CAVU Café: Royboy’s Prose & Cons

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AFTERMARKET TAGS: Overhauled vs Repaired vs 2 Years

Time to stir the pot again

I continue to hear moans about the issues we’re about to discuss, so I dusted off and updated this classic prose which will address the purchasing of aftermarket spares (other than new condition). Many of you have shared privately with me that you forwarded links to the older blog to your customers, and this too prompted this update. In this blog we’ll review the following:

    • Reliability study
    • Lack of Overhaul instructions for many parts
    • Possible effects of unnecessary disassembly
    • Degrees of Airworthiness?
    • Concerns about degradation/deterioration
    • Concerns about the latest S/Bs, ADs, or software updates


I’m perplexed that so many purchasers continue to demand that parts, other than new, on the aftermarket must be in “Overhauled” (OH) condition. That’s for every part. Everyone knows that you will be charged more for OH condition than for Repaired or Inspected parts. When I question the practitioners of such requirements, the first answer I get is “It’s our policy.” OK, what’s that policy based on? If the person wears glasses, they’re seen to slide the spectacles down to the tip of their nose, and lower their head; the better to give your direct eye contact while they give you the lecture you deserve. “Why, don’t you know (you silly boy) that Overhauled parts last longer on the airplane? This translates to requiring fewer spares.” And there it is, the reason for the policy. Here are some thoughts to challenge that:

  1. For the overwhelming majority (not all) of your parts, you will not be able to statistically prove that use of purchased Overhauled parts vs. Repaired or Inspected last longer on the aircraft.
  2. Most Component Maintenance Manuals (CMM) do not literally contain “overhaul” instructions.
  3. The act of performing unnecessary disassembly may introduce the very reliability problems you hoped to avoid by using overhauled parts exclusively.
  4. Keep in mind that when you get a part with a serviceable tag from a repair station, an 8130-3 for example, the side that is signed says “Certifies that…was accomplished in accordance with Title 14, Code of Federal Regulations, Part 43 and in respect to that work, the items are approved for return to service.” In other words, for either OH, Repaired, or Inspected parts, you are getting an airworthy product! Repaired or Inspected parts are no less airworthy than Overhauled parts.

  • Reliability Study:

Let’s forget about statistics for a moment.

First jot down a few parts you’d like to test and research.

Start with your engineering department. Ask if any of the following programs address the parts you’re researching: MRB (Maintenance Review Board), MPD (Maintenance Planning Documents), and the MSG (Maintenance Steering Group) programs for your aircraft. A discussion of these programs is beyond the brevity of this blog, but your reliability engineer will assist. Suffice it to say that these programs form the basis for your Maintenance Operations. Do any of these address your components? Does it say anywhere that the part must be overhauled upon removal or replacement? There may be a few, but these are in the minority; it’s likely you will not find any such requirements for the majority of parts on your list.

OK, let's assume you can’t substantiate the 100% Overhaul Policy