Wanted: Aerodiesel from Honda

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Carl Spaatz and Ira Eakin—the two legendary leaders of U.S. air power in World War II--just got it all wrong when they decided to bomb the German ball bearing factories at Schweinfurt in 1943. What they should have been bombing is the factories that make those little skinny spring washers that the Germans can’t seem to build so much as a toy wagon without using by the gross. The war would have ended a year earlier.

I was reminded of this today when my correspondent Stan Fetter wrote this note about his experiences in repairing a Thielert diesel’s all-critical clutch: “There are a bunch of spacers in there, and if any of that stuff comes apart the whole thing has to go back to the factory...Had a new one on the bench and the tool guy picked it up and moved it, and stuff went everywhere.”

Been there…and the t-shirt is now a shop rag. I have a couple of motorcycles, a BMW and a Honda. To service the fuel pump and filter on the BMW, you need a pair of hemostats—no kidding, that’s what the shop manual says—to squeeze off the fuel hoses while you worry the thing out the side of the fuel tank, being careful not to trash the $400 fuel gauge sender. And don’t forget the special clamps which you must replace. On the Honda, the same assembly drops out of the bottom of the tank in five minutes. Buy the clamps at NAPA.

This aside is central to the problems Thielert is having with its aerodiesel. The thing requires a lot of wrenching—replacement of the gearbox and clutch assemblies, fuel pumps, alternators and so on. And it’s not simple wrenching, thanks to the German penchant for using two spacers where one will do, a spring hidden in an invisible blind hole that rockets across the shop and careens off the bench grinder and disappears before you even knew it was there. And great clouds of those damn flat washers which are always left over after you’ve reassembled the part without the missing spring because they’re out of stock and the parts guy says they leave them out, too.

Which brings me to this: What’s needed here is for Honda to stop screwing around with four-cylinder gasoline engines and to get busy with aerodiesel. For reasons related to culture, economics and predisposition, the Japanese haven’t been big on diesel engines for cars. In fact, Honda is expected to launch its first next year. By dint of long experience—the Germans own the diesel car market—the Germans have diesel pretty well figured out. It will be daunting for others to catch up. But to a degree, the Germans are victims of their own success when it comes to building things that are easily maintainable. They tend toward in-the-box thinking with regard to repairing things. The Japanese have proven to be better at this, at least in cars and motorcycles. It would be intriguing to see their version of a practical aerodiesel.

Comments (57)

Yep. We need Honda to develop a simple, economical diesel engine for aircraft, with low cost for aircraft owners (a Theirlet costs what, 62K, for an install? That ain't low cost!). The price has to be low enough so that aircraft owners will be able to replace the avgas engine economically.

And DON'T go with full FADEC!. I don't mind partial control over the engine with computer, but leave a backup system that isn't dependent on computers.

Wouldn't hurt if they did some developing of some gasoline engines for aircraft...maybe one that run better with automotive gasoline...I'd be afraid to run an aircraft these days, what with ethanol and such added to the gasoline.

Posted by: George Rambo | May 9, 2008 9:38 AM    Report this comment

And while they're at it, why not develop an electric aero engine powered by a small gasoline aux generator in the baggage locker? Honda already makes the latter.

Posted by: nicholas budd | May 9, 2008 11:06 AM    Report this comment

hehe, you're right paul, we operated a c-172 with a 1.7 thielert (failed in flight) then a 2.0 and the bloody clutch came apart(literally) 3 times in 100 hrs. diesels are here to stay, we just got to work the last few bugs out, and the japs are probably the peeps to do it!

Posted by: JOHN GREIF | May 10, 2008 11:35 AM    Report this comment

Might I suggest the French (particularly PSA) who have a long tradition of cheap, lightweight and very durable diesels; or Volvo Penta which has a long tradition in aero engines, and good experience with diesel on both the marine and automotive side?

Posted by: Bram Smits | May 13, 2008 5:50 AM    Report this comment

the problem with honda using gasoline motors in airplanes is that their motors are much more powerful at higher rpm settings, not to say that honda couldnt create a great aviation motor. i am a Honda automobile employee and truly believe in Honda's product and innovation. i have been employed at honda dealerships for 10 years now. they have grown in leaps and bounds. i think Honda and Ge really need to concentrate on the possibility of a hybrid type engine. use gas (but a lot less of it)and electricity, very similar to a civic hybrid.

