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Aerodiesels: Progress, If Not Thriving

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Jet-A burning diesel aeroengines, we're led to believe, are the future of general aviation propulsion. So at Aero last week, I expected the place to be lousy with them. Well, not quite. There were a couple of new ones—SMA's six-cylinder concept engine and the nice little three-cylinder SmartCar conversion from FlyEco, but also some MIAs. Notably absent was Red/Raikhlin's 12-cylinder behemoth, which made the rounds last year, and Continental's TD300, which was quietly certified last December with absolutely no announcement whatsoever.

Cessna was expected to fly in its new SMA SR305-powered JT-A 182, but it didn't show because of weather, we were told. However, Diamond did have on display a detailed mockup of its new larger twin, the DA52 VII, powered by new variants of the Austro AE300 at 180 HP each. I got a flight demo in that aircraft after the show and found it quite impressive. More on that at a later date.

For now, the diesel market is to the overall engine market as LSAs are to overall airframe market. The technology has a foothold, but it's not yet dominant, despite the ongoing and perhaps worsening lack of confidence in avgas supplies. This would seem to present the ideal climate for diesels to explode in popularity, but perhaps with the exception of Diamond, the march to a Jet-A world seems to be a wandering meander. There's definite interest and progress, mind you, but it's slow. Consider that the U.S.-based DeltaHawk admits that it probably has the longest running engine cert project in aviation history.

The real surprise to me is Continental, which has vigorously committed to diesel, developing technology acquired from SMA for its own family of diesels. In this podcast last week, Continental's Rhett Ross said the company is certain Jet-A technology will open markets throughout the world, yet it's currently almost downplaying its own diesel. They didn't have it at Sun 'n Fun either and made no announcement of the certification. No one is saying why, but I surmise it might be a legal skirmish with SMA. We're told to expect big announcements at Oshkosh or later in the year. They've got an OEM and my blue sky guess is that it would be Cirrus, with a diesel-powered SR20. The SR22 would be a better candidate, but it will need more horsepower than the four-cylinder TD300 can deliver.

Ross's counterpart at Lycoming, Michael Kraft, said "interesting question" when asked if Lycoming had its own diesel in the works. Last summer, Lycoming announced that it would provide service and overhaul support for the SMA diesel, but there aren't yet enough of those in the field to make a dent in the market. Kraft has always said he thought the uptake of diesel would be slow, and it now looks like that's exactly what's happening. Still, I wouldn't be surprised to see some kind of announcement from Lycoming that either expands on the SMA agreement with regard to OEM work or conversions and/or a homegrown diesel from Lycoming. Sooner or later, the market is bound to turn in diesel's favor if we're not seeing it—in slow motion—already. And you can't sell what you haven't developed.

If the diesel market seems slow now, it wasn't always. It's fair to say Diamond pioneered the OEM diesel market with the Thielert-powered DA42. At the time of its introduction, I thought that (a) there was no market for a new twin and (b) even less of one with diesel engines. Wrong and wrong. Despite what seemed like a high asking price of $460,000, the DA42 proved hot, selling up to three a week during the 2005 to 2008 period. Counting singles and twins, Diamond has some 900 diesel-powered airplanes flying. In the current market, that's a big number.

What tanked it? Diamond CEO Christian Dries says Thielert's bankruptcy and subsequent jacking of prices to turbine levels made any more major OEM inroads unlikely. Recall that Thielert got into trouble before the recession and after the financial meltdown, its market prospects were unlikely to improve and didn't. Thielert has been operating in insolvency for five years and won't comment on any prospects for exiting that state. It thus seems unlikely that it will develop new products or even significantly improve what it has until that happens. Thielert engines are still hobbled by requirements for recurrent clutch and gearbox inspections. It's difficult to imagine that this model will remain competitive with Austro's and SMA's more powerful models that don't require the inspections. Long term, I don't think customers will put up with that if there's a choice.

Anyone who thinks gasoline technology is done better let Rotax know. The company's 912 iS is finding strong market traction, with some 300 in the field. At Aero, Rotax showed some test data that indicated the engine's fuel economy is considerably better than first claimed.

Life cycle costs of diesels are still a moving target. Given the low volume and high manufacturing costs, they're expensive to build and any recurrent replacement parts, such as pumps or gearboxes, only adds to that. The last analysis I did on the Austro AE300 against a Lycoming IO-360 yielded a $53.53 per hour cost for the Austro—inclusive of fuel—versus $66.50 for the Lycoming, not including any mid-run cylinder overhauls or typical mag work.

