Fuel Survey: Give Us Real Numbers

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In today's news feed, we're reporting a brief summary of the responses to our avgas replacement survey. More than 3000 people participated and at least 2000 of them provided written comments, most of which I have read. I consider the effort required a valuable education in what owners think about this critical issue. And they are thinking about it. I thought the most penetrating comment I read came from owner Tim Kramer, who said this:

We need estimates as to the cost of hardware modifications and forecast pricing for alternative blends. The pricing projections need to come from credible fuel producers, not from proponents of any particular formulation. Consumers want a cheap fuel that does not increase engine maintenance costs, does not reduce range or power, and is readily available within existing infrastructure. We won't know how to 'vote' until we see some data on modification costs and fuel pricing.

That, in a nutshell, frames the difficult conundrum that owners find themselves in. Through a maddening confluence of government slow-leak regulation and a weak market, every conceivable solution to replacing leaded fuels has significant and unattractive downsides. There is no obvious pain-free solution. And as Kramer points out, the people who are most at risk here—the actual buyers of fuel—don't have enough reliable information with good price signaling to form the definite opinions that will gel into unified demand. Our survey was an attempt to sound these dark depths and return with useful information. The results are sketchy at best, but still better than anything anyone else has done.

One thing seems obvious to me: Every possible path will cause erosion in flight activity and participation. Do nothing, lose owners due to doubt. Announce a pricier 100-octane solution, lose owners on cost issues. Tilt toward 94UL, lose owners who won't modify their aircraft. Push against mogas to sustain high-octane demand, lose owners at the low end. So, as I've said before, it may be a question not of picking the best solution, but the least bad one.

The alphabet groups might rather see less independent reporting on this topic than more, because they wish to control the narrative and one way of controlling that is to attempt to tamp down owner concern with the don't-worry-we've-got-this-covered approach. I'll concede some merit to this sentiment, but many owners simply won't buy it. And they are in the "overhang" group; the owners who are delaying purchases and upgrades because of doubts about fuel. These are owners who have hundreds of thousands tied up in assets that are useless without 100-octane fuel.

I'm inclined neither to inflame these owners nor blow puffs of sunshine their way as a narcotic against maintaining pressure to put a solution in sight as soon as possible. Every week, we are asked by a reader or two to keep the fuel issue front and center and I think it's important to do that as accurately and fairly as possible and to resist signing on to the industry propaganda apparatus.

Where to from here? This week, the FAA convenes a committee to yet again examine the replacement fuel issue, re-state the problem and, one hopes, actually move forward to a solution. I have yet to see a proposal better than that from Lycoming's Michael Kraft: Decide on a path within two years, allow eight to 10 years to implement it. The "decide" part is critical, because it injects some certainty into the market and at least reduces market erosion while the ultimate solution is put into place. Owners will begin to get the clarified price signals Tim Kramer is asking for and they can plan accordingly.

It's unfortunate that federal agencies like EPA play, perhaps unintentionally, a form of rope-a-dope. If they did not, perhaps the industry could realistically approach them with a proposal that splits the difference between various conflicting interests. One idea that has probably occurred to some is to propose the soon-to-be-approved 100VLL fuel as a standard, encourage more unleaded mogas and accept that airborne lead emissions will decline gracefully at a somewhat lower rate than emerging air quality standards might require. Long-term, the heavy-fuel engine demand curve will take over and further erode gasoline lead emissions. The argument for this is economic: jobs and infrastructure protection, a tradeoff against what surely must be the world's least critical environmental threat. But for this to work, EPA would have act quickly and decisively, which is something it simply does not do, preferring instead waffling and confusing statements that serve only to sow further doubt. Getting anything approaching clarity from this agency is impossible.

I'm not ignoring the single-point-lead-supply argument, by the way. I just think it's wrong. I recently registered with the Alibaba Trading Agency inquiring about tetraethyl lead opportunities in China. Now I get an e-mail every other day asking where I'd like it delivered and how much I want. I think if you want lead, you can get lead. There's not just one source.

Moving back into the realm of the doable, my guess is that an unleaded 100-octane solution of some kind is what the market wants and what is most likely to happen, eventually. The survey revealed very little support for 94UL, nor the modifications necessary to burn it. I can't imagine manipulating the wording in the questions to move that response much. Perhaps some more definitive comparative price data would help. If 94UL proponents want to push this fuel, they've got a sales job to do.

While I think mogas should be part of the mix—that's what owners say they want—this is going to be difficult. And the fact that half of the owners who want mogas recognize that it's probably a non-starter due to ethanol pressure is telling. Still, although it's the market equivalent of the Charge of the Light Brigade, it's worth a try.

What's not worth trying is accepting lack of action as owners continue to defect for lack of confidence in future fuel.

Comments (124)

"I consider the effort required a valuable education in what owners think"

I agree.
Most owners probably think they need 100 octane. Most renters and student pilots also think they need 100LL (or it's equivalent). It's no surprise at all since that's what they've always seen on airport and ever used in airplanes.

I only disagree that it's valuable information; I could have told you without the survey that most pilots think they need 100 and that they want to avoid engine cylinder work.

Posted by: Mark Fraser | March 16, 2011 9:29 AM    Report this comment

I tend to agree that the value of the survey information is limited. Not because I knew the results, but because of the self-selection bias that is inherent in this process. The results of the survey are naturally biased because this group of people chose to be subjects and, unfortunately, that will never yield the same results as a random sample of the pilot population. And to Paul’s credit he cites that fact, “the high response rate (of those requiring 100 octane fuel) may be due to owners of high-performance aircraft believing they have more at stake if a replacement fuel isn't found.”

Are the results useful, yes – but definitive, they are not. I did not respond to the survey, but as an aircraft owner with a mogas STC, I know my response would have “tilt(ed) strongly toward mogas” as Paul observed. Let’s hope someone comes up with reasonable solution soon as lead-free gas is where we are headed . . . and my low compression engine would greatly appreciate the absence of a lead-filled diet soner rather than later. I know - my bias shows!

Posted by: Rob Souza | March 16, 2011 7:41 PM    Report this comment

Rob, I did not respond to the survey either (and I own a couple of piston aircraft). Reasoned solutions are already available, so are 20+ years of "polls". There is overwhelming evidence that FAA, EPA, and producers don't listen to web surveys. That's why I'm justifiably cynical of the "usefulness" or "value" of another poll.

Posted by: Mark Fraser | March 16, 2011 8:31 PM    Report this comment

The only two bloggers in 24 hours are essentially non voters who complain about the election result? Gimme a break!

Posted by: Brad Vaught | March 16, 2011 11:50 PM    Report this comment

Thanks for the data Paul. You have done an excellent job accurately describing this clusterfu€k.

Keeping what we have is the rational best case scenario. Complete with a mandate from congress barring the EPA from ever affecting the outcome of lead in avgas again.

Posted by: Brad Vaught | March 17, 2011 12:15 AM    Report this comment

I didn't think I was complaining, just pointing out the statistical relevance of the data presented.

Posted by: Rob Souza | March 17, 2011 3:06 AM    Report this comment

What you don't know Fraser and Souza is this: For those owners who need a higher octane, would they prefer 100-octane or are they willing to buy a presumably less expensive 94-octane and modify their airplanes.

This is worth knowing ahead of time because if you pick the wrong path, you will accelerate market erosion. The trick is to pick the solution that won't do that. So it's worth asking to what degree owners are willing to modify their airplanes. Answer: Not much.

Further not known is how many of those owners who say they need 100-octane actually have engines approved for 94 or 91/96. Is it 5 percent? 20 percent? 50 percent? That matters, too and would change the opinion of some owners. Have to get to that in a future survey.

Posted by: Paul Bertorelli | March 17, 2011 5:55 AM    Report this comment

I hear too many times that a lower octane fuel will work just fine for most aircraft. If your in the "most" side that's fine but what about the rest. Because I'm not in the majority I don't matter? Lower octane fuel equals longer takeoff roll, slower climb and maybe slower cruise. Big deal unless you are like me and must have all the performance possible. Helicopter flight training and crop dusting. If the majority forces a lower octane fuel on me I'm out of business. Also it would be a boring Oshkosh without all the old round engine warbirds flying around. My point is that the solution shouldn't ground a single aircraft. Can anyone out there prove that my 100LL is causing damage and must be replaced?

Posted by: Bill Albrecht | March 17, 2011 6:46 AM    Report this comment

Mike Krafts vision is still a vision. Still after 20+ years of research there still does not exist any potential single candidate 100 LL fuel replacement which seems to get the necessary approvals. Industry has no wizards. If no single drop in fuel will arise - what will then be the decision of the market?

Posted by: Lars Hjelmberg Hjelmco Oil Sweden | March 17, 2011 7:04 AM    Report this comment

Paul, do you provide a link to the actual survey PDF somewhere, the one you sent me? I do not see this here. I was pleasantly surprised with the strong endorsement for mogas. Given it's available at fewer than 3% of all airports and all the myths that surround its use, support for its use pretty amazing and encouraging.

