Dive planner says a S.I. of 3 hours put me in NDL Group A??

[codeblue2k]

My wife and I are just about to finish up with out Open Water cert. But due to water conditions we have to put off our last dive until the day right before we fly out to Mexico. Since we have two full tanks of air we thought that we would do the last dive and then one fun dive. But onto my question, I used our dive planner and put in two dives (depths are the max we will go, but most of the dive time we will be around 30ft):

Dive 1: Depth 50ft - Time 35mins
S.I.: 1 hour
Dive 2: Depth 50ft - Time 35mins​

Now the dive planner says after the second dive and a 3 hour S.I. we should be back in NDL group A. Does that sound right? Does that technically mean that we could fly anytime after 3 hours? Now we will in reality we will have a 16 hour S.I. before taking off. But im just wanting to get a grasp on this whole flying after diving thing and what the dive-planner is trying to tell me.

I do know that PADI and DAN say that 12 hours for a single dive and 18 for multiple dives is suggested. But when they make that recommendation are they including dives that are 100ft and an hour long? If we do the two dives stated above, we wont hit that 18 hour mark. Any help you can give a newbie diver would be much appreciated.

 

[Blackwood]

I don't believe there are any conclusions to be drawn about flying from the "pressure group." Flying wasn't considered anywhere in the algorithm.

Personally I'd not worry about it (especially given the 16 hours before your flight), but I won't make that recommendation to anyone.

 

[codeblue2k]

I don't believe there are any conclusions to be drawn about flying from the "pressure group." Flying wasn't considered anywhere in the algorithm.

Personally I'd not worry about it (especially given the 16 hours before your flight), but I won't make that recommendation to anyone.

Agreed the 16 hours should be long enough. But im just trying to get a grasp on the pressure group. If it says that im in group A does that mean I should be good to fly?

 

[Pearldiver07]

Agreed the 16 hours should be long enough. But im just trying to get a grasp on the pressure group. If it says that im in group A does that mean I should be good to fly?

No, Don't confuse your nitrogen loading with regard to dive exposure limits (i.e., what you calculate on the table) with your nitrogen loading prior to flying.

PG "A" does not mean you're clear. Remember that these are merely mathematical models, not directly calculating what excess nitrogen is left in your body, and just as importantly, where it may be in your body.

Although I would agree that a low loading and a 16-hour interval are in all likelyhood safe, don't infer the belief that simply being a PG "A" means that your Nitrogen loading is low enough to fly.

I always recommend taking the more conservative approach. In this case, follow the DAN guidelines of 18 hours after multiple dives. Any personal decisions you make reducing these margins needs to be an informed decision, because if you get bent, you made the decision to shave off of the recommended guidelines. You get to ride the chamber, and you get to foot the bill (unless you have DAN insurance - plug for them is intended to be blatant).

But in any regard, have fun and enjoy your vacation.

 

[tkdgodess]

My Padi RDP says 1. wait a minimum surface interval of 12 hours prior to ascent to altitude..the rules are printed below table 3.

Being in pressure group A does not mean it's OK to fly. As a pressure group A you still have residual nitrogen. If you ended up pressure group z after a dive, then waited 3 hours you'd be a pressure group A. The Pressure Group Letters are representitive of the nitrogen you have left in you after a dive.

Follow the current flying after diving guidelines.

 

[oly5050user]

Agreed the 16 hours should be long enough. But im just trying to get a grasp on the pressure group. If it says that im in group A does that mean I should be good to fly?

If you are going by the book, then no, you must wait 18 hours..realistically probably ok.I have to advise to wait the 18hrs.
If you go by the old US Navy tables,and recommendations from back in the day ,you had to wait till pg "D:" or less. PG's from Navy tables and RDP DO NOT work together.Based on different half times.

 

[Blackwood]

If it says that im in group A does that mean I should be good to fly?

Again, "Flying wasn't considered anywhere in the algorithm."

A "pressure group" is meaningless out of the context of a specific repetitive dive table.

 

[muddiver]

Using the U.S. Navy No-Decompression Air Diving Tables on Pg. 9-62 of the U.S. Navy Diving Manual, Rev. 6, the dives are as follows:

Dive #1 50 feet sea water/for 35 minutes 35) the Repetitive Group Designation (RGD) = F

Surface Interval of :60 the RGD = E

Dive #2 50'/:35 the RNT = :35 added to the Bottom Time of :35 the Total Time of Dive is :70 so the RGD = J

Using the "Required Surface Interval Before Ascent to Altitude After Diving" Table on Pg. 9-61 the SI should be 14:13 for a "J" diver.

Your 16 hour period before your flight is ok.

 

[Blackwood]

Using the U.S. Navy No-Decompression Air Diving Tables on Pg. 9-62 of the U.S. Navy Diving Manual, Rev. 6, the dives are as follows:

Dive #1 50 feet sea water/for 35 minutes 35) the Repetitive Group Designation (RGD) = F

Surface Interval of :60 the RGD = E

Dive #2 50'/:35 the RNT = :35 added to the Bottom Time of :35 the Total Time of Dive is :70 so the RGD = J

Using the "Required Surface Interval Before Ascent to Altitude After Diving" Table on Pg. 9-61 the SI should be 14:13 for a "J" diver.

Your 16 hour period before your flight is ok.

... based on only two dives, when it's clear from the OP that these are the last two in a series.

 

[codeblue2k]

My Padi RDP says 1. wait a minimum surface interval of 12 hours prior to ascent to altitude..the rules are printed below table 3.

Being in pressure group A does not mean it's OK to fly. As a pressure group A you still have residual nitrogen. If you ended up pressure group z after a dive, then waited 3 hours you'd be a pressure group A. The Pressure Group Letters are representitive of the nitrogen you have left in you after a dive.

Follow the current flying after diving guidelines.

No, Don't confuse your nitrogen loading with regard to dive exposure limits (i.e., what you calculate on the table) with your nitrogen loading prior to flying.

PG "A" does not mean you're clear. Remember that these are merely mathematical models, not directly calculating what excess nitrogen is left in your body, and just as importantly, where it may be in your body.

Although I would agree that a low loading and a 16-hour interval are in all likelyhood safe, don't infer the belief that simply being a PG "A" means that your Nitrogen loading is low enough to fly.

I always recommend taking the more conservative approach. In this case, follow the DAN guidelines of 18 hours after multiple dives. Any personal decisions you make reducing these margins needs to be an informed decision, because if you get bent, you made the decision to shave off of the recommended guidelines. You get to ride the chamber, and you get to foot the bill (unless you have DAN insurance - plug for them is intended to be blatant).

But in any regard, have fun and enjoy your vacation.

Got it! Thanks for clearing that up. Group A means nothing when it comes to flying. And in the case of this dive that im donig, 16 hours S.I. should be ok before flying? Ill make sure we stay well hydrated