Can anyone flying a 9/9A with an O-235 confirm the fuel flow required to cruise at 155 mph? Van's numbers show 151 mph at 55% power with this engine- 64.9 hp X .435 BSFC= 28.2 lbs./hr.= 4.7 US gal/hr.
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Van's Air Force
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Delta Hawk
- Thread starter Mike S
- Start date
Can anyone flying a 9/9A with an O-235 confirm the fuel flow required to cruise at 155 mph? Van's numbers show 151 mph at 55% power with this engine- 64.9 hp X .435 BSFC= 28.2 lbs./hr.= 4.7 US gal/hr.
I've searched some posts and extrapolated some CAFE data for a 320/9A, seems 155 mph with a Lycoming leaned out but not LOP is in the 4.1 to 5.3 GPH range. Different props, C/S permits near WOT and lower rpm for this low power setting. I used Lycoming's published BSFC on their website. I suppose if you ran LOP, fuel flows could be less than the WAM. Given their published spec and the speeds and FFs posted here, .435 does seem in the ballpark. So in this case, 2 stroke diesel and old tech SI engine burn about the same fuel at this low speed.
The Lycoming gives you the ability to do 193 mph should you wish to burn some fuel quickly too.
Gosh, Ross, you win! I'm gonna throw my WAM away and put in a new Lycoming. You have convinced me that there is nothing produced today that is better than good ol' SI technology. Then I'm going to buy myself an old 240Z and go around drag racing 8000 lb diesel trucks. That'll show 'em!
Kurt
Ross,
I think your BSFC data is pretty optimistic. Looking at the Superior IO-360 data in their installation manual, the 60% BSFC is more like 0.48 without going lean. With a CS prop and running LOP, I extrapolate their data to about 0.445 or so. I doubt the O-235 will be better than this - more likley worse. I doubt you'll get it under a real 5gal/hr under any speed near 155mph.
A
I think your BSFC data is pretty optimistic. Looking at the Superior IO-360 data in their installation manual, the 60% BSFC is more like 0.48 without going lean. With a CS prop and running LOP, I extrapolate their data to about 0.445 or so. I doubt the O-235 will be better than this - more likley worse. I doubt you'll get it under a real 5gal/hr under any speed near 155mph.
A
\
I won't get into this debate other than to say I think you might be surprised at what a well tuned 320 or 360 will do at that speed fuel flow wise. There are posts all over the internet with people and their RV's posting real fuel flow number/pictures related to speed. No need to try and "extrapolate" numbers when there are thousands of these things flying and lots of data out there. You may have doubts about the numbers based on extrapolated data, but the reality from those of us flying behind such setups speak for themselves. You can get some crazy/ridiculous fuel flow numbers down at low speeds like that in most of these RV's....especially lightly loaded, well trimmed and at altitude. Some of the 235 and 290 powered -9's have numbers that are laughably small when slowed down a bit.
Anyway, I have no horse in this race other than to say go build what you want, go fly it and report back. I'm eagerly awaiting Ross's RV-10 to see what kind of numbers he gets. In the end, it really doesn't matter that much - as long as you're building that's a good thing!
My 2 cents as usual!
Cheers,
Stein
I'd side with Stein on this. I was looking at actual numbers posted on VAF and some posted on the CAFE 9A test. At this low 135 knot speed, the fuel flows really will be in the 4-5 gph range. Why wouldn't we run an SI engine leaned out at 55% power? Feel free to search out some TAS vs. FF numbers on this forum and work the approx BSFC for yourselves. Sub .40s are common with the IO engines running LOP. .435 makes sense on an O-235 at WOT leaned to peak. A friend with an O-360 FP here gets 180-185 mph at 7.8 gph in a 7A running LOP (yes with a carb). TBO on the low compression O-235 engines is 2400 hours too I believe.
The truth is hard to swallow sometimes if you have preconceived ideas about something. Everyone thinks diesels are so much better in SFC, the reality with 2 stroke designs like the DH and WAM at around .43 are they are not that great and even the Thielert was only marginally better than what the best existing SI engines can do LOP.
By all means, if you like diesel engines and want to have something different and are willing to take a risk with long term support and reliability (like my Subaru), I encourage it. Different flavors for different folks is fine by me.
