maxholstemh1521
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Future Of Diesel Technology

Fri Sep 06, 2013 10:22 am

With all the talk about what will replace 100 low lead for existing airplanes, do you guys think that airframe, and engine manufacturers start pushing diesel technology for new design aircraft? Also, do you guys see more manufacturers doing what Cessna did, and putting a diesel engine on an existing airframe?
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Jetlagged
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RE: Future Of Diesel Technology

Fri Sep 06, 2013 12:26 pm

They already do. The Diamond DA42 had diesel engines in a new airframe. The single engined DA40 has two versions with a diesel powerplant (DA40-D and DA40-NG).
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Starlionblue
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RE: Future Of Diesel Technology

Fri Sep 06, 2013 1:26 pm

Diesel engines are more thermally efficient due to higher compression. However this higher compression means they have to be beefier, and thus heavier. Compromises.

There's probably a power and weight above which diesel makes sense, and under which petrol/gas makes sense. Same as there is a point where turbines makes sense.

I was recently told that fifteen years ago you would never use a turbine if you needed less that the equivalent of 1000bhp. Now you're down to 500bhp turbines being a viable alternative to pistons.

[Edited 2013-09-06 06:27:22]
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rwessel
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RE: Future Of Diesel Technology

Sat Sep 07, 2013 1:22 am

Quoting Starlionblue (Reply 2):
Diesel engines are more thermally efficient due to higher compression. However this higher compression means they have to be beefier, and thus heavier. Compromises.

Yes, although the reduction in fuel requirements seems to net that out as a small weight decrease on typical missions. The SMA diesel on the JT-A 182 is only about 35lbs heavier than the turbocharged O-540 it replaces - you'll make that up in fuel weight after about 90 minutes.

Quoting Starlionblue (Reply 2):
There's probably a power and weight above which diesel makes sense, and under which petrol/gas makes sense. Same as there is a point where turbines makes sense.

Doubtless, although the boundary is likely well under 150hp for engines running on non-leaded gas, and so is largely irrelevant for all but the smallest aircraft applications. And the curves are going to be pretty flat in the area, so there will be some overlap. 100LL is a huge issue in most of the world (as in you can't get it at all, or it costs $20/gal), and outside the US and a handful of other countries, unleaded gasoline or Jet-A are really the only viable options. Even in the US, I have serious doubts about the availability of 100LL for a "reasonable" price more for more than another decade or so.
 
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Aquila3
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RE: Future Of Diesel Technology

Sun Sep 08, 2013 3:21 pm

Wouldn't a Diesel work/be certifiable with Jet-A? It seems to work in some automotive Diesels...
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Starlionblue
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RE: Future Of Diesel Technology

Sun Sep 08, 2013 11:43 pm

Quoting Aquila3 (Reply 4):
Wouldn't a Diesel work/be certifiable with Jet-A? It seems to work in some automotive Diesels...

Jet-A is indeed used in aviation diesels. At airports you only tend to find Jet fuel and avgas anyway.
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MrBuzzcut
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RE: Future Of Diesel Technology

Mon Sep 09, 2013 4:20 am

Quoting Aquila3 (Reply 4):
Wouldn't a Diesel work/be certifiable with Jet-A? It seems to work in some automotive Diesels...

Why not? The remote base I used to work at powered all of their diesel equipment with JP-5, because that is what we had, and it worked just fine for everything from generators to backhoes. IIRC, the JP-5 was actually a better fuel because it met a tighter spec for water and particulate contamination than regular diesel would.
 
rwessel
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RE: Future Of Diesel Technology

Mon Sep 09, 2013 2:08 pm

Quoting Starlionblue (Reply 5):
Jet-A is indeed used in aviation diesels. At airports you only tend to find Jet fuel and avgas anyway.

Indeed. In fact I'm not aware that any of the aviation diesels are actually certified to run on "normal" diesel fuel (despite several of them being derived from automobile engines). The fuels are quire similar though, and I'd expect the engine to run reasonably well, at least so long as it doesn't get too cold (regular diesel will start to gel up at a higher temperature than Jet-A). The Jet-A will be better filtered and more consistently formulated too.

