Standby Vacuum?

: The reason why all electric panels are becoming common is because
: electrical systems are more reliable than vacuum, and backup is easier to
: provide for everything, a second battery. It also makes more sense to
: unify around a single system, instead of having a hodge-podge of two
: different systems.

Easier is relative. Designing a truly redundant electrical system is
nontrivial and expensive in both money, weight, and complexity. Strictly speaking,
you should have dual alternators, dual busses with crossover breakers, etc, etc. It's
not as simple as "throwing another battery" in the tail. If the system isn't designed
properly or is improperly operated, a failed system can break the other system.

The nice thing about the standard six-pack is that there's redundancy built
into the instruments and sources. Yes, vacuum systems are less reliable, but short of
something catastrophic, they are *completely* independent. It would probably be
better to transition to an electric AI and vacuum TC as "standard equipment"... or
maybe electric DG and vacuum TC. Still redundancy, but the likelihood of failure goes
down with the electric replacements. A vac pump going out on a standard plane (and
losing *all* bank except TC) is "unpleasant" and not that uncommon. Change 2 out of 3
bank instruments to be electric, rather than vacuum and one failure isn't nearly so
bad.

-Cory

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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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