ALAN YERLY wrote:
> If you don't have an engine yet for your project, consider this:
> http://www.extremeaircraftengines.com<http://www.extremeaircraftengines.com/>
I have been looking quite some times to this website in the past.
Problem is that this guy appears to be an "engine-guy", and not a pilot.
Lots of pictures, lots of hurray talk about fuel injection, but no real
"pilot information."
What I would like to know, before considering to use such an engine is:
1) What is the weight penalty compared to a standard rotax 914?
2) How does the injection system cope with avgas? Will the injectors
clog due to the lead over time? Who is going to find out what happens then?
3) What do they mean with "redundancy"? Nice to have two computers, but
if they use one set of sensors, one set of cables, and one set of
injectors, well, it actually doesn't provide much redundancy at all.
4) How much electrical power do you need to operate the engine in case
of alternator failure? I assume that the high pressure fuel pump uses a
lot more juice than the standard low pressure rotax fuel pumps. How
large (and heavy) has the battery to be to provide one hour of flight?
5) How does the engine behave if it swallows an air bubble in the fuel?
Not much of a concern for a car engine, but aviation engines see quite
some air. It is common practice to run one tank empty, and then switch
to reserve. Also, with a partially filled tank, in turbulence there is
quite some sloshing of fuel, and as a result quite some air suspended in
the fuel. If the injectors/high pressure pump can not handle air bubbles
(as is common in fuel injection systems), well, one day you are going to
have a problem, or you can only fly with a tank at least halfway filled
to stay out of problems.
Well, actually I do have many more questions, but it would be nice to
see some of this covered on the website. At least, this would give the
impression that the engine builder is aware about what is important for
us pilots.
Also, keep in mind that the engine setup is changed significantly, and
that users are the genuia pig. Even with the standard rotax, there have
been unforseen surprises (hence all the service bulletins). Stupid parts
like rubber carburetor flanges can cause an engine failure. In case of
fuel injected engines, one has to start all over again with experiments.
Nothing wrong with that, if you really understand the risks and are
willing to take them.
Having said all this, I think that fuel injection is the way to go. It
just has to mature a little for aviation use. And I would really love to
see a website with important information *for pilots*.
--
Frans Veldman
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