Posted by: Kent Misegades | March 17, 2011 7:44 AM    Report this comment

"Further not known is how many of those owners who say they need 100-octane actually have engines approved for 94 or 91/96. Is it 5 percent? 20 percent? 50 percent? That matters"

My point exactly.
Polling samples of people who don't really know what's required is a non-starter. It's like watching CNN polls asking people on the street about nuclear energy. GIGO.

I'm afraid that basically the future will NOT be either what we want nor the best technical answer. The future will be pilots reacting to what's available...

Posted by: Mark Fraser | March 17, 2011 7:52 AM    Report this comment

Mike Krafts vision is still a vision. Still after 20+ years of research there still does not exist any potential single candidate 100 LL fuel replacement which seems to get the necessary approvals. Industry has no wizards. If no single drop in fuel will arise - what will then be the decision of the market?

Posted by: Lars Hjelmberg Hjelmco Oil Sweden | March 17, 2011 7:53 AM    Report this comment

We don't need a survey to know that Avgas will be vastly more expensive in 10 years for a whole host of reasons. Then you can add to that $2/gal minimum for taking the lead out. It is just folly to think that will be free.

Kramer's fuel nirvana aside, it is interesting to consider whether the year 2020 will bring clarity of vision (pun intended) as to a bright future or a death from a thousand cuts for GA . The same time frame for the phase-out of 100LL (and the cost of engine changes to accommodate that)corresponds to the time when we will have been mandated to spend thousands equiping our aircraft for ADS-B. It is not hard to imagine the result of being faced with at least two major upgrade expenses that in most cases will have to be made to a fleet that is already arthritic (to say nothing of the pilots) and that will be a decade older than it is now. It just won't happen. I don't imagine that there will be a rush to write checks for the lead-paint versions of Cirruses from China either.

Posted by: David MacRae | March 17, 2011 8:18 AM    Report this comment


Add in the inevitable imposition of user fees (because there will be less Avgas used to tax), security regulations, airport closures, a generally lower standard of living for the middle classes, and it is not unlikely that as a casual activity, GA will wind up at best being split into two widely separate camps of ultra-light/LSA for the masses and exec jets for the uber-rich.

The point is that we tend to see each of these problems as totally separate issues, when there is actually a collective effect. Mostly those problems are reflected in increased costs. We already know that costs are now very close to the point where people are thinking about other ways to spend their money.

I don't have a magic bullet answer to these issues, but we are in a perfect storm for the generation of a radically changed GA environment, if it exists at all. GA needs the recreational aspect to remain viable as an encouragement for the training of pilots for the other necessary economic functions that GA supports.

Posted by: David MacRae | March 17, 2011 8:24 AM    Report this comment

I may have missed it, but was it mentioned that mogas with ethanol is not acceptable to most STC's. It would be foolish to put more mogas at airports if it contains ethanol.

Posted by: Pete Anderson | March 17, 2011 9:31 AM    Report this comment

While I fully understand the threats to GA from the fuel change and other issues, I think there is way too much of a "chicken little" syndrome going on here.
Unless we approach this with a positive attitude that states "GA is an incredible resource that needs to be maintained", then we doom ourselves to negative outcomes.
Attitude is everything when it comes to change and challenges, lets all be more positive, or the EPA etc will simply reacon we are already resigned to losing, and trample us.

Posted by: Steve Elder | March 17, 2011 9:40 AM    Report this comment

Couple of comments: First, I'm unaware of any credible scientific evidence that environmental or health damage has or is likely to occur from our use of 100LL. However, the EPA doesn't care that much about science so they will "purify" our environment, for political if not scientific reasons.

Second, for those who think the 100LL fleet should just buck up and modify their engines to use lower octane fuel, please tell me what modifications are currently available and legal. How likely is it that a company would spend millions to develop and STC such a modification for a small and diminishing aircraft fleet, and how likely is it that the STC would apply across the board to a V-35, a T-210, a Be-58, C414, C421,a Piper Seneca. etc, etc? Further, if all those STC's were in fact developed, how likely is it the cost would be acceptable, especially if it also decreases aircraft performance and thus utility? In the "high performance" aircraft I've flown (V35, B58P, C310, C337,C414, for instance) I've never seen a POH that had alternate power schedules for reduced octane fuel or a notation that it was approved for such.
(see next post)

Posted by: warford johnson 11 | March 17, 2011 9:54 AM    Report this comment

I don't know what proportion of flying (in terms of person-hours flown per year)is instructional/recreational and what proportion is for business/personal transportation, nor what percentage of those two groups are flown in aircraft that could use a lower octane fuel tomorrow, were it available. However, I suspect the bulk of the latter group could not do that either practically or legally. I suspect a cataclysmic regulation mandating the elimination of 100LL without a viable, cost effective, 100 octane alternative, would decapitate the business/personal transportation group, which in turn would inevitably do serious damage to the instructional segment and thus to the recreational segments.

Posted by: warford johnson 11 | March 17, 2011 9:55 AM    Report this comment

That's very interesting. If AirPlains can extend the STC to cover my 414, it doesn't cost an arm and a leg to install on two engines, doesn't void the engine warranties, doesn't require tankering 20 gal of H2O around or otherwise significantly diminish the aircraft's utility, I'll be very interested (and somewhat surprised). Then I'll need to locate the mo-gas on each airport I fly to.

Thanks for the reference - I'll keep an eye on it!

Posted by: warford johnson 11 | March 17, 2011 10:34 AM    Report this comment

The ADI system is projected to cost approximately $15,000 for a twin. Given Lycomings approval of mogas I don't think the warranties would necessarily need to be canceled. Yes you'll have to carry ADI fluid on board but perhaps only ten gallons. That shouldn't have much impact on the utility of the airplane.

Posted by: Todd L. Petersen | March 17, 2011 10:49 AM    Report this comment

John, I see the ADI expert Todd Petersen already replied. The Aviation Fuel Club can help you find mogas, www.aviationfuelclub.org

Posted by: Kent Misegades | March 17, 2011 11:00 AM    Report this comment

Thanks again, guys. Very interesting indeed. And again, I'll be very interested if the STC gets extended to C414's and mo-gas becomes more available. Right now the nearest supplier to me is 100nm away.

Posted by: warford johnson 11 | March 17, 2011 11:44 AM    Report this comment

John, nearly the entire focus of the Aviation Fuel Club is to get mogas onto airfields. Join up (it's free) and we can let you know what is happening in your area. Many airports - from CA to ME - are now in the process of adding mogas as an option. Might be one near your home base, who knows?

Posted by: Kent Misegades | March 17, 2011 11:52 AM    Report this comment

The intention is to extend the STC's to airplanes like Navajo's, Chieftains, Bonanza's, and yes, perhaps the 414.

Posted by: Todd L. Petersen | March 17, 2011 12:19 PM    Report this comment

I concur with the comment about needing proof that 100LL is a health threat. I suspect that the author takes the view that lead is bad. 100LL contains lead. 100LL is bad and must be banned.

Using that same reasoning we can assert that mercury is bad. The new curly fry bulbs contain mercury. The new curly fry bulbs are bad and must be banned.

I am not opposed to reducing or eliminating lead in 100LL. Just don't go down a path that mandates high costs for no discernible benefit when you have not provided anything more than emotion for starting the process.

Posted by: Ronald Lee | March 17, 2011 1:57 PM    Report this comment

I suspect that the author takes the view that lead is bad.

Posted by: Paul Bertorelli | March 17, 2011 2:41 PM    Report this comment

Ron & Paul, nearly all here would agree that lead from aviation is a minor health issue. But try convincing the public. Already one citizen group has formed in Vero Beach, convinced their children are being poisoned by GA aircraft. Which airport is next? If airports would however take some initiative, put in a small mogas tank, they can always provide evidence to the public that they are doing something about lead while waiting on the magical drop-in replacement from Washington. They'll be lowering the cost of aviation too for recreational flyers and flight schools, and that helps everyone.

Posted by: Kent Misegades | March 17, 2011 3:01 PM    Report this comment

I missed the reasons why ethanol is a no-no in aircraft engines. It seems to me that it could be used if fuel lines were improved, as in autos. That's a mighty easy fix, compared to lower compression pistons. And, ethanol's ability to absorb water seems an advantage.

Posted by: Richard Van Pelt | March 17, 2011 3:39 PM    Report this comment

The survey also says many people have already a decision, including me. I purchased an experimental aircraft with a 2-stoke engine that burns mogas. We are betting that pressure from owners of other sports equipment including boats and the need to lower food prices will keep non-ethanol fuel around. We have no confidence that we can stop the EPA from removing lead from avgas. Removing lead from products in other industries has caused many problems. Since removing lead from solder, the electronics industry has experienced much higher failure rates.

