Airborne diesels

diesel_freak

Veteran Member
Joined
Apr 7, 1999
Location
Troy, Ohio
Developments both here and in France are pointing to the future of light aircraft powerplants and that future is diesel engines running on Jet-A fuel.

First off the block is Morane, a partnership between Renault and Socata, the general aviation arm of the French aerospace giant Aerospaciale. They have developed a family of six cylinder, air cooled, turbocharged diesels ranging from 200 to 300 hp. The engines are currently testing in France, and Socata has announced that it will offer the engine in its top piston-engine model, the Trinidad, even in the US. The 300 hp version claims a fuel burn of about 15 gph at full power and 10 gph at cruise. That is approximately 45% better economy than a gasoline engine of equal power.

Teledyne Continental Motors is using a NASA research grant to develop a two-stroke, four cylinder turbodiesel. Lycoming has joined forces with Italian diesel specialist VM Motori (a Detroit Diesel subsidiary) to develop a four-stroke airborne diesel engine.

Both American engine manufacturers are significantly behind Morane, as the French company enjoys a two year head start and the know-how of Renault Sport, which has the development talent and time since their pullout from Formula 1.

As a pilot, I see nothing but advantages to a diesel engine. No antiquated magneto ignition, huge torque at low rpms (where it is needed most), tremendous fuel economy, longer durability (Morane predicts a time-between-overhauls of 3000 hrs, the typical 300 hp aero engine is lucky to reach 2000), and cheaper fuel. The price difference between Jet-A and Avgas is about $.20/gal in the US, but around $2.00 in Europe, making our aircraft more attractive to European buyers. It remains to be seen how the typically ultraconservative American aircraft owner will respond to this, though. I have a feeling that the company I work for will dismiss diesel engines like it has missed other market opportunities, and hand it over to the competition.
 
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mickey

Guest
I'm not a pilot myself (in fact I've actually never been airborne in my life, believe it or not) yet I've wondered about diesel aircraft for years. I sure seems like a "why didn't they think of it before" kind of thing to me.

Why are so many aircraft engines air-cooled? Is it just a weight/reliability question, or are other factors involved? Diesels are so sensitive to temperature that I would expect that water-cooling would be the way to go, in order to maintain a more constant temperature and prevent excessive heat loss.

-mickey
 
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mickey

Guest
By the way, I understand that redundancy is important in the fuel and ignition systems in an aircraft engine.(For obvious reasons.) The Pumpe Duse design would seem to be the perfect solution, to me. No ignition system at all, and each injector is it's own fuel pump. With some kind of "limp home" feature to keep it firing in the event of an ECU failure, I'd feel pretty secure with my life depending on one of those things! An ECU might not even be necessary at all. The injector nozzle could open when a preset pressure is reached, and the turbo/wastegate control could be the same simple setup already used in aircraft engines. The fuel economy would suffer a little bit without the precise computer control, but it would be as reliable as a stove bolt.

-mickey
 

diesel_freak

Veteran Member
Joined
Apr 7, 1999
Location
Troy, Ohio
Most light airplane engines are air cooled for two reasons: less weight and less complexity. You would not believe how weight sensitive light airplanes (less than 8000 lbs MTOW) are. No cooling system is one less thing to fail and to maintain.

The Morane diesels are aircooled, and I have not read of any problems coused by this. I believe both the Continental and Lycoming designs are aircooled, but I can't swear to it.

As to why diesels have not made inroads into aviation, I can give you two reasons: the steep cost of an FAA certification program, and the "if it ain't broke don't fix it attitude" of the general aviation community. The recent push to diesels comes from two sides. Socata decided to pursue it as a solution to the high fuel costs in Europe. The american companies are getting much help from NASA and the FAA under the AGATE (advanced general aviation technology experiment) program.
 

diesel_freak

Veteran Member
Joined
Apr 7, 1999
Location
Troy, Ohio
Mickey, I believe you have just described the control system philosophy that these diesel engine developments are pursuing.

It might shock people to know that aircraft reciprocating engines use nothing more sophisticated than the ignition found in a Briggs and Stratton lawn mower engine: magnetos. Magnetos can run independently of any external electrical power, and aircraft engines have two independent ignition systems, each with its own magneto.
 