True life cycle costs from acquisition to overhaul are pretty hard to beat on the Lycoming I think though. Time will tell if these diesel designs really are cheaper in the long haul. There is no way a $62K Delta Hawk will compete however- ever. I think all the flight schools who bought into the diesel myth with Thielert Twin Stars are regretting that decision.
The truth is hard to swallow sometimes if you have preconceived ideas about something. Everyone thinks diesels are so much better in SFC, the reality with 2 stroke designs like the DH and WAM at around .43 are they are not that great and even the Thielert was only marginally better than what the best existing SI engines can do LOP.
By all means, if you like diesel engines and want to have something different and are willing to take a risk with long term support and reliability (like my Subaru), I encourage it. Different flavors for different folks is fine by me.
True life cycle costs from acquisition to overhaul are pretty hard to beat on the Lycoming I think though. Time will tell if these diesel designs really are cheaper in the long haul. There is no way a $62K Delta Hawk will compete however- ever. I think all the flight schools who bought into the diesel myth with Thielert Twin Stars are regretting that decision.
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One thing to consider is that, while SI engines can approach diesel SFC LOP, they are not flown LOP all of the flight. Climb, approaches, and other unusual situations (i.e. "not straight and level leaned") will result in higher SFCs which change your average.
CI engines, on the other hand, are almost always run LOP. The exception might be at higher altitudes where it may be possible to supply more fuel than the oxygen being supplied can oxidize.
CI engines, on the other hand, are almost always run LOP. The exception might be at higher altitudes where it may be possible to supply more fuel than the oxygen being supplied can oxidize.
OK, I got curious and did a slightly interesting thing!
Taking the Van's speed data on the RV-7A at 8000' and fitting a curve through it, I came up with a polynomial that predicts power to TAS (presumably Van's is quoting TAS)
R^2 value for a cubic fit is very close to 1.0 (0.9998) and the polynomial is:
P = 1.6441E-05*TAS^3 + 1.5888E-03*TAS^2 - 5.2399E-01*TAS + 4.8980E+01
Then I knocked up a table that gives fuel flow for assumed SFC numbers.
Speed Power Flow at 0.360lb/hp.h Flow at 0.435lb/hp.h Flow at 0.450lb/hp.h Flow at 0.500lb/hp.h
120 37.4 2.24 2.71 2.80 3.12
130 43.8 2.63 3.18 3.29 3.65
140 51.9 3.11 3.76 3.89 4.32
150 61.6 3.70 4.47 4.62 5.13
155 67.2 4.03 4.87 5.04 5.60
160 73.2 4.39 5.30 5.49 6.10
170 86.6 5.20 6.28 6.49 7.22
180 102.0 6.12 7.40 7.65 8.50
190 119.5 7.17 8.67 8.97 9.96
200 139.3 8.36 10.10 10.44 11.61
210 161.3 9.68 11.69 12.10 13.44
OK, so the formatting is all screwed up, but I think you'll get the gist.
The most interesting thing to me is that when you get close to 4-5gal/hr the difference between a great SFC (0.36) and something that is perhaps average (0.45) the difference in flow isn't all that much, so throwing numbers like 4.5-5gal/hr is tending towards meaninglessness. The fuel flow (and TAS) measurements must be pretty accurate to get good data!
A
Taking the Van's speed data on the RV-7A at 8000' and fitting a curve through it, I came up with a polynomial that predicts power to TAS (presumably Van's is quoting TAS)
R^2 value for a cubic fit is very close to 1.0 (0.9998) and the polynomial is:
P = 1.6441E-05*TAS^3 + 1.5888E-03*TAS^2 - 5.2399E-01*TAS + 4.8980E+01
Then I knocked up a table that gives fuel flow for assumed SFC numbers.
Speed Power Flow at 0.360lb/hp.h Flow at 0.435lb/hp.h Flow at 0.450lb/hp.h Flow at 0.500lb/hp.h
120 37.4 2.24 2.71 2.80 3.12
130 43.8 2.63 3.18 3.29 3.65
140 51.9 3.11 3.76 3.89 4.32
150 61.6 3.70 4.47 4.62 5.13
155 67.2 4.03 4.87 5.04 5.60
160 73.2 4.39 5.30 5.49 6.10
170 86.6 5.20 6.28 6.49 7.22
180 102.0 6.12 7.40 7.65 8.50
190 119.5 7.17 8.67 8.97 9.96
200 139.3 8.36 10.10 10.44 11.61
210 161.3 9.68 11.69 12.10 13.44
OK, so the formatting is all screwed up, but I think you'll get the gist.
