Diesel powered helicopters
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Powerband is only limited by emissions, and installation, but not engine design . Usually it is most noticeable in turbo diesels. The combustion speed, hence RPM, is limited so that you need more torque for power similar to gasoline model. Trouble is it's likely to be a derivative of the same gearbox, so that limits torque. The net result is that the max torque ends up closer to the max power, so smaller power band.
Since helis are constant RPM machines, i see no problem with a diesel installation. If anything a turbo diesel is ideal, since all can be matched for single RPM operation.
Mart
Since helis are constant RPM machines, i see no problem with a diesel installation. If anything a turbo diesel is ideal, since all can be matched for single RPM operation.
Mart
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If you want to make Diesels for helicopters you will need a minimum of 180 hp at no more than a Lycosaurus's weight - at that weight it will not last 2000 hrs - not even 500.
Not counting for the heavier clutch/damper/trans you need to deal with the sharp torque spikes with every power stroke...
For anything bigger than a R22 you will need more likely 300hp at some time in the performance charts.
Again the only Diesel close to these numbers is the German Thielert V8 with a max cont. power of 250 or 260 hp at 600lbs!!
However if Diesel or better Jet-A burning is good enough for you, watch for the Swiss Mistral-Engines.
If they pull off their 1st certification this year or next, I bet you will see a 360 hp Jet-A burning 3 rotor-turbo engine within 4 years! 3000 hr TBO at no more than $10000.- of todays value (for the overhaul!! Compare that to a Lycoming...), at a weight of no more than a Lyc 540!
3top
Not counting for the heavier clutch/damper/trans you need to deal with the sharp torque spikes with every power stroke...
For anything bigger than a R22 you will need more likely 300hp at some time in the performance charts.
Again the only Diesel close to these numbers is the German Thielert V8 with a max cont. power of 250 or 260 hp at 600lbs!!
However if Diesel or better Jet-A burning is good enough for you, watch for the Swiss Mistral-Engines.
If they pull off their 1st certification this year or next, I bet you will see a 360 hp Jet-A burning 3 rotor-turbo engine within 4 years! 3000 hr TBO at no more than $10000.- of todays value (for the overhaul!! Compare that to a Lycoming...), at a weight of no more than a Lyc 540!
3top
Last edited by 3top; 14th Jun 2005 at 13:22.
New 3-Seat Diesel Helicopter
A german company MK Helicopters displayed the first prototype of their MK3 helicopter at the Aero2005 Airshow at Friedrichshafen last month. This new machine on first glance appears to be the answer to many Rotorheads dreams, a diesel light helicopter!
The machine has an empty weight of 700kg, a MTOW of 1182kg and is powered by the SMA 4-stroke flat-four diesel unit, producing a maximum rated power of 230hp. The machine has a two-blade main and tail rotor with composite blades and is very, very nice to look at!
I think this machine has a great deal of potential, but appears to have a VERY low power-to-weight ratio, which I fear may criple the machines performance. My guess is that during flight test they will find they either have to accept lower than claimed performance or a significantly lower than advertised gross weight. I hope not though; if they can offer what they claim at a price somewhere between R22 and R44 then they have a winner on their hands!
Good luck to the MK Team!
CRAN
NOTE: Edited to ad web address; www.mk-helicopter.de
The machine has an empty weight of 700kg, a MTOW of 1182kg and is powered by the SMA 4-stroke flat-four diesel unit, producing a maximum rated power of 230hp. The machine has a two-blade main and tail rotor with composite blades and is very, very nice to look at!
I think this machine has a great deal of potential, but appears to have a VERY low power-to-weight ratio, which I fear may criple the machines performance. My guess is that during flight test they will find they either have to accept lower than claimed performance or a significantly lower than advertised gross weight. I hope not though; if they can offer what they claim at a price somewhere between R22 and R44 then they have a winner on their hands!
Good luck to the MK Team!
CRAN
NOTE: Edited to ad web address; www.mk-helicopter.de
Last edited by CRAN; 11th Jun 2005 at 12:44.
Veryvery nice helicopter.
Looks like it can be flown RH seat with 2 pax!
