Diesel engine and aviation

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Mafoo

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Mafoo
So in the little research I have done on the subject, it seems there is really no downside, and lots of upsides to a diesel.

This must be the byproduct of visiting all pro-diesel websites, or every GA aircraft would be equipped with one.


So what are the downsides to them, and would you want a GA aircraft with one in it?
 
I think it's only a matter of time before we see Jet A being the fuel of choice, and diesel engines burning it in light general aviation airplanes. Viable choices are coming on the market and are already found available in light aircraft. Avgas is hard to find internationally, and refined and available from very few sources today. The cost continues to climb, the market is small.

Diesel makes a lot of sense, and no doubt will eventually likely become the fuel of choice as more powerplant options become available.
 
weight is the biggest single drawback for diesel in GA, I think. I assume they've made progress on that front, but haven't read up on any of the Thielert info of a few years ago
 
Mafoo said:
So what are the downsides to them, and would you want a GA aircraft with one in it?
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Priced a Deltahawk recently? How does $60,000 before the installation sound for you? And no, SMC is not any cheaper. Back in 2000 the F/F on 172 was $44k. It is breaking $100k.
 
Mafoo said:
So what are the downsides to them,
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Weight and cost.
...and would you want a GA aircraft with one in it?
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Sure -- at the right price. If they can deliver me a diesel for my Tiger at something approximating the cost of overhaul plus core value of my current engine, I'd do one in a heartbeat when it's time for the next overhaul.
 
gkainz said:
weight is the biggest single drawback for diesel in GA, I think. I assume they've made progress on that front, but haven't read up on any of the Thielert info of a few years ago
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+1.......................

When I started my Zenith 801 experimental build I plumbed the fuel system for the DeltaHawk diesel. I even got a delivery position and offered to R&D the firewall forward kit for the 801 series..... They basically laughed and told me they were much more qualified to do that.... Altho that didn't stop DeltaHawk from using a pic of my plane on their website... :mad:... It has been 11 years and they still have not delivered a motor to any builder that I know of.... I have been flying my V-8 since 2004 and 400+ hours........:confused::confused:.

I am a huge diesel fanatic and as soon as a viable one comes along I "might" even remove the Ford and put a kerosene burner in..:yesnod::dunno:
 
Mafoo said:
So what are the downsides to them, and would you want a GA aircraft with one in it?
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Cost and availability. Also, some of them are built on common rail injector platforms which require :hairraise: electricity :hairraise: (Oh the humanity!!! :rolleyes:) for injection. For some reason many pilots are of the belief that the common aircraft bronze age mechanical fuel injection technology is actually reliable and electronic injection isn't.

Would I want one? Depends on cost. But otherwise, why not?
 
Capt. Geoffrey Thorpe said:
Would I want one? Depends on cost. But otherwise, why not?
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Has anyone designed one yet that can keep running after an electrical failure?

It sucks to have your life depend on detecting an alternator failure, whereas it most likely wouldn't have been life critical with a more traditional engine. At least you keep the vacuum powered instruments and can stay aloft as long as you have fuel (though you can't read the fuel gauges).

While you can say that a good pilot "should" detect an alternator failure prior to it becoming a power failure, there are quite a few cases where this doesn't happen. With electrical injection, now it's an engine failure, i.e., much more serious.
 
MAKG1 said:
Has anyone designed one yet that can keep running after an electrical failure?

It sucks to have your life depend on detecting an alternator failure, whereas it most likely wouldn't have been life critical with a more traditional engine. At least you keep the vacuum powered instruments and can stay aloft as long as you have fuel (though you can't read the fuel gauges).

While you can say that a good pilot "should" detect an alternator failure prior to it becoming a power failure, there are quite a few cases where this doesn't happen. With electrical injection, now it's an engine failure, i.e., much more serious.
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That is a shallow conclusion...

My plane depends on a constant source of electricity to fire the ignition system.. I designed in a 15 hour "window" of safety by installing a oversized capacity battery to store enough juice to power the ignition for a LONG time, even after a alternator failure... In fact the DAR that inspected my plane asked that specific question.. I demonstrated to him that I would have to land and refuel 4 times before the battery lost the ability to run the ignition system... I even told him " If I a dumb enough to take off and land 4 times before I get the alternator fixed then I deserve to crash" He agreed 100% and signed off my experimental right there..:yesnod:.