The most interesting thing to me is that when you get close to 4-5gal/hr the difference between a great SFC (0.36) and something that is perhaps average (0.45) the difference in flow isn't all that much, so throwing numbers like 4.5-5gal/hr is tending towards meaninglessness. The fuel flow (and TAS) measurements must be pretty accurate to get good data!
A
Yes, I quite agree the diesel will save a meaningful amount here but since we spend a lot more time in cruise at a relatively high power setting unless were are training, long term savings are not that great. WAMs own stated BSFC number at full power was .49- again not that great really by SI standards.
With IE2 coming from Lycoming soon, SI engines will be optimized across the whole operating range. We see similar savings running EFI/EI on the Sube and Lycoming engines in experimentals. Much of the savings are in startup, taxi, climb and descent modes, not in cruise over good manual leaning techniques.
Saving $2-$3 of fuel on a one hour flight is really pretty insignificant compared to the bigger issues of initial cost, maintenance and repair, TBO and cost to overhaul. If you were in Europe and could save $10-$12 per hour on fuel costs- well this becomes significant and over time makes a reliable diesel very attractive.
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diesel engine
heres my take on it
by the time diesel engines are needed in the U.S.A. the electric motor will be the answer its just a matter of storing the juice or producing it
the motor tech is here and now and it will be a quite ride
the motors will last and last
not to change the subject but seeing the sonex clip with jet engine it burns diesel whos going to be the first to hang a pair of large RC jets on a RV
bob
heres my take on it
by the time diesel engines are needed in the U.S.A. the electric motor will be the answer its just a matter of storing the juice or producing it
the motor tech is here and now and it will be a quite ride
the motors will last and last
not to change the subject but seeing the sonex clip with jet engine it burns diesel whos going to be the first to hang a pair of large RC jets on a RV
bob
CMD engine - another Aero Diesel
another diesel aero engine here.
Developed over in Italy, but unfortunately, their website (www.cmdengine.com) has lapsed. I bet not many in the world know much about it, but if anyone does, I'd be keen on the inside goss!
Large-ish (can't remember the details) but 400hp. To big for a direct replacement to an IO-540 if my memory is correct.
another diesel aero engine here.
Developed over in Italy, but unfortunately, their website (www.cmdengine.com) has lapsed. I bet not many in the world know much about it, but if anyone does, I'd be keen on the inside goss!
Large-ish (can't remember the details) but 400hp. To big for a direct replacement to an IO-540 if my memory is correct.
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Building a new engine design for a small market like this is pretty hard financially and rarely does anyone succeed. I guess WAM has in very low volume production which is amazing given the reasonable price tag- for how long, nobody knows. Kudos nonetheless.
Jabiru seems to be the last, big success as far as numbers go. Many teething problems after initial introduction but they have slugged it out. That was a long time ago now.
A few like HKS have designed and sold a number of lower hp engines.
There seems no shortage of engineers wanting to design new aero engines, they just seem to lack the funding and business plan to make it a long term success.
I salute all these guys who tried to design and build their dreams.
Jabiru seems to be the last, big success as far as numbers go. Many teething problems after initial introduction but they have slugged it out. That was a long time ago now.
A few like HKS have designed and sold a number of lower hp engines.
There seems no shortage of engineers wanting to design new aero engines, they just seem to lack the funding and business plan to make it a long term success.
I salute all these guys who tried to design and build their dreams.
Don't know if anyone else has been checking, but this page appears to be new. Looks like they're quoting $40,000 for the 200hp engine without some accessories, $60,000 for a "firewall forward kit," and implying a 6 month delivery time. They also seem to be optimistic about certification - probably their engines delivered working on drones has helped in that regard.
Bubblehead
Well Known Member
I realize that the DeltaHawk website is trying to give an apples to oranges comparison but it is a little deceiving because they are showing a Lyc with turbo. Very few RVers have chosen a turbocharged system, but the diesel requires it. That is 11,000 of the difference. Van's engine price is also about $2000 less than the Delta Hawk assumed engine price.
The FWF price is inflated too. Van's sells the FWF kit for the 200 hp Lyc for $5,130 but the DeltaHawk site prices a FWF kit at $12,900.
They show a EI engine instrumentation system for the Lyc for $3100 but a system using Vans gages is much less. My GRT EIS-4000 system was about $1,000.
