What is meant by “yellow tag”, “8130 form”, etc.?
Bob S is the true expert on this, but I’ll give you my “take” on the subject.
The “tag” system goes back so far that I don’t even know its origins. There are at least three colors; White (new or factory zero-timed); Yellow (serviceable), and Red (non-airworthy). I vaguely recall that a green tag may have indicated a rebuilt part (not rebuilt by the OEM), but I haven’t seen one in years. It is possible that these tags originated in a time when parts regulations were less stringent, and at that time perhaps they actually had more “influence”. Right now I think that the only purpose they serve is to identify parts status while in storage. The tags have no authority to confer airworthiness, without supporting documentation (8130, order papers, repair work order, etc.).
“Serviceability” has to be determined for any part that goes on a certified plane, whether new, overhauled-repaired, or used from salvage. In the case of a new or overhauled part, the part must be accompanied by supporting paperwork. New parts should always come with an 8130. Both may have an 8130, but any overhauled-repaired part is also supposed to have a workorder copy that shows what was done to it, to restore it to serviceable status. Let’s take a repaired cylinder assembly as an example. It is sitting on a counter at Sun-N-Fun with a yellow tag on it that is labeled “Serviceable”, and the sale flyer says “rebuilt, $500”. Sounds like a real “buy”, but as it sits, it is illegal for a certified installation. Let’s take the same cylinder with the same tag. This time the tag has a number of boxes checked that indicate replaced parts, and there is a workorder that lists all the actions taken and the parts that were installed, by part number. The workorder may describe plating or honing, welding repair, new or reused piston, type and part number of the rings, work done on (or replacement of) valves, seats, and guides, etc. Now the cylinder becomes “certifiable”, subject to a determination of applicability and apparent serviceability by the installing mechanic. Now let’s take the same cylinder with the very basic “serviceable” tag and no paperwork, but the A&P has a cylinder shop. He disassembles, cleans, and inspects the cylinder. He measures everything and restores all parts to serviceable limits, and writes up the applicable paperwork. He has now created a legal “repaired part” from a core unit. Without a cylinder shop, the mechanic can still take measurements and do some leak testing, and then make the determination that the cylinder is serviceable as-is, and can install it. He is really on the hook then, for any subsequent short-term cylinder failure.
The final authority for part serviceability is the mechanic who is installing it. No paperwork will absolve the mechanic of responsibility for installing the wrong part, or one that is clearly not serviceable. This doesn’t mean that he has to take a newly overhauled engine (with complete paperwork) apart to examine it (for example), but it does mean he is not free to just install a used engine without a careful examination and testing. He can’t just install a used brake cylinder without putting new rubber parts in it, unless he knows that they are still good (as another example). There is a lot of judgment involved, but the A&P will be on the hook for any bad outcomes. Having only a yellow tag for a used brake cylinder won’t clear the mechanic, if the cylinder fails and the plane winds up off the side of the runway in the weeds. He’ll be “safer” if he has a yellow tag along with a work order from the part supplier, that says new o-rings were installed and the cylinder was tested prior to shipment.
The 8130 is a form that is normally supplied by a new parts supplier. It certifies both airworthiness and traceable origin; it does NOT certify part applicability. The mechanic remains responsible for applicability. I have also been told that a copy of the order papers from a “certified source” such as RAPID can be substituted for the 8130, but I have not officially confirmed that. The traceability has become a major issue with heavy aircraft and helicopter operators, due to things like bogus rotor blades; many of the counterfeit parts have deadly possibilities (unfortunately this has been demonstrated in service). Our GA planes are less likely targets, as the money just isn’t there to make it worthwhile. However, we are not immune. A lot of bogus Lycoming rod bolts made it into the parts pipeline, through no other than Lycoming itself. They had been packaged in genuine Lyc boxes, and were re-imported and resold by Lycoming. That caused a few teardowns, following some in-flight bolt failures. Fact is, even small standard aircraft hardware is supposed to be fully traceable. That is virtually unenforceable right now; can you imagine the thousands of FBOs that have had bench stock for thirty or forty years, trying to come up with source documentation on every nut, bolt, screw, and washer? Thus far the main risk, therefore attention and enforcement, has been in the air carrier business.