Paul & Gilles, I missed the beginning of this thread, but I am impressed
that if you wire your 914 fuel pumps according to the diagram that came from
Europa with mine, then you can switch off main switch and alternator switch
and one pump carries on - supplied directly from the alternator. It wouldn't
matter if the rest of your electrics were totally fried. Alternatively you
could have a blown alternator and power the other from the battery with the
alternator switched off, and inessential electrics switched off.
I went some way to proving the former point when I managed to
switch both Main & alternator switches off with my left trouser leg (having
lifted my leg to replace my pee bottle under the L thigh support!), over
rather inhospitable countryside near the German/Czech border - nothing but
forest. All the dials were blank but the plane went merrily on while I
sorted it out.
The latter situation is a bit like that I found myself in having
just departed the Belgian coast for Dover, and the regulator packed up
completely. The essentials (a radio and a fuel pump) took very few amps and
I readily persuaded myself that my 16 amp/hr battery would get me to the
other side, which it did and more. So you do have electrical redundancy in
the sense that you only need either the alternator or the battery to be up
and running.
Regards, David Joyce, G-XSDJ
----- Original Message -----
Sent: Wednesday, July 26, 2006 6:21 PM
>
>
> why not wire the
> > essential fuel pump directly off the battery - would you not then
> > have a working pump to get the aircraft down.
> >
>
> Hi Paul,
>
> This is a good question. The diagram suggested by Rotax is far from being
satisfactory. It does not provide electrical redundancy for the fuel pumps.
Don't know about the Europa schematic, but chances are they followed Rotax.
>
> It is far safer to run the pumps direct from a more reliable power supply,
eg a battery.
> This is what I did in our 914. For those interested, there are some
details on my website.
>
> Regards,
> Gilles Thesee
> Grenoble, France
> http://contrails.free.fr
>
>
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