Stefan wrote in
:

Not that I want to excuse those system failures the least bit, and not
that I would not have an adrenaline rush in that situation, but there
*are* manual back ups for the critical items! At least in those planes
I've seen so far, there has always been a "steam" AI, a "steam" ASI, a
"steam" altimeter and a whisky compass. You can perfectly fly in IMC
with this equipment.

Sure, you can keep the plane aloft, but how would you navigate or fly an
approach? By the compass and Dead Reckoning? I guess it's not that much
different than an alternator / battery failure. But I think a total
electrical system failure is pretty rare. And while often missed, there are
warning signs that can give you advance warning of an impending electrical
failure so that you can get to safety (VFR or on the ground) before you are
left without effective navigation instruments (VOR, GPS, etc.). You can
even control the amount of time you have by reducing consumption (ie:
turning stuff off) and saving it for the necessary phases of your flight.

Sensors fail frequently by comparison. Hell - fuel system sensors fail so
frequently that every pilot I know checks his fuel level visually because
the fuel sensors can't be trusted. There are even discussions about whether
a fuel sensor that reads empty all the time is legally considered failed!

There is built-in redundancy in the airplane electrical system - you have
an alternator and a battery. Having your redundant electrical system
essentially undermined by a poorly designed glass panel that fails
completely when any one sensor misbehaves is unfortunate at best, and is
added risk that seems unjustifiable.