And there is no question that they could be more reliable with stuff like electronic engine management/protection
I am not sure because the history of electronics in GA is appalling. I would not want any of what is currently out there on my engine.
Other stuff could be improved but whether it would reduce the chances of a catastrophic in-flight stoppage, I am not sure. That is just basic metallurgy which has been well understood since around WW2.
IMHO the design of these engines is pretty clever. One could do a lot with water cooling but then you would need very good quality components there… And the result would be a much heavier engine – unless you made the engine smaller and extracted the required HP by the use of high RPM which is what Rotax and Thielert have done. And the high RPM needs a gearbox…… 
Peter wrote:
I am not sure because the history of electronics in GA is appalling
But the point is that we don’t want “GA electronics” – we want to reuse existing proven technology that should require no significant further development cost (beyond the certification/paperwork). You will fly an aircraft with a single-shaft magneto, but you wouldn’t fly one with dual Cosworth/Motec/Bosch or similar ECUs?
Peter wrote:
That is just basic metallurgy which has been well understood since around WW2.
We have advances like fractured end caps on conrods, better cylinder lining materials, etc. It is hard to believe that there are no materials or manufacturing advances since 1950 that would provide reliability/performance/efficiency improvements to aero piston engines?
Peter wrote:
IMHO the design of these engines is pretty clever
They were pretty clever in 1950 you mean? I do agree that the simplicity of air cooling and direct drive is still appealing though.
Peter, so you believe a Lyco/Conti of today is more reliable than a Thielert/Austro of today?
I wrote earlier
My own feeling is that the two are on the same order of magnitude – 100k hrs or so. They have to be for the simple reason that most GA pilots would be dead or crippled (or permanently scared of flying again) if the MTBF was say 1k hrs rather than say the 100k hours which is often mentioned re Lycos.
Yes but why do you then mention electronics, liquid cooling and gearboxes as a negative thing? The Merc aero diesels have all that as all modern engines on this planet. If the resulting MTBF (or IFSD – in-flight shut down rate) are comparable then either those features do not make engines more error prone or the core of the engine is significantly more reliable so that in the end the error rate is the same.
Probably, but I don’t see the applicability of this discussion because the only way to change is to sell our planes and buy Diamonds.
Would I do that, change to a DA42, just to get an engine of comparable reliability?
There is no engine swap option for me. SMA never went anywhere, as far as STCs go. Or anywhere else really AFAIK. It was flying in a TB20 10-15 years ago…
The form factor of most planes does not allow geared engines. Only the flat engines will fit.
Also, my mechanic is rather intimately familiar with the DA40/42 and he doesn’t think it would be a net positive move on the maintenance front. In fact he says I would spend 2x to 3x more than I currently do.
my mechanic is rather intimately familiar with the DA40/42 and he doesn’t think it would be a net positive move on the maintenance front. In fact he says I would spend 2x to 3x more than I currently do.
The Thielert saga is really a wonderful example of the ‘German technology takes on the world’ situation that has played out again and again in so many fields of technology. When I lead the design of a piece of equipment I have to deal with the most annoying group of ‘system engineers’ who in collaboration with Marketing, the Program Office and etc develop a very long string of numbers and characteristics that they think drive the market. My guys design to meet that market spec. Generally in the end the whole thing is driven by real world economics as seen by a hard nosed and aggressive international customer who gets a lot of respect… and demands quarterly meetings in which he lays down the law. It’s a very inefficent process but there are no sacred cows. If no new product can meet customer demand better than what already exists, the new product development (and associated budget) is curtailed.
Meanwhile in Germany 
the government creates a fairly extreme tax policy intended to drive technology in some ethereal way, outside of market worldwide demand and preference, outside of real world economics, toward some single number… in this case specific fuel consumption, with seemingly little else that matters. Industry, collaborating closely with government tax policy and respecting it without question, then assigns a couple of smart guys to create a product…. which appears after a period of time and stumbles along for years while the market tries to figure out what the hell they had in mind. Eventually the market might say “well, it kind of matches what I need and it’s got a lot of status” and buy some (or maybe quite a few if they get lucky and the market picks them up)… or alternately perhaps they go broke, particularly so in aviation. In the latter case some features might get picked up by other companies who mate them with designs matching the real world a little more closely.
It really makes me smile. I’m sticking with an O-320 because it works, keeps working, and doesn’t extract scheduled maintenance (parts and labor) from me every year like a haughty girlfriend with a cocaine habit. I say buy whatever works for you. Some guys never get past that kind of modern girls
Silvaire wrote:
German technology takes on the world
German technology cheats the world at the moment. ortac wrote:
The improvements in the reliability engineering on these engines has been virtually zero in the last 50 years.
Don’t forget there is a load of critial accesories around the engine that also directly impact reliability.
This study from 1965-1969 has a figure of 3,855 engine failures for 84,000,000 hours flown. Which is an accident rate of 4.6 per 100,000 hours flown.
Compare that to Achimha’s link that states the FAA these days accepts only 1 per 100,000 hours…
That indicates a significant improvement in reliability. A factor 5, blatantly assuming we’re talking apples and apples here. I believe both figures have excluded pilot-in-command related causes.
Now, since we’re talking about the future of AvGas here, the engine failure rate for PT6 turbine likes is apparently approx. 1 in 100,000 hours. Note that the accident rate may be lower.
[ documents moved to local storage – Peter ]
Silvaire wrote:
outside of real world economics, toward some single number… in this case specific fuel consumption, with seemingly little else that matters.
Yes, who had this crazy idea that fuel consumption is actually relevant, the more the better and best with a lot of lead because that’s what real men emit. If you need to cool your engine, do that with some extra fuel. And if the price gets too high, there’s always some Arab country to invade. Just those damn leftist tree huggers spoiling the party!
achimha wrote:
And if the price gets too high, there’s always some Arab country to invade. Just those damn leftist tree huggers spoiling the party!
