Deltahawk at Sun N Fun ? (2013)

Yes, let's face it, tens of thousands of existing SI aviation engines are not going to be replaced with diesels, there will be a new unleaded avgas available to support that fleet sometime in the future when 100LL is actually phased out. There are programs now in place in the US to distribute non-ethanol 91 UL to airports and there are similar things happening in Europe now too, thanks to large Rotax 912 usage there. It is hard to say how this will pan out and how expensive the alternatives might be. Turbine re-engining of 421s now and maybe Navajos next would reduce the need for higher octane unleaded replacement fuels to some degree outside the few WW2 vintage aircraft flying.

The 2 stroke diesel seems pretty weight competitive, at least WAM has demonstrated that. If DH's new numbers are realistic, they are also in the ballpark to directly replace legacy certified SI engines from a weight perspective. The 2 stroke internally is pretty simple, the WAM has proven remarkably reliable for a new design. If they can do it, others should be able to as well.

I guess we also have to consider heavy fuel (ie Jet A) SI engines. Continental was working on a design quite a few years ago. Not sure how that is progressing, perhaps shelved now as they bought into the SMA diesel program.

The big thing with new engines seems to be the cost which is why the latest US V8 diesel development targets the 400hp+ market to replace the big turbocharged Conti and Lyc sixes in twins. $60-$80K is ok is this market but these sort of prices for 200hp class engines won't go far IMO.

We'll soon see (perhaps!) how the DH pans out, whether it is another SMA or Thielert which didn't live up to the press hipe showered on them nor on reliability or overall operating cost fronts. DH has certainly had the time to get all the major bugs out in testing so let's hope they have, and launch and initial service feedback is smooth and good.

Diamond is selling diesels like hot cakes. Next year they will have a certified V8, 450 HP and a 450 HP turbine.

We already have avgas 91/92, no lead, but that fuel cannot fully replace 100LL. From a standpoint of counting the number of aircrafts that needs a replacement for 100LL, it makes sense to develop a replacement. But, the marked is shrinking every day, diesels and turbines from the upper end and auto gas using engines from the lower end. Very few wants to head into a niche market that is shrinking. The money can be put to better use elsewhere. Thus, the price for 100LL as well as any replacement, has no way to go but up. This will increase the demand, particularly for diesels burning jet fuel.

SvingenB said:

Diamond is selling diesels like hot cakes. Next year they will have a certified V8, 450 HP and a 450 HP turbine.

We already have avgas 91/92, no lead, but that fuel cannot fully replace 100LL. From a standpoint of counting the number of aircrafts that needs a replacement for 100LL, it makes sense to develop a replacement. But, the marked is shrinking every day, diesels and turbines from the upper end and auto gas using engines from the lower end. Very few wants to head into a niche market that is shrinking. The money can be put to better use elsewhere. Thus, the price for 100LL as well as any replacement, has no way to go but up. This will increase the demand, particularly for diesels burning jet fuel.

Click to expand...

Yes, totally agree.

I don't read too much on how the new Austro engine is working in service. What do you hear in Europe? Are they lasting? Many high time ones yet? Just isn't too much news on this side of the pond. It was nice to see Diamond directly involved with the Austro powerplants and get control of the situation after the Thielert debacle.

Diesels and turbines make a lot more sense in Europe and Africa where 100LL is hard to find and/or crazy expensive so I think you see much higher numbers there so far.

I have to think DH wants to aim for the OEM markets here too, some decent starting numbers available to slowly ramp up production.

rv6ejguy said:

I don't read too much on how the new Austro engine is working in service. What do you hear in Europe? Are they lasting? Many high time ones yet?

Click to expand...

I don't know, around here I have only seen HK36 and DA/DV 20. But, the Austro diesel is increasing the TBO all the time. I think they are selling to aeronautic colleges, mostly in central Europe, Asia and Russia?

