Wacko AI

[blanche cohen]

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.

[Paul Tomblin]

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

[Dan Luke]

"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?

[Jay Honeck]

> 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"

[Jim B]

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]

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

[Blanche]

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.

[Jim B]

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

[Mike Noel]

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"
>

[Morgans[_2_]]

"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>

[Matt Barrow[_3_]]

"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/story/501135p-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.

//

[Matt Barrow[_3_]]

"Mike Noel" > wrote in message
. ..
>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.
>
If they said it was coming because of GW, he'd been justified

>
> http://photoshow.comcast.net/mikenoel
>
> I'm a uniter, not a divider. - GWB, 1999.

GWB got high marks from members of the Texas legislature, both D's and R's
and especially minorities, for his ability to bring people together.

Of course, Texas does not have the coastal and MSM crazies.

[Steve Foley]

"Matt Barrow" > wrote in message
...

> The bad news is you can lose the presidency of the united States even when
> you win the popular vote.

In exactly the same way that your team can score the most runs in the World
Series, but still lose.

[Montblack]

("Steve Foley" wrote)
>> The bad news is you can lose the presidency of the united States even
>> when you win the popular vote.

> In exactly the same way that your team can score the most runs in the
> World Series, but still lose.


In Game 7, Gore got thrown out trying to steal Florida. :-)


Montblack-socks

[Steve Foley]

"Montblack" > wrote in message
>> In exactly the same way that your team can score the most runs in the
>> World Series, but still lose.
>
>
> In Game 7, Gore got thrown out trying to steal Florida. :-)
>
>

Was Chad Billingsley pitching?

[DR]

blanche cohen wrote:
> 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.
>

Perhaps I may be off on this, but if it seemed stable upside down, is it
possible that it was accurately upside down so that the erecting
mechanism was not able to get it the right way up? I wonder if you had
resored vacuum after it started tumbling whether that would have enabled
it to precess to upright (which may take several minutes)?

Cheers Mark

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[Matt Barrow[_3_]]

"Steve Foley" > wrote in message
news:wiDFh.32266$kr6.7274@trndny09...
> "Matt Barrow" > wrote in message
> ...
>
>> The bad news is you can lose the presidency of the united States even
>> when you win the popular vote.
>
> In exactly the same way that your team can score the most runs in the
> World Series, but still lose.
>

Not my post, but I agree with yours.

[Blanche]

In article >, DR > wrote:
>blanche cohen wrote:
>> 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.
>
>Perhaps I may be off on this, but if it seemed stable upside down, is it
>possible that it was accurately upside down so that the erecting
>mechanism was not able to get it the right way up? I wonder if you had
>resored vacuum after it started tumbling whether that would have enabled
>it to precess to upright (which may take several minutes)?
>
>Cheers Mark

Mark, et al.

Turns out (politics aside) that all of you were close. When the
next (#3) DG was installed, one of the hoses/tubes got pinched,
effectively hosing the AI. The unit itself is fine, and the repairs
have been completed and tested. Unfortunately, I won't be able
to check anything until Saturday due to anticipated horrendous
winds in Colorado.

Thanks all for the suggestions.

[Mike Noel]

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>
>

[Morgans[_2_]]

"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

[Ron]

My XP Hawk didn't have a filter upstream of the pump until I had to overhaul
the AH and DG, with carbon found in each instrument. I had a vac 'pump'
failure some time previously. Hopefully the filter doers the trick during my
next vac failure.

--

regards
Ron



"Morgans" > wrote in message
...
>
> "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
>