I think the more realistic price comparison is $62,500 for the diesel and $48,385 for the Lyc for RV use.
The FWF price is inflated too. Van's sells the FWF kit for the 200 hp Lyc for $5,130 but the DeltaHawk site prices a FWF kit at $12,900.
They show a EI engine instrumentation system for the Lyc for $3100 but a system using Vans gages is much less. My GRT EIS-4000 system was about $1,000.
I think the more realistic price comparison is $62,500 for the diesel and $48,385 for the Lyc for RV use.
LoPresti has received their first 200 hp engine destined for their Cirrus SR20 test bird.
http://www.flightglobal.com/news/articles/lopresti-november-flight-for-upgraded-sr20-362230/
Certified engine, cowling and propeller will practically be GIVEN AWAY at a measly $100,000.
http://www.flightglobal.com/news/articles/lopresti-november-flight-for-upgraded-sr20-362230/
Certified engine, cowling and propeller will practically be GIVEN AWAY at a measly $100,000.
Another one...
http://www.dukeengines.com/ Here is another option currently in development.
Don't know much about this other than the website info and a short article that appeared a while ago in Sport Aviation. Did get to see it at the 'Flair' aviation expo today http://www.nzflair.com/flair-brochure.pdf . Certainly looks the part, but will it perform as claimed?...no idea!
Clive Whittfield
Auckland
New Zealand
RV6 (very) slow build in progress
http://www.dukeengines.com/ Here is another option currently in development.
Don't know much about this other than the website info and a short article that appeared a while ago in Sport Aviation. Did get to see it at the 'Flair' aviation expo today http://www.nzflair.com/flair-brochure.pdf . Certainly looks the part, but will it perform as claimed?...no idea!
Clive Whittfield
Auckland
New Zealand
RV6 (very) slow build in progress
DonFromTX
Well Known Member
Is this because you know some facts about the Viking engine, or that you just did not want him to know?
We did happen to stumble on the Eggenfellner booth. My son-in-law was quite taken by the display as it showed off some visually actractive engine/psru FF packages. I told him to keep walking and I'd explain later.
Captain Avgas
Well Known Member
DeltaHawk were exhibitors at the Avalon Airshow (had a prototype engine on display) when I was there in March 2003. They were taking orders then for "shipment approx August". The trouble was that no-one knew they were talking about August 2012....and even that must now be doubtful.
Flyfalcons
Well Known Member
Was the Viking even around in 2009?
AK4x4
Well Known Member
I have followed Delta Hawk for some time and thought it would be a nice match for an RV-7......unfortunatly they have hitched their wagon to the certified aircraft market....and the rediculous associated costs. To bad really as I think an experamental FWF package in the 30-35K range could have been huge. Russ
detlef lili
Well Known Member
No reliable company
Yes, Russ I agree with you, but all other diesel engines on the market have to little power.
Two weeks ago, I wrote them an email and they didn't answer until now. They made so much publicity for the experimental market. And now...., forget this company.
They have to pay the bill later. It's only a short step running out of business.
Detlef
Yes, Russ I agree with you, but all other diesel engines on the market have to little power.
Two weeks ago, I wrote them an email and they didn't answer until now. They made so much publicity for the experimental market. And now...., forget this company.
They have to pay the bill later. It's only a short step running out of business.
Detlef
smokyray
Well Known Member
Samo, samo...
Check out this video...listen to the price quote on the engine.
http://www.aero-news.net/index.cfm?do=video.playVideo&videoid=0d19e3fc-d33b-4370-8280-beec0d38a69b
Smokey
Check out this video...listen to the price quote on the engine.
http://www.aero-news.net/index.cfm?do=video.playVideo&videoid=0d19e3fc-d33b-4370-8280-beec0d38a69b
Smokey
mill2978
Well Known Member
John Clark
Well Known Member
My favorite line is, "I'll let you know after we do the thermal testing".
John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
The prices appears to line up don't they? 40-something for the engine, 20-something for the FWF. The DH site was talking 60-ish for a complete engine+FWF kit. Then add 15-ish for the the cowling... that's a lot of money compared to other aftermarket cowls, although I suppose one is buying a lot of efficiency and a solution to difficult problem (and perhaps certainty of fuel supply longer term).
Still, if it does what their models predict it's an impressive piece of engineering.
Still, if it does what their models predict it's an impressive piece of engineering.