Their new 80HP Wankel is coming too. 27 kg and 80 HP, but ultra expensive I guess.

rv6ejguy said:

Yes, let's face it, tens of thousands of existing SI aviation engines are not going to be replaced with diesels, there will be a new unleaded avgas available to support that fleet sometime in the future when 100LL is actually phased out. There are programs now in place in the US to distribute non-ethanol 91 UL to airports and there are similar things happening in Europe now too, thanks to large Rotax 912 usage there. It is hard to say how this will pan out and how expensive the alternatives might be. Turbine re-engining of 421s now and maybe Navajos next would reduce the need for higher octane unleaded replacement fuels to some degree outside the few WW2 vintage aircraft flying.

The 2 stroke diesel seems pretty weight competitive, at least WAM has demonstrated that. If DH's new numbers are realistic, they are also in the ballpark to directly replace legacy certified SI engines from a weight perspective. The 2 stroke internally is pretty simple, the WAM has proven remarkably reliable for a new design. If they can do it, others should be able to as well.

I guess we also have to consider heavy fuel (ie Jet A) SI engines. Continental was working on a design quite a few years ago. Not sure how that is progressing, perhaps shelved now as they bought into the SMA diesel program.

The big thing with new engines seems to be the cost which is why the latest US V8 diesel development targets the 400hp+ market to replace the big turbocharged Conti and Lyc sixes in twins. $60-$80K is ok is this market but these sort of prices for 200hp class engines won't go far IMO.

We'll soon see (perhaps!) how the DH pans out, whether it is another SMA or Thielert which didn't live up to the press hipe showered on them nor on reliability or overall operating cost fronts. DH has certainly had the time to get all the major bugs out in testing so let's hope they have, and launch and initial service feedback is smooth and good.

Click to expand...

I know of a few companies working on lower compression heavy fuel SI engines. Of course, with lower compression, the engine weight can come down, as well as the cost. It would be the best of both worlds.

Kurt

OSH report please

Well, considering that OSH is just around the corner, I figured it was time to resurrect this thread.

Anybody going to look up Delta Hawk while at OSH, please update us.

It has been over two months since Mr. Brooks has logged on, and he was the best source of information available at the time this thread was active.

Demo flight video of one in action earns an extra 10 points

Thanks in advance.

Should be easy to find, right next to the Innodyne booth.

At a minimum they (Delta Hawk) should have their SR-22 there and there will most likely be a Delta Hawk powered Sportsman there. In fact, Glasair will be announcing (I believe) that the Delta Hawk will soon be an option in the Two Weeks to Taxi Program.

I think I heard someone in the booth saying "Hopefully by the end of the year."

Price of the 200hp engine looks to be a little scary. Almost $70,000 for a firewall forward setup.

http://www.deltahawkengines.com/Firewall prices.shtml

I was scheduled to fly the Sportsman with the Deltahawk at OSH, but it wasn't ready and didn't make the show. I wasn't really counting on it happening.

Ironflight said:

I was scheduled to fly the Sportsman with the Deltahawk at OSH, but it wasn't ready and didn't make the show. I wasn't really counting on it happening.

Click to expand...

This is really sad, lots to be read between the lines-----not only on Paul's post, but the history of DH also.

I have been following this engine for many years, and sincerely hope it will finally achieve widespread availability and success in the market.

But---------to schedule a test flight with the editor of a major aircraft magazine and then not show up............just simply a poor way of doing business. Why would anyone schedule a flight in something that is not even ready to fly???

At what point will the "Boy who cried wolf" effect take over and make all the customer base turn their collective backs on what looks to be a promising work of engineering design, all because of un-kept deadlines, unfulfilled claims, and just general poor performance in the publicity dept???

I wonder if going down the 2 stroke path in their design was a mistake. It requires a Supercharger, plus they add a turbo. Lots of extra complexity and expense.

Diesels make awesome torque down low and are relatively low revving engines. That, plus no need for an ignition system... I would think it'd be perfect for aviation.