Posted by: DANA NICKERSON | March 17, 2011 6:55 PM    Report this comment

Great analysis and comments. Here's my twist on the split into rich jets and lightweights. I think that is likely for other reasons - many of us fly for fun, and some of the newer high efficiency lightweights are pretty efficient, and even sort of practical (for aviation, anyway!), but with a twist: Diesels burning jet A will help supply a signficant part of the 250 hp and up reciprocating market, via STCs. The higher efficiency could easily pay for the engine replacement in a high use aircraft, and increased range at the lower burn is a real plus. I think there will be a real place for Diesels, despite the spotty record so far. But I will really, really miss the Warbirds and the sounds of Merlins and P&Ws at OSH.

Posted by: TOM LUBBEN | March 17, 2011 10:48 PM    Report this comment

"The higher efficiency could easily pay for the engine replacement"

What would be the cost of a brand new 250hp aircraft diesel engine, plus the cost of the STC for your type, plus the cost of airframe retrofits (for fuel, mounts and cowling)?

The "efficiency" is not there. I don't buy a new $40,000 hybrid car to get 10mpg better than my paid-for 96 Honda. Point being that "efficiency" does not matter when it costs more.

Also, the prices of Jet-A is more than either 100LL or MoGas. That means break-even on the swap is even hard for high-use aircraft. The "efficiency" is not worth it.

Posted by: Mark Fraser | March 18, 2011 7:19 AM    Report this comment

The higher efficiency could easily pay for the engine replacement in a high use aircraft, and increased range at the lower burn is a real plus.

Posted by: Paul Bertorelli | March 18, 2011 8:09 AM    Report this comment

"the difference between .36 and .42 SFC"

They both average 0.4 on my calculator.
I agree that the other claims have not panned out either as far as TBO, maintenance, or even vendor support. OEM market has never embraced diesels (even in Europe).

It'd be great if diesels were cheap, available, and fuel was cheaper! I just don't see any of that happening in my lifetime...

Posted by: Mark Fraser | March 18, 2011 9:56 AM    Report this comment

Isn't Diamond fairly committed to diesels?

Posted by: Kent Misegades | March 18, 2011 11:20 AM    Report this comment

The problem with diesels, is the torque. Props can't take it. Maybe someone will come up with one that can, but my understanding is that this is where the problem is.

Posted by: Todd L. Petersen | March 18, 2011 12:16 PM    Report this comment

Horsepower is a function of torque and RPM. If you have an IO-360 turning 2700 RPM and producing 200BHP and a diesel turning 2700 RPM and producing 200BHP, their torque output has to be identical. So any prop rated for the RPM range and horsepower range that a given diesel operates at should have no issues with the torque.

Of course, props mostly are concerned with the dynamic response to the engine and airflow vibration based load inputs. Designing for the torque is simple by comparison. Hence why it's such a big deal to get a new prop approved for any engine and you can't just take a prop off some other engine of equivalent power and RPM ranges as assume it'll be safe.

Posted by: Andrew Upson | March 18, 2011 12:36 PM    Report this comment

Perhaps. But that's not what I've been told by people who are in a position to know.

Posted by: Todd L. Petersen | March 18, 2011 12:41 PM    Report this comment

that's not what I've been told by people who are in a position to know.

Posted by: Paul Bertorelli | March 18, 2011 1:41 PM    Report this comment

We have Super Unleaded MOGAS available at my FBO. A spectrometric analysis is delivered with each load, so that the pilot can be assured of the makeup of the fuel, the Reid Vapor Pressure, and that it doesn't contain alcohol. The retail price is only 50 cents more than the posted price of regular gas at the nearby gas station.

We use it in our own fleet of Piper Warriors--including the 160 h.p. version (we have Peterson STCs). We have never had a case of vapor lock (except at 90 degrees on a 1974 model--this first year lacked the cooling blast tube for the fuel pump--since installed). Engines make TBO without cylinder problems.

If an airplane is going to be left out in the sun in the summer, we will sometimes put 5 gallons of 100LL in each tank--otherwise, straight auto. This is partly prophylactic to insure against vapor lock--and partly because the STC holder mandates a load of 100 every 75 hours.

Despite the availability of low-priced and documented auto fuel, we only sell about 1500 gallons of it a year at retail. Though many aircraft pulling up to the pump have the STCs--they don't elect to use MOGAS. We still have a ways to go to convince pilots that MOGAS is an acceptable alternative.

Posted by: jim hanson | March 19, 2011 3:46 PM    Report this comment

Just finished a day of maintenance seminars. One particular engine overhaul facility went from "No Mogas whatsoever" last year to "If you're gonna use it you're on your own and make sure you get the right octane" this year. As long as this sentiment continues, don't look for widespread acceptance of mogas. I think it is time to have a frank discussion of the advantages and issues surrounding this alternate fuel. Pilots who fly regularly, have STC's, have mogas on the field and who still choose 100LL have way too much money in my opinion - please send some my way!

Posted by: Josh Johnson | March 19, 2011 9:45 PM    Report this comment

Metal props are just fine with diesels, provided torsional issues have been properly addressed. The Junkers Jumo and Napier Nomad were very large 2-stroke diesels that worked just fine with huge metal props.

Posted by: Paul Bertorelli | March 20, 2011 6:47 AM    Report this comment

We have Super Unleaded MOGAS available at my FBO

Posted by: Paul Bertorelli | March 20, 2011 6:58 AM    Report this comment

In his excellent Smithsonian Monograph, The First Airplane Diesel Engine, Robert Meyer observes that the Packard DR-980 didn't fail because it wasn't technically clever. It failed because its benefits weren't outweighed by its advantages: It was heavy, expensive to produce, had lower power density than the Whirlwind it competed against and it smelled bad.

Except for the odor part, not much has changed in 80 years. Thielert, SMA and Delthawk have proven the economy, but not the economics. . The emerging fuel situation may change this, but no one really knows. Just because the Chinese are betting big on diesel, doesn't mean it will happen.

The diesels pencil out impressively. So did the Jumo. But when it got into the field, it didn't do well. My guess is diesel has reached the inflection point, but my guess is no better than Hugo Junkers' and probably not even as good.

Posted by: Paul Bertorelli | March 20, 2011 7:11 AM    Report this comment

"We still have a ways to go to convince pilots that MOGAS is an acceptable alternative." Not among pilots who have been using it for 20+ years, all new LSA & Rotax/Jabiru owners or the shops that look after them. There are two worlds out there, one that has embraced the three-fuel future (Mogas + 100LL + Jet-A), and others who are in denial that it's coming. It's the same reason that Cessna changed their mind and used the ancient Conti O-200D for the C162 instead of the Rotax since Cessna maintenance folks didn't understand the Rotax, and the decision has really hurt the C162's useful load. Now Conti is owned by the Chinese, Van is happy with the Rotax in the very popular RV-12 and the Rotax has a 2,000 hour TBO, burning around 4 gph on cheap mogas. The number of new LSA designs is way over 100 now, and the number of LSA aircraft in our skies has increased by over 20% in the past two years, success older companies can only dream of. Mogas users aren't sitting around waiting to be told what to do by the FAA and Alphabets, I can assure you.

Posted by: Kent Misegades | March 20, 2011 8:30 AM    Report this comment

Paul the Jumo 204 first entered service in 1932. A lot has happened since then in terms of materials technology, fuels and a lot of other things.

Making a straight comparison between this engine and today's engines is like comparing the Jumo 004, the world's first jet engine (Me-262) to today's turbofans.

Even still, the 205's power density of of 0.66 hp/lb, is about 50 percent better than the Thielert 1.7 which puts out 135 hp for 300 lb weight, for a power density of 0.45.

The Napier Nomad had a fuel efficiency of under 0.35 lb fuel/hp-hr, which has only recently been surpassed by high bypass turbofans and is still not matched by any piston engine that I am aware of.

The Nomad was not an opposed piston design like the Jumo. It was fairly complex and the emerging turbine engine sealed its fate.

The Jumo diesel likewise was eclipsed by high output gas engines because the need was for high power warplanes.

Today we need high fuel efficiency using a universal aviation fuel.. Plus low manufacturing cost, simplicity, ruggedness and power density would be good too. The opposed piston 2-strokes is a good bet and that is why quite a bit of development is happening in this area, much of it driven by military.

Posted by: Gordon Arnaut | March 20, 2011 10:01 AM    Report this comment

Btw, there was never any technical issue with propeller vibrations that I am aware of with those diesels I mentioned.

The Jumo diesel is considered "moderately successful" overall by engine historians especially in the civilian role where it powered various models of Blohm & Voss and Dornier small airliners.