That's good, but not necessarily slam dunk if the diesel is more expensive to buy. Where it turns the corner is if diesels get to the high TBOs they are known for—say 2400 or even 3000 hours. If that happens, diesel economics are undeniably attractive. Of course, if you're in a part of the world where Jet-A is the only fuel available, the comparison is moot.

And that's what the diesel camp is counting on.

Comments (36)

"Consider that the U.S.-based DeltaHawk admits that it probably has the longest running engine cert project in aviation history." Call me cynical, but as long as investment money flows into that company, it seems they can't be bothered with such pesky details as actually producing them. So far their target price has doubled too. I guess they are following the Zoche business model when it comes to engine development. This is a Diesel engine, folks - not rocket science.

Posted by: Peter Thomas | May 2, 2013 2:29 PM    Report this comment

The progress with diesel and gasoline powered aircraft engines are just not keeping pace with other users (cars). With some small exceptions (Rotax and Diamond), no one is putting serious effort into developing (Lycoming and Continental) new technology or implementing it (Cessna, Cirrus, or even Van's). The dithering about Avgas vs Jet-A vs other continues to hurt the prospects for the future and no one is willing to "commit" to a long term solution. Oil is not getting any cheaper, and what aviation needs is a way to reduce cost and improve the pilot/aircraft interface!

With that kind of situation, what might very well is that aircraft will follow the auto market into electric propulsion. Yes, it will take a long time to change over, but power is power. No question about "fuels", low wear on components, simple electronic interfaces (which is not a feature, but people gravitate towards it these days). There is LOTS of investment in this area on the automotive side for the motors, and even more from the battery side (including cell phones and all other electric devices). Btw, the infrastructure problem is largely being solved by others already: do all hangers have power? yes! are power companies installing fast-chargers for cars in houses? yes!

GA is a small market. If we want to know where GA is going, you have to look at who is making BIG investments in technology: car and cellphone producers. GA will have to leverage these developments to continue to improve.

Posted by: Jeffrey Smith | May 2, 2013 5:34 PM    Report this comment

"With some small exceptions (Rotax and Diamond), no one is putting serious effort into developing (Lycoming and Continental) new technology or implementing it."

Not to offer an apologia, but I'm not sure what you consider serious. In recent history, Continental invested multiple millions in FADEC technology that used state of the art automotive technology. Lycoming's IE2 technology is similarly a major investment for what is essentially a small company.

Thielert's development of the OM640 was certainly in the multiple millions, too, to sell, thus far, perhaps a couple of thousand engines at most. MB makes that many in a day for its car market. Austro invested $100 million to bring its own version of the OM640 to market.

Recall that Rotax probably invested at least $10 million to bring its aborted V-6 to market. It had OEM takers in Cirrus and Diamond.

Would you call these not serious? It's not really clear why they stumbled, but they did, including Thielert. It's a tough market to make money in with profoundly risky returns on investment.

Posted by: Paul Bertorelli | May 3, 2013 4:27 AM    Report this comment

Diesel engines have been the "next big thing" in aviation for about a hundred years...and counting. Think of all the incredible advances in aviation, computers, medicine, science, and bottled water. But still no cure for the common cold or an economically viable diesel aircraft engine.

Posted by: Richard Montague | May 3, 2013 8:06 AM    Report this comment

"Diesel engines have been the "next big thing" in aviation for about a hundred years..." because they had to compete with gasoline-fueled engines and the infrastructure that supported them. Aviation gasoline is going away. In the post-gasoline environment, diesel will be the only alternative to turbines. For sub- $2million aircraft, that will make diesel the powerplant of choice. And it will make economic sense to re-engine a Saratoga with a $70,000 diesel, in lieu of either buying a (by then) $1million Cirrus single, or parting out the 'Toga and taking a bus to your destinations.

Dreams about electric airplanes are of the wet kind. Simple physics rules out hauling 4-6 people 1,000 NM at 200 KTS on battery power. There's a reason that vehicles from Cessna's new 182 through the Saturn 5 have been powered by kerosene. Physical chemistry.

