Gyros - Electric vs Vacuum?

[Bill Denton]

I have noticed that American Champion offers three different panel "types"
on the Super Decathlon:

No gyro instruments.

Vacuum gyro instruments.

Electric gyro instruments.

I have read that aerobatic work is extremely hard on vacuum gyro
instruments, and that for an airplane doing primarily work, the no gyro
option is preferable.

So how do electric gyro instruments fit into the equation? Are they less
susceptible to damage from aerobatics than vacuum gyro instruments? Are
there any other advantages?

I'm not particularly interested in the performance of either gyro type
instruments during aerobatic maneuvers, as I understand neither type
performs particularly well. I'm thinking in terms of an airplane that would
be used for both "ordinary" flying, where gyro instruments would be
desirable, and for aerobatics, where gyro instruments aren't particularly
important. I'd like to know if replacing gyro instruments would be a once a
week operation under these flight circumstances.

What I'm primarily interested in is what sort of reduction you would see in
the service life of gyro instruments, and if there is a vastly different
reduction between vacuum and electric instruments.

Would it be possible to increase the service life of electric gyros by
powering them down and letting them spin down before beginning aerobatic
maneuvers? Would it be legal?

[Martin Hellman]

"Bill Denton" > wrote in message >...
> I have noticed that American Champion offers three different panel "types"
> on the Super Decathlon:
>
> No gyro instruments.
>
> Vacuum gyro instruments.
>
> Electric gyro instruments.
....
> So how do electric gyro instruments fit into the equation? Are they less
> susceptible to damage from aerobatics than vacuum gyro instruments? Are
> there any other advantages?

I can't answer the aerobatic Q or if there are other advntages, but do
know of a major disadvantage, at least within the experience detailed
below. They are highly failure prone and very expensive, both to buy
and fix.

I have a motor glider with no vacuum pump on the engine and the time
I'm most likely to need a gyro is if the engine won't start and I have
to descend through a cloud layer. So an electric gyro was really the
only option. I put an RC Allen Artificial Horizon in the plane, had it
fail after a few years and not work all that well during those years,
had it overhauled for $1k, and had it fail again soon afterward. When
I did an avionics upgrade, I pulled it out and now rely on my Garmin
196 (which has a gyro like page) for the small probability that many
things go wrong and I need a gyro. I'm also really careful not to get
into those situations, but fate can conspire against the best of
plans, so I wanted some backup option.

My experience with the RC Allen electric AH is not unusual, in fact
it's the norm within the fleet I'm a part of -- at least within the
part that has a gyro. (Most owners don't bother with any gyros since
we're limited to VFR flight.)

I also had heard similar stories of frequent failure from a flight
school that had a fleet of the older Katanas with the Rotax 912 engine
(similar to my 914) which also had no vacuum pump and RC Allen
electric AH's.

That said, the little checking I've done has indicated that most, if
not all, "reasonably priced" (under $3k!) electric AH's are relatively
unreliable, so it may not be just RC Allen. An electric turn and bank
gyro may be a different story since they are in more widespread use
and much cheaper.

There are some new solid state "gyros" out that you may want to look
at. Sounds like a much better approach in general and for aerobatics
particularly.

Hope this is of some help.

Martin