Posted by: Gordon Arnaut | March 20, 2011 10:13 AM    Report this comment

The Napier was a licensed version of the Jumo. Both had fluid torsional dampening, along with a quill shaft for drive flexibility (like Continental's Tiara engines). This no doubt explains the success with metal props. Beyond that however they were incredibly (clever, but) complex engines that would have no relevance to what GA needs in today's circumstances. It is dismaying to note that Continental's foray into liquid cooled engines got no market acceptance(nor did their Tiara engines). The success of the Continetal/Lycoming powerplants is largely due to their stone simplicity. Some see this simplicity as an advantage, others decry it as old-fashioned, and therefore undesireable. The world knows how to build complex engines where the rock/hard place squeezes of cost, weight, certification, legacy airframes, low volume production are not overwhelming considerations. Did I mention cost? Conversion of an aircraft from an IO-520 Continental to a similarly powered Diesel will mean in the new, post-100LL reality that there will be little or no value in the "core" of the 520, and the increased complexity of the Diesel will represent a significant delta up-cost, not to mention the cost of airframe mods that will be required, even if Cessna/FAA or whoever were to sign off on them. The value of the average GA aircraft is going to plummet. Where will GA be then? This will be the real economic cost to aircraft owners with the elimination of 100 Avgas.

Posted by: David MacRae | March 20, 2011 1:09 PM    Report this comment

there was never any technical issue with propeller vibrations that I am aware of with those diesels I mentioned

Posted by: Paul Bertorelli | March 20, 2011 1:38 PM    Report this comment

David, every engine with a propeller has to be carefully scrutinized for vibration issues. Prime example is non-counterweighted 4-banger Lycs which are not allowed to operate in a certain rpm band around 2000 rpm.

That's the nature of the beast. A propeller blade being a long slender blade with considerable flex that will whipsaw back and forth with the twisting of the crankshaft caused by power pulses.

Bottom line is that every engine with a prop bolted to it has to have torsional issues addressed, not just diesels like some people are saying here.

A NA diesel actually has lower peak cylinder pressures than a NA spark engine and will actually have lower torque spikes. Much of the reason is that the burn rate of the diesel is much slower.

Thermodynamically a diesel is considered a constant pressure cycle where the cylinder pressure does NOT exceed the pressure reached by compression alone. This does not apply to all diesel engines of course, but spark engines are a constant volume device where burn happens very quickly in a millisecond while the piston is basically motionless at the top. This causes an increase in cylinder pressure of about 5 or 6 times at least.

Posted by: Gordon Arnaut | March 20, 2011 2:15 PM    Report this comment

Bottom line is that a 2-stroke diesel makes the most sense. Opposed piston arrangement is very efficient and light, with a fraction of the parts of a 4-stroke engine because it uses cylinder ports not valves and no valvetrain, like a 4-stroke diesel which is very heavy and expensive because of all the parts.

It may in fact be true that the Thielert engine had very strong torque spikes. This is typical of modern 4-stroke diesels that are boosted in order to try to improve efficiency. That configuration is a terrible idea for an aero engine.

The Wilsch 2-stroke diesel has slightly better power density than comparable Lyc, even though it uses exhaust valve and the required cam train.

the SMA and Thielert and Austro are not the answer. They are heavy, have more moving parts than direct drive spark engine and all of those problems mentioned about converting legacy fleet are true.

A better idea is needed.

Posted by: Gordon Arnaut | March 20, 2011 2:25 PM    Report this comment

Paul, I have to disagree with your reasoning that the Jumo should have lasted into the 50s.

Reason is fuel. Avgas was the standard in those decades at airports. It was not until the turbine era that diesels made any sense, simply due to fuel availability. Sound familiar?

Posted by: Gordon Arnaut | March 20, 2011 2:32 PM    Report this comment

Gord, no argument on the need for testing with specific prop/engine combinations. Just pointing out that Jumo understood the need for dampening way back when, and that the similar arrangement with the Continentals got no traction for other reasons.

I also understand the thermodynamics of the engine types.

Nonetheless, I have to disagree on the complexity issue. For example, having to have two crankshafts, with a gear train between them that no doubt also had to be protected from torque impulses, double the number of pistons, complex direct injection (for which they only claimed 800 hours TBO), etc, makes for an expensive engine. That is what will be the hurdle. Then we get to installation costs and ongoing support. The prospects are daunting to say the least.

Posted by: David MacRae | March 20, 2011 4:16 PM    Report this comment

Gordon, there was plenty of heavy distillate around during the 1950s. Don't forget, the Germans were much bigger into diesel than the U.S. or U.K. Even as early at 1927 in the U.S., fuel availability for the DR950 was not cited as a reason for its failure. It may have actually used kerosense.

Perhaps the bigger driver was that turbojets were in sight and no one wanted to go slow behind a stinky diesel, no matter how economical is it was.(See Packard.) For all we know, it may still be true. But it's technical complexity didn't help its cause.

Also, what's your reference on gasoline engines having lower peak pressures than diesels? All the literature--including DelataHawk's Web site, by the way-- says the reverse. In the test cell, I've seen gasoline engine peaks around 900 PSI, but higher for detonation runs. Diesels generally start at around 2000 PSI. These are post ignition.

I'm reading this in Taylor's Internal Combustion Theory and Practice and Diesel Theory . Can you give me the reference? I'm missing something here. (Not an engineer, either.)

Posted by: Paul Bertorelli | March 20, 2011 5:00 PM    Report this comment

David, I would do an opposed piston engine with a simple helical gear on each crank and a larger one in the middle.

With a short stroke on each piston you could have a high rpm diesel, but with a cylinder volume equal to an engine with double the stroke.

A diesel running at 5000 rpm instead of 2500, but with equal cylinder volume and torque, will have double the power. With the same piston speed which is a diesel's limiting factor due to slow fuel burn. And in a very small package.

I don't see direct injection as a problem. It may have been on those engines in the 1930s. My understanding is that the mechanical high pressure, piston type pump, Bosch pump, is very reliable in all its various iterations. Unit pumps work good too. New technology like the voice coil DI used by Evinrude spark 2-strokes is pretty neat.

Posted by: Gordon Arnaut | March 20, 2011 5:51 PM    Report this comment

Just to mention another possibility that takes legacy fleet into account.

Any gasoline spark-ignition engine can be made to run on heavy fuel with direct cylinder fuel injection. Military versions of commercial outboard engines do this. So do small 2-stroke engines used in UAVs.

DI also eliminates any possibility of detonation because fuel is injected after compression has taken place. Whether or not a retrofit for aircraft recips is economically practical is another story, but it is certainly doable technically.

Posted by: Gordon Arnaut | March 21, 2011 6:47 AM    Report this comment

If the 80% of us who DON'T NEED exotic 100 octane racing fuel would get behind 94UL avgas, 80% of us would wind up with a CHEAPER fuel that is NOT DETRIMENTAL to our engines like the EXPENSIVE 100LL we've been forced to put up with for the past 20 years.

Anybody trying to make a living with a piston engine that needs an exotic 100 octane racing fuel ought to have his head examined.

Anybody else who flies a hotrod that requires exotic 100 octane racing fuel should buy it from the same place NASCAR gets their exotic 100 octane racing fuel and quit making the rest of us subsidize their toy.

Posted by: JON BAKER | March 21, 2011 7:58 AM    Report this comment

Gordon and Paul --

Thanks so much for your insightful discussion of fuels and engine technology. The link to EPI Inc.'s website is amazing !!

I have been approached by an individual interested in converting a Subaru EE-20 Diesel engine for aircraft use: Any comments on the viability ?? (I think it's probably too heavy @ > 300lbs not including accessories or PSRU)

Name EE20
Displacement 1998cc
Maximum output 110kw(150PS)/3600rpm
Maximum torque 350N·m/1800rpm
CO2 emission 148g/km
Compression ratio 16.3
Bore × stroke 86.0 × 86.0mm
Bore pitch 98.4mm
Bank offset 46.8mm
Deck height 220mm
Journal diameter φ67mm
Pin diameter φ55mm
Rod center distance 134mm
Piston pin diameter φ31mm
Compression height 43.0mm
Fuel injection system common rail
Turbocharger variable nozzle turbocharger
EGR water cooled
DPF open
Total length 353.5mm

Posted by: STEVE WENKE | March 21, 2011 10:09 AM    Report this comment

Paul--you asked for our fuel supplier for MOGAS. It's Western Petroleum in Minneapolis--952 941 9090. It comes from the Koch refinery in South St. Paul. Western is the dominant aviation fuel supplier in Minnesota, Wisconsin, Iowa, North and South Dakota--and also distributes to Illinois, Missouri, and Nebraska.

They only use fuel from Koch refining terminal because Koch specializes in aviation fuels--providing most of the jet fuel for Minneapolis airport--also refining 100 octane. They only use Wayne Transport trucks--dedicated only to aviation fuels, and provide a spectometric analysis of the fuel--all part of their quality control system.