You are right about the two stroke needing a supercharger, but it is offset by not needing a cam and all the assorted complexity, weight and lubrication requirements thereof associated with a valve train.

Most diesels have a turbo-----so I think that item is a wash.

I believe that two stroke diesels offer a better power/weight ratio.

I think they have a slightly higher fuel consumption however.

Mike S said:

But---------to schedule a test flight with the editor of a major aircraft magazine and then not show up............just simply a poor way of doing business. Why would anyone schedule a flight in something that is not even ready to fly???

Click to expand...

To be fair, the Sportsman that was to attend was a customer built airplane and not a Delta Hawk airplane, per se. The guy building it already has built a diesel powered RV-9(A), I think, and knows a lot about diesels in aircraft.

He was working with Glasair on a firewall forward package, and the project probably just ran out of time before the show. It wasn't that long ago that the factory was making the mold for the cowling.

grayforge said:

I wonder if going down the 2 stroke path in their design was a mistake. It requires a Supercharger, plus they add a turbo. Lots of extra complexity and expense.

Diesels make awesome torque down low and are relatively low revving engines. That, plus no need for an ignition system... I would think it'd be perfect for aviation.

Click to expand...

The WAM is a 2 stroke design that has been very successful and was developed on a fraction of the money and time as the DH. WAM has proven that there is nothing wrong with the 2 stroke approach. Perhaps DH could have learned some lessons from WAM on how to bring an affordable reliable diesel to market in a reasonable time?,

As a point of reference, diesels actually produce less torque than comparable SI engines. The torque of the modern diesel is only coming from the very high boost pressures being used.

I agree with Mike here. DH has lost most of its credibility long ago and really it does not even matter any more because at the current price point, these engines make no sense on an experimental and probably little more on a certified airframe in North America anyway. The fuel savings from a 2 stroke design are simply not there as confirmed by DHs own published BSFC figures. These engines will only be for the military, diesel die hards who don't care about the price and for operators where avgas is either hard to get or too expensive or both.

A guy involved with the DH project posted on this forum a few months back with more glowing information but would/ could not even answer simple questions about costs and performance/ weight. He deleted most of his posts and then quietly slipped away into the shadows again...

DH has spent millions on development, if they were actually serious about the market, they could have simply bought a used RV or Glasair for $50K and within a couple months, their engineers could have had their engine installed and test flown years ago, ready to give Paul a shot at it at Osh this year. Again, their actions simply bring into question their whole business model. Here was a great opportunity to show their stuff and regain some lost credibility, instead they generated yet even more negative perceptions of their product.

I love diesels, and think that it might be possible to make a competitive unit for GA. Many reasons, but the 2 stroke has too many issues to be developed into the best balance for aero. SFC is lacking mostly due to expansion ratio and aided by low BMEP with one firing per stroke. Sadly the carrot of commercialization is lacking and imbalanced to the extensive costs to develop a new from scratch design, pay for tooling, and payoff the investment.

Further, it would take some a very experienced design and development staff to pull it off to replace the highly evolved infrastructure for the Lyc/Conti. Sad, but reality.

Our best hope (General Aviation) may be the new Conti owners and their true commitment to diesel development for the China market. Maybe that volume will allow some Chinese manufacturing and produce an engine that is cost competitive and performance equal to the SI of today. Especially attractive could be that the EAB community could (may) get (import) it without the litigation costs.

I have noticed over the years that some small business models are focused more on the glamour of getting investor money than making a real product. That is really disappointing to a life long engineer, and tends to generate some critical questioning of some of the diesel offerings. The Conti approach does not seem to fall in that bucket.

I have watched this for nearly 30 years, and hope this can go mainstream in my lifetime. Sad for the USA which has provided these engines for many years.

Cirrus flying....yes!

http://www.aopa.org/News-and-Video/...k-flies-diesel-powered-Cirrus-SR20-to-Oshkosh

And...here we are again.

