Death of the Diesel?
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Death of the Diesel?
The European finance ministers have asked the European Commission to look into raising a tax on aviation fuel (JetA1). Apparently the idea was brought up by the UK at a recent meeting of the G7!
If the tax came in it would remove the advantage in price and interest in JetA1 powered light aircraft will drop significantly. In the US there is very little interest as the price difference is not large.
Rod1
If the tax came in it would remove the advantage in price and interest in JetA1 powered light aircraft will drop significantly. In the US there is very little interest as the price difference is not large.
Rod1
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But diesels are so much more efficient, so they still have a distinct advantage. The recent Diamond TwinStar non-stop crossing of the Atlantic provides some evidence to support this.
http://www.avweb.com/newswire/10_35a.../187987-1.html
Anyway, I doubt jet fuel will be taxed to the same degree as 'lesuire' fuel. Also, to me, this was inevitible.
http://www.avweb.com/newswire/10_35a.../187987-1.html
Anyway, I doubt jet fuel will be taxed to the same degree as 'lesuire' fuel. Also, to me, this was inevitible.
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Plus the advantages of no mixture control (just a "power" lever, which varies the amount of fuel injected) and no chance of carb ice. Not forgetting - no magnetos either.
Still the way forward.
Still the way forward.
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Does a diesel engine provide a lot more range per kg of fuel carried? I don't know, but it's a question worth asking. The fuel has a different SG, IIRC.
A 30% gain (if it is that) in range isn't worth paying the huge retrofit fee for, given that some SEPs can already do 10hrs endurance at best-range power. Neither would be a 30% gain in flow rate for a given IAS.
The DA42 making it across the Atlantic West to East doesn't in itself mean a lot because a) it is a very aero-efficient design; b) there is no petrol version to compare with; c) they must have had good tailwind
FADEC and turbos can be equally applied to a petrol engine.
I do think this will limit the diesel market to new aircraft; in effect it will kill it off because new aircraft sales are very low.
The real question is how the EU is going to get around their treaty obligations for tax free jet fuel.
I've heard it mentioned that some EU states provide tax free jet fuel only to AOC holders. That is an obvious anti-private flying discrimination measure which is likely to raise very little money for the foreseeable future, but it's one way.
A 30% gain (if it is that) in range isn't worth paying the huge retrofit fee for, given that some SEPs can already do 10hrs endurance at best-range power. Neither would be a 30% gain in flow rate for a given IAS.
The DA42 making it across the Atlantic West to East doesn't in itself mean a lot because a) it is a very aero-efficient design; b) there is no petrol version to compare with; c) they must have had good tailwind
FADEC and turbos can be equally applied to a petrol engine.
I do think this will limit the diesel market to new aircraft; in effect it will kill it off because new aircraft sales are very low.
The real question is how the EU is going to get around their treaty obligations for tax free jet fuel.
I've heard it mentioned that some EU states provide tax free jet fuel only to AOC holders. That is an obvious anti-private flying discrimination measure which is likely to raise very little money for the foreseeable future, but it's one way.
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I agree about the retrofit dilemma, but today's old aircraft won't be around indefinitely. Certainly most of the ones I learned on have gone to the scrapheap......
However, the future of AVGAS as a viable fuel isn't certain either. As it is seen as environmentally bad, it may be phased out altogether or made even more expensive. Even today, not every airport stocks it and then the range problem has another significant factor in the equation - a pilot may have to go well off a straight line track to find his next tankful.
Less than twenty years ago people said that diesel powered cars would never catch on in any great numbers - but look what's happened.
I'll guess that AVGAS has another twenty years at most.
However, the future of AVGAS as a viable fuel isn't certain either. As it is seen as environmentally bad, it may be phased out altogether or made even more expensive. Even today, not every airport stocks it and then the range problem has another significant factor in the equation - a pilot may have to go well off a straight line track to find his next tankful.
Less than twenty years ago people said that diesel powered cars would never catch on in any great numbers - but look what's happened.
I'll guess that AVGAS has another twenty years at most.
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Shy Torque is right.
Avgas is rare in Africa aparrently.
Had a talk at the Oxford PFA a year ago about avgas, very interesting. One point made was that there is only one manufacturer of Tetra-Ethyl-Lead in Europe.
In my opinion diesels are better for several reasons. Fuel is safer, engines are more efficient, engines are more reliable( no ignition and no carb ) and the normal diesel power curve fits a propellor application superbly.
Mike W
Avgas is rare in Africa aparrently.
