Why Rotax Built an Eco-Engine

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Sometimes I feel like a bug smashed on the windshield of aviation progress. At least that's the impression I got on Thursday at Rotax's giant factory here in Gunskirchen, Austria, when I walked into a big product display tent set up on factory grounds. This was one of those giant Taj Mahal-type tents reminiscent of Eclipse's glory days and it was wingtip to wingtip with 10 LSAs already equipped with Rotax's new flagship aviation engine, the 912iS.

Major new product rollouts like the 912iS don't happen often and they happen even less in the engine segment. The typical product rollout is one third trial balloon, one third fanciful work by the modeling department and one third crafty press release prose. Not Rotax. In addition to the 10 airplanes already fitted with the 912iS, a trial production line was moving along with the first 50 engines and the company says it's about six weeks away from shipping the things. Many of the BRP workers were already sporting well-worn 912iS logo wear. Clearly, Rotax has been at this for a long time—at least a couple of years and a thousand hours of testing, including flight time.

What's this going to mean to the market? A good question. The 912iS, which BRP/Rotax is marketing as an eco-engine, will carry something like a 20 percent premium over the legacy 912 series, which will remain available. For the addition bucks (or Euros), you get a more efficient engine with sophisticated self-diagnostics than even an owner can use. (Rotax has developed software that will run on PCs to download fault codes and operating data in plain language.) In short, your airplane engine is getting closer to your car engine and it's about time, thanks very much.

I don't have good specific fuel consumption numbers yet, but for planning purposes, Rotax says the 912iS is 20 percent more efficient. That's the difference between 4.2 GPH and 3.4 GPH in cruise or a BSFC from the mid .4s where the carbureted 912 runs to the high .30's, which would be a considerable achievement if it turns out to be accurate. But what BRP has its eyes on—and you won't like reading this if you are a U.S. pilot—is carbon emissions. A typical 912 spits out 85 pounds of CO2 per hour compared to 68 pounds for the 912iS.

Here in Europe, they take the carbon thing more seriously than we do in the U.S. because we have politicized CO2 emissions to the point that any suggestion of a need to reduce carbon pollution is taken as hogwash—the lunatic ravings of the green crazies. BRP, which makes its living building engines to stoke the hydrocarbon lifestyle, doesn't have the pleasure of denial. They see which way the world is going on CO2 regulation and rather than fight it, they aim to be ready with more efficient, lower emissions engines and that's what the 912iS is. BRP is applying similar technology in its other markets because it wants to give its customers more efficient options to reduce fuel costs and it believes it has to pay more than lip service to lower carbon emissions. Whether it's right or wrong—I think it's right—it's well positioned to move forward into an age when light aircraft fuel efficiency is going to matter. We are, in fact, already there. Like the 912, by the way, the 912iS will also burn mogas up to E10.

We'll have more reporting on European swing later this week.

Comments (26)

A perfectly combustion-efficient IC engine produces only water vapor and CO2 as an exhaust (that also of course assumes a pure hydrocarbon fuel and a pure O2 air charge but the reality of combustion is close enough for blog comment purposes). Trying to reduce CO2 emmissions can therefore only really be accomplished by improving SFC, all else being equal (e.g. engine BHP and displacement, fuel used, etc).

While reducing fuel consumption is a great goal - afterall fuel is one the biggest costs of flying - CO2 emmission controls are silly. If you want to improve the real "greeness" of an engine, rather than it's political greeness, focus on the emmissions of unburned hydrocarbons, NOx, lead, and so on.

When the boondoggle of CO2 driven AGW finally dies the death it deserves we'll all be better off.

Posted by: Andrew Upson | March 9, 2012 2:18 PM    Report this comment

I think the reason they (Europeans) take CO2 emissions more seriously is that they have run out of things to tax and are looking for any excuse.

Nevertheless, the 912iS seems like a good deal except for the price, if it is truly 20% above their already pretty high price. Electronic ignition and fuel injection certainly have improved automobile operations, particularly things like hot and cold starts, which most airplane engines are miserable at.

As far as fuel economy, I'm not so sure. I have a fuel injected Harley and my brother has an identical but one year older model with a carb. Much to my chagrin, he gets slightly better gas mileage when we ride together. Maybe the Rotax-Bing carb combo wasn't so good and thus the F.I. was a dramatic improvement (or maybe Harley has bad F.I.).