Enjoy,.... Someone pass this along to Mr. V plz. Thanks.....
http://www.avweb.com/avwebflash/news/Delta-Hawk-Almost-Ready-For-Production222486-1.html

Almost

Almost. If I had a extra 60k it wouldn't be spent on a 200 HP deltahawk.

Thanks Paul

Please enjoy that 8-Track tape and slide ruler. My sincere best wishes.

Nice to see some progress however unless the BSFC figures have been dramatically improved from a couple years ago, doubtful this engine is going to save 30% over a Lyc or Conti running LOP. We haven't seen it on other 2 stroke diesels running mechanical injection.

Why list TBO figures until they are actually set and proven? Projected TBOs are meaningless.

I'll say it again, a $60K, 200 hp aero diesel doesn't make economic sense in North America for GA. You can't compete when your acquisition costs are double that of a Lycoming with similar SFCs. Does makes sense for military UAV stuff and in places where avgas is not available or very expensive.

Looking at the Cirrus installation: http://www.deltahawkengines.com/PDFs/Cirrus SR20 - Press Release.pdf, why does a diesel need such a large air inlet? That looks to be close to 50 in2. That's a lot for a 200hp engine even feeding rad, oil and intercooler.

The 30-40% fuel savings mentioned here are unlikely, that implies a BSFC figure of .27 to .30.

Inlet size

Tough to find out you made the inlet too 'small'.
Easiest to size down (unlike diets).
We knew heat rejection could b cut.
Doug is great at allowing some leeway.
He careful and I like that.
(Thanks for asking)
If some of you aren't critical or done yawning
At us then you will see a smaller inlet and not
what I call the 'Monica Lewinski' inlet

doubtful this engine is going to save 30% over a Lyc or Conti running LOP. We haven't

Thanks for your doubts. We accept that, like Gilligan, you may never get off your island of criticism.
I truly want to meet you some day and shake hands with you. (You will, I trust,...come to appreciate your thinking may have flaws, as my thinking always has 'flaws'. The difference between you and me is that I know I can be wrong and change course to enjoy another day). Your input is most appreciated.

JP Brooks said:

Thanks for your doubts. We accept that, like Gilligan, you may never get off your island of criticism.
I truly want to meet you some day and shake hands with you. (You will, I trust,...come to appreciate your thinking may have flaws, as my thinking always has 'flaws'. The difference between you and me is that I know I can be wrong and change course to enjoy another day). Your input is most appreciated.

Click to expand...

Not negative, just realistic. these observations are based on my years in this field. The cowling looks lovely BTW.

Now, what's the story on the descrepancies on the published BSFC figures and cost comparisons on the website and the 30-40% figures on the "sales" side? I'm a math and engine guy and these figures don't compute.

The Conti 550 running LOP has a BSFC of around .38 in cruise- same as what is claimed for the DH. Lycoming with FI and EI running LOP, is around .40. Either way, that does not add up to 30-40%. We know here on VAF that a 360 running LOP does not burn 10 GPH at 65% power.

We are also not changing spark plugs every 200 hours and cost comparison is meaningless unless acquisition costs are taken into account.

When you can explain your numbers, more people might come around to shake your hand...

Since the engine has fewer parts, is simpler etc etc, will the acquisition cost eventually come down to lyc levels?

Bevan

JP Brooks said:

Thanks for your doubts. We accept that, like Gilligan, you may never get off your island of criticism.
I truly want to meet you some day and shake hands with you. (You will, I trust,...come to appreciate your thinking may have flaws, as my thinking always has 'flaws'. The difference between you and me is that I know I can be wrong and change course to enjoy another day). Your input is most appreciated.

Click to expand...

This rhetoric is not helpful. Without some hard data or blaming performance on the prop, it would be good to provide good reasoning and estimates for fuel usage. There are certainly beneficial contributions from idling where the Otto is very bad, and ROP on TO where it is also bad. After 20 years, surely there is an accurate fuel map of this engine. No one is trying to disparage this design and installation, nor the human effort that has been invested here. Just provide data or some good analysis in support of the claims.

