So what is the practical protocol for the light jet pilots who fly SP and cruise up high on a routine basis?

It appears all the light jets predicate their range assumptions so far high up, at 41,000 feet. Even the mustang's range map is predicated at 41,000 feet.

http://cessna.txtav.com/aircraft-range-tool

These altitudes sound great, but wow that is way high up there! Even higher than routine commercial airline flights (which obviously have dual crews)

Do you actually have the quick donning mask around your neck on a routine basis?

Do you wear it?

The need for a quick donning mask relates to the amount of time you have to put on a mask when you have a rapid decompression. With a rapid decompression at higher altitudes you have progressively less and less time to recognize what has happened and then find and put on your mask and get oxygen flowing. You have precious little time to do so before you become hypoxic and become confused and unable to realize what you should do. At those altitudes I have always either already been breathing oxygen or have a quick don.

I thought that, at high altitudes, if one pilot leaves the cockpit the other had to wear a mask until the other pilot returned. Would that mean a single pilot has to wear a mask all the time? How is this handled?

The one not wearing a mask is basically not a factor in a rapid decompression. The pilot flying with the rapid donning mask would have to most likely help him. Whether there is another pilot in the cockpit that is without oxygen is the same as not being there. He can't be relied upon to make any significant contribution to the emergency until he (or she, I guess) got on oxygen. Don't really know what the current FAA regs on it are but the physics are the same regardless of whether there is another pilot in the cockpit or not. The use of the mask when only one is in the cockpit can also be related to a sometimes belated recognition of hypoxia at higher altitudes. We did that in the AF when I flew tankers but it was what was written, so we did it.

The entire rule is bullshit and nobody obeys it including net jet pilots.

That is what I understand too.

However, if I buy a light jet and want to get max performance out of it and take it to FL410 solo / SP I should be wearing a mask. Right?

Not my experience at all. Why is this rule bull.....? Have you been through a decompression at FL 410 or above? I've been through one at FL 350, it's not a joking matter. You've got about 10 seconds before the lights go out, depending on how you, individually, react to the situation. Above FL 450 you have no chance.

You must be basing this on the, it's never going to happen anyway line?

WOW! It may be BS but look up what your TUC is at 410 in the event of a loss of cabin pressure. Cut that in half if it is a rapid decompression. It probably won't happen but if it does you'll be unconscious in about 5-10 seconds without a mask; if your a triathlete. If you're in a lesser state of fitness it will be even shorter. I would wear the mask.

Yea, I agree it is stupid to obey the regs and be safe, especially when you don't fly jets at 41k.

With a rapid decompression at FL410, you have about 7 seconds. The regs require you to have a mask donned at that altitude. However, it is the single most violated regulation in aviation. Why? Because it hardly ever happens. Some airplanes are probably less likely to have it happen than others, but if it does happen, having the mask on is only going to give you a chance. There will be so many other things working against you both physiologically and operationally, you'll have to rely on some luck to get through it. One feature I really like in the Mustang is the Emergency Descent Mode (EDM). If you have a cabin decompression, all you have to do is idle the throttles, drop the gear, and throw out the speed brakes. Hopefully, you can stay focused enough to do that. The autopilot will automatically turn 90 degrees left and do an emergency descent to 15,000 feet. It takes about 2:20 to drop to 15,000 from 41,000. At that point, hopefully you still have a chance to execute a landing somewhere. There is yet to be a rapid decompression in a Mustang, and hopefully there never will be.

What is it, above 350 or 380 a single pilot must be wearing and using the mask?
Is the oxygen bottle even large enough to support a max range flight at 410?

Nobody obeys the rule. It exists only in US of A because of Payne Stewart. There have been two rapid decompression events worldwide in the last 40 years in twin jets that were not accompanied by structural failure. Let's go thru this topic again with everyone disagreeing, because I said it was BS. Then let's pull up everyones YouTube account BSing around at FL410 or FL450 or FL510 with nobody wearing a mask in the cockpit, even when the co-pilot goes to take a leak. Rapid decompression is about 1000x less likely in a twin jet than PT6 shitting on you in a PC12 or TBM. Nobody wears a mask in a twin jet. Just landed in Austria two days ago. Pilots took a leak multiple times in 10 hours from Omaha to Vienna. Nobody wore a mask the whole time. We were IMC the whole time because of cigar smoke.

You have wear it above FL350. Yes, there is enough O2 to get you through the flight, but you'll be refilling the bottle before the next flight. I agree in that virtually everyone violates the rule, but it's still the rule. It's kind of like preparing for something that is almost certain to never happen.

Another thing I learned at Flight Safety was the procedure for dealing with an engine fire. Some people wonder why the Mustang only has one Halon bottle for engine fires. Well, Cessna has been building Citations since 1969. Any idea how many Citation engine fires have occurred since 1969? ZERO. That's right. There's never been one. Yet, the FAA requires a fire suppression system. Not a bad idea, but it is yet to be tested on an actual fire. Thus, why have more than one bottle?

Jets have a bunch of things you prepare for that you're highly unlikely to experience.

I assume you're going to sweat into your face for hours at a time wearing that nasty rubber thingy every time you go east to catch a tailwind. Yeah, right. Can you say "Say Again". Some amazing microphones in them things...

No %#$@...