Parts Primer

How to tell a good part from a bad one.

Here are a few things that you must pay attention to when you install a TSO part. First, the vast majority of TSO parts are used for alterations, not remove and replace items. Second, use of a TSO part may require a logbook entry and a Form 337. So the first thing you need to determine is, if the installation of the TSO part or parts constitutes a major alteration. For example, what about a complete TSO radio package with coupled autopilot installed in a King Air B-200? Is it major or minor? In this case it is a major alteration. But slipping a couple of TSO life vests in a seat pocket of a Piper Arrow before a trip to the Bahamas is not because nothing has been altered.

Type or production parts

This is easy to explain. You open up the aircraft's parts manual and order the part you need. The part comes directly from the manufacturer or another manufacturer who has been authorized by the TC or Production Approval Holder for direct ship authority. The part is usually identified by manufacturer part number, or tagged, or has an 8130-3 tag.

A small problem might come into focus when you order a part using a part number out of the manufacturer's parts manual. When the part arrives, it looks, feels, and even smells the same as the one you are replacing, but it has a different part number on the invoice. You call up the manufacturer and you get the story that the part number has been superceded but the part manual has not been revised and go ahead and install the part.

This is not a good idea! Try explaining to the NTSB or FAA if the aircraft goes in and the part you installed last Tuesday is high on their list of probable causes and the part's guy is suffering from memory failure.

Be smart! Get the revised part number change in writing from the manufacturer! An e-mail or a fax from the manufacturer explaining the part number revision is fine. Be sure that the e-mail or fax includes the person's name, position in the company, and phone number. At least you will have something in your pocket if the aircraft has a problem instead of being the only one holding the wet paper bag of responsibility.

Owner produced parts

Despite the title, "owner produced parts" the owner does not have to make the part himself. However to be considered a producer of the part the owner must have participated in controlling the design, manufacture, or quality of the part such as:

  1. provide the manufacturer with the design or performance data from which to make the part, or
  2. provide the manufacturer with the materials to make the part or,
  3. provide the manufacturer with fabrication processes or assembly methods to make the part or,
  4. provide the quality control procedures to make the part or,
  5. personally supervise the manufacturer of the part.

One of the most important things to remember about owner produced parts is an owner or his agent can not automatically make a part by reverse engineering it. You need an approved data trail. Either make the part using original design drawings, have a DER make some new drawings, or make your own drawings of the part and have the data field approved by the local FSDO.

Most pilots and owners are blessed with so much mechanical hands-on talent that you would have to times it by 100 to fill up a Corvette's trunk. Realizing this, the FAA allows the owner to contract out for the manufacture of the part to his mechanic or anyone else and still have a part that is considered "owner produced" as long as the owner participated in one of the five functions listed above.

The question always comes up if a mechanic manufactured parts for an owner is he considered in violation of section 21.303(b) (2)? The answer would be no if it was found that the owner participated in controlling the design, manufacture, or quality of the part. The mechanic would be considered the agent for the producer and would not be in violation of section 21.303(a).

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