Aero Advantage closing shop.

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

"Nathan Young" wrote in message
...

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.

Very few piston general aviation airplanes have dual alternators and you
could not even begin to consider a non-vacuum-system airplane without both
dual alternators and dual electrical buses. Even dual electrical buses can
fail and that is why business jets often have an emergency battery-powered
gyro which completely self-contained; these backup gyros can easily cost
over $7,000.

At those prices, it seems a lot more practical or at least economical in a
GA airplane to simply have a conventional vacuum AI backed up by a
conventional electric AI.

--------------------
Richard Kaplan, CFII

www.flyimc.com

Why spin a gyro at all? Laser ring gyros are the way to go. No moving
parts.

Sandy Mustard

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.

--- Jay

David Megginson wrote
Afterwards, I read the Air Safety Foundation report that everyone cites on
the danger of vacuum pump failures: it turns out that they did not find a
*single* fatal accident from 1983 to 1997 involving a vacuum-pump failure
for a fixed-gear plane flying IFR -- losing control partial panel seems to
be a retractable thing.

As a gross generalization, that makes sense to me.

IMO the really critical parameters are drag coefficient and roll
stability. Airplanes which are roll stable and draggy (Cherokees,
C-172's, and their ilk) are easy to fly partial panel and it takes a
long time for a nose low unusual attitude to develop to the point
where the airplane will redline. Airplanes that are clean and not
terribly roll stable (Bonanzas, Mooneys) are much more demanding
partial panel, and will go to redline in a heartbeat once you let a
nose-low unusual attitude develop. I suspect, though, that the new
crop of high-speed low-drag fixed gear singles from Lancair and Cirrus
are likely to behave more like the Mooneys and Bonanzas, whereas
retracts like the Arrow and Cutlass are probably not significantly
more likely to have loss of control problems when partial panel than
their fixed gear cousins.

Personally, I consider backup vacuum/gyros to be a low priority for
something like a Cherokee. I suspect that the same money spent on
regular recurrent training would have a significantly higher payoff in
safety. I would put the backup vacuum/gyro for something like a
Cherokee lower on the list than some sort of weather avoidance
capability (spherics, datalink, etc.) and lower than a good handheld
GPS with fresh batteries. Once you have those things, and you're
doing regular recurrent training, then sure - get athe backup. I'm
sure it must have some marginal safety advantage.

Michael

Richard Kaplan wrote:

Very few piston general aviation airplanes have dual alternators and you
could not even begin to consider a non-vacuum-system airplane without both
dual alternators and dual electrical buses. Even dual electrical buses can
fail and that is why business jets often have an emergency battery-powered
gyro which completely self-contained; these backup gyros can easily cost
over $7,000.

It can be a fraction of that if you don't mind yet another portable device
cluttering your cockpit:

http://www.icarusinstruments.com/microEFIS.html

People have also reported some success under the hood flying a plane using
the display on the Garmin 196. Of course, until people are forced to used
it in actual IMC, we won't know how well it really works in an emergency.

At those prices, it seems a lot more practical or at least economical in a
GA airplane to simply have a conventional vacuum AI backed up by a
conventional electric AI.

That's just it -- even my cheap little Warrior has a lot of options for
keeping the wings level in IMC:

Vacuum-powered AI and HI
Electic-powered TC
Battery-powered GPS
Magnetic compass

Of course, these become less and less useful as you go down the list (I
wouldn't be much on my chances with just the magnetic compass), but in real
life, but how much redundancy do you need before you've overdesigned the
system? As I mentioned earlier, I have not yet managed to find a single
example of a fatal accident caused by a vacuum-pump failure in a fixed-gear
plane flying IFR. There must be one or two, but it does not appear to be a
significant risk.


All the best,


David

Michael wrote:

Personally, I consider backup vacuum/gyros to be a low priority for
something like a Cherokee. I suspect that the same money spent on
regular recurrent training would have a significantly higher payoff in
safety. I would put the backup vacuum/gyro for something like a
Cherokee lower on the list than some sort of weather avoidance
capability (spherics, datalink, etc.) and lower than a good handheld
GPS with fresh batteries.

Funny, you just listed my major purchases over the past six months: I bought
a Garmin 196 in December, and just ferried my plane back from Montreal this
afternoon with a (used but factory updated) WX-900 Stormscope installed by
an experienced shop. It was the perfect afternoon for it: solid IMC above
1,200 ft AGL, with a small risk of occasional embedded TCU and CB (normally,
I cancelled flights under those conditions).


All the best,


David

On Mon, 10 May 2004 16:15:48 GMT, "Richard Kaplan"
wrote:

snip

Very few piston general aviation airplanes have dual alternators and you
could not even begin to consider a non-vacuum-system airplane without both
dual alternators and dual electrical buses. Even dual electrical buses can
fail and that is why business jets often have an emergency battery-powered
gyro which completely self-contained; these backup gyros can easily cost
over $7,000.

At those prices, it seems a lot more practical or at least economical in a
GA airplane to simply have a conventional vacuum AI backed up by a
conventional electric AI.

I would be interested in the maintenance requirements for a couple of
the new "electric" aircraft. Another thread was asking about the
batteries keeping the engine turning on the Liberty XL2. My totally
uninformed guess is that on the Liberty, when the batteries quit, the
engine does as well. This was indeed the case with the certified
Porsche-powered Mooney.

Having maintained a few turbine aircraft & "business jets", periodic
maintenance and inspection/cap check of the various batteries and
specific DC generator life limits (one specific example has three
primary DC buses, six batteries, and three generators installed) are
an important factor in maintaining the "normal" and "emergency"
systems.

I would like to think that this same matter (periodic cap check and
alternator life limts) is specifically addressed in the new GA
designs.

BTW, I've also thought that it curious that cap checks on the main
ship's battery (which is the sole source of emergency electricity) on
"classic" GA designs seems to be a non-issue.

Regards;

TC

Airplanes that are clean

Aye

and not
terribly roll stable (Bonanzas, Mooneys)
are much more demanding
partial panel,

My 65 C Mooney is incredibly roll stable and extremely easy to fly
partial panel; so much so that some view it as a weakness (I dunno,
maybe in a flat scissors?). I fly partial panel approaches IMC for
practice. Later M20's are more pitch stable as well.

Jay Honeck wrote:

It's amazing when spending something approaching $1500 for two lousy vacuum
instruments makes me a "cheapskate"...

If you manufactured a clock to that level of precision, it would cost more than one
of those items. And wouldn't have to be certified. Don't believe me, check out the
prices on Swiss watches these days.

I repeat. Quitcherbitchin.

George Patterson
If you don't tell lies, you never have to remember what you said.

"David Megginson" wrote in message
e.rogers.com...


It can be a fraction of that if you don't mind yet another portable device
cluttering your cockpit:

If we are talking about why airplanes have vacuum systems then we need to
keep the discussion to certified equipment -- other options may work but if
they are not certified then the FAA will require a vacuum system for legal
IFR.

system? As I mentioned earlier, I have not yet managed to find a single
example of a fatal accident caused by a vacuum-pump failure in a
fixed-gear
plane flying IFR. There must be one or two, but it does not appear to be
a
significant risk.

I think part of this may be related to how the accidents are classified.

For example, there are a number of examples each year of IFR airplanes which
simply suffer inflight break-up for unknown reasons; these could well be due
to vacuum pump failure.

--------------------
Richard Kaplan, CFII

www.flyimc.com