Lots of good questions. I can address some of them. Jason is well aware of
the problem of potential air in the fuel and has designed the fuel flow
through the system and back to the tank so that any air should be pumped on
through quite quickly. This part makes sense to me. As for redundency, it
is totally redundant with two complete systems: two fuel pumps, two sets of
injectors, two sets of sensors,separate electrical systems, etc. Only one
system is in operation at one time and you manually switch from one to the
other if needed.
Curtis
On Wed, May 13, 2009 at 11:34 AM, Frans Veldman <frans@paardnatuurlijk.nl>wrote:
> >
>
> 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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