No Fly Time

[Firebrand]

Question, If I go diving and restrict my depth to 20 FSW, and am underwater for 90 minutes, will I be safe to go recreational flying restricting my elevation to 10,000 feet of altitude after a three hour off-gasing period? Is there a model equation I can use to calculate the height restriction for flying? I know you SHOULD wait at least 24 hours before getting on a commercial airliner that cruises at 30,000, with a cabin pressure of equivalent to around 8,000 feet. Note, I am in Florida and will not be affected by having to fly over mountainous terrain. Thanks for your assistance.

 

[mempilot]

Here's the NOAA Ascent to Altitude chart.

After a dive to 20 (35 on the RDP), you'd exit in the Q pressure group, but after that surface interval of 3 hours, you'd be an A pressure group.

You should have no wait time to ascend to 10000ft after your SI.

 

[pete340]

Here's the NOAA Ascent to Altitude chart.

After a dive to 20 (35 on the RDP), you'd exit in the Q pressure group, but after that surface interval of 3 hours, you'd be an A pressure group.

You should have no wait time to ascend to 10000ft after your SI.

Hmm, I don't read it that way. In particular, NOTE 1 says to use the highest repetitive group indicator reached in the last 24 hours. So isn't it group Q, not A?

 

[mempilot]

Highest Repetitive Group, or what you would enter the tables at if you were going to do another dive at that moment.

If you used Q, you would be disregarding any surface interval credited.

 

[pete340]

Highest Repetitive Group, or what you would enter the tables at if you were going to do another dive at that moment.

If you used Q, you would be disregarding any surface interval credited.

Yup, makes sense to me: when you figure the minimum surface interval you don't take credit for the surface interval so far. Or, to come at it another way: if you come out of the water in group Q the table says you have to wait 24 hours. If you wait three hours, which gets you to group A, and then need no further surface interval, the table should say 3 hours for group Q.

 

[rab]

This has been interesting, but I've got one big question. Who's definition of "groups" are being used in the table? There seems to be some indication that the dives are being planned to PADI's RDP, but it doesn't look like the NOAA groups are defined the same way. Are those NAUI or SSI (or US.Navy) groups? (A..O,Z) (PADI includes P..Y also)

-Rob

 

[mempilot]

I'm posting a correction to my above post. This table is connected with the Navy's new No-Decompression Limit Air Tables published in 1999, and they refer to any PG as a Repetitive Group.

Therefore, Pete is correct with this table, in that you would use the highest Group encountered during the day, but for this dive it would be:

20fsw for 90 minutes is a Group D, and the SI before ascent to 10,000 feet would be 12 hours and 52 minutes.

I have another set of tables that I use based on M values upon exit, followed by a SI, then an ascent to altitude.

Sorry for the confusion.

 

[pete340]

This has been interesting, but I've got one big question. Who's definition of "groups" are being used in the table? There seems to be some indication that the dives are being planned to PADI's RDP, but it doesn't look like the NOAA groups are defined the same way. Are those NAUI or SSI (or US.Navy) groups? (A..O,Z) (PADI includes P..Y also)

mempilot said it's NOAA's table. That means it's NOAA's groups, too.

 

[mempilot]

mempilot said it's NOAA's table. That means it's NOAA's groups, too.

I posted the wrong Ascent to Altitude table. The one I posted is NOAA, but it refers to the Navy No Decompression table pressure groups.

Sorry about the confusion.

Coming out of the Navy tables a Group B would allow you to fly to 10k feet within a couple of hours. You would need to limit your dive to about 50 minutes.

 

[pete340]

The one I posted is NOAA, but it refers to the Navy No Decompression table pressure groups.

I should look it up, but you may know offhand: does NOAA also have its own set of tables with its own set of pressure groups, or do they work off the Navy tables?