Posted by: Thomas Yarsley | May 3, 2013 8:22 AM    Report this comment

I recall similar questions in the U.S. a decade ago regarding the Rotax, by far the most important powerplant for training and LSA aircraft today. Diesels too will take time to evolve, and they will come from Europe, where diesel automobile engines are highly refined, clean, efficient, peppy and very popular. The American perception of diesel engines is mired in memories of black clouds of soot behind old Mercedes from the 70s. We also have only recently made the switch to ULSD low sulfur diesel fuels. The folks at JAARS (mission aviation in Waxhaw, NC) recently told me that their Jet-A burning C-182s are the most efficient aircraft in their fleet, which includes the Helios and the Quest Kodiak turboprop. While aircraft diesels have been around since the 1930s (Zeppelin and Junkers flew with them), they have a ways to go in price and weight. Since though SMA is using a commodity Renault engine, and Austro a Mercedes diesel, there is a good chance they'll make it. On Thielert - their main early problem was their use of an aluminum block and its lack of stiffness. Austro wisely stuck with the stiffer original steel block from the Mercedes engine. Thielert also suffered from a corrupt CFO. Since lead-free Jet-A fuel and small auto diesels are however so ubiquitous, we can expect to see more of them in the future, for sure. Free markets will work this all out as long as the government lets them.

Posted by: Kent Misegades | May 3, 2013 9:17 AM    Report this comment

I hope that diesels will eventually give the industry the shot in the arm it needs. Ideally, a liquid-cooled diesel would allow an enclosed cowling, eliminating most cooling drag (except for radiator intakes/exhaust).

I'm curious to see how successful Pipistrel's Panthera hybrid turns out to be. I'm as skeptical as the next guy, but the idea makes sense to me. IIRC their design uses an engine to turn a generator which provides power to an electric motor turning the prop - I'd think this setup would be significantly more efficient than a conventional Lyc/Cont. Still waiting to see if their IO-390 powered Panthera manages 200kt on 10gph though.

Posted by: Will Alibrandi | May 3, 2013 10:04 AM    Report this comment

Regarding the DA 42 NG there are a few things. First, I believe your cost numbers are, well, optimistic. In 12 months and 4400 hours of operation on 4 airplanes, we've spent an average of $44/hr on fuel alone.

The engines are approximately 64k a piece for new. Yes, Diamond advertises about half that for an overhauled version...of which they cannot supply. According to Diamond's Austro Engine division, they do not have the process for overhauling the engines yet in place. (we're now approaching our second set of engine changes) Diamond also advertises that they will "prorate" the engine costs based off the current TBO compared to the goal of 2000. This has also been very difficult to get Diamond to comply with, in fact...we had to take parts credit in place of the reduced price on our last engine replacements.

Continued Below:

Posted by: Jared Testa | May 3, 2013 10:08 AM    Report this comment

Continued From Above:

The engine is pretty bulletproof, but there have been a consistent amount of accessory problems and manufacturing defects discovered. Most recently, an engine shut down for training resulted in a propeller that wouldn't come out of feather. After checking the usual suspects and replacing the governor, it happened again. The end result? An over-crimped wire on a circuit board that was making intermittent contact.

The amount of labor taken to maintain the airplane is DOUBLE what Diamond advertises.

It actually pains me to write this. This airplane is a poster-child for "love-hate relationships". I have never flown an airplane that I enjoyed flying more than this airplane, perhaps with the exception of the beloved 208. Flying this airplane is great, and then when I get to my office and deal with managing an operation of four of them flying 100hrs a month, I think about wanting to call Vero Beach.

Diamond needs to pull their proverbial head out of their proverbial rear-ends and come up with a logical, efficient, effective North American support program. Diamond North America is nearly defunct and seems to have themselves handcuffed by Austria. If Diamond wants to really sell this airplane in the North American market, they need a comprehensive support strategy...which they are very much lacking.

Disclaimer: These are my personal views, not necessarily those of my employer.

Posted by: Jared Testa | May 3, 2013 10:09 AM    Report this comment

The engine is pretty bulletproof, but there have been a consistent amount of accessory problems and manufacturing defects discovered. Most recently, an engine shut down for training resulted in a propeller that wouldn't come out of feather. After checking the usual suspects and replacing the governor, it happened again. The end result? An over-crimped wire on a circuit board that was making intermittent contact.

The amount of labor taken to maintain the airplane is DOUBLE what Diamond advertises.

It actually pains me to write this. This airplane is a poster-child for "love-hate relationships". I have never flown an airplane that I enjoyed flying more than this airplane, perhaps with the exception of the beloved 208. Flying this airplane is great, and then when I get to my office and deal with managing an operation of four of them flying 100hrs a month, I think about wanting to call Vero Beach.