Posted by: MICHAEL SULLIVAN | May 13, 2008 11:43 AM    Report this comment

I can't see how a hybrid makes sense. The advantage of a hybrid in a car comes from the ability to shut off the engine while idling and battery charging during braking. The disadvantage is weight, which matters far more to an aircraft than a car. Maybe leave out the extra batteries and use solar panels to provide some of the energy in flight? But would this really overcome the efficiency and weight penalties of a gas engine/electric motor system in anything larger than a motorglider?

Posted by: Alex Frakt | May 13, 2008 2:14 PM    Report this comment

Hybrids are primarily aimed at levelling the "peaks and valleys" of driving. Aviation does not have the same type of demand curve - typically short high load climb, extended part load cruise and short low load descent. The battery would only benefit from the descent phase where we need to dissipate excess energy. Self discharge of the battery would limit the amount of energy that could be "recycled" in the climb phase of the next flight.

I consider that the internal combustion engine is firmly entrenched, but needs to reap the benefits of improved technology, whether diesel or petrol. Turbine engines, with improved materials may offer the best long term solution because they can burn just about any liquid fuel and do not waste energy on reciprocation.

Posted by: simon lewinson | May 13, 2008 6:43 PM    Report this comment

alex is correct. K I S S

Posted by: JOHN GREIF | May 13, 2008 6:51 PM    Report this comment

Dear Paul, beeing German but owning a Vespa-Scooter for more than 25 years (and maintaining it) I know exactly what you are talking about and you are right. KISS is a very important principle when it comes down to cost at maintenance and operation, too. You were stressing on Honda to build a good aerodiesel, well they are doing well, but you have to be on the cutting edge when it comes to weight/power relation in small four-seat single-engine aircraft. Learning from the Thielert desaster,Diamond Aircraft Industries, Thielert's biggest customer, has gone a different way. They engaged in a joint-venture and founded Austro Engine, a joint-ventute between MB-Tech (MB for Mercedes Benz), BOSCH and Diamond Aircraft. They have a similar aerodiesel engine ready and Diamond is famous for easy maintenence. Try to Google on Diamond and Austro Engine. The new engine will be 20% more powerful with a little increase in weight. Finetuning small and fast running diesel engines is a delicate thing. Sometimes it needs just a small spring more to achieve what you desire ;-) but you are all right at the end. KISS is paramount, we are operators and we are out there, far from the shops and factories. So long, Thomas.

Posted by: Thomas Neuland | May 14, 2008 5:02 AM    Report this comment

With approximately 1.5million kilometers on my fleet of Honda cars over the years I can say that I, too, am hopeful that Honda will move into aerodiesel development. While hopeful, I have to look at history to keep those hopes in check. What happened to the Honda/Continental collaboration that was supposed to produce the next generation of gasoline aero engines? I saw this effort announced in 2003 and haven't seen much of it since, certainly not a production engine.

And my experiences with Honda engine diagnostics has been positively chilling. When you look at Honda shop manuals they are predicated on a part (like a temp sensor) either working, or not working. They have absolutely no "gray area" troubleshooting assistance. In the aviation world, this approach to dealing with any kind of electronic engine control simply won't fly. If Honda is unwilling to provide detailed troubleshooting information to the automotive mass market, there's no hope of them providing it to the miniscule aviation market.

I'm hoping to see a truly viable 100hp aerodiesel in the near future, and there are a couple that are darned close. Unfortunately, Honda's name isn't on any of them, and they're all far more expensive than they should be. Heck, even the 80hp Smart car engine conversion runs close to $20K - this makes Jabiru and similar gasoline engines look pretty cheap.

Posted by: Mark Briggs | May 14, 2008 6:44 AM    Report this comment

The Gemini 100 hp diesel is now in flight testing with the Indus LSA The company producing it is Jadeair in England which does a certified gas engine and several experimental gas engines which are pretty good (no- I dont work with or have any financial interest in the Co or its products.) Turbines aren't the answer for small aircraft. Their light weight is offset by higher fuel burn and they aren't efficient at low altitudes where most GA takes place. Diesel is the best hope for relatively economic operating costs.

Posted by: DAVID WILDER | May 14, 2008 8:23 AM    Report this comment

I don't care if it's Honda, Toyota, MB, Volvo, GM, Ford, etc - any or all would be fine with me. Their resources and experience would be great. I agree that KISS and use of COTS components where possible would be preferred.