Also looks like they are planning to have the Garmin 430/530 pack on the center console. The G-1000 would be even better!
Crashworthy seats, probably required for EASA 27 certification.
I think the proposed TBO time for the SMA 230 is 3000 hrs. If that holds it a very big plus.
I can´t see any baggage hold? Hope they include some kind of baggage/cargo space!
Unfortunately great ideas for new helicopter pop up quite regularly and disappear just as fast! I hope this one makes it to production.
To have it powered by a diesel should make it a winner.
Looks like it can be flown RH seat with 2 pax!
Also looks like they are planning to have the Garmin 430/530 pack on the center console. The G-1000 would be even better!
Crashworthy seats, probably required for EASA 27 certification.
I think the proposed TBO time for the SMA 230 is 3000 hrs. If that holds it a very big plus.
I can´t see any baggage hold? Hope they include some kind of baggage/cargo space!
Unfortunately great ideas for new helicopter pop up quite regularly and disappear just as fast! I hope this one makes it to production.
To have it powered by a diesel should make it a winner.
D3,
Certainly not! I'm always pleased to see new ideas and designs in the market place and so try to be as positive as possible, even when I don't agree with the approach adopted. You'll note that I immediately commented that the power-to-weight ratio is (IMHO) very low and that they are having to work the un-proven engine extremely hard just to achieve this low power-to-weight ratio.
Simply stated the machine will be underpowered and I personally would expect reliability problems with the over worked engine. In practise I think that the machine will have pretty poor performance; worse than that claimed and also when compared to the R44, simply because its too heavy.
I hope this clarifies things.
CRAN
Certainly not! I'm always pleased to see new ideas and designs in the market place and so try to be as positive as possible, even when I don't agree with the approach adopted. You'll note that I immediately commented that the power-to-weight ratio is (IMHO) very low and that they are having to work the un-proven engine extremely hard just to achieve this low power-to-weight ratio.
Simply stated the machine will be underpowered and I personally would expect reliability problems with the over worked engine. In practise I think that the machine will have pretty poor performance; worse than that claimed and also when compared to the R44, simply because its too heavy.
I hope this clarifies things.
CRAN
Yes CRAN I absolutely agree with you that those performance figures seem to be overly optimistic to me as a layman.
However we do not know yet if the SMA 230 is overworked when producing 230 hp constant!
Usually aircraft engines are not designed like car engines, where the car/automobile engine is only designed to produce its rated horsepower for less than 25% of the time and aircraft gasoline engines for less than 75% continious power.
Lets hope the SMA and other diesel engines were designed to produce rated power 100% of their operating time, does any one know?
However we do not know yet if the SMA 230 is overworked when producing 230 hp constant!
Usually aircraft engines are not designed like car engines, where the car/automobile engine is only designed to produce its rated horsepower for less than 25% of the time and aircraft gasoline engines for less than 75% continious power.
Lets hope the SMA and other diesel engines were designed to produce rated power 100% of their operating time, does any one know?
Aesir,
A few years ago, when the SMA305 series first appeared (along with the other aero-diesels) I looked into them in rather a lot of detail with regards to using them to power light helicopters. I found that I couldn't satisfy myself sufficiently that you could expect to produce a diesel engine light enough while maintaining the level of reliability and cost-effectiveness that people seem to be claiming for the demanding helicopter duty cycle. Sure you can do it, with some expensive materials and clever engineering, but then you end up with an engine costing as much as an equivalent turbine and I know which I would rather have powering my machine!
For those that are interested an early report on the subject is given in NASA CP-3260, by Alex Brouwers, in April 1980, whom studied a configuration not dissimilar from that subsequently developed (but not brought to market yet) by Zoche. The report clearly highlights both the well published benefits and many of the technical challenges in the field that to my knowledge have simply not been addressed. Furthermore, the literature is littered with accounts of companies both automotive and aeronautical attempting to 'get the weight out' of diesel engines and failing miserably; running into enormous technical problems! Has anybody wondered why SMA, Wilksch, Zoche, DieselAir and Deltahawk Diesel have all been ‘developing’ engines for over ten years, even with their doubtless capability and credentials? Or why both Lycomming (with Detriot Diesel) and Continental (NASA GAP Project) have abandoned their efforts? There are some very good reasons I assure you…
I know I keep hammering on with the same point, but you simply cannot escape the fact that helicopters have one of the most demanding duty cycles of any application for engines, not least of which is the requirement for engines with and extremely high power-to-weight ratio (i.e. turbines optimised for the application). Diesel engines occupy the opposite end of the P/W spectrum, having one of the lowest power-to-weight ratios, so where is the sense in trying that! This is a simple fact that if ignored will lead to an expensive, underpowered, underperforming, bulkly white elephant. (No pun intended.)
