Standby Vacuum?

Our club is looking at upgrading a couple of airplanes to Garmin 430s, etc.

It seems to me that standby vacuum would be a good thing to add, too.

1) Good idea? Do these systems really work?

2) Recommendations on type/brand/model?

TIA

What kind of airplanes do you have? I can understand wanting attitude
indication redundancy in a Bonanza, but it's overkill on a Skyhawk.

Do you have redundant attitude gyros? I've seen more of those fail
than dry pumps, never mind wet.

There are two basic approaches - tapping the intake manifold (which
means full throttle is no longer available if you want vacuum), and an
electrically driven backup pump (which adds weight). Decide whether
you want to carry the extra weight around all the time, or whether you
want to limit yourself to partial power when the vacuum fails. Both
systems work.

I think that if you really feel the need for redundancy, the sensible
solution is replacing the T&B with an electric AI.

Michael

Michael wrote:

I think that if you really feel the need for redundancy, the sensible
solution is replacing the T&B with an electric AI.

I see that Sporty's is encouraging this option, too, with their electric
AI.

However, doesn't the AI have the potential to tumble in an unusual
attitude? During my IFR training I recall learning that the turn
coordinator will not tumble in an unusual attitude scenario whereas the AI
may. Since recovery from an unusual attitude was taught to me by first
going to the TC, I would be hesitant to replace an instrument so reliable
during a UA.

What say you?

--
Peter
























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However, doesn't the AI have the potential to tumble in an unusual
attitude?

You know, I've heard that too. And it sure seems like it could, by
design. Only thing is, I've spent a lot of time teaching unusual
attitudes - and I've never seen it happen. I think you need something
more radical to happen than what we think of as an unusual attitude -
more aerobatic.

I see little chance of that happening with dual AI's, and even less
chance that the average pilot will recover from an aerobatic attitude
partial panel after screwing up enough to get into that mess.

But hey - if you have the panel room, why not keep the electric TC too?

Michael

Michael wrote:

I see little chance of that happening with dual AI's, and even less
chance that the average pilot will recover from an aerobatic attitude
partial panel after screwing up enough to get into that mess.

Interesting that you pointed that out. I was thinking the same thing when
I posed the question but thought that two tumbling AIs would pretty much
guarantee that the pilot would not recover.

But hey - if you have the panel room, why not keep the electric TC too?

My Bonanza has the original TC along with a backup electric AI located to
the left of the TC. However, the electric AI keeps precessing and requires
a reset about four times per hour, which concerns me.

--
Peter
























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Interesting that you pointed that out. I was thinking the same thing when
I posed the question but thought that two tumbling AIs would pretty much
guarantee that the pilot would not recover.

I agree with you - with two tumbled AI's and no TC, recovery is
impossible. With a working TC, it is merely highly unlikely.
Therefore, if the panel space is there, it might make sense to keep the
TC. Not much sense, mind you, because if you manage to screw up badly
enough to put the plane into an attitude that would cause both AI's to
tumble, well, I'm willing to give very good odds that you're not going
to recover on the TC.

However, let's say having both the TC and the second (electric) AI is
not practical (probably due to space considerations). Would I rather
have an electric AI, or the TC? I would still prefer the electric AI.
First off, with dual AI's next to each other, I believe that following
a dying AI into an unusual attitude becomes far less likely, and thus
while the chances of recovery from the unusual attitude are reduced
slightly, the chances of encountering it in the first place are reduced
dramatically. Not so with a backup vacuum - you have to engage it.
And even if you do, half the time (in my experience more) the problem
is the AI, not the power source, so backup power for the AI does you no
good.

The problem with this analysis is the reliability (or lack of same) for
electric AI's. I've heard the affordable ones are not good, and the
good ones are not affordable.

Finally, there is the issue of training. If you have dual AI's with
independent power sources, it makes sense to skip partial panel
training. If you have only a single AI, even with redundant power
sources, that's not the case. In that case, a standby vacuum system
seems to be an unjustified expense - the money spent on it is probably
better spent on recurrent training.

Michael

Peter R. wrote:
Michael wrote:


I see little chance of that happening with dual AI's, and even less
chance that the average pilot will recover from an aerobatic attitude
partial panel after screwing up enough to get into that mess.


Interesting that you pointed that out. I was thinking the same thing when
I posed the question but thought that two tumbling AIs would pretty much
guarantee that the pilot would not recover.


But hey - if you have the panel room, why not keep the electric TC too?


My Bonanza has the original TC along with a backup electric AI located to
the left of the TC. However, the electric AI keeps precessing and requires
a reset about four times per hour, which concerns me.


What brand ?

I have an electric DG and AI in my Extra 300, which can be installed in a
removable panel for cross country flying. Neither has tumbled with gentle
acro (rolls, loops, spins), although it's probably hard on the bearings.

I suspect it would take more than an unusual attitude to tumble the gyros.

Peter R. wrote:
Michael wrote:


I think that if you really feel the need for redundancy, the sensible
solution is replacing the T&B with an electric AI.


I see that Sporty's is encouraging this option, too, with their electric
AI.

However, doesn't the AI have the potential to tumble in an unusual
attitude? During my IFR training I recall learning that the turn
coordinator will not tumble in an unusual attitude scenario whereas the AI
may. Since recovery from an unusual attitude was taught to me by first
going to the TC, I would be hesitant to replace an instrument so reliable
during a UA.

What say you?


Vacuums tumble.

Saw it on Dave Letterman, "throwing household appliances off a building".

I think that if you really feel the need for redundancy, the sensible
solution is replacing the T&B with an electric AI.

I would not remove the T&B. If you add another AI, put it in a nearby
hole, but not the T&B. No other instrument provides turn rate information.

Jose
--
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