There is no question as to the purity and makeup of the fuel--something reassuring to us as the FBO and the airplane owner. A side note: We fuel my wife's car with it. The car developed a problem with starting and rough running. The dealer did all of the "tuneup" things", but after several visits and spending over $800, it still ran rough. "You must just have picked up some bad fuel" they told me. I responded "You picked the wrong guy to tell THAT fairy tale to--I can account for every drop of fuel that has gone into that car for the last 2 years!" They looked further, it was the submersible fuel pump in the gas tank--I got half of the "tuneup" money back.

Posted by: jim hanson | March 21, 2011 11:19 AM    Report this comment

Kent--we DO have a problem in pilot acceptance of MOGAS--though we have used it for thousands of hours, we sold only about 1500 gallons at retail last year--though many aircraft have the STCs, when offered the choice at the pumps, they decline.

Posted by: jim hanson | March 21, 2011 11:19 AM    Report this comment

Regarding the availability of tetraethyl lead and possible second sources-

I too have dealings on Alibaba and find that an initial inquiry is ALWAYS answered with "where?" and "how much?" as it's the beginnings of a commercial transaction that has many unknowns.

The unasked question is "when?".

If you reply with a large enough volume requirement and a solid RFQ, they WILL find a way to make it - eventually - and after you pony up some good faith $$ - then they will tell you the "when".

Just for fun - ask for 1/12th of a years worth of GA consumption of TEL to be delivered POE LA in 90 days. Then tell us the reply.

Oh, and how you are going to get it imported?

Posted by: Walter Freeman | March 21, 2011 11:20 AM    Report this comment

Jon, I think that perhaps you might want to reconsider your statements. The majority of 'working' airplanes are the ones that need 100 octane fuel. 414,421,Cirrus,Barron, etc... Although the fleet size is small, the number of hours and revenue generated is high. Aviation is not a democracy, but rather a collective. If we exclude the most economically significant portion of the GA piston fleet then we, the remainder, will have to shoulder all the cost burden, which will mean higher prices for EVERYTHING. Bottom line is that we can't simply go with your concept of screw them, they're crazy and I'm not going to subsidize them. The fact is that they are subsidizing you and all the rest of us.

Posted by: Ken Anderson | March 21, 2011 11:30 AM    Report this comment

I like the approach these guys have taken - liquid cooling conversion. (www.liquidcooledairpower.com) While it's not cheap at 17k/21k for 4/6cyl Lycs, if incorporated into the cost at overhaul (and eliminating the cost of air-cooled cylinders) the increased longevity and fuel savings should more than pay for itself over time, I believe. I've gone through the entire site and the testing that has been done on their Cherokee 180 showed some impressive results. The stable 190 degree CHTs would enable the use of lower octane fuel (a significant cost saver) and the reduced top-end maintenance and correspondingly higher TBO are very attractive. Plus, the big reduction in cooling drag (even accounting for the small radiator cutout in the cowling) means higher speed with less power, or equivalent speed with lower power. All told, it seems to be a well-engineered package.

The caveat: I've been unable to get any response from these guys through email, and it seems the site hasn't been updated for almost ten years. I understand the problematic economics of an expensive STC for a small fleet of aero engines, but if a dedicated bunch of engineers in CA can come up with this solution, what do you suppose Lycoming or Continental could do?

Posted by: Will Alibrandi | March 21, 2011 11:40 AM    Report this comment

Jim, forums are bad means to communicate at times. My comment was on the acceptance of autogas for those who have used it successfully for many years. FBOs often do not see these people as they self-fuel, becoming difficult in recent years due to ethanol in fuel at the corner gas station. Autogas users generally will avoid large airports like KMSP which is why you'll find the fuel at smaller GA airfields around the Twin Cities such as S.St. Paul, Wipline, Anoka Cty., Stanton, Burnett Cty., & Albert Lea, quite a few really. With avgas now at $7.22 at one of the KMSP FBOs, I'll bet some pilots are rethinking their attitudes about autogas. But it needs to stand on its own feet and make money for the FBO or be seen as an essential service - it will not be a money-making option for every airport or every FBO. One also does not need a 10,000g tank for autogas; many small airports get by with a small fuel trailer or tank. They could sell much more if they advertised it for non-aviation use, too. Koch folks are terrific. I have spoken with them and they are absolutely committed to maintaining a supply of ethanol-free fuel in the Midwest.

Posted by: Kent Misegades | March 21, 2011 11:43 AM    Report this comment

Oh, and how you are going to get it imported?

Posted by: Paul Bertorelli | March 21, 2011 12:49 PM    Report this comment

Thanks for that contact, Jim. I'll follow up with them.

Posted by: Paul Bertorelli | March 21, 2011 12:50 PM    Report this comment

I forgot to mention, mogas would dovetail nicely with the liquid-cooled Lycoming, and according to the LCAP guys, greater thermal stability means the detonation margin is huge compared to an air-cooled engine. In this situation 94UL would be a perfectly adequate fuel.

Posted by: Will Alibrandi | March 21, 2011 12:56 PM    Report this comment

Ken, I'll say it again and I hope is sinks in this time. It's NUTS to try and make a living with a piston engine that needs a fuel so exotic that it's single-sourced and so incompatible that it has to be trucked around instead of pipelined -- and has to be overhauled every 2000 hours instead of 30,000 hours. Anybody doing that needs to buy a calculator and do the math -- and then upgrade to a turbine.

The ONLY reason they haven't ALREADY upgraded is that the Government imposed 100LL on the whole industry 20 years ago, making it barely possible for a commercial operator to limp along without upgrading. Meanwhile, 80% of us wound up with a fuel that actually hurts our engines just so that a few commercial operators wouldn't have to invest in an upgrade that would save them money in the long run anyway.

And Ken, it's NEITHER a democracy OR a collective. It's a MARKET! If the Government would just get out of the way, the problem would fix itself. Lycoming and Continental would certify their low-compression engines for 94UL and modify their high-compression engines to get by on it. The fuel vendors would discover a new market for what is essentially premium car gas. Commercial operators would do what they should have done 20 years ago and make the investment necessary to cut their fuel bills in half.

ALL of us would see our fuel bills come down from the stratosphere.

Posted by: JON BAKER | March 21, 2011 1:17 PM    Report this comment

And speaking of who's subsidizing who -- thanks just the same, but I'd rather have my fuel cost "subsidized" by 300 million cars than a couple of thousand "414,421,Cirrus,Barron...".

Posted by: JON BAKER | March 21, 2011 1:23 PM    Report this comment

JOn, "I'd rather have my fuel cost "subsidized" by 300 million cars" I couldn't agree more, but would never suggest autogas should be the only solution as long as the market can sustain high-octane fuels as it has in motorsports for many years.

Posted by: Kent Misegades | March 21, 2011 1:27 PM    Report this comment


0-360's don't need to be water cooled to use lower octane fuel. They've been STC'd since 1989 to use 91 octane mogas. STC SE2563CE.

Posted by: Todd L. Petersen | March 21, 2011 2:11 PM    Report this comment

Thanks Todd, that's good to know. However, the benefits of water cooling go far beyond the lower octane capability.

Posted by: Will Alibrandi | March 21, 2011 2:29 PM    Report this comment

And Jon, where do you see the capital coming from for these companies to upgrade their fleets. Have you looked at the profit margins in aviation? Have you tried to get a commercial loan to upgrade or acquire an aircraft lately? I have, and I can tell you that there is currently no way to make the numbers work with the slim profits currently existing, and the banks refusing to loan money. I would love to waive a magic wand and make it all better, but darned if I can find one. I would love to just upgrade to a turbine, but since the engine alone would cost more than the whole plane, that's a non-starter too. So that pretty much leaves me in the situation that I will need 100LL if I am going to be able to haul myself coast to coast to do my job. As for aviation being a market, I would disagree with you on that, because I don't know of very many people who get involved in aviation to make money. We are in it because we love it. The only way to make a small fortune in aviation is to start with a large one.

Posted by: Ken Anderson | March 21, 2011 2:50 PM    Report this comment

Also, even if Lyco and Cont re-certify their engines, who will pay for the work? We will. Aircraft owners who are already on the brink of economic ruin. As for cutting fuel bills in half, I don't know where that number comes from. Can you name a single turbine aircraft that has lower operating costs than a turbocharged mooney? I can't think of one. As for the EXOTIC label, Avgas is hardly an exotic fuel. It is a specialized fuel, true, but not EXOTIC.

Posted by: Ken Anderson | March 21, 2011 2:56 PM    Report this comment

"...a fuel so exotic that it's single-sourced..."

I think you will find that there are multiple refineries producing avgas

Posted by: Ken Anderson | March 21, 2011 2:58 PM    Report this comment

As for cutting fuel bills in half, I don't know where that number comes from.

Posted by: Paul Bertorelli | March 21, 2011 3:30 PM    Report this comment

"Collective" is exactly the right word, if for no other reason the the camaraderie we share as aviators.

