Why wait 12-24 hrs to fly?

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Mr Carcharodon

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So is flying at just 1000' (plane not pressurized of course) 4 hrs after that dive profile too much risk? The utility would be nice.


?

The thing that muddles this up is working in two sets of units for pressure. If you consider sea level to be 1 atmosphere, or 33 feet of sea water absolute (fswa), then 1000 feet above sea level is 31.8 fswa. Would you think you totally blew your deco if you did it 1.2 feet shallower than planned? Would you normally wait 4 hours (or DAN's recommended 12 hours) to move up a foot in the water column?
 

CoopAir

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The thing that muddles this up is working in two sets of units for pressure. If you consider sea level to be 1 atmosphere, or 33 feet of sea water absolute (fswa), then 1000 feet above sea level is 31.8 fswa. Would you think you totally blew your deco if you did it 1.2 feet shallower than planned? Would you normally wait 4 hours (or DAN's recommended 12 hours) to move up a foot in the water column?

My thoughts exactly.
 

boulderjohn

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So is flying at just 1000' (plane not pressurized of course) 4 hrs after that dive profile too much risk? The utility would be nice.
The DAN study that set the 12/18 hour recommendation said that ascents of less then 2,000 are acceptable without any wait.
 

Afishianado

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Give it a try and get back to us. Good luck.

http://www.scubaboard.com/forums/ne...ried-fly-out-today-i-ended-up-being-bent.html

I want this to be a warning to anyone that reads flying 22 hrs after diving. Im writing to you from the most expensive hotel room you can get a hospital bed at St Marys in west palm beach FL. Friday morning i dove 2 100ft dives on air 40min 45surface 17min down again on a wreck in Key west. I took off at 7:20am the next day back to phoenix when the aircraft got to about 10 k feet started to feel strange my left hand and arm started to tingle then my right arm and both legs.I knew exactly what happened. the plane landed back at the airport and i was air lifted a helocopter here spent 5 hrs in the chamber on 100% o2. I had all my gear in my checked bags so i might not have the exact time correct just going from memory. I learned a lesson could have been a lot worse. Im still feeling the tingle in my leg off o2 so ill do another dive in the chamber again tomorrow morning.

Don't introduce this into the discussion on flying after diving. The flying isn't the problem here. A 100' dive for 40 mins on air is double the NDL (for PADI tables an an example and also close to that for all of my computer algorithms) followed by a 45 min surface interval and another dive to 100 ft which is close to the NDL as a first dive, not to mention as a multiple with a short SI. Granted, we do not know the exact profiles etc but at first glance these dives where provocative anyway. The diver may well have been bent even if he didn't fly.

No one knows more about flying after diving than DAN, read up on the flying after diving study. Even considering your logic in the OP why would you intentionally place yourself at an increased risk of DCS beyond what DAN recommends? I like diving and my health more than I like shaving a few hours off of my travel schedule.
 

c-fstb

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I'm glad to see this conversation because of questions I've long had myself, but was hesitant to ask. Please correct me if I'm way of base here, but it seems that the effect of atmospheric pressure drop on the body is not linear, but rather it seems it is exponential. The above example of 1000ASL being equivalent to 1.2FSWA would seem to be insignificant, however using the same rational we could say that a dive from 33' to surface would be equal to surface to the edge of space. The rise from 33' to the surface has a fairly negligible effect on the body but the rise to the top of the atmosphere would be drastically worse for your health. (according to Dr. McCoy (Bones) your blood will boil in 13 seconds:wink:) Since we also perform the majority of decompression time at a relatively shallow depth of 15' even after exposure to vastly greater pressures at depth, it would seem so. However this conclusion is not based on any significant study of empirical data so I may be completely wrong.
The reason I'm so interested in this is related to my other hobby, experimental aircraft. I finished building my own plane about 10 years ago, when I was just an occasional vacation diver using rental gear. At the time I was building I had this fantasy of flying it to exotic locations and diving before flying elsewhere. In the last year I started to pursue diving in earnest and have bought all of my own cold water gear, which is so heavy I've realized the impossibility of hauling 2 sets of gear with at least a spare set of tanks in a light aircraft... fantasy indeed! However I can't stop thinking about flying it down to more tropical locales where tank & weight rentals abound and required gear weight is minimized. Island hopping in my own plane seems like a fantastic way to get to some fantastic dive spots. If only it weren't for that pesky no-fly time. As I can choose to fly at low altitudes as well as set my own departure time, this can be managed, however should any sort of DCS be encountered during flight it would be rather inconvenient to say the least.
Since divers should share many personality traits with pilots, I'd be shocked if there weren't at least a few pilot/plane owners on this forum and a subject such as this should surely catch their attention. I'm really interested in what those with experience in this would have to say?
 