A friend and engineer, who passed away before his time said "we mock what we don't understand"

rv6ejguy has stated a reasonable expectation and a definitive professional discourse would be helpful for all to advance the discussion.

your money

JP Brooks said:

Please enjoy that 8-Track tape and slide ruler. My sincere best wishes.

Click to expand...

If a pocket calculator cost $10 grand I would imagine most people would still be using slide rules. I do not see the point of spending that kind of money on a diesel where avgas is widely available. 60k is approaching Walter numbers.

When you putting your deposit down?

BillL said:

This rhetoric is not helpful. Without some hard data or blaming performance on the prop, it would be good to provide good reasoning and estimates for fuel usage. There are certainly beneficial contributions from idling where the Otto is very bad, and ROP on TO where it is also bad. After 20 years, surely there is an accurate fuel map of this engine. No one is trying to disparage this design and installation, nor the human effort that has been invested here. Just provide data or some good analysis in support of the claims.

Click to expand...

Yep. The diesel does probably save a fair amount in the taxi/ TO and climb phases where the SI engine is running relatively rich. On an RV though, the climb phase is short- less than 5 minutes in most cases so on a 2 or 3 hour trip, this doesn't amount to much. The vast majority of cross country work is spent in cruise.

Today, a diesel makes sense on a global perspective. AVGAS is not available in many places, or must be shipped exclusively (in small quantities) and this is very expensive. Jet A1 is available everywhere and costs almost nothing many places. The ability to use Jet A1 is the only important factor. The finer details of BSFC and such means nothing.

But - on a global perspective, the engine must be installed on certified aircraft, the engine itself also has to be available. The existence of an engine that cannot be installed on a C-172 or similar work horse, is not very helpful.

The two stroke diesel has many advantages compared to a 4 stroke. Less parts, virtually no vibrations from pulses, much more compact, much simpler altogether. Also, in time it should be no problem installing common rail (incl FADEC), and greatly improve the BSFC. But, it has to compete with SMA, Austro and Continental on the global market. It cannot compete with Lycoming clones on the experimental market, a small niche market based in the US where AVGAS is readily available, and where acquisition cost is the only important factor.

I think the technology looks cool, but I don't see it getting anywhere without a change of business strategy.

SvingenB said:

Today, a diesel makes sense on a global perspective. AVGAS is not available in many places, or must be shipped exclusively (in small quantities) and this is very expensive. Jet A1 is available everywhere and costs almost nothing many places. The ability to use Jet A1 is the only important factor. The finer details of BSFC and such means nothing.

But - on a global perspective, the engine must be installed on certified aircraft, the engine itself also has to be available. The existence of an engine that cannot be installed on a C-172 or similar work horse, is not very helpful.

The two stroke diesel has many advantages compared to a 4 stroke. Less parts, virtually no vibrations from pulses, much more compact, much simpler altogether. Also, in time it should be no problem installing common rail (incl FADEC), and greatly improve the BSFC. But, it has to compete with SMA, Austro and Continental on the global market. It cannot compete with Lycoming clones on the experimental market, a small niche market based in the US where AVGAS is readily available, and where acquisition cost is the only important factor.

I think the technology looks cool, but I don't see it getting anywhere without a change of business strategy.

Click to expand...

I agree with most of your points here except that the US experimental/ GA fleet is bigger than the rest of the world combined- hardly inconsiderable.

rv6ejguy said:

I agree with most of your points here except that the US experimental/ GA fleet is bigger than the rest of the world combined- hardly inconsiderable.

Click to expand...

I came to think about that myself too. I don't know if it is bigger than the rest of the worlds GA fleet, but maybe? It would be nice to see some numbers. It certainly is a larger factor than just a small niche.

