Multiday dives and altitude

[fstrasz]

Our group is planning a trip to two dive resorts that are a reasonably far drive/travel apart. To minimize the travel, we were considering taking a chopper from the one resort to the next (making about 30-60 minute flight out of a 6 hour ordeal). If we did this and the chopper could stay under say 5000 ft, what would that do to our no fly times? I've read that each 1000' is equal to 2 PADI pressure groups. We'd like to end our dives by 3:00PM one day and then fly over to the other resort at 7:00AM the following morning. That would give us 16 hours of off gassing. Assuming a 22 hour no fly (based on recent multi dive trip), this would still leave 6 hours of no fly.

So, basically, I'm looking for some sort of formula to minimize the time we are not diving and still make it to the other resort without losing a day of travel/transfer.

Thanks!

 

[boulderjohn]

Our group is planning a trip to two dive resorts that are a reasonably far drive/travel apart. To minimize the travel, we were considering taking a chopper from the one resort to the next (making about 30-60 minute flight out of a 6 hour ordeal). If we did this and the chopper could stay under say 5000 ft, what would that do to our no fly times? I've read that each 1000' is equal to 2 PADI pressure groups. We'd like to end our dives by 3:00PM one day and then fly over to the other resort at 7:00AM the following morning. That would give us 16 hours of off gassing. Assuming a 22 hour no fly (based on recent multi dive trip), this would still leave 6 hours of no fly.

So, basically, I'm looking for some sort of formula to minimize the time we are not diving and still make it to the other resort without losing a day of travel/transfer.

Thanks!

The two pressure group per thousand feet is not used the way you seem to intend to use it. There really is not a good way to figure this at this time. Here are some points to consider:

The usual recommendation is to use 18 hours before flying for multiple dives.

The definition of flying is an elevation gain of 2,000 feet from your starting point. If you are talking about resorts at sea level, then you are exceeding that minimum.

Normal commercial aircraft are pressured to 7,000-8,000 feet. An unpressurized helicopter flying at 5,000 feet is not much different from a commercial jet.

 

[Bobyjimmie]

Look at it this way, no fly means no airplane right? Commercial airplanes pressurize their cabins between 5000 and 8000 feet usually closer to 6000. Helicopters dont pressurize their cabins because they dont fly very high and there is no need to so basically your flying in a plane which is a no go for 6 more hours? Your breaking the rules of no fly if you put it that way. Thats my opinion on it.

 

[The Chad]

Thats a pretty cool question.....I think you would have to know your Desat and flytime. Which for me comes off the VR3 screen (cuz I'm lazy) and of course and its related to the dive profiles I've done.

We done 200'+ multiple day dives at a place in NM 4000' and then have to drive over Raton pass 8600' I belive. Getting out of the water last time I had a desat of just over 2hrs, to get to the pass it's 3hrs so I off gased on the way.

I by no way am saying try it! We were using lots of different mixes too that affect desat. If your just diving air you really better do some checking around. I'm sure DAN would be interested in the results. It's really going to depend on the dive profiles you have and the mixes you use

 

[knotical]

So, basically, I'm looking for some sort of formula to minimize the time we are not diving and still make it to the other resort without losing a day of travel/transfer.

Break the problem into two parts. The simple part is the diving. If both resorts are at the same elevation (presumably sea level), you could simply dive as if you had remained at the same location.

For flying, you could use the Navy/NOAA ascent to altitude tables and methods mentioned in this post:
http://www.scubaboard.com/forums/2369525-post29.html
and other similar ones.
Using those tables should reduce your wait time before flying.
Also search on “altitude” within ScubaBoard and you’ll find lots of discussion.

 

[knotical]

and then have to drive over Raton pass

The Chad,
I was not aware of it until roakey pointed out in this post:
http://www.scubaboard.com/forums/959854-post16.html
that there is quite an elevation gain well before reaching Raton.
Blue Hole is at approximately 4600 feet.
Raton Pass is about 7835.
But Las Vegas is about 6430 feet, and
Romeroville, on the way to Las Vegas is about 6875.

So, you can see that about two-thirds of the elevation gain actually occurs in the first hour of driving.