Question about flying before and after diving ?( private pilot instructor )

landonnin1 · Jul 10, 2011

I hope this is in the right place
I have someone that just went through class and pool work .Now they want to go to gilboa Ohio but he is a private pilot instructor and owns a few planes.He wants to fly down on sat and do his 2 dives then fly home to Michigan , then fly back down on sunday for his other 2 dives then back home.now in the course book it says wait 12 hr after one dive and 18 after 2 but I believe this is a commercial flight .He did say the he does not go over 3500 ft for a trip like this. could someone please help me out on this ? or PM me so we can talk in more detail
thank you
Matt

Mossman · Jul 10, 2011

You're right, the standards are based on a commercial flight using 8,000 feet of pressurized cabin "altitude". Also, these flights gain altitude faster than a small plane would, increasing the chance of oversaturating the tissues with nitrogen. Furthermore, the depths might not exceed 30 feet on his checkout dives, thus less nitrogen will be absorbed than on deeper recreational dives. Finally, checkout dives are likely to be short.

The 1999 USN table found here : http://scuba-doc.com/FADDEMA2002.ppt (slide 34) requires no pre-flight surface interval before ascending to 4,000' for repetitive groups A-F. After the sort of dives he'll be doing, it's highly likely he'd exceed repetitive group F. G can be done after a 1:23 interval and H after a 3:26 interval. There will be some surface interval because he's not climbing out of the water directly into a moving plane.

That said, it's probably not a good idea. He might suffer other issues such as ear trauma that could affect his ability to fly safely (without vertigo). And even if statistically he's practically 100% safe, he'll be alone in the plane if anything does happen. Obviously any condition that might render him unconscious or physically incapacitated would be quite fatal if he's in the pilot's seat at 3,500'.

Jim Lapenta · Jul 10, 2011

Why would anyone even chance something like this? His plane is likely not pressurized like a commercial plane. His plan is not to go over 3500, what if he runs into a thunderstorm that forces him to go over it? It also sets a bad example for others. As an instructor I would advise my student not to do it. Telling them its ok would to me be like telling them to forget all that useless junk about staying with your buddy, not holding your breath, etc. The rule is no flying and doing it between dive days is just stupid. If he can afford to fly down both days he can afford to be safe and drive down, get a room for the night, and drive home. Sounds like more money than sense.

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landonnin1 · Jul 10, 2011

Mossman thank you for the PP.Jim Lapenta I am with you but before I flat out told he no I wanted to check into it first as I have not ran in to this before.
He is only able to do 2 dive per day per our standards
Now I know I can not tell him he can't fly but I know I can say no about doing the dives to certify him
thank you for all the info
Matt

DevonDiver · Jul 11, 2011

This is the sort of situation that would be debateable if your friend was considering being a passenger on a non-commercial flight at that altitude.

However, for a pilot to take that chance (and risk becoming incapactitated when in control of an aircraft) I don't think it should ever be considered.

This isn't a judgement call solely based upon your friend's attitude towards their own safety; it must include the risk to passengers (if any), other aircraft...and even people on the ground (should the plane crash).

Mossman · Jul 11, 2011

DevonDiver:
This is the sort of situation that would be debateable if your friend was considering being a passenger on a non-commercial flight at that altitude.

However, for a pilot to take that chance (and risk becoming incapactitated when in control of an aircraft) I don't think it should ever be considered.

This isn't a judgement call solely based upon your friend's attitude towards their own safety; it must include the risk to passengers (if any), other aircraft...and even people on the ground (should the plane crash).

I was trying to find whether the FAA addressed the issue or not. Unfortunately, they only phrase it as a recommendation AFAIK, but since their recommendation is 12 hours for "up to 8,000 feet", that's the number a wise pilot would use. If there were any sort of accident, violating the FAA's recommendation probably wouldn't look so good:
d. Decompression Sickness
After Scuba Diving.

1. A pilot or passenger
who intends to fly after scuba diving should allow the body sufficient time to
rid itself of excess nitrogen absorbed during diving. If not, decompression
sickness due to evolved gas can occur during exposure to low altitude and create
a serious inflight emergency.

2. The recommended
waiting time before going to flight altitudes of up to 8,000 feet is at least
12 hours after diving which has not required controlled ascent (nondecompression
stop diving), and at least 24 hours after diving which has required controlled
ascent (decompression stop diving). The waiting time before going to flight
altitudes above 8,000 feet should be at least 24 hours after any SCUBA dive.
These recommended altitudes are actual flight altitudes above mean sea level
(AMSL) and not pressurized cabin altitudes. This takes into consideration the
risk of decompression of the aircraft during flight.

http://www.faa.gov/air_traffic/publications/ATpubs/AIM/Chap8/aim0801.html

Thalassamania · Jul 11, 2011

A few points:

It is always best to wait.
I believe that recent recommendations permit an ascent to 2,700 feet after diving.
Two hours of 100% oxygen, breathed at the surface should set you up for an ascent as high as 8,000 feet, as long as you are in USN Group N of less.
In the old days believed that an ascent to 500 feet was all that was permitted, I burned a lot of extra fuel as I flew back from the Channel Islands at 500 feet, it's expensive and nerve-wracking.

Mossman · Jul 11, 2011

Thalassamania:
A few points:

It is always best to wait.

I believe that recent recommendations permit an ascent to 2,700 feet after diving.

Two hours of 100% oxygen, breathed at the surface should set you up for an ascent as high as 8,000 feet, as long as you are in USN Group N of less.

In the old days believed that an ascent to 500 feet was all that was permitted, I burned a lot of extra fuel as I flew back from the Channel Islands at 500 feet, it's expensive and nerve-wracking.

Finally, a minimum threshold altitude below which guidelines were unnecessary was

discussed. Although no data were available that specifically addressed the question, a

previous publication had suggested that restrictions were unnecessary below a threshold

altitude of 2,300 feet (701 meters). The U.S. Navy Diving Manual had followed this

recommendation without apparent problem until introduction of the 1999 procedures that

reduced the threshold to 1,000 feet (305 meters) for internal consistency. The

workshop participants agreed that 2,000 feet (610 meters) was a reasonable, if uncertain,

threshold, as no problems with 2,300 feet were cited.

http://www.diversalertnetwork.org/research/projects/fad/workshop/FADWorkshopProceedings.pdf - pp. 12-13

Thalassamania · Jul 11, 2011

Thanks for the correction.

Question about flying before and after diving ?( private pilot instructor )

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