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DH Pricing
Remember, these prices are for a certified engine and FWF package. If they ever get these engines on the market, the fact that it is certified may be beneficial to us experimental guys in the long haul. If they find certified oem's to supply the DH option (and they will), it should mean higher volumes and eventually lower prices for experimental guys. There will be plenty of us willing to develop a FWF package for different airframes, so the cost doesn't have to be nearly as high as for a certified airplane.
For all you traditional engine fans, let me say that you don't know what you're missing. As many of you know, I fly regularly (280 hours so far, since Nov '08) behind a two stroke turbo diesel, and I will never go back to a traditional engine.
I'll be glad to pay $40k for a DH once (if!) they become available. The economy, safety, simplicity, and power at altitude are worth it!
Kurt
RV9 / Wilksch 120 diesel
Remember, these prices are for a certified engine and FWF package. If they ever get these engines on the market, the fact that it is certified may be beneficial to us experimental guys in the long haul. If they find certified oem's to supply the DH option (and they will), it should mean higher volumes and eventually lower prices for experimental guys. There will be plenty of us willing to develop a FWF package for different airframes, so the cost doesn't have to be nearly as high as for a certified airplane.
For all you traditional engine fans, let me say that you don't know what you're missing. As many of you know, I fly regularly (280 hours so far, since Nov '08) behind a two stroke turbo diesel, and I will never go back to a traditional engine.
I'll be glad to pay $40k for a DH once (if!) they become available. The economy, safety, simplicity, and power at altitude are worth it!
Kurt
RV9 / Wilksch 120 diesel
L.Adamson
Well Known Member
I've been running diesel Silverado pickup trucks for quite a number of years now. I live in mountain country, and prefer the way they haul heavy loads up hill. I have no inkling to go back to gasoline powered trucks at all.
But at the same time, I just have no desire to install a diesel in my airplanes. I prefer the Lycs. Strange.....huh..
L.Adamson
I'd be waiting to see how the DH pans out in the real world before laying down any money. Just because it will be certified does not mean it will be trouble free. The Thielert was certified but was a complete disaster and the SMA has faired little better, again not living up to projected TBOs. I think it will be quite some time before the Lycoming is unseated as the popular choice for GA.
A few engines with a few hours means little in the big scheme of things as far as demonstrated reliability goes. I've got 350 trouble free hours on my Subaru now but this is just a drop in the bucket really.
A few engines with a few hours means little in the big scheme of things as far as demonstrated reliability goes. I've got 350 trouble free hours on my Subaru now but this is just a drop in the bucket really.
We are the real world
The way I see it, we are part of the "real world". At one point, Lycoming engines were certified, and pilots just like us flew them, and built hours. There were problems. There still are problems. But if newer more efficient technologies are to be developed, someone has to do it. Over time, the diesels (or electric, or whatever) are going to have to build hours and work the bugs out, just like the traditionals have, and continue, to do.
With regard to the Thielert, they have racked up almost 3 million flying hours, not exactly what I would call a "disaster"! Their business practices, leading to receivership? Yes, a disaster. But a "less than the GA average of in-flight shut downs", along with the accumulated hours indicates they're doing something right. I understand that there is probably a "higher than average" amount of maintenance required to achieve this good reliability record, but they are whittling away at the issues, even in receivership. All this with a converted auto engine, which I do not think is the way to go.
My point is that, while I agree with Ross that the proof will be in the pudding, we'll never get anywhere as long as we stay in "the box", never getting out and proving (and improving) better technology.
Kurt
The way I see it, we are part of the "real world". At one point, Lycoming engines were certified, and pilots just like us flew them, and built hours. There were problems. There still are problems. But if newer more efficient technologies are to be developed, someone has to do it. Over time, the diesels (or electric, or whatever) are going to have to build hours and work the bugs out, just like the traditionals have, and continue, to do.
With regard to the Thielert, they have racked up almost 3 million flying hours, not exactly what I would call a "disaster"! Their business practices, leading to receivership? Yes, a disaster. But a "less than the GA average of in-flight shut downs", along with the accumulated hours indicates they're doing something right. I understand that there is probably a "higher than average" amount of maintenance required to achieve this good reliability record, but they are whittling away at the issues, even in receivership. All this with a converted auto engine, which I do not think is the way to go.
My point is that, while I agree with Ross that the proof will be in the pudding, we'll never get anywhere as long as we stay in "the box", never getting out and proving (and improving) better technology.
