his recommendation that one can actually do decompression diving and then "fly with your hair wet", I like to defer to our very own Doc Deco's comment. As he states, ANY time you change the parameters of the situation (i.e. do something other than what is recommended), you negate the results of the study. (In other words, your chances of bad things happening just went WAY up.) As Doc puts it, you might get away with it for a while, but when the failure occurs, it will be spectacular.

Nothing in life that we do is totally without risk, even staying IN bed. There are, however, things that we can do to REDUCE the risk level, and give us a better chance of returning safely to our significant other, or to yak about how the dive went on the Scuba Board.

Rob

 

[ArcticDiver]

Thank you all so much, you all have been a terrific help. I was offered a spot on a boat last week and I knew I was flying the next day. The instructor told me about the 12 hour limit for diving above 60 feet. The first thing that happened in my mind was, what if for some reason I dive deeper than 60 feet, for a rescue perhaps or to retrive a piece of equipment such as my bifocal mask that may have been kicked off. My second brain flash was, what if we are on "Jamacian time" and the dive lasts longer than it is suppose to. The 3rd bright thought that I had was my instructor in 1973 telling us to wait 24 hours before flying.
I now know that according to studies 12 hours is probably ok but 24 hours is a safer bet. Thanks, again.

Good on you joed!

To me a vital part of Risk Management is to decide whether the worst reasonable outcome is worth doing whatever it is that I'm about to embark on. The other main part is to realize that, other than death, no life outcome is absolutely certain. There is risk in absolutely everything.

So I try to keep the odds in my favor and remember an old preacher's lesson: "Son, you gotta be ready to pray, or die on a moment's notice. So live well, be ready; but don't rush into either."

 

[diverbob]

I play it safe, wait 24 hours and all should be good. Last thing I want to do is get bent in an airplane.

 

[AggieDad]

[ As he states, ANY time you change the parameters of the situation (i.e. do something other than what is recommended), you negate the results of the study. (In other words, your chances of bad things happening just went WAY up.) As Doc puts it, you might get away with it for a while, but when the failure occurs, it will be spectacular.

Rob[/QUOTE]

I am sure will back me up here about the above statement. In our business when one does not follow the approved procedures especially in an abnormal situation you now are a test pilot. We aren't paid to be test pilots.

 

[BigJetDriver]

For those individuals who insist on pushing the envelope, such as MHK for instance, with his recommendation that one can actually do decompression diving and then "fly with your hair wet", I like to defer to our very own Doc Deco's comment. As he states, ANY time you change the parameters of the situation (i.e. do something other than what is recommended), you negate the results of the study. (In other words, your chances of bad things happening just went WAY up.) As Doc puts it, you might get away with it for a while, but when the failure occurs, it will be spectacular.

I am sure Rob will back me up here about the above statement. In our business when one does not follow the approved procedures especially in an abnormal situation you now are a test pilot. We aren't paid to be test pilots.

I sure will back you up on that. Now, if you want to talk about a good-sized pay override for that maintenance test flight..... :monkeydan

If we are talking about risking ourselves when it comes to being bent (and twisted) with DCS, I'll pass on trying it, even if there were a bonus offered! :11:

Rob

 

[pipedope]

Remember that all of the guidelines stipulate that you are showing NO Symptoms of DCS.

If you are showing ANY symptoms of DCS go to the chamber NOT the airport.

If you look at the stats from DAN you will find that the vast majority of people who got bent on an airplane were showing symptoms before flying.

 

[boulderjohn]

Here in the Rocky Mountain region, people will dive in, say, Utah, in the morning. They know they should not fly back to Denver in a plane (Pressurized to 8,000 feet), so they drive back on I-70, going over Eisenhower Pass (11,000 feet).

I wonder why there is no well-advertised warning about taking mountain passes after diving.