Can I calculate the time before flight by myself?

[GrumpyOldGuy]

Here's a link to all the NOAA charts. The Ascent to Altitude after diving is key, use a 8,000ft altitude for pressurized aircraft (airliners, not bush planes). A warning: This chart is used with the NOAA tables which are different than PADI, don't assume the PADI or other tables can be used as the letter codes are different.

Index of /pdfs

 

[Hoomi]

This would be the basis of all dive tables, so why you think this is iffy eludes me.

Primarily, my statement is due to the additional factors of being aboard an airliner. If I'm in my hotel room a few hours after a dive, and start to feel symptoms of DCI, it's a pretty good chance I'm closer to emergency medical care, than if I'm aboard an airliner at 35,000 feet over the Pacific Ocean. Additionally, if my calculations are leaving little room for error, and I'm wrong, then it's not just my health that I'm risking. I'm also potentially messing with the travel schedules of everyone else aboard the airliner, if the flight has to divert to take me to the nearest airport for emergency medical care.

In any risk assessment situation, the more factors you add in to the scenario, the greater the potential for catastrophic results. We make calculations assuming we're somewhere close to the middle of the bell curve, and then incorporate a fudge factor to improve our safety margin. Unfortunately, the human body is not a static factor. With all of our science and research, we still don't fully understand all the dynamics of physiology, and why something that was fine yesterday, isn't fine today.

My point wasn't that we can't make calculations, but rather, why not just plan conservatively for safety's sake? It might be one thing if I get back to the dock after a dive, to find a message that one of my kids back home was just in a horrible accident, and we need to leave ASAP. For routine travel, though, it just makes more sense to take the recommended interval into account when scheduling trip activities.

 

[GrumpyOldGuy]

Primarily, my statement is due to the additional factors of being aboard an airliner. If I'm in my hotel room a few hours after a dive, and start to feel symptoms of DCI, it's a pretty good chance I'm closer to emergency medical care, than if I'm aboard an airliner at 35,000 feet over the Pacific Ocean. Additionally, if my calculations are leaving little room for error, and I'm wrong, then it's not just my health that I'm risking. I'm also potentially messing with the travel schedules of everyone else aboard the airliner, if the flight has to divert to take me to the nearest airport for emergency medical care.

In any risk assessment situation, the more factors you add in to the scenario, the greater the potential for catastrophic results. We make calculations assuming we're somewhere close to the middle of the bell curve, and then incorporate a fudge factor to improve our safety margin. Unfortunately, the human body is not a static factor. With all of our science and research, we still don't fully understand all the dynamics of physiology, and why something that was fine yesterday, isn't fine today.

My point wasn't that we can't make calculations, but rather, why not just plan conservatively for safety's sake? It might be one thing if I get back to the dock after a dive, to find a message that one of my kids back home was just in a horrible accident, and we need to leave ASAP. For routine travel, though, it just makes more sense to take the recommended interval into account when scheduling trip activities.

Respectfully, it is not really a new factor, just another pressure gradient to calculate (about 22' equivalent depth) that in essence makes it a deeper dive with a long S/S before the final 22' ascent.

I agree, we don't have a full understanding of all DCI issues, but the physics part of it is easy to calculate. The individual variables (health, age, obesity, dehydration and other conditions) are in play any time you dive. The NOAA tables have a lot of scientific research behind them by people a lot smarter than me.

 

[Session Eleven]

While rare (40-50 occur annually across all types of aviation), I think it is also worth bearing in mind that a decompression event on an airliner can mean a diver could spend up to several minutes at 20 or 30 thousand feet. A simple decompression typically results in no injuries, but if a diver is riding the line to begin with, it could spell trouble. They occur rarely enough that an informed diver may elect not to account for them, but the possibility adds another, subjective wrinkle to the no-fly time.

 

[GrumpyOldGuy]

While rare (40-50 occur annually across all types of aviation), I think it is also worth bearing in mind that a decompression event on an airliner can mean a diver could spend up to several minutes at 20 or 30 thousand feet. A simple decompression typically results in no injuries, but if a diver is riding the line to begin with, it could spell trouble. They occur rarely enough that an informed diver may elect not to account for them, but the possibility adds another, subjective wrinkle to the no-fly time.

You are correct in that it is another wrinkle. If you dig deeper, you may find the only the slowest tissue compartments still have residual gas if you are following NOAA tables, and being slow tissues the 2-3 minutes at 20-30K may not be the critical factor. I would think a far more dangerous scenario would be a partial failure in the system where the plane is not fully pressurized and the pilots don't realize it.

 

[DandyDon]

The cabins are pressurized to 8,000 ft max, and if their systems fail that - you have bigger problems than a hit.

 

[diveprof]

The one issue with trying to do this with the NOAA tables is that if you have been diving using your dive computer all week with multiple dives each day it is unlikely that you could determine your ending last dive pressure group with any degree of accuracy (particularly if you were doing multilevel dives). As previously stated, some dive computers can process this others just use a countdown clock.The easier and safer way is just to be conservative.

 

[RTee]

Not sure what advantages I would get from attempting to calculate such a time from table following a single dive let alone a week of multiple days of repetitive diving. As an example, I just returned from a week of diving in Cozumel where I did 21 dives over a 6.5 day period. I think there would have been too many factors to come up for such calculation myself. That is why I usually leave it to my Suunto Vyper to figure it out. Suunto is renowned to be conservative, too much at time. Therefore, I figure that if I abide by its number, I should be OK. FYI the maximum No Fly Time I got last week was 25 - 26 hours following two or three days of four dives each (all EAN 32).

 

[DivemasterDennis]

After multiple days of multiple dives, Debbie and I end each trip with a full no dive day, and usually fly out the next morning. I have been on trips where one or more people want to get in "just one more dive, and do. They are usually ok. I choose not to take that risk, nor sprain my brain calculating the first moment I can safely ( or mostly safely) fly. Absent a combat situation or emergency air evacuation due to injury or illness ( so far no problems there), I choose to be conservative. However, I will be glad to have a formula expert handy to calculate my situation if I have to be airlifted to medical care in an emergency.
DivemasterDennis

 

[RonFrank]

I take a break from diving the day before a flight. I may dive in the AM if we leave the following day in the PM, but not normally. I see no reason to push any limits doing a recreational activity. If I need another day of diving the time to plan that is before the flight is booked. My puter generally clears in 18 hours, but I give myself 24+ hours. Why push limits? The other factor is this stuff is all theory and you are screwed when it happens. I know a woman who had a DCS incident coming home to CO from Blue Hole. Should not have happened but it did and who knows why....