"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

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

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.

You screw the head onto the cylinder, and if it is off alignment at "tight",
there is an allowable amount of "back me off" angular adjustment that is
allowable to make the intake/exhaust ports line up.

In the field, big and long wooden dowels stuffed into the intake/exhaust
ports and smartly pushed and pulled around to make the sucker line up are
not exactly in accordance with the service manual, but is how it is done.

Of course, such an unapproved procedure would NEVER be used by a reputable
mechanic, but ....


Jim




"Cy Galley" wrote in message
news:bBK%d.93211$Ze3.82701@attbi_s51...
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.

Jim, That unit was mailed your way (at Downwind Court Address)
last Monday from Florida.

The secretary in our office was/is new. She only charged me
One dollar and ten cents postage, it may arrive with postage
due as that seems too little.

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage http://bfn.org/~ca266