As a general comment, diesels, like turbines, are pretty adaptable to different fuels, unlike gasoline engines. Pretty much so long as you can get it through the injector, it'll run the engine. For radically different fuels, you may need a different injector and high pressure pump system (for example, if you converted your diesel engine or turbine to run on natural gas), but the bulk of the engine will usually not need any changes. Since the fuel never mixes with air until the very moment it's supposed to burn, there's not that very delicate balancing act performed in gasoline engines, where the mixture has to readily burn, but not during the compression cycle, thus leading to a very narrow set of properties for the fuel. There is really no such concept as "octane" or resistance to predetonation in compression ("diesel") engines (or turbines, for that matter).
 
nomadd22
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RE: Future Of Diesel Technology

Mon Sep 09, 2013 4:29 pm

When I was in the Coast Guard they used JP-5 for everything. Ship turbines, ship diesels and helo turbines. Really saved on the logistics.
I'm not sure if it's power to weight as much as fuel weight to gross weight. I remember when Burt didn't want to go with a 10% more efficient rear engine on Voyager because it weighed 14 pounds more, until he figured out that it would save him 1100 pounds of fuel.
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Flighty
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RE: Future Of Diesel Technology

Mon Sep 09, 2013 7:53 pm

Are there good prospects for 4 cyl diesels to get into Cessnas, etc? There has been a lot of progress in turbo gasoline engines as well (run on 91 octane).

It seems like the recent progress in auto industry could spill over to small a/c. Although duty cycles may be too punishing for auto engines.

UPDATE - it seems that Cessna decided to produce only diesel 182s going forward. One"blew an engine" during certification flights  http://www.kansas.com/2013/08/23/296...e-that-made-emergency-landing.html

[Edited 2013-09-09 12:59:33]
 
DiamondFlyer
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RE: Future Of Diesel Technology

Mon Sep 09, 2013 10:07 pm

Quoting Flighty (Reply 9):
UPDATE - it seems that Cessna decided to produce only diesel 182s going forward. One"blew an engine" during certification flights

Incorrect. They are producing natural aspirated 182's on 100LL and phased out the turbocharged 182, to replace it with the diesel.

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rcair1
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RE: Future Of Diesel Technology

Mon Sep 09, 2013 10:16 pm

Described here.

Interesting - they call it a "compression-ignition engine", not a Diesel. Probably so people don't put diesel in it?
http://www.cessna.com/single-engine/turbo-skylane-jta

"The new 227-horsepower compression-ignition SR305-230E-C1 is a drop-in replacement for a turbocharged gas engine, which offers significant fuel-burn reduction. This innovative powerplant design affords you more time between engine overhauls to keep your operating costs at a minimum"
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Starlionblue
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RE: Future Of Diesel Technology

Tue Sep 10, 2013 12:23 am

Quoting rcair1 (Reply 11):
Interesting - they call it a "compression-ignition engine", not a Diesel. Probably so people don't put diesel in it?

Perhaps, though technically it is in fact a "compression-ignition engine" as there are no spark plugs. You can also run it on other things than diesel.
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Okie
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RE: Future Of Diesel Technology

Tue Sep 10, 2013 3:44 am

Quoting DiamondFlyer (Reply 10):
Incorrect. They are producing natural aspirated 182's on 100LL and phased out the turbocharged 182, to replace it with the diesel

The gasoline engine 182 is from what I can tell to be phased out in 2014 and replaced with the T182JT-A.
Cessna does not list the 182 gas burner on their web page at this time, I would not go out on a limb and say you could not order one, you possibly can.
One thing for sure it indicates Cessna's commitment to the "Jet A" burner if they are not offering a gasoline alternative.
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Starlionblue
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RE: Future Of Diesel Technology

Tue Sep 10, 2013 4:10 am

Now if they could only reboot the 172 diesel project... A 182 is lovely but it is a touch too much airplane for flying schools.
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PhilBy
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RE: Future Of Diesel Technology

Tue Sep 10, 2013 6:21 am

Quoting Starlionblue (Reply 14):
Perhaps, though technically it is in fact a "compression-ignition engine" as there are no spark plugs. You can also run it on other things than diesel.

I think that there appear to be linguistic differences to note. Technically 'Diesel' is the term for the compression ignition engine based on the 'diesel cycle' (as opposed to the 'otto cycle') and not the fuel. For example in France the motor is a diesel motor but the fuel is called gasoil. In the UK pumps used to be marked DERV (Diesel engine road vehicle) and only (comparatively) recently have they been marked Diesel. Fortunately a diesel cycle angine can run on a variety of fuels.
 