I will follow the MK Project with great interest and dearly hope, for their sake, to be found to be incorrect.
Best Wishes
CRAN
PS: Would you really want an engine in your helicopter that had absolutely nothing in reserve? No spare couple of inches of MAP! No five min or 30sec rating?
A few years ago, when the SMA305 series first appeared (along with the other aero-diesels) I looked into them in rather a lot of detail with regards to using them to power light helicopters. I found that I couldn't satisfy myself sufficiently that you could expect to produce a diesel engine light enough while maintaining the level of reliability and cost-effectiveness that people seem to be claiming for the demanding helicopter duty cycle. Sure you can do it, with some expensive materials and clever engineering, but then you end up with an engine costing as much as an equivalent turbine and I know which I would rather have powering my machine!
For those that are interested an early report on the subject is given in NASA CP-3260, by Alex Brouwers, in April 1980, whom studied a configuration not dissimilar from that subsequently developed (but not brought to market yet) by Zoche. The report clearly highlights both the well published benefits and many of the technical challenges in the field that to my knowledge have simply not been addressed. Furthermore, the literature is littered with accounts of companies both automotive and aeronautical attempting to 'get the weight out' of diesel engines and failing miserably; running into enormous technical problems! Has anybody wondered why SMA, Wilksch, Zoche, DieselAir and Deltahawk Diesel have all been ‘developing’ engines for over ten years, even with their doubtless capability and credentials? Or why both Lycomming (with Detriot Diesel) and Continental (NASA GAP Project) have abandoned their efforts? There are some very good reasons I assure you…
I know I keep hammering on with the same point, but you simply cannot escape the fact that helicopters have one of the most demanding duty cycles of any application for engines, not least of which is the requirement for engines with and extremely high power-to-weight ratio (i.e. turbines optimised for the application). Diesel engines occupy the opposite end of the P/W spectrum, having one of the lowest power-to-weight ratios, so where is the sense in trying that! This is a simple fact that if ignored will lead to an expensive, underpowered, underperforming, bulkly white elephant. (No pun intended.)
I will follow the MK Project with great interest and dearly hope, for their sake, to be found to be incorrect.
Best Wishes
CRAN
PS: Would you really want an engine in your helicopter that had absolutely nothing in reserve? No spare couple of inches of MAP! No five min or 30sec rating?
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CRAN,
if you are in contact with MK, tell them to talk to the Mistral-people in Geneva! ...maybe they already did.
Just to repeat it, the Mistral-JetA is not a real Diesel (their CEO hates the word Diesel by now!), but a spark ignited, direct-injection, JetA burning, turbocharged Rotary.
Their W/P ratio is at or better what you find in any Lycosaurus.
MK will get no where with the SMA - too heavy, and as you said " no spare MP" ", I also hope (for them...) they have some luggage-space - at least what Robinson has, or forget it!
Beautiful machine though!
3top
if you are in contact with MK, tell them to talk to the Mistral-people in Geneva! ...maybe they already did.
Just to repeat it, the Mistral-JetA is not a real Diesel (their CEO hates the word Diesel by now!), but a spark ignited, direct-injection, JetA burning, turbocharged Rotary.
Their W/P ratio is at or better what you find in any Lycosaurus.
MK will get no where with the SMA - too heavy, and as you said " no spare MP" ", I also hope (for them...) they have some luggage-space - at least what Robinson has, or forget it!
Beautiful machine though!
3top
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Worlds first diesel engined helicopter...?
