> ...are not "two independent sources" a
> battery and an alternator, just as an engine-driven pump and an electric one
> are two independent sources of pressure?
> What am I missing?
> Cheers, Ferg
I believe FAA's answer would be not if one can affect the other. An
overcharging alternator can ruin the battery, especially an RG type. A
failed battery can ruin the alternator regulator. Even if there's
adequate means to notify the pilot, who can promptly switch to battery
only, there's no way to know if the capacity in that battery will be
sufficient to keep the pump running long enough, in addition to holding
the battery relay closed, to avoid an off-airport landing...or whatever
better term local TV news will use to describe the event!
Regards,
Fred
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