And yeah, it's discouraging to hear a "to hell with those guys" sentiment.

As for the mythical free and honest market, well that is what the plutocrats who run this country would have us believe, now that they have irretrievably rigged the system in their favor.

Posted by: Gordon Arnaut | March 21, 2011 4:51 PM    Report this comment

Adding to what Gordon said, the big show stopper in converting that diesel would be a gearbox that could handle the torque to the prop. These are difficult enough in gasoline engines in a nightmare in diesels, as Thielert discovered.

Doing it one off is just a black hole when you consider that an O-320 will do what the engine can...only better.

Posted by: Paul Bertorelli | March 21, 2011 5:08 PM    Report this comment

I agree. A propeller gearbox is never a no-brainer.

That is one of the reasons I like the opposed piston arrangement. You have two very short crankshafts on each end, which means very high torsional stiffness and the crank natural frequencies will therefore be well above the operating range.

Since you need to gear the two cranks together anyway, you just put a larger gear in the middle and bolt your prop to that.

You can arrange this engine horizontally, so it would be able to fit nicely into the typical light plane. You would have an engine of two cylinders with the displacement of a 4 banger, or a 3 cylinder with the displacement of a six.

Being a 2-stroke, you would have the same amount of power pulses as a 4 and 6 cylinder four-stroke, but with a crank of half the length. Also half the stroke so you could rev it twice as high with the same piston speed!

This is the really big factor that would let such an engine make impressive power density. Make the engine spark ignited, NA, and Bob's your uncle. Run any fuel you want and get fuel specifics at least on a par with today's recips.

Posted by: Gordon Arnaut | March 21, 2011 5:54 PM    Report this comment

Will, I had a look at that liquid cooling conversion for Lycs website. While it is true that liquid cooling can help reduce thermal stress on the exhaust valve, the claim that liquid cooling of the same engine results in less cooling drag is total malarkey.

Here's why. An engine's heat balance is like this: 30 percent of the fuel's heat energy goes to making power; another 30 percent goes out the exhaust pipe; about 10 percent goes to friction and pumping losses; and about 30 percent of the heat energy is rejected to the coolant.

Now that is for an engine running at high power; a car engine cruising down the highway will reject over 50 percent to the coolant.

Now here is the key point. changing to a liquid coolant does NOT change the engine's energy balance. You are still putting the exact same amount of heat into the coolant and that must be transferred to the air either way, whether by fins on the engine or by fins on the radiator.

Since convective cooling is a function of coolant mass flow and fin surface area, the fin surface area of the radiator must be equal to the fin surface area of the air-cooled engine of the same type in order to dissipate the same heat---since the mass flow does not change, being dependent solely on airspeed.


Posted by: Gordon Arnaut | March 22, 2011 5:53 AM    Report this comment

The only way to reduce cooling drag is to REDUCE the amount of heat being rejected to the cooling system. Generally that means finding a way of dumping more heat out the exhaust pipe, instead of letting it heat up the exhaust valve and cylinder head.

An example of this is the piston ported 2-stroke engine (or rotary) where you do not have an exhaust valve in the stream of the hot exhaust, you simply have a hole that dumps the heat out the cylinder.

Result is that less heat is transferred to the exhaust valve (which absorbs about half of the heat energy rejected to the cooling system btw) and from there to the cyl head and thence the coolant.

Since you are not doing any of these things, the exact same amount of heat is being transferred to the liquid and must be transferred to the air by the rad. This means exactly the same fin area on the rad as on the engine, and exactly the same amount of friction loss.


Posted by: Gordon Arnaut | March 22, 2011 5:58 AM    Report this comment

The only thing you have accomplished is to waste a few hp on driving a water pump, and add a bunch of weight, cost and potential failure points.

The reason I like the opposed piston config is because it rejects very little heat to the cooling system. Reason is that there is no cyl head (the combustion chamber is the space between the two pistons meeting head to head in the middle of the cyl).

That means there is less surface area to transfer heat to the engine metal. Plus you have very large cylinder ports for exhaust so most of the heat is just dumped right out. A rotary is similar, but its rotor has a higher surface to volume ratio than a cylinder and absorbs more heat.

An OP 2-stroke is the LOWEST heat rejection recip engine I know of. How much? As much as 2/3 less heat rejection to coolant, compared to conventional 4-stroke engine of same power. This means you save about 2/3 cooling drag.

That is real, not fairy tale like this liquid cooled Lyc story.

Posted by: Gordon Arnaut | March 22, 2011 6:10 AM    Report this comment

"A big part of the difficulty in addressing the fuel replacement issue is the amount of disinformation, misinformation and just general lack of knowledge about fuel"

Paul, you just made my point. That is precisely the reason that your survey has no merit. You cannot get "real numbers" because most pilots are not engine mechanics. You got a sampling of superstitions, not real information on the topic.

Posted by: Mark Fraser | March 22, 2011 7:32 AM    Report this comment

Gordon, I follow your explanation, but if liquid is a more efficient conductor of heat (vs air) wouldn't that mean a smaller total cooling area of a radiator will do the same work of a larger cyl head fin area?

Posted by: Will Alibrandi | March 22, 2011 8:01 AM    Report this comment

Will, no because the more effective heat transfer of water (convective when we are talking about moving fluids like water and air, not conductive), applies only to the part where the heat is passed from the engine metal to the water.

The part where the heat is transferred from the water to the air, by means of the rad cooling fins, is exactly the same. Same amount of heat has to eventually be transferred to the air is the key point.

Look these guys I'm sure know enough about heat transfer to know what I am saying is true. They are just trying to fudge things hoping people will not notice.

Fact is that you can decrease cooling drag on most recips by optimizing the flow around the engine, such as using plenum rather than pressure cowl. So they are saying well we can design a rad duct that will do a better job of this.

Maybe so. But it will be no better than a well designed air-cooled engine cowl. Apples to apples...

Posted by: Gordon Arnaut | March 22, 2011 8:21 AM    Report this comment

And just to add that reducing thermal stress on exhaust valve is good thing, no question. Water cooling will do this.

Big question is whether that really equates to the kind of extended life, 5,000 hours, that they are talking about. I will believe that when I see it.

My understanding is that careful and regular inspection of exhaust valve can extend air-cooled engine life impressively, provided the engine is also operated properly by the PIC.

On balance my opinion is that the tradeoff with water cooling is not worth it. If you're going to reinvent the lightplane recip, best bet is to not have an exhaust valve in your engine to begin with...

Posted by: Gordon Arnaut | March 22, 2011 8:35 AM    Report this comment

That is precisely the reason that your survey has no merit.

Posted by: Paul Bertorelli | March 22, 2011 9:01 AM    Report this comment

Paul, I agreed with you and your assessment of lack of general knowledge in the aviation community on fuel requirements and engine technology. Surveying such a community (if it's a good survey) reflects that. Therefore I said it's useless data unless the first step is toward pilot education.

If the only answer you hold is that all of GA lives or dies by selling 100 octane then the number of "right questions" you'll consider acceptable is awfully limited indeed.

Posted by: Mark Fraser | March 22, 2011 11:15 AM    Report this comment

I've mentioned on other threads but I still don't see the math that gets to boutique being better than modding.

From Vref a Cessna 402 averages 625 hr/yr from birth. Assume 40 gph and that's 25,000 gal/yr. Now Gami projects their fuel will come in at +$0.50/gal. So that's an extra $12,500/yr for our hypothetical operator which Mr. Bertorelli has said is negligible, something to the effect of in the noise of normal price fluctuations. Mr. Peterson comes along and says he can mod out from the 100 LL requirement for $15,000 one time. Now the argument switches to mods are mortal financial wound, operators are barely scraping by and will just park their planes.

I don't get it.

Right now airnav says 100 LL is +$1.40 from mogas, nationwide average. Add GAMI's estimate of no-lead cost premium, it will widen to $1.90. That means a 402 operator can save $50,000/year on fuel costs with a one time $15,000 mod from Mr. Peterson. Even if you assume least-benefit case that the tradeoff is between 94UL at current 100LL price and 100UL at $0.50/gal, the 402 operator saves $12,500/year for a one time $15,000 mod. Why would any commerical operator that can use a calculator choose boutique fuel option over the mod? They won't imho in a level competition. They chose the higher cost boutique gas option because there is nothing else available. Not because it makes any kind of economic sense.


Posted by: BYRON WARD | March 22, 2011 1:14 PM    Report this comment

I completely understand that for personal planes that need 100 LL (like mine...) investing $$ now that might break even after a lot of years doesn't look nearly as palatable. But I'm not sure we get a vote. If commerical operators start abandoning the 100 LL ship whether they go to Jet A or mod out to lower octane gas, either way owner flown guys will be dragged along by the Golden rule.