Posted by: Stephen Phoenix | March 9, 2012 2:40 PM    Report this comment

The fine print appears to say direct injection, not just fuel injection, which is a big deal. Hope they keep their promises

Posted by: RAY DAMIJONAITIS | March 9, 2012 7:58 PM    Report this comment

Would make a heck of an engine in a C150/152. Flying for 3.8 gph instead of 6 would pay off pretty quick in a flight school.

Posted by: Josh Johnson | March 9, 2012 8:23 PM    Report this comment

What's the big improvement? A turbonormalized Continental 520 or 550 (8.5:1 compression) running Gami injectors and lean of peak cruises with a BSFC of .39 to .41 according to TAT data.

Posted by: Charles Haubrich | March 9, 2012 8:30 PM    Report this comment

Thank you Charles, The big bore engines have been doing this for some time. Its the little guys who have yet to catch up. While the world wants to see lower emissions in carbon output, the aviation market wants to see lower emeissions in fuels savings. Two ideas after the same goal.

Posted by: Kevin Strange | March 9, 2012 11:57 PM    Report this comment

It is direct injection, with two fuel injectors per cylinder. Not port injection.

In an engine of this class, when you're paying $8 a gallon for autogas to run it,may be quite attractive to the recreational and training market. If gas goes higher--which it very well could--it may find a ready market. 20 percent efficiency is a considerable improvement.

I've talked to a few LSA people and they seem split on whether this engine--given its price premium--will become the engine of choice for LSAs or light Part 23 trainers, if such a thing ever comes to pass.

It has to earn its chops on durability and reliability first.

Posted by: Paul Bertorelli | March 10, 2012 12:00 AM    Report this comment


When comparing/contrasting fuel burns (SFC, really), you have to look at it two ways – what the engines are capable of, and what the engines yield in actual use. In the flight training environment, WAY too much time is spent tooling around at full-rich mixture settings. This poor practice is abetted by clock-hour wet rates, which cause both students and flight instructors to conclude that “it doesn’t matter – I’m not paying for the gas!” (High-altitude operations obviously don’t employ such techniques.)

The decision to re-engine a rental aircraft depends on many factors. Ignoring all except SFC, it boils down to “how many flight hours will an engine have to provide, just to pay for its incremental cost?”

Assume the following: $8/gal fuel; a typical burn of 6.7 gph (typical 2-seat Part 23 trainer) for a traditional engine; 4.5 gph for the candidate engine; a zero-cost STC for the conversion; selling the core of the run-out, so net cost of the new engine = $20,000. Fuel savings will be 2.3 gph x $8 = $18.40/hr. All other things being equal (they rarely are), you’ll start to see a payback after flight hour number 1,087. If the real-world TBO > 2,000 hours, you’ll build an overhaul account of $16,800 by the time that you reach TBO. The next time through, you’ll have accumulated $36,800, minus any overhaul cost above the banked $16.8k.

Posted by: Tom Yarsley | March 10, 2012 8:30 AM    Report this comment


With a decent FADEC, things would improve a lot. You’d get burns that approach that factory-boasted SFC, so the overall savings could be larger than calculated above. In theory, operating a one-lever engine at best-power / beat-economy all of the time would extend engine life and reduce maintenance costs. It also would boost dispatch reliability and reduce fueling costs, because the interval between re-fuelings would increase.

As a flight school operator, I’d also consider the safety advantage of not having a carburetor to ice up, nor the ever-present opportunity for students to attempt go-arounds while carrying full carb heat. If this new engine is 80% of what its manufacturer claims it is, it’s a winner in my opinion.

Posted by: Tom Yarsley | March 10, 2012 8:30 AM    Report this comment

The ability to run automotive gasoline also would save a small fortune with this engine. I assume an STC to run mogas with ethanol would require fuel tank mounted pumps in a legacy airframe, but that should be simple enough.

Posted by: Josh Johnson | March 10, 2012 7:14 PM    Report this comment

The current 912 models also run on E10, depending on whether the airframe manufacturer approves it. I doubt if conversions of legacy airframes would make much economic sense. The fuel delta between mogas-burning conventional engines such as the O-200 or O-235 and the Rotax is not great as a percentage of airframe value to make much sense.

The larger driver is the efficiency of the airframe and 150s and 152s aren't efficient enough to really take advantage of the lower fuel specifics, although it might work in the training role.

Posted by: Paul Bertorelli | March 11, 2012 3:08 AM    Report this comment

Rotax is also catching up on all the engine shops, who for €2,000 plus the old carb fit crude injection kits, which usually improve fuel economy by 10% in real terms. They have been on offer for years.
They are popular in France where the ULM (microlight) regulations mean you can do your own maintenance, and pay the consequences -- the death rate is higher than that for motorbike crashes.