Kurt
Yes, I applaud the efforts of any new companies coming into aviation attempting to bring new engines into the marketplace. As Kurt says, nothing will ever change unless some new things are tried and eventually proven.
The truth though in aviation is that nothing is sound until well flight proven to be so. Even the new engines from GE, RR, Pratt and CFM powering new twin jet airliners are not fully approved for all over water routes until substantial actual flight time and reliability history is accumulated. Even then, stuff does happen as seen on the RR powered A 380s. Nothing is perfect, despite hundreds of millions of dollars of R&D.
The Thielert was not especially prone to catastrophic failure but rather, slow, well premature ring/ piston death and frequent teardowns of the clutch for inspections. This meant the overall operating cost per flight hour were well beyond projections and the downtime was added to that cost, especially for flight schools. Lawsuits in Europe flew and disgruntled operators either dumped the aircraft or waited out a better idea, hopefully in the form of the new Austro engine. Operators had to use them or sell them so yes, they accumulated a decent amount of flight hours but simply did not even come close to delivering on lower operating costs or TBR.
The DA42 here was apart more than it was together after many problems, SBs and inspections. I saw the clutch apart on the Thielert once and it was just a stupid design IMO. These engines simply were not viable as delivered with removals taking place at 200-500 hours typically due to excessive oil consumption.
No doubt Thielert has learned and improved on the original design however the DA42 is no longer being produced with their engines. SMA under new ownership is also no doubt applying fixes to bring engine life up to the expected levels. At the same time these things are happening, the costs for the manufacturer and clients goes up through warranty claims, new engineering costs and maintenance costs, making people wonder if the high initial and operating costs were worth it compared to the fuel savings. With the new costs having to be eventually passed on to the market to ensure corporate survival, the overall economic premise is put into question. Indeed, the fiscal problems at Thielert were, in large part, due to an unsustainable model partly caused by what was an insufficiently developed design. I don't think you can call their attempt successful. The good sales of diesel Diamonds was based a lot more on marketing hype than real world overall operating savings.
What I'm trying to say with all of this is that DH will also have to prove that initial costs, operating costs and reliability are at least as good as the crusty old Lycoming on a per flight hour basis. Lower fuel flows are meaningless in the big picture if the engine costs 50% or 100% more to acquire and has to be replaced prematurely. DH has had many years now (!) to complete exhaustive testing and redesign prior to market release so expectations will be very high for this expensive engine.
One does start to wonder how viable their financial model is though after all these years of engineering and development and the substantial costs involved. How many engines do they have to sell and at what price to just get back to even now? In reality, often these costs sink a new aero engine project almost before the first engine is delivered. The reality being that overall, the project must show a profit to stay alive.
A sound mechanical design coupled with a sustainable and realistic financial plan is the only way any new engine design, either SI or CI, will be with us for as long as the Lycoming. I truly wish DH, Austro and SMA the best of luck here. In many parts of the world, good diesel designs are really needed and who wouldn't want truly lower operating costs and fuel flows? The problem is, nobody has done this yet with an aero diesel so I suspect it is not as easy as it seems. SMA almost certainly never turned a real profit on the low number of engines delivered and having to fix so many under warranty. When someone can offer a $20-$25,000 180-200 hp diesel which really does go consistently 2000+ hours before overhaul, without costly inspections and maintenance, while burning 25% less fuel than a Lycoming, then the day will have truly arrived. As I have said before, the very high gas loadings, vibration characteristics and high continuous power settings in aviation use make the design of a competitively priced, reliable, long lived, lightweight aero diesel very challenging to designers and manufacturers. If it was easy, someone would have done it decades ago because the diesel has been around for a very long time now.
The truth though in aviation is that nothing is sound until well flight proven to be so. Even the new engines from GE, RR, Pratt and CFM powering new twin jet airliners are not fully approved for all over water routes until substantial actual flight time and reliability history is accumulated. Even then, stuff does happen as seen on the RR powered A 380s. Nothing is perfect, despite hundreds of millions of dollars of R&D.
The Thielert was not especially prone to catastrophic failure but rather, slow, well premature ring/ piston death and frequent teardowns of the clutch for inspections. This meant the overall operating cost per flight hour were well beyond projections and the downtime was added to that cost, especially for flight schools. Lawsuits in Europe flew and disgruntled operators either dumped the aircraft or waited out a better idea, hopefully in the form of the new Austro engine. Operators had to use them or sell them so yes, they accumulated a decent amount of flight hours but simply did not even come close to delivering on lower operating costs or TBR.
