Flying In Police Helo after diving

[AustinPDDiver]

Hey fellow public safety officials, I have a question, Im doing a 30ft max fresh water dive on saturday morning, not a very long dive just an OW checkout. The problem is that Im flying as a crew member on our helo saturday night, our altitude doesnt usually exceed 2000 feet. Does anybody have any experience with this, or think that this might put me at risk?

Thanks,

Ryan

[Deep Lake]

Call DAN @ (919)684-2948

[MyDiveLog]

I agree with the suggestion to call D.A.N. for safety's sake, but would add that it doesn't seem like much of a risk.

If my memory serves, the atmosphere extends for about 40,000 feet, which would mean that 2000 feet is about 5% of an atmosphere, or like a rapid ascent of less than 2 feet in sea water.... not a big concern. You mentioned that you wouldn't be down long or deep, so you won't have much N buildup anyway. Finally, the single-dive "no fly" time recommendation is 12 hours. You said you were diving in the morning and flying in the evening, which means you'll off-gas for most or all of 12 hours anyway. I wouldn't worry much. Now, if you were doing a deep, long dive, I might be a bit more cautious...

[opiniongirl]

I dunno about it - even over 1,000 feet it's still considered altitude, so unless there is a 12 hour SI you're still at higher risk of DCI - and it would be pretty embarrassing to get bent in the chopper in that situation pushing the limits...

So you would be at increased risk...without a longer SI.

[AustinPDDiver]

Hey guys, took your advice and called DAN, they stated that in their opinion, diving to 30ft or less, and an altitude not exceeding 2000 ft, and a SIT of around 7hrs, I was within the guidlines for being able to fly. Thanks for the Suggestions

Ryan

[caveseeker7]

If you're certified for it and it's available, consider using the highest O2% Nitrox available, as it will reduce your tissue loading and speed up off-gassing.

[Gary D.]

Hey guys, took your advice and called DAN, they stated that in their opinion, diving to 30ft or less, and an altitude not exceeding 2000 ft, and a SIT of around 7hrs, I was within the guidlines for being able to fly. Thanks for the Suggestions

Ryan
You can't just throw out numbers like that because your home altitude has to play in as well. Did you give DAN that info?

Using your same numbers for us wouldn't work. We have and will again, I'm sure, dive to several atmosphere's and fly to between 3000 and 4000 feet. Driving sometimes gets us much higher than that.

Gary D.

[BigJetDriver]

Using your same numbers for us wouldn't work. We have and will again, I'm sure, dive to several atmosphere's and fly to between 3000 and 4000 feet. Driving sometimes gets us much higher than that.
Gary D.

Flying after diving is ALWAYS a balancing act. It is always a case of the amount of inert gas loading versus the amount of time to off-gas versus the amount of pressure drop versus time. Thanks to DAN's recent studies, their recommendations are much more up to date than any of the other agencies.

One must always remember that it is a game of procedures based on statistics. Any individual can fall outside the parameters on any given day for a myriad of reasons.

In any case, diving for significant time periods and then ascending to 4000 feet msl immediately afterward is NOT a good idea, and WILL lead to someone getting bent! Just because it has not happened YET means absolutely nothing, I am sorry to say! I hope someone will reconsider that idea before it happens! :11:

[AustinPDDiver]

Gary, Flying to 1000 feet is 1000 feet..... our local field elevation is like 596....so 1000 MSL is about 400 agl....we try to stay around 1000 agl (above ground level) which puts us around 1600 MSL (mean sea level.) DAN told me that as long as we didnt go above 2000 MSL I should be ok.


Ryan

[lamont]

If my memory serves, the atmosphere extends for about 40,000 feet, which would mean that 2000 feet is about 5% of an atmosphere, or like a rapid ascent of less than 2 feet in sea water.... not a big concern.


The density of the atmosphere isn't constant, so that going 5% of the distance to the 'top' of the atmosphere is going to cover more than 5% of the mass of the atmosphere and result in more than a 5% pressure drop.

I've also flown in a plane at 55-60,000 feet...

I just dug up some altitude-pressure tables though and it looks like at 2000 feet you're at 706 mm Hg which is .93 ata, so the correct figure looks to be 7%...

8000 feet is 564 mm Hg which is .74 ata or 8.6 fsw. Funny that it can take a 12-18 hour "deco stop" at 1 ata in order to be able to ascend another 8-9 fsw in a plane...

[Gary D.]

What I was refering to is for us to fly 1000 feet after a dive we would have to dig a 1500 foot hole. A 1000' flight in Denver is over 6000'.

A 1000' flight for us is in reality 3500'. Just driving from one side of our second biggest lake to the other puts us at a min of 3100' which is 950' above the lake.

Gary D.