The point is, with a large capacity battery, a diesel running an all electric common rail fuel injection system can have a wide margin of safety simply by using a large enough battery to get them to an airport before they need more fuel... :idea: IMHO.
 
What Ben said.

It's an engineering problem, not a fundamental design flaw. Turbines also need a continuous source of electricity and their designers seem to have sorted it out.
 
Old Geek said:
Turbines also need a continuous source of electricity and their designers seem to have sorted it out.
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Well, turbines don't need an electrical source to continue ignition once it's the start sequence is finished.
 
Old Geek said:
My mistake. I was thinking FADEC engines.
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I believe those have back-up on-engine electrical power sources in case the airframe electrical power system fails completely, so it takes multiple electrical failures to lose the FADEC and thus the engine. In addition, the FADEC engines on the projects I worked (F119 and F135) had dual, redundant FADECs in case one took a bullet.
 
So an alternator failure is the only electrical power failure? I gave it as an example, not as the whole problem.

What if you get smoke in the flight deck? Conventional engine = turn off the master, open the window and land with power.

What if you pop circuit breakers?

With more complex electrical systems, you also have many more opportunities for undetected wiring damage. How do you handle an electrical fault in the injection system? Conventional injectors fail closed. Would you fail them open? Then, you may flood the engine, and you'll certainly run partial power. And that occurs with known electrical problems, so there may be some fire risk associated.

Yes, these are engineering problems. They are not insurmountable, but they are a bit more complex than throwing a big heavy battery in and saying you're done.

I suspect the solution may drive you to a twin engine, fully redundant aircraft.
 
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So an alternator failure is the only electrical power failure? I gave it as an example, not as the whole problem.

What if you get smoke in the flight deck? Conventional engine = turn off the master, open the window and land with power.

What if you pop circuit breakers?
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No different with a diesel powered engine. Just a different type of fuel.
 
SMA's diesel is fadec with a mechanical backup. An electrical failure won't kill it.
 
Mafoo said:
So in the little research I have done on the subject, it seems there is really no downside, and lots of upsides to a diesel.

This must be the byproduct of visiting all pro-diesel websites, or every GA aircraft would be equipped with one.


So what are the downsides to them, and would you want a GA aircraft with one in it?
Click to expand...

I'm waiting for Continental to come out with the 6 cyl/350hp version of the 4cyl/230hp Diesel they bought from SMA a couple years ago just before the Chinese bought them. The USAF is waiting for the 4cyl. The Junkers Jumo was an interesting opposed piston (2 crankshafts with piston tops working towards each other to form the combustion chamber). The problem prior to digital common rail injection was the weight required to deal with the strong power pulses. During WWII Caterpillar made a 450hp Diesel(notice the upper case D, Diesel was the man's name) version of the R1820 which typically was a 1200-1435 HP engine on gasoline.
 
;)
MAKG1 said:
So an alternator failure is the only electrical power failure? I gave it as an example, not as the whole problem.

What if you get smoke in the flight deck? Conventional engine = turn off the master, open the window and land with power.

What if you pop circuit breakers?

With more complex electrical systems, you also have many more opportunities for undetected wiring damage. How do you handle an electrical fault in the injection system? Conventional injectors fail closed. Would you fail them open? Then, you may flood the engine, and you'll certainly run partial power. And that occurs with known electrical problems, so there may be some fire risk associated.

Yes, these are engineering problems. They are not insurmountable, but they are a bit more complex than throwing a big heavy battery in and saying you're done.

