I'm not suggesting anything. I'm stating that the actual incident probably didn't happen as you described, and it's irrelevant to the risk of flying after diving.
Why the wait to fly?
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Please read 5.6 and 5.7 on pages 66 and 67 of the following PhD Thesis:
Your thoughts about ejection and decompression sickness, because the ejected pilot is descending at the time, has one fallacy. That is the assumption that bubble formation takes time to develop. I had that misconception while in the USAF. We were flying a “duckbutt” mission (circling in a rescue HH-53C Super Jolly Green Giant helicopter) awaiting anything to happen to flights of aircraft on bombing raids while on a strike in North Vietnam. We were circling over Laos, at just over 10,000 feet altitude. It was hot inside the unpressurized helicopter, so I got out a can a root beer, and opened it. Instantly, it spurted its contents on everything around, including the helicopters ceiling. I ended up with only about a sip of root beer in that can. The bubble formation is instantaneous when the pressure is released.
The above thesis “Human Consequences of Agile Aircraft,” by David A Groggins, talks about decompression sickness happening to pilots during normal, rapid flight up to altitude in agile aircraft such as the F-22. Bubbles have been detected during these normal ops, because of the capabilities of the aircraft. If that can happen is a pressurized aircraft, then a pilot ejecting can also get decompression sickness.
SeaRat
hammet
Contributor
Not true. Okay, given a catastrophic yes. The FAA classifies three levels of decompression:
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_61-107B_CHG_1_FAA.pdf
(3) Types of Decompression.
(a) Explosive Decompression. A change in cabin pressure faster than the lungs can decompress. Most authorities consider any decompression that occurs in less than 0.5 seconds as explosive and potentially dangerous. This type of decompression is more likely to occur in small volume pressurized aircraft than in large pressurized aircraft and often results in lung damage. To avoid potentially dangerous flying debris in the event of an explosive decompression, properly secure all loose items such as baggage and oxygen cylinders.
(b) Rapid Decompression. A change in cabin pressure where the lungs can decompress faster than the cabin. The risk of lung damage is significantly lower in this decompression compared to an explosive decompression.
(c) Gradual or Slow Decompression. A gradual or slow decompression is dangerous because it may not be detected. Automatic visual and aural warning systems generally provide an indication of a slow decompression.
hammet
Contributor
Given the speeds required to sustain high altitude flight, I would think that
At 10000' your soda explodes yet commercial flights are pressurized to about 8000' and soda cans are routinely opened without incident. Hmmm....
Airplane
It's the one drink order that will undoubtedly annoy your flight attendant. Here's why.
BY CAROLINE HALLEMANN
At this point, experienced travelers (and germaphobes) know they should never ask for a cup of coffee or tea on an airplane, but this week, Travel + Leisure revealed that there's another drink order that annoys flight attendants intensely: Diet Coke.
The reason for their displeasure with the low-cal cola? It takes too long to pour.
According to flight attendant blog These Gold Wings, pressure in the plane cabin affects all soda, but none so much as Diet Coke. "As you may know, the aircraft cabin is not pressurized to sea level, but rather to the equivalent of about 7 or 8 thousand feet. This means some passengers might feel a little light headed or that alcohol effects them almost twice as much as it would on the ground. It also means soft drinks foam up a lot more when poured out of a can," explained the blog's author, who goes by the pseudonym "Jet."
"The worst culprit for this is Diet Coke. I literally have to sit and wait for the bubbles to fall before I can continue pouring. If all 3 passengers ask for diet coke I’ll often get them started, take another three drink orders, serve those, and then finish the diet cokes."
The writer even went so far as to say, "Pouring diet coke is one of the biggest slow downs in the bar service."
Altitude inside a pressurized commercial jet does affect the drinks.
SeaRat
OK, I read it. I don't see how it refutes my point.
A soda pop can is not a useful model for the human body. I have opened such cans in commercial aircraft pressurized to about 8,000 ft equivalent altitude without anything spurting out.
The RCAF has never operated the F-22 or anything like it. I understand that they have done some experimental high-altitude flights with CF-104 fighters, but the pilots wore pressure suits specifically due to the risk of loss of cabin pressure. So, I am still highly skeptical that an RCAF aviator ever actually got DCS during an ejection.
Okay, be highly skeptical. But realize that this was a publication that came from multiple sources and authors, not just the RCAF. If you’ll look at the authors of “Chapter 5, Physiological Consequences: Cardiopulmonary, Vestibular, and Sensory Aspects,” was written by three authors, H. Walsh, W. Albery, and W. Bles. W. Albert was representing the Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio. This is why there was discussion of the F-22.
Neither you nor I know what happened to the RAF pilot, except for what was said by him. I only presented this paper because it shows that what he claimed was possible, e.g. decompression sickness from an ejection, and had happened to others, even those who had not ejected.
SeaRat
So, I’ll do a 4 hour cave dive with an hour plus of deco and fly home 90 minutes later all the time. How?
I own the plane. I keep altitude under 4000’
But I’m the pilot and I own the plane.
If I had to worry about the pilot ascending or us losing cabin pressure, I wouldn’t do it.
I own the plane. I keep altitude under 4000’
But I’m the pilot and I own the plane.
If I had to worry about the pilot ascending or us losing cabin pressure, I wouldn’t do it.
fsardone
Solo Diver
^This
and also fly below 10,000’ and keep max differential pressure to 0’ cabin altitude … quick descent if loosing cabin pressure becomes an option.
NeverStopLearning
Registered
I assume I'm missing something, but:
Doesn't this make it far more likely that the divers in the 3, 6, and 9 hour groups who got DCS were already bent before the "flight?" If their supersaturation levels correlated to a GF99 of 97% upon surfacing, and only 38% (in the 3 hour case) upon "flying" they underwent far greater decompression stress upon surfacing than upon flying.
What this suggests to me is that relatively short intervals between flying and diving are perhaps sufficient to reduce DCS risk to well below what is generally assumed to be a reasonable level for diving.
Most divers like a certain level of conservatism, say a GF hi of 80, so assuming sufficient surface interval has passed that an 8000 foot pressurized cabin will result in a GF99 of under 80, then wouldn't flying be reasonable?
(All of this puts aside the idea that putting time between diving and flying allows time for DCS symptoms to manifest, treatment to be acquired, etc.)
In many ways, this makes sense considering that an 8000 foot cabin pressure corresponds to under 10 fsw in terms of pressure differential.
Where am I wrong? Why is a 12, 18, or even 24 hour wait time recommended given these factors?
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