Wacko AI

Not to be confused with Yakko or Dot...

Just had the DG replaced (went precessing 60 deg on a 90 deg turn)
yesterday. Ran the engine up and taxi'd to the ramp from the shop.
Things looked ok - no, wait! the AI is upside down. Now, I'm
used to seeing it canted to the right before everything is run up
to speed, but upside down? Waited a few minutes, nothing, but
nothing changed. Unfortunately, the shop was closed by now so I
left it on the ramp and took the bus home.

Much more mystifying...after ALL power was off, engine off, key
out, battery off, etc. the AI dial was spinning. Yes, that's right,
spinning like a top. Fast. And it didn't seem to slow down, either.
I didn't time it, but it just sat there spinning for at least
5 minutes.

This is really surprising for a number of reasons.
1) I had spent 2 hours flying before taking it to the shop with
no indications of any problems.
2) A new AI installed in 2003
3) #2 occurred because the old AI sloooowly died on an IFR lesson
back in 2003. It was very noticeable, too, but not like this!

I would not have expected the AI to just quit without any warning.

Any suggestions? I haven't heard from the shop this morning (they're
not open yet). I'm thinking something got jarred loose when the
new DG was installed.

In a previous article, (blanche cohen) said:
Any suggestions? I haven't heard from the shop this morning (they're
not open yet). I'm thinking something got jarred loose when the
new DG was installed.

My guess would be that while they were working on the DG, something got
into the vacuum system and ended up in the AI gyro.


--
Paul Tomblin http://blog.xcski.com/
"The means of defense against foreign danger historically have become the
instruments of tyranny at home." - James Madison

"Paul Tomblin" wrote:

In a previous article, (blanche cohen) said:
Any suggestions? I haven't heard from the shop this morning (they're
not open yet). I'm thinking something got jarred loose when the
new DG was installed.

My guess would be that while they were working on the DG, something got
into the vacuum system and ended up in the AI gyro.

Or the pump is shedding carbon and fouling the system?

Any suggestions? I haven't heard from the shop this morning (they're
not open yet). I'm thinking something got jarred loose when the
new DG was installed.

It's funny -- I read the title of this thread a "WACKY AL" -- and
expected to read about Al Gore's latest lunacy.

Danged disappointing...

;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

You said it before I did, but I was thinking the same thing.
Oscar Awards... most recent indication that you're nuts.
Jim

My first questions to the shop would be "Did you disconnect the vac from the
AI in any way when you changed the DG?" and "Did you blow out the
(hopefully new) DG hose before you re-connected it?

As the AI is above the DG, the AI hose and even the AI itself may have been
in their way if they accessed it from the top. It could be as simple as
they cracked a T fitting or a hard hose.

Something is preventing the AI from erecting, could it be low vac suction?
What does your suction gauge read? Could be weak springs in the AI simply
waiting for a day to show you they are tired.

Good luck
Jim

Jim B wrote:
My first questions to the shop would be "Did you disconnect the vac from the
AI in any way when you changed the DG?" and "Did you blow out the
(hopefully new) DG hose before you re-connected it?

That's why it's back at the shop. I'm thinking that something got
into the AI connections.

As the AI is above the DG, the AI hose and even the AI itself may have been
in their way if they accessed it from the top. It could be as simple as
they cracked a T fitting or a hard hose.

Please, let this be the simple problem with a simple solution.

Something is preventing the AI from erecting, could it be low vac suction?
What does your suction gauge read? Could be weak springs in the AI simply
waiting for a day to show you they are tired.

Both the DG and the suction were showing good numbers/reactions. The
AI was installed in 2003 and was brand new. I'm hoping that it would
last more than 5 years.

But it's snowing here, so there's no rush.

If your DG was not new, I would suggest swapping the vac hoses on the AI and
DG. This may lead you towards a cracked line or fitting. I'm not an A&P or
any kind of Instrument Tech, but I can't imagine that applying low vac to a
new instrument would do it any favors. Just an idea.

Not snowing here (yet) but we've got a Winter Storm Warning from now until
Friday night. Now calling for 9-12" on top of the 18" we got last weekend.

Jim

I think if Jay had a house on the beach in Banda Aceh a couple of Christmas
seasons ago and someone told him a big wave was coming, he'd laugh and call
them crazy.

--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel

I'm a uniter, not a divider. - GWB, 1999.

"Jay Honeck" wrote in message
oups.com...
Any suggestions? I haven't heard from the shop this morning (they're
not open yet). I'm thinking something got jarred loose when the
new DG was installed.

It's funny -- I read the title of this thread a "WACKY AL" -- and
expected to read about Al Gore's latest lunacy.

Danged disappointing...

;-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Dan Luke" wrote

Or the pump is shedding carbon and fouling the system?

Only if it is a pressure system, instead of a true vacuum system.

Instruments run off of vacuum so that any carbon or other debris from a
failed pump goes into the pump and out the exhaust, instead of into the
instruments or plumbing.

But you knew that and had a brain fart, right? g