In that case, things gets turned around a bit. Then the total cost of this engine is very comparable to the total cost of a Lycoming/clone. In no circumstance will the added cost be outrageous. But there will be benefits. Jet A1 is a fuel that will be available in all foreseeable future, and at a predictable and low cost, AVGAS is not. To be indipendant of the insecurities of concerning AVGAS, combined with "cool factor" and "experimental factor" of this engine may just be enough, certainly for people with some money. The engine may not be for everyone, but there will be enough people who want it to start a viable business.

SvingenB said:

I came to think about that myself too. I don't know if it is bigger than the rest of the worlds GA fleet, but maybe? It would be nice to see some numbers. It certainly is a larger factor than just a small niche.

In that case, things gets turned around a bit. Then the total cost of this engine is very comparable to the total cost of a Lycoming/clone. In no circumstance will the added cost be outrageous. But there will be benefits. Jet A1 is a fuel that will be available in all foreseeable future, and at a predictable and low cost, AVGAS is not. To be indipendant of the insecurities of concerning AVGAS, combined with "cool factor" and "experimental factor" of this engine may just be enough, certainly for people with some money. The engine may not be for everyone, but there will be enough people who want it to start a viable business.

Click to expand...

Some form of avgas will be around for a long time yet. You just can't orphan 100,000+ SI piston aircraft overnight. In the meantime, lots of us are using mogas for local flying and unleaded aviation fuel is available in many parts of Europe now. About 10 years ago, I saw a figure of about 200,000 aircraft in the US and 300,000 total worldwide. Not sure what the numbers are today or what proportion would be piston SI powered.

I agree there is a market for diesel lovers and the cool factor in North America but I'd caution people not to be the first on the DH bandwagon until a few years of fleet service shows they are actually reliable and durable. The SMA and Thielert engines certainly weren't when introduced. They were disasters for initial users.

If this engine was $30K instead of $60K, the economics would be quite different. You can buy a lot of fuel for $30K and the Lycoming can be serviced all over the globe- this is a big deal IMO.

Total cost of ownership burning avgas vs diesel has been hashed on other threads.
In the US, the average cost of 100LL is only 55 cents more than Jet A (See Airnav fuel report)

This, including an improvement in BSFC, will NOT compensate for 30 grand in extra capital cost. Not even close.

building on a budget

JP Brooks said:

(snip) If some of you aren't critical or done yawning (snip)

Click to expand...

No one is yawning as evidenced by the number of replies.
VAF is loaded with critical thinkers, they ask critical questions.

I am neither bored nor technically savvy enough to understand engines the way many posters do. Instead, my perpetual intrigue over a reliable affordable diesel always seems to keep me coming back despite my perpetual disappointment.

rzbill said:

Total cost of ownership burning avgas vs diesel has been hashed on other threads.
In the US, the average cost of 100LL is only 55 cents more than Jet A (See Airnav fuel report)

This, including an improvement in BSFC, will NOT compensate for 30 grand in extra capital cost. Not even close.

Click to expand...

But it's roughly twice the cost of 'farm' diesel. And we can pretend that Lycs/Conts can be operated at .38 BSFC, but if we're honest, maybe 2% of them actually *are* operated at that efficiency (and NONE of the carb'd engines even *can* be that good). Most, even injected are operated closer to .46-.48, real world.

Debating the world's demand is fine, but when it comes to an individual choice, the individual will likely pick what they perceive as best for them. I'd never pay $60K for a diesel, but I'd never pay $30K for a Lycosaur, either.

I tend to compare costs per hour for mogas vs farm diesel.

Charlie

rv7charlie said:

But it's roughly twice the cost of 'farm' diesel. And we can pretend that Lycs/Conts can be operated at .38 BSFC, but if we're honest, maybe 2% of them actually *are* operated at that efficiency (and NONE of the carb'd engines even *can* be that good). Most, even injected are operated closer to .46-.48, real world.

Debating the world's demand is fine, but when it comes to an individual choice, the individual will likely pick what they perceive as best for them. I'd never pay $60K for a diesel, but I'd never pay $30K for a Lycosaur, either.