At the moment, I think the Gemini twin-crank (a la Junkers) shows a lot of promise. I am looking forward to seeing them at EAA this year.

As for the cooling challenge of a diesel, perhaps a deeper integration of the engine and airframe teams could help resolve those challenges. Rather than figuring how to mount and duct the radiator, perhaps the answer is a heat exchanger which could serve double duty as a part of the semi-monocoque skin of the aircraft. . . .

Thanks for the blog entry and continuing to push these issues and ideas.

Posted by: Jim Hausch | May 14, 2008 8:32 AM    Report this comment

Well I have had 3 BMW cars and do 100% of the maintenance. You will not find an easier vehicle to work on. The TAE was based on a Mercedes. Honda is good, but it will take many years for them to catch up. Thielert needs oversight from a real deal company like BMW or Honda to fine tune and mass produce what they got already....and what they got are STCs, FAA, and JAR approvals....the most valuable pieces of paper in the industry.

Posted by: Joe Demers | May 14, 2008 11:10 AM    Report this comment

I agree that diesel engines have a place in aviation, and that the ready worldwide availability of Jet-A - and the inertia behind the idea at this point - is what drives their popularity. But what's wrong with four-cylinder gasoline engines, as long as they will run on blended auto gas? Speaking of simplicity, diesel engines are inherently more complicated because of the required turbocharger and liquid cooling. They are also inherently heavier due to these added parts, as well as because of structural concerns related to their high internal pressures. They do have some advantages for aviation, but are not ideal for inexpensive, low power, low altitude aviation applications IMHO. Hard to beat an air cooled gasoline engine for that.

We may at some point see turbine engines for light aircraft, if materials technology advances to the point where their inherent efficiency can be substantially increased. The main limiting factor to turbine efficiency is the heat tolerance of the high pressure turbine. Major improvements, however, are some ways off at this point, even in the best case scenario. And the comments about the poor low altitude efficiency of turbines are correct; small, low altitude turbine engines will always be less efficient than large, high altitude ones.

Posted by: Ryan Biggs | May 14, 2008 11:44 AM    Report this comment

yo ryan, this isn't a hypothetical. aerodiesels have proved themselves. the 1.7 and 2.0 thielerts that we operated commercially for over a thousand hours, payed for the conversions from lycoming and saved us money due to the avgas/jet a price delta.lets not reinvent the wheel here. we just need to work out the last few bugs in the system.

Posted by: JOHN GREIF | May 14, 2008 11:54 AM    Report this comment

AVWEB,PLEASE HELP!

Please investigate and give us AVWEB readers an in depth report on why the Zoche Aerodiesel is not yet available for sale.

Hands down the best aerodiesel engine yet developed for General Aviation is already here! The Zoche Aerodiesel. There is internet speculation that this engine is so good that someone has bought out or is paying Zoche off, thus keeping this engine from reaching the market.

Please get to the bottom of this!

This engine can revolutionize not only GA, but the kit aircraft/homebuilding if brought to market!

http://www.zoche.de/

Posted by: eric stocke | May 14, 2008 4:00 PM    Report this comment

Checkout deltahawkengines.com, they seem to have the simplest aerodeisel I have seen. My mechanic friends look at theirs and say "that's what I want to service". No electronics at all, just simple mechanicla assemblies.

Posted by: fred gruner | May 14, 2008 4:15 PM    Report this comment

My understanding is that Zosche is now in the US working for the new owners of his Diesel stuff. Perhaps Paul can update us on that. DeltaHawk isn't ready yet. I hope its not a financing issue as their engine shows great promise.I'm betting on Gemini as its not a startup and th other engines these folks make are good value for money.

Posted by: DAVID WILDER | May 14, 2008 4:20 PM    Report this comment

Honda has designed an excellent automotive diesel engine that has been sold in Europe for several years installed in Accords and CRV's. The have stated they will introduce this engine and another larger one into the US next year and meet the 50 state clean air standards. This development could be the basis for an aerodiesel engine if they decided to go in that direction.

http://www.autoblog.com/2008/01/14/detroit-2008-honda-gives-us-a-peek-at-the-i-dtec-clean-diesel/

Posted by: Rip Sessions | May 14, 2008 4:56 PM    Report this comment

Yeah I hear you on the diesel vs. avgas delta John (although now Jet-A is more expensive - yes I know that diesels have lower fuel burns though), and know that this is why diesels are gaining popularity. I'm also impressed that 1000 hours was enough to pay for the conversion, although it sounds as though it wasn't exactly a smooth transition. I'm just saying that a simple but newer technology gasoline engine that will run on common pump gas wouldn't be reinventing the wheel either, and would have some distinct advantages in the US market. So why dismiss that possibility?

