Today's Message Index:
----------------------
1. 10:39 AM - Stuck starter questions (Pat Little)
2. 11:59 AM - Re: Stuck starter questions (Alec Myers)
3. 08:02 PM - Alternator OV disconnect (Pat Little)
Message 1
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| Subject: | Stuck starter questions |
Many of the Z diagrams show the starter current passing thru the master
contactor as well as the starter contactor, and I gather this is to allow
for the possibility of the starter contactor welding itself shut. If that
were to occur then the pilot can disengage the starter motor by turning the
master switch off (having a "starter engaged" light and an e-bus alt feed
would both be useful for this scenario).
However, I see that Z-20 shows the starter current direct from the battery
to the starter contactor and not thru the master. Z-20 is for a Jabiru
system, and I have a Jabiru engine so I figure (no pun intended) that I
could use the Z-20 arrangement, although I don't know why Jabirus would be
different in this respect.
So, here are my questions: How unlikely is a welded contactor? How well
does the diode prevent this from happening? Is there a way to tell if the
diode has failed open-circuit?
Pat
Message 2
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| Subject: | Re: Stuck starter questions |
Can=99t speak for how common this is overall, but I=99ve had a s
tuck starter solenoid on both my TC aircraft.
On Oct 21, 2018, at 13:38, Pat Little <roughleg@gmail.com> wrote:
Many of the Z diagrams show the starter current passing thru the master cont
actor as well as the starter contactor, and I gather this is to allow for th
e possibility of the starter contactor welding itself shut. If that were to o
ccur then the pilot can disengage the starter motor by turning the master sw
itch off (having a "starter engaged" light and an e-bus alt feed would both b
e useful for this scenario).
However, I see that Z-20 shows the starter current direct from the battery t
o the starter contactor and not thru the master. Z-20 is for a Jabiru system
, and I have a Jabiru engine so I figure (no pun intended) that I could use t
he Z-20 arrangement, although I don't know why Jabirus would be different in
this respect.
So, here are my questions: How unlikely is a welded contactor? How well does
the diode prevent this from happening? Is there a way to tell if the diode h
as failed open-circuit?
Pat
Message 3
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| Subject: | Alternator OV disconnect |
In the (British) Light Aircraft Association=99s technical leaflet on
electrical systems it says it=99s better to disconnect a permanent-ma
gnet
alternator by interrupting the AC going into the regulator than the DC
output from the regulator. The Z diagrams that include PM alternators seem
to show the OV relay downstream of the regulator. Any thoughts on this?
Pat
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