Operating altitude / service ceiling

Now, how does this work in real life? Does that mean I can plan a flight at FL160?

Yes. But it will take forever to climb the last 2000ft if the demonstrated altitude is 16400ft. FL140 seems more realistic to me unless you keep the weight very low.

Also, is FL160 sufficient to stay on top of (most of) the weather?

Unfortunately not. At work a fly a bizjet and on (our) typical sub-one-hour legs we rarely climb above FL 250. Even at this time of the year we are in clouds most of the time with the kind of frontal weather that we have right now. With icing conditions present from the surface up to at least FL200. And it's getting worse every year. The stable high-pressure conditions that used to dominate central european winter weather for weeks and weeks in a row are now reduced to a few days only. Saturday I had a flight where I needed to keep engine anti-ice on for the whole 50 minutes and wing and tail anti-ice for at least 30.

My own experience, TB20 with a TKS de-iced prop, is that nothing short of FL250+ capability is going to remain VMC in the average frontal weather.

So I avoid frontal weather Except where it is clear that the front is a very weak one and the IR images suggest the tops are not above c. FL150-180.

Obviously your despatch rate suffers, but that is the price for being a poor pilot

I think I would manage a 75% despatch rate, taking random dates, whereas a TBM850 (or some other radar-equipped and fully deiced aircraft with a FL250-300 ceiling) would probably do c. 98%.

A pilot who likes to take chances in a less equipped plane will be somewhere between the 75% and the 98%. One could debate that, of course...

If you avoid frontal weather (which as What Next says appears to be getting less easy each year) then the FL160 ceiling is fine.

Most of the time you will be VMC on top at FL120-140, no problem.

The other factor is Eurocontrol IFR routings. These tend to have an absolute minimum of FL070 (basically the base of controlled airspace, e.g. FL070 in the French Class E) but the available routes down there are - outside of France - usually rubbish. They get better at FL100 and better still at FL120. For some cases e.g. Frankfurt overflight you need FL130. I normally file for FL140, and request a "stop climb" once in nice VMC.

Oxygen is really useful; you are crippling yourself without it. I know many pilots fly without it but I always carry it and always use it at FL100 or higher. Even if not legally required, it makes a difference between landing fresh and landing exhausted. At the bottom end of the technology, portable oxygen is cheap. You stick the cannula up your nose and forget about it almost immediately. You can eat, drink, talk, etc. The only time oxygen is an issue is with "not responsible" children, or if somebody has a blocked nose (you have to carry a mask, in case).

I cannot understand why so many pilots fly without oxygen, FL100 max, in icing conditions and turbulence, not knowing what convective stuff they might fly into, when they could be at FL120-140 and getting a suntan

My experience over the past two months suggests that in stable air, the mid to high teens should be enough to be VMC-on-top. In frontal weather (eg my trip back last week from Berlin). I was still in layers of IMC at 210 as the front moved through. While I didn't climb given I was about to come back down into Munster, I suspect that, even at FL250, I would not have climbed over it.

I've flown the DA40 up to FL100 (which is the Max I could get VFR), and the climb performance at that level is still fine, because of the turbocharged diesel engine. According to the POH the demonstrated Operating Altitude is 16400ft (pressure alt).

Now, how does this work in real life? Does that mean I can plan a flight at FL160? Also, is FL160 sufficient to stay on top of (most of) the weather?

I haven't heard the term "Demonstrated operating altitude". The usual term used is "Service Ceiling" which basically means the altitude at which your best rate of climb has dropped below 100fpm.

As you approach this level, you're obviously talking about a climb rate that is going to cost you just under 10 minutes to climb 1000ft.

Even when you stop your climb, you're using a lot of your engery just to hold your altitude, which can affect your forward speed quite a bit. If you're lucky you'll have a nice strong tail wind which more than compensates, but if you're unlucky......

I've no idea of the implications for the different termonology used in your POH though.

Here is a TB20 at its ceiling

On a nice cold day it takes 30-40 minutes to get there. In ISA+10 conditions, forget it; FL180 is about the max, at MTOW.

lenthamen, unlike most aircraft with a service ceiling, the 16.400 ft max altitude of the DA-40 TDI is a limitation, not a performance number.

In other aircraft I would rule out planning a cruise altitude so close to the published maximum. However, altitude performance of the Thielert engine cannot be extrapolated, as it is not purely a function of density altitude, being electronically governed.

I also have flown the DA-40 TDI to FL 100 and not much higher; also with the 2.0 Thielert.

At this altitude I have noticed that the engine's performance is far better than book performance. The percent-power-indication; the climb performance and the max cruise speed are all significantly better than book performance. I suspect that this is the result of replacing the original 1.7 engine with a 2.0 engine without changing the POH. Max power is limited to the same 135 HP (to avoid recertification tests?), and rewriting the POH is not required as altitude performance is better in all respects (and so considered non-critical? Pilot DAR is most welcome to correct me; I suspect from his profile that he knows about this).

I am just guessing here, and I am very interested to know whether you observe the same "excess" performance when flying at altitude.

I don't have all the numbers here, but I remember a stable max cruise speed of 147 KTAS at FL100 at close to ISA temp; this is at least 12 knots above book values, an excess which is otherwise unheard of. And yes, I double checked that airspeed. However, indicated power was 94% or more; POH says only 80% should be available at that altitude. Depending on software, the engine may very well deliver far better than book climb performance up to FL 160, but there is no way to tell from the POH; only a flight test will show.

I understood that Mountain High O2 delivers the best system at the moment.

You can play this 2 ways, I think, depending on how much you fly, how easily you can refill, and how much you want to spend.

(1) The "entry level" option is a cylinder, a 1st stage regulator with 4 outlets, and "oximiser" cannulas.

(2) The "nice" option is a cylinder, a 1st stage regulator with 4 outlets, the O2D2 2-outlet electronic demand reg, and ordinary cannulas.

I always recommend buying a fair size cylinder, because refills are usually a big hassle. The one I fly with, composite material, is about $800. It is very light. The details are at the end of my o2 writeup.

Composite cylinders can be very pricey ($3000 or so) but for some reason the MH "48 cu ft" one is a good price. I have 2 of them - in case one runs out because I forgot to shut it off after a flight

Can you recommend a shop that sells them in Europe?

Buy them straight from MH in the USA. Just call / email Eric Westeren. I tried to buy MH stuff in Europe and it was poorly stocked and prices were inflated. There wasn't any point.

Too often I had to cancel a VFR weekend trip abroad because of the WX...

VFR despatch rate is a lot lower than IFR - especially if you want to do long legs and climb high into CAS which is known to be accessible VFR (rare in the UK but common in Europe). Assuming you actually fly 100% legal VFR which is not a widespread habit here in the UK, I reckon 30-50%.

I think I would manage a 75% despatch rate, taking random dates...

I will be really, really happy if I could actually fly three out of four planned cross country flights! Too often I had to cancel a VFR weekend trip abroad because of the WX...

I just did my numbers on this over the past two months and with full de-icing and pressurisation to go to FL250, I had a 100% despatch rate on 25 sorties with 2 almost diversions on returning to the UK. I think the longer term rate is more likely to go to 95-100%. At this time of year, I think de-icing is the bigger driver than altitude. But VFR vs IFR would make an enormous difference. I calculated that of the 12 flights to Europe, only one could have been done VFR (or more correctly, only one would I have launched if VFR).