"Yellow tag" and my A&P's inspection

Couple of months's ago I bought a used strut from an indivudual.
My A&P sandblasted it, inspected it, declared it OK.

That's the same process the strut would have gone thru if I had
purchased it with a "yellow tag", correct? - Mike

"Glenn Jones" wrote in message ...
In article ,
Michael Horowitz wrote:

Couple of months's ago I bought a used strut from an indivudual.
My A&P sandblasted it, inspected it, declared it OK.

That's the same process the strut would have gone thru if I had
purchased it with a "yellow tag", correct? - Mike

Not necessarily. A yellow tag is just a piece of paper. Any part that is
unknown should be inspected. Any shop work from an outside vendor should
be thoroughly inspected. Yes, I know they're SUPPOSED to do that, but
I've found reality can often depart from the ideal.

Case in point:

I've gotten cylinders back from machine shops with yellow tags on them,
and cracked exhaust guide bosses. Totally unairworthy, but the shop saw
fit to tag it. On other cylinders, the seat-guide alignment was so bad
that only 1/3 of the valve face hit the seat before sliding sideways and
seating up. I don't know if this is an unairworthy condition according
to the feds, but it is to me.

So unless you're experienced enough to inspect another's work, don't put
a lot of faith in that little yellow tag. It often serves simply to tell
the vendor, "Sell this piece of ****."

What exactly is the 'Yellow Tag'? Does it have a specific format (ala 8130-3)? Who can put them on the part?

The local FBO just had two exhaust valves go bad on his C180.... Pulled
the cylinders and sent them out to a cylinder shop for overhaul... They
came back yellow tagged... He re-installed the cylinders back on the
same piston they came off from, and on one could not get the exhaust
pipe to line up... What the hey? Gets out a strong light (why do all
mechanics work in a shop that is dimmer than a confessional booth?) and
takes a look... The head was re-installed on the barrel ten degrees out
of alignment...

I just went through a big thrash on a carburetor that was supposedly
zero timed from the re-manufacturer... It was defective out of the
box, TWO times in a row...

So yellow isn't necessarily the answer...

denny

Glenn Jones wrote:
In the real world, EVERYTHING coming back from a third-party shop
needs
inspection.

No, the real world abandoned that kind of thinking decades ago. The
real world long ago switched over to quality systems and production
processes that don't require 100% (or even 10%) inspection.

Only in backwater industries mired in a regulatory morass and hidebound
with obsolete technology is 100% inspection normal - or needed. In
other words - when you're dealing with certified aircraft parts and
repair stations, everything needs inspection and the paperwork that
comes with the part that assures its airworthiness (yellow tag) is just
so much useless paper.

I personally inspect and, as much as possible, test every part I
install on an aircraft. But I also design instrumentation for a major
manufacturer, and thus deal with manufacturing, inspection, and repair
procedures in the real world - where a mistake can mean a major
industrial accident. I must say that if we did things the way
certified FAA manufacturers and repair stations do, we would be out of
business within three years.

Michael

On Mon, 21 Mar 2005 07:23:58 -0800, Glenn Jones
wrote:

In article .com,
"Denny" wrote:

The local FBO just had two exhaust valves go bad on his C180.... Pulled
the cylinders and sent them out to a cylinder shop for overhaul... They
came back yellow tagged... He re-installed the cylinders back on the
same piston they came off from, and on one could not get the exhaust
pipe to line up... What the hey? Gets out a strong light (why do all
mechanics work in a shop that is dimmer than a confessional booth?) and
takes a look... The head was re-installed on the barrel ten degrees out
of alignment...

I just went through a big thrash on a carburetor that was supposedly
zero timed from the re-manufacturer... It was defective out of the
box, TWO times in a row...

Well, especially in the case of the cylinders, visual inspection prior
to installation would have revealed the flaw. The fact your A&P just

Visual would have revealed 10 degrees? Your eyes are better than
mine. On something that large I'd not see the 10 degrees until I had
something with which to reference it too.