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Starlionblue
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RE: Future Of Diesel Technology

Tue Sep 10, 2013 6:37 am

You are correct of course PhilBy. Thanks for clarifying.
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DiamondFlyer
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RE: Future Of Diesel Technology

Tue Sep 10, 2013 6:15 pm

Quoting okie (Reply 13):
The gasoline engine 182 is from what I can tell to be phased out in 2014 and replaced with the T182JT-A.
Cessna does not list the 182 gas burner on their web page at this time, I would not go out on a limb and say you could not order one, you possibly can.

I don't see Cessna abandoning the 100LL 182 market in the US. Quite frankly, these JetA piston jobs aren't going to catch on in the US. They're too expensive to retrofit, especially if there is any chance of a drop in 100LL replacement fuel.

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Okie
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RE: Future Of Diesel Technology

Wed Sep 11, 2013 12:25 am

Quoting DiamondFlyer (Reply 17):
They're too expensive to retrofit, especially if there is any chance of a drop in 100LL replacement fuel.

They are working on that.

Quoting DiamondFlyer (Reply 17):
I don't see Cessna abandoning the 100LL 182 market in the US

I did not either but as I posted, Cessna does not list a 182 gasser. My curiosity was trying to figure how much additional up charge there was to go to the "diesel" vs "gas burner" if the factory equipment was the same. It is really hard to get an accurate comparison between aircraft with different avionics and other packages even harder if only one is listed.

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RE: Future Of Diesel Technology

Wed Sep 11, 2013 12:43 am

Quoting DiamondFlyer (Reply 17):
I don't see Cessna abandoning the 100LL 182 market in the US. Quite frankly, these JetA piston jobs aren't going to catch on in the US. They're too expensive to retrofit, especially if there is any chance of a drop in 100LL replacement fuel.

Why "in the US"? I know the US is a special market for aviation but economics are economics. If the price of new aircraft and/or retrofit plus the operating costs make it a viable proposition, customers will gravitate towards the diesel solution.
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DiamondFlyer
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RE: Future Of Diesel Technology

Wed Sep 11, 2013 2:36 am

Quoting Starlionblue (Reply 19):
Why "in the US"? I know the US is a special market for aviation but economics are economics. If the price of new aircraft and/or retrofit plus the operating costs make it a viable proposition, customers will gravitate towards the diesel solution.

Because the cost of 100LL is vastly lower in the US than anywhere else in the world. So much so that a majority of light airplanes would never make up the difference in operating costs when you consider that it costs roughly $70,000 USD to retrofit a 172 with a diesel engine.

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Starlionblue
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RE: Future Of Diesel Technology

Wed Sep 11, 2013 3:11 am

Quoting DiamondFlyer (Reply 20):
Quoting Starlionblue (Reply 19):
Why "in the US"? I know the US is a special market for aviation but economics are economics. If the price of new aircraft and/or retrofit plus the operating costs make it a viable proposition, customers will gravitate towards the diesel solution.

Because the cost of 100LL is vastly lower in the US than anywhere else in the world. So much so that a majority of light airplanes would never make up the difference in operating costs when you consider that it costs roughly $70,000 USD to retrofit a 172 with a diesel engine.

Point. In any case I don't think retrofit will be the majority of it. Much more likely to find a diesel in a new build.

There may be a point in the future where dieseltech has progressed to the breakpoint even in the US. Compare with the rise of diesel in Europe, with more than half of cars sold today being diesel. Thirty years ago, this would have been unthinkable but modern diesels make it work. If gas prices continue to rise compared to diesel and diesels continue to become lighter and more efficient.
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Flighty
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RE: Future Of Diesel Technology

Wed Sep 11, 2013 3:41 pm

Quoting Starlionblue (Reply 21):
Much more likely to find a diesel in a new build.

Yes. We should keep in mind, Cessna sells new airplanes. That's a tiny, tiny market and they are barely surviving AFAIK with this business model. New aircraft are expensive. But diesel is one way they might maybe compel some sales. The new build market can afford $70k without any trouble.

