Why the wait to fly?

[tursiops]

EON Core set to "aggressive". I always adhere to at least an 18 hour rule, but depending on the surface intervals between dives, etc. and how the dives are spaced out, it can sometimes be on the very low end for a no fly window.

So the computer is desaturatured, and can fly.

 

[oya]

If the plane were to lose cabin pressure at altitude, there is potential to get bent.

To be fair, if the plane were to lose cabin pressure at altitude, there is the potential to smash into the Earth at 500mph, too.

 

[oya]

There's a dive site here, Nohoch. The average depth is 12 feeth. You can be there for hours, but it's only 12 feet.

Breathing 32%.
Apply Dalton's triangle and you wind up with a PN2 of 1. Only a shade above normal atmosphere. So, in theory, you couldn't possibly ongas a ton. And could, in theory, drive straight to the airport after a dive there.

I'm not going to. Nor, do I imagine, will any of you.

 

[Nick_Radov]

I think that's a risk at cruising altitude. When I went for my interview for a NEXUS pass, the Canadian official was an ex-air force pilot who had a mechanical failure (I didn't ask what altitude) who ejected and got bent.

I am skeptical of this story, or there may be a misunderstanding about terminology. Bubbles don't form instantaneously. A typical ejection sequence will involve a stabilized free fall down to about 15000 ft where the main parachute opens. That happens very quickly. Unless the aircraft was cruising much higher than the typical 40000 ft maximum for civilian airliners, in which case military pilots typically prebreathe pure oxygen specifically to reduce DCS risk.

Ejection can cause traumatic injuries with symptoms that could be mistaken for DCS. Rapid decompression can also cause barotrauma injuries that are not DCS (bends). Unless the subject of this story experienced immediate symptom relief upon taking a recompression chamber ride I doubt he was really bent.

 

[tursiops]

The average depth is 12 feeth.

On-gassing is not a function of average depth.

 

[Billg68bg]

Why risk it. A short moment of fun could have a lifetime of implications. Including shortening said life. Don’t know enough about the science of it, but I’d err in the side of caution.

 

[DiveProKoko]

So the computer is desaturated, and can fly.

Haha! Yes it is!

 

[John C. Ratliff]

I am skeptical of this story, or there may be a misunderstanding about terminology. Bubbles don't form instantaneously. A typical ejection sequence will involve a stabilized free fall down to about 15000 ft where the main parachute opens. That happens very quickly. Unless the aircraft was cruising much higher than the typical 40000 ft maximum for civilian airliners, in which case military pilots typically prebreathe pure oxygen specifically to reduce DCS risk.

Ejection can cause traumatic injuries with symptoms that could be mistaken for DCS. Rapid decompression can also cause barotrauma injuries that are not DCS (bends). Unless the subject of this story experienced immediate symptom relief upon taking a recompression chamber ride I doubt he was really bent.

I don’t think you’ve done your homework on this one.

Loss of cabin pressurization in U.S. Naval aircraft: 1969-90.​

Bason R 1,
Yacavone DW

Author information​

Aviation, Space, and Environmental Medicine, 01 May 1992, 63(5):341-345
PMID: 1599378

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Abstract​

---

During the 22-year period from 1 January 1969 to 31 December 1990, there were 205 reported cases of loss of cabin pressure in US Naval aircraft; 21 were crew-initiated and 184 were deemed accidental. The ambient altitudes varied from 10,000 ft (3048 m) to 40,000 ft. (12192 m). The most common reason for crew-initiated decompression was to clear smoke and fumes from the cockpit/cabin (95%). The most common cause for accidental loss of cabin pressure was mechanical (73.37%), with aircraft structural damage accounting for the remaining 26.63%. Serious physiological problems included 1 pneumothorax, 11 cases of Type I decompression sickness, 23 cases of mild to moderate hypoxia with no loss of consciousness, 18 cases of hypoxia with loss of consciousness, and 3 lost aircraft with 4 fatalities due to incapacitation by hypoxia. In addition, 12 ejections were attributed to loss of cockpit pressure. Nine of the ejections were deliberate and three were accidental, caused by wind blast activation of the face curtain. Three aviators lost their lives following ejection and seven aircraft were lost. While the incidence of loss of cabin pressure in Naval aircraft appears low, it none-the-less presents a definite risk to the aircrew. Lectures on the loss of cabin/cockpit pressurization should continue during indoctrination and refresher physiology training.

Europe PMC

Europe PMC is an archive of life sciences journal literature.

europepmc.org

Jersey SL, Hundemer GL, Stuart RP, West KN, Michaelson RS, Pilmanis AA. Neurological altitude decompression sickness among U-2 pilots: 2002–2009. Aviat Space Environ Med 2011; 82:673–82.

