p.mulwitz(at)worldnet.att
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 Posted: Thu Dec 07, 2006 11:01 am Post subject: Jabiru Starter contactor and solenoid |
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Hi Clive,
I took a quick look at your wiring diagram. This is the first time I
have actually seen one for a plane, so many things were new to me.
First, let me say the diodes are correctly wired up for the solenoid
and relay. If you put these in backwards, they will probably blow
out as soon as the battery is connected due to very large current and
no fuse. That suggests the idea that a fuse for the actuator coil
circuit would be in order. I have no idea how much current might be
conducted through the coil since there is no load resistor for this
DC circuit. There may be one installed in the actual solenoid or an
implied resistance from the wiring of the coil. Probably the
standard practice would be the thing to do. If this were not a
circuit that has been wired up a few million times per year since the
flood, I would include a resistor and fuse in the actual switching
circuit for the master relay and also the starter solenoid.
There does seem to be a fuse for the starter solenoid called
"Instruments" and limited to 10 amps. Again, I have no idea how much
current the starter solenoid uses for switching the primary current
to the starter.
I would suggest a review of the fuel pump circuits by someone more
experienced than me. The diodes look funny. I can't imagine what
their purpose might be. Also, I don't see the point of having 10 amp
fuses in series to each fuel pump. One for each pump should
suffice. If two are needed for some reason then it seems the first
one should be 20 amps to allow for each fuel pump to draw 10 amps as
allowed by its fuse.
I am also a little confused by the alternator hookup. This is no
surprise since I have no experience with this kind of circuit. My
memory as a Cessna pilot is that there should be separate master
switches for the alternator circuit and battery circuit. This allows
for separate control so a faulty circuit can be shut down while still
supplying power to avionics and other stuff. This diagram seems to
wire both sides of the master switch for battery function and not any
for the alternator. Again, I would suggest a review of this function
by someone more familiar with common practice in airplanes than I have.
Best regards,
Paul
At 12:08 AM 12/7/2006, you wrote:
| Quote: | Hi Matt and Paul,
Paul's summed up the issues and I've already wired my latest Jabiru
as he has recommended.
The only issue he didn't mention is starter solenoid sticking.
What do you do in the unlikely event that the starter solenoid
(contactor/relay) sticks closed?
With the master contactor powering everything you merely open the
master and all goes quiet. If the starter solenoid is wired direct
you can't do this. A 'starter engaged warning light' powered from
the starter feed is also a good idea to warn you off this problem.
Regards, Clive
P.S. I've sent my latest wiring diagram to you direct for
information. If you see anything wrong with it let me know!
Send instant messages to your online friends http://uk.messenger.yahoo.com
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Paul Mulwitz
32013 NE Dial Road
Camas, WA 98607
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