Posted by: BYRON WARD | March 22, 2011 1:14 PM    Report this comment

I don't get it

Posted by: Paul Bertorelli | March 22, 2011 2:21 PM    Report this comment

Ok my mistake. But Mr. Peterson doesn't need 94 UL anyway...Substitute 91/96 UL for 94 UL, or whatever you want to call 100 LL minus the LL.

Posted by: BYRON WARD | March 22, 2011 2:47 PM    Report this comment

91/96 is essentially 94UL.

You may be thinking mogas, which should always be--one hopes--about a $1.50 Delta with avgas.

Posted by: Paul Bertorelli | March 22, 2011 5:46 PM    Report this comment

Not thinking mogas, thinking 100 LL exactly as it is today, but minus the lead, whatever octane that might be.

I was really just trying to make the point that even with the relatively small delta that GAMI projects of $0.50/gallon increase from current prices, it makes more sense for the people that burn the most gas to mod for lower octane instead of accepting a new, higher priced alternate.

Over the long run it makes more sense even for owners to mod vs higher priced gas but because hours are low payoff is long and no-one is interested in investing $$$ that only pays off 20 years down the road.

I say it doesn't matter because private owners are at the mercy of commercial operators, who burn a lot of gas and also have to look at the bottom line.

I'm also highly skeptical of drop in 100 UL at minimal cost increase given several decades of coming up empty from the most aviation-fuel-knowledgeable people in the country. Probably the world. Extraordinary claims etc. When a real fuel producer invests money in locking up rights to one of the new ones I'll start reeling in the cynicism.

Running a lab fuel in the lab, even on experimental planes is nice, but it's been done more than a decade ago and what do we have to show for it?? A 300 page report that's about it. Too bad my plane doesn't run on committee reports. I'd be good for a 100 yrs.

Posted by: BYRON WARD | March 22, 2011 10:48 PM    Report this comment

There is a big difference between the 91/96 UL from Hjelmco and the proposed 94UL. The Hjelmco fuel has been produced for 20 + years, flown in thousands of aircraft for millions of flight hours. Anyone starting from zero with a 94 UL a fuel which has flown some houndred hours has to learn to master the difficulties to make a fuel which the fleet will accept and which constantly gives TBO of about 3000 hours.
It is not that easy.

Posted by: Lars Hjelmberg Hjelmco Oil Sweden | March 23, 2011 2:31 AM    Report this comment

There is a big difference between the 91/96 UL from Hjelmco and the proposed 94UL

Posted by: Paul Bertorelli | March 23, 2011 3:57 AM    Report this comment

Paul -- the 94 UL and our 91/98 UL (91/96 UL) yes have about the same properties if you measure them as per AVGAS standard D910.
However standard D910 does not adequately control an unleaded AVGAS so our unleaaded fuel contains proprietary capabilities - (still within the D910 standard) which anyone else that would like to produce any other unleaded AVGAS (such as 94UL) don,t have or will have to find out through "trial and error" in the same way we did
about 25 years ago.
As you understand Hjelmco cannot disclose these proprietary knowledge here - they carry a substantial economical value and many oil companies would certainly be prepared to pay a fortune to get hold of these data.

Posted by: Lars Hjelmberg Hjelmco Oil Sweden | March 23, 2011 9:09 AM    Report this comment

Yeah...but 94UL is an approved ASTM fuel so aren't we talking about the difference between Shell Platformate and Chevron Techron?

Posted by: Paul Bertorelli | March 23, 2011 10:31 AM    Report this comment

our unleaaded fuel contains proprietary capabilities ...

I guess that if we don't want to pay for the special sauce in Hjelmco's 91/96, couldn't we just add a bit of Marvel Mystery Oil to a tank of 94 and get pretty much the same performance? :-)

Posted by: David MacRae | March 23, 2011 12:00 PM    Report this comment

Paul - as far as I remember the 94UL is still an approved ASTM test fuel specification for engine calibration and FAA certification and so is also the Swift fuel.

Posted by: Lars Hjelmberg Hjelmco Oil Sweden | March 23, 2011 2:53 PM    Report this comment

I'll bow to your knowledge. I thought it had final approval.

Posted by: Paul Bertorelli | March 23, 2011 4:06 PM    Report this comment

David MacRae, We sell the Hjelmco 91/96 UL and 91/98 UL at a lower price than 100 LL
and have done so continiously for 20 + years.
It is mirage to think that all the inventors working on unleaded fuels will do all this work free, take all the costs free and all the liability issues free of cost for the end-user. If that was the general opinion among consumers you will not see any new fuels on the horizon and all the investors will turn their eyes on something else.

Posted by: Lars Hjelmberg Hjelmco Oil Sweden | March 23, 2011 4:33 PM    Report this comment

Lars, Take a breath.

Just trying to inject a little levity in here.

I spent my professional life in R&D and understand the concept of intellectual property. See my post on March 17th.

That said, there is a subtle line that can get crossed by people who engage in endless self-promoting on these forums.

If the shoe fits....

Posted by: David MacRae | March 23, 2011 5:46 PM    Report this comment

Kent--"FBOs often do not see these people as they self-fuel, becoming difficult in recent years due to ethanol in fuel at the corner gas station. Autogas users generally will avoid large airports like KMSP which is why you'll find the fuel at smaller GA airfields around the Twin Cities such as S.St. Paul, Wipline, Anoka Cty., Stanton, Burnett Cty., & Albert Lea,"

I AM the FBO at Albert Lea--that's why I mentioned that though many people have the STCs--that certified MOGAS is readily available right next to the avgas pump, and that it is a dollar cheaper than 100LL, airplane owners are just not using it. We retail only 1500 gallons a year. Obviously, there are a lot of people out there that don't believe in it. My question is WHY? My thought is that pilots feel uncomfortable using a product they don't know--and if that is the case, ANY "replacement" for 100LL will have the same problem.

We have used auto fuel for almost 10,000 hours in our fleet, with no significant problems--obviously, we believe in it.

Posted by: jim hanson | March 23, 2011 5:57 PM    Report this comment

I haven't seen much discussion of Very Low Lead 100. As brought out elsewhere, there is no mandate YET for COMPLETE ELIMINATION of lead by the EPA--only a discussion of how to mitigate it.

What ARE the chances of a VLL-100 passing muster with the EPA? What percentage of lead would be eliminated with a switch to VLL?

If the total amount of lead could be demonstrated to be very low, and no practical alternative exists, EPA could solve the equation overnight by simply stating that VLL will be approved for the next 20 years--and after that, a new fuel will have to be found. That gives the big-engine, high volume users time to act, and allows full testing of alternatives. Is 20 years the right time frame? I think so--it will allow nearly all engines to reach TBO during that time--and it should be remembered that the whole 100 octane issue has raged for the same length of time. Twenty years gives owners a time to PLAN, and to be convinced that any alternative fuels are acceptable. We could also help our own cause by encouraging anyone that CAN burn auto fuel to do so--further mitigating any lead issues.

As so often happens with government, we got INTO this mess with a stroke of the regulatory pen, and the same pen can be used to SOLVE the situation.

Posted by: jim hanson | March 23, 2011 6:21 PM    Report this comment

David - if you feel so - you are right - my time is probably better spent elsewhere

Posted by: Lars Hjelmberg Hjelmco Oil Sweden | March 23, 2011 6:26 PM    Report this comment

Jim - As to why more people don’t burn mogas at Albert Lea & elsewhere, perhaps a great many aircraft owners are still intimidated by the disclaimers that have been printed and reprinted, over and over, warning against using auto fuel. It started in the 1950’s, when there were plenty of reasons to stick with avgas. Then gasoline changed in the 1970;s and the STC’s followed in the 1980’s. When they came out it was just about the same time that all of the hard hitting lawsuits were making the news. OEM’s & oil companies were in panic mode to deflect liability from any source, issuing repeated warnings against auto gas at the same time we were trying to promote it. Hence a lot of confusion was sown. I think that still has a lot to do with it. Today we have ethanol to worry about. People are justifiably cautious.

Posted by: Todd L. Petersen | March 23, 2011 7:46 PM    Report this comment

Stick around Lars.

Posted by: Todd L. Petersen | March 23, 2011 7:47 PM    Report this comment

Why aren't airplane owners using mogas? I think because they lack a proper understanding of the basic technical issues.

The aviation media should be doing a better job in explaining these things. I remember a couple of years ago, one of the magazines ran a story about mogas that managed to get every technical issue wrong. Basically a rehashing of old wives tales and some things that might have been true in the 1960s, like vapor pressure levels.

I was going to write a letter, but it would have had to be a whole article in itself to straighten out the mess. Good to see things get properly hashed out in a forum like this.

Posted by: Gordon Arnaut | March 23, 2011 7:52 PM    Report this comment

Yeah please don't go anywhere Lars. I want the guy with a real fielded solution commenting!!

If someone was faking who they are or not mentioning some connection to a project I'd have an issue about it but that's just not the case here.

