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#111
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Thielert (Diesel Engines)
On Tue, 19 Feb 2008 17:15:11 +0000, David Lesher wrote:
Well, if "old" Diesels made sense for GA use, you'd a thunk there would be lots by now. There don't seem to be. My understanding is that this has, until recently, been a weight issue. [...] There are real issues with starting over, and ignoring everything other But there's a great deal of space between retasking and "starting over, and ignoring everything other people found out The Hard Way". So this is something of a strawman argument. [...] There are significant advantages to engines that run closed-loop, and FADEC control systems add others. Yes, it's best to have zero single points of failure in any design, be it a Bonanza or a highway bridge, [or flywheels] but that's not always possible. This appears to me to be another strawman. Sure, zero SPOF is not always possible. But how does that impact the goal of minimizing the SPOF? Your later comments about granite cumulus would appear to be of the same sort. Hyperbole, perhaps? [...] (The alternative, by the way, is where GA is now -- 1950's technology holds forth; outside of the avionics, and it run on 1960-design alternators.) This might also be explained by the size of the market. Also, don't ignore the "pause" imposed by the liability issue. Now that small GA is "moving again" we are seeing innovation. Avionics has been getting a lot of attention over the past few years thanks to advancements in electronics, and it appears that we're now seeing the result of evolution in the engine market. - Andrew |
#112
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Thielert (Diesel Engines)
Andrew Gideon writes:
Well, if "old" Diesels made sense for GA use, you'd a thunk there would be lots by now. There don't seem to be. My understanding is that this has, until recently, been a weight issue. Note that over the last ~30 years, cars too have come under intense scrutiny over weight, and where to (and not to...) save. It includes things such as making the brake cylinder{s} from aluminum vice steel, reducing the capacity of the automatic transmission case/sump to use less ATF, etc. and many smaller gains. All those ounces add up. There are significant advantages to engines that run closed-loop, and FADEC control systems add others. Yes, it's best to have zero single points of failure in any design, be it a Bonanza or a highway bridge, [or flywheels] but that's not always possible. This appears to me to be another strawman. Sure, zero SPOF is not always possible. But how does that impact the goal of minimizing the SPOF? Your later comments about granite cumulus would appear to be of the same sort. Hyperbole, perhaps? Call them what you want. Zero SPOF is almost never possible. The question is, what do you gain, and how do you mitigate the new risk? That twin with the dead battery is a good example; it was bad engineering to depend on the one main battery for the FADEC's, but with an added gel-cell for them alone, that flaw is 99% gone. [You need some automagic battery test as part of startup.] (The alternative, by the way, is where GA is now -- 1950's technology holds forth; outside of the avionics, and it run on 1960-design alternators.) This might also be explained by the size of the market. Also, don't ignore the "pause" imposed by the liability issue. Now that small GA is "moving again" we are seeing innovation. You think it's moving? I'll let others speak their mind {Jay, Donnie etc.}, but from outside, it looks to me like it's reaching stall speed. GA {in the US} faces large fuel cost increases, an aging fleet, airport losses to developers, and an overall grim economy. And, sooner than you think, I bet leaded gas will vanish. Then what? Does AOPA etc. try to estimate the # of GA hours flown per year? I can see two ways to swag same: ATC data and total gallons of 100 Octane sold. Both have flaws but it might be interesting to see a 10-20 year trend. And I'm not one to discount the coffin corner of low volumes plus regulatory overhead. But what I observe is not a pause but a fergett-it by new vendors coming from such. YMMV. -- A host is a host from coast to & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 |
#113
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Thielert (Diesel Engines)
Andrew,
You need to let go of what you Americans consider to be a "diesel". That's good for trucks and boats, but not for efficient small cars - and airplanes. So how are we to classify the SMA engine? A diesel, but not good for airplanes? Or not a diesel? Ah, let's just say that was not my most coherent posting ;-) But of course you're correct about this being an "old style" engine. That's rather the point. Does that make it a poor choice for aircraft? Numerous articles about flight test, along with commentary by current users, suggests that the SMA engine works quite well in a 182. Hmm. I've heard and read quite the opposite. SMA has never met their goals with regard to certification both of the engine itself and with airframes. They had a ton of cooling problems, AFAIK they still have altitude restrictions which are rather low for a turbocharged engine. They had an airframe from Cirrus to fit the engine to and Cirrus was more than willing to go forward with them, but in the end they gave up because of a mountain of problems. I suspect that it's far cheaper to merely retask an existing engine rather than design anew. Indeed it is. Frank Thielert has described the calculation in a German aviation magazine in detail (from a slighly biased POV, of course ;-)). Very interesting. But that doesn't address the possibility that the retasked engine may not be as appropriate for the new task as the engine designed specifically for that task. True. I'm just looking at the evidence so far. Number of aviation diesels designed from a car engine: 1 (I think). Percentage of those flying in numbers for several years: 100. Number of aviation diesels designed from the ground up: 3 (? - Zoche, sma, Deltahawk). Percentage flying in numbers for several years: 0. And I'd suggest an engine with more failure modes is less desirable - esp. for SE aircraft - than an engine with fewer failure modes. Sure. But just because Bertie says it's so, doesn't mean the Thielert does in fact have more. Different ones, for sure. I also believe that Thielert's ability to get their engines into the market sooner - another benefit of retasking - has made a big difference over SMA. True. They started into it at about the same time, though. sma seems to have run into a wall of problems. Or are there truly technical reasons for the Thielert to be chosen over the SMA? Might OEMs still buy into the SMA (Cessna may not have much choice for 182s, since I don't think Thielert has a good replacement for the O-470)? I think they really tried. I know Cirrus did. Cessna did (as an OEM), too. Socata did. -- Thomas Borchert (EDDH) |
