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?

"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

OK, we now know the problem was a pinched hose, but there is some
speculation that a failed vacuum pump can actually blow dust backwards into
the vacuum instruments. The idea is that residual vacuum at the instruments
allows the higher pressure at the failed pump to push the dust into the
vacuum instruments. There is an STCd filter that can be placed between the
instruments and the pump designed to prevent dust backflow if the pump
fails.

--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel

Time flies like an arrow, fruit flies like a banana.

"Morgans" wrote in message
...

"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

"Mike Noel" wrote in message
. ..
OK, we now know the problem was a pinched hose, but there is some
speculation that a failed vacuum pump can actually blow dust backwards
into the vacuum instruments. The idea is that residual vacuum at the
instruments allows the higher pressure at the failed pump to push the dust
into the vacuum instruments. There is an STCd filter that can be placed
between the instruments and the pump designed to prevent dust backflow if
the pump fails.

I thought vacuum systems had a check valve that prevented backwards moving
air. No?

If not, it sounds like they should.
--
Jim in NC

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"

On 28 Feb 2007 10:05:58 -0800, "Jay Honeck" wrote
in .com:

It's funny -- I read the title of this thread a "WACKY AL" -

And here I thought he was referring to an Inspector of Aircraft.

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

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

http://www.nydailynews.com/front/sto...p-422609c.html

//

The bad news is you can lose the presidency of the united States even when
you win the popular vote. But the good news is you can get an Oscar with
fewer people than fit on a subway train.

"There are three categories in the Oscar voting that require a special
ballot," says an insider. "To vote for foreign, short film or documentary,
you have to sign an affidavit that you have seen all the nominees." it's not
enough to watch them at home on a DVD - Academy members have to attend an
official screening.

The snitch said fewer than 300 people requested the special ballot in the
documentary category, which was won by Al Gore's "An inconvenient Truth"
Sunday. But even that number is about 100 more than usual.

An Academy rep confirms that of its 5,800 voting members, only about 200
typically file a ballot in the category.

//