>Your message said in part:
>
>> Our recommended wiring diagrams for amateur built aircraft
>> show single operator, two pole switches for the DC power
>> master switch and a pullable breaker for the alternator
>> feeding the alternator field. Alternator and battery
>> come ON and OFF together.
>
>I am having a problem applying this statement to the Rotax 914. There does
>not seem to be any way of controlling the alternator field. I have the
>recommended Europa wiring diagram which shows terrminal C of the regulator
>connected to positive battery through a 5 amp breaker. On the other hand
>the Rotax wiring diagram shows terminal C connected directly to terminals R
>and +B, with the additional caveat "never sever connection between terminal
>C and +B of the regulator, e.g by removal of a fuse".
>What is the best way of connecting the 914 to obtain the results in your
>message?
See http://www.aeroelectric.com/errata/fig_z7.pdf
>A second question:
>
>What would be the consequences of eliminating the master relay, and instead
>having a master switch that switched power to all systems except the wire
>to the starter relay. The only consequence I could see is that there would
>always be battery power to the starter relay, which could result in a
>problem if that component failed in the on position. (a highly unlikely
>occurence).
Starter contactors are the single most likely device to
stick shut in a single engine airplane. I'm personally
aware of two aircraft (a Vari-Ez and a Glasair wired
as you suggest) that suffered some damage to their
electrical system. One had a battery meltdown, the
other smoked a starter. If you elect to wire this way,
put the starter contactor as close as practical to the
battery (keep length of always-hot, fat-wires to a minimum).
I know that you have to throw away about an amp of
alternator capacity just to keep the battery contactor
closed but it is the more failure tolerant architecture.
Bob . . .
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