# Engine Oil Design

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#### Dan Thomas

##### Well-Known Member
Not all home builds require large bore/hp engines - the 100 +/-hp market (in Australia) is dominated by Rotax & Jabiru. I would speculate that this remains true for the rest of the World, except for USA
So Australians and the rest of the world's homebuilders, outside of the US, have the money to buy brand-new Jabirus and Rotaxes?

Prove that.

#### Skippydiesel

##### Well-Known Member
Count the number of homebuilt in the US, and count the number in the rest of the world. Compare.
Where would you find that sort of information (probably have to combe through each countries aircraft register.
I don't think there is any doubt that the USA represents the largest single aircraft market (one country) in the World but whether this is more or less than the rest of the World combined - no idea.
The Europeans & Scandinavians are very active - Australia & New Zealand do well, with a small population (combined less than your larger cities). I know of builders in some of the S. American countries , Canada, Ireland occasionally hear of people in Asia & Africa - how this compares with the US ?????
If your point is that the largest market rules - unfortunately this is often true. This is not necessarily a good thing and in the case of aviation, I feel that the US domination is actually bad, stifling innovation in both airframe & engine development (as always there are exceptions ).
In my humble opinion the leaders in light aviation are the Europeans (with the Boing mess, this may also apply to large transport aircraft).

#### Skippydiesel

##### Well-Known Member
So Australians and the rest of the world's homebuilders, outside of the US, have the money to buy brand-new Jabirus and Rotaxes?

Prove that.
What makes you say that? We are much the same the World over - only the population numbers differ. Like you we will have builders who are wealthy/lucky enough to purchase new but many will go the mid hour engine to the over TBO but still tests good.
Some think purchasing a new Rotax is a mugs game, as preloved examples will reliably deliver the hours of enjoyment that the builder is looking for, at a much lower acquisition price.
Jabirus are by a considerable margin the cheaper engine - don't know if this holds good for those purchasing outside Australia/NZ.

#### gtae07

##### Well-Known Member
This may be so in many instances however it seems clear (to me at least) that the retention of what I see as dinosaur engine technology and its related need for leaded fuel, is not so much being driven by the market, as the marketeers (vested industry). Sure there are other factors at play eg the fear of litigation/being sued (an American phenomena that has slowly infected the rest of the free Word) leading to development stagnation ie legally keep you head down (take no risk) stay with the known, however ridiculous that may be.
A fair chunk of that is perverse regulatory incentives. In true government fashion, the FAA set rules effectively saying "new stuff must meet the latest and greatest rules" with the expectation that everyone would do what they wanted, and the constant churn of new developments would lead to ever-increasing levels of safety. Things didn't work out that way...
- The technical requirements (for airframes and engines) did continue to tighten up and improve... but they were overwhelmingly driven by the needs of commercial operators and larger aircraft. And under the FAA's "one size fits all" application of the rules (yes, I realize there's a difference between Part 23 and Part 25, but all this happened within Parts 23 and 33 too because of commuters and small business aircraft) new spam cans and their engines would have to meet the same standards as much larger aircraft, even though those rules didn't make sense at the light airplane level. Tighter requirements = more cost.
- The FAA's requirements for "means of compliance" and "showing compliance" ratcheted up, too, independent of the actual regulations themselves. The standards of "here's what the regulation means" and "here's how you test it" and "here's the paperwork you need to generate" all increased.
- Since certifications don't expire, and you don't have to update things that don't change, there's an incentive (which increases with the age of the design) to continue to reuse the existing off-the-shelf design/equipment instead of developing something new. Why spend a bunch of time and money making something brand new when you can just pick something already in use? The 737 MAX is the ultimate end game of this, but it's also a big reason why so many new certified aircraft continue to use air-cooled Lycoming/Continental installations with magnetos and carbs/mechanical fuel injection.

Much like the Light Sport rule, where the FAA intended and expected LSA's to just be mostly "fat ultralights" well within the performance specs and used for training Part 103 pilots... and everyone else looked at LSA's as "how can I fly a 'real' airplane without a medical?" and pushed for designs up to (or beyond!) the limits. Anyone who's spent time around real people in aviation could have told you that's what was going to happen...