Worlds first diesel engined helicopter...?
http://www.airliners.net/search/phot...nct_entry=true
There has been a lot of talk but this is the first time I have heard of actual testing.
RD
http://www.airliners.net/search/phot...nct_entry=true
There has been a lot of talk but this is the first time I have heard of actual testing.
RD
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Hmmm nice...
VW TDI is a good choice for a heli powerplant, since it is reasonably high revving so relatively light. I wonder if they have retuned it for fixed RPM operation. If lag is no problem turbo could have been pushed up, and cam may be altered, so max torque is on max RPM. Also emissions will not be such a consideration so they may run it closer to stoichiometric before the fuel limiter cuts in. All go to bettering that 170BHP figure, without seriously affecting engine life (since combustion pressure balances piston inertia - high torque at low RPM is worse case).
Mart
Mart
Last edited by Graviman; 28th Apr 2014 at 17:30. Reason: BMW diesel is not related to Steyr M16.
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I was just looking at the MK-Helicopter project. To me it looks as if they are using Jet A on their "diesel" engine. Why would you want to do this, use Jet A instead of the much cheaper "diesel".
When I first looked at it I was telling myself: great idea, good looking helicopter, finally something new, something more sophisticated then a Robbie or a Hughes.
But then again I figured out that it is just a project, following MK I and MK II (also good looking machines). And when looking at the main rotor mast...
... well so far only that tiny little mast of a Robinson scared me.
When I first looked at it I was telling myself: great idea, good looking helicopter, finally something new, something more sophisticated then a Robbie or a Hughes.
But then again I figured out that it is just a project, following MK I and MK II (also good looking machines). And when looking at the main rotor mast...
... well so far only that tiny little mast of a Robinson scared me.
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Well, i think 3-top has hit the nail on the head. The SMA engine is not a true diesel, in the sense that it is "spark ignition" and not "compression ignition". The main reason for high compression ratio in a true diesel is to get the ignition, which is where the weight comes in. I imagine that Jet A ignites far more easily than diesel, since this is how turbines are started.
In truth you can actually get good efficiency out of a petrol by pushing up the turbo boost pressure (eg VAG 1.8 turbo can offer 275 BHP, while still achieving 30mpg). You need to intercool the mixture to avoid detonation, and never quite get around the NOx emission problem (ie need a catalyst for auto use). The trouble is that by the time you've pushed up the "pressure ratio" enough to offer diesel type efficiency the need to improve crank and cylinder liners means the thing weighs as much as a diesel.
I suspect that as turbos become multistage, for fast response and high pressure ratios (along with lighter ceramic construction) petrol efficiency will improve - as long as the engine is designed for boost from the outset. Equally as combustion development continues (mostly through ECU injection control), diesel power to weight will improve. My own preference is diesel, since i see advantages in alternate fuelling and fuel metering for combustion temperature (engine at part load is also inherently efficient)...
Mart
In truth you can actually get good efficiency out of a petrol by pushing up the turbo boost pressure (eg VAG 1.8 turbo can offer 275 BHP, while still achieving 30mpg). You need to intercool the mixture to avoid detonation, and never quite get around the NOx emission problem (ie need a catalyst for auto use). The trouble is that by the time you've pushed up the "pressure ratio" enough to offer diesel type efficiency the need to improve crank and cylinder liners means the thing weighs as much as a diesel.
I suspect that as turbos become multistage, for fast response and high pressure ratios (along with lighter ceramic construction) petrol efficiency will improve - as long as the engine is designed for boost from the outset. Equally as combustion development continues (mostly through ECU injection control), diesel power to weight will improve. My own preference is diesel, since i see advantages in alternate fuelling and fuel metering for combustion temperature (engine at part load is also inherently efficient)...
Mart
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Where in Finland can I see this diesel engined 300C?
I think it is a hypothetical item as certification issues would hamper any progress of this kind of technology. Or is the Finnish CAA more forward thinking than the majority of correspondents on this post.
IMHO I believe that there is never a reason for 'quoting' ''It will never happen on a helicopter as it will be too heavy''.
I once wrote that soon helicopters would be crewed by law enforcement agencies who would have gun/rockets fitted as a response to criminal activity, and I was shot down in flames by many who said it was impossible.