BRUSSELS BELGIAN

Old Whig
Joined
May 26, 1999
Location
Aston,Pa. USA
TDI
1997 Passat TDI
MICKEY: Since I am a World War II buff, I will speak for the Japanese experience of favoring air-cooled radial engines for almost all naval aircraft and many army planes. The concern was simplicity, but also ability to sustain damage and continue flying. For example, there was a case of an American P-40 in China (Flying Tigers) which was shot down by ONE BULLET hitting the radiator hose and draining the coolant(engine seizure). Ironically, the Americans favored the in-line, water-cooled engines because the narrower front profile gave a little more SPEED. Some things never change!
 

diesel_freak

Veteran Member
Joined
Apr 7, 1999
Location
Troy, Ohio
Actually, ALL USN and USMC WW2 combat aircraft were powered by radial engines, as were about half the AAF fighters and virtually all its bombers and transports.

European Air Forces showed a distinct predilection for watercooled engines.
 

BKmetz

Administrator, Member #10
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Sep 25, 1997
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Illinois
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2015 Passat, titanium beige, 6MT
The German air force in WWII had a cargo plane with diesel engines. Some WWII buffs could probably give more detail.

Brian, post war baby boomer
 

Randy W

Veteran Member
Joined
Jun 2, 1999
Location
Orlando, FL USA
Greetings Gentlemen:

In my experiences as both an pilot and a maintenance technician, I can see a whole host of problems getting a diesel powerplant into the general aviation community here in the US.

I will list some of them to help you see the HUGE hurtle (sp?) that this technology has to overcome.

1) Liability: This one is probably the only one we need mention as it is the singe biggest cost per aircraft of any type in the nation. Thanks to the 'Deep pockets' theories of litigation and to the 30 year battle to win limits on liability (now limited to 20 years per airframe). The new Diesel powerplant is not covered by existing legislation and would get the most attention as soon as it hit the market.

2) Complexity: With some aviation aircraft using nothing more than gravity feed and a bobbing stick to operate fuel to the engine, it is difficult to imagine getting the high pressure fuel delivery systems, along with the associated pump architechture onto an aircraft without sacrificing weight. Not to mention the tragedy that could be inflicted if there were an inflight fuel emergency. Gasoline is fairly forgiving, diesel is not. (see issue #1)

3) Handling: Aircraft are dirty enough with the way they leak fluids/oil. When you add the peculiar nature of diesel into that, you would have a entire new industry arise just to keep the aircraft clean. And I for one have absolutely no interest doing a 100 hr inspection on a diesel powered aircraft where I would have to scrub down the entire aircraft prior to beginning. That would also remove any indicator of failure that is normally present.

Just my .02. It seems like a good idea, but it would be a miracle for it to find it's way into this country in any of our lifetimes.
 
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mickey

Guest
Randy W: The new Pumpe Duse engine doesn't even have a high-pressure fuel pump. Each unit injector acts as it's own pump, and is driven directly by cam lobes. Fuel is delivered to the injectors by galleries in the head, no by rubber hoses. I cannot imagine a simpler, or lighter arrangement than that.

Aircraft leak fluids and oil? That's the best argument I've heard yet for some new technology! Why the hell do they leak? There's no reason for it. Yes, the exhaust is a little sooty. Solution: Paint the wings black.

-mickey
 

N Dennis

Veteran Member
Joined
Mar 18, 1999
Location
Napa, CA USA
Randy, what makes you think a diesel-powered airplane's fuel injection system would be any more complex than what is on a Lycoming IO-360? Diesels have used mechanical fuel injection systems a lot longer than general aviation aircraft. I can not see them being any more of a pain in the ass than what is already out there. There are diesel engines with self priming injectors,(I have owned one of these engines since Sept 94) so I don't really see an issue there. The Liability issue I can understand your position on. As long as people are stupid enough to make a manufacturer of airplanes liable for the pilots screwup then changes will be slow in coming. The pisser of the whole deal is the whole tort process which rewards the survivors of the persons who causes the crash to begin with. One word: assinine. As far as the dirtiness of diesel fuel, these diesel engines that are being developed won't be drinking diesel anyway. They will be using Jet A, so you should not have a worry there. No different than working on a turbine(except less costly parts wise). I have seen Lycoming and Continental engines a hell of a lot dirtier than my Powerstroke(with 102,000 miles) or my D-50(which had 167,000 miles on it when it died).
 