Diamond needs to pull their proverbial head out of their proverbial rear-ends and come up with a logical, efficient, effective North American support program. Diamond North America is nearly defunct and seems to have themselves handcuffed by Austria. If Diamond wants to really sell this airplane in the North American market, they need a comprehensive support strategy...which they are very much lacking.

Disclaimer: These are my personal views, not necessarily those of my employer.

Posted by: Jared Testa | May 3, 2013 10:09 AM    Report this comment

The engine is pretty bulletproof, but there have been a consistent amount of accessory problems and manufacturing defects discovered. Most recently, an engine shut down for training resulted in a propeller that wouldn't come out of feather. After checking the usual suspects and replacing the governor, it happened again. The end result? An over-crimped wire on a circuit board that was making intermittent contact.

The amount of labor taken to maintain the airplane is DOUBLE what Diamond advertises.

It actually pains me to write this. This airplane is a poster-child for "love-hate relationships". I have never flown an airplane that I enjoyed flying more than this airplane, perhaps with the exception of the beloved 208.

Posted by: Jared Testa | May 3, 2013 10:12 AM    Report this comment

One additional perspective... most diesel engine manufacturers are developing engines in the 200 HP range as a starter. I just wonder if it might be a bit backward? The larger displacement engines are where the real fuel and wear savings come from, more sales are likely here than replacing the engine in a Arrow. Plus most of these engines are used in twins which means two engine sales per aircraft. In a twin a four gallon per hour per engine fuel saving is huge and you'll get lots of attention with this group.

Posted by: Jim Kabrajee | May 3, 2013 10:38 AM    Report this comment

Paul,

Great coverage from Europe. I was most interested in the Flyeco diesel because I agree with Jeffrey Smith above that our best way forward might involve leaveraging tech from bigger industries. That little diesel seems perfectly suited to 600kg LSAs that run happily on 80hp like the Jabiru j170 et al. 95 to 100 knots on just under 2 US Gallons an hour? That is actually awesome!

This diesel issue annoys me immensely due to having following the NASA GAP program in the "noughties". Where did all that money go? It seems like a cast iron scandal. Now it looks like any development is coming from the private sector, despite all that public money being spent and big companies getting involved. Where is Continental's 2 stroke diesel? Did they buy the tech and bury it to avoid hurting their existing business? Now that the avgas chickens are coming home to roost, I'm expecting more people to start asking questions.

Posted by: john hogan | May 3, 2013 11:17 AM    Report this comment

In the ground vehicle world a successful diesel only needs to be rugged & dependable; a few (or even a bunch) of extra pounds of weight can be tolerated to achieve this, and accommodating the bulky liquid cooling systems needed for all-condition operation presents only a minor problem. Improvements can be, and have been, made incrementally as time passes while profitable volume production of earlier designs continues.

In aviation applications we basically must have a fully mature product right off the bat, with no opportunity to finance the R&D needed for that maturity out of ongoing production. Factor in the great bugaboo of aviation, limited sales volume, and it is no wonder things have progressed so slowly.

But slow or not, we are progressing. Notwithstanding the wishful thinking of the proponents of electric, hydrogen, and other alternatives, hydrocarbon burning piston engines will continue to propel smaller aircraft for the foreseeable future, and my bet is on diesels.

Posted by: John Wilson | May 3, 2013 11:22 AM    Report this comment

"...Now that the avgas chickens are coming home to roost, I'm expecting more people to start asking questions..." Maybe the avgas chickens are coming home roost, but it's up to us to see that they don't land anytime soon. The equity of the GA fleet is inextricably linked to the availability of avgas. There is no fix, not relaxation of medical standards, not better student retention, nor anything else I can think of, that will make up for the shellacking GA will take if avgas goes away in the next few years. Don't get me wrong: I've owned [marine] diesels and they are great, and I'd love to have a diesel Skylane. But I suspect that few of the tens of thousands of us who have invested in GA aircraft of some vintage will have the wherewithal to convert our powerplants, and there is no body of buyers waiting to take these birds off our hands -- even as cheap as they will be. We should be channeling some of our activism into making the case for 100LL, whenever and wherever it needs to be made.

