OK. Lets scale up the Rotax to 133 HP continuous, what do we get:
Too bad that has not worked out so far and the 912iS is only heavier and more expensive but not delivering a single HP more. The improved efficiency of the 912iS is only achieved where Rotaxes are rarely found: at high altitude where the mechanical carburetor mixture adjustment performs poorly.
I’m with you when it comes to gasoline engines being simpler and cheaper. However, the fuel is becoming a problem and unless there is going to be direct replacement for 100LL, this forking of gasoline into multiple fuels is only going to accelerate the demise of gasoline as an ubiquitous aviation fuel.
My data comes from Technify, which may or may not have massaged it (though I can’t see why they’d massage it for 2013).
Re – old technology; in my opinion simplicity and intuitiveness drives product acceptance. It’s perfectly fine that some people are happy with old skool lawnmower tech, but that cannot go hand-in-hand with volume and product acceptance. The debate has been raging for… what… 50 years? on LOP vs ROP operations, there’s no definitive opinion on that, yet we’re told this technology is “simple to operate”. Maybe that was considered simple way back when people were still used to pulling a choke and handcranking their car… but that in no way will drive product acceptance nowadays. You don’t see Ferraris built with 1950es technology just because “it works”. They are not cheap cars, not by a long shot (most cost actually MORE than a Cirrus), yet every single one of them is sold BEFORE it leaves the production line. Same for all top-end supercars (no, the Corvette doesn’t qualify). What does that tell you?
PS – funny you mention accelerator failures; one of the well known Rotax 912 failure modes is one of the throttle two cables snapping and the corresponding carb defaulting to a WOT setting. At least it doesn’t blow a cylinder off like “good ole tech” does :)
Your posts are full of “I know better” and lots of misinformation. One last example: a Rotax 914 consumes 20 litres/h at 75% power (not: “12-15”).
What about if you typed a bit less, but more accurate stuff?
Too bad that has not worked out so far and the 912iS is only heavier and more expensive but not delivering a single HP more. The improved efficiency of the 912iS is only achieved where Rotaxes are rarely found: at high altitude where the mechanical carburetor mixture adjustment performs poorly.
Rotax has already fixed this last summer. The 912iS Sport is the new engine, the 912iS is not sold anyomore. All owners of 912iS can free of charge upgrade their engine to “Sport” version.
I’m with you when it comes to gasoline engines being simpler and cheaper. However, the fuel is becoming a problem and unless there is going to be direct replacement for 100LL, this forking of gasoline into multiple fuels is only going to accelerate the demise of gasoline as an ubiquitous aviation fuel.
Avgas UL91 is the future. But I have to admit that running on jet fuel/diesel would be a better option. Nevertheless what is important is the package fuel+engine, and the gasoline engine wins that competition.
Your posts are full of “I know better” and lots of misinformation. One last example: a Rotax 914 consumes 20 litres/h at 75% power (not: “12-15”).
What about if you typed a bit less, but more accurate stuff?
You are half right, it is about 15-16 liters. Any other errors? At least no one accuses me of being a grumpy one liner dude 
It is about exactly 20l per Rotax (75% at 5000 rpm) so probably about a bit more in real life :)
You don’t see Ferraris built with 1950es technology just because “it works”. They are not cheap cars, not by a long shot (most cost actually MORE than a Cirrus), yet every single one of them is sold BEFORE it leaves the production line. Same for all top-end supercars (no, the Corvette doesn’t qualify). What does that tell you?
This is hopeless argumentation, what exactly is your point?. I bet there are just as many Ferraris from the 1950s-60s-70s around as there are Ferraris from the 2000-2014. What does that tell you?
My point is – try to sell a car from the 60es today other than a collector, see how well it works. My point is – there are people with money in the market more than ready to pay for new tech and drive prices down. My point is – make it intuitive to operate and more people will buy it (there is this fruit name phone brand… can’t recall the name…). My point is – old tech works. New tech sells.
The Rotax v. Lyco is an irrelevant comparison, because of airframe+engine certifications.
Rotax play mostly in markets where you can screw any engine on the front of anything with two wings, more or less.
In those markets, the Lyco O-200 is an option, but also in those markets most people are incapable or unwilling to operate any kind of engine management (setting the red lever for peak EGT in cruise) so the Rotax delivers much better SFC (a 30% saving is possible with the red lever). If people were even half smart, the O-200 would be better than the Rotax becaise it revs slower. But also, in those markets, one is facing artifically created weight categories and the lighter Rotax wins again. Not because weight makes much difference to performance but because of the regulatory-environment-generated weight categories.
The Ferrari comparison is irrelevant too. Loads of people buy these “supercars” and loads of millions are spent on R&D – because the money is recovered via sales. You can buy a used Aston Martin DB9 for £39k. Every “banker” and every “Harley Street” surgeon has one of these cars. My son (21; a web designer) wants a DB9 and he can probably get it. Never before in the history of the human race has it been as cheap to be a poser as it is today. But if you ran a Ferrari engine at 65% of max rated HP it would fall apart as quickly as most car engines.
Sure one can complain about the old 1950s engine designs but they are the best for the job that currently exists. They are damn efficient for all the reasons known since thermodynamics were discovered: slow revs, big cylinders, air cooled. They just need careful thermal management, which is no problem for anybody with more than half a brain (and about €2k in engine instrumentation) but a lot of people use this as an excuse for pushing “modern” technology, which doesn’t work at all unless you chuck a lot of complexity at it (sensors, FADEC, etc) and then you just end up with a complex engine which only a specialist can work on, so the industry has got you (the owner) over a barrel. And avoidance of barrels is one of the main goals in GA aircraft ownership.
You are half right, it is about 15-16 liters
Laughable. My conversation with you is over.
I guess others would do the same if it weren’t for the generally interesting subject of the thread.
I couldn’t agree more about ‘avoiding barrels’!
Comparing a super car engine with an aircraft reciprocating engine is to compare a piece of jewelry with an industrial machine that has to earn its keep for decades in order to be economically viable. I think you might as well compare a woman’s set of diamond earrings with a Snap On socket set.
The Rotax is interesting to me because it’s actually the only mass production engineering style engine that’s succeeded in the GA market. The issue remains that it’s not a long term investment to buy one, especially not for a certified application. At the end of 2000 hrs or so you have very little to reuse – the two stroke style built up needle bearing crankshaft/rod assembly needs to be tossed, the cylinders are Nikasil so if they are worn its likely easiest to buy new and so it goes. You can overhaul the heads and reuse the crankcase. Now scale the engine to 150 HP and six cylinders… Do you think the idea has not occurred to Rotax? I think what happens is that at GA volume you can’t compete on economic terms with an O-320 or O-360. So Lycoming stays busy building engines and parts for RVs etc.
GA aircraft engines are an industrial product by nature, not a consumer good. When you you look at similar products in O&G, Marine and Heavy Industry you find lots of them that last a long time and get overhauled… because that’s the best way to solve the problem at the actual scale of the problem. The real world is not all software and cell phones.
