Aero Diesels
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I was concentrating on private owners/groups.
I was not thinking of a JetA1 engine, more a Rotax powered machine. The Rotax is much cheaper than the JetAt burner and is tried and tested but still much more modern than the old Avgas burners.
In my UK touring over 80% of the airfields I visit do not have JetA1, but 90% have Avgas, or increasingly Mogas. With the UK applying to Europe to remove the tax exemption on JetA1 Europe wide, it is likely the cheap fuel will vanish in three to four years. When this happens, if the manufacturers have not achieved critical mass on the number of installations we may see some big problems.
Your PA28 is comprehensively out performed by a modern VLA. The VLA would be new, against 40 years old airframe and it has a long term future. I have just returned from a week long tour of France, two up. My MCR averaged 121kn w to w, airborne in 300m, climbed at 900 fpm at MAUW in 30c heat and burned 18.5 lph. Cruse speed was 128kn point to point with handling and visibility which makes a PA28 look like a Ford Anglia against a modern sports car. Remember we are talking about a fixed gear, fixed pitch machine which will cost me about £500 per year to maintain. Still want a two seat PA28?
Rod1
I was not thinking of a JetA1 engine, more a Rotax powered machine. The Rotax is much cheaper than the JetAt burner and is tried and tested but still much more modern than the old Avgas burners.
In my UK touring over 80% of the airfields I visit do not have JetA1, but 90% have Avgas, or increasingly Mogas. With the UK applying to Europe to remove the tax exemption on JetA1 Europe wide, it is likely the cheap fuel will vanish in three to four years. When this happens, if the manufacturers have not achieved critical mass on the number of installations we may see some big problems.
Your PA28 is comprehensively out performed by a modern VLA. The VLA would be new, against 40 years old airframe and it has a long term future. I have just returned from a week long tour of France, two up. My MCR averaged 121kn w to w, airborne in 300m, climbed at 900 fpm at MAUW in 30c heat and burned 18.5 lph. Cruse speed was 128kn point to point with handling and visibility which makes a PA28 look like a Ford Anglia against a modern sports car. Remember we are talking about a fixed gear, fixed pitch machine which will cost me about £500 per year to maintain. Still want a two seat PA28?
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Skyjock
You would praise Thielerts and SMAs wouldn't you seeing as you're trying to flog conversions froma certain Oxfordshire based airfield....!!
The 'diesel' GA revolution will only take place when the Americans recognise them as powerplants for things smaller than a 42 wheeled truck.
You would praise Thielerts and SMAs wouldn't you seeing as you're trying to flog conversions froma certain Oxfordshire based airfield....!!
The 'diesel' GA revolution will only take place when the Americans recognise them as powerplants for things smaller than a 42 wheeled truck.
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The problem, rod1, is that the market is probably a lot more complicated than any of us think.
If you think that a £500 annual cost is a significant thing, then you won't be in the market for anything that costs "real money". The annual fuel costs of anybody doing a reasonable amount of flying will be far more than this saving.
In cruise, a Rotax will not deliver more HP per given fuel flow than a properly operated old Lyco - the power comes solely from burning fuel and once you are at peak EGT, or even LOP, there is nothing more to gain.
The tax exemption is another funny one. Currently, anybody with an AOC can get tax free avgas in most places in Europe - though not in the UK as far as I know, well not below a certain weight perhaps. So, the case for avtur in pistons is much diminished for any commercial operation whose fuel usage makes it worth applying for an AOC just for this reason alone - even if they never make any use of the AOC itself. In Spain, it's even easier... any business customer can get tax free avgas, so a PPL school based in Spain has a big price advantage straight away.
The reliability of any piston, especially a Rotax (based on past history), does not even begin to compare with a turbine. And the old Lycos are actually very reliable; the big ones need proper management to get to TBO but the things rarely fall apart.
These are just random factors I can think of.
I do think it is stupid for diesel designers to not match the existing power output. Mind you, did you see the latest Loop magazine? There is an advert in there for a new diesel whose size and mounting points are identical to the old Lyco - now that's interesting. Don't recall the HP but at least somebody is waking up to the fact that at a retrofit cost of say £50k there will be very few takers.
If you think that a £500 annual cost is a significant thing, then you won't be in the market for anything that costs "real money". The annual fuel costs of anybody doing a reasonable amount of flying will be far more than this saving.
In cruise, a Rotax will not deliver more HP per given fuel flow than a properly operated old Lyco - the power comes solely from burning fuel and once you are at peak EGT, or even LOP, there is nothing more to gain.