Posted by: Jerry Fraser | May 3, 2013 12:10 PM    Report this comment

Still waiting for a viable 100 octane unleaded replacement fuel. That would fix the major problem, as long as it's not horrifically expensive. (not holding my breath for that)

Posted by: Will Alibrandi | May 3, 2013 12:38 PM    Report this comment

I'm expecting that when the engine in my Archer II is due for a major overhaul, it'll be replaced with a diesel. Granted, the total time is in the low hundreds so I have some time to wait, but that's what I foresee. Fortunately, it'll also run on 92UL (or whatever they're calling it), so even the 100LL uncertainty shouldn't be an issue for me. As for the existing aircraft out there much closer to TBO, for all the talk about the imminent demise of 100LL, I suspect those will still be replaced with another 100LL burner.

I believe we'll see the market for diesel/Jet-A piston engines take off (pun not intended) well before any viable electric solution. Until I can fly my plane with its current payload capacity 4 hours between stops and recharge within 10% of the time it takes to refill 38 gallons (my current fuel capacity, minus the 1 hour reserve), electric just won't cut it. There's also the matter of diminished battery capacity over time that will need to be addressed; running out of power in a car is merely an embarrassing inconvenience, but unacceptable in aviation.

Posted by: Gary Baluha | May 3, 2013 2:12 PM    Report this comment

@Gary Bakuha - That's my opinion of the diesel vs electric market potential. Add to that, the very best batteries commercially available aren't even at 200 W-hr/kg yet. Even if they were, assuming you're talking about an IO-360 (200hp) plane, to produce a 65% cruise level of power for those 4 hours would take more tha 2 tons (4,273lbs) of batteries. Even at the 400 W-hr/kg some labs have achieved that's still over 2000lbs in batteries. That plane would never even leave the ground.

Anyway, I keep hoping to see Deltahawk get certified. As an engineer I like their design philosophy. And I have an idea for a long-range plane that will really only work well with diesels. Fuel consumption is way to high with a turbine, and while my idea could work with 100LL, it's less attractive to me for a number of reasons. The 400hp Deltahawk that is supposedly planned for their next project would be perfect if it turns out to be anything close to what they claim.

Posted by: Andrew Upson | May 3, 2013 2:47 PM    Report this comment

"I'm expecting that when the engine in my Archer II is due for a major overhaul, it'll be replaced with a diesel."

And what might you be willing to pay for such a thing?

Posted by: Paul Bertorelli | May 3, 2013 3:09 PM    Report this comment

Paul, Hopefully by then, no more than I'd pay for a new O-360 (not including any changes required to the fuel system) ;-)

But as I say, I have many years to go before I get to that point.

Posted by: Gary Baluha | May 3, 2013 3:15 PM    Report this comment

I suspect when the time comes you won't like the diesel numbers much. An O-360 overhaul will remain competitive for quite some time against a new diesel conversion, which is likely to be in the low $40,000s to over $50,000. Unless you're flying a lot of hours a year--maybe 200--the economics don't pencil out that well.

Jerry Fraser touched on the economics above. Worldwide, there are in the range of 250,000 GA piston aircraft, of which under 2000 are diesels. At current rates, five years from now, we might add another 1000, but probably less. So unless someone repeats the loss leader mistake Thielert made, the volume won't be high enough to bring prices down much.

The legacy fleet will remain a gasoline fleet for a long time. Currently, it will take 50 years or more to replace it. In new airplanes, the percent that are diesel will rise steadily. Let's generously say Cessna sells 125 diesels a year, Cirrus 150, Diamond another 100. That's 1800 or so for the period. During that time, worldwide production would be between 4500 and 6000 piston airframes.

So using reasonable assumptions, despite what the diesel and electric acolytes say, this paradigm shift is and will be plodding.

Maybe China will save us.

Posted by: Paul Bertorelli | May 3, 2013 3:56 PM    Report this comment

When I purchased my 182 several years ago I already planned ahead for this. It can use mogas now and if needed I can retrofit a SMA diesel should ethanol free mogas goes away. Mogas offers the cost savings we need and is available now for 70-80% of the fleet. The longer it takes to find a 100LL replacement the better diesel looks to replace the high power density engines(100LL) especially with the uncertainty of the cost of the 100LL replacement fuel.

