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The ROBD is usually available during MAYO clinic training at NJA company recurrent in CMH for those who want to try it. Nifty little device that just substitutes nitrogen into the air mix and gradually lowers the partial pressure of the oxygen.
I agree with the "one pilot at the controls" rule, but one pilot to wear the mask at all times above a certain altitude (and different alt's for different FAR parts???) is really outdated. I know that many disagree with this based on time of usefull consciousness numbers. However, check an aviation safety database and search for pressurization accidents and see what you find. There are very few and most occur before the A/C reaches high altitudes. Also, with the advent of Emergency Descent Modes (autopilot/autothrottle automatic descents) on more and more aircraft, it's time for a rule change. And yes, I remember the unfortunate Payne Stewart accident. I just think there are better ways to improve safety.
In all seriousness, does anybody actually don their mask above 350?
About 3 weeks ago I met a Citation Shares pilot who told me that the company is really enforcing that rule after one of their owners took a picture of the crewmembers not wearing their mask above fl350
I flew a Lear 35 at a Part 135 Company for two years. The airplane I flew was used for data and research in the Payne Stewart litigation because they were similar serial numbers. Lawyers and engineers were out on three occasions I know of to take measurements.
I looked at the cabin outflow valve and talked to our mechanics about it.
The thing is nearly 100% plastic. Ours was replaced while I worked there because we had an erratic cabin pressure write-up. It turned out to be cracked nearly 2/3 of the way through. It was just a matter of time until it failed completely.
That valve was less than two years old, and was of the new and improved “Post Payne Stewart” variety. When the valve fails, you now have a 3-inch hole directly from the cockpit into the nose compartment. That is where the 2-4 second estimate for pressure equalization comes from.
I have nearly 6000 hours of military time with a mask on my face. I find military masks relatively comfortable. The problem is, most civilian types are not. The EROS “Alien” masks are pretty good, but at $12,000 each, most operators won’t retrofit them to an older jet. The Lear mask was a piece of Gothic medieval torture—but I wore it anyway.
When I first got there, no one would wear the mask. I made a point of wearing it, or asking the Capt to. I often got the “Why? No one can see us” look. So I told them what the chamber is like, and how quickly it can go from good to bad.
By the time I left, most guys would wear the mask, if even reluctantly. So at least it was being done. The good news in Part 135 is that time above 350 (or 250 if someone goes aft) is usually pretty short.
(You may not have considered that during a rapid decompression, you can get evolved gas problems—ie, the bends, or even nitrogen narcosis—just like rapid ascending from a scuba dive. If your regulator allows pre-breathing oxygen, it will lessen that possibility).
I don’t think the rule is all that archaic. Just look at QANTAS’ oxygen bottle blowout this summer. Every Lear 20 and 30-series has that plastic valve---how many other jets have a similar single-point failure mode?
You never know. And that is why you should wear the mask.
About 3 weeks ago I met a Citation Shares pilot who told me that the company is really enforcing that rule after one of their owners took a picture of the crewmembers not wearing their mask above fl350
I bet a lot of Citation Shares pilots are flying at FL350 or below now.
About 3 weeks ago I met a Citation Shares pilot who told me that the company is really enforcing that rule after one of their owners took a picture of the crewmembers not wearing their mask above fl350
Yep a true story but the owner wasn't even concerned about his safety. He was trying to use the photo to get a free flight!!
If you have ever been in the altitude chamber, and gone to FL350, you would demand that someone wear the mask in the airplane above 350.
When I was a 2Lt and student USAF pilot, the chamber went to 35,000 (now they only go to 25,000, I've been told). You get oxygen-stupid amazingly fast, except, in my case, I didn't even realize it--until someone put my mask back on for me.
For civilians, if you contact the FAA at Oklahoma City, they will put you in touch with the closest military chamber--and you can get a free altitude ride. VERY worth the effort. It is space-available, though.
For what it's worth: the size of the fuselage makes a difference in how long it takes to equalize the pressure if you have a catastrophic window failure. They told us in the 747 it would take about a minute at FL350 if you lost THREE cabin windows.
In the Lear 35, best estimate is 2-4 seconds.
I always wear the mask.
Been in a chamber at 290. Yes you get weird and it happens fast. But not enough to freak me out the way you are. I still enjoy, with no nervous breakdowns, cruising in the bus at 390 with out.
As stated before its all because in the 121 world our oxygen is better.
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(You may not have considered that during a rapid decompression, you can get evolved gas problems—ie, the bends, or even nitrogen narcosis—just like rapid ascending from a scuba dive. If your regulator allows pre-breathing oxygen, it will lessen that possibility).
Can you explain how a pilot can get nitrogen narcosis? Or Bent. I think you got that wrong.
From the literature I have read from DAN (divers alert network), the only pilots that ever even came close to being bent are those people flying U2s, SR 71's and similar aircraft, and they only "showed symptoms" of DCI.
Do not confuse nitrogen narcosis (getting "narked") with being DCI (decompression illness, also includes lung over expansion injury) they are not the same thing, and aren't really related.
I could write 1000 words about DCI, but you won't need to worry about it at flight level 350.
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