Lycoming or Rotax

BAH!!! · Post by **BAH!!!** » Tue Feb 24, 2004 8:00 pm

Which engine do you think is more reliable\better?

....or another way of looking at it....

Plastic planes or metal planes??? What would you choose?

Right Seat Captain · Post by **Right Seat Captain** » Tue Feb 24, 2004 8:24 pm

Now now, rotax does not mean plastic, nor does lycoming mean metal. Lycomings can be found in a Cirrus, a composite aircraft, likewise rotaxes are finding themsleves in many homebuilts that are metallic.

Rotary engines are a much lighter engine for the power they provide. However the technology to create a rotary engine that can match the high end of 'traditional' internal combustion engines is not yet affordable. Rotaxes are becoming the engine of choice for those who need a lightweight solution for their aircraft. Lycomings though will be used in the high end power range until a Rotary can produce the same power for the same amount of money.

In terms of reliability, from a mechanical standpoint, rotary engines are less complex and there's less that can go wrong. Lycoming's on the otherhand have numerous problems that plague the performance constantly, such as leaks, improper oil flow...

If you want reliable efficient power, go with a rotax, if you want more horses, for now you have to stick with a lycoming.

brokenwing · Post by **brokenwing** » Tue Feb 24, 2004 8:47 pm

Isn't rotax the rotating plate in the intake of a piston engine, Trade marked by bombardier?. I think it kinda has the same function as reeds do in the 2 cycle engine as is most rotax engines (except the 912).
rotax ultralight engines have a nasty habit of ceasing up. I think it might have something to do with the crank bearings/bushings? being made of some kind of plastic.

Rotary engines should in theory be far more reliable than any piston engine because the rotary only has one moving part.

N2 · Post by N2 » Tue Feb 24, 2004 8:51 pm

I thought I would share my experience with you guys. I had a fellow redo my Lycoming a few years back who had just come back from Austria.(factory trained Lycoming engine over hauler for the past 25 years) He was there to take the Rotax factory training and when he got back I asked him what his first impressions were and here's basically what he told me. Not bad but nothing near as sturdy as the Lycoming and he really didn't view them as an honest aircraft engine as of yet. Remembering that this is only one person’s opinion of them, I’m sure you could find others who swear by them. I do know a fellow who's had a few engine failures with the Rotax and he is definitely not impressed by them at this time. Perhaps just growing pains for Rotax and who knows but as of this instant my money stays with Lycoming....till the Delta Hawk comes out that is!

BAH!!! · Post by **BAH!!!** » Tue Feb 24, 2004 8:58 pm

Yeah, I also know a guy who has had a couple of his rotax powered planes blow a hole in the engine. Howerver, as far as I know, he still swears by them.

Right Seat Captain · Post by **Right Seat Captain** » Tue Feb 24, 2004 8:58 pm

I thought Rotaxes were rotary engines. But if I'm wrong, then I have no idea whether Rotaxes are more reliable or not. But can someone confirm that a Rotax is not a Rotary? If not, has anyone tried putting a rotary engine into an aircraft. I suppose it might have too high an RPM for a directly connected shaft, but it could be geared. Or I'm sure it can be modified to have a lower RPM.

Another question, which is better? Continental or Lycoming?

oldtimer · Post by **oldtimer** » Tue Feb 24, 2004 9:22 pm

My money is on the Pratt PT6A-60A in the Beech 350. A fine combo. (If your not the one paying) Just kidding. Incidently, has anyone ever heard of someone using a jet fuel starter out of a US Navy jet. A friend of mine in Edmonton was considering it for his Rand KR2. 'bout 80hp if I remember. Used to start Corsairs or some other Navy jet.

loopy · Post by **loopy** » Tue Feb 24, 2004 9:26 pm

A Rotex is not a rotary. If you are interested in rotary engines in aircraft look up the websites for powersport aviation (convert a mazda rotary for a/c use) and I beleive Mid-west aero engines , or something similar, out of the UK. They have a certified engine in the 75-110hp range.

