Questions Rotax Engines

Captain Wubba wrote:

Hello. I am currently evaluating engine choices for a possible sport
plane purchase. I'm a CFI, and have plenty of experience with planes
powered by Lycomings and Continentals, but never have flown one
powered by a Rotax. Specifically I am looking for information on the
Rotax 582 and the Rotax 912. If anyone could help me out, I would
greatly appreciate it. Especially appreciated are responses from
people with extensive experience with the engines themselves.

1. How reliable are the 582 and the 912. I have heard some bad things
about both, and some people speak of the the utter unreliability of
the 2-stroke engines like the 582. And experiences either way?

2. The 582 has a stated TBO of 1200 hours, and the 912 of 1500 hours.
Are these reasonable, or simply marketing numbers?

3. What are the ballpark overhaul costs of each engine?

4. What are the typical 'real-world' fuel burns per hour?

5. Do either engine have problems with vibration or any other specific
isssue that might make the plane they power less 'fun' to fly?

6. Do either of these engines have any especially nasty failure modes?
Compared to Lycomings or Contientals, are either of these engines more
prone to failure, or have there been any documented issues with engine
failure?

7. What kind of maintenance requirements are associated with each
engine? Are they relatively easy to perform preventive maintenance on?

I greatly appreciate any help that anyone might be able to provide.

Thanks,

Cap


First, when you come across those 582's with a real 1200 hour TBO, I
want several,,,,,,,,,

also, I've heard that the Lyc's possible blow oil all over your
windshiled,

this does not happen with two strokes, especially pushers, that's the
good news,

your questions indicate you should stay with the big four
strokes,,,,,,,,there are not good answers to them for sure,,,,,,,
--


Mark Smith
Tri-State Kite Sales http://www.trikite.com
1121 N Locust St
Mt Vernon, IN 47620
1-812-838-6351

Hello, I don't propose to be an expert but here are some thoughts (on the
912 only):

"Captain Wubba" wrote
Hello. I am currently evaluating engine choices for a possible sport
plane purchase. I'm a CFI, and have plenty of experience with planes
powered by Lycomings and Continentals, but never have flown one
powered by a Rotax. Specifically I am looking for information on the
Rotax 582 and the Rotax 912. If anyone could help me out, I would
greatly appreciate it. Especially appreciated are responses from
people with extensive experience with the engines themselves.

1. How reliable are the 582 and the 912. I have heard some bad things
about both, and some people speak of the the utter unreliability of
the 2-stroke engines like the 582. And experiences either way?


The 912 is OK provided that you know and care for its idiosyncrasies. It's
different than traditionals, but reliability is similar.

2. The 582 has a stated TBO of 1200 hours, and the 912 of 1500 hours.
Are these reasonable, or simply marketing numbers?

If properly cared for, it seems reasonable for the 912. It was recently
upped from 1200 hrs.


3. What are the ballpark overhaul costs of each engine?

4. What are the typical 'real-world' fuel burns per hour?

For the 912, I've logged 3-4 gph.


5. Do either engine have problems with vibration or any other specific
isssue that might make the plane they power less 'fun' to fly?

Being a geared engine, if you reduce power too abruptly there may be some
unusual noise/thumps if the propeller gets into "braking" mode. Nothing to
worry about in normal operation.

The100hp 912S has a service bulletin about vibration issues in some cases,
but frankly I'm not sure if it's the engine, the propeller or the engine
mount that has been the problem. It is important that the twin carburetors
are properly synchronized, but this is a normal maintenance item (albeit
maybe unfamiliar to those used to traditionals).

6. Do either of these engines have any especially nasty failure modes?
Compared to Lycomings or Contientals, are either of these engines more
prone to failure, or have there been any documented issues with engine
failure?

Compared to what I've read about cylinder cracks etc. on traditionals, the
912 seems to be rather tolerant of in-flight mis-handling (such as shock
cooling), but it needs to be maintained OK. I haven't heard of an in-flight
failure yet here in Finland. The engine needs to have the correct type of
oil (important as it also lubricates the gearbox), and it likes to be run on
automotive gas (95 octane or more) rather than 100LL which is harder on the
oil and the plugs.