diesel_freak

Veteran Member
Joined
Apr 7, 1999
Location
Troy, Ohio
Ditto. It is my prediction that diesel powered piston engine airplanes will be on sale in the US within 5 years, and they will meet with good success (Socata being the pioneer). I also predict that The New Piper Aircraft Company will be the first US airframe manufacturer to get in the act. I can't see Raytheon or Cessna taking the lead because business jets are their bread and butter. Piper's major revenues come from reciprocating engine private airplanes.

P.S. The new limit on aircraft liability is 18 years, not 20.

[This message has been edited by 16vforever (edited July 17, 1999).]
 

Bry

Well-known member
Joined
Jun 30, 1999
Location
Atlanta, Georgia, USA
On the theme of "there's nothing new under the sun..."

As Brian had earlier said, the German Luftwaffe made use of diesel engines in their aircraft prior to and during the Second World War. The powerplants were officially known as the Junkers Jumo 205, and Jumo 207, and existed in many variants. It was a "six-cylinder vertical opposed piston, compression ignition, two stroke engine." I've seen the engines rated output from as low as 600hp for the 205C, to as high as 950hp for the 207A-1/B variant (depending upon altitude and application). Quite an accomplishment! There were two pistons firing in each cylinder! Talk about German efficiency! Anyway, these torquey beasts were put usually in lumbering seaplanes, some of the less fancy medium range bombers, and also bombers that were used for photo-reconnaisance--roles being ideally suited for an engine that could produce greater endurance (and consequently, range) and/or the ability to loiter around a specific site. If memory serves there was even one plane which carried one of these engines in the fuselage solely to power the supercharger and electrical gizmos on the plane, and was fired up only when needed.

Its actually quite amazing what the Germans were willing and able to do with powerplants back then. If it could be a source of propulsion they would inevitably figure out a way to harness it. Hence their use of the pulsejet, turbojet and rocket powered aircraft later in the war. The Junkers Jumo 205/207 was simply an earlier instance of such creative applications that the Germans would later become famous for using in their so-called "secret weapons."

If I can remember more or I unearth anything else, I'll post it if there is interest.

Bry (a "Gen X'er")

------------------
96 Passat tdi


[This message has been edited by Bry (edited July 21, 1999).]
 
S

SkyPup

Guest
Speaking of unreliable piston airplane engines, I am never understanding of the crummy updraft carbs used in the Lycoming or Continental engines, these things are a constant mess and hassle to keep functional without a flame out. Surprised that someone would rely on one of these a few thousand feet up in the air as they are totally unreliable in an airboat a few thousand feet from the shore!
 

N Dennis

Veteran Member
Joined
Mar 18, 1999
Location
Napa, CA USA
Just read an article in the July 23, 1999 issue of The Flyer. Morane Renault expects to have european certification of its JetA/diesel powered engines by the first quarter of 2000. They also hope to have US certification by the 2000 Oshkosh fly in(approximate 1 year from now).
Advantages:
Lower fuel burn--180 lycoming gas consumes 9-10 gallons per hour--their diesel will burn 5.0-5.1 gph
Lower fuel prices--Jet A is significantly less in cost than 100LL(depending upon where you live)
Engines will be quieter--max rpm of 2100 versus 2700-2800 for Lycoming and TCM motors
Fuel is cleaner--JetA contains no lead unlike 100LL
No plugs
No magnetos
3000 hour projected TBO versus 2000 max for almost all other engines
Vibration levels are reportedly less
Sigle lever power controls



[This message has been edited by N Dennis (edited July 31, 1999).]
 

gator

Well-known member
Joined
Jul 26, 1999
Location
Virginia, USA
I would think that a diesel engine would reduce the plane's noise significantly. The engine noise would be reduced due to the lower RPM. Also, with the prop spinning at lower speeds, the prop noise would be reduced even more. With the recent big push to limit airport noise pollution, that might one benefit that helps bring diesels to planes faster.
 
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