Good AI backup, wish me luck

In article ,
(Robert M. Gary) wrote:
Because, a real world situation is that the AI dies very, very slowly.
There isn't that immediate "hmm, somethings wrong" like with a dead
vac (alarms going off etc). The TC has enough bounce in it that there
is really no way to detect small differences like 5 degrees when you
are in real IMC. Once you start bouncing around in the clouds the TC
starts bouncing back and forth. It will keep you upright but is far
from close enough to determine 5 or perhaps even 10 degrees off. The
DG you may or may not notice. In anycase two AIs being off is a pretty
quick and certain thing to notice.

Couple that with the fact that you have to decide which is right, the
TC or the AI. If you have 3 its easier to pick on that might be bad.


Let's see, I have 4 instruments in a basic IFR panel that can indicate
the position of the wings. AI, DG, TC, and wet compass. If my AI
starts to roll over 5 or 10 degrees and I level it, that's not going to
put me in a death spiral, but I should notice heading changes regardless
of what the TC is doing. If the ride is so rough that you can't obtain
meaningful data from any of the other instruments, then you're not the
guy I'd send to buy my lottery ticket.

Bottom line is that a scan should include all instruments. The more
data you incorporate into your scan, the more data you'll have to work
with if something looks amiss. The TC isn't the only practical backup
for the AI and, in fact, provides no pitch information anyway; for that,
you'll have to include airspeed and altimeter.

If I had to pick between having the TC, DG, altimeter, and airspeed as
my AI backup, or picking a second AI, I'd take the data from 4
instruments rather than one.

Maybe it's just me. Wouldn't be the first time.



JKG

In article ,
(Teacherjh) wrote:
You don't know which to trust, and you are out of bullets. You have to figure
out which one is lying. Besides, you can bank while remaning straight, and
you can be level while turning.

With two AIs, you can go PP and use the TC and DG (and ball).


If I have two AIs and they begin to disagree, what then? How do I
determine which one to believe?

If I incorporate the AI, DG, TC, wet compass, altimeter, and airspeed
into my scan and one instrument begins to disagree with the others, I
know almost instantly which instrument to disregard. Not sure how a
second AI helps substantially more with that, since it seems that I have
quite a few instruments to reference without the second AI. The second
AI would probably help me fly the airplane after I identified a faulty
AI, but wouldn't contribute substantially more to recognition because
I'd still have to use the other instruments in the panel to identify
which of the two AIs is accurate.

And, I flew partial panel in actual IMC just fine with *NO* AI many
times during my instrument training. The AI was covered and I knew that
I "lost" it, but I certainly didn't need a second AI to fly partial
panel, even on approaches.

I don't mean to make things sound trivial, because they're not.
Recognition and recovery is definitely not trivial for something like an
AI (I've had an AI die on me). However, thinking that a second AI is
going to bail your butt out of the recognition game is dangerous, IMO.
It all comes down to practice and practice often, which I suspect that
many of us (myself included) don't do enough of.



JKG

Jonathan Goodish wrote in message ...
In article ,
(Robert M. Gary) wrote:

Let's see, I have 4 instruments in a basic IFR panel that can indicate
the position of the wings. AI, DG, TC, and wet compass. If my AI
starts to roll over 5 or 10 degrees and I level it, that's not going to
put me in a death spiral, but I should notice heading changes regardless
of what the TC is doing. If the ride is so rough that you can't obtain
meaningful data from any of the other instruments, then you're not the
guy I'd send to buy my lottery ticket.

Its very common for me to be in actual conditions that are bouncy
enough that the TC isn't going to do anything other than keep me
upright. I'd be banking back and forth like a mad man as it flopped
around. The compass is pretty useless, it just spins back and forth.
That's the problem with most IFR, its usually very, very bouncy.

If I had to pick between having the TC, DG, altimeter, and airspeed as
my AI backup, or picking a second AI, I'd take the data from 4
instruments rather than one.

But its not one, its two. If you look at the two AIs and they disagree
you will say to yourself "Hmmm, something is wrong". The ability to
say that is HUGE. A real AI failure is so mild that you probably would
never notice. If just using the TC, DG and compass worked, you
wouldn't hear about people dieing after partial panel situations. You
wouldn't see big warnings on vac pumps. The airlines decided to get
extra AIs and dump the TC a while ago.