624 · Post by **624** » Wed Feb 25, 2004 12:17 am

As loopy said, Rotax engines are not rotary. These engines have been around for quite a while, although maybe not as long as Lycomings. They've been in skidoos and utralights, they're also a certified aircraft engine. The one I'm familiar with is in a Diamond Katana, has a 83 hp rotax with a constant speed prop. It cruises at around 100 knots and uses about 4 gallons per hour.
The thing I don't like about them is there are a lot of extra parts on them compared to a lycoming, so possibly more to go wrong. But the nice thing about them is they are high tec compared to lycoming.
For example, you can find the same ignition system and carburator on any old 1950's or 60's tractor as you will find on the new lycomings today.
I guess if it's not broke, don't fix it.
But on the other hand with the advances in electronic ignition and fuel systems why not take advantage of that. (Mainly because of liability, but thats a whole other topic)
The 912/914 rotax seems to be holding it's own from what I hear. I think they have a 1500 hr TBO( in commercial ops), maybe 1700hrs. and some companies are running them on condition to around 2500hrs. no problem.
They are also fairly pricey, around 25,000.00
If I remember right that is outright price, no exchange. The cores are worth about the same with 1700 hrs or 2500hrs. (not very much)
Anyway, that's my opinion on these engines.

ahramin · Post by **ahramin** » Wed Feb 25, 2004 12:44 am

Rotax are not rotary engines. There are a few C150s and quite a few homebuilts out there with Mazda rotaries.

The biggest problem with the Rotax seems to be that they blow up and seize. My limited experience with them leads me to beleive that they are just not able to deal with the changing operating conditions (temp, humidity and pressure). The jets do not meter the fuel properly and you blow an engine because it overheats.

I saw the new six cylinder bombardier at oshkosh on the murphy moose and it was quite quiet and is one of the only aviation engines out there which are not sixty year old tractor engine technology. I do not like the idea of a reduction gear though, not necessary and one more thing to go wrong.

Any engine i am going to buy is going to come from aero sport power in kamloops. Start with a proven reliable lycoming and then put new technology into it. Fuel injection, electronic ignition on one side, high compression cylinders, may even get a turbo for the next one. These engines are supremely reliable, very smooth, and put out a ton of power as well.

Even if i had to get a certified engine i still think i would stay with a lycoming or continental. There are some problem engines out there but they are all identified and it is easy to stay away from them. Simply would not trust a snowmobile engine over the rocks or water.

I like the new aero deisels though. I really think we should all be gearing our aircraft towards these engines. They are supremely simple, have very little to go wrong, and will burn anything and everything, including fuel distilled from used McDonalds vegetable oil if that turns your crank. If i had to get a certified engine i would go with one of these if they were even moderately close to a new avgas piston.

ahramin

linecrew · Post by **linecrew** » Wed Feb 25, 2004 7:06 am

Is it not true that Diamond Aviation stopped pushing the Rotax powered Katana's because of poor sales and reliability issues? The marketing focus seems to be more on the Katana C1 with the Continental engine.

My preference is to the Continental powerplant since I know of 4 instances around my home airport alone of Katana's having engine failures in flight.

Also, from purely an athetics point of view, the sound of those Rotax engines is just disturbing.

HoCapt · Post by **HoCapt** » Wed Feb 25, 2004 7:20 am

My sled has a Rotax engine in it. Very powerful for the size, and that thing starts no prob in -30C weather. (no pre-heat) Not too sure of the similarities in the aviation models, but I'd trust it in a bird.....

phillyfan · Post by **phillyfan** » Wed Feb 25, 2004 8:21 am

Now take that sled out in the summer and giver wide open for an hour or two.
I've had 2 engine failures on snow machines, 2 in airplanes and 1 in a rotax ultralight. The difference is I probably only have about 50 hours on snow machines and only did one flight in an ultralight.

ndb · Post by **ndb** » Wed Feb 25, 2004 8:38 am

I've been told of a guy called Claude Roy who has had 21 - count them, twenty-one - engine failures in rotax-powered ultralights.

I don't know anyone who has had anywhere near that number of failures behind a Lycoming.

You might grumble about a Lycoming - sure, it's heavy, and the cam lobes spall - but the cylinders can take amazing shock-cooling abuse, and the crankshafts and crankcases are incredibly tough.

Sean Tucker does multiple +12G snap rolls at 240 mph on vertical downlines with his Lyc 540, year after year after year. Using the 2/3 rule from _Aerodynamics For Naval Aviators_ that's roughly equivalent to an straight +18G pull. Try that with a rotax.

