What is changed to make a diesel-engine work in an airplane?

[Frank N. O.]

I know a bit about passengercar and truck (roadtrain) diesel engines and after seeing that diesels are now proving to work great for GA planes like in passengercars (in Europe at least) then I'd like to know details on what is changed to make them work in planes. I read that the 1.7L Thielert is based on a Mercedes-Benz car-engine and that would probably be the one used in the 1-box A-Class since they have a 1.7 but that's a watercooled engine with electronic fuel-injection, does it still have this in the aviation version (not that I can imagine it would work without it)? And does the diesel have problems with ignition when it comes into thinner air or does the turbocharger eliminate that problem like turbonormalizing in a gasoline aviation engine? How much does a diesel engine with watercooling weigh vs a aircooled big displacement gasoline aviation engine? Even a small 4-cylinder Cessna engine is around 5.9L if I remember correctly (the designation number is the CID) and is it a problem that the dieselengines are inline and not boxers (horizontally opposed)? Now for a probably dumb question: Isn't it a great benefit that diesels don't use ignition systems both in terms of reliability and maintenance?

Frank

[Gulfstream Driver]

About the only thing I know about diesels is they don't have spark plugs.   

[Frank N. O.]

LOL, nope but they do have glow-plugs to heat up the diesel when it's starting cold, or at least my dad's 84 Ford Fiesta 1.6 Diesel did (and that was a new-generation engine back then, like the VW TDI engines were about 10 years later and of course also the common-rail system as well). My dad averaged 58 miles per US gallon fuel economy with 54 naturally aspirated hp pulling 1764lbs, The 14.1L 420hp intercooled V8 turbodiesel in the 22 wheeled 47.5 ton Scania R-142H 6x2 roadtrain he drove was a different story however, that was more like 5 mpg but then again, it could carry over 33 tons of cargo.

Frank

[fireflyr]

Germany used some two-stroke diesels  (Jumo diesels) in the 30s and 40s, they were quite complex in spite of not having a valve train

With fuel becoming so expensive, I believe Thielert is on the right track.   A diesel's power band would be well suited for aircraft work (low RPM and high torque) and the ability to more precisely meter fuel gives them better economy, just look at the performance versus fuel use of the Diamond Twin.

[Frank N. O.]

You know, BMW also makes some high-power diesels, like a 3L straight-6 24V DOHC with 230hp and 450Nm (in std. car-form with ultra-tight emission std's). VAG of course is also a big player in the high-tech diesel-market (Volkswagen Audi Group). Just imagine a plane with a straight-6 BMW Turbo Diesel I'm sure all here know what BMW started as right? And BMW's may be show-off cars but they do excell in engine-making both in terms of performance and quality from what I hear, my late uncle also always drove old BMW's and they just lasted hundreds of thousands of km's and BMW was the only one to attempt to make the engine demanded by McLaren for the F1 streetcar since the quality, specifications and power output demanded was simply thrue the roof, but BMW did it and with more than needed power that engine ran extremely reliable even in racetrim even though the F1 was actually strictly planned as a streetcar. Now if that also goes for the diesels then it could be cool flying

Frank

[Roland]

Frank, let me help you with your questions regarding the diesel engine in aircrafts:

I’ve discussed with the experts on the Diamond DA40/42 Diesel here and found out the following: due to the fact that both engines, the Diesel and the Gasoline engine, are burning machines, there are no big differences in the burning processes. The only advantage of the diesel engine is that it has no critical altitude compared to the gasoline engine. At the critical altitude the burning process in a gasoline engine becomes explosions and therefore “knocking”. You will understand that the performance will be not so good then. The diesel engine has no critical altitude.

But why does Diamond install diesel engines on the new aircrafts? There is no real reason to do so in the case of performance. Also the problems introducing a “new” technology are great. Very! The reason to do this all is an economical one: the prize of the fuel. Diesel engines run longer on the same amount of fuel and this fuel, Diesel or Jet-A1 Kerosene, is a lot cheaper here in Europe.

You found out correctly that Thielert uses an engine from the Mercedes A-Class. Of course it is modified to aviation needs. And it has an electronic injection control. This allows, like on the car, to inject the needed amount of fuel several times per second to allow a better burning process. And it has its turbo.

It is quite complex and not so easy to explain it in short time to the full extent. If I’ve finished the training manual for the DA 42 I think I should send you one. But don’t let my boss know.

[Frank N. O.]

Now that was a new bit of information about the altitude, that's quite interesting. I do know a little bit about diesels since my dad drove diesels both with the big 48 ton Scania roadtrain and our 0.8 ton 1984 Ford Fiesta 1.6 Diesel (that whirlchamber Ford-KHD engine was itself a big step forward in passengercar diesel technology at the time of introduction in 83, my dad could do 25 km/l easily with it and it could still keep up with traffic and was totally reliable, he said it was the best car he'd ever had and he'd driven cars and trucks since from 1958-98 and we had the gasoline carburator 89 Ford Orion 1.6 at the time).

Diesel is getting a bit expensive though, today Shell listed a liter-price of 9.31 DKK which is about 1.25 euro/l.

How many pages is the manual for such a plane btw? I got some pdf-manuals for a Commander 112 and Cardinal RG and they are about 100+ pages. Are modern planes even more complicated (most likely a dumb question but I'll ask anyway)?

Do you know if there are any plans for an engine between the 4-cylinder 1.7 and the 4L V8? A 3L BMW straight-6 Turbodiesel would be nice for most planes where the 1.7 is too small and the V8 too big. Is the V8 also a MB btw?
I found this while searching for diesel planes, is that the new V8? http://www.airliners.net/open.file/0576413/L/

Frank

[Roland]

@ Frank:

Our company is testing a six cylinder Diesel engine but I do not know which make but it could be the BMW you mentioned. Diamond thinks to build a “large” version of the DA 40 with a wider cabin and a six cylinder diesel engine. But more information is classified.

The training manual will have 300 + pages due to many drawings explaining the plane in a simple way. Training manuals of an Agusta 109 Power have around 900 pages … Yes, there are more complex systems involved like the EFIS or Garmin 1000. And at least the training manual should explain the thingies (Dingsbums) more detailed.

Nice picture, btw. The aircraft showing its tail on the left side of the picture is the Pilatus PC 12 of the Boss of Diamond Aircraft Industries, Mr. Dries. If I’m not completely wrong this picture was made in Berlin, Germany, Summer 2005. And the aircraft shown has two props and two engine IN the airframe… Try this, although it is in German, no problem for you

http://www.bredow-web.de/ILA_2004/Grossraumflugzeuge/TT62_Alekto/tt62_alekto.html

[Frank N. O.]

A new engine, that sounds very interesting indeed 

Those sure are some very big manuals for those aircraft but of course they are needed to cover all the systems. you don't have to remember it all by heart do you? It's more like the basics and then you look up when you need specific info for service and repair on specific parts/systems correct?

I think I read the info on the airliners.net-photo that it was from may 2004. On the link you gave it even said that Luigi Colani had a hand in the shape of the plane, and that certainly explains the prop position and the neat design of the windshield as well in my book. It was also interesting to read the data on the plane. It seems there are still small companies making planes, like there are for cars, and that's cool. I just wonder if they started because they are following a dream or they got scorned from a big company like Mr. Ferrari did to both Mr. Lamborghini and Mr. Monteverdi, and probably more but I'm not sure if they managed to build their own cars.

The new engine might be a MB though since I think they also make 6-cylinders, I just mentioned BMW since I know they produce some high-output diesels and they are off course originally a manufacturer of airplane engines so I thought it was fitting.

Frank