Introduction: Compared to the previous 47 yr, U-2 pilots reported an increased number of altitude decompression sickness (DCS) incidents with central nervous system (CNS) manifestations during 2002–2009. Due to increasing incident severity during military operations, the U.S. Air Force initiated an investigation to prevent future mishaps. Methods: We retrospectively examined all neurological DCS cases observed among U-2 pilots during 2002–2009. Urgency to prevent further pilot losses limited this study to using existing, often incomplete data sources. Results: During 2002–2009, 16 confirmed incidents of CNS DCS occurred with 13 pilots, plus 4 possible incidents with 4 pilots. Significantly, 12 of 16 confirmed incidents occurred at 1 operating location, including 4 of 5 life-threatening cases. This series of cases were of a type and severity rarely found in flight operations and correlated temporally with increased sortie frequency/duration associated with combat operations. Multiple investigations confirmed no defects in aircraft, support equipment, or oxygen supplies. Nor were significant trends observed with age, habitus, environmental exposure, medication use, or cardiac defects. In 11 cases, symptom recognition occurred well after the 4-h point where clinical experience indicated risk should stabilize. Symptoms also recurred days later and responded to repeat hyperbaric oxygen therapy in three of four cases. Finally, neuropsychiatric symptoms persisted in six pilots for years and may represent permanent injury. Conclusions: An increase in U-2 CNS DCS cases probably resulted from more cockpit activity combined with longer, more frequent high-altitude exposures. Adjustments in preoxygenation, cabin altitude, exercise at altitude, and frequency of flights may reduce incidence.

Neurological Altitude Decompression Sickness Among U-2 Pilots: 2002–2009​

Neurological Altitude Decompression Sickness Among U-2 Pilots: 20...: Ingenta Connect

www.ingentaconnect.com

Hypobaric decompression sickness​

Ann Whitfield, Carlos D Scheinkestel, Ian L Miller, D Jamie Cooper, David V Tuxen
First published: March 1995

Abstract​

The Royal Australian Air Force (RAAF) mimics emergency aircraft decompression and hypoxia in a chamber decompressed over two to six minutes to a simulated altitude of 25,000 feet (7500m). Air crews in the chamber are trained to use oxygen apparatus including positive pressure breathing systems under these conditions. Over a seven year period, the RAAF has performed approximately 2500 subject decompressions and the Alfred Hospital Hyperbaric Service has treated 11 patients suffering decompression sickness (DCS) following this hypobaric exposure.

The 11 patients (eight males, three females, mean age 26±4 years) presented with typical DCS, with joint pains (9), paraesthesiae (7) and concentration and memory deficits (6). One had major neurological deficits including ataxia and dysarthria. Patients required a mean of seven treatments (range 2–25) to a depth of 18m on 100% oxygen. Two patients with refractory symptoms were recompressed with a 50: 50 mix of helium and oxygen and the patient with severe neurological deficit required recompression to 30m.

Nine patients had complete resolution of DCS with treatment, one patient resolved fully by one month after treatment, the patient with more severe neurologic deficit recovered completely by 12 months and one patient with persistent mild sensory deficits was lost to follow-up by the Alfred Hospital. There were no major differences in presenting symptoms, number of treatments, or outcome between these patients and 422 treated patients suffering DCS following diving over the same time period.
DCS may occur with exposure to high altitude. The severity and treatment is similar to that occurring following diving. Resolution of symptoms and signs may be achieved by recompression therapy.

https://onlinelibrary.wiley.com/doi/full/10.1111/j.1442-2026.1995.tb00184.x

SeaRat

 

[Nick_Radov]

I don’t think you’ve done your homework on this one.

I've done my homework. None of those articles refute my comment.
Everyone understands that if the cabin depressurizes at high altitude and remains there for several minutes then there is a risk of DCS. But the story above was about ejecting, which involves an immediate descent to lower altitude where DCS is highly unlikely.
The RCAF has never operated the U-2, or any other aircraft that cruises at extreme altitudes.
I wouldn't be surprised if several RCAF pilots have suffered some form of barotrauma injuries as a result of high altitude ejections, I'm just skeptical that they were ever properly diagnosed with DCS (bends). If that actually happened then let's see an official report. There are unclassified summaries available for most major mishaps.

 

[wetb4igetinthewater]

I've done my homework. None of those articles refute my comment.
Everyone understands that if the cabin depressurizes at high altitude and remains there for several minutes then there is a risk of DCS. But the story above was about ejecting, which involves an immediate descent to lower altitude where DCS is highly unlikely.
The RCAF has never operated the U-2, or any other aircraft that cruises at extreme altitudes.
I wouldn't be surprised if several RCAF pilots have suffered some form of barotrauma injuries as a result of high altitude ejections, I'm just skeptical that they were ever properly diagnosed with DCS (bends). If that actually happened then let's see an official report. There are unclassified summaries available for most major mishaps.

Nick,

Are you suggesting that I challenge the guy who is deciding whether I get a NEXUS pass with "Bent? The fυck you were!"