Advanced SUP knowledge may reduce risks and save money

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Which replacement parts are legal/safe?

Flying Magazine provides a nuts-and-bolts explanation

 Plus business and regulatory rationales for SUPs

Below is a superb review of the vagaries of suspected unapproved parts. The FLYING article was written (including an incredible quote from Friedrich Nietzsche) by an  A&P Mechanic, Embry-Riddle Aeronautical University graduate whose practical experience with parts includes having owned a 145 repair station, currently a Technical Analyst for a major airline and MRO. He walks you through the nuts and bolts of deciding what parts are safe and meet the FAA regulations.

All too often, it can be heard “that FAR makes no sense, why should I spend time and/or money to comply?” As with many requirements, there are substantial safety reasons for meeting an insipid standard.

Airplanes are expensive and it appears that the replacement parts are even more costly. Why? One hypothesis is known by the label King Gillette business model of selling razers cheaply to sell razer blades at a higher price.

Whether that is true or not, what is known is that the replacement parts actually incur regulatory-mandated expenses that do not impact the exact same part at the hardware store. From a form, fit and perhaps function, the retail part may appear to be the same; in regulatory sense, THEY’RE NOT!!!

SUP partsAs part of the Part 21 certification process, the TC applicant must show that every element of its proposal can meet very demanding airworthiness tests. So, while Part A and Part B may be visual replicas, Part A is the result of a proprietary manufacturing process which makes it stronger, more durable, more heat resistant or whatever. Thus, Part B may not be fit to endure the FAA testing that Part A did.


Part documentation is a PHD course. The above 8130 is the best evidence, but it is not always attached to a single bolt or screw. What then? While Mr. Scarbrough’s paper suggests, the information required to make such judgments are long and obtuse. If you want to increase your confidence in determining what is an airworthy partSUP class v. non-compliant one, time (class or virtual) with some Subject Matter Experts will allow you to further explore the indicia of what’s FAR compliant by hearing their hypotheticals and posing your personal tests.

Another legitimate reason for the differential between system I and System II prices could be the massive research that contributed to the I appliance’s greater reliability, and/or the inventory control (security or controlled warehouse environment or distribution or supply availability…) or the paperwork tracking.

Whatever the reason for the higher price tag, buying from a reputable source is the best path to greatest safety reduction.

part numbers are important



Are You Flying With Approved Aircraft Parts?


SUP parts

A bit of due diligence now can save you an expensive headache later, or worse.

By Richard Scarbrough

February 10, 2022

Pulling up to the hangar, you are eager to check the progress of the work on your airplane.

The installation of your Garmin, Aspen, or Avidyne avionics finally finished up last month, and you need a little more time familiarizing yourself with them before that big cross-country flight next month. The cost consumed your entire profit-sharing bonus, but it was worth it.

GA MX hangar

A local mechanic stops by the hangar whenever needed. He has a key and should have started work on that bracket replacement while you were still stuck in traffic, trying toquestion leave the city. You cannot wait to shed this dreadful day and get airborne to clear your head.

The look on your mechanic’s face tells you all that you need to know. Something is wrong. From the look of things, you won’t be circling the pattern tonight.

“Where did you get that hardware you left for me to use on this installation?” he says grimly.

You reply, “My son found them on an aviation surplus inventory website. Why?”

After a long pause, your mechanic flatly states, “Well, one of them just sheared off in the engine case.”

Replacements Parts Are a Serious Topic 

Aircraft replacement parts are a crucial component of continued airworthiness. Friedrich Nietzsche once famously said


Nietzsche failed to mention maintenance, as one must maintain the aircraft to fly successfully.

Even the smallest replacement part can ground an airplane, as was demonstrated in our parable above. Garmin makes cool stuff. Have you seen the new watch? However, it’s the little things that can make all the difference in the installation of new equipment.

One of the biggest questions many aircraft owners face is: How do I know the parts I am flying behind are approved and not some garage sale knock-off? Well, that is a multibillion-dollar question.

The seriousness of approved replacement parts is critical. It’s far too important to rush through. This article is the first installment in a series covering aircraft spares.

The FAA has a term for aircraft material that does not meet the standards for installation, and return to service  suspected unapproved parts (SUPs). Just because a bolt fits in the hole and torques to specs does not necessarily mean you are good to go. Approved aircraft parts must conform to strict guidelines.

SUPs ?In 1995, the FAA committed to addressing the issue of unapproved parts by establishing a program office dedicated to SUP material. The scope of aircraft maintenance, parts handling, and flight operations is far too immense for one agency to control. So, aviation essentially is a “self-policing entity,” with everyone holding each other accountable.

I can say that my 30-plus years in aircraft maintenance and parts distribution have introduced me to all sorts of characters, unsavory and otherwise. The rogues are very few and far between. The vast majority of my interactions were with professionals that took pride in their role and operated with the utmost integrity.

The FAA has a series of documents to help you get started in your quest to fly in compliance. What follows is by no means an exhaustive list. In time, we will cover much more territory as we navigate aircraft parts and spares together.AC No. 20 62E

FAA AC 20-62E, “Eligibility, Quality, and Identification of Aeronautical Replacement Parts,” is a great place to start. This advisory circular provides a wealth of knowledge of aircraft parts. It’s required reading for anyone dealing in parts, maintaining aircraft, or operators interested in what goes on under the cowling.


FAA AC 21-29, “Detecting and Reporting Suspected Unapproved Parts,” spells out the program parameters and offers guidance for navigating the sometimes tricky world of aircraft parts and materials.