Posted by: Ryan Biggs | May 15, 2008 11:41 AM    Report this comment

How sad that an American designed and made engine didn't even begin to enter the mind of this writer, or any of the commenters.

Signed: An american mechanical engineer who knows the Japanese and the Germans aren't any better than American engineers. Its the bean counters who have screwed us. "Would you like fries with your burger ?"

Posted by: Kerry Stevens | May 15, 2008 11:46 AM    Report this comment

ur right ryan, in the u s, thats the way to go. but any where there's a significant diff in jet fuel price or availability, we NEED the diesels. we operate a fleet of caravans and australian airvans.

Posted by: JOHN GREIF | May 15, 2008 11:59 AM    Report this comment

yo kerry, i agree bro, the americans taught the world to fly and still dominate in aviation. but the proof is in the pudding. too many innovations are coming from japan, but don't blame the bean counters, lay the blame at the feet of the ridiculously litigious populas, and the liberal judges!

Posted by: JOHN GREIF | May 15, 2008 12:02 PM    Report this comment

Its not really the bena counters. In Europe the price of gas has been insane for years, and the European govts in order to reduce the imported oil dependency have given tax breaks for diesels for years and have mandated clean diesel. The result is lots of efficient diesels in use. The contrast with the US shows a lack of foresight amongst the lawmakers-but what else is new.

Posted by: DAVID WILDER | May 15, 2008 12:24 PM    Report this comment

I agree John, but don't forget the the unions are screwing American industry just as bad. When layoffs come, the junior most people go first...regardless of performance, education, capability, etc. In addition, in a union workshop, many jobs are unecessary and/or redundant, thus driving the cost of labor through the roof. Unions should be outlawed with the exception of police and fire.

Posted by: Joe Demers | May 15, 2008 12:26 PM    Report this comment

Sure, it is vital to lower operating costs. But diesel engines and Jet-A are not the right way to go... too complex a technology, the KISS principle has indeed been forgotten by many. The diesels (at least 4-cycle ones, the jury is still out on 2-cycle models) have maintenance and overhaul/replacement costs that cancel nearly all the fuel cost advantage they may have. They also have significant and inherent reliability issues (i.e. no bugs or teething problems). Why not consider mogas? There is actually nothing against using mogas in aviation PROVIDED the engine as well as the fuel system are designed for it. Gasoline engines may burn 20-25% more gallons than diesel engines (the real delta is arguably significantly less), but mogas is ~30% cheaper than Jet-A and available everywhere. Not on YOUR airport? It's a question of insufficient demand. Ask our German and Austrian friends who, more often than not, have mogas available on their base airfield (including at Wiener Neustadt, Diamond Aircraft's home).

Posted by: FRANCOIS BADOUX | May 15, 2008 12:29 PM    Report this comment

My understanding is that Mogas has lower standards for water and hence a higher risk of iced fuel lines. This can be overcome by adding stuff to the fuel-but at the GA fuelling level that s not a guaranteed fix.Jet A is cheaper than gas here.

Posted by: DAVID WILDER | May 15, 2008 12:34 PM    Report this comment

francois, your comment "But diesel engines and Jet-A are not the right way to go... too complex a technology" dosen't hold water. the 2.0 thielert that we operated had 1/3 fewer parts thah the lycoming it replaced.

Posted by: JOHN GREIF | May 15, 2008 12:37 PM    Report this comment

Water is indeed slightly miscible with gasoline, MUCH MORE SO with Jet-A. So Jet-A Is not the answer to that preoccupation. Water in gasoline is NOT an issue related to the product spec but to the care and control at the retail distribution point. I have had problems once with water mixed in avgas at a sloppy FBO.

Posted by: FRANCOIS BADOUX | May 15, 2008 12:40 PM    Report this comment

joe, as much i as dislike unions, they are desirable to some degree,BUT the tail is currently wagging the dog in the u s. on the unionized labour continuum we are def to close to the wrong end.is saturn car company still non-union? just shows if you treat your peeps right it isn't necessary.