The tax exemption is another funny one. Currently, anybody with an AOC can get tax free avgas in most places in Europe - though not in the UK as far as I know, well not below a certain weight perhaps. So, the case for avtur in pistons is much diminished for any commercial operation whose fuel usage makes it worth applying for an AOC just for this reason alone - even if they never make any use of the AOC itself. In Spain, it's even easier... any business customer can get tax free avgas, so a PPL school based in Spain has a big price advantage straight away.
The reliability of any piston, especially a Rotax (based on past history), does not even begin to compare with a turbine. And the old Lycos are actually very reliable; the big ones need proper management to get to TBO but the things rarely fall apart.
These are just random factors I can think of.
I do think it is stupid for diesel designers to not match the existing power output. Mind you, did you see the latest Loop magazine? There is an advert in there for a new diesel whose size and mounting points are identical to the old Lyco - now that's interesting. Don't recall the HP but at least somebody is waking up to the fact that at a retrofit cost of say £50k there will be very few takers.
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Hi everybody! :-)
We have a C172N with a Thielert in our club. Comparing to our other Cessna, a 150hp C172M, I would say the performance is more or less the same. I don't remember the exact figures offhand, but the takeoff distances are not really significantly better or worse. Of course if you have a 160hp or even a 180, then it is a bigger difference.
Sure, neither of our planes are particular hotrods or real four-seaters, that's a fact. With 3 on board the diesel is still a very nice flying club plane with good range. But what made the real difference for us is the 30-40 euros per hour difference in fuel cost. That is very important for us, as to keep flying at least remotely reasonably priced and thus maintaining enough hours annually to keep the fixed costs down per hour.
The engine weighs 30kg more than the 150hp O-320, and kerosene is a bit heavier than avgas, so one loses some payload with full tanks, but like mentioned earlier, that would be about 7 hours plus endurance depending on the power setting on cruise. Comparing with four hours of fuel on board should even gain a bit over the avgas plane.
We've had the plane with thielert for 1.5 years now and put in some 600 flight hours during that time without any real problems, and have been happy with it. Of course the sticky smell of diesel that emits from the pilots and the plane could be a problem for someone
Does anyone know what kind of problems Cabair has had with their Diamonds? Powerplant, airframe or combining-the-two -related? Some of this could well be related also to mainteinance organizations having a new gizmo to play with, after maintaining a fleet of Lycomings for the last half decade..?
We have a C172N with a Thielert in our club. Comparing to our other Cessna, a 150hp C172M, I would say the performance is more or less the same. I don't remember the exact figures offhand, but the takeoff distances are not really significantly better or worse. Of course if you have a 160hp or even a 180, then it is a bigger difference.
Sure, neither of our planes are particular hotrods or real four-seaters, that's a fact. With 3 on board the diesel is still a very nice flying club plane with good range. But what made the real difference for us is the 30-40 euros per hour difference in fuel cost. That is very important for us, as to keep flying at least remotely reasonably priced and thus maintaining enough hours annually to keep the fixed costs down per hour.
The engine weighs 30kg more than the 150hp O-320, and kerosene is a bit heavier than avgas, so one loses some payload with full tanks, but like mentioned earlier, that would be about 7 hours plus endurance depending on the power setting on cruise. Comparing with four hours of fuel on board should even gain a bit over the avgas plane.
We've had the plane with thielert for 1.5 years now and put in some 600 flight hours during that time without any real problems, and have been happy with it. Of course the sticky smell of diesel that emits from the pilots and the plane could be a problem for someone
Does anyone know what kind of problems Cabair has had with their Diamonds? Powerplant, airframe or combining-the-two -related? Some of this could well be related also to mainteinance organizations having a new gizmo to play with, after maintaining a fleet of Lycomings for the last half decade..?
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Pretty much all the problems I've heard the Diamonds have had, are to do with the engine and specifically the FADEC.
The airframes seem to be fairly good, their construction is pretty simple and any potential problems would more likely to be catastrophic rather than minor issues.
The thielert engine has had many problems that have always been explained away as ancillary issues, but I don't consider this to be a true picture. If the FADEC has a fit and goes to get home mode at low power, then you have an engine problem end of story.
There have been occasions of poor knowledge on the part of pilots when failures have occured, ie over-reaction to warnings, but there was certainly an issue with some of the major components such as wastegates, turbo's and the gearbox. These will I'm sure have been corrected now, but it will take a fair while before I feel totally comfortable spending vast amounts of cash on conversions for our machines.
