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Avgas vs Diesel


Aaaron16
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With all the challenges of Avgas, why are there hardly (or any?) piston helicopters using diesel?

 

Seems like diesel has a ton of advantages over 100LL, including efficiency, safety, availability, etc. Is it simply a weight problem?

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It has been done

http://en.wikipedia....t_diesel_engine

 

http://machinedesign...s-are-here-0619

 

Cesna is also developing a plane with a diesel engine (Cesna 182 NXT), do a google search, It seems to be the popular thing these days. Also, the 182 NXT burns jet-A in it's diesel engine and gets 30% better economy. Jet A/JP-8 is a mixture of kerosene and gasoline... Pretty much diesel fuel.

 

Sorry, the "add Link" is not working for me right now.

Edited by gary-mike
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Well, just read the most recent issues of both AOPA PILOT and FLYING Magazines (which you should all be reading anyway). They both did big write-ups on the plane Cessna is now calling the 182 JTA ("Jet-A" get it?). They took the big, ol' six-cylinder Continental out and stuck in a four-cylinder turbo-diesel of about the same horsepower. They saved some weight by using a composite propeller.

 

Could Robinson do the same - take the Lycoming 540 out and put in the new diesel that Cessna is using? Doubtful, as the weight penalty could not be countered so readily. But who knows? Stranger things have happened.

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Could Robinson do the same - take the Lycoming 540 out and put in the new diesel that Cessna is using? Doubtful, as the weight penalty could not be countered so readily. But who knows? Stranger things have happened.

 

The diesel question has come up every time I've been to Robinson. The simple answer is, tried that, couldn't make it work, that's why the R66 is a turbine!

 

If you can stick a turbine in a mosquito, why bother with diesel? Is the gas a lot cheaper, or something?

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Is the gas a lot cheaper, or something?

 

I'd say so.

 

Here in Prescott, AZ

Deisel: Average is $3.90 /gal

100LL: $6.12 /gal (Self serve is $5.62)

Jet-A: $5.99 /gal

 

In an R22 (10 gal/hr if I remember correctly) that's $61.20 per hour if you don't self serve. If it ran off deisel, $39.00. Savings of $21.20 per hour. Factor that across a month and you've saved hundreds on fuel.

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The diesel question has come up every time I've been to Robinson. The simple answer is, tried that, couldn't make it work, that's why the R66 is a turbine!

 

If you can stick a turbine in a mosquito, why bother with diesel? Is the gas a lot cheaper, or something?

 

Diesel Helicopter Coming Within 5 Years

 

The largest helicopter maker in the world has announced it is committed to developing a diesel-powered helicopter in the next five years. Eurocopter displayed an example of a possible diesel piston-engine design at the 2010 Heli-Expo in Houston. The company says the efficient powerplant could replace turbine engines in its light, single-engine helicopters.

 

Oliver Jouis is the head of environmental affairs at Eurocopter. He told Wired.com the European consortium will adapt a diesel powerplant for use in one of their smaller helicopters.“Diesel has reached a technology level that is transferable to the helicopter world,” he said.

 

Diesel engines have proven to be very successful in the auto industry over the past decade. Gone are the days of noisy, gutless, smoky motors. Today’s diesels are quiet, efficient and the power-to-weight ratio is so good, diesels are used in racing. Diesel-powered cars from Audi and Peugeot have dominated the 24 hours of LeMans in recent years.

 

A significant challenge facing Eurocopter is shaving enough weight from existing diesel engines. In aircraft, power-to-weight is at even more of a premium than in auto racing. But Jouis believes the same efficiency that makes diesels attractive for cars, is also attractive for helicopters.

 

“Specific fuel consumption is cut by 40 percent,” he said compared to existing turbine engines used in the company’s smaller helicopters. Currently all of Eurocopter’s helicopters are turbine-powered. Turbine engines are incredibly reliable and provide a large amount of power for the weight of the motor. But they are also quite thirsty for fuel. The cost of fuel for a small helicopter can run several hundred dollars per hour. Any reduction is obviously welcome news to helicopter operators.

 

Eurocopter has said its EC120 would be a likely candidate for the diesel engine. Currently, the helicopter is powered by Turbomeca Arrius turbine engine.

 

“The second advantage for the helicopter is the diesel offers better performance at high altitude,” Jouis said. Turbine engines used in helicopters lose efficiency rapidly as the altitude increases. Because of the power loss at altitude, helicopter operators that often fly in the mountains use helicopters with more powerful engines to compensate. Larger engines are even thirstier engines, increasing an already large fuel bill.