Posted by: JOHN GREIF | May 15, 2008 12:42 PM    Report this comment

John, first, the future standard on part count should not be Lycoming... Second, the complexity, fragility and absence of redundancy lie in the high-pressure direct fuel injection system. The other major weaknesses are 1. internal stresses are through the roof in aviation turbo-diesels and 2. torque fluctuations break dampers (aka clutches) and transmissions in no time at all (confirmed in these very pages)

Posted by: FRANCOIS BADOUX | May 15, 2008 12:46 PM    Report this comment

I agree with Paul. The German culture of engineering and manufacturing gives us great end products, but I think many times manufacturability and ease of maintaining those products once they’re in the field leaves a lot to be desired. I know I’m Monday morning quarterbacking here, we all are, but I’m not as much of a fan of the Thielert line of aero diesels as I used to be. It sounded good at the beginning when Thielert was leveraging the advantage of all those mass produced Mercedes engines. But as it turned out, that stock engine had to just about be completely torn down and rebuilt, with very few stock parts left in the engine; so most of the leveraging advantage was lost. With the end result being yet another low volume, essentially hand built engine that was never really designed for the mission it was now being asked to do.

TCM claims that they will certify a heavy fuel engine in 2009. It will be interesting to see if it’s based on the GAP engine. I understand when that engine goes from four cylinders to six cylinders, the weight issues become much easier to deal with.

Posted by: JOHN MININGER | May 15, 2008 12:53 PM    Report this comment

francois, yeah but i have to deal with the now, not a hypothetical. btw it was our aircraft that had the clutch problems, AND an in flight failure (due to cylinder head) and from that informed perspective i still favor diesels.

Posted by: JOHN GREIF | May 15, 2008 12:54 PM    Report this comment

John, the cylinder head failure is a consequence of the #1 problem I mentioned above: unacceptably high mechanical and thermal stresses to compensate with turbo boost for the diesel's inherently low power density. A French aero-club close from where I live had within 18 months 3 in-flight failures on their... 3 Thielert-powered aircraft. One due to cylinder head and two to fuel pump failures. Bad karma...

A engine running on 100LL as well as on mogas, blended or not, much simpler, much more reliable, durable, lighter, cheaper to operate is not an hypothesis, it is presently undergoing FAA certification... not next year, now.

Posted by: FRANCOIS BADOUX | May 15, 2008 3:53 PM    Report this comment

esta bien francois. vamos a ver!

Posted by: JOHN GREIF | May 15, 2008 7:12 PM    Report this comment

I don't think piston diesels are the answer. Piston engines by their nature require parts, parts and more parts. Which means, more labor time and parts inventory issues which means $$$. What we need is a turbine like Innodyn is working on. I haven't heard much from them lately but they seem to have a working product that just needs to be refined. Skip Honda & the car manufactureres. GE, P&W, or Williams should be looking to build these small turbines. I think a PT6 has a 3000+ hour TBO. Just the longer TBO times would make a turbine much more cost effective than piston diesels.

Posted by: george valent | May 15, 2008 8:46 PM    Report this comment

talk about $$$$$, now turbines = money!!! the tolerances, the precision, the expensive heat tolerant materials, the low volume production!!!! i spent 2 years on a p&wc advisory board. one of the ideas developed was a "common core turbine", one core for turbo fan, turbo shaft, and turbo prop, they were a whole order of magnitude off on price that would allow them to mass produce.

Posted by: JOHN GREIF | May 15, 2008 9:22 PM    Report this comment

The cost of oil based fuels is going up-a high consumption engine is not the answer.The operating costs would be very high for GA aircraft because the turbines aren't efficient at low altitudes. Diesel is the least worst solution.

Posted by: DAVID WILDER | May 15, 2008 10:36 PM    Report this comment

right you are ken....errr dave

Posted by: JOHN GREIF | May 15, 2008 11:00 PM    Report this comment

George Rambo wrote: "We need . . . to develop a simple, economical . . . engine for aircraft, with low cost for aircraft owners" Right!

And george valent is right when he wrote: "Piston engines by their nature require parts, parts and more parts. Which means, more labor time and parts inventory issues which means $$$"

For engines up to 1,000 horsepower, the solution is to--throw away the piston!

And the camshafts, the shims, the buckets, the valves, the crankshafts, the connecting rods and all the other fragile, high-maintenance, designed for failure parts and replace it with:

a turbocompounded Wankel rotary engine.

