Diving and flying

[sharkbait13]

just wondering if anybody would like to take a shot at saying with resonable certainty to what altitude one can safely fly within a couple of hours of doing two no deco dives.
as a dive instructor and helicopter pilot i would like to start combining the two and not have to wait 12hrs before flying home.
would it be reasonably safe to fly say under 1200 feet?
i have in the past dove and then driven over a mountain pass at 1500feet with no ill effects.
having trouble finding anything on the subject of low level flying after diving.

commercial airlines are pressurized to 8000 feet hence a definite risk of DCS.

any thoughts would be muchly appreciated as i would rather learn from other peoples blunders.

 

[Tigerman]

Keep in mind that with flying you tend to ascend to altitude faster than you would when driving in most cases..

 

[bleeb]

One reference you might like to try is the NOAA tables. See the Required SI Before Ascent to Altitude table. Be careful that the letter groups are from the No-Deco Air Table and are not necessarily compatible with anyone else's letter groups (PADI, NAUI, USN, etc.)

For your specific example of a couple of no-deco dives, two hours and 1200 feet altitude, using these tables it could go either way and depends on the exact profiles. Short and deep is actually better than long and shallow.

 

[sharkbait13]

One reference you might like to try is the NOAA tables. See the Required SI Before Ascent to Altitude table. Be careful that the letter groups are from the No-Deco Air Table and are not necessarily compatible with anyone else's letter groups (PADI, NAUI, USN, etc.)

For your specific example of a couple of no-deco dives, two hours and 1200 feet altitude, using these tables it could go either way and depends on the exact profiles. Short and deep is actually better than long and shallow.

Bleeb

thanx for the reply had a quick glance at the tables you included gives me a good starting place.

Sharkbait

 

[wve]

Great question, and very interesting to think about!

However, my short answer is: No one knows. It's all theory.

There are some data upon which the theories are built, but data about groups of people do not necessarily translate into what will happen to an individual.

Next best answer: It depends.

If the dive profile suggests that you primarily loaded the fast compartments (short, deep dives) rather than the slow compartments (long, shallow dives), then you may be able to get away with a shorter interval before flying because the fast compartments also off-load more quickly.

A person may also be able to hedge by minimizing altitude because 1000 ft of altitude only lowers the partial pressure of nitrogen by about 2%. That difference may be small enough to avoid DCS. But again, who knows?

Practical answer: If one's computer still shows ticks in the nitrogen bar graph display, you are safest to stay put.

Getting DCS while someone else is flying is one thing. Getting it when you are the pilot could have devastating consequences.

 

[sharkbait13]

Great question, and very interesting to think about!

However, my short answer is: No one knows. It's all theory.

There are some data upon which the theories are built, but data about groups of people do not necessarily translate into what will happen to an individual.

Next best answer: It depends.

If the dive profile suggests that you primarily loaded the fast compartments (short, deep dives) rather than the slow compartments (long, shallow dives), then you may be able to get away with a shorter interval before flying because the fast compartments also off-load more quickly.

A person may also be able to hedge by minimizing altitude because 1000 ft of altitude only lowers the partial pressure of nitrogen by about 2%. That difference may be small enough to avoid DCS. But again, who knows?

Practical answer: If one's computer still shows ticks in the nitrogen bar graph display, you are safest to stay put.

Getting DCS while someone else is flying is one thing. Getting it when you are the pilot could have devastating consequences.

i know that medivacs will fly at very low altitude when transporting DCI cases to the chamber but they are nowhere near the 1000 foot range.
there has to be studies on the subject somewhere. surely someone was foolish enough to experiment with this theory at some point otherwise we wouldnt know what we know today.
trouble is finding the results unless they are like u say only theoretical at this point.

PADI's short answer is no but they tend to lean towards the side of extreme caution. more of a CYA ( cover your a##s)situation.

so the search continues as u say as the pilot i cannot afford to possibly take a DCS hit while flying.

 

[SteveAD]

It also depends on the dive profile. Are you talking about a couple of 20-30 minute dives to 80-100 feet (heavily loading fast tissues) or a couple of 50-60 minute dives to 20-40 feet (moderately loading slow tissues)?


The safe answer is don't fly after diving. Anything other than that is up to the individual.

 

[wve]

surely someone was foolish enough to experiment with this theory at some point otherwise we wouldnt know what we know today.

DAN was actually doing some research on this. This article on the DAN website explains why the information is hard to come by. The article dates to 1995, so there may have been some results published. I'll be looking.

I also found this article which says that you can fly 2 hours after diving if:

1. your diving is restricted to no-decompression dives, and
2. your total dive time does not exceed 1 hour in the previous 12 hours, and
3. your altitude (cabin pressure) will be less than 2000 ft.

These latter recommendations were developed for commercial divers. I'm not sure how they would differ from recreational divers except that the dive profiles between commercial and recreational divers may be quite different.

 

[DocVikingo]

Hi wve,

Short answer; Next best answer; Practical answer.

Nicely done and useful.

Thanks,

DocVikingo

 

[wve]

I found that there is much good discussion on this topic at the DAN website.

The results of the DAN Flying after Diving (FAD) study that I mentioned in my previous post can be found here. After all has been said and done, DAN still recommends a 12 hour surface interval for divers who plan to fly commercially (with cabins usually pressurized to 8,000 ft).

If you are a DAN Member, you can also access the proceedings of the Flying After Recreational Diving Workshop which was held in May 2002. Check out the Executive Summary where it talks about flight altitudes.

It says that the U.S. Navy had used 2,300 ft as its threshold for many years without incident. Participants agreed that 2,000 ft was a reasonable, though uncertain, threshold below which restrictions on flying should not be necessary.

The uncertainty stems from lack of experimental data even though there are ample historical data to suggest that the 2,000 ft ceiling may be safe. And again, this is no guarantee that DCS will not occur -- just an assessment of risk.