#114
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Thielert (Diesel Engines)
Thomas Borchert writes:
True. I'm just looking at the evidence so far. Number of aviation diesels designed from a car engine: 1 (I think). Percentage of those flying in numbers for several years: 100. Number of aviation diesels designed from the ground up: 3 (? - Zoche, sma, Deltahawk). Percentage flying in numbers for several years: 0. Well, today yes. But Thomas may recall the Luftwaffe Junkers Ju86 used 2-cycle Diesels. I'm sure they did not use FADECs.... -- A host is a host from coast to & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 |
#115
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Thielert (Diesel Engines)
On 21 Feb., 01:10, Peter wrote:
Thomas Borchert wrote True. I'm just looking at the evidence so far. Number of aviation diesels designed from a car engine: 1 (I think). Percentage of those flying in numbers for several years: 100. Number of aviation diesels designed from the ground up: 3 (? - Zoche, sma, Deltahawk). Percentage flying in numbers for several years: 0. Unfortunately this deduction fails to take into account the real market. I could not disagree more with your line of reasoning. ALL players I mentioned come from outside the US (apart from Deltahawk, I think). All entered the field either at the same time as Thielert or well before. Only Thielert has managed to gain any traction in the market, including just recently winning Cessna as an OEM on the 172. One just can't claim that this is all clever marketing and fast action. It's the way the engine is built. BTW, note that Diamond has now started building its own diesel engine. Two remarks regarding that: 1. I guess they don't think the Thielert is perfect, either. 2. Wanna guess what their design is based on? Yep, a Mercedes car engine. Thomas |
#116
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Thielert (Diesel Engines)
"Peter" wrote And what new aircraft are there? It's difficult to sell into the USA (e.g. to Cessna) because a U.S. aircraft maker has to be really careful beta testing new engines (see the Rotax fiasco; the name still stinks in the USA) and because of the U.S. not-invented-here syndrome (call it patriotism if you like but it is an awfully powerful tool to keep people buying the old engines). Correct deduction, wrong reason. The name Rotax stinks because of the quality of the product, not because of where it was invented. It is not tough enough to stand up to the rigors of a plane being flown all day long as a trainer. So spare us the "we won't buy it because it is not American" crap. I'm sick to death of hearing that. Add to that, the fact that Rotax did not get a service capability built up before they brought the Rotax powered planes here. Few people knew how to work on them. Some companies that are selling light sport aircraft with Rotax engines are doing pretty well, but they are providing the necessary training for working on the engines. Many people that own the Rotax engines privately love them. I admit that I am still scared of them. Too many poor experiences with the smaller Rotax engines to believe that the bigger aviation versions could be enough better to be worth my life. Nothing to do with patiotism. Self-preservationism. -- Jim in NC |
#117
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Thielert (Diesel Engines)
On Wed, 20 Feb 2008 11:53:10 +0100, Thomas Borchert wrote:
So how are we to classify the SMA engine? A diesel, but not good for airplanes? Or not a diesel? Ah, let's just say that was not my most coherent posting ;-) Fair enough. I'm sure all those old fashioned diesels accept your apology laugh. But of course you're correct about this being an "old style" engine. That's rather the point. Does that make it a poor choice for aircraft? Numerous articles about flight test, along with commentary by current users, suggests that the SMA engine works quite well in a 182. Hmm. I've heard and read quite the opposite. SMA has never met their goals with regard to certification both of the engine itself and with airframes. I'm not sure what you mean. Scheduling? It's no big shock to me when aviation schedules are extended (esp. regarding certification issues which necessarily involve the FAA). But the SMA is currently certified in at least a couple of 182 models. Plus, users seem happy with it. My club has been looking into SMA-ing a 182Q, so we've collected some opinions from existing customers. Both the names we received from SMA and those we found ourselves (ie. via CPA's forum) seemed to praise the engine. Oddly, I have to admit, this praise came even from a couple of the very first recipients. This is odd to me because they seemed to have a lot of "start up" problems. Perhaps that SMA handled these at no cost swayed the customers' opinions, but I've have considered that a necessity for so new a product. They had a ton of cooling problems, AFAIK they still have altitude restrictions which are rather low for a turbocharged engine. The restriction is FAA/US only. In the EU, those are regularly "violated". So they appear less an engine issue and more a certification issue. They had an airframe from Cirrus to fit the engine to and Cirrus was more than willing to go forward with them, but in the end they gave up because of a mountain of problems. Given the timeframe that SMA and Cirrus were involved together, I can absolutely understand that. [...] But that doesn't address the possibility that the retasked engine may not be as appropriate for the new task as the engine designed specifically for that task. True. I'm just looking at the evidence so far. Number of aviation diesels designed from a car engine: 1 (I think). Percentage of those flying in numbers for several years: 100. Number of aviation diesels designed from the ground up: 3 (? - Zoche, sma, Deltahawk). Percentage flying in numbers for several years: 0. But all of this could be explained by marketing and timing. And I'd suggest an engine with more failure modes is less desirable - esp. for SE aircraft - than an engine with fewer failure modes. Sure. But just because Bertie says it's so, doesn't mean the Thielert does in fact have more. Different ones, for sure. Bertie might be like that proverbial clock, too: correct once or twice a day. What failure modes does the SMA have that the Thielert lacks? That the latter requires electrical power for the FADEC is clear, but what's "the other side"? [...] Or are there truly technical reasons for the Thielert to be chosen over the SMA? Might OEMs still buy into the SMA (Cessna may not have much choice for 182s, since I don't think Thielert has a good replacement for the O-470)? I think they really tried. I know Cirrus did. Cessna did (as an OEM), too. Socata did. But now that the SMA is certified, what might happen? Or is this all for naught now that Continental is [claiming to be] entering the diesel market? - Andrew |
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