Posted by: Brian McCulloch | March 12, 2012 9:21 AM    Report this comment

Everyone is zeroing in on the technicals of this new engine while forgetting that the reason LSA's aren't selling in large numbers is their cost v. benefit. The only thing that's going to attract buyers to LSA's in sufficient numbers is a great design and proper pricing. This engine COULD be a part of that equation.

In order for an existing LSA to attract me it must be fast , have long range and/or a decent useful load with a reasonabe price. LSA’s HAVE to cost what they do because they aren’t produced in sufficient numbers. If we could somehow solve THAT conundrum, the movement could potentially be the savior of GA.

Light sport draws the older pilots in because of the no medical issue. It subtly offers all owners the ability to do their own maintenance and manufacturers to install cheaoer non-TSO’ed equipment and to certify the package easily. As Paul says, a (new) “light” two-place Part 23 or ASTM airplane with good aero efficiency with one of these engines installed and with good load carrying ability would turn my head if one could be brought in around $125K.

In the early days, everyone scoffed at the Rotax. They’ve now proven themselves to be reliable little engines but -- unfortunately -- their prices are going up. Saving fuel, greater reliability, and fuel injection can make up for same. Now lets see someone marry it to the right airframe and sell enough of them to achieve economies of scale. It they do, buyers will ‘come.’

Posted by: Larry Stencel | March 12, 2012 11:50 AM    Report this comment

BRP is recognising reality; Aircraft Engines need to be modern. Lycoming and Continental seem to be backing away from updating their products. There is no technical reason that the legacy manufacturers aren't building state of the art engine control systems. Both have toyed with electronic engine controls, but have not pushed forward. If Lycoming and Continental don't have the engineering talent to create up to date systems, they could contract it from someone like Ford. They should be providing new engines that run on Mogas, Premium or Regular as required. The components of such an engine control system are easily available, and likely total less than $250 at the OEM level. Given development and certification costs, the 20% increment that Rotax is charging is a bit high; a lower increment is achievable.
Further, it should be a simple matter to engineer a complete certified retrofit system for existing engines, at a cost of $5000 or less.
There is no technical excuse why we are not flying fully electronic, cleaner, more economical engines on widely available fuel. Who will step up?

Posted by: BRIAN HOPE | March 12, 2012 12:34 PM    Report this comment

While the cost of re-engining legacy aircraft doesn't make economic sense to the owner, that's not including resale of the aircraft. If gas is $10/gallon, a 912iS is going to command a hefty price premium at resale. Even allowing for the TVM costs, consider that an inefficiently-engined airplane may not sell at all, except maybe as a lawn ornament. Of course, the STC's for engine swaps have to come first, and they might not. I don't see it happening for my 182 :-(

Posted by: DAVID CHULJIAN | March 12, 2012 12:41 PM    Report this comment

Rotax contracted with Rockwell Collins -- who has the requisite talent inside the US -- to build the 912iS ECU. The new Lycoming O-233 uses an electronic mag with variable timing and fuel injection which goes part way but not as far as the Rotax. As Paul says, if the 912iS does provides the 20% or so increase in fuel efficiency along with reliability and the capability for an operator to self-diagnose the thing, it'll be a winner. It IS time for Continental and Lycoming to come up with a similar design. Their O-200 and O-233 'lite' engines are little more than warmed up leftovers.

Posted by: Larry Stencel | March 13, 2012 12:05 PM    Report this comment

"...The only thing that's going to attract buyers to LSA's in sufficient numbers is a great design and proper pricing. This engine COULD be a part of that equation..."

I'm guessing you missed the part where Paul B. said this engine will cost 20% more than the older version?

I don't see a fit for US product, except if they can convince Cessna to put it in the Skycatcher. No one will bother with the costly development of STCs for legacy planes that use 100 Hp.

I was once involved in the development for an STC to put an O-200 into a J-3 Cub. It was costly and the only reason it was done was because the Boss was a multi-millionaire (back-in-the-day) and wanted it. We advertised it to others to recoup some of the cost, but never sold one.

Posted by: Edd Weninger | March 13, 2012 2:03 PM    Report this comment

There will likely be another LSA or two to emerge from the U.S. as a joint venture with a European company. Stay tuned on that. It may or may not use the 912iS.

What's unknown is how the market will respond to the iS's higher cost. Will it see the fuel consumption as a worthy offset? And second, the fuel consumption numbers have to be borne out. Marketing brochure claims do not necessarily make for sales.