The reason for the prevalence of O-290/320/360/540 type engines in (US designed/built) homebuilts is not "Americans want these engines" so much as those were the available engines when the kit aircraft market really took off. When the market for new light GA aircraft diminished, there was a glut of used aircraft on the market, and that has satisfied GA demand for a good while. Run-out or salvaged engines from that giant spam-can fleet could be obtained cheaply, and so the homebuilt designers built the airframes around those engines.
In recent years the once-plentiful supply of used/run-out engines has declined, so prices for them have risen.

To the best of my understanding, as long as you are not intending to hire out your RAA (factory built) aircraft and can satisfy the authorities that you have the expertise necessary (pass an exam), you may do all routine servicing/maintenance.
Factor built aircraft will loose their "certification" (not like GA Certified Aircraft) if the maintainer uses non factory supplied/approved parts or materials. The owner of such aircraft may also reduce sale value, if he/she can not demonstrate that the aircraft has ben maintained to a high standard - this may lead many owners to use the services of a LAIM (often not a great idea) or a certified RAA professional maintenance provider.
We do have a homebuilt/experimental category but they are never approved for commercial use - qualified owners are able to perform all maintenance tasks.
RAA aircraft were, until recently limited to 600kg take off weight (slightly higher if a float/amphibian or fitted with a ballistic parachute). The TO limit has recently been raised to 750 kg. We are also allowed CS props, retractable undercarriage and have no practical speed limit. Limited to a single reciprocating engine (no jet/turbines), max 45 knot stall (just be upped to ?), no aerobatics and may have restrictions on entry to controlled airspace/overflying populated areas.
Ah, so RAA is roughly (if you squint a bit) comparable to LSA in the US. Nice! Though I was thinking you meant something more like Canada's "owner maintained" program, or the proposed Primary Non-Commercial category in the US. Still, neat that there's flexibility...

If your point is that the largest market rules - unfortunately this is often true. This is not necessarily a good thing and in the case of aviation, I feel that the US domination is actually bad, stifling innovation in both airframe & engine development (as always there are exceptions ).
In my humble opinion the leaders in light aviation are the Europeans (with the Boing mess, this may also apply to large transport aircraft).
Designers in Europe are operating in a much different environment, in many ways.
The US had the postwar boom and surplus pilot population that led to an explosion in light GA pre ~1970, leading to the glut of used airframes mentioned above. In many ways we have been coasting on that for decades.
Europe had no such GA boom decades ago, so there's less institutional inertia. Light GA hasn't been seen as an instrument of travel in the same way it was/is in the US (and to some extent Canada), and they're also in an environment with more pressures towards fuel efficiency/operational cost over performance/payload/range/speed like many US designs. That's put more emphasis on smaller engines like the Rotax family, and on smaller composite airframes.
From personal experience working with both, the European regulators also seem easier to work with in many ways. Their rules may be more strict and we in the US enjoy much greater freedom of operation in many respects, but the typical European response to things like "this rule doesn't make sense" or "we need to separate things out for light airplanes vs. commercial ones" leans a lot more towards "Ok, let's work with you and see if we can come up with something that makes more sense for everyone". By contrast the FAA response is almost always to double-down and say "nope, the rule is the rule and we can't change the rule because then it wouldn't be the rule".

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#### Dan Thomas

##### Well-Known Member
Aviation is full of mythology. I encountered it when learning to fly nearly 50 years ago. Young pilots pick up all sorts of trash that they consider truth, since they haven't heard anything to the contrary, and because of the learning factor if Primacy, it's hard to convince them otherwise. I had to unlearn a lot of stuff when I became a commercial/IFR pilot, and as an instructor I had to deal with it al the time in new students. They knew better than their instructors, and because of that it took them longer to learn everything. We had to prove them wrong a dozen times before they'd start listening.

One of the myths is the "1930s aircraft engine technology." But the engines we have now only look like 1930s engines. They are not the same at all. There are vast differences in metallurgy and internal design in most of them. In fact, some of them were far ahead of auto engines when they came out. My ancient A-65 has hydraulic lifters, something that didn't show up in cars for decades after that engine was built.