 

The diesel engines Eurocopter is investigating would be turbocharged. The use of a turbochargeer results in an aircraft being able to maintain full power to a higher altitude where the air is thinner. This “turbo normalizing” doesn’t necessarily mean a boost of power at lower altitudes. Instead, the boost from the turbocharger is used to compensate for thinning air as the helicopter is flown at higher altitudes. Gasoline-powered piston helicopters have long used turbocharged engines for the same reasons.

 

Jouis said the company has not yet announced what kind of diesel engine it will choose. He said the company will not be getting into the engine manufacturing business, but will instead work with an existing manufacturer to develop the diesel powerplant. Jouis said they are currently in talks with engine makers, including car companies with diesel experience. Another advantage to the diesel according to Jouis would be lower acquisition costs compared to turbine engines.

 

The company displayed two-stroke diesel engine at the Heli-Expo. The multifuel engine is made by U.S.-based EcoMotors International. The interesting design uses two opposed pistons per cylinder. This arrangement generates one power stroke with every revolution of the crank for each cylinder. Jouis said the company is also looking at several other options, including more traditional four-stroke diesels.

 

All of the engines still need a lot of weight shaving, “we are nowhere near the power-to-weight ratio of a turbine,” Jouis said. “But we can see there is a solution [for diesel power].”

Eurocopter is not setting a timeline for the introduction of a diesel-powered helicopter to the marketplace, but Jouis said he expects one to at least make a first flight within the next five years.

 

http://youtu.be/buX89nlww2E

Edited by iChris
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That is a really cool idea. I'm really excited to see the progression of engines and potential alternate fuels and how they will be used in aviation. With the advancement of batteries maybe we'll see an electric helicopter?

 

I was watching an AOPA show (albeit half asleep) and they were talking about completely overhauling the certification process for new aircraft and technology. They were saying on a typical GA aircraft, this initially adds $100,000-$200,000 to the price tag and I would imagine a considerable amount of time. Maybe these things will combine, and we'll have some newer engine technology sooner than we think? I can stay hopeful :lol:

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Weight, weight, weight. Its all about the weight.

 

I have a I-6 cummins in my dodge, it weighs in over 900#'s. I have been trying to put the 4 cyl version (cummins 4bt) in my jeep wrangler for years, but it too weighs 800# + with turbo, etc. Not that great for a rock crawler.

 

Diesels need to be heavy to accommodate the high amounts of compression produced. This results in higher torque. Having a large and heavy flywheel also helps keep the torque flowing. I imagine that torque would be very valuable in a heli, keeping rotor rpms from falling. But, how would you replace that heavy flywheel with something comparable but lighter?

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Diesel and AVGAS aren't too far off in the grand scheme of things. Most helicopters setup for JET 100, JP8, JP4 etc can also run AVGAS if absolutely necessary. I could see engineers being able to make the engine inherently more efficient and capable of using whatever.

 

As long as it can burn it consistently we should survive.

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A Turbine will burn about anything, the fuel control should be adjusted for it though. I would imagine running AVGAS in a turbine would really shorten the life of the turbine wheel.

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I use to burn Jet A in my VW Jetta 1991 diesel. The car ran fine on it, But that engine would never hold up at the continuous power out put you would need even in a light helicopter like an R-22. The Main problem with Avgas 100LL is that the EPA wants it gone, but there is no replacement for it at present that will work. Thus you will have a large number of aircraft being grounded because of it, or you can go to Rolls Royce, they have an engine that will replace the IO-540 series. You will just have to write a check for around 500K. There is nothing wrong with 100LL, you all complain about the costs to learn to and to just fly well, the costs are going to go up even more if the EPA gets its way in this, and they will. Aviation is having a very tough time of it, and the times are going to get a lot tougher. Never mind the damage to the economy that this move will do, but they could care less about that. Flying represents freedom and they don't like it.

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I HIGHLY doubt that the EPA dislikes the freedom aspect of flying. The question here is what kind of emissions regulations govern the aviation world? To my extremely limited knowledge on the subject: None. The pollution produced is what the EPA wants to cut down on, not the freedom. To think otherwise is pretty narrow sighted.

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There are some cleaner burning turbo fan engines used on large passenger jets, that can run on a type of bio diesel jet fuel instead of your everyday Jet A. The problem with avgas, is I don't think there many alternatives for gasoline based fuels. We have E85, that is a cleaner burning ethanol corn based fuel, but because of the stoichiometry and lack combustable energy in the fuel compared to gasoline, more of it is used. So if you burn more of a cleaner fuel, is there really much benefit there?

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