To the pilots out there.......Flying 2 hrs after diving, but only to 1500 ft. OK?

[Searcaigh]

When I lived in Jeddah I had friends that lived in Taif and drove almost immediately back home to an altitude of 6,000 ft although not at the rate of 500 ft/ min. I have never heard of any DCS incident from them (not to say that it did not happen to other people)

My normal drive back from east coast UAE to Dubai takes me to around 1,000 ft above sea level, again with a slower rate of climb than 500 ft/min.

Personally I would see this as a very low risk if using maximum O2 content Nitrox for diving, and flying with a ceiling of 1,000ft

Here in UAE maximum altitude for private flying is 1,500 ft but I usually do this in the mornings when the air is cooler, and before diving in the afternoon.

 

[CoopAir]

I could even make the return flight back as low as 500 ft, but would prefer 1000-1500 as it would give me a bit more time to put out a mayday call and set up for a ditching if i lost power.

Air is my only option for diving here as nitrox is not available

 

[Searcaigh]

I have to practice stalls at 1,500 ft, so 1,000-1,500 should be okay IMHO.

Given no Nitrox available, is pure O2 available to breath post dive for 30 mins just to reduce risk, no idea if this would make any significant difference.

 

[CoopAir]

I have to practice stalls at 1,500 ft, so 1,000-1,500 should be okay IMHO.

Given no Nitrox available, is pure O2 available to breath post dive for 30 mins just to reduce risk, no idea if this would make any significant difference.

Yea, I've thought about that actually. No reason to think it wouldn't help (I know tech divers can go from very high letter groups to clean in 2 hrs on pure O)

Seems like it'd be a good idea to help off gas. Unfort, no O2 avail there, but I could probably get a 24 CF tank of aviation O2 and breath from that.

http://www.sportys.com/Pilotshop/product/13008

 

[ianr33]

Recommended rule for altitude diving is that you still wait the proper 12-18 hours. Just because you ascend to altitude higher after a dive and 6 hours clears you on tables it still isn't an accepted practice and doesn't count for flying after diving.

That makes NO sense to me. If this was planned as an altitude dove to 2000 feet,and he then flies at that height, he is not flying at all from a deco/n2 loading perspective.

If i was going to do this I would check the profiles in V planner putting in an elevation of 2000 feet. Also would dive nitrox if possible with computer set to air .

EDIT: Just checked this on V planner. With +2 conservatism NDL at 80 feet on air is 23 minutes. Changing the altitude needs a 1 minute deco stop depending on how you configure it. I think 2000 feet is a non event.

 

[CoopAir]

That makes NO sense to me. If this was planned as an altitude dove to 2000 feet,and he then flies at that height, he is not flying at all from a deco/n2 loading perspective.

If i was going to do this I would check the profiles in V planner putting in an elevation of 2000 feet. Also would dive nitrox if possible with computer set to air .

EDIT: Just checked this on V planner. With +2 conservatism NDL at 80 feet on air is 23 minutes. Changing the altitude needs a 1 minute deco stop depending on how you configure it. I think 2000 feet is a non event.

I was just pondering something along those lines. Since air is the only gas available, I could set my dive computer (Cressi Giotto) to "1 mountain" (2000 to 5000' elev) as well as the safety factor to 2.

Additionally, I could easily do 6+ minute safety stops at 15' instead of 3 min.

 

[XS-NRG]

That makes NO sense to me. If this was planned as an altitude dove to 2000 feet,and he then flies at that height, he is not flying at all from a deco/n2 loading perspective.

The point is he's NOT diving or planning at altitude though. You can't plan for an altitude dive but dive it at sea level. It's not valid. When you dive at say 2000 ft altitude then climb in a car to say 4000 ft you have residual nitrogen based on air pressure. It's a 4 pressure group increase. This increase results whether you dove prior to climbing or not. If you now wait 6 hours that pressure group will reduce to below an A on table and therefore consider you to be clear of any RNT........BUT......that only counts when you are then making another dive at altitude. If you aren't diving at altitude after you can't just wait 6 hours and be clear from a sea level dive. Also if you dive at altitude then wait 6 hours you can't expect that you can fly right away there either just because procedures say you are now below the charts.

I understand your point about diving at 2000 then descending and getting in an aircraft and only going as high as 2000 because technically it should still be the same but that's a dicey risk if you ask me. Using your theory you should then also be able to dive at 5000+ feet altitude then get in a plane and fly at 30,000 ft because the plane is pressurized to 5000 ft anyway. Clearly this isn't going to be the case and breaks every rule out there. Yes these are all book standards and everyone is different etc etc etc but I think the answer is clear. Either fly or dive, don't do both until you are clear from your table or computer (which accurately calculates your multi-level) and may reduce SIT time.