Had a talk at the Oxford PFA a year ago about avgas, very interesting. One point made was that there is only one manufacturer of Tetra-Ethyl-Lead in Europe.
In my opinion diesels are better for several reasons. Fuel is safer, engines are more efficient, engines are more reliable( no ignition and no carb ) and the normal diesel power curve fits a propellor application superbly.
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Having been involved with a group where we looked at a diesel aircraft last year, I was quite surprised to learn that the Thielert diesel was on a total replacement periodicity of 1000 hrs. I just checked the Centurion Thielert web site and I could find no easy reference to this and there was just a Maintenance Data Sheet showing a 1000 hr inspection.
On another part of their Web Site, it states 'The entire aircraft engine TAE 125-01 has a proved lifetime of 1000 flight hours or 12 years whichever occurs first. For safety reasons it is strongly recommended to replace the entire aircraft engine after 1000 flight hours or after 12 years whichever occurs first.'
I don't know the current CAA certification status, as I know Thielert were working to increase the TBR to 2000 hrs. The replacement is pretty well everything forward f the firewall (including wiring looms, ancillaries, etc).
On another part of their Web Site, it states 'The entire aircraft engine TAE 125-01 has a proved lifetime of 1000 flight hours or 12 years whichever occurs first. For safety reasons it is strongly recommended to replace the entire aircraft engine after 1000 flight hours or after 12 years whichever occurs first.'
I don't know the current CAA certification status, as I know Thielert were working to increase the TBR to 2000 hrs. The replacement is pretty well everything forward f the firewall (including wiring looms, ancillaries, etc).
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As far as I am aware diesel engines have a lesser power-weight ration than gasoline engines.
Turbo and injection can equally be applied to gasoline engines.
Gasoline engines have a long proven record as light aircraft power-plants.
The reason for developing diesel as a light aircraft power plant appears to be to take advantage of tax breaks on fuel - not a good safety reason.
Mike
Turbo and injection can equally be applied to gasoline engines.
Gasoline engines have a long proven record as light aircraft power-plants.
The reason for developing diesel as a light aircraft power plant appears to be to take advantage of tax breaks on fuel - not a good safety reason.
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I would always rather have a diesel or turbine engine in an a/c rather than a rotten old piece of 30's technology.
Mike just to make a point, in the event of an accident where a fuel line or tank is ruptured, which is more likely to combust, Dielsel or petrol? In an accident, I'd rather have pools of diesel than petrol any day of the week (not that I would like to see either of course!)
So as safety goes, there is a case for a diesel engine.
Petrol engines have got a long record for powering light a/c, but that is more down to the fact that there has been no alternative rather than their inherent suitability for the task.
If Lycoming or Continental had put some effort into developing their ancient products, then we might have some competition between the Diesels and petrol engines. As it is, eventually Avgas will be wiped away due to it's cost, current environmental impact and the reducing availability of the stuff.
It is inevitable that Diesels/Avtur powered engines will overtake their Avgas rivals, it is just a matter of time.
Mike just to make a point, in the event of an accident where a fuel line or tank is ruptured, which is more likely to combust, Dielsel or petrol? In an accident, I'd rather have pools of diesel than petrol any day of the week (not that I would like to see either of course!)
So as safety goes, there is a case for a diesel engine.
Petrol engines have got a long record for powering light a/c, but that is more down to the fact that there has been no alternative rather than their inherent suitability for the task.
If Lycoming or Continental had put some effort into developing their ancient products, then we might have some competition between the Diesels and petrol engines. As it is, eventually Avgas will be wiped away due to it's cost, current environmental impact and the reducing availability of the stuff.
It is inevitable that Diesels/Avtur powered engines will overtake their Avgas rivals, it is just a matter of time.
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All the arguments against diesel engines also applied to the increasing number of road vehicles so powered...... but the case FOR diesels is becoming overwhelming.
In my youth, diesels were noisy, smelly, sluggish things that were only fit for lorries and railway locomotives. However, once the road-going diesel engine was given more research and development, because the market had accepted it as a concept, the output and sophistication increased markedly. There is absolutely no doubt that the type has become very widely accepted, even though in UK the road fuel is actually MORE expensive than petrol.
A diesel can run on a wide range of fuels, all of them cheaper to produce than petrol. A spark ignition / petrol engine needs a very specialised fuel quality to make it work, especially in the relatively large cylinders required for aero engines. Without such a high octane fuel, the power output has to be reduced. If the use of tetra-ethyl lead is completely banned (there is speculation that it might be), it would quickly signal the end of the line for the petrol aviation engine as we know it because there is no viable replacement suitable for aero engines.
