So, let's say you're interested in building an airplane for flying to breakfast and maybe the occasional <400 mile fishing trip. You'd like a Super Cub but they're stupid expensive.

The available homebuilts, including various RANS, various Zeniths, and various Cub clones, are generally powered by Rotax 912's or Lycoming clones, the recent favorite being the Titan O-340.

If you have Rotax experience, what do you think of the options?

Compared to the Titan, the Rotax will:
1) Cost 30% less up front.
2) Weigh less.
3) Produce less horsepower (100hp vs 180hp)
4) Make a slower airplane (typically 110mph vs 150mph)
5) Burn less fuel and cheaper fuel -- 5gph of E10 pump gas.
6) Sound a lot less like an airplane.

But what about installation and maintenance? Have you built one? Maintained one?

As for "maybe more...." what about fabric vs aluminum?

Just making conversation. Don't try to guess my intentions!

I installed and maintained a Rotax 912 80hp engine in a Zenith 701. Initially I was very paranoid about an engine that was not a Lycoming or a Continental, however I warmed up to the Rotax 912. They are light weight, efficient and reliable. On the minus side, they have some quirks and sound like a weed whacker. Balancing the carbs is one of the quirks, but it really is no big deal. The new 912is does away with that problem but they are more expensive. I am currently building a Sonex Onex and I am going to install a Rotax 912 100hp in it. The traditional engine for the Onex is an 80hp VW conversion. The Rotax will give me 20+ more horsepower than the VW, will be much more reliable and will be much lighter.
What airplane are you thinking about building?

I'm just making conversationnnnnnnuh.....!

In a weak moment, I might admit that my currently-RV-8-building eye has been captured by RANS S-20 vs S-21. Call it reverse mission creep. I started the RV thinking it would be a Bonanza killer, but I've come to realize that there is no single-engine Bonanza killer!

The Rotax, burning less than 5gph of $2 pump fuel is hard to ignore. How much would I fly if the marginal cost was $10/hr? Maybe a lot more, but maybe not.

those are engines for different classes of planes. I think of the rotax as a peer of an cont O-200 or lyc O-235. The O-340 is more of an O-360 class of engine

in airplane terms it's super cub vs aeronca champ

the rotax is efficient and reliable, the only complaint i have with them is that they are stupid expensive to buy compared to many of the 80-100hp alternatives

I have a Rotax 914, it's the best aircraft engine I've ever flown behind. It's like a sewing machine: smooth, easy to start, quiet and burns very little gas. Light years ahead of the Continental or Lycoming.

I think the military has used Rotax in drones. Are there any available failure stats for them?

The little hearsay I've had from experimental folks is all extremely positive. Can verify the 100hp models sip 4-5 gph.
Wish they would made a 180 hp or higher version to put in the RV6.

IIRC, Predators have Rotax 914's, which are turbocharged. Since a Predator costs over $2 million, it seems they wouldn't skimp on the engine. Also IIRC, the size of the Predator contract makes Rotax the largest piston aircraft engine producer in the world.

I wonder about installations. It appears there's basically one Rotax 912 ULS. Every individual has the accessories located in the same place, meaning every kit designer knows what dimensions he has to deal with. OTOH, a Lycoming IO-360-LBJ may be entirely different from an IO-360-FDR, which means a builder might find distressing answers to questions he didn't know to ask, and no builder gets a cowling that fits right out of the box.

Am I too optimistic on this Rotax install?

Military runs the 914 to 7000 hours before overhaul; I think that says something.

I have about 35 recent hours on a 914 and I thought it would be weird and I was a little nervous. Wasn't weird and I'm no longer worried about it. The 914 does need higher octane auto fuel and I prefer non ethanol. I can get that (did today) for $2.90 gallon. What I don't like about the Rotax is that if using aviation fuel regularly it lowers the gearbox tbo and a few other possible issues. With the aggravation of fueling, toting auto fuel....I had rather just pay the extra dollar and stay 100% aviation fuel. I get 5gph one takeoff and cruise fuel burn.

With a Searey, I usually stop and buy 90 Octane marina gas, it runs great on this.

7,000 hrs! Enough said.

Its so depressing to see the current state of small piston GA being stuck with the crappy 1930's VW-like technology Lyc's and TCMs air cooled junk with all the technology advancements of the last 80 plus years relegated to the sideline.

The fact that we even have to ever think about valves, jugs, fuel delivery, engine management, shock cooling, etc in this day and age is pathetic.

Hopefully Rotax and like minded firms can lead the charge to update small GA propulsion past the era of Herbert Hoover.

I'm told that some budget 912s to 800 hours due to the TBO on the reduction drive. It has been said that you can sell at 800 hours and buy a new one and come out ahead. I really don't know but flying behind one in a Highlander there is some gearbox chatter if you don't keep it under a load. 5000 RPM seems to be the sweet spot for smooth running and getting at or over 100 mph indicated straight and level. It goes like stink!!!

I have a 912ULS in my Tecnam P2008. It serves me well when I'm not in my F33A.

For those not completely familiar with Rotax:

The Rotax is a different engine from what we are all used to. The 4-stroke Rotax 912/914 series are modern engines designed for auto gas. They drive the prop thru a gear reduction unit. They sound different and feel different but I think they are great little engines. Operation or maintenance is not what everyone is comfortable with. But treat them right and they are very dependable. If run mostly on avgas, Rotax recommends more frequent oil changes and the gearbox serviced at 600 hours. The service is very minor, relatively inexpensive, and requires a only few days if you send it to Lockwood Aviation in Sebring, FL. Lockwood also offers courses on the maintenance and care of Rotax engines.

Keep the carbs balanced (easy), don't idle at low RPM (at least 1900), do proper oil and filer changes and they run smooth and are happy. Before I learned anything about the Rotax I was concerned about the liquid cooling, but liquid cooling helps give them long cylinder life. The cylinders are uniformly cooled by liquid and air and consequently the cylinder barrels stay round during operation. I've been informed that ROTAX will not honor any warranty unless all the maintenance has been documented and performed by a Rotax certified Technician...due to the unique differences. BUT...Rotax certification and learning all the differences is easy at http://training.lockwood.aero/

Maybe one Rotax will make a 300 HP engine.

Not sure where you found that number. I have heard much shorter times than that. I will check with my colleagues at the predator office. We are developing a heavy fuel engine engine for that application. I seem to recall the rotax being pulled every 25 to 50 hours. Not for an overhaul obviously.

Hi Stuart-

I don't have much information that is relevant to your decision or thought process, but I did help my brother replace the Jabiru engine in his daughter's Legend Cub with a Titan O-340 with dual Lightspeed electronic ignition. The plane is a real rocket ship, and a blast to fly. With the electronic ignition, it seems to start just like a car, pretty much as soon as the key is turned. I think that the typical cruise will be at a very low % power.

I don't know what the announced closure of the San Antonio facility means for the Titan line of engines, but they seem to have enough presence in the market that I would expect manufacturing and support to continue.

Regards,

Bob