If the OP is going to be doing stalls (which is dangerous enough of a technique) then the answer is clear as day. DON'T DIVE!!! You need to consider the risk of injury of DCS/DCI, you need to consider if something happens during your stall and you can't recover properly you are going to crash and likely kill yourself. There are concerns with an airplane hitting structures and causing damage to life and property. There are rescue efforts that will need to be done. Firefighting will need to be done and don't forget environmental concerns of leaking oil, transmission fluid, jet fuel or avgas from a crash (hopefully not in the water). One final note, I can almost guarantee that if you have a problem, then crash and somehow live the NTSB will revoke your pilots license after finding out you disobeyed procedures for flying after diving yet took the risk anyway. It boils down to negligence and you already know the answer...the decision is yours. I know what I'd do/not do.

 

[wve]

Some have said that there is no problem ascending as high as 2000 ft right after diving where as others have said this unwise.

Is this an ACCEPTABLE risk in your opinion? Not a ZERO risk, but an acceptable one?

The only way to get ZERO risk is to not dive. Acceptable risk is a judgment call...

Using the NOAA Dive Table, an 80 ft dive for 25 min puts you in group F at the end of the dive. After a 45 min SI, you are still in Group F. The NDL for your 2nd dive to 40 ft would be 139 min. If you dive 50 min as you stated, your ending group would be K (because you have 61 min of residual nitrogen time; 50 + 61 = 111, and 40 ft for 111 min = group K).

The NOAA Diving Manual Table 4.3 says that for an ending Repetitive Group Designator of K, you need a SI of 4 hrs 37 min before ascending to 2000 ft altitude, or 3 hrs to ascend to only 1000 ft. So by extrapolation, an ascent to 1500 ft might be about 3.5-4 hours.

Of course, this is the conservative approach with lots of rounding that occurs when using tables, but it minimizes the risk enough to satisfy NOAA.

If one wanted to rationalize some other plan, one could argue that there is only a 7% difference in atmospheric pressure between sea level and 2000 ft, so how much more could the DCS risk be? The problem is that no one knows.

Diving is a bit of a crap shoot anyway. People break the rules and don't get bent. People follow the rules and wind up in chambers.

You may be a bit of a risk taker if you fly small planes...over water...where there are sharks... . The real question may be how ADDITIVE are the risks of diving combined with the risk of piloting a small plane over open water?

---------- Post added August 25th, 2013 at 04:26 PM ----------

I understand your point about diving at 2000 then descending and getting in an aircraft and only going as high as 2000 because technically it should still be the same ... Using your theory you should then also be able to dive at 5000+ feet altitude then get in a plane and fly at 30,000 ft because the plane is pressurized to 5000 ft anyway.

Actually, diving at 5,000 ft then flying in a cabin pressurized to 5000 ft would be okay as long as the plane doesn't suffer a sudden decompression. Most commercial planes are pressurized to 8000 feet, though, and that would be a problem because you would be "ascending" another 3000 ft from the altitude at which you performed your dive.

 

[HIGHwing]

You should post this question at StudentPilot.com rather than here. All this Nitrox this and that is interesting, but a 55-70nm crossing at drug-runner height through the ADIZ is certainly going to get you some attention.

The more pertinent factor is a 172 has a fixed gear. I submit that at 1,000-2,000 feet in an engine out scenario you cannot complete the engine restart/ditching checklist.

Forget it. Fly safer and modify your diving plans to suit your role and responsibilities as Pilot In Command. You should be making that crossing at a much higher altitude IMHO. I've done it many times. If you need life jackets, radio license, 12-inch tail numbers, customs stickers, or a life raft contact the FBO at KFPR and they will get you sorted out for a very nominal fee.

 

[CoopAir]

You should post this question at StudentPilot.com rather than here. All this Nitrox this and that is interesting, but a 55-70nm crossing at drug-runner height through the ADIZ is certainly going to get you some attention.

The more pertinent factor is a 172 has a fixed gear. I submit that at 1,000-2,000 feet in an engine out scenario you cannot complete the engine restart/ditching checklist.

Forget it. Fly safer and modify your diving plans to suit your role and responsibilities as Pilot In Command. You should be making that crossing at a much higher altitude IMHO. I've done it many times. If you need life jackets, radio license, 12-inch tail numbers, customs stickers, or a life raft contact the FBO at KFPR and they will get you sorted out for a very nominal fee.

You do realize that I'll NOT be crossing an ADIZ, right?????

It'll be a 30nm hop from Rum Cay to San Salvador (or Stellar Maris) which is UNCONTROLLED airspace.