Posted by: SAMUEL SUTTLE | May 3, 2013 4:12 PM    Report this comment

Paul:

If aviation gasoline goes the way of the dinosaurs (a sudden apocalyptic event - like the EPA/FAA banning its use), the paradigm shift will take place in a matter of weeks. Suddenly, diesels will be immensely popular. I just have no faith at all that we're ever going to see a drop-in replacement for 100LL. I see that asteroid coming within the next 10 years...

Posted by: Thomas Yarsley | May 3, 2013 5:09 PM    Report this comment

A friend of mine brought up an interesting point. What about the "Air assisted direct injection" technology that Orbital Engines has been developing? Apparently Hirth is using it on some of their 2-cycle ultralight engines to allow the use of heavy fuels (diesel, various jet fuels, etc) in their spark ignition engines. Seems like there might be a possibility of modifying existing 100LL engines with this kind of system so they could burn either 100LL or Jet-A. I don't know enough about that system to say if it's truely a good idea, but it seems to bear looking into a bit more.

Note - I am not affiliated with nor an investor in any of the companies mentioned above. Just a geek that wants to find some solutions.

h t t p : //orbeng.com.au/flexdihf2013.html (take out the spaces from the beginning portion.

Posted by: Andrew Upson | May 3, 2013 5:33 PM    Report this comment

@Andrew I'm the test pilot a certain UAV helicopter made by a certain aviation company in Sweden, and we use the 55HP Jet-A burning Hirth injected engine you described. Been an interesting road as fly/help develop this powerplant with them...

Posted by: Anthony Longobardo | May 3, 2013 6:30 PM    Report this comment

Overall it's been a good performer. Rumor is a 3 cylinder is in development which we're pretty excited about. They're nice and small engines, and if you look online, their US distributor has a 100hp non-diesel available.

Posted by: Anthony Longobardo | May 3, 2013 6:45 PM    Report this comment

It seems to me that for diesel to become prevalent in (say) 10 to 15 years, aside from the fear factor, the positive way is via a pull factor: the price of installing a new diesel motor being around the cost of an overhaul. That has to be possible, given the size of the fleet. Producing those engines would be mass production, not cottage industry production. Maybe a diesel must be heavier but I bet that weight delta can be within the range of the weight saved due to lower consumption.

There is a lot of loyalty that builds up from getting home safely all those times behind Lycomings and Continentals. Ly/Con have plenty of enthusiastic people but quite simply, via the priorities of their parent companies they've been no friends to aviation WRT adapting to emerging realities. They were cashing in when they should have been pushing the hardest. They've had a hard row to hoe recently but what is more important - loyalty to them or a viable GA fleet? I believe that hard, unpleasant realities require unpleasant, impolite questions.

Paul, you're just about the most dependable aviation journalist but I urge you to annoy these people more. Ask them harder questions. Put them on the spot. Some of them should scared (or more scared?) to see you coming!

Posted by: john hogan | May 3, 2013 9:44 PM    Report this comment

Anybody know what happened to the Gemini 100 diesel engine from PPD?

Posted by: John Bond | May 3, 2013 10:59 PM    Report this comment

Mr. Varley, I don't mean to sound impertinent, but I take issue with your statement about electrics. I'm not a fan currently, no pun intended, but batteries have taken remarkable leaps in the last 10 years alone. There are plenty of discoveries as well, such as carbon technology that was being researched to make printing graphene cheaper. The "super super capacitor" video on wimp.com if you'd like a look. I don't think it will happen for quite a bit yet, but it is important to note the charge time, seconds for minutes. On an item that was being developed for something else entirely. Flexible batteries that are ultra-lightweight wont happen tomorrow, but tell someone in the 1980's using a Motorola brick that in a couple of decades that people will be using phones with large color displays that can access Arpanet, for hours without plugging in. Like I said before, not tomorrow. Then again who knows when a Eureka! moment will happen.

Personally, I want an easing of STC regulation to allow a swap of avgas engine to diesel engine of the same horsepower. I wouldn't count on that, too many variables to control for in the equation. Don't take me too seriously though, I advocate nuclear power and fusion research too, which too many NIMBY's fear or consider a waste.

Posted by: Joseph Servov | May 3, 2013 11:07 PM    Report this comment

John, one can only surmise so much from asking companies hard questions. The real proof of the pudding is in user surveys, which we also do. But that takes a couple of years of field experience to assess.

In 2005, I spent a day at Thielert's factory in Lichtenstein where I asked them to whiteboard the economics of that engine. It didn't quite add up. I eventually concluded they were loss leadering, hoping to turn the corner with higher volumes, longer TBOs and fewer inspections.

