Well, here's my $0.02 worth on this issue.
I'm not terribly fond of the tank system because of the size and space consumption in the luggage area. If you have a parachute AND this in the back you can pretty much consider the luggage area gone. That and the refilling just seem to add to ongoing costs. The on-demand system is great and helps to conserve the O2 to just what is needed.
I do like the Turbo O2 system, but it's very pricey. I had a very long conversation with the owner of Aithre at Osh this year. They are very proud of their products and honestly I found him quite defensive throughout the conversation to try to justify his costs (I think the service price is excessive). I could probably justify the costs a bit more if the maintenances costs weren't $900 every two years on top of the initial acquisition costs. You can offset the costs of refilling O2 bottles with the longevity of the generator, so you don't need to keep an eye on the O2 tank emptying in the middle of a flight. If you have the backup O2 tank installed you're starting to get into some real space consumption in the baggage area. I honestly am not sure how you would get that box installed behind the panel unless you were building with the new heating system that doesn't have the heating unit behind the panel. But maybe there's an option for that. Midwest likely is (or has) working on a method for doing it behind the panel. But I'm not aware of this method.
I've personally flown with the Inogens at 17,500 and they work great. The cons to them would be the extra wiring and "stuff" floating around the cabin during the flight. I've wired my Tsi so the cigarette adapter is right next to where the Inogen would be placed to help reduce the wiring and I do have one Inogen G5 currently.
My solution was to use the Aithre Turbo Oxygen Maker Portable (
https://aithreaviation.com/products/ait ... r-portable) which is pretty much the same as the Turbo O2 maker w/ O2 without the bottle. They used to be north of $5k and I bought mine when they did a 50% off deal. The price is still around that at $2,750. From there I made a mount in the aft luggage area (I don't have a parachute) with some thumb screws, so can easily remove the system if I'm not planning on using it. I also bought a remote on/off bluetooth switch so I can turn it on in flight. I then plumbed the O2 lines to the center console of the plane so I can easily grab the cannulas and put them on in-flight if need be. So I'm pretty happy with my setup - and it works.
The intention is that the Aithre system is there for myself/passenger pretty much full time and if I am carrying extra folks I have the Inogen that I can toss in for that trip.
As far as the altitude limits. There's the published limits and then the reality. The reality is as long as your O2 levels can remain above 90 anything works. The Inogen (as per their manual) says it only goes up to 10,000 feet. But I know that isn't the case - not just personally but from a number of other pilots who have gone to those flight levels with it and remained well within the limits. They have these published limits (Aithre and Inogen) for legal requirements more than anything. Plus they can also use those limits to provide some levels of guaranteed functionality.
The other positive for the Inogen is that it's field serviceable (this is my beef w/ the Aithre system). You can buy the parts and service it yourself. Again Aithre pushed back super hard on this using all kinds of reasons about why it can't be done.
The price you have listed for the Inogen doesn't take into account you can buy used ones on Craigslist for about half of what the costs of a new one are. So in theory, you could buy four of them for the cost of one Aithre system. The one I have was around $1200.
Do I like the Aithre system? Yeah. I tell ya, the Turbo O2 maker and supporting equipment are VERY well made. I have no qualms with paying a little more for a decent product. But I feel the service/maintenance costs are excessive. Plus, as I said earlier, the system I have was originally north of $5k until they had a 50% off sale and it's appeared to stay the same price. You don't put a material item on sale for 50% off and choose to lose money. So the markup on the products (IMHO) is quite high. Do they deserve to make money on their products? Absolutely - and I fully support them in doing so, but for what they are charging for the initial purchase v. maintenance it's just a bit much.
Not that I have an opinion on it or anything.