I suspect the solution may drive you to a twin engine, fully redundant aircraft.
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I didn't want to go into the details of my redundent electrical architecture
set up I crafted on my experimental out of fear some guys /gals would not understand the entire concept.. Since you asked a specific question I will give a brief description... I have several electrical busses. The main buss is energized by the master contactor and feeds all devices. The secondary one still goes through the master contactor but supplies power to essential stuff like com 1, transponder, electric fuel pump and most importantly the ignition system... Since I have a high wing all of my fuel pumps can quit and gravity will supply the motor with enough fuel for 60% power output. If the complete electrical system fails I have a third source to power the ignition that comes DIRECTLY from the pos terminal of the 1000 CCA battery straight to the #2 ignition box, that is run up to the panel through a insulated chase so the plane can be on fire and the main electrical system can have a dead short and my motor will still run to get me on the ground safely..... YMMV.. :yesnod:;)
 
N801BH said:
;)

I didn't want to go into the details of my redundent electrical architecture
set up I crafted on my experimental out of fear some guys /gals would not understand the entire concept.. Since you asked a specific question I will give a brief description... I have several electrical busses. The main buss is energized by the master contactor and feeds all devices. The secondary one still goes through the master contactor but supplies power to essential stuff like com 1, transponder, electric fuel pump and most importantly the ignition system... Since I have a high wing all of my fuel pumps can quit and gravity will supply the motor with enough fuel for 60% power output. If the complete electrical system fails I have a third source to power the ignition that comes DIRECTLY from the pos terminal of the 1000 CCA battery straight to the #2 ignition box, that is run up to the panel through a insulated chase so the plane can be on fire and the main electrical system can have a dead short and my motor will still run to get me on the ground safely..... YMMV.. :yesnod:;)
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Like Ben, my airplane will also be electron-dependent, not for the ignition since I will carry one mag but for the dual electric fuel pumps (no engine-driven pump). It's a relatively simple task to design an electrical system with several layers of protection. I have a main buss that carries everything, a backup buss that carries only flight-critical items and can be supported solely by the backup alternator in the event of primary alternator failure, and then I have the ultimate shutdown with battery power only to the pumps and everything else is dark. My battery (on paper anyway) is good for 2 hours of running the fuel pump in this case.

I'll carry dual alternators and my EFIS screens have their own internal backup batteries that are good for an hour, so even in IFR with both alternators down (pretty unlikely scenario) I have an hour of full capability plus another hour without screens. The idea of an electron-dependent aircraft does not scare me, it's just a limitation that needs to be planned for.

As for the diesel engine - I'll put one in my airplane in a heartbeat, just as soon as someone has one at an APPROPRIATE cost. We don't have that option today and it appears we won't for a while. I'm an optimist, I put return lines in my tanks and set up the fuel system to go either way.
 
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N801BH said:
;)

I didn't want to go into the details of my redundent electrical architecture
set up I crafted on my experimental out of fear some guys /gals would not understand the entire concept.. Since you asked a specific question I will give a brief description... I have several electrical busses. The main buss is energized by the master contactor and feeds all devices. The secondary one still goes through the master contactor but supplies power to essential stuff like com 1, transponder, electric fuel pump and most importantly the ignition system... Since I have a high wing all of my fuel pumps can quit and gravity will supply the motor with enough fuel for 60% power output. If the complete electrical system fails I have a third source to power the ignition that comes DIRECTLY from the pos terminal of the 1000 CCA battery straight to the #2 ignition box, that is run up to the panel through a insulated chase so the plane can be on fire and the main electrical system can have a dead short and my motor will still run to get me on the ground safely..... YMMV.. :yesnod:;)
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That's quite nice design, but there is still one hole I'd like to hear about.

It's not unheard of for an injector to fail to a dead short. Are your injectors wired redundantly as well, or does one dead short kill them all? It's also not unheard of for an injector to partially short across windings, which results in low resistance. For the common simple parallel wiring, the bad injector draws much more current than the others, and can starve them all if it doesn't just blow the circuit. Can your engine run safely with a dead cylinder?

As an engineer, it's complexity that makes me nervous. Due to failure modes, most traditional aircraft engines have no spark advance, even though if they did (along with the associated knock sensor), they would operate at lower fuel flows, with greater power, as they could push the advance to the detonation limit. But the failure modes mean significant power loss or detonation.
 
MAKG1 said:
That's quite nice design, but there is still one hole I'd like to hear about.

It's not unheard of for an injector to fail to a dead short. Are your injectors wired redundantly as well, or does one dead short kill them all? It's also not unheard of for an injector to partially short across windings, which results in low resistance. For the common simple parallel wiring, the bad injector draws much more current than the others, and can starve them all if it doesn't just blow the circuit. Can your engine run safely with a dead cylinder?