The secondhand market is another story. It will take decades to clear out the secondhand gas fleets. But the secondhand would want diesel if they could afford it. So these compression ignition planes will have good resale, which ironically means Cessna might sell more new ones. That is how BMW sells cars.
 
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RE: Future Of Diesel Technology

Wed Sep 11, 2013 3:52 pm

Quoting Flighty (Reply 22):
The secondhand market is another story. It will take decades to clear out the secondhand gas fleets. But the secondhand would want diesel if they could afford it. So these compression ignition planes will have good resale, which ironically means Cessna might sell more new ones. That is how BMW sells cars.

Remember, people throw away cars every 10 year or more often. How many cars from the 1980's do you see reguarly driving around? Most of the GA fleet today is at least 1990 or older. A good bit of it is from the 60's and 70's. When an airplane only costs 50,000 to 100,000 used, why on earth would someone spend another 70K to retrofit a diesel engine on when they can just install overhauled for 1/2 that? Other than airplanes that are used to make money, I don't see diesel ever getting a big market share in the GA world.

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Okie
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RE: Future Of Diesel Technology

Wed Sep 11, 2013 4:57 pm

Quoting Starlionblue (Reply 19):
Why "in the US"? I know the US is a special market for aviation but economics are economics. If the price of new aircraft and/or retrofit plus the operating costs make it a viable proposition, customers will gravitate towards the diesel solution

There are just too many aircraft in GA service to justify change over, especially economically, some old aircraft not counting warbirds or specialty aircraft are 40-50 years old and still viable for use in GA applications.

100LL is facing several problems on the supply side, equipment has to be segregated from manufacturing all the way to the delivery equipment to prevent the tetra ethyl from entering other fuel sources.

GAMI and Swift are both working on a drop in replacement but they are sort of running into the same issues with segregation since auto fuel is starting to be required to contain ethanol. Ethanol is just not compatible with the fuel systems along with some other issues. I think the main issue is that government regulations are holding up the approval process.

Just remember that automobiles are doing just fine without lead, actually better but that is largely due to electronic timing and ignition. although that technology is not available for the old magneto ignition power plants on aircraft.

Just remember to the naysayers, about 95% of the Old Mechanics Tails about the pitfalls of removing lead from Avgas are untrue.

Quoting Flighty (Reply 22):
Yes. We should keep in mind, Cessna sells new airplanes. That's a tiny, tiny market and they are barely surviving AFAIK with this business model. New aircraft are expensive. But diesel is one way they might maybe compel some sales. The new build market can afford $70k without any trouble

I think the big issue has been getting enough aircraft/engine sales volume to distribute the costs of certification and manufacturing.
The list price that I found for a 2012 was about $400K a 2014 Jet A is $515K. That is a heck of a lot more than $70K.

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Flighty
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RE: Future Of Diesel Technology

Wed Sep 11, 2013 7:28 pm

Quoting DiamondFlyer (Reply 23):
When an airplane only costs 50,000 to 100,000 used, why on earth would someone spend another 70K to retrofit a diesel engine on when they can just install overhauled for 1/2 that?

Yeah, but Cessna isn't selling new planes to those people at all.

Quoting okie (Reply 24):
Ethanol is just not compatible with the fuel systems along with some other issues. I think the main issue is that government regulations are holding up the approval process.

Great, hadn't heard of that. E85 conversion has to be be cheaper than a repower.
 
DiamondFlyer
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RE: Future Of Diesel Technology

Wed Sep 11, 2013 8:26 pm

Quoting Flighty (Reply 25):

Yeah, but Cessna isn't selling new planes to those people at all.

Cessna is barely selling airplanes at all. The only way an engine like this takes hold, is by market share. And with the rate light singles come off the line these days, there will never be any kind of market share gained by the engine.

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Starlionblue
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RE: Future Of Diesel Technology

Thu Sep 12, 2013 12:39 am

Quoting okie (Reply 24):
some old aircraft not counting warbirds or specialty aircraft are 40-50 years old and still viable for use in GA applications.

Tell me about it. I did my multi on an airplane built in 1957. The first hour or so I cringed during every steep turn, worrying the wing spars would snap in a cloud of rust. Apparently they inspect planes regularly though so we were ok.  To be fair that thing was built like a tank, and flew like one on one engine.

But I digress...
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