Having read the preceding posts, one thing that perhaps needs clarification - modern aero diesels run on Jet-A1, NOT the diesel fuel (DERV) used by road-going vehicles. This means that the fuel is already very widely available at aviation oulets.
I speak as a self-declared petrol head, definitely one who doesn't enjoy driving diesel cars. However, if I was in a position to choose a brand new light aircraft, it would definitely have a diesel powerplant.
In my youth, diesels were noisy, smelly, sluggish things that were only fit for lorries and railway locomotives. However, once the road-going diesel engine was given more research and development, because the market had accepted it as a concept, the output and sophistication increased markedly. There is absolutely no doubt that the type has become very widely accepted, even though in UK the road fuel is actually MORE expensive than petrol.
A diesel can run on a wide range of fuels, all of them cheaper to produce than petrol. A spark ignition / petrol engine needs a very specialised fuel quality to make it work, especially in the relatively large cylinders required for aero engines. Without such a high octane fuel, the power output has to be reduced. If the use of tetra-ethyl lead is completely banned (there is speculation that it might be), it would quickly signal the end of the line for the petrol aviation engine as we know it because there is no viable replacement suitable for aero engines.
Having read the preceding posts, one thing that perhaps needs clarification - modern aero diesels run on Jet-A1, NOT the diesel fuel (DERV) used by road-going vehicles. This means that the fuel is already very widely available at aviation oulets.
I speak as a self-declared petrol head, definitely one who doesn't enjoy driving diesel cars. However, if I was in a position to choose a brand new light aircraft, it would definitely have a diesel powerplant.
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“end of the line for the petrol aviation engine as we know it because there is no viable replacement suitable for aero engines”
I think Rotax, the largest European aero engine manufacturer, would disagree with you! Their 4 stroke specific aircraft designed engines are based around Mogas, which is the obvious alternative to Avgas for most of GA. Almost non of the small airfields I visit have JetA1, but some have mogas by PPR. A modern Rotax engine has most of the advantages of a Diesel, but with much less weight. Weight is a problem in a car, but it is a huge problem in an aircraft. It is only in comparison with 1930’s engines that modern diesels can compete on weight, a modern mogas engine like a Rotax will win every time unless there is a big difference in the cost of the fuel.
Rod1
I think Rotax, the largest European aero engine manufacturer, would disagree with you! Their 4 stroke specific aircraft designed engines are based around Mogas, which is the obvious alternative to Avgas for most of GA. Almost non of the small airfields I visit have JetA1, but some have mogas by PPR. A modern Rotax engine has most of the advantages of a Diesel, but with much less weight. Weight is a problem in a car, but it is a huge problem in an aircraft. It is only in comparison with 1930’s engines that modern diesels can compete on weight, a modern mogas engine like a Rotax will win every time unless there is a big difference in the cost of the fuel.
Rod1
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I know the sound argument for small engines like the Rotax but MOGAS is not such a viable proposition for higher performance aircraft that operate at altitude, nor allowed for commercial operations or in twins.
There are obviously other known safety concerns with the use of MOGAS, such as an increased likelihood of carb icing and fuel vapour lock at high ambient temperature.
There are obviously other known safety concerns with the use of MOGAS, such as an increased likelihood of carb icing and fuel vapour lock at high ambient temperature.
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Mogas isn't a viable solution to the problem. Look at the extreme reluctance of the regulators to it's use.
A diesel or to be more correct a compression ignition engine will always be at a disadvantage when the argument is purely about power to weight ratios, but how about a power to torque ratio, that is probably more important.
One argument is, that due to the increased efficiency of a Diesel is that you can reduce the amount of fuel you have to carry for a certain sector, therefore the difference in TOW between an Avgas or Avtur powered a/c would be reduced.
To me, reliability is still the most important issue in aviation and lets face it, a Diesel is inherently a more reliable powerplant than any petrol engine.
Bring 'em on I say.
A diesel or to be more correct a compression ignition engine will always be at a disadvantage when the argument is purely about power to weight ratios, but how about a power to torque ratio, that is probably more important.
One argument is, that due to the increased efficiency of a Diesel is that you can reduce the amount of fuel you have to carry for a certain sector, therefore the difference in TOW between an Avgas or Avtur powered a/c would be reduced.
To me, reliability is still the most important issue in aviation and lets face it, a Diesel is inherently a more reliable powerplant than any petrol engine.
Bring 'em on I say.
