Parts Primer

How to tell a good part from a bad one.


On the other hand if the owner did not play a part in controlling the design, manufacture, or quality of the part the mechanic runs a good chance of being in violation of section 21.303 (b)(2). To stay out of harms way the mechanic should never make a logbook entry saying that he "made" a part under his certificate number. However, the mechanic can say on the work order that he helped manufacture an "owner produced part" under 21.303 (b) (2). To avoid from making friends with the local FSDO, the owner or operator should be encouraged to make a logbook entry that is similar to section 43.9 maintenance entry that states that: The part is identified as an owner produced part under section 21.303 (b)(2). The part was manufactured in accordance with approved data. The owner/operator's participation in the manufacture of the part is identified such as quality control or supervision. The owner should declare that the part is airworthy and sign and date the entry.

As the mechanic who is going to install this owner produced part you must ensure that it meets form, fit, and function and ensure that it meets its approved type design. Then install the part on the aircraft and make an operational check if applicable and make the required section 43.9 entry.

OK, where does the responsibility lie for this owner produced part? The short and sweet answer is the owner is responsible for the part meeting type design and is in a condition for safe operation. The mechanic is responsible for the installation, that it's airworthy, and a record of installation is made. Once the part is on the aircraft it is treated just like any other aircraft part.

Standard parts

Think nuts, bolts, safety wire, etc. that conform to an industry specification. If you want the real definition according to AC 20-62D a standard part is a part manufactured in complete compliance with an established U.S. government or industry-accepted specification which includes design, manufacturing, and uniform identification requirements. The specification must include all information necessary to produce and conform the part. The specification must be published so that any party may manufacture the part. Examples include, but are not limited to, National Aerospace Standards (NAS), Air Force-Navy Aeronautical Standard (AN), Society of Automotive Engineers (SAE), SAE Aerospace Standard (AS), Military Standard (MS), etc.

On June 5, 1997, the FAA Aircraft Engineering Division published in Volume 62 of the Federal Register an expanded interpretation for standard parts. FAA determined that certain kinds of electrical and electronic parts built to an industry standard fit within the limits of Section 21.303(b)(4) such as resistors, capacitors, diodes, transistors, and nonprogrammable integrated circuits such as amplifiers, bridges, switches, and gates. The Notice of Interpretation is five pages long and if you are interested please go to the Federal Register web site and check out Volume 62, June 5, 1997, titled Notice of interpretation.

Surplus parts

A surplus part is a product, assembly, part, or material that has been released as surplus by the military, manufacturer, owner/operator, repair facility, or any other part supplier. These products should show traceability to an FAA approved manufacturing procedure. The biggest problem with surplus parts is that in many cases the internal condition of the part is unknown. Surplus composite fabric, sealant, paints, glues, and parts with internal O-rings, seals, and gaskets are usually put on the surplus market by the ton, just so the military overhaul facility can pass an IG inspection without being gigged for overdue shelf life items. Since the first Gulf War the military has tightened up its inventory control, so real "bargains" are hard to find and if you do, they are even harder to document . . .

Overhauled parts

According to section 43.2 an overhauled part has been disassembled, cleaned, inspected, repaired, tested, and reassembled to meet the manufacturer's service limits. Well this is a fine definition but every manufacturer's service limits define a finite area that sits between brand new and worn out. It is quite possible a part could be legally signed off as "overhauled" even if it is just .001 inch inside the maximum limit. So it would stand to reason that overhauled parts will not match new or rebuilt TBO times. This is something to think about when you order your next "overhauled" part.

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