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Be a “Part” of Improving Aviation Safety - A Look at Suspected Unapproved Parts

By James P. Niehoff
Source: FAA Safety Briefing May/June 2019


unapproved parts

The reality of unscrupulous people trying to dupe unsuspecting mechanics, owners, and/or operators into buying unapproved aircraft parts is very real, and the GA community needs to remain staunchly aware of these practices. Adding to this concern is the confusion when it comes to understanding the differences that exist among aeronautical parts. Despite a repeated history of lessons learned, the FAA continues to confront this issue and remains committed to advocating the importance of using approved parts.

Part and Parcel

To better understand the issue, let’s start by explaining how aircraft parts are classified. There are three main categories: approved parts, unapproved parts, and suspected unapproved parts.

Approved parts: A part can be called “approved” if it has been produced in accordance with one of the following: type certificate (TC), supplemental type certificate (STC), parts manufacturing approval (PMA), technical standard order (TSO), owner produced parts, standard parts, or other process approved by the Administrator.

Unapproved parts: These are parts that we know were not produced in accordance with any of the approved methods previously listed. These would include automotive parts, hardware store bolts, etc.

Suspected Unapproved Parts (SUPs): These parts resemble approved aircraft parts, but they were not produced in accordance with an approved method. This can also include parts that may have been approved but can no longer be traced to that approved method.

For some additional context into the issues with SUPs, let’s expand on the acceptable methods used to deem a part “approved.”

Seal of Approval

Type Certificate (TC): An aircraft manufacturer receives a TC from the FAA when it demonstrates that its newly designed aircraft meets all of the current aircraft certification rules. The FAA will issue a production certificate (PC) to a manufacturer when its established production demonstrates that each aircraft produced conforms to its TC, or type design. All parts and pieces associated with that aircraft are “FAA Approved.” Certification of aircraft by the FAA ensures that commercial and general aviation aircraft meet the highest safety standards, from initial design to retirement.

Supplemental Type Certificate (STC): An STC is a TC issued when an applicant has received FAA approval to modify an aeronautical product from its original design. The STC, which incorporates the related TC by reference, approves not only the modification, but also how that modification affects the original design. In other words, to modify an aircraft from its original type design, you will need an STC. Think floats, wing extensions, short takeoff and landing (STOL) kits, engine conversions, etc.

Parts Manufacturer Approval (PMA): A PMA is a combined design and production approval for modification and replacement articles. It allows a manufacturer to produce and sell these articles for installation on type certificated products. FAA Orders 8110.42 and 8120.22 prescribe the approval procedures for FAA personnel and guides applicants in the approval process. An Approved Model Listing (AML), which should accompany a PMA, lists all of the aircraft on which that part is approved for use. The AML is your installation approval.

Technical Standard Order (TSO): A TSO is a minimum performance standard for specific materials, parts, and appliances used on civil aircraft. A TSO authorization is authorization to manufacture a material, part, or appliance to a TSO standard. Receiving a TSO authorization is both a design and production approval. However, receiving a TSO authorization is not an approval to install and use the article in the aircraft. Rather, it just means that the article meets the specific TSO, and it authorizes the applicant to manufacture it. There are many current published TSOs. Think seat belts, life vests, emergency locator transmitters, airspeed indicators, etc.

Owner-produced parts: This is a subject all on its own, so I won’t cover it in detail here. The FAA does make provisions in the regulations for aircraft owners to produce parts for installation on their own aircraft. However, you cannot produce in surplus and sell any parts made in this manner to other owners. This action would require a PMA or other FAA approval. See 14 CFR section 21.9(a) (5) & (6) and Advisory Circular (AC) 20-62E for additional information. There is also an article on owner-produced parts from the Jul/Aug 2002 issue of this magazine available here:

Standard Parts: When you hear this term, you might be inclined to think of something simple, like regular nuts and bolts. In fact, other types of parts, as well as materials used to produce aviation parts, may fall under the “standard part” category. A standard part is a part or material that conforms to an established industry or U.S. government-published specification. The FAA bases the acceptance of a standard part as an approved part on the certification standards used to design and produce that part (usually an independent established set of specifica-tions and criteria.) Think Air Force/Navy (AN), Military Standard (MS), National Aerospace Standard (NAS), Society of Automotive Engineers (SAE), etc., to include nuts, bolts, hoses, plumbing lines and fittings, sheet metal, rivets, etc.

