Deltahawk at Sun N Fun ? (2013)

[SvingenB]

Originally Posted by rv6ejguy

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.

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.

[rv6ejguy]

Originally Posted by SvingenB

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.

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.

[rzbill]

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.

[Moondog]

Originally Posted by JP Brooks

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

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.

[rv7charlie]

Originally Posted by rzbill

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.

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

[Michael White]

Originally Posted by rv7charlie

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

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.

[rv6ejguy]

Originally Posted by rv7charlie

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

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.

[rzbill]

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.

[java]

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.

[rv6ejguy]

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.