The fuel consumption and sealing problems of the rotary were solved YEARS ago. The Wankel rotary engine is now smooth, reliable, powerful, reliable, frugal, reliable, already tested, reliable, small, reliable, only three moving parts--oh, and did I mention, they are reliable?

Current, non-turbocompounded rotaries have BSFC's comparable to Lycoming and Continental. A turbocompounded rotary would yield far more power and efficiency than a piston engine, either spark- or compression-ignition, could ever achieve.

Mr. Bertorelli, what you actually want is an inexpensive, light, reliable, economical, easy-to-repair engine. Look to the rotary, sir, not the piston.

For details, look at http://www.rotaryeng.net/turbo-compound.html

Posted by: Les Nordman | May 16, 2008 10:11 PM    Report this comment

While rotary and turbine engines appear attractive, they are both expensive to manufacture, operate and maintain. The typical turbine engine cost at LEAST $100/hr for maintenance cost (and that is for high use engines, low use is far more expensive) and their specific fuel consumption is MUCH higher that any diesel or piston aero engines.

It is important to note that Honda has produced extremely reliable engines for their racing efforts. No cars have retired from championship races in the past two years due to engine failures, a first in that class of racing (and all engines are Honda). The same designer of Honda racing engines created their new clean diesel engine by special request from the company. If they decide to apply their same technology and efforts to a aero-diesel engine (and we should all hope they do) there can be no doubt they will succeed in producing a reliable product. They are the number one internal combustion engine manufacturer in the world and have a stellar record of success.

Posted by: Rip Sessions | May 16, 2008 10:47 PM    Report this comment

According to this evening's NY Times, Honda, VW Audi and Subaru will all be introducing Diesels into the US. over the next year or so. the smaller ones won't have urea tanks for emissions controls and will be legal in all 50 states the aviation implications are obvious. Magnetos and spark plugs will soon be artifacts

Posted by: DAVID WILDER | May 17, 2008 1:15 AM    Report this comment

hey, check this out "Lycoming announcing a diesel engine, after Continental announced that it is finally developing with Honda Motors a 350 HP engine, is therefore major news." unfortunately its from an article dated 2005.http://dieselair.com/2005/04/lycoming-shows-one-eye-jacks-possible.html

Posted by: JOHN GREIF | May 17, 2008 10:25 AM    Report this comment

yo francois, just read up on your engine. how does the fuel consumption compare to the continental io-520 or the lycoming io-540, both burn about 14gph in a cessna 207/207 produing about 115 knots at 3000ft density altitude. what would your numbers be? and how does your installed weight and purchase price compare?

Posted by: JOHN GREIF | May 18, 2008 12:39 PM    Report this comment

Francois- What is the name of the manufacturer of this paragon of engines you mentioned. Is it perchance Superior? Is ther a website I can go to to see something about its characteristics-weight, HP, etc.

Posted by: DAVID WILDER | May 18, 2008 1:05 PM    Report this comment

http://www.mistral-engines.com/

Posted by: JOHN GREIF | May 18, 2008 1:09 PM    Report this comment

Hi, John.I have to check on my C-206 handbook what power setting will yield 115knots at 3000 feet with the Mistral G-300. Initial guesstimate is 13.0 gph of regular MOGAS. If you can feed it that fuel, you'll save an additional $1.20-1.50 per gallon over avgas, for a saving of $20-30/hr. The IO-540 installation, ready to fly, will be ~50lb heavier than the Mistral G-300's. Purchase cost will be approximately the same as a new IO-540, but maintenance and provisions toward overhaul will amount to a fraction.

Posted by: FRANCOIS BADOUX | May 18, 2008 3:01 PM    Report this comment

thanks francois,please keep me posted on your progres, and best of luck to you. my email Jgreif@tropicair.com www.tropicair.com

Posted by: JOHN GREIF | May 18, 2008 3:29 PM    Report this comment

I believe in aerodiesels, tightly controlled by a box full of electronics. KISS is well and good, but to a point. After all, we use cars and don't ride horses anymore, don't we. The development of efficient, reliable car-engines has worked, it can work on aero-engines as well. The problems I see, are not technology related, but money and certification related. The reasons mentioned above (high combustion pressure breaking cylinder heads, torque transients breaking clutches, high pressure fuel pumps, etc.) have all been solved in car engines for a while. For instance, modern diesels use up to five injections per ignition phase - Thielert uses only one. The first two "pilot injections" help to achieve a smooth pressure gradient in the combustion chamber before the "main injection" provides the energy. The two "post injections" are primarily for exhaust gas treatment and would not be required on aerodiesels. With this, there won't be torque transients destroying clutches and propeller blade bearings or cracking cylinder heads. For the high pressure fuel pumps, BOSCH has made new models, capable of even higher fuel pressures (the one used in the Thielert engine is 2 generations behind). But development costs a lot of money. to be continued ....