The issue of the potential ending of VAT free AVTUR, would be a deathknell for engines such as these, without the financial benefits, there is no reason to change. Especially as performance is compromised.
When these issues are sorted, then flying schools will start thinking about converting, but until then it just isn't worth the risk.
The airframes seem to be fairly good, their construction is pretty simple and any potential problems would more likely to be catastrophic rather than minor issues.
The thielert engine has had many problems that have always been explained away as ancillary issues, but I don't consider this to be a true picture. If the FADEC has a fit and goes to get home mode at low power, then you have an engine problem end of story.
There have been occasions of poor knowledge on the part of pilots when failures have occured, ie over-reaction to warnings, but there was certainly an issue with some of the major components such as wastegates, turbo's and the gearbox. These will I'm sure have been corrected now, but it will take a fair while before I feel totally comfortable spending vast amounts of cash on conversions for our machines.
The issue of the potential ending of VAT free AVTUR, would be a deathknell for engines such as these, without the financial benefits, there is no reason to change. Especially as performance is compromised.
When these issues are sorted, then flying schools will start thinking about converting, but until then it just isn't worth the risk.
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Originally Posted by Say again s l o w l y
The issue of the potential ending of VAT free AVTUR, would be a deathknell for engines such as these, without the financial benefits, there is no reason to change. Especially as performance is compromised.
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The thing is, it's very easy to go from 43lph to 18.5lph. It is called a smaller (particularly in the cockpit frontal section) lighter and slower aeroplane.
The above is only partly tongue in cheek. Composite airframes, properly designed for aerodynamics, will definitely help. But a lot less than most people would believe.
Especially as the difference between operating LOP, and operating the way every UK PPL has been taught, is about 30% in fuel flow rate.
It's all a tradeoff. If I lost my IFR privileges then I would most likely go for a top-end PFA type right away, fit it with the best IFR avionics, a TKS prop, and would be more than happy with the performance.
I suspect a significant chunk of the efficiency of a DA40 comes from its glider-like low wing loading, which will make it tough to hold in turbulence.
The above is only partly tongue in cheek. Composite airframes, properly designed for aerodynamics, will definitely help. But a lot less than most people would believe.
Especially as the difference between operating LOP, and operating the way every UK PPL has been taught, is about 30% in fuel flow rate.
It's all a tradeoff. If I lost my IFR privileges then I would most likely go for a top-end PFA type right away, fit it with the best IFR avionics, a TKS prop, and would be more than happy with the performance.
I suspect a significant chunk of the efficiency of a DA40 comes from its glider-like low wing loading, which will make it tough to hold in turbulence.
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Diesels
Very interesting discussion. Seems like I stirred up a real hornets nest. Some good points though. Rod 1, the IFR ability of the PTCoA is attractive over the Permit a/c although I do acknowledge that the more recent VLAs are very potent in terms of cruise speed and fuel burn.
With respect to adding VAT to Avtur, I'd do the calculations again Sayagainslowly. The discussion within the European Commission is to remove the VAT exemption not to levy UK fuel duty. So the most that would be added is 17% (of course that is not to say that the dour presbetarian of a future Prime Minister would not add fuel duty in the future), but the cost would increase to say between 50p and 60p/lt. Since I'm paying around £1.50/lt at present, I'd say the saving is worth considering.
Current fuel burn 40-45 l/hr @ £1.54 - £60-£70/hr
Diesel equivalent 25 lt/hr @50-60p - £12.50-£15/hr
Not saying diesels are for everyone, but the thread has certainly given me food for thought
With respect to adding VAT to Avtur, I'd do the calculations again Sayagainslowly. The discussion within the European Commission is to remove the VAT exemption not to levy UK fuel duty. So the most that would be added is 17% (of course that is not to say that the dour presbetarian of a future Prime Minister would not add fuel duty in the future), but the cost would increase to say between 50p and 60p/lt. Since I'm paying around £1.50/lt at present, I'd say the saving is worth considering.
Current fuel burn 40-45 l/hr @ £1.54 - £60-£70/hr
Diesel equivalent 25 lt/hr @50-60p - £12.50-£15/hr
Not saying diesels are for everyone, but the thread has certainly given me food for thought
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Surely anybody who is VAT registered (most schools I guess) will be able to claim back VAT, so this will affect private owners only.
