Question-non-pressurized flying after diving

[Artimas]

I have a diving friend with a private plane that he wants to take on a dive trip. It is not pressurized. He flies as high as 12,500 feet on occasion.

Everything I've read about flying after diving involves airliners which are typically pressurized to 8,000 feet.

What changes (if any) should I make with regard to flying after diving if I'm going to go as high as 12,500 feet?

Thank you!

 

[SteveAD]

I would go with a wait time of 24 hours or longer before going to altitude, or go with one of funnest things about private aircraft--low level flying. Keep it under 500 feet and you can island hop between dives.

 

[Riger]

I have a diving friend with a private plane that he wants to take on a dive trip. It is not pressurized. He flies as high as 12,500 feet on occasion.

Everything I've read about flying after diving involves airliners which are typically pressurized to 8,000 feet.

What changes (if any) should I make with regard to flying after diving if I'm going to go as high as 12,500 feet?

Thank you!

Hello there,

Without going into the math/science of this;

Commercial Aircraft (High Fliers) do de-pressurize the aircraft to the equivalent of about 8000' during flight.

No-Fly times of the NDL tables or computer that you use is based on an assumed altitude of 8000' in a commercial aircraft (or slightly higher to allow for safety margins). Flying at 12500' will further reduce the outside pressure by 50% thus reducing the effect of the no-fly times and placing yourself at increased risk.

Whilst some may argue that there is sufficient margin built in on the NDL Tables or computers, I'd rather err on the side of safety in the scenario you describe and double the recommended no-fly time. This is based on the inverse proportion of the 50% reduction of the pressure you will fly at. (This is my opinion, and is not based on anything other than my understanding of the math. Use this at your own risk!!)

Best Regards
Richard (Riger)

 

[Riger]

..................... Keep it under 500 feet and you can island hop between dives.

There you go, that's the answer

Best Regards
Richard (Riger)

 

[bleeb]

Don't FAA regs require pilots to breat O2 when depressurized to 12500'? Any US pilots out there who know the exact limits and details?

On another note, the NOAA Ascent to Altitude table maxes out at 24 hours and 10000'. Not conclusive, I realize, but another clue.

 

[mavdog]

FAR 91.211
(a) General. No person may operate a civil aircraft of U.S. registry-
(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;

 

[Artimas]

Don't FAA regs require pilots to breat O2 when depressurized to 12500'? Any US pilots out there who know the exact limits and details?

On another note, the NOAA Ascent to Altitude table maxes out at 24 hours and 10000'. Not conclusive, I realize, but another clue.

What Mavdog said.

Not sure how much difference breathing O2 would make during the flight.

 

[SteveAD]

Supplemental O2 is to prevent hypoxia. At an altitude of 14,000 feet ppo2 of ambient air is low enough that significant reduction of a pilots faculties is likely.

 

[Riger]

What Mavdog said.

Not sure how much difference breathing O2 would make during the flight.

What Stevead said;

The Partial Pressure of 21% O2 would be very low at 12500' sucking a higher %O2 would increase the PPO2 sufficiently to reduce the risk of Hypoxia.

 

[bleeb]

Not sure how much difference breathing O2 would make during the flight.

Supplemental O2 is to prevent hypoxia. At an altitude of 14,000 feet ppo2 of ambient air is low enough that significant reduction of a pilots faculties is likely.

Like stevead said. IIRC, the first concern for pilots is reduction in visual capabilities resulting from hypoxia, particularly decreases in color recognition and night vision.

BTW, just so everyone has a sense of scale:
Sea level pressure = 101.3 kPa = 14.7 psi = 1 ata
5,000' = 84.3 kPa = 12.2 psi = 0.83 ata
8,000' = 75.3 kPa = 10.9 psi = 0.74 ata
10,000' = 69.7 kPa = 10.1 psi = 0.69 ata
12,000' = 64.4 kPa = 9.3 psi = 0.64 ata
13,000' = 62.0 kPa = 9.0 psi = 0.61 ata
15,000' = 57.2 kPa = 8.3 psi = 0.56 ata
http://www.flymetothemoon.com.au/content/Pressure to Altitude Conversion.pdf