I tend to compare costs per hour for mogas vs farm diesel.

Charlie

Click to expand...

Charlie,
You make some good points, but I'm afraid comparing avgas to farm diesel isn't really a valid comparison because farm diesel isn't available at airports. Sure, you can transport it to your home airport in the back of your truck, but most people won't do that. And if you do truck it to your home airport, then there's the question of what to do when you travel...you're pretty much stuck with what they have at the airports you stop at. So all in all, I think the avgas to Jet-A cost comparison is more valid in figuring life cycle costs.

JMHO, YMMV, etc. etc.

rv7charlie said:

But it's roughly twice the cost of 'farm' diesel. And we can pretend that Lycs/Conts can be operated at .38 BSFC, but if we're honest, maybe 2% of them actually *are* operated at that efficiency (and NONE of the carb'd engines even *can* be that good). Most, even injected are operated closer to .46-.48, real world.

Debating the world's demand is fine, but when it comes to an individual choice, the individual will likely pick what they perceive as best for them. I'd never pay $60K for a diesel, but I'd never pay $30K for a Lycosaur, either.

I tend to compare costs per hour for mogas vs farm diesel.

Charlie

Click to expand...

Hard to buy what you say here.

1. At .48 BSFC a 360 would be burning 10.8 GPH at 75% yet we see lots here on VAF closer to 8.5 to 9 which would be right around .40.

2. There are people here running carbed Lycos LOP successfully with carb heat.

3. Dyno testing on the Conti 550s running LOP as per recommendations confirm the sub .40 figures. So do various Mooney and Cirrus owners on forums.

4. There was a thread here on VAF a while back comparing O-235 fuel flows vs. the WAM diesel at similar TAS on RV9s. Pretty much a wash in cruise- 4.5 to 5.5/hr. in either case depending on speeds.

When avgas over here becomes the price it is in Europe, an aero diesel will make a lot more sense. Jet fuel isn't available a lots of small airports either.

Yeah, non-av fuel oil is cheaper than Jet-A and improves the cost picture.

Problem is, as soon as we start talking non-aviation fuel sources, then the comparison should be between non-av fuel oil and mogas. I don't have national average price data handy but I suspect the economics will turn out similar.

Your point about actual BSFC operation of lycs is important (I commonly operate at 0.42) but the delta between .46 gas and .38 deisel is still not enough to make the dollars come out in favor of a $60K diesel.

All I want in this exercise is truth in advertising. With that, I can make no argument if a buyer chooses a diesel. The buyer is going in with the full knowledge of choices made.

Numbers...

I'm a numbers guy too, but more so $'s than BSFC #'s. I ran some calculations from a financial perspective.

Assumptions:
- $30k premium, all in, capital cost to outfit with diesel vs. Lyco
- 200 hr/yr flying
- 2000 TBO on both engines
- Fuel prices used were the national average between 100LL and Jet-A from the link posted earlier. Need to assume the spread remains constant.
- Cost of capital = 5%
- I used numbers from my O-360 RV-6 as baseline for the Lyco, namely 8.5gph which I can safely plan for. Assume that I'd operate the diesel for equivalent performance.

Then reverse calculated how much more efficient the diesel would have to be to make it worth spending $30k more up front. The answer was 32%, or 5.8gph (getting the same performance I can get at 8.5gph from my Lyco).

Whether there exists an engine that can do this or not, I'll leave to the gear-heads to debate. There are also a lot more factors that come into play that are harder to quantify (at least right now), such as...

- Lyco's have a long history to support 2000 TBO. How do we know the diesel will make 2000 hours? Alternately, maybe it is more?
- Will the spread between 100LL and Jet-A remain, on average, constant, or will it widen or narrow?
- Will Lyc's even be burning 100LL in the future or will the elusive "better" alternative be found and widely accepted?
- What will be the maintenance cost difference?
- What will the relative reliability be (hard to quantify, but arguably most important factor).
- What is the real "cost of capital" for a representative purchaser?
- If you fly more per year, it looks better for the diesel (earn the money back faster). If you fly less, it looks better for the Lyco.

