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CAVU Café: Royboy’s Prose & Cons

*Note: The views expressed in CAVU Café: Royboy’s Prose & Cons blog are those solely of the writer and are not necessarily shared by the Aviation Suppliers Association or the Association’s staff, members, or Board of Directors.


   About Roy Resto



You bump into a friend you have not spoken with in a while. The friend asks “so…are you still with Jane?” What should be a simple yes or no answer turns into a slightly awkward and delayed answer from you; “it’s complicated”. Use of the “it’s complicated” strategy  means that in order to be truthful with your friend, a quick answer will not do, and that the choice to give any additional details is optional (due to time limits or level of trust), and further, that if you don’t give any additional details it would be socially acceptable to move on. Of course, in the absence of additional details, your friend’s imagination would immediately and quietly embark upon a fit of creativity, which may find expression in the presence of other friends, maybe. So, what about standard parts? I would like to give a common, simple answer, but guess what? It’s complicated.

I’m wont to write this blog because in my consulting business I continue to run across confusion and misinformation about this topic in the industry, especially a lack of practical advice (herein bolded for ease of locating it), so I hope to impart some here. I’m going to cover the following topics:

·      Definition

·      Trace for standard parts

·      Lesser known standard parts

·      Standard parts that are only standard within the purview of the OEM

·      Documentation for standard parts


From FAA AC 20-62E titled “Eligibility, Quality, and Identification of Aeronautical Replacement Parts”:

·      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 to the part. The specification must be published so that any party may manufacture the part. Examples include, but are not limited to, National Aerospace Standard (NAS), Air Force/Navy (AN) Aeronautical Standard, Society of Automotive Engineers (SAE), Aerospace Standard (AS), Military Standard (MS), etc.

From EASA AMC M.A.501 (c):

·      Standard parts are:(a) parts manufactured in complete compliance with an established industry, Agency, competent authority or other Government specification which includes design, manufacturing, test and acceptance criteria, and uniform identification requirements. The specification should include all information necessary to produce and verify conformity of the part. It should be published so that any party may manufacture the part. Examples of specifications are National Aerospace Standards (NAS), Army-Navy Aeronautical Standard (AN), Society of Automotive Engineers (SAE), SAE Sematec, Joint Electron Device Engineering Council, Joint Electron Tube Engineering Council, and American National Standards Institute (ANSI), EN Specifications etc…

In these and other definitions I’d like to point out the important common denominator which is the standard part was manufactured in compliance with a Government, or industry accepted specification. For example, commonly cited part numbers such as may start with NAS, MS, or AN, are parts whose blueprints (specifications) were crafted by the Government.

Before going any further, here’s my first bit of practical advice: Write down this web site and put it in your favorites: Go there. On the Document ID line, type in a common standard washer AN960 and Submit. The result will have a link to the actual drawing (and whoopee, it’s free), and you’ll notice a note saying it’s been S/S (superceded) by NAS1149. In fact the link to the AN960 drawing will also take you to the official cancellation notice (a quick flutter of the eyebrows please). Neat huh?  We wish it were all so simple, right?

The problem arises with those pesky other standard part numbers that do not begin with NAS, MS, or AN, and indeed there are many. For example, you may be on the market for a certain part number, and a supplier informs you that the part number is a standard part number, really? This is the first illustration of the complicated issue. I have seen too many suppliers purport to have standard parts but can’t prove it in light of the aforementioned definitions. More practical advice: Ask to see the blueprint or specification for the part. If you are shown a typical manufacturer’s print with those tiny notes in the legend that say its proprietary, or any other equivalent language indicating its IP (Intellectual Property), then it’s not a standard part, period. But, you ask, Royboy, why would anyone want to claim a part is standard?