Well, what has now happened? There are seroius proposals to fit guns/misiles. So why is it not possible to have a light weight powerful diesel engined helicopter?
Of course there will be such machines, and sooner than the sceptics would believe.
The diesel helicopter is coming and yes the big danger is governmental taxation of GA diesel fuel.
If there is a popular item then the tax man will want to tax it, that's for sure. I would hope they didn't but my hoping will not save the world.
I think it is a hypothetical item as certification issues would hamper any progress of this kind of technology. Or is the Finnish CAA more forward thinking than the majority of correspondents on this post.
IMHO I believe that there is never a reason for 'quoting' ''It will never happen on a helicopter as it will be too heavy''.
I once wrote that soon helicopters would be crewed by law enforcement agencies who would have gun/rockets fitted as a response to criminal activity, and I was shot down in flames by many who said it was impossible.
Well, what has now happened? There are seroius proposals to fit guns/misiles. So why is it not possible to have a light weight powerful diesel engined helicopter?
Of course there will be such machines, and sooner than the sceptics would believe.
The diesel helicopter is coming and yes the big danger is governmental taxation of GA diesel fuel.
If there is a popular item then the tax man will want to tax it, that's for sure. I would hope they didn't but my hoping will not save the world.
Would you not be better putting all that R&D money, time and effort into something than is fundementally more suitable...
One example, 17kg (with gearbox removed), 200hp, better fuel efficiency than Lycoming:
Or following Inodyns efforts:
Just food for thought...
Helicopters need an incredible power-to-weight ratio, so why not start with the type of engine that gives the best power-to-weight ratio?
Hope this helps
CRAN
One example, 17kg (with gearbox removed), 200hp, better fuel efficiency than Lycoming:
Or following Inodyns efforts:
Just food for thought...
Helicopters need an incredible power-to-weight ratio, so why not start with the type of engine that gives the best power-to-weight ratio?
Hope this helps
CRAN
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Site looks good:
http://www.innodyn.com/aviation/products.html
Couldn't see any quotes for fuel consumption. Don't forget an automotive diesel can achieve 200 g/kW-Hour which would be hard matched by a turbine.
Mart
http://www.innodyn.com/aviation/products.html
Couldn't see any quotes for fuel consumption. Don't forget an automotive diesel can achieve 200 g/kW-Hour which would be hard matched by a turbine.
Mart
Yeah but...
Is that really a benefit?
Most missions carried out by commerical helicopters require a flight time of less than 3hrs (@ cruise power). If we go to jet fuel then the cost of fuel becomes a relatively unimportant part of the operating cost, so we are back to considering the weight issue as the design driver.
Considering the total weight of the engine system as the weight of engine+fuel then for an example helicopter requiring 200hp.
SMA SR305-230 Diesel
-------------------------
Engine=225kg
3hrs Fuel = (200hp*0.36lb/hp-hr*3hrs)/2.2lb/kg = 98kg
Total = 323kg
SavioPower Turbine
---------------------
Engine=17kg
3hrs Fuel = (200hp*0.5lb/hp-hr*3hrs)/2.2lb/kg = 136kg
Total = 153kg
Therefore the turbine unit, despite using more fuel offers a 170kg payload advantage for a realistic mission which is the difference between 2-seats or 4-seats plus bags in your helicopter for the same power and MTOW. (Or 2-seats with high performance and a crash worthy fuselage depending on how you wish to spend your additional weight budget)
This is why I keep hammering on about diesel engines and helicopters. I love diesel engines, my car has a diesel engine - but I wouldn't dream of putting one in a helicopter because they are not the right engine for the job. Gravy, you correctly point out that automotive diesels are producing BSFC's of 200g/kW-hr. Sadly they wouldn't be able to produce this at peak output and thats how you would have to use them to get a helicopter off the ground.
Hope this helps
CRAN
Most missions carried out by commerical helicopters require a flight time of less than 3hrs (@ cruise power). If we go to jet fuel then the cost of fuel becomes a relatively unimportant part of the operating cost, so we are back to considering the weight issue as the design driver.