Rotax engines on ultralights don't even have carb heat! Can you say "flight safety issue"? I knew you could ... and look closely at the fuel system on a rotax sometime. Try not to have nightmares afterwards.

ahramin · Post by **ahramin** » Wed Feb 25, 2004 11:41 am

Sure Tucker is rough on his 540, he also has a new engine every season. It is not like Bob Hoover who was so nice on the engines that they looked like new after 1000 hours. The fact that Tucker can abuse his engine does not mean that the engine does not suffer from that abuse.

ahramin

Youngback · Post by **Youngback** » Wed Feb 25, 2004 1:27 pm

I never had a problem with any of the rotax engines that I have flown. They were in light aircraft though and not in ultralights. The ultralight 2-stroke models of rotax engines I've been told do have design issues though. Also the rotax 912 I believe now has a life of 3200 hrs before the engine must be replaced (REPLACED not overhauled). I may be mistaken but I know of the demise of two katana operators due to this problem. The 914 is a new design and very reliable but who knows if in the future it may be hit with similar problems to its predecessor. I'd say go for Lycoming based on their history and tolerance to abuse but rotax if cost and weight is important.

PS. Linecrew, where are you from?

PPS. I liked the sound of a rotax. Not nearly as much as I like a radial but you hear the lycomings and continentals all over the place and a rotax is a nice change.

Right Seat Captain · Post by **Right Seat Captain** » Wed Feb 25, 2004 3:09 pm

ndb wrote:I've been told of a guy called Claude Roy who has had 21 - count them, twenty-one - engine failures in rotax-powered ultralights.
...
Rotax engines on ultralights don't even have carb heat! Can you say "flight safety issue"?.

Ummm...can you say fuel injected?

Anywyas, I do agree the engine failures do happen more often in ultralights, but from what I've seen, it's usually because the drive belt snapped. I can't believe they have a rubber band turning the prop. Belts are prone to failure. In first year engineering, students are taught belts are meant to be replaced on a regular basis. If you want a more permanent solution, look to gears. Why would they use a method they know is prone to failure to turn the prop.

ahramin · Post by **ahramin** » Wed Feb 25, 2004 5:34 pm

Anytime the question is why, the answer is money.

They use a belt because it is in a location which is easy to inspect and a big reduction gear drive would be too heavy and expensive. Why pay for that when a belt will do the job safely (with regular inspection, replacement).

NDB, i guess i must fly really unsafe airplanes as neither of the RV-8s i fly have carb heat.

Damn, neither did the Extra 300.

OH NO, THE KING AIR DOESN'T HAVE IT EITHER.

SMEG, I HAD BETTER TELL THE CHEIF PILOT ABOUT THIS RIGHT AWAY.

ahramin

Driving Rain · Post by **Driving Rain** » Wed Feb 25, 2004 7:11 pm

Most of the Rotax engine failures happen on their 2 cycle engines. 2 cycle or 2 stroke engines are used in the ultra lites because they are small and develop a greater amount of torgue and horsepower per litre than equivilant 4 stroke engines. They get the 2 stroke moniker because the piston has a power stroke every second revolution where as the 4 stroke every 4 revolutions. The 2 strokes life on this planet is short lived because they are by far the biggest polluters in internal combustion engines. The engines require oil to be either mixed with the fuel or injected in the combustion chambers to lubricate the cylinders. In the cleanest and latest 2 cycle engines 1/2 the oil is spit unburned back into the environment. Just follow most outboards on a lake and enjoy the stick of rotten dinosaur. 2 strokes are notorious for engine failures especially the air cooled variety. They're put in Jet Ski's, snowmobiles, some motor cycles, ultra lites , chain saws and lawn mowers anywhere a light and powerful engine is required. Friends don't let friends fly 2 strokes.

Bombardier recreation products owns Rotax Austria. Rotax also manufactures a family of 4 stroke or conventional cycle engines. They range from the 912 and 914 turbo, 80 to 100 hp engines and they are Transposrt Canada certified real aircraft engines. Like the poster above mentioned Bombardier unveiled the latest offering from Rotax at Oskosh this last August, a pair of V6 engines. One is 220 hp naturally aspirated and the other is iturbo charged to 300 hp. Both are water cooled and compare very favourably to the weight of equivalent air cooled engines in that power range. The 300 horse model weighs in a 412 lb compared to a turbo Continental or Lycoming at 425 to 430 lbs. The real savings will be in fuel economy and both models feature triple redundant electrical systems. The Rotax has a .413 lb/hp fuel rating where as the Lycoming or the Continental is much much greater. What this means is simply by swaping a Rotax for a Lycoming the same aircraft will gain 1/3 more range on a given fuel load. Because they are V6's they will be very smooth. I wouldn't be afraid of the gear reduction units because most aircraft engines use them. They are on all turbo props be they PT6 or Allison and most large radial P&W and Wright's

By the way a "real rotory" engine like the WW1 Spads, Fockers and Sopwiths had, the crank shaft was bolted to the fire wall of the aircraft and the whole engine assembly cylinders and all rotated around it. Unbelievable torgue!!!!! The engines had no throttle but were turned on and off by killing the mag, they were also 2 strokes that burned castor oil. I wonder if the pilots wore diapers?
What everyone today calls a rotory engine is really a Wankel developed by a Dr. Wankel in Germany after the war. Lots of manufactures have tried to get one to run right but only Mazda had been successful.