Also if you use the plane for business travel, you can get the business to buy the fuel used on the business flights, and if the business is VAT registered it can get the VAT back on the fuel. The business can incidentally also pay for the appropriate percentage of the total maintenance costs, and get the VAT back on those. This is from my accountant, as of yesterday.
Everything else being equal (which it isn't) I would prefer avtur over avgas simply because of much better availability when looking at the international airfield/airport scene as a whole. However, on farm strips it is likely to be very much the other way round.
Also if you use the plane for business travel, you can get the business to buy the fuel used on the business flights, and if the business is VAT registered it can get the VAT back on the fuel. The business can incidentally also pay for the appropriate percentage of the total maintenance costs, and get the VAT back on those. This is from my accountant, as of yesterday.
Everything else being equal (which it isn't) I would prefer avtur over avgas simply because of much better availability when looking at the international airfield/airport scene as a whole. However, on farm strips it is likely to be very much the other way round.
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“Everything else being equal (which it isn't) I would prefer avtur over avgas simply because of much better availability when looking at the international airfield/airport scene as a whole. However, on farm strips it is likely to be very much the other way round.”
Most a/g licensed airfields have avgas, a significant number do not have Jet A1, some, like Sywell, are offering Mogas. To refer to such as farm strips is not very fair!
Most Micro strips will supply Mogas in cans if you ask in advance.
Most Farm strips do not have anything, but might have a petrol station near by.
You can buy Mogas on the way to the airfield (as I do)
The Problem with the JetA1 burners is you cannot use Diesel, so if you have no JetA1 at home base you will probably have a very long drive to get some from a licensed airfield.
At most French CCI airfields it is possible to get Avgas via the flying club out of hours (including diner time), but getting JetA1 is much harder.
Rod1
Most a/g licensed airfields have avgas, a significant number do not have Jet A1, some, like Sywell, are offering Mogas. To refer to such as farm strips is not very fair!
Most Micro strips will supply Mogas in cans if you ask in advance.
Most Farm strips do not have anything, but might have a petrol station near by.
You can buy Mogas on the way to the airfield (as I do)
The Problem with the JetA1 burners is you cannot use Diesel, so if you have no JetA1 at home base you will probably have a very long drive to get some from a licensed airfield.
At most French CCI airfields it is possible to get Avgas via the flying club out of hours (including diner time), but getting JetA1 is much harder.
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AVTUR at my local field is 60p/L and I can easily see there being both duty and VAT added to it at some point (currently there is 5% VAT on it). The sop to the airlines would be that if you have an AOC you would be exempt.
I can forsee this as most governments see GA as a rich man's hobby.
We currently pay £1.34 litre for AVGAS.
For example our PA 28 averages around 34 l/hr so costs us £45.56/hr or over an engine life of 2000 hrs : £91120 for fuel, add in the cost of the engine in the first place (approx £18K) gives a total life cost (not including servicing and oil) of £109120. This is however a 181 Archer II, with performance that leaves a diesel machine for dead.
A Diesel conversion costs in the region of £50K with costs of approx 63p/l and with an assumption of a burn around 25 l/hr giving a cost of £15.75/hr for fuel.
Again assuming a 2000hr TBR you are looking at a cost over the life of that engine (excluding maintenance and oil etc.) of £81500.
A significant saving yes, but as I have already stated. This isn't about cost solely, but a combination of reliability and cost. The reduction in power is also something I wouldn't accept. I want a replacement engine to be at least as powerful, if not more than the one it is replacing, otherwise why risk it?
We cannot afford unreliable machines in the the flying school/club environment. They have to make their TBO/TBR with few problems, something I haven't seen (m)any diesels do yet. When that happens and I get an agreement from the manufacturers that they'll guarantee their product, then sign me up.
The current promise to pro-rata an engine if it fails before it's due time is good, but what about the reliability of the electronics? I doubt they are included in that deal.
Whilst neither Lycoming or Continental do this, they are a known quantity already.
I can forsee this as most governments see GA as a rich man's hobby.
We currently pay £1.34 litre for AVGAS.
For example our PA 28 averages around 34 l/hr so costs us £45.56/hr or over an engine life of 2000 hrs : £91120 for fuel, add in the cost of the engine in the first place (approx £18K) gives a total life cost (not including servicing and oil) of £109120. This is however a 181 Archer II, with performance that leaves a diesel machine for dead.
A Diesel conversion costs in the region of £50K with costs of approx 63p/l and with an assumption of a burn around 25 l/hr giving a cost of £15.75/hr for fuel.