Any other process approved by the Administrator: The bottom line here is that there should be a paper trail showing a connection to that FAA approval. Think field approval, etc.

Terms to Know

Now that you have a better idea of the different types of aeronautical parts and what makes them officially “approved,” let’s talk about how to identify and report a SUP. The differences can be subtle.

To help with the FAA’s ability to investigate as well as educate the aviation community on SUPs, the agency formed a SUP Program Office in 1995. The FAA’s Flight Standards Service (FS) assumed initial responsibility for the program, but in 2012 it was transferred to the Aircraft Certification Service (AIR). Today, the FAA’s Office of Audit and Evaluation processes all FAA Hotline complaints (more on that later) and forwards all SUP related reports to focal points in both AIR and FS for evaluation. These individuals then work together to properly classify the report and assign it for investigation, as determined by the details of the case.

From the perspective of the SUP office, there seems to be a lot of confusion regarding SUPs. That’s understandable, because it is a nuanced issue. It also uses terminology that overlaps into other aspects of the aviation industry, making it hard to differentiate among those terms.

Here are a few, real-world examples that illustrate some of this confusion:

Use of Known Unapproved Parts: We received a report that identified the use of grade 8 hardware store bolts in place of approved standard aircraft hardware. This error was obvious and easy to spot; the reporter spelled out the issue and included numerous photos to document the error. The intentional use of known unapproved parts in place of approved aircraft parts is a case of “improper maintenance” and is not a SUP case. Ultimately, we assigned this case to the local Flight Standards District Office (FSDO) for investigation.

Quality Escape: This term means that a production certificate holder makes an error and ships a part that does not conform to the type design. There may be a variety of reasons for this occurrence. For example, there may have been a missed step in the part’s manufacturing process, which was then missed by quality control. This is not a SUP case, but it gets immediate attention from the FAA’s Aircraft Certification personnel to identify and fix the problem.

Approved Parts Installed in Unapproved Places: This is another instance of “improper maintenance” rather than a SUP case. When you install an approved part in the wrong place, it does not lose its classification as an approved part if it has not lost traceability to its approved roots.

Counterfeit Parts: These are unapproved parts manufactured and sold without FAA approval. You should report them to the FAA as a SUP. There may be obvious, or not so obvious, visual clues to help you spot these parts. The FAA aggressively investigates these cases and works closely with the Office of Inspector General (OIG) and law enforcement officials to ensure proper adjudication. There are cases of this nature that have resulted in significant civil penalties and/or jail time for those involved.

Play Your Part

As an aircraft owner, operator, or mechanic, you play an important role in ensuring the integrity of aeronautical products, especially when it comes to determining the quality, eligibility, and traceability of aircraft parts. One tool you can use to report any instances of SUP is the FAA’s Hotline Program ( The hotline is a national reporting system established to receive reports of potential unapproved parts entering the aviation system primarily at the supply and repair level of aircraft maintenance. You can also report SUP via mail, and the SUP Report form is available Please note that you can no longer report a SUP by phone.

If the SUP office receives a hotline report that is ultimately classified as something other than a SUP, please don’t think it gets ignored or discarded. Instead, the SUP focal points evaluate each report, make the appropriate classification change, and recommend assignment to the appropriate FAA office. The FAA investigates all cases.

An excellent resource for dealing with a potential SUP case is FAA Advisory Circular (AC) 21-29, Detecting and Reporting Suspected Unapproved Parts (see Learn More at the end of this article for a link). This AC provides detailed guidance on how to identify unapproved parts, as well as prevent the procurement, acceptance, and installation of such parts.

It is important for all airmen to remain vigilant on this issue. If you identify a SUP, we are here to support you. So please send us a report.

Learn More

Advisory Circular 21-29, Detecting and Reporting Suspected Unapproved Parts -

Advisory Circular 20-62, Eligibility, Quality, and Identification of Aeronautical Replacement Parts -

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James Niehoff is an FAA aviation safety inspector and the SUP Focal Point with the Aircraft Maintenance Division’s Special Programs Branch.


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