On 09 May 2004 22:12:21 GMT, (Jay Masino)
wrote:

Jay Honeck wrote:
This whole topic drives me crazy, since the idea of a "vacuum system" is
ridiculous in the first place.
I'm stuck with one, and have replaced both of my vacuum instruments in the
last six months. Why? Because the danged electric replacements are
absurdly over-priced, and the back-up battery that would make an
all-electric system prudent (and legal) is even worse.
Personally, I think the fact that we're flying around behind vacuum
instruments in the 21st century is patently absurd.

I suspect it's a lot easier to get a gyro to spin at 10 or 15,000 RPM (or
whatever) using vanes and vaccum, than it is to design a reliable electric
motor to spin the gyro at that speed. It can obviously be done, but I
suspect the parts neccessary to do it might be a little more exotic and
expensive than vaccum gyro parts. Add to that the immense liability that
a manufacturer of such devices are taking on, you start to see why all of
these devices are expensive (even the vaccum devices, really).

Turn coordinators spin a gyro with an electric motor, but I bet the fact
that horizons have to pivot in two directons (roll and pitch) makes the
internal design way more complex.

As long as we are talking about conventional gyros, it doesn't matter
if they are vacuum or electric driven. Since they have moving parts,
eventually they will fail. On the other hand, accelerometer based
electric 'gyros' have lifetimes well beyond airframe life.

Jay's original comment of the absurdity of vacuum systems is dead on.
But the solution isn't to replace with electric gyros, the solution is
to replace with solid-state ones.

-Nathan