Again assuming a 2000hr TBR you are looking at a cost over the life of that engine (excluding maintenance and oil etc.) of £81500.
A significant saving yes, but as I have already stated. This isn't about cost solely, but a combination of reliability and cost. The reduction in power is also something I wouldn't accept. I want a replacement engine to be at least as powerful, if not more than the one it is replacing, otherwise why risk it?
We cannot afford unreliable machines in the the flying school/club environment. They have to make their TBO/TBR with few problems, something I haven't seen (m)any diesels do yet. When that happens and I get an agreement from the manufacturers that they'll guarantee their product, then sign me up.
The current promise to pro-rata an engine if it fails before it's due time is good, but what about the reliability of the electronics? I doubt they are included in that deal.
Whilst neither Lycoming or Continental do this, they are a known quantity already.
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Originally Posted by IO540
Everything else being equal (which it isn't) I would prefer avtur over avgas simply because of much better availability when looking at the international airfield/airport scene as a whole. However, on farm strips it is likely to be very much the other way round.
IO540 has a point. While this may not be so in the UK, venturing further afield 100LL avail definitely is very high on the list when it comes to flight planning. Being able to use AVTUR would be a godsend ! Horses for courses, really....
What I also fail to grasp is why the diesel guys are offering engines that produce less power than the ones they are supposed to replace.
In any case, as long as 100LL and AVTUR in the only GA market that really counts (USA) are roughtly the same price, I doubt the big diesel breakthrough
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What is TBO on the Thielert? I thought it was 1500, but I may be wrong. This would put your cost saving into the red.
I compared a Wilch 100 hp (forgive the spelling) with a Rotax 912s 100hp some time ago. The Rotax was £8600 inc Vat and delivery to my house, the Wilch was £14750. The Diesel was much heavier and the total running time was measured in 100’s of hours.
Rod1
I compared a Wilch 100 hp (forgive the spelling) with a Rotax 912s 100hp some time ago. The Rotax was £8600 inc Vat and delivery to my house, the Wilch was £14750. The Diesel was much heavier and the total running time was measured in 100’s of hours.
Rod1
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My figures are giving a best case scenario for a diesel. They are nothing more than a rough estimation.
If I'm not mistaken, the current TBO for a thielert is 1500 hrs, but they are hoping to increase this to 2000.
Was the Rotax for a PT aircraft (ie for flight training) or for a permit? That makes a massive difference in cost. Actually a Rotax is a pretty expensive engine for what it is.
If I'm not mistaken, the current TBO for a thielert is 1500 hrs, but they are hoping to increase this to 2000.
Was the Rotax for a PT aircraft (ie for flight training) or for a permit? That makes a massive difference in cost. Actually a Rotax is a pretty expensive engine for what it is.
Originally Posted by IO540
In cruise, a Rotax will not deliver more HP per given fuel flow than a properly operated old Lyco - the power comes solely from burning fuel and once you are at peak EGT, or even LOP, there is nothing more to gain.
BTW IO540, regarding the diesel advert in Loop. Was there any web links published? Could you pm them to me if so? I'm in India at the mo and Loop doesn't get that far! Thanks
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I am sorry Andy_rr I binned the magazine immediately after reading it - like I do with all magazines, and it's gone now.
It was a 4 cylinder engine, with 6cyl versions mentioned. I've just remembered that the image was computer generated and they were looking for somebody to pay for the tooling to make the first one, so this is something at a really early stage.
I am not an engine expert but would be suprised if a higher revving engine would out-do an old Lyco when it comes to efficiency when LOP. More revs means more friction losses, the same airflow through a smaller inlet manifold means more pumping losses, a gearbox means yet more losses. With car engines this is all irrelevant because high revs is the only way to get the HP from a physically small unit.
AFAIK the most efficient engine is one with a single large cylinder, working at very low revs. Everything else is a compromise
It was a 4 cylinder engine, with 6cyl versions mentioned. I've just remembered that the image was computer generated and they were looking for somebody to pay for the tooling to make the first one, so this is something at a really early stage.
I am not an engine expert but would be suprised if a higher revving engine would out-do an old Lyco when it comes to efficiency when LOP. More revs means more friction losses, the same airflow through a smaller inlet manifold means more pumping losses, a gearbox means yet more losses. With car engines this is all irrelevant because high revs is the only way to get the HP from a physically small unit.
AFAIK the most efficient engine is one with a single large cylinder, working at very low revs. Everything else is a compromise