EDS vs. Aerox (OxySaver) O2 System

Is the EDS system clearly the best oxygen system (i.e. worth the extra $)? I'm planning my equipment for a new ship to fly in the western US, and trying to decide between the EDS and Oxysaver options. I'd appreciate comments from others who have gone through this decision.

Yes, and it depends.

I'm looking at the same problem. The A-14's in my Lark are old and, with the two 22 cubic foot capacity steel bottles the whole system weighs 54 pounds. I'd like to recover the payload.

The EDS has the advantage of needing a much smaller bottle which needs to be refilled far less often. It is certainly better than a mere constant flow system in that regard. You'll have to decide if it is worth your money.

There is another option that I would like to hear about. That is liquid oxygen systems. A quick check of e-Bay finds several used portable liquid oxygen systems for medical applications in the $100 (US) range.

These things provide substantial flow of O2 for up to 15 hours and weigh just a few pounds. They are small enough to be 'personal gear' and not have to be a permanent part of the airframe requiring a Form 337. The problem is getting them refilled. I expect that the charge for a medical refill is steep but I understand that there are air reduction units that produce LO2 from air using 120V AC power.

Any thoughts?

Bill Daniels

I found a thread that discussed liquid oxygen at length - search for oxygen in this group, I think it started on May 3rd. Pretty controversial, and it didn't sound too pragmatic in many respondants'

Have you given any thought as to what might happen if spillage should occur in flight? Liquid oxygen is at a temp of -320 deg F. Aluminum gets rather brittle at that temp. Do not know about Fiberglas. Not very good for the pilot's skin either.

spillage should occur These things are ruggedly designed for everyday use by mobile patients. They are designed for portability so they have to withstand the rigors of auto travel. The medic's I have spoken with consider LO2 safer than high pressure bottles.

They are even designed to be refilled at home by patients from dewars of LO2. As such, they have passed a lot of FDA and other government certifications. I doubt that there is much concern about spillage. It appears that they would have to be smashed for the LO2 container to leak.

By comparison, compressed O2 isn't all that safe. A leak in a high pressure line can do damage to both the pilot and airframe. An exploding high pressure bottle is something we don't even want to think about.

Bill Daniels

From one who knows next to bugger-all about liquid gasses....

Do you have to keep LO2 cold to stop it wanting to become gaseous and producing high pressure in the bottle? If so, how?

Rob

At 13:42 13 May 2002, Bill Daniels wrote:

Yes, you have to keep it cold to keep it in liquid form. If you don't, it will turn to a gas and generate quite a bit of pressure unless it is released as it evaporates.

Basically, the portable liquid oxygen (LOX) systems are small thermos bottles called dewars. The idea is to fill it with LOX (at minus 183 degrees Celsius) and them use it before it evaporates. The portable medical systems give about 15 hours at 2 Liters/min. The rate of evaporation is controlled by a small electric heater powered by a battery.

Cryogenic liquids can't be kept indefinitely without refrigeration but a dewar will maintain a gas in liquid form for a very useful period time. I have kept liquid nitrogen (-196C) on a bench in an open foam plastic coffee cup for about an hour. A one liter open dewar of LN2 will last about six hours on a bench. (I was cryowelding small metal parts together. You can shrink a metal shaft with LN2 so it will fit into a hole in a gear smaller than it's diameter at room temperature. When it warms up, it's welded in place.)

It's not clear whether LOX in a glider is practical but I think it is at least as safe as compressed O2. The obvious down side with LOX is that it must be filled each time you intend to use it. This means that a filling system must be available at the airport or that you must fill it on the way.

The advantage is that portable LOX systems are very small and light compared to compressed O2. You could just strap one to a seat or toss it in a storage area.

If you expect to use O2 only occasionally, LOX is a non-starter. Where I fly, O2 is needed on almost every flight in the summer. In this case, LOX might have an advantage.

Bill Daniels

No offense, but this whole thing sounds like a solution in search of a problem.

The problem is an obvious one, surely it is that of ensuring that the pilot(s) have sufficient O2 to safely operate for longer durations. I'm sure the perlan project aside from using pressure suits will be experiencing these types of challenges

No rumor, there are two LOX systems in the bay where the motor normally lives (along with stacks of batteries). They are loaner units from f-16s, I believe...

Now an F16 taking a canon round in the LOX tank cant be pretty

Anyone out there fly Microprose F16 sim by the way?

Al