Posted by: BYRON WARD | March 23, 2011 11:05 PM    Report this comment

Todd, that's why I think Lycomings decision to switch from "it is not permissible in any instance to use autofuel in aircraft engines" (1070 rev P) to allowing autofuel in their last revision of the fuels service instruction (1070 rev Q) is a huge deal. It got zero coverage in aviation press though so far as I can tell

Posted by: BYRON WARD | March 23, 2011 11:15 PM    Report this comment

Oops I don't know why it dropped the quote. I was responding to Todd "As to why more people don’t burn mogas at Albert Lea & elsewhere, perhaps a great many aircraft owners are still intimidated by the disclaimers that have been printed and reprinted, over and over, warning against using auto fuel"

Posted by: BYRON WARD | March 23, 2011 11:16 PM    Report this comment

Gordon, I'll tell you why the aviation press doesn't do more coverage on mogas. Because getting at what passes as reliable truth is all but impossible.

You can get sharply conflicting information from engine manufacturers, airframers, refiners and the self-interested people pushing mogas. So the problem becomes, whose biased version of "reliable information" do you wish to believe?

My response to this has been to survey owners using mogas, of whom there are not many anymore. Although this has its own biases (because they tend to be the true believers), it didn't turn up a lot of complaints or problems.

It did confirm supply chain issues. It did confirm ethanol contamination issues. These are not trivial problems.

Posted by: Paul Bertorelli | March 24, 2011 8:39 AM    Report this comment

I have a reasonably good grasp of the technical issues and I tilt to not using mogas primarily because everywhere I have seen it, it is unbranded. For a $1.50 a gallons saving on five gallons an hour and 20 gallons a month, I'm just not interested. Many, many people are in the same situation.

I would change that tune, however, if (a) the industry got behind the idea of mogas and certain elements of it stopped raising technical issues, however valid or not and (b) suppliers didn't raise liability issues and (c) I could buy it from a branded pump with a spec analysis stuck right on in a weatherproof sleeve to assure no ethanol content. That last one is a biggie, although not for Rotax owners.

"Branded" doesn't mean Shell, or Chevron or Exxon, but a name on the pump that says someone is standing behind this product, it's not some below-the-radar bootleg deal and someone is assuring it has the octane and no ethanol through an assured supply chain.

The new U-fuel Sport Fuel initiative does this or if it doesn't, it should. It's a step in the right direction, although it may face significant market challenges.

Posted by: Paul Bertorelli | March 24, 2011 8:53 AM    Report this comment

Last, self-promotion on this forum. I have exchanged e-mail in the background about doing this.

You are free to argue the benefits of your product here. Want to add links to a web site? Be my guest. Happy to have readers have the information.

But we do ask that you identify yourself, so that readers--and we get hundreds a day who are new--will know that you are providing information from a stance of self-interest and they can then judge it accordingly, good, bad or indifferent.

I have yet to ban anyone and would be loathe to do so. But if information is coming from a source with a commercial interest, readers should know this.

Make sense?

Posted by: Paul Bertorelli | March 24, 2011 8:59 AM    Report this comment

Paul, what you're saying confirms what I wrote regarding why some pilots are rejecting mogas, conflicting information, and deliberate disinformation tend to cause confusion. I just received a letter this morning from a pilot whose mechanic is dead set against mogas in his 80 octane engine because the octane rating methods of the two fuels are different. Of course they're different but it doesn't matter to the engine. Yet some of the industry statements against mogas try to make the point that it does, even in an 80 octane engine. What's a pilot to do? Well if he only flies 50 hours a year, he burns avgas so he doesn't have to worry about it. A 200 hour a year pilot does his homework and figures it out. Is my information biased? Of course it is. Is it false information? No it's not, if it were I'd have never been able to obtain the STC's in the first place. You don't just fill out a request to get an STC you have to test for it. People tend to forget that.

Posted by: Todd L. Petersen | March 24, 2011 10:10 AM    Report this comment

And Mr. Noel, yes you're right. The Lycoming services letter was indeed a big deal, which was unfortunately largely ignored by the press.

Posted by: Todd L. Petersen | March 24, 2011 10:23 AM    Report this comment

Paul, I'm with you on the disinformation. General rule of thumb: the bigger the outfit, the bigger the whoppers they will tell.

Now about the ethanol, which you describe as the "biggie." I think you hit the nail on the head, and this whole thing makes no sense to me, although I am not a fuel expert by any stretch of the imagination.

Here are the facts as far as I can tell, and I will appreciate being corrected if my info is wrong. The FAA does not allow ethanol in mogas for airplanes and I think Todd's STCs reflect that.

Question: Why not? Adding 10 percent Ethanol instead of MBTE has a number of pluses which I will not get into right now. The only minus I am aware of is the corrosion issue, which is not a big deal with the small amount, plus corrosion inhibitors can take care of that.

Now I'm not taking any sides here and trying to boost ethanol, which I generally oppose because it is a big political lie that is meant to enrich (through ag subsidies) a particular interest group.

But reality is that is what is available universally. Rotaxes run just fine on it and it would seem to me that it would make things much easier if the exact same mogas that is available at the filling station is also available to the low output lightplanes that can run well on this grade of fuel.

Posted by: Gordon Arnaut | March 24, 2011 2:44 PM    Report this comment

Actually, the Rotax 912s are approved in E10 generally and in a number of LSA airframes. Not sure if that applies to the FAR 33 version of the engine. In any case, operators are using it.

Cessna did a big research study on ethanol and came down flat and hard against it. I suppose it could re-opened, but I doubt they would roll over on it due to liability worries.

In practice, people are using E10 because I heard from at least half a dozen. They are opening flaunting the limitation of the STCs. Ethanol's hygroscopy can be, but isn't necessarily always, a real issue. Here's a quote from one owner:

"Flights of longer than four hours can result in gascolators being completely full of water upon landing. I've kept company with many 172 pilots over the last 8 years who are using ethanol blended fuels because they can't get pure gas in their states. They report the same results: just be extra cautious when you sump the tanks, and there are no other adverse effects. This is with blends in the 3-10 percent range which appear in most northern states."

Posted by: Paul Bertorelli | March 24, 2011 3:16 PM    Report this comment

This just serves to further highlight the confusion and distrust over avgas. On the one hand, a credible report saying thou shalt not, on the other, a flight school in California running a fleet of Tecnams on E10 because they can't get anything else.

Posted by: Paul Bertorelli | March 25, 2011 5:36 AM    Report this comment

Gordo, you're an engineer, it would be useful to look up the compatiblity of various 0-ring and other rubber products used for fuel bladders and hoses with ethanol.

I don't know what materials might be where in either of my planes, so I'd rather not put ethanol there. Obviously something is OK with the millions of autos out there, but....?

I also avoid issues by using 100LL in my sports car and motorcycles for winter storage.

Posted by: Edd Weninger | March 25, 2011 2:06 PM    Report this comment

I made a comment when I responded to the poll that Paul should have asked responders how much fuel they burned per year. I thought it interesting that an FBO reported that he sold 1,500 gallons of mogas over a year. Man, I'd hate to pump any of that into an airplane if the storage tank was 3,000 gallons.

I burn almost twice that much of 100LL per year. I'm not bragging, and have cut back significantly due to the fuel cost, but it puts certain ideas into perspective.

Posted by: Edd Weninger | March 25, 2011 2:14 PM    Report this comment

You use 100LL in a motorcycle? Nothing too new, I guess, that might have a converter. Still, kinda makes a mess of the plugs, doesn't it?

Posted by: Paul Bertorelli | March 25, 2011 2:33 PM    Report this comment

1979 Honda CBX bought new, still ride, no problems with carbs or plugs. In fact, as I think about it, plugs might have been changed once only?

I put the 100LL in at the time of winter storage, otherwise use AZ mogas (which sometimes does and sometimes does not have ethanol and I don't want to test for)

Posted by: Edd Weninger | March 25, 2011 2:44 PM    Report this comment

Edd, there's a few guys on those Van's threads that have researched this quite a bit. I think there's only a few pieces in the fuel system that are rubber, which is incompatible with alcohol.

Also tank corrosion issue, which some guys say is a non-issue, but others are using alodine on the aluminum and maybe some other coatings.

Paul mentioned Tecnams and I know a few guys with those and they all use the ethanol blend gas, no problem (rotax engine).

From what I hear phase change is an issue only if you let water leak into your fuel tank, by rain, say. Otherwise the condensation is not enough to make the fuel and water separate.

I think with cars a couple of things to remember. One is that the fuel injection returns a fair bit of fuel to the tank and so keeps everything mixed. As long as things stay mixed no problem, it's when your engine ingests a slug of pure water or alcohol that things get bad. Again not trying to promote it by any means, just looking at reality.

Posted by: Gordon Arnaut | March 25, 2011 7:35 PM    Report this comment

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