At the end of the day, EVEN IF there was hard proof that there was 32% lower fuel burn, I still wouldn't be shopping for this engine. My fuel cost per hour may be higher, but...
- Too many unknowns with the diesel.
- I already have a perfectly good Lyco.
- The economics, at least right now, are not compelling. I can't accept the unknowns (i.e. risks) of the diesel for break even. It would have to be some measure BETTER than 32% lower fuel burn to take a bet on it.

I am TOTALLY in favour of this engine development, and hope it becomes a viable alternative. I just don't want to fund the development and assume the risks associated with it. For those who have a different set of values (i.e. cool factor) and want to do so, I accept we all look at things differently and I wish you well.

Just one more guys view from a dollars and cents perspective. Worth what you paid for it.

Let's also remember that Jet and Avgas have different densities. Avgas weighs about 6 lbs./ US gal and Jet A around 6.7.

So, for the same volume burned, the diesel actually has worse BSFC when we look at it in pounds per hp per hour.

If we look at a diesel using 7.5 US GPH that's 50.25 lbs./hr.
If the Lycoming is at 8.5 GPH, that's 51 lbs./hr.

Of course we buy fuel by volume, not weight.

A quick check online found Jet A averaged $5.89/ gal vs. 100LL at $6.62

Our example diesel above would use $44.18/ hr.
The Lycoming $56.27/hr.
Delta $12/hr.

If we switch the Lycoming over to 91 mogas vs. Jet A, the delta becomes around $11/hr. in favor of the Lycoming.

If we use road diesel compared to retail premium mogas, the delta is about $7.30/hr. in favor of the diesel.

Operating a Lyc 360 at 8.5gph is not the same thing as operating it at 75% power.

Check Van's performance specs for speed at 75% of 180 HP; they are quite accurate, assuming a built-to-spec plane.

Check Lycoming's own numbers for fuel burn at 75%. I'm pretty sure that you'll find that 135 HP requires 10gph, plus/minus a percentage point or two.

As a sanity check, compare both the above to Van's still-air range figures.

Ask the guys if they are flying at Van's published 75% cruise speed when burning 8.5gph.

None of the above is really relevant to the diesel discussion, except that comparisons are pretty much meaningless unless accurate figures are used.

Again, I'm not about to buy a $60K diesel OR a $30K Lyc.

I DO haul premium mogas home for my Lyc powered RV-4, and I will haul low octane mogas for my rotary powered RV-7, when if flies.

Most of my flying is day trips, as I suspect is true for many others. I rarely purchase avgas, because I rarely need to. That is my point about each individual making decisions that are best for them. As I said, I'd be comparing mogas (not avgas) to farm diesel.

Charlie

java said:

I am TOTALLY in favour of this engine development, and hope it becomes a viable alternative. I just don't want to fund the development and assume the risks associated with it. For those who have a different set of values (i.e. cool factor) and want to do so, I accept we all look at things differently and I wish you well.

Click to expand...

Did a similar exercise with fuel prices at my local airport (ENVA, Norway). I have no idea what the average prices in Europe are though.

Fuel prices here, now (in US$/gal) is
100LL 9.16, Jet A1 5.93, MOGAS "off road" 7.06, Diesel "off road" 6.34

The break even is 711 hours flown. At 2000h I would have saved 54k with the Delta Hawk, that is almost a new engine. The break even for DH-Jet A1 vs Lyc-Mogas is about 1200 h.

It certainly is food for thought, but I even with these numbers the economics are so far into the future that it would not be a deciding factor, more like an excuse to do this or that. If, I for some reason would have something else than a Lycoming, then the DH is the only viable option (if it becomes available that is), and that is also a factor, maybe the main factor.

Point well made Bj?rnar.

With that large a spread in fuel costs, you are right that the payback is good.