(I just bought a 647L cylinder and don’t find it too big / heavy)
Peter wrote:
I wonder whether these “nitrogen stripping” devices work at “IFR SEP top end” levels like FL180-200.
The Inogen Aviator G2 is specified for up to FL180 “because above that the FAA mandates (recommends?) full face masks”. They confirm that the compressor of all models will issue the nominal flow rate at altitude. Only it will last for thousands of hours instead of tens of thousands of hours when operating on the ground at non-mountain elevations. So in my understanding, “we cannot tell you clearly, but they work fine higher… if the oxygen quantity delivered is enough for your physiological needs”. The G2 is specified for 1265ml/min. New G3s are 1050ml/min, older ones 840ml/min. There’s also a G4 specified at 630ml/min, The documentation of the medical version doesn’t say so clearly, but it gives the “maximum pulse setting”. That’s the flow divided by 210ml/min.
My expectation is that the smaller units are great for pressurised aircraft where the cabin altitude is legal, but below your optimal comfort level, and will allow the crew (and passengers) to arrive less fatigued. Mine is arriving soon, I’ll report my findings when I get the occasion to test it. Also if I ever take the local club’s ratty Cessna 182TR up to this kind of altitude :)
lionel wrote:
My expectation is that the smaller units are great for pressurised aircraft where the cabin altitude is legal, but below your optimal comfort level, and will allow the crew (and passengers) to arrive less fatigued. Mine is arriving soon, I’ll report my findings when I get the occasion to test it.
I did my first real flight with the oxygen generator. Cabin altitude was around 11000 feet. The two pilots (front-seat occupants, among which yours truly) shared one Inogen Aviator G3 on maximum setting (pulse setting 5 = 1050ml/min), with a simple “Y” splitter (which was delivered with the unit, along with the tubing, cannulas, etc). Due to the “detect inhalation stroke and inject a fixed amount of oxygen into the inhalation” design, I’m not convinced we each got a strictly equal share of oxygen: Imagine one always inhaled a fraction of a second before the other one, he may have gotten the brunt of the bolus.
I certainly felt in much greater shape than usually after a flight. How much of that is placebo effect is anybody’s guess :)
loco wrote:
did you connect it to onboard power source?
For part of the flight, it was operating on battery, and then we connected to onboard power. It certainly was charging, it was at like 99% or 100% at the end.
@loco, do you use the standard version or the Aviator version?
I would like to see how well it works (what blood o2 is achieved, by a normal-size person, non smoker) at higher levels e.g. FL150/170/190.
I ask this because delivering o2 at say FL100 involves so little gas, if using a decent demand regulator (the O2D2 or its single version being the only option currently, AFAIK), that a small cylinder will do 2-3 people for a trip to Greece and back. It is at higher altitudes that the aircraft-powered generators get really interesting.
I am sure many people are watching this carefully. Of the early adopters (near the start of the thread) I don’t believe any are still flying. One of them sold up the SR22 and went to microlights.
As I have mentioned beforeI do use the oxyfly. With two persons on board and with full oxygenflow, we achieve without any problems a sturation of 97%-98% at FL 150 for more then two hours. Both of us ar nonsmokers. We do use it now since 2012.
I have the standard version.
Peter wrote:
I would like to see how well it works (what blood o2 is achieved, by a normal-size person, non smoker) at higher levels e.g. FL150/170/190.
Since it seems that loco’s testimony (posts 39 and following) left open questions for you, if/when we are at the same place, you are welcome to take my Inogen G3 (max 1050ml/min) for a trial flight. I believe you have your own cannulas? Any result of the Inogen G2 (max 1265ml/min) you’ll have to extrapolate yourself.
Note that loco said he was using at FL160 pulse setting 3, meaning 630ml/min. That’s the rating of an Inogen G4. Which also means that, from pure raw numbers, you can use one Inogen G2 for two people (with a Y-splitter, not another regulator) and get the same total oxygen per person than loco was using. Now, the subtle part: “total oxygen per person” is “total oxygen delivered divided by number of persons”. It does not mean that each person gets that amount of oxygen. Theoretically, I can imagine that due to the “bolus” system, one person gets more than the other depending on the timing of their breathing. However, assuming the frequency of breathing is similar but differs (even if only by a few percent), I think the average over a dozen breaths or so will be at least roughly divided equally, since that will ensure the timing of the breaths is not always “A breaths before B” for fixed A and B. If you have a flowmeter (or even a totalising flowmeter), we can even measure that 
I’m up for investigation for the sake of knowledge and experimentation.
