High level IMC flying

One shouldn’t take flying at FL200+ lightly. Monitoring the oxygen level in regular intervals and having backup equipment including mask available is a must.

I had a Mountain High O2D2 failure at high altitude in IMC and difficult weather — it just stopped dispensing oxygen. I was prepared for that and it took me about 30 seconds to apply the mask but if I hadn’t been prepared, it would have been quite a challenge. I did do previous flights like this where the mask was onboard but not in reach so I learned my lesson.

europaxs wrote:

Cannulas work well even at FL250, even though FAA doesn’t believe it.

Indeed, but Mountain High O2D2 are not be trusted, they can fail at any point and they like doing that with the valve shut.

The FL180 cannula limit is only for installed o2 systems. Details here

Typically such systems are found in turbocharged aircraft e.g. TB21, SR22T.

Such systems are governed by the AFMS which is regulatory agency (FAA, CAA, DGAC, EASA etc) approved. So if the AFMS says Mask above FL180 then legally you have to wear a mask.

But there is no reg on portable systems.

Cannulas do work at FL210 (the highest I have been in the TB20) but you have to breathe very consistently and not get lazy.

That’s a risk you have high level in IMC as well.

True, but I was responding to your question as to why one doesn’t fly at low level in IMC, below the 0C level i.e. safe from icing.

If non-turbo, the only reason to fly higher than about FL080 (apart from terrain, obviously) is to get VMC on top.

It is IMHO certain that the safest flight is VMC on top, because it is VMC so you cannot fly into something nasty. And if the tops rise so you cannot maintain VMC then you do a fast descent, perhaps collecting ice, but usually it is not too much ice because one can descend fast and the vertical extent of icing is usually not more than a few thousand feet. Obviously you don’t want to be doing this above the Alps…

That’s why we have two O2D2 units. They are relatively cheap.

I have two also, which enables four people to get oxygen, or if flying 2-up you have a backup unit.

I also have a second 1st stage regulator.

You can also bring a mask with you, but is less convenient…

You MUST carry a mask, for anyone who has respiratory difficulties. I can think of 2 or 3 people who have needed the mask. Children also tend to sleep with their mouth wide open. I have several of the cheap masks (no microphone) and one of the expensive MH $400 ones which has a Darth-Vader-emulation microphone

Sorry to divert slightly from the original post, but as we speak about canulas and masks, why the o2 flow has to be higher (with the oxymeter) for a mask than a canula ?
I too have MH mask and canulas from Aerox, and I can litteraly fly 6-8 hours with 3 people onboard flying at FL180 with canulas, while the O2 bottle will only last 3-4 hrs with masks and 3 people again.
I thought it would be the contrary since O2 is confined in the mask, whereas much more diluted with canulas…

Peter wrote:

If non-turbo, the only reason to fly higher than about FL080 (apart from terrain, obviously) is to get VMC on top.

On longer distance flights, > 200 nm, I always consider the wind charts. Often one can take advantage of great tailwinds at higher altitudes.
I remember a flight this year where I had a tailwind at FL 100 of 20 kts and up to 50 kts at FL 170. So getting higher sometimes makes sense even in a non turbo aircraft. And imagine a technical problem en route. From high altitude you can perhaps reach an airport and avoid an emergency landing on a field or you can resolve the problem with more time to think about, IMC or VMC.

Especially in summer, I often choose the altitude based on temperature. I like the combination of sun shining into the cockpit (= greenhouse) and massive influx of very cold air.

This August, I did my IR check ride, one hour flying manoeuvers close to the ground at 35°C. That was quite a challenge! At FL150 it would have been perfect.

I don’t think the O2D2 is cheat at € 1000 (around $ 850 in the US) – i thnk it’s too expensive.

Mine has worked like a charm for 2 years now, but that’s another reason why i don’t like to fly above FL160.

why the o2 flow has to be higher (with the oxymeter) for a mask than a canula ?

Probably because an O2D2 with a cannula can squirt pure ogygen up your nose right when it is most effective – at the start of the inhalation cycle – whereas with a mask you are breathing a mixture of pure oxygen and ambient air. There may be masks which feed 100% oxygen but I don’t think they are used in GA, and there would be no point because at say FL180 the oxygen partial pressure is down to 10.5% (from 21% at sea level) so you need only a little bit of extra oxygen to get back to 21%.

I don’t think the O2D2 is cheat at € 1000 (around $ 850 in the US) – i thnk it’s too expensive

The O2D2 is $850 so why buy in Europe? Buy it here

Still, I am sure the gross margin is approximately 80% But that’s normal for an electronics company selling directly to the end user. I’d expect nothing less. You have to do that, to support reseller discounts. The fact that most resellers of specialised gear rob you (the mfg) of a lot of money while offering no service (most order back to back when you order from them) is a fact of life…

This flight test, done by myself and another pilot here in 2008, has upset a few people in the business

Of course i bought mine in the US aswell. And course i understand how trade works. I’m just saying that $ 850 for that gadget is not cheap.