Note that Jabiru is an air-cooled "dinosaur." Note, too, that the Rotax's heads are liquid-cooled, but not the cylinders. These are not very "advanced" designs. That Rotax has already been around for 33 years already, having been sold for homebuilts in 1989, and wasn't certified until 1995. That's 27 years ago, a lifetime in technology.

The SMA diesel is a clean-sheet diesel aircraft engine, built in France. Oil-cooled heads, air-cooled cylinders. I worked on one 12 years ago that was already having issues, and it only had a couple hundred hours on it. Certified, in a 182. By the time we were fixing a lot of stuff on it, SMA was on their third iteration of it, fixing shortcomings. There were 50 of those engines flying worldwide, and SMA told us they'd already spent one billion dollars on the project. That gives you some idea of the difficulty in coming up with a "modern" design. One can be skeptical of the costs and obstacles, but a lot of skeptical people have found out the hard way just how difficult it is. They're not skeptical anymore.

#### Skippydiesel

##### Well-Known Member
I agree with "hydraulic lifters, something that didn't show up in cars for decades " - aero engines (especially those developed during and shortly after WW2) were often leaders in engine technology and yes there has been "tweaking" around the edges "metallurgy and internal design" but this does not change the fact that the traditional air-cooled aircraft engine is now well behind its earth bound counterparts in fuel efficiency, vibration, pollution and noise. They are still an amazing bit of technology but real forward movement has just not happened and I believe this is due to the influence of the largest single market for these engines.
I have never understood the reasoning behind the development of the Jab range. I admire the tenacity of its developers but that's about it. To produce a dinosaur varient that is so far behind its nearest main competitor, Rotax, in all aspects of operation, except initial purchase price (a biggie!) is a bit like being the only soldier marching in step. I do understand that for pilots who may only be doing 50 hrs a year, around their local area, the purchase price is a big factor and the higher operating cost & suspect reliability, not so much.
On the SMA diesel - Oh how I wished for this concept to succeed - that it hasn't is a big disappointment. In reality the traditional LyCon style engine has been the beneficiary of 119 years of powered flight and I would suggest 160 years of automotive engine development. The challenge of developing a high power : low weight engine that can reliably/safely operate at near/full power for its entire service life, WITHIN OUR CURRENT FINANCIAL ATTENTION SPANE is awesome - I had high hopes for the Wankel/Mazda.
On Rotax - sure its been around for a bit more than a blink of an eye but what its done is marry aircraft & auto concepts into a very effective aircraft engine. Who else has achieved such success in this area? In my mind it leaves the traditional air cooled, direct drive in the dust. My introduction to the engine world was European cars/motor bikes - almost all small capacity high revving, so I am more than comfortable with the Rotax construction/service requirements - something that seems to trouble those raised on big bore slow revving engines. Their latest move up to 141 hp will be interesting to watch.

#### rv7charlie

##### Well-Known Member
Supporting Member
For probably its 1st decade, a lot of people here in the US were quite leery of the 9 series' high rpm and its gearbox (not 'traditional' enough to trust). It's a reasonable bet that Jab, with direct drive & air cooling, was shooting for that segment of the small engine market.

The big problem with getting modern tech into aviation is the (lack of) size of the market. We can pretend it's the FAA's fault, but it isn't; it's the pilots. Porsche played around for a minute with Mooney, and no one was interested. Toyota & Honda played around with prototypes, but you can rest assured that neither ever had any intention of going into production. They both sell more engines (in cars) before lunch than they could sell for airplanes in probably a decade. Getting either of their prototypes into FAA-approved production probably wouldn't cost any more than they spend in their private engine development programs (FAR more rigorous than FAA requirements), but...there's that 'before lunch' return on investment thing. Even if they did it, they'd face the same response from pilots (at least here in the US, which is probably half the market) that Porsche faced; 'Engines aren't done that way for airplanes'.

Mistral had what seemed to be an excellent design, and the company apparently was big enough to fund a really big development program. But I think their expectation of initial market acceptance was very unrealistic. My personal opinion is that they could have had hundreds of engines flying in homebuilts, and if they'd supplied a resonable level of assistance to homebuilders to keep cooling issues dealt with, they could have achieved what Rotax did with the 9 series; so many running successfully that the old school guys eventually began to cave to the idea of a modern design. Cooling assistance would have been essential; most guys have no clue on how to cool an a/c engine; the only reason Lycs work in homebuilts is because the builder can copy existing cooling systems, and even then, the forums are awash in 'why isn't my [insert engine here] oil, or CHT, etc cooling properly?' (reference the concurrent thread here on O200 temps....).