Dave Butler wrote in message ...
Mark Astley wrote:
Robert,

There was a recent article in Aviation Consumer about this (not sure if you
subscribe):

http://www.aviationconsumer.com/arch...ty/5307-1.html

Among other things, they discuss: dual chamber vac with a backup gyro and
PDA-style all electronic backups. If memory serves, a dual chamber vac with
a backup gyro is not terribly expensive and probably wouldn't require fancy
paperwork. I think they quote a price in the ballpark of $2000 for that
solution. The PDA-style all electronic solution is a bit more pricey and
wouldn't be panel mount.

Aviation Consumer's original article on the subject, written by Coy Jacobs, was
pretty negative on the dual vacuum pump.

It seems that Coy likes the items that he sells in his shop and tends
to not like the items that are not sold in his shop. I've never been
very happy with his objectivity. The whole scandal with the CorrosionX
vs the competitor was a good reason for me to drop the subscriptions.
Clearly he was going after the company that didn't want to let him
resell their goo (in my opinion).

-Robert

Followup after talking to one of my partners: We're pretty sure it's an RC
Allen. It's been in a little longer than I thought, more like 12 years instead
of 10. It's been repaired twice in the 12 years. The first time was relatively
reasonable and cost a few hundred dollars. The second time was over a thousand
and was called an 'overhaul'. The overhaul was done by Kelly Instruments. My
partner's feeling is that the reliability and repair cost was no different from
any typical gyro. The net is that maybe it's not as bad as I thought.


The installation in my airplane is over on the copilot's side, so it's
way out of my scan and therefore pretty much worthless. I'd go partial
panel with the turn coordinator and mag compass before I'd try to use a
gauge so far out of my scan. If you install an electric, be sure to put
it where you can see it.

Dave, thanks for the feedback ! Sounds like RCA, Kelly Inst. is the
manufacturer of that brand.

I bit the bullet and got one, will put it just right of the center
stack for now, but I could also go into what is now the #2 CDI spot
and move that to the right. That would look a bit funny, but may make
for a much better cross-check. In any case, I'll definitely practice
with it before considering it a solid backup.

Martin

I'm surprised no one has mentioned wet vacuum pumps. I'm considering a
wet pump when the current dry pump gives up the ghost, as it sounds like
wet pumps are nearly bullet-proof. That said, I have been lucky in that I
still have not had a vacuum pump go out on me. I have had several gyros
fail though.



--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

If you already have a few oil leaks, then the wet pump won't annoy you.
Those oil/air separators in the discharge are not perfect.
---JRC---

"Ray Andraka" wrote in message =
...
I'm surprised no one has mentioned wet vacuum pumps. I'm considering =
a
wet pump when the current dry pump gives up the ghost, as it sounds =
like
wet pumps are nearly bullet-proof. That said, I have been lucky in =
that I
still have not had a vacuum pump go out on me. I have had several =
gyros
fail though.
=20

Ray Andraka opined

I'm surprised no one has mentioned wet vacuum pumps. I'm considering a
wet pump when the current dry pump gives up the ghost, as it sounds like
wet pumps are nearly bullet-proof. That said, I have been lucky in that I
still have not had a vacuum pump go out on me. I have had several gyros
fail though.

At one point I thought about replacing the dry pumps on a Twin Comanche with
wet ones. Seems that you need to go through a bunch of STC or 337 field
approval paper work to do the swap. So I dropped the idea.



-ash
Cthulhu for President!
Why vote for a lesser evil?

"Ash Wyllie" wrote in message =
...
Ray Andraka opined
=20
I'm surprised no one has mentioned wet vacuum pumps. I'm considering =
a
wet pump when the current dry pump gives up the ghost, as it sounds =
like
wet pumps are nearly bullet-proof. That said, I have been lucky in =
that I
still have not had a vacuum pump go out on me. I have had several =
gyros
fail though.
=20
At one point I thought about replacing the dry pumps on a Twin =
Comanche with
wet ones. Seems that you need to go through a bunch of STC or 337 =
field
approval paper work to do the swap. So I dropped the idea.
=20
=20
I don't know about Lycoming engines, but Continentals still have the oil =
galleries
under the mounting pads for the vacuum pumps.
I know because I recently had to replace a leaking seal on one of my dry =
pumps.
Probably a simple 337 would suffice for Continentals.
You'd just be changing back to the configuration they were originally =
designed for.
---JRC---

Mine (a '65 model) originally had a wet pump, and I believe it is what is listed
on the TC.


At one point I thought about replacing the dry pumps on a Twin Comanche with
wet ones. Seems that you need to go through a bunch of STC or 337 field
approval paper work to do the swap. So I dropped the idea.

-ash
Cthulhu for President!
Why vote for a lesser evil?

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759