the only effect they have is to make the certified marked more expensive to enter, unless you fly 500+ hours each year.
I think the pricing is because the Marketing people always aim for the low hanging fruit which is the 500+ hr FTO industry.
I think the vast majority of DA42s went to FTOs, for example.
Retrofit kits never make sense for private owners unless they really want avtur operation.
We have done all this before on the various diesel threads but I think the ease of field maintenance in the major market (USA) will massively outweigh any product on which you can’t do that – no matter how efficient it is (within the limits of physics). Also Americans are deeply suspicious of anything where some far away factory in Europe has you over a barrel, and I agree with them. I don’t like it even for avionics (it’s the fact for most glass cockpit products of the G500 and upwards).
I think deep down the diesel makers (or their financial backers) know this. Let’s face it – a bank will be delighted to lend you money when you are making so much of it you don’t know what to do with it… but the 250HP+ diesel projects keep reappearing at Friedrichshafen year after year, burning some investors’ money all the time but never getting enough money to get anywhere. It cannot be hard to make a 250-300HP diesel. The lower powered ones are fine for flight training, so that is what gets developed. They also address some private flying; e.g. the DA40-TDi is a fine aircraft for 2 people travelling light. And lower down, Rotax owns the business and diesels cannot compete there at all.
no hassle in greece about getting Avgas
If you have a TB20, there is no hassle in Greece with avgas anyway 
From any of the airports which have it and which are legal points of entry (Corfu, Samos, Iraklion, Sitia, Athens, Rhodes) you can go anywhere and back without a refuel.
The time avgas would be a hassle in Greece would be if you lived there and didn’t live at one of these places Then you would have to illegally keep drums (which can be bought for about €3.50 per litre) or just mix in car petrol…
There is also Megara but not a port of entry so a major hassle.
Anybody who wants a Lycoming IO-320 in their RV can have one, but most buyers get the 360… Because what they really want is 2000 fpm climb…
My plane is certified with the IO-320 but mine has a carb’d engine. Nothing to do with me, that’s the way I found it but I believe I’d choose the carb engine if I had the choice. Fuel cost is not a big part of my budget, and I like the simplicity and low pressure fuel lines. I did have carb ice once (on the ground) but that’s not a big part of my life either. I would surely prefer if either 80/87 or 91 UL were available because they’re better for my stuff. I would absolutely run 91 UL in my motorcycles.
SR22: 11.5 USG/hr for 140kt IAS (low level)
That’s simply wrong, Peter. My SR22 will always fly 153 to 155 KTAS at 4000 feet with a fuel flow of 11.5 USG, sometimes only 150. (And about 160 with 15.5 IUSG)
UPDATE: Sorry I missed the IAS :-) Yes, 140 KIAS is about correct.
My comparison was about airframe and engine efficiency.
There is really very little difference between them.
Obviously the SR22 (310HP) goes faster, but the MPG then gets worse.
The obvious conclusion is that the SR22 and the Cessna (Lancair) 400 are more slippery than the TB20 on the airframes (they ought to be, with compound curves etc) but throw away the advantage in the fixed landing gear. Of course a Cirrus salesman will disagree.
BTW the 140kt could be 138-142 depending on weight and the air conditions. At low temps you go faster because there is more mass flow per unit volume flow (avgas expands at 0.1%/degK).
“Old” engines are good, they’re just not great. We have that legacy, because of US development, mostly military paying development and certification costs. that’s not happening any more.
I think they are again finally: there are a lot of interesting drone engines e.g. these:
If we want to compare TDI versus AVGAS engines, we could compare two engines sitting on approximately the same airframe: DA40-180 vs DA40D.
I took these numbers from the respective AFMs (with some extrapolation)
DA40-180: 117 KTAS 2000’ ISA 60% BHP 7,7 USG/h – (60% of 180 HP = 108 HP)
DA40D : 117 KTAS 2000’ ISA 70% BHP 4,8 USG/h – (70% of 135 HP = 95 HP)
I expected to find the same power output in terms of HP and cannot explain why it is not the case. But then the DA40-180 I fly cruises about 4 kts faster at F080 than the book value.
DA40-180: 117 KTAS 2000’ ISA 60% BHP 7,7 USG/h – (60% of 180 HP = 108 HP)
DA40D : 117 KTAS 2000’ ISA 70% BHP 4,8 USG/h – (70% of 135 HP = 95 HP)
I wonder if the first one is peak or LOP?
My IO540-C4 would be burning about 9 USG/hr for that HP, but that’s a bigger engine.
But as you say, the thrust must be identical for the same speed, and the HP must therefore be nearly identical because prop efficiency doesn’t vary that much.
I think they are again finally: there are a lot of interesting drone engines e.g. these:
http://www.rotron.co.uk/
Except they have a TBO of 10-50 hours. Except perhaps for the really large ones, drone engines seems to be light and powerful 2 strokes made to be constantly maintained, model airplane engines essentially. Also, the rotary engine is technically a 4 stroke, but practically a 2 stroke regarding lubrication.
For the e-go engine the TBO is 500 hours, not 50.
I had a long chat with them at Farnborough and the ‘overhaul’ for the e-go engine seemed relatively straightforward – primarily a bearing change. They seemed very helpful, and some of the larger engines seemed very attractive (ran on Jet-A). Of course, the real question will be how they perform in service but with the number of hours drones are putting in, some of these companies will be getting real-world experience.
Except perhaps for the really large ones, drone engines seems to be light and powerful 2 strokes made to be constantly maintained, model airplane engines essentially. Also, the rotary engine is technically a 4 stroke, but practically a 2 stroke regarding lubrication.
The best known US government funded UAVs have Rotax 914 engines with modified ancillary systems. They’ve been that way for over 20 years but new production has now made the inevitable cost/capability climb to turboprops. Army funded tactical UAVs used Thielert diesels but with the change to Chinese company ownership that must be ending, which was I imagine the reason for the Lycoming/VM diesel demo. Who knows where that is going.
