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Aviation Oxygen (merged)

And it can still take full fuel.

EGTK Oxford

I know it's for a different purpose, and is only required in an emergency, but the CJ3 has a 50 cubic foot oxygen bottle, and that could have to supply 10 people in a descent down from FL450.

Your 48 cu ft cylinder is quite admirably large.

I suspect that yours has to put out a large continuous flow rate out of ten masks.

Using a cannula saves a factor of several times.
Using an oximiser cannula saves 2.5x over a plain cannula.
Using an O2D2 saves about 5x over a plain cannula, and probably 20x over a mask putting out enough o2 to keep somebody half alive for just long enough at FL400.

So that's a very different situation.

Administrator
Shoreham EGKA, United Kingdom

@Peter: Little bit OT :) but what IAS/TAS and what climb rate you get when you climb a) between FL100 an FL130 b) above FL130?

LDZA LDVA, Croatia

but what IAS/TAS and what climb rate you get when you climb a) between FL100 an FL130 b) above FL130?

I don't remember, and also I work on the engine temperatures first (i.e. maintain a high-ish speed), but at FL100 would expect 500 fpm or so at Vy, with this reducing to zero at FL200 in a fairly linear fashion.

At sea level I get just slightly over 1000fpm, MTOW, so if you took a straight line from that, it's probably not far off.

But as I say I almost never climb at Vy.

The TB20 is fine to FL180 anytime in ISA conditions, and to FL200 if lighter.

Administrator
Shoreham EGKA, United Kingdom

Oxygen is not the only issue on high altitudes. In the winter season one can mix isopropylalcohol at 1% to AVGAS. I have never heard about this in summer time. How do you prepare your fuel in spring or summer time to avoid fuel icing ? My maximum altitude was FL 210, where I was concerned about at OAT of -24°C.

Berlin, Germany

I think fuel icing is highly fuel system dependent.

I have flown (TB20) for hours at -30C but there is a prolific pilot forum poster who flies an Aztec who (if my memory serves me right) has repeatedly claimed he gets a guaranteed engine failure at -15C (presumably both engines). IMHO this behaviour (if true) is absolutely not airworthy and if I was the FAA and found this universal I would issue an emergency AD grounding the worldwide fleet.

Some years ago I met a pilot of a Beech Baron who lost both engines to apparent fuel ice over the N Sea, in VMC. They restarted at about 2000ft. He immediately sold the Baron and bought a King Air. He said "the only thing better than a PT6 is having two of them".

This is a well known case

I do long flights in expected cold conditions with ~ 0.5% IPA added, but have no reason to think it is needed. I have never heard of fuel icing on a TB20.

A really interesting and illegal experiment would be to rig up an IO540 with miniature PT100 sensors on various parts of the fuel distribution spider (which is a very thin stainless steel tube) and fly it at various OATs and power settings including very low ones typical of low flow rates at high altitudes and see just how close that thin pipe gets to the OAT.

Avgas freezes at something like -55C but not if it has some water in it.

Administrator
Shoreham EGKA, United Kingdom

A while ago I started a discussion on altitude flying, and I decided to buy an oxygen system.

I found a diving shop close to my house that fills Oxygen, using the DIN-477 connector, and they were happy with me as a customer selling it for 0.022EUR/liter.

So far, so good...

Then I contacted a Mountain High Oxygen Dealer in The Netherlands, and as soon as I mentioned that I was going to use "Diving Oxygen", they start arguing strongly against it, because "it contains too much water, and there is a chance that the system freezes up. Not safe.". They even forwarded me a mail from the Divox Gas Supplier saying that Diving Oxygen should not be used for aviation.

The problem is that the only place that I know of that sells Aviation Oxygen in The Netherlands (Hugen Aviation Oxygen), is a long drive, so I'm a bit disappointed that I can't use my local dive shop...

I would think: Oxygen = Oxygen, but apparently that is not true...

Is there any specification on how much H2O is allowed for the MH Oxygen system?

Why would it be more likely to freeze in aviation than diving? I assum your cabin is not running at a sub zero temperature? Wouldn't freezing be more related to the expansion of the compressed gas which happens in both applications?

EGTK Oxford

There is zero water in modern oxygen.

Well, there are tiny impurities - of the order of 0.1 to 0.01%. I spoke to British Oxygen about this and they gave me the figures, and they are all the same for

Welding oxygen
Food fresh oxygen
Medical oxygen
Aviation oxygen

Only the paperwork (and maybe quality supervision) differs.

The manufacturing process is the same nowadays - cryogenic with some variations (example).

Don't confuse this with "oxygen concentrators" (also discussed in this forum) which pump air through zeolite and remove most of the nitrogen, which is OK for altitude breathing but AFAIK most of the water vapour remains, and so do all other gases.

I use welding oxygen, and have been since 2003, with Aerox, Precise, and now Mountain High. The reason I use it is because I can get the cylinder swapped for a new one by a local welding gas depot, no questions asked. I also get argon gas from there for TIG welding (really expensive stuff).

"Freezing" is nonsense anyway. The equipment is in your cockpit. The 1st stage regulator cools a tiny bit; maybe a few degrees C.

Administrator
Shoreham EGKA, United Kingdom

I was thinking the same, Jason. Also: If diving oxygen would contain more oxygen, then why aren't the steel bottles corroding on the inside?

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