Still, it's welcome progress and I am glad to see it.

Posted by: Paul Bertorelli | March 14, 2012 6:10 AM    Report this comment

I think one of the biggest reasons Rotax decided to go with EFI is because they are about to get their clock cleaned by the engines made by UL Power up in Belgium. How come Avweb never did any kind of an article on those engines ? They've only been around for about four years now and are cheaper and better than the Rotax offerings.

Posted by: RANDOLPH PALMA | March 14, 2012 7:18 PM    Report this comment

Oh, I don't know...it may have something to do with the fact that the company hasn't returned queries for information or doesn't seem interested in hosting visits.

This is very common in this industry. More on this later.

Posted by: Paul Bertorelli | March 15, 2012 5:24 AM    Report this comment

"Why Rotax Built an Eco-Engine " - because "Eco"-anything is a popular marketing term that sells stuff these days.

Posted by: PETER THOMAS | March 15, 2012 7:38 AM    Report this comment

I just bought a new GM pickup with their 5.3L Active Fuel Management (AFM) direct injection one coil per cylinder V8. This thing gets phenominal gas mileage (I've seen as high as 25 if I'm careful) and has oddles of power compared with my 20 year old 5.7L throttle body injection truck which barely got 17 mpg. So almost a 50% improvement in fuel economy.

Likewise, the new Rotax 912iS will likely improve the reliability and fuel consumption of the 912ULS with twin carb and no ECU. If you only saved 1GPH, over a 2000hr TBO, you'd save $10K in fuel costs at $5/gal. Most will see better. So the added cost is essentially free over the course of one TBO, more if fuel keeps going up. And, you get the added advantage of FADEC and reliability.

If I had to fly a 912ULS or the 912iS from CA to Hawaii, I know which one I'd pick ... hint ... it doesn't have carburetors. And, being able to plug my laptop into the ECU so the engine can "tell" me how it' doing is appealing to me. Knowing that Rockwell Collins built the ECU is a plus, too.

Rotax has become the de facto standard for LSA airplanes for a reason. Making their little engine better still is good for all of us. I just wish they said that they did it for efficiency reasons and NOT to be "green." I'm tired of that over used hyperbole.

Posted by: Larry Stencel | March 17, 2012 4:40 AM    Report this comment

I just wish they said that they did it for efficiency reasons and NOT to be "green."

They are doing both, Larry. Let's not forget that BRP's survival depends entirely on the burning of hydrocarbons for recreational purposes. They aren't Ford or Toyota.

They are feeling definite pressure on environmental concerns. They want to have answers. One of the executives we spoke to said..."we like what we're doing. We want to keep doing it."

We should not decry the idea of an engine that has fewer emissions just because we don't like "green." It is in no way a bad thing. Better fuel efficiency comes along with the bargain.

Posted by: Paul Bertorelli | March 19, 2012 3:11 PM    Report this comment

EFI & ECU can be used to EITHER boost performance, OR to boost fuel efficiency, or some combination of the two.
In this case, Rotax clearly targeted fuel efficiency which also achieves a cleaner burn, burning more of the fuel and leaving less partially burnt products of combustion (i.e. undesirable compounds) in the exhaust gases.

Personally I would like to see a dual-map ECU where the operator (pilot) can toggle between PERFORMANCE or ECONOMY at will. For example, use Performance mode for taking off in High, Hot & Humid conditions and/or short runway, then switching to Economy mode when cruising.
One spin-off from Rotax committing to EFI is that other engine manufacturers will wake up to the benefits of EFI. I am a paramotor pilot (powered paragliding) and have been trying to convince paramotor engine manufacturers for many years to investigate EFI. We are just about to see the launch of the very first such project (the Top80 engine), while others have been playing it down. With Rotax's entry into this field, perhaps more manufacturers will take EFI seriously.

Posted by: Keith Pickersgill | March 20, 2012 9:16 AM    Report this comment

"....the operator (pilot) can toggle between PERFORMANCE or ECONOMY at will...."

I use a mixture control to accomplish this ;-)

Posted by: Edd Weninger | March 20, 2012 12:36 PM    Report this comment

"One spin-off from Rotax committing to EFI is that other engine manufacturers will wake up to the benefits of EFI."

I see you haven't been paying attention...Continental has had its EFI FADEC available for more than 10 years and Lycoming is about to certify a similar system.

It's the market that needs waking up, not the engine makers.
The Continental system does, by the way, have the economy versus power switch as an option.

Posted by: Paul Bertorelli | March 20, 2012 6:51 PM    Report this comment

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