Posted by: Guenter Mannsberger | May 19, 2008 8:41 AM    Report this comment

...continued Then certification. Someone mentioned COTS (=commercial of the shelf). The EASA and FAA folks don't like COTS - they want to see service history of the parts in airborne applications, or you have to re-engineer the thing and have it developed and certificated to airborne standards - 5 million cars don't count. There goes another fortune into development. And then specifically in the US, the subject of liability and legal aspects add another fortune. So, I think many engineering teams in the world might have answers - but only a few might have the deep pockets to pull certification through. And then sell - what - a few hundred engines a year? If they are lucky. If you go to the bean counters with that proposition they want your head examined, I guess.

Posted by: Guenter Mannsberger | May 19, 2008 8:42 AM    Report this comment

The JAR folks in Europe did a white paper on light aircraft certification and pilot training for VFR. They came to the conclusion that aircraft certification for under 4400 lbs (2,00 kilos) was a waste of money. The crash statistics and expected mortality -both for people in the air and on the ground underneath were near as never mind identical. If you take a cutoff point-say 200 knot and say 3 passengers, "experimental " should rule. Tha implies that non-certified powerplants for light GA should be the rule-not the exception. Hope Diesels come sonn.

Posted by: DAVID WILDER | May 19, 2008 9:05 AM    Report this comment

Subaru have some beautiful four & six cylinder boxer diesels coming off the assembly lines now. reduction drives are allready avaliable so whats stopping evry one?

Posted by: Barry Davis | May 19, 2008 9:55 AM    Report this comment

My understanding is that subaru has been reluctant to cooperate in seeing their units used in GA because of the potential liability issues. Perhaps someone could get them to revisit that issue as the liability issues really aren't that great anymore. Barry-can you give me some coordinates on those Subaru diesels?

Posted by: DAVID WILDER | May 19, 2008 1:28 PM    Report this comment

I do not agree on a couple of things mentioned above: a). Working on 5 million cars does not mean a piece of technology will work well in an aviation application. Actually, the contrary is quite often true. Aviation applications DO need healthy doses of the KISS principle, from which modern automotive technologies are drifting away ever faster. b). My experience with the FAA type-certification procedure is that I am yet to hear something from them that does not make decent sense. They are quite pragmatic and competent.

Posted by: FRANCOIS BADOUX | May 19, 2008 3:06 PM    Report this comment

Does anyone happen to know if there's any spark of life in the Bombardier V-6 project?

Posted by: JOHN MININGER | May 20, 2008 8:14 AM    Report this comment

Nice discussion so far.

I have flown the Thielert installed in a DA-42 and found its operation simple and well suited to the aircraft. I loved the fuel flow at cruise. I am disappointed to learn of all the hidden maintenance issues which could result in the loss of A/C and crew.

Just wanted to point out that Deltahawk is approximately 1.5 years into their certification program. Their approach seems to have several advantages.. First - no gearbox. It would be great not to have another new, complex and heavy flying companion on each flight. Secondly, I recall that their total parts count is under 200. Fewer parts to build and maintain. Much of this is achieved because there are no removable heads! They do sell many engines into the UAV fleet and appear to be taking orders and even making deliveries to the experimental fleet.

To the flag wavers out there (that is a good thing) Deltahawk is based in Racine, WI (arguably within the US :') )( and production is in the US as well.. Go to their website to watch their progress

COTS will ultimately help aviation out. As the big component manufacturers get comfortable manufacturing 28,000 psi fuel components, we will benefit from their mass production volumes.

Aviation is both modern and ancient at the same time. It is good to see so much thought and energy going into getting us away from engines which were designed in the 30s.

As bad as things look today, I am optimistic that we will rise to the challenge.

Posted by: RAY DAMIJONAITIS | May 21, 2008 8:47 AM    Report this comment

hijacking again, darn it. Doesn't anyone read these things on the editorial side

Posted by: DAVID WILDER | November 27, 2010 12:46 AM    Report this comment

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