An interesting new engine development program

This is very interesting, and follows on from an earlier EuroGA thread tangent in which cylinder blow-by was mentioned. These cylinders are all aluminum meaning they may have Nikasil coated bores, like an air cooled motorcycle cylinder. That allows much smaller cylinder-to-bore clearances and thereby much reduced blow-by and oil consumption. When this was done on large displacement air cooled motorcycle engines in the 80s, oil consumption dropped to about zero.

I’d assumed that various factors like the Lycoming design placing the cylinders in tension (no cylinder through bolts) and maybe the need for fine pitch cooling fins might preclude all-aluminum Lycoming cylinders. Note how much larger the cylinders are to get enough fin area with thicker aluminum fins… but it seemingly fits and works.

Neat stuff

PS having looked at the PDF spec sheet Link, I see they’re Hypereutectic Si-Al sleeved and don’t incorporate directly applied Nikasil, but depending on the sleeve and piston materials it can still work out similarly in terms of tight cylinder clearances.

This will probably never be certified. Oil consumption isn’t a major issue and doesn’t justify a large R&D effort to improve it. More horsepower won’t work either because the crankcase, crankshaft, bearings etc. are not designed for more. Lycoming/Continental haven’t even managed to certify electronic ignition although that is fairly trivial and adds considerable value.

My car has a 1.6 liter diesel engine that even with 20.000 km service intervals has never needed a top up of engine oil.

Apart from being chimp technology, aero engines are air cooled whereas your diesel is liquid cooled. Air cooled engines operate in a much wider temperature range and see a much larger distribution of temperatures throughout the engine which requires much larger tolerances between parts. It doesn’t have to be as bad as with Lycoming and Continental which represent 1950s technology but it will always be a different animal than your liquid cooled car engine.

Aero diesels are more similar to car engines and have virtually no blow by. However, they also have the very open crankcases of gasoline aero engines which car engines do not have.

Usually the way this kind of development works is that after the ‘first adopters’, air racers etc, work out most of the major bugs, the RV guys and their brethren adopt en mass. After about 10 years of that, certified customers get interested and an STC results. I have a friend who has done a number of component developments that way and now sells his stuff to airframe OEMs, certified aircraft owners by STC and amateur builders. I think Diamond was his first OEM customer, in about 1993. Its basically the intent of the FAA Experimental Category, and he makes a very good living out of it.

I see a strong analogy between Lycomings and US built V8 car engines. They’ve both ended up being timeless because the initial concept was right, they led the pack initially and everything else works out as more expensive. Detail development over time can and probably will improve them for many more decades, and a lot of it will be done by the aftermarket – the Experimental, STC and PMA systems mean that aircraft and engine development is not a centrally controlled activity.

Piston to cylinder clearances for aluminum air-cooled cylinders are about the same as a water cooled engine, i.e. very tight. Aluminum bored cylinders were a big advance in the 70s and 80s when introduced on motorcycles and in addition to the cylinder sealing improvement, bore wear with Nikasil dropped to approximately zero. The initial work by GM, BMW and others on water cooled car engines without iron sleeves had some significant problems, but when applied to air cooled cylinders there were no problems with Nikasil that I recall. It’ll be interesting to see how this hypereutectic Si-Al sleeve thing works out in comparison; its not blindingly clear to me why they went in that direction.

For every new Panthera there will probably be fifty Vans RV’s completed.

My guess would by 11,000 RVs flying to perhaps 50 Pantheras, five years from now.

The reason that Lycomings remain preeminent in GA, supported by Continentals that are perhaps a little less robust and 1980s Rotaxes for low power applications, is because buyers think they are the best tools for the job, in 2014. Knocking established players is a favorite activity of armchair engineers, but reality tends to continue unimpeded. The push rod Chevy V8 car engine introduced in 1955 works well in 2014 too, makes 460 HP while weighing very little, and works well in an appropriate application. Its one reason a new Corvette goes fast and costs Euro 37K. Link

I think there are many good reasons why Lycomings will be developed by the aviation community in a similar fashion, for similar reasons. The people who will actually pay for the development, buying the parts with their own money, are flying $60K experimental category aircraft and aren’t interested in buying heavy, complex, vastly expensive new engines.

AEIO-540s making full power for aerobatics are expensive to run even without paying outrageous fuel tax.

Lower compression Lycoming variants like my O-320 run fine on auto fuel – my certified plane was STC’d for auto fuel years ago and run on it for a long time. In Europe you have the advantage of still being able to buy it without alcohol. Its certainly possible build similar non-certified engines from parts. A guy I know built an injected O-320 for under $15K using some new parts, some yellow tagged parts and some red tagged parts that had trivial non-conformances. He’s been flying it from about 7 years now, and the plane made the cover of one of the US national magazines. It shows every sign of going to TBO without issue.

Another friend has a S1S and keeps encouraging me to buy a $20K Experimental S1C so we can tear around in them together. However landing at ~100 kts without forward view intimidates me a bit! We go out in his Citabria every once in a while so I can practice flying from the back seat. I flew front seat in a S2C a while ago, did some rolls etc and it stands out as one of coolest things I’ve done. Its more fun to turn the horizon when your view is framed by the wings.