Having said all that, the resistance from pilots to new tech is understandable; it really comes down to 'the devil you know', because the devil you don't know can be the one that kills you.

To repeat the oft stated response to this oft raised issue, 'If it's so easy, why don't you do it?' ;-)

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#### rv7charlie

##### Well-Known Member
Supporting Member
Didn't say Jab was right; just suggested what their motivation probably was, back when they were making their design choices. Yesterday ain't today, after all.

#### KeithO

##### Well-Known Member
I agree with "hydraulic lifters, something that didn't show up in cars for decades " - aero engines (especially those developed during and shortly after WW2) were often leaders in engine technology and yes there has been "tweaking" around the edges "metallurgy and internal design" but this does not change the fact that the traditional air-cooled aircraft engine is now well behind its earth bound counterparts in fuel efficiency, vibration, pollution and noise. They are still an amazing bit of technology but real forward movement has just not happened and I believe this is due to the influence of the largest single market for these engines.
I have never understood the reasoning behind the development of the Jab range. I admire the tenacity of its developers but that's about it. To produce a dinosaur varient that is so far behind its nearest main competitor, Rotax, in all aspects of operation, except initial purchase price (a biggie!) is a bit like being the only soldier marching in step. I do understand that for pilots who may only be doing 50 hrs a year, around their local area, the purchase price is a big factor and the higher operating cost & suspect reliability, not so much.
On the SMA diesel - Oh how I wished for this concept to succeed - that it hasn't is a big disappointment. In reality the traditional LyCon style engine has been the beneficiary of 119 years of powered flight and I would suggest 160 years of automotive engine development. The challenge of developing a high power : low weight engine that can reliably/safely operate at near/full power for its entire service life, WITHIN OUR CURRENT FINANCIAL ATTENTION SPANE is awesome - I had high hopes for the Wankel/Mazda.
On Rotax - sure its been around for a bit more than a blink of an eye but what its done is marry aircraft & auto concepts into a very effective aircraft engine. Who else has achieved such success in this area? In my mind it leaves the traditional air cooled, direct drive in the dust. My introduction to the engine world was European cars/motor bikes - almost all small capacity high revving, so I am more than comfortable with the Rotax construction/service requirements - something that seems to trouble those raised on big bore slow revving engines. Their latest move up to 141 hp will be interesting to watch.

I dont think its hard to understand. Jabiru were first and foremost building and selling airplanes. Thus they needed an engine. Their location added significant shipping cost on what was already an expensive item (either Lycoming, Continental or Rotax). Then there is the particular poison of the "exclusive importer" who adds a markup of 50-100% of the original price to every item passing through their doors (just like with Japanese cars, heavy equipment etc). This results in an airplane produced by Jabiru being cost uncompetitive with one built in Europe or the US. Then the original Italian engine chosen for the Jabiru being discontinued, that put the factory in a pickle.

I own an airplane with a Jabiru 3300, a second generation engine. It has hydraulic lifters but not the roller type. It needs the head bolts re-torqued every 25 hours, matching the oil change interval... My engine has 700 hours and is fading fast because of lead deposits from 100LL jamming up the rings and producing blowby. In a country as large as the US, engine sales and maintenance has been consolidated to 1 shop in TN. If I fly the several hours to them for a top overhaul I was quoted $7500. If I buy the parts to do it myself I was quoted$4700. Their carb rebuild kit was quoted at $400+. While this work is cheaper than similar work on a Conti or Lycoming, if I had either of those it would not need a top overhaul at 700 hours. I think its an unfortunate fact that Jabiru's customers have indeed been doing a lot of the validation testing for the factory and then fixing it at their own expense. The 6 cylinder Jab is now$19500 whereas the 100hp 912iS is $24k. If I was contemplating a choice between these 2 engines I would definitely pay the extra$4500 for the Rotax because of its known superior reliability and durability and for having eliminated the 50's carburetor on the Jabiru (lawnmower magnetoes anyone ?)......