Cheers Pete

ahramin · Post by **ahramin** » Wed Feb 25, 2004 7:23 pm

When we talk about rotaries today we are talking about Wankels. Wankels have triangular pistons which rotate rather than going up and down. They are not a "reciprocating" engine.

And about the Bombardier V6 and smoothness, The one on the moose was a 300hp turning a 3 blade prop. It was so smooth that there was basically no vibration felt in the cabin.

ahramin

Cat Driver · Post by **Cat Driver** » Wed Feb 25, 2004 7:25 pm

Well I'll be double damned.

Where in hell did you get to be so knowledgable about engines Pete?

Don't tell me you take time out from flying those neat OMNR machines to delve into mechanics.

The last time we were together your mechanical expertise was limited to snapping the caps off beer bottles.

Got your e-mail and will eventually answer it, I'm really into procrastinating lately.

P.S.

Good post on engines, I'm proud of your progress...can you still snap beer bottle tops?

Cat Driver

Driving Rain · Post by **Driving Rain** » Wed Feb 25, 2004 9:29 pm

Cat Driver,
I know llittle bit about engines. I've always loved working on them helping my Uncle Joe work on em since I was kid.
I was lucky enough to grow up in a community in Southern Ontario when Avro and Orenda were going concerns. My next door neighbour was a design engineer with Orenda and one of my good friends father was one of Rolls Royce's top engineers and at one time worked with Whttle at Power Jets, between the pair of them they held many many patents for one thing or another found on todays gas turbines. I spent many hours listening to them. Both had thick Scots brogues and were kind enough to speak to me in langage that was plain enough for me to follow.

I'm working on an engine that runs on Beer. All I've got to do is figure out how to get three finger shaped rods to snap at the correct moment and hurl a beer cap shaped saucer into the air. I'm looking for a test pilot are you still doing that kind of work? Of course I consider this engine to be a life's work and will gladly demonstrate the principles over a Heiniken.
Cheers Pete

Cat Driver · Post by **Cat Driver** » Wed Feb 25, 2004 9:39 pm

I shure will stop in when we come down that way in the motor home.

As soon as I get these two f.... Cessnas sold we are going to take off in the motor home...

I stilll have not heard about the Brazil contract so have no idea what is going to happen there.

By the way do you remember my quitting drinking booze in 1985?

Haven't had a drop since, but would love to watch you get into it..

.

Driving Rain · Post by **Driving Rain** » Wed Feb 25, 2004 9:48 pm

. yes I remember.
I wish you'd talk to my wife she hates it when I get into it. I have firm rule now about drinking I only drink when I'm alone or with other people but she isn't satisfied.
You better stop in if your going by. I've never had a beer in your motor home I can hardly wait.
Cheer Pete

N2 · Post by N2 » Thu Feb 26, 2004 3:40 pm

While I was Oshkosh this past year I was particularly interested in power plants as I hope to power my RV7 with a newer technology rather than the old Lycoming or Continentals. The diesel really seems to show promise with a great reduction in moving parts, lower specific fuel consumption, no electrics to worry about failing (mags, plugs) and state of the art fuel injection. The other benefit to the diesel is that it will burn a variety of fuels but is really designed to burn jet A which is cheaper than avgas. Oh did we mention torque? Bags of the stuff!

I also looked at the new engine from Bombardier and it looks attractive as well but a tad more expensive than the Delta Hawk and was informed that the engine will not be available for purchase for some time yet by homebuilders. Whether or not they stick to this plan I guess will remain to be seen. One good thing about the L & C’s is that they are well proven and are reliable as hell.

Now I hear rumours that Honda is almost set to release a new piston engine but I really don’t have any details on that as of yet, perhaps someone else might have a bit more insight into that engine. Rest assured if it comes from Honda it will probably be a very refined piece of machinery!