7. What kind of maintenance requirements are associated with each
engine? Are they relatively easy to perform preventive maintenance on?

I have little comparative experience, but did not find the 912 very hard.
Just follow the book rigorously. Ignition and valves are maintenance-free,
but on the other hand there are some oddities like checking of the friction
in the propeller slipper clutch. Also the carburetor mount rubber sleeve may
be prone to cracking and must be checked, but this item is also well pointed
out in the book.


I greatly appreciate any help that anyone might be able to provide.

As I understand the US situation, the main issue is that local FBOs are on
average not yet very familiar with the engine and may not be able to give
the familiar level of support . But there are some knowledgeable places
(Phil Lockwood's operation being one of them from what I've read) and
following their expertise, operation of the 912 should be ok. I went to a
one-day course organized by our local Rotax support facility and it was very
useful, and recommend any Rotax user to do the same.

I've flown behind a 912 and had no issues during that time. No
experience with the 582 so thats pretty much the limit of my anecdotal
information. The rest that follows is pure editorial.

I've been looking at similar sized engines and have come to the
conclusion that there is a gradiant of power/weight vs. reliability
that you have to pick from. The key to high power to weight is revs.
Diesels on one side, 2 stoke gassers on the other. Engines that give
a lot, and weigh a little, are not as fool proof, or run as long
between maintenance (e.g. 2 strokes). Engines that are more robust in
their ability to handle mishandling, are heavier for a given output (4
stroke). So this puts you in the position of trading risk against
performance. So what you tend to see is people put the
light/powerful/risky engines in aircraft that can land anywhere
anytime, and they put the heavier robust engines in aircraft that go
fast and need a paved runway.

There are exceptions like little racers that go 200MPH on a 582, which
rachet the risk all the way in one direction. And there are little
put-put airplanes that carry little more than a heavy robust engine
and the pilot, and go nowhere fast but are really safe.

Sometimes a 582 (or similar) will be used to enable a design that was
really too heavy in the first place. Various miniature heli's and
high wing loaded planes have been seduced into this. Its a recipie
for disaster.

My choice is leaning towards the Rotax 914 because at least it is a 4
stroke, so you're further along on the robust side of things, and it
can make power way up high for XC, and its under $20k new.

The other approach which has been written up here quite a bit is to
try to exploit the composite reliability of 2 high reving light
engines with the idea that if one of them quits, you can sustain
flight to your paved runway. Problem is, no good kit aircraft exist
designed with that idea in mind. The goal is a power plant with the
power to weight of a 2 stroke, and the reliability of a 4 stroke (in a
fail soft mode).

Regards

(Captain Wubba) wrote in message . com...
Hello. I am currently evaluating engine choices for a possible sport
plane purchase. I'm a CFI, and have plenty of experience with planes
powered by Lycomings and Continentals, but never have flown one
powered by a Rotax. Specifically I am looking for information on the
Rotax 582 and the Rotax 912. If anyone could help me out, I would
greatly appreciate it. Especially appreciated are responses from
people with extensive experience with the engines themselves.

1. How reliable are the 582 and the 912. I have heard some bad things
about both, and some people speak of the the utter unreliability of
the 2-stroke engines like the 582. And experiences either way?

2. The 582 has a stated TBO of 1200 hours, and the 912 of 1500 hours.
Are these reasonable, or simply marketing numbers?

3. What are the ballpark overhaul costs of each engine?

4. What are the typical 'real-world' fuel burns per hour?

5. Do either engine have problems with vibration or any other specific
isssue that might make the plane they power less 'fun' to fly?

6. Do either of these engines have any especially nasty failure modes?
Compared to Lycomings or Contientals, are either of these engines more
prone to failure, or have there been any documented issues with engine
failure?

7. What kind of maintenance requirements are associated with each
engine? Are they relatively easy to perform preventive maintenance on?

I greatly appreciate any help that anyone might be able to provide.

Thanks,

Cap