#### KeithO

##### Well-Known Member
Sure. Now add in the cost of converting and mounting it and working the bugs out of it. Have you done that? I have.

Everything looks easy and cheap until you try it.

#### KeithO

##### Well-Known Member
Here in the US, on any cross country flight, there will be no place at 99% of airports to get unleaded fuel. Its a logistical hassle to find a gas station that sells ethanol free gasoline (automotive gasoline has Min 10% ethanol content by federal law and it does not play well with aviation applications, especially at higher lattitudes when cold, freezing, condensation and at the same time, high summer temperatures come into play.) The stuff I have started buying is called "Recreational fuel", cost (today) $5.30/gal vs$3.65 for regular pump gasoline (with ethanol). But 100 low lead aviation gasoline is $7/gal self service or$8.75 if you call the truck to the hangar to fill up.

My understanding is that if the Rec fuel works out (it only has 90 octane, so I have to add an octane booster to get it to 94 at least, more expense) I could see 100hr oil change intervals vs 25 hour intervals due to the elimination of lead sludge in the engine. And none of the problems with the rings getting stuck, valves potentially getting stuck due to deposits. And longer spark plug life also. If you have a modern engine with an O2 sensor, one has no operational restrictions on unleaded fuel whereas with 100LL the sensor will probably only live for 30 hours before it is contaminated to the extent that it is useless. And leaning with the help of an O2 sensor is the simplest thing imaginable.

So far, the UL fuel will cover all of my wifes training flights (100+ hours planned in the next few months) and I will have a fuel caddy holding the uL fuel in the hangar, so easy to refuel. If she does a cross country there will be Decalin additive in the plane to add to the tanks, it should help reduce the effect of the lead contamination, but not eliminate it. Better than doing nothing. In the meantime, for this coming winter I may elect to disassemble the engine and attempt to clean off the deposits from the pistons and cylinders. If there is too much wear then I will just have to order the parts needed to do the the top overhaul if cleaning is not going to be enough.

#### Skippydiesel

##### Well-Known Member
KeithO - fortunately, for me, we fly in very different environments.
In Australia we have access to 91, 95 & 98 RON ULP.
10% Ethanol fuels are also available (have never used them). I am aware that E10% is okay for a Rotax 9, subject to aircraft fuel storage & reticulation compatibility.
95 RON is getting harder to find, with many fuel stations consolidating their offering to just 91 & 98 RON (my local). I use mainly 98 but have found little/if any, difference in performance, when using the cheaper (small margin) 95.
Like you very few airfields carry ULP - At home I have 20L x 5 plastic fuel containers. On an away trip I carry 20L x 2 collapsible fuel bladders. Most airfields seem to have a kind sole willing to lend me a vehicle or transport me to/from the nearest (suitable) fuel station. The nearest fuel station & contacts on ground, is part of my flight planning.
I use a home made, positive displacement (Holly copy) transportable, 12volt fuel pump for fuelling - no wastage, back/arm strain and its almost as fast as pouring into a wide mouth funnel (which I don't need). All fuel filtered in.

#### Vigilant1

##### Well-Known Member
Supporting Member
Here in the US, on any cross country flight, there will be no place at 99% of airports to get unleaded fuel. Its a logistical hassle to find a gas station that sells ethanol free gasoline (automotive gasoline has Min 10% ethanol content by federal law ...

Of note: If the government mandate went away, fuel companies would still blend in about 10% ethanol. It is the cheapest way for them to produce fuels at the octane ratings that cars need/the market demands. Sure, some outlets would offer ethanol free gasoline (as they do now in many markets), and some motorists are willing to pay a higher price for it. But, it remains a boutique product for a niche market.

#### rv7charlie

##### Well-Known Member
Supporting Member
E-gas is not a mandate in the US. According to pure-gas.org, there are 467 stations selling E-free mogas in my home state, alone. I know of 4 or 5, within 30 miles of me.

And E-gas works just fine in a/c, *if* proper precautions are taken. Most rotary drivers run it all the time, and a growing number of Lyc drivers are doing it, too.