Now OTOH I'm not a mechanic and maybe there are alignment marks that
would have made it stand out like a sore thumb, but having alignment
marks would be too simple and make too much sense.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

pulled them out of the box and slapped them on the engine is alarming to
me.

In an ideal world, something coming back from a shop with a yellow tag
would not need inspection prior to installation.

In the real world, EVERYTHING coming back from a third-party shop needs
inspection.

The yellow tag only means it's yellow, a repair station could use yellow for
rejected parts. the important part is the"overhauled per this or that
manual" even then unless you are cognizant of ALL the manual requirements,
including reference documents, and followed your particular part through the
repair process making sure that actually happened, you probably didn't get
what you paid fo.
The FSDO folks that oversee these repair stations aren't familiar with all
of these requirements either and only look into things when there has been
an accident or complaint, otherwise it's business as usual.Most of the time
there won't be a problem, but who wants to volunteer to be there when it
happens?

"Denny" wrote in message
oups.com...
The local FBO just had two exhaust valves go bad on his C180.... Pulled
the cylinders and sent them out to a cylinder shop for overhaul... They
came back yellow tagged... He re-installed the cylinders back on the
same piston they came off from, and on one could not get the exhaust
pipe to line up... What the hey? Gets out a strong light (why do all
mechanics work in a shop that is dimmer than a confessional booth?) and
takes a look... The head was re-installed on the barrel ten degrees out
of alignment...

I just went through a big thrash on a carburetor that was supposedly
zero timed from the re-manufacturer... It was defective out of the
box, TWO times in a row...

So yellow isn't necessarily the answer...

denny

Denny wrote:
pipe to line up... What the hey? Gets out a strong light (why do all
mechanics work in a shop that is dimmer than a confessional booth?) and
takes a look... The head was re-installed on the barrel ten degrees out
of alignment...

Out of curiosity, how does the head go on ten degrees (approximately
or exactly) out of alignment? I thought the bolts or studs would
accurately locate the head and jug every time, so obviously there is
something I am missing or don't know.

Earlier, Jim Carriere wrote:

Out of curiosity, how does the head go on ten
degrees (approximately or exactly) out of
alignment? I thought the bolts or studs would
accurately locate the head and jug every time,
so obviously there is something I am missing
or don't know.

For the cylinder of the common Lycoming and Continental engines, the
cylinder head is a machined aluminum casting that is screwed onto
threads at the top end of the steel cylinder barrel. Separating and
reassembling the head/barrel pair is something that relatively few
shops do, and I've never personally seen it done. However, I have seen
procedures for doing it, and I think it takes special heating and
alignment equipment.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com

The Cylinder head is screwed on the cylinder like a big jar lid. I always
though that they used the old head with a new barrel, screwed it on tight,
then jig drilled the mounting holes is the flange of the barrel. I don't
know how one would index a new head with and old barrel. I suppose it could
be done with shim gaskets, but if you didn't get the right shim, the head
would not stop at the right place.


--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot
"Jim Carriere" wrote in message
...
Denny wrote:
pipe to line up... What the hey? Gets out a strong light (why do all
mechanics work in a shop that is dimmer than a confessional booth?) and
takes a look... The head was re-installed on the barrel ten degrees out
of alignment...

Out of curiosity, how does the head go on ten degrees (approximately or
exactly) out of alignment? I thought the bolts or studs would accurately
locate the head and jug every time, so obviously there is something I am
missing or don't know.

The head doesn't "stop" at the right place, nor is there a head gasket,
per se. The threads on the barrel ARE the actual seal, and the head is
screwed down a specific distance, plus or minus the amount of rotation
necessary to make the head to barrel flange angular alignment correct.

Cy Galley wrote:
The Cylinder head is screwed on the cylinder like a big jar lid. I always
though that they used the old head with a new barrel, screwed it on tight,
then jig drilled the mounting holes is the flange of the barrel. I don't
know how one would index a new head with and old barrel. I suppose it could
be done with shim gaskets, but if you didn't get the right shim, the head
would not stop at the right place.