But whatever the assumptions were, the curves came together and we discovered this with owner interviews in late 2007. Four months later, Thielert was bankrupt. Some companies just make unrealistic assumptions about the inputs. Some just obfuscate the numbers and without a glimpse inside the books, we can only offer informed opinions.

Customer experience is the great field leveler. See Jared Testa's comments above. I'll be following up.

Posted by: Paul Bertorelli | May 4, 2013 6:48 AM    Report this comment

As for the economics being slam dunk because of automotive manufacturing volume, I am skeptical of this claim. You have to make a lot of engines and airframes to get meaningful economy of scale.

Take SMA, for instances. Nice engine. Light, simple and reliable, but very few in the field. What, in your wildest imagination, will be the uptake? In new airplanes, for the next five years, maybe 300 to 400 a year. And that's probably pie in the sky optimistic. Very little scale at that number. An automotive engine plant makes that many in a couple of hours.

That's not to say diesel won't be adopted and in volume. It will. It's just not going to happen rapidly because of gasoline engine interia. And if someone comes out with a sweetheart price offering a diesel conversion for the price of a gasoline overhaul, keep your hand your wallet. That could be Thielert all over again.

Still, people will fall for it. And we'll be writing the same story all over again.

Posted by: Paul Bertorelli | May 4, 2013 6:59 AM    Report this comment

The answer to our diesel desires is at www.EPS.aero. that is a group called Engineered Propulsion Systems (EPS), they are developing a new 350 hp aircraft diesel. Their engine that is now running on the test stand is a weight, size, and shape fit to interchange with existing Lycoming 540 or Continental 550 engines in all single and twin applications. EPS has been fairly quiet about their efforts as they are the kind of engineers that want to make sure the design works before bragging about it The one interesting fact about EPS is that if you want to see it running you can go to New Richmond Wisconsin and watch it operate at full power. this is different from the other 300 hp diesel engine developers. I have not been able to go visit any of the other players building an engine in this category. Call EPS, find a date that fits their test schedule and they will be happy to have you visit.

Posted by: william Lawson | May 6, 2013 8:45 AM    Report this comment

Using Continental's and EPS'spublished weights, the EPS engine would be a bit over 200 lbs heavier than my IO520. That kind of weight difference on the nose is not going to work no matter how fuel efficient it is.

Posted by: Richard Montague | May 6, 2013 11:03 AM    Report this comment

You really need to compare installed weight not data sheet weights. However unfortunately lyc. and Cont. never publish those weights.

for comparison the TIO540 in my Aerostar with all the stuff necessary to fly weighs 650 lbs without the prop if you unbolt the engine,and weigh the engine assembly with mounts, intercooler, ducting, normal accessories. etc

The EPS 350 hp engine with all the stuff it needs and fluids radiator, etc. to fly weighs 670 lbs ready to fly.

A 300 hp IO540 from our studies installed weighs about 70 lbs less than the EPS 350.

fuel usage is where you make up the difference. at 75% of 350 hp (LYC tio540 comparison) the EPS 350 uses 53 lbs per hour less with the 100LL engine rich and with the TIO 540 lean uses 38 lbs/hr less. thus taking off with less than 2 hours of fuel, The EPS 350 is about the same and the longer you fly the better it gets.

FYI the Theilert 4.0 300 hp diesel V8 when they certified it in a 206 weighed about 250+ lbs more than the engine assembly they took out.

Posted by: william Lawson | May 6, 2013 12:10 PM    Report this comment

Bill Lawson is absolutely correct. In addition, take a look at Hartzell's press release on their new ASC-II Bantam Prop, it is quite a bit lighter than a standard metal prop and has already been tested satisfactorily on the EPS engine. For my Aerostar, an EPS 350/Bantam combo is a wash weight-wise...but the speed/fuel burn (aka CAFE parameter)...my oh my.

Posted by: Norman Howell | May 8, 2013 6:21 PM    Report this comment

Bill also notes correctly the weight delta between a normally aspirated gasoline engine (installed) and the EPS 350 as about 70 pounds. I would think any Bonanza conversion from an NA IO-520 to a TAT Turbo or Machen added 30 or 40 pounds or more as well.

Now, think about running your EPS powered Bo on red diesel (plus Prist of course) from the local co-op. :-)

Posted by: Norman Howell | May 8, 2013 6:37 PM    Report this comment

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