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