For new-condition aircraft parts you want to be able to demonstrate you have trace documentation to the PAH/DAH (Production Approval Holder or Design Approval Holder), in other words, trace to someone who typically possesses a TC, PMA, or TSOA. An exception to this requirement is that standard parts generally do not require trace to a PAH/DAH; you can obtain them from any source as long as you are provided the documentation I’ll review in the last section. So, here’s a practical example of how this comes into play: You’re on the market for a new-condition, certain part. A supplier informs you she has the part. You dutifully ask if they are a PAH/DAH? The reply: ‘that is not necessary, this is a standard part’. At this point your head bends down towards the table to be supported at the forehead by one of the palms of your hands as you realize things just got complicated. If the supplier cannot produce proof that the part is indeed standard (as is the case for many such suppliers), your head is now seen to bend down towards the table with the forehead supported by two palms; body language for a troublesome position indeed. Move on to another supplier. Royboy’s practical advice: If no supplier can prove it’s a standard part, go up the Next Higher Assembly (NHA) chain until you get the PAH/DAH and order the part from them.

…standard parts generally do not require trace to a PAH/DAH


A friend recently approached me who is on the market for an aircraft light bulb, part number 767. She said that a supplier told her the part was a standard part. It took some research, but my friends in the aircraft lighting industry told me to look at SAE Aerospace ARP881 titled “Lamps for Aircraft Lighting” and guess what? There it is. Many other part numbers are listed.

First we need to recall that both definitions I cited earlier included examples of Government or Industry accepted specifications. SAE is but one of those industry groups, and ARP881 is a perfect example. If you go to SAE’s web site and search on ‘Aerospace Lighting’, you’re going to get a lot of results. The challenge is that each standard has a price, so I can’t tell you that all those search results at the SAE web site will yield a listing of part numbers as did the ARP881. If any one of you has that information, please share it as a comment on this blog.

Of course there’s more. I have a pretty good avionics background so I know the electronics industry has a lot of standard part numbers. For example, 2N2222 is a common transistor (anything starting with 2N is a transistor), and anything that starts with a 1N is a diode. RL is similarly used for resistors. By the way, more practical advice; go back to the web site. In the “Word in Title” line, type in 2N2222, enter Submit. Uh-huh, more neat info. An ‘A’ awaits any college student willing to spend the time to research all those government and standards organizations to create an exhaustive list of standard part numbers cross referenced to the respective standard. Oh, yes, be sure to share it with Royboy


How about part numbers that start with BAC, ABS, or NSA? Are those standard parts as we established earlier? The answer is a stern no! BAC part numbers are only ‘standard’ within the purview of Boeing aircraft, and ABS and NSA within the purview of Airbus. Their drawings are IP, and so were not made by a government or industry group. As you can see, the problem is the industry loosely uses the term ‘standard part’ for both BAC/NSA/ABS, and AN/MS/NAS parts, but as you now know, there are critical distinctions between the two. Failure to make that distinction has resulted in reports of Suspected Unapproved Parts.

Let’s amplify this with some simple practical advice: When purchasing new BAC, NSA, or ABS parts ask the question: Is the supplier a PAH/DAH (do they have for example, PMA or TSOA for the parts? If the answer is no, get the parts from Boeing or Airbus, period. Just because a manufacturer is on some Boeing approved supplier list does not entitle them to sell BAC parts directly to end users (unless they have PMA or TSOA), and in fact such selling (AKA Direct Shipping) is a clear, reportable SUP. ‘Nuff said.

As you can see, the problem is the industry loosely uses the term ‘standard part’ for both BAC/NSA/ABS, and AN/MS/NAS  parts, but as you now know, there are critical distinctions between the two


For all standard parts, the expected documentation is some sort of Certificate of Conformity. BTW, see my blog titled ‘C of C’s, BEWARE THE DIFFERENCES’ at

Airbus recently sent out a message that it will start to issue EASA Form 1’s for its NSA and ABS standard parts, very welcomed.


Over ‘n out

Roy ‘Royboy’ Resto

Posted By Roy Resto | 6/2/2015 5:06:56 PM