As an engineer, it's complexity that makes me nervous. Due to failure modes, most traditional aircraft engines have no spark advance, even though if they did (along with the associated knock sensor), they would operate at lower fuel flows, with greater power, as they could push the advance to the detonation limit. But the failure modes mean significant power loss or detonation.
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Injector problems would occur (or not) to any aircraft, regardless of electrical system design.
 
airguy said:
Injector problems would occur (or not) to any aircraft, regardless of electrical system design.
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Not at the same frequency, and not with the same symptoms. As a mechanical injector wears, the engine slowly runs poorer. Electrical injectors (and any other solenoid) have a tendency to fail suddenly. Mechanical injectors all tend to be independent, as well. While electrical injectors can be designed that way, the simple (and simple = reliable to a large extent) designs don't comply.

Now, the metered orifices used in some "injected" aircraft engines have no moving parts and simply will not fail in this manner at all.
 
Fuel systems "injectors" on diesel engines vary considerably. They can be completely mechanical using a dedicated lobe on the cam shaft to compress and inject the fuel into the cylinder (big syringe); electro-mechanical using a solenoid to control when (timing) the injection takes place by varying the height of the injector, using fuel or engine oil, but still rely on the cam to compress and inject; or completely electric using a high-pressure pump to produce the rail pressure (common rail) and a solenoid to release the pressure at the precise time. Diesel injection fuel pressure is in the 20K-30K PSI range and it is typically injected directly into the combustion chamber.

Automotive fuel injectors for "gas" are completely different animals. They typically are not direct injection and the rail pressure is much lower; usually less than 100 psi.
 
Yes, the discussion is about common rail injectors. It stemmed from a poster not understanding why those might make some people nervous.

While the details are indeed different, gas injectors are not totally different animals from those. It's still a set of solenoids in a harsh environment, and has all the failure modes that implies.
 
MAKG1 said:
That's quite nice design, but there is still one hole I'd like to hear about.

It's not unheard of for an injector to fail to a dead short. Are your injectors wired redundantly as well, or does one dead short kill them all? It's also not unheard of for an injector to partially short across windings, which results in low resistance. For the common simple parallel wiring, the bad injector draws much more current than the others, and can starve them all if it doesn't just blow the circuit. Can your engine run safely with a dead cylinder?

As an engineer, it's complexity that makes me nervous. Due to failure modes, most traditional aircraft engines have no spark advance, even though if they did (along with the associated knock sensor), they would operate at lower fuel flows, with greater power, as they could push the advance to the detonation limit. But the failure modes mean significant power loss or detonation.
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Rare as hell in my experience, and in fact, in tens if not hundreds of thousands of hours of digital and HP common rail systems to the original set of 16-149 DDECs Stewart Stevens put in, I have never seen that failure mode. There were early teething issues but within 90 days they had the bugs chased and the reduction in fuel wasted as smoke was noticeable in a real $$$ savings. The State of California had a fund that paid to repower the entire work boat fleet from old 12-71s to digital control engines not more than 10% greater in power. This fund was established in part as compensation for the low surfer fuel mandate that required the overhaul of injection systems whose seals basically were addicted to sulphur and failed without it. I doubt you could even find the most no tax conservative who complains about that bill.

I would have no reservation about using a single point HPCR system in a plane but then I will be fully redundant in engines. I offered up my plane and flying to do the certifation test sled work.
 
Baron2PG said:
Fuel systems "injectors" on diesel engines vary considerably. They can be completely mechanical using a dedicated lobe on the cam shaft to compress and inject the fuel into the cylinder (big syringe); electro-mechanical using a solenoid to control when (timing) the injection takes place by varying the height of the injector, using fuel or engine oil, but still rely on the cam to compress and inject; or completely electric using a high-pressure pump to produce the rail pressure (common rail) and a solenoid to release the pressure at the precise time. Diesel injection fuel pressure is in the 20K-30K PSI range and it is typically injected directly into the combustion chamber.