Considering the total weight of the engine system as the weight of engine+fuel then for an example helicopter requiring 200hp.
SMA SR305-230 Diesel
-------------------------
Engine=225kg
3hrs Fuel = (200hp*0.36lb/hp-hr*3hrs)/2.2lb/kg = 98kg
Total = 323kg
SavioPower Turbine
---------------------
Engine=17kg
3hrs Fuel = (200hp*0.5lb/hp-hr*3hrs)/2.2lb/kg = 136kg
Total = 153kg
Therefore the turbine unit, despite using more fuel offers a 170kg payload advantage for a realistic mission which is the difference between 2-seats or 4-seats plus bags in your helicopter for the same power and MTOW. (Or 2-seats with high performance and a crash worthy fuselage depending on how you wish to spend your additional weight budget)
This is why I keep hammering on about diesel engines and helicopters. I love diesel engines, my car has a diesel engine - but I wouldn't dream of putting one in a helicopter because they are not the right engine for the job. Gravy, you correctly point out that automotive diesels are producing BSFC's of 200g/kW-hr. Sadly they wouldn't be able to produce this at peak output and thats how you would have to use them to get a helicopter off the ground.
Hope this helps
CRAN
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Not that I don't like turbines - I've been flying them since 1978...
But........
Don't forget to compare the other, possibly more important "power to pounds ratio", i.e. initial engine purchase cost and the subsequent overhaul costs. What might be acceptable for commercial ops may be totally unrealistic for a private aircraft owner.
Turbines can make your cheeks squeak and your eyes water.
But........
Don't forget to compare the other, possibly more important "power to pounds ratio", i.e. initial engine purchase cost and the subsequent overhaul costs. What might be acceptable for commercial ops may be totally unrealistic for a private aircraft owner.
Turbines can make your cheeks squeak and your eyes water.
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Cran,
Thanks for your very informed posts on this thread.
"I love diesel engines, my car has a diesel engine - but I wouldn't dream of putting one in a helicopter because they are not the right engine for the job."
Good point very well made - my car too. I can definately see the weight advantage of a turbine. My real point regarding diesel is that if you were to design an engine specifically for heli usage, you would run at least 2 stage (or even 3 stage) turbocharging to get the best power to weight (ideal is also 2-stroke). The actual engine would be very "solid", but would be very small for the air mass flow rate. This gives a happy compromise between cost, power, efficiency, and weight. Think of it as a piston high pressure stage gas turbine, which strikes me as the future of IC engine design anyway.
"Sadly they (auto diesels) wouldn't be able to produce this at peak output and thats how you would have to use them to get a helicopter off the ground."
If the diesel was optimised for constant RPM apps, then i don't fully agree. Cam would put max torque on max rpm, which would make for an undriveable car. Turbo is optimised for this RPM, at max power, which (for single stage) introduces lag similar to turbine. Boost then becomes BMEP controlled, maintaining efficiency. Again the result is a compromise specific to heli duty cycle.
Mart
Thanks for your very informed posts on this thread.
"I love diesel engines, my car has a diesel engine - but I wouldn't dream of putting one in a helicopter because they are not the right engine for the job."
Good point very well made - my car too. I can definately see the weight advantage of a turbine. My real point regarding diesel is that if you were to design an engine specifically for heli usage, you would run at least 2 stage (or even 3 stage) turbocharging to get the best power to weight (ideal is also 2-stroke). The actual engine would be very "solid", but would be very small for the air mass flow rate. This gives a happy compromise between cost, power, efficiency, and weight. Think of it as a piston high pressure stage gas turbine, which strikes me as the future of IC engine design anyway.
"Sadly they (auto diesels) wouldn't be able to produce this at peak output and thats how you would have to use them to get a helicopter off the ground."
If the diesel was optimised for constant RPM apps, then i don't fully agree. Cam would put max torque on max rpm, which would make for an undriveable car. Turbo is optimised for this RPM, at max power, which (for single stage) introduces lag similar to turbine. Boost then becomes BMEP controlled, maintaining efficiency. Again the result is a compromise specific to heli duty cycle.
Mart
Last edited by Graviman; 29th Jul 2005 at 08:58.