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Shy torque
I really really wish you were right. I wish that the whole of the present-day c. 1970 fleet was scrapped and made way for modern designs, composite, aerodynamically efficient and with modern navigation kit. GA could then move forward into the 20th century (let's not be too ambitious )
But the money to replace it just isn't there. The desire to do so isn't there either, because GA is packed with people who see nothing wrong with these old heaps.
There is a virtually limitless supply of old Cessna/Piper heaps in the USA; plenty to keep Europe going for decades.
There is no indication that new aircraft sales will take off anytime soon. This means the diesel market is going to remain mostly retrofit, and the figures for that don't add up unless one is doing hundreds of hours a year.
If the tax break was taken away, the figures would not add up in any GA situation I can imagine, which is why there is next to zero interest in diesels in the USA.
Avgas will go away eventually but it's going to create a huge upheaval when it does. It will be like mandatory Mode S transponders but 20 times worse, and that's assuming that a usefully reliable diesel has been developed by then. Nobody has done it yet, certainly not Thielert. I hope somebody does it before it's too late.
SAS
I think that's a misconception. Power = torque x RPM.
You can get an engine to deliver lots of torque at a low RPM but it will be big, with big cylinders. It won't be able to rev high because the big heavy parts won't have the strength. So you end up with a Lycoming-type engine. A diesel doesn't in itself deliver higher torque than a petrol engine.
today's old aircraft won't be around indefinitely
)But the money to replace it just isn't there. The desire to do so isn't there either, because GA is packed with people who see nothing wrong with these old heaps.
There is a virtually limitless supply of old Cessna/Piper heaps in the USA; plenty to keep Europe going for decades.
There is no indication that new aircraft sales will take off anytime soon. This means the diesel market is going to remain mostly retrofit, and the figures for that don't add up unless one is doing hundreds of hours a year.
If the tax break was taken away, the figures would not add up in any GA situation I can imagine, which is why there is next to zero interest in diesels in the USA.
Avgas will go away eventually but it's going to create a huge upheaval when it does. It will be like mandatory Mode S transponders but 20 times worse, and that's assuming that a usefully reliable diesel has been developed by then. Nobody has done it yet, certainly not Thielert. I hope somebody does it before it's too late.
SAS
how about a power to torque ratio
You can get an engine to deliver lots of torque at a low RPM but it will be big, with big cylinders. It won't be able to rev high because the big heavy parts won't have the strength. So you end up with a Lycoming-type engine. A diesel doesn't in itself deliver higher torque than a petrol engine.
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Say again slowly
Your argument about being able to carry less fuel due to diesels being more efficient doesnt stack up. You are not taking account of the fact that Avtur is 12% heavier than Avgas.
Apart from that....I look forward to the day when a 300HP Diesel is available
Your argument about being able to carry less fuel due to diesels being more efficient doesnt stack up. You are not taking account of the fact that Avtur is 12% heavier than Avgas.
Apart from that....I look forward to the day when a 300HP Diesel is available
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So basically IO you are saying that power is a made up figure from torque and engine speed!
Torque is basicall turning force, what is an engine trying to do? Turn a prop. To my eyes is it just as if not more relevant than power.
O.K so Avtur is 12% heavier, how much more efficient are Diesels than Petrol engines? If it is more than 12 % then the argument is valid, if minor. Though it is a point worth noting.
Actually, I think I meant to type a weight to torque ratio rather than a torque to power ratio!
Torque is basicall turning force, what is an engine trying to do? Turn a prop. To my eyes is it just as if not more relevant than power.
O.K so Avtur is 12% heavier, how much more efficient are Diesels than Petrol engines? If it is more than 12 % then the argument is valid, if minor. Though it is a point worth noting.
Actually, I think I meant to type a weight to torque ratio rather than a torque to power ratio!
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A diesel doesn't in itself deliver higher torque than a petrol engine.
Does that sound right?
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The European union are also looking to triple the tax on Red diesel for motorboats. when will tony Blair take charge of his own country and stop being bossed around by others.
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Torque:
The 2 litre diesel engine in my car produces 50% more torque at significantly lower revs than the 2 litre petrol engine.
D=330 nm at 2000 rpm versus P=210nm at 3500rpm.
So you don't need a larger diesel than petrol to produce torque which is the most important element of driving a propeller.
The 2 litre diesel engine in my car produces 50% more torque at significantly lower revs than the 2 litre petrol engine.
D=330 nm at 2000 rpm versus P=210nm at 3500rpm.
So you don't need a larger diesel than petrol to produce torque which is the most important element of driving a propeller.