Automotive fuel injectors for "gas" are completely different animals. They typically are not direct injection and the rail pressure is much lower; usually less than 100 psi.
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Mechanical injection Diesels require too high of a weight to power ratio to be practical for light aviation, you need to get into stuff like the big early post WWI flying boats to make those weights work with ending up like the original GM 5.7 Diesel whiCh was a 350 Olds engine with a rotary injector pum where the distributor was and injector nozzles where the spark plus were. Problem was the webbing couldn't handle it and they would hammer the cranks out of the bottom ends. HPCR technology allows for dwelling a high pressure, high efficiency spray pattern over a longer period giving a much smoother, cleaner, more efficient burn which allows us the ability to really lighten cases and cylinders. I think the Diesel 1820 fitted with a HPCR system could provide a reliable 900-1100+ HP on half the fuel of a PT-6 using current case casts and air cooled cylinders.
 
A couple weeks back AWST had an article stating that Cessna would be offering a diesel powered 182 starting next year. I just scanned the article but it seemed like they were saying a 2800 hr TBO and 70k extra for the diesel. I'll see if they posted it in the online version and see if a link will work, it is a subscribers only website.
 
Threefingeredjack said:
A couple weeks back AWST had an article stating that Cessna would be offering a diesel powered 182 starting next year. I just scanned the article but it seemed like they were saying a 2800 hr TBO and 70k extra for the diesel. I'll see if they posted it in the online version and see if a link will work, it is a subscribers only website.
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Is that $70K more than the standard Skylane or the turbo Skylane that the diesel is replacing, which is $443K.
 
I am diesel junky as well and absolutely love my 7.3L F250.... To bad the 7.3L wont't fit in a 172.... LOL I am actually late to the party I just found out there are diesel replacements for the 172 and 182. My 7.3L uses oil pressure to feed the fuel so I do not see why an aircraft engine cannot do the same. In fact I had to drive it over 100 miles once without an alternator with my HID lights on. West Texas can be unforgiving and is very desolate. What I want to know is how they keep the Diesel / Kerosene from jelling at colder temperatures.
 
Robert, the "diesel" engines run on Jet-A fuel, and Prist can be added for low temp operation (or at least it can be added to Jet-A in turbine applications). The diesel moniker is the engine design, not the fuel used...though I'm sure the engines will run on auto diesel or k-juice.
 
Mike I said:
Seems to be $515k: http://www.aopa.org/oshkosh/2012/news/120723cessna-unveils-turbodiesel-182.html
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Thanks. So, at least then, they were expecting a 16% increase in base price. Lower fuel usage and cost per gallon and a longer range, but that's still a healthy increase. Wonder what else they're getting for the money?

Mike I said:
Robert, the "diesel" engines run on Jet-A fuel, and Prist can be added for low temp operation (or at least it can be added to Jet-A in turbine applications). The diesel moniker is the engine design, not the fuel used...though I'm sure the engines will run on auto diesel or k-juice.
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Yes, they are certified to run on Jet-A. I read that they will run on but are not certified with other fuels because of the variability in standards. And, just for the record, the model has been renamed the Turbo Skylane JT-A. Apparently "NXT" was already used by another company for another aircraft type.
 
Kinda like my torpedo heater for the hangar. It'll run on diesel, kerosene, Jet-A... It doesn't care. It's just a tiny dumb little turbine.

I joke that it's the closest I'll get to owning a Turbine. Haven't run any Jet-A through it yet, though.
 
gprellwitz said:
Thanks. So, at least then, they were expecting a 16% increase in base price. Lower fuel usage and cost per gallon and a longer range, but that's still a healthy increase. Wonder what else they're getting for the money?
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If the diesel 182 costs $70K more, that means that the diesel engine installation costs $70K plus whatever value the not-installed IO-540 would have had. I would figure that the diesel engine is therefore at least $110K or more.

Which fits fairly well with the conversion cost of the 182Q, the only other 182 that has an STC to install the SMA diesel. That's north of $100K, too.

Dan
 
The Cessna 182 with the turbo-diesel sounds like big news to me.

I'm guessing that until now, there hasn't been a new piston engine put in a certified US-built airframe in decades.

Moreover, it provides a real alternative for the post-100LL world that will come eventually.
 
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