FAA Order 8120.16A, “Suspected Unapproved Parts Program,” is intended for FAA personnel, but could be a deeper dive if you are an avgeek like me and read aviation regulation documents for fun.

AC 21 29D

The Aviation Spares Aftermarket

SUP stopThe entirety of the aircraft parts aftermarket is massive and will only continue to grow. Fortune Business Insights recently stated that the aircraft parts aftermarket will exceed $47 billion by 2028. This growth creates both opportunities and challenges for owners, operators, and maintenance professionals when it comes time to procure parts.

aftermarket quote

Let’s start with the basics. We will get to more complex items, like line replaceable units (LRUs), later. The AN960-5 is a plain washer, has no unique characteristics, and is very unassuming. It is probably the same thing you can pick up at Ace Hardware or Napa, right? Wrong. The “AN” portion of the part number denotes the mil-spec standard it was manufactured to, in this case, a mil-spec standard “Air Force-Navy.” The 960 determines the style, and the -5 represents the bolt size the washer accommodates.

Where does one obtain such a part, and in doing so, how can you tell if it is approved? The popular aviation parts online marketplace returns eight pages of listings for AN960-5. Which company has approved parts? Who is cheaper? It’s just a washer, what harm could it do? Tread carefully. I once worked with an airline that unknowingly installed bad washers on their braking systems and almost grounded the entire fleet because of the ensuing corrosion.

The above questions are all excellent. After reading AC 20-62E, you are in a much better position to answer them. Even so, not every part is going to have back-to-birth paperwork and flawless traceability. You still need to do your homework and strive at all costs to stay approved and operate in compliance.

Operating in the Green

As stated above, the number of business entities advertising themselves as aircraft parts distributors numbers in the thousands. This list does not include the undocumented dealers, private sellers on the airfield, or eBay aficionados listing parts they acquired through the years. There are some approved parts on eBay, and if you buy parts from the popular auction site, do so with care, diligence, and a discerning eye.

The best defense you can have against the threat of a SUP is to buy consistently from trusted suppliers.

I recently connected with Mark Ginn, FAA/DAR-F, and the director of quality and accountable manager for Wencor, an aerospace parts distributor. Mark offered some valuable insights on the aftermarket. He has tips on staying compliant and advice when the time comes to buy.

I asked Mark what ensures Wencor is accredited to distribute aircraft parts.

“To ensure we meet operational requirements, Wencor presently holds recognized industry quality management standards that include ISO 9001:2015, AS9100, AS9120, and ASA-100 and [we] are also accredited [under]FAA 0056B as an aerospace distributor.”

We talked about different aspects of suspected unapproved parts, and he highlighted the following:

How can aircraft parts distributors protect themselves against counterfeit goods?

  • Maximize availability of authentic products.
  • Procure products from reliable sources, assuring authenticity and conformance.
  • Control products possibly identified as suspect.
  • Report products to other potential users and government authorities.

In the unfortunate event a situation is identified, what are the steps taken by the company to mitigate the risk?

Within the approved quality management system, a process addresses this situation in case of an occurrence.

Included in this process are:

  • Initiation of the event
  • Containment of the suspect product
  • Notifications
  • Investigation
  • Closing

What advice can you offer to an aircraft owner, pilot, or mechanic when purchasing aircraft hardware?

Do business with an accredited supplier operating within an aerospace standard, including a robust supplier oversight program, an internal receiving program with exact criteria, and well-trained/experienced personnel.

These resources will help arm you with information when it comes time to purchase. No system is fail-safe, and it is impossible to completely guarantee fully traceable and compliant parts.

The bottom line is to listen to that inner voice of reason that asks, “Why is this actuator $500 while all the others I have seen are $5,000?”

That little voice may save you a big headache later on.

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1 Comment on "Advanced SUP knowledge may reduce risks and save money"

  1. This article barely scratches the surface on the costs of getting a part approved. My last project with the Los Angeles ACO took 9 years (A TC is only supposed to take 5 years). What if you are having to pay an engineer a wage during that entire time? How many articles do you have to sell to break even on wages? The DER and test lab cost another $35k. There were six months of testing that I was able to do in house. The final cost for one piece of paper is mind-bending and I am a three-man shop.
    On the other side, the FAA is playing lip-service to SUPS. I received parts from Grimes (Honeywell) through Aviall Boeing). Grimes’ own parts do not meet all of the part 45.15 marking requirements for PMA parts. I have been battling this for 30 years with the local FSDO and MIDO. Seemingly Grimes is immune to marking requirements or their enforcement. When the local FSDO ASI came to my shop he sensed an opportunity to seize a career advancing moment. With certain SUP’s in his hand, his only concern was who I was selling the parts to in order to make an easy bust. Additionally, there is a repair station that is known to take “liberties” with other people’s PMA’d parts; my own and Aviall (Boeing) that I can prove. This has been going on for years. When asked directly “How do you do this?” their response is “Our FAA let’s us do it”. How does the FAA talk SUPs and then not enforce when presented with a chronic repeat offender? The FAA needs to give their own people more training on what is permitted in a repair station. Specifically, just because you have the proper tools for a job does not necessarily allow you to perform the work.
    At the end of the day those of us who repair aircraft need to be diligent in all aspects of our trade. My standing question is: “after your repair, are you willing to put your wife and children on that aircraft?”. If the answer is no you are not doing your job. That mind-set also removes the complaint about the cost of parts you are using.

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