The DA42 here was apart more than it was together after many problems, SBs and inspections. I saw the clutch apart on the Thielert once and it was just a stupid design IMO. These engines simply were not viable as delivered with removals taking place at 200-500 hours typically due to excessive oil consumption.
No doubt Thielert has learned and improved on the original design however the DA42 is no longer being produced with their engines. SMA under new ownership is also no doubt applying fixes to bring engine life up to the expected levels. At the same time these things are happening, the costs for the manufacturer and clients goes up through warranty claims, new engineering costs and maintenance costs, making people wonder if the high initial and operating costs were worth it compared to the fuel savings. With the new costs having to be eventually passed on to the market to ensure corporate survival, the overall economic premise is put into question. Indeed, the fiscal problems at Thielert were, in large part, due to an unsustainable model partly caused by what was an insufficiently developed design. I don't think you can call their attempt successful. The good sales of diesel Diamonds was based a lot more on marketing hype than real world overall operating savings.
What I'm trying to say with all of this is that DH will also have to prove that initial costs, operating costs and reliability are at least as good as the crusty old Lycoming on a per flight hour basis. Lower fuel flows are meaningless in the big picture if the engine costs 50% or 100% more to acquire and has to be replaced prematurely. DH has had many years now (!) to complete exhaustive testing and redesign prior to market release so expectations will be very high for this expensive engine.
One does start to wonder how viable their financial model is though after all these years of engineering and development and the substantial costs involved. How many engines do they have to sell and at what price to just get back to even now? In reality, often these costs sink a new aero engine project almost before the first engine is delivered. The reality being that overall, the project must show a profit to stay alive.
A sound mechanical design coupled with a sustainable and realistic financial plan is the only way any new engine design, either SI or CI, will be with us for as long as the Lycoming. I truly wish DH, Austro and SMA the best of luck here. In many parts of the world, good diesel designs are really needed and who wouldn't want truly lower operating costs and fuel flows? The problem is, nobody has done this yet with an aero diesel so I suspect it is not as easy as it seems. SMA almost certainly never turned a real profit on the low number of engines delivered and having to fix so many under warranty. When someone can offer a $20-$25,000 180-200 hp diesel which really does go consistently 2000+ hours before overhaul, without costly inspections and maintenance, while burning 25% less fuel than a Lycoming, then the day will have truly arrived. As I have said before, the very high gas loadings, vibration characteristics and high continuous power settings in aviation use make the design of a competitively priced, reliable, long lived, lightweight aero diesel very challenging to designers and manufacturers. If it was easy, someone would have done it decades ago because the diesel has been around for a very long time now.
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detlef lili
Well Known Member
Hi Russ!
I agree 100% with you. It makes no sense to spend 20-30,000 bucks more, for 25% fuel saving.
I spotted also the diesel engine market for a long time,since avgas is not all over the world available.
We ended up with a Superior IO-360 with Dual Lightspeed Ignition and a fine tuned Airflow Injection System which is 100% ethanol proof.
Since more than 400 hours we are flying now on car gas with a minimum of 91 Oct. without any problems.
Even in Brazil we used the car gas which is mixed with 30% Ethanol.
A couple of years ago, I heard something about SMART Spark Plugs, thats allows you also to use diesel. The system is patented, but the website looks abandoned. The problem of all this new stuff is the big amount of money you must have to develop the details.
Greeting from Sosua, Dominican Republic
Detlef
I agree 100% with you. It makes no sense to spend 20-30,000 bucks more, for 25% fuel saving.
I spotted also the diesel engine market for a long time,since avgas is not all over the world available.
We ended up with a Superior IO-360 with Dual Lightspeed Ignition and a fine tuned Airflow Injection System which is 100% ethanol proof.
Since more than 400 hours we are flying now on car gas with a minimum of 91 Oct. without any problems.
Even in Brazil we used the car gas which is mixed with 30% Ethanol.
A couple of years ago, I heard something about SMART Spark Plugs, thats allows you also to use diesel. The system is patented, but the website looks abandoned. The problem of all this new stuff is the big amount of money you must have to develop the details.
Greeting from Sosua, Dominican Republic
Detlef