CoopAir

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I'm glad to see this conversation because of questions I've long had myself, but was hesitant to ask. Please correct me if I'm way of base here, but it seems that the effect of atmospheric pressure drop on the body is not linear, but rather it seems it is exponential. The above example of 1000ASL being equivalent to 1.2FSWA would seem to be insignificant, however using the same rational we could say that a dive from 33' to surface would be equal to surface to the edge of space. The rise from 33' to the surface has a fairly negligible effect on the body but the rise to the top of the atmosphere would be drastically worse for your health. (according to Dr. McCoy (Bones) your blood will boil in 13 seconds:wink:) Since we also perform the majority of decompression time at a relatively shallow depth of 15' even after exposure to vastly greater pressures at depth, it would seem so. However this conclusion is not based on any significant study of empirical data so I may be completely wrong.
The reason I'm so interested in this is related to my other hobby, experimental aircraft. I finished building my own plane about 10 years ago, when I was just an occasional vacation diver using rental gear. At the time I was building I had this fantasy of flying it to exotic locations and diving before flying elsewhere. In the last year I started to pursue diving in earnest and have bought all of my own cold water gear, which is so heavy I've realized the impossibility of hauling 2 sets of gear with at least a spare set of tanks in a light aircraft... fantasy indeed! However I can't stop thinking about flying it down to more tropical locales where tank & weight rentals abound and required gear weight is minimized. Island hopping in my own plane seems like a fantastic way to get to some fantastic dive spots. If only it weren't for that pesky no-fly time. As I can choose to fly at low altitudes as well as set my own departure time, this can be managed, however should any sort of DCS be encountered during flight it would be rather inconvenient to say the least.
Since divers should share many personality traits with pilots, I'd be shocked if there weren't at least a few pilot/plane owners on this forum and a subject such as this should surely catch their attention. I'm really interested in what those with experience in this would have to say?


Glad to see another private pilot on this board! I think there is a fair amount of overlap in terms of pilots who dive as well.

Like you I am a new diver (got my C-card last August) but have been flying for many years before that.

In 6 short months I went from being as apprehensive about simple OW recreational diving as most passengers are thinking about their first flight in a piston single to wanting to learn wreck and cave diving (which I've always thought of the equiv to flying in night with 200' ceilings with a 30 kt crosswind)!
 

c-fstb

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I suspected that your original post was hinting at private rather than commercial flight. I've never been too apprehensive about new adventures, instead usually being a little to eager, however parenthood has tempered those tendencies somewhat.

If I was building a plane today, I would certainly build something different that would have diving as a prime mission. But I have it at home in my shop right now and am considering a few changes that would make it a little better suited to the purpose.

But I'd really like to hear from others that have direct experience with diving and light aircraft.

Picture this; Landing on a remote beach, diving the reef, camp overnight on same beach, fly to source of tank refill, repeat.
Fantasy or possibility??

Todd
"Whatever you vividly imagine, Ardently desire, Sincerely believe in, Enthusiastically act upon, Must inevitably come to pass"
 

theduckguru

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A diver wants to dive at sea level. If he wanted to fly in a unpressurized plane below 5000 ft after diving, why couldn't the diver set his computer for maximum high altitude setting, ie 10,000 ft, prior to diving then fly?
 

Hatul

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I'd have to believe that a lot of the reason is relative pressures. You know how people keep saying the pressure gradient is greatest very shallow? It's the same thing, but more pronounced in the air. Yeah, it's only the equivalent of 8fsw....but the pressure at 35000ft is 25% of the atmosphere at sea level. That's a HUGE difference if the plane depressurizes. Even at 8000ft, it's still 60% of the pressure at sea level. HUGE difference.

I think you have part of the answer, in that there is a large relative pressure change from sea level. But that's not all. Is this the same as an altitude dive from 8000 ft, so we can just use altitude tables or set our computer to 8000ft? The answer is no.

It's the same as a saturation dive from 8000 ft in air to sea level, then a further dive, then an ascent to 8000 ft. It's that saturation part that's the problem, and is related to the slow compartment explanation which gets saturated. The equivalent in terms of relative pressure changes is a saturation dive from sea level to 23 ft sea water, then a further deeper dive, then a slow ascent back to sea level. Because of tissue saturation to 23 ft, the requirement is to make the final ascent from 23 ft over a period of 12-18 hrs to avoid the risk of DCS.

It's really because the diver starts out saturated to 1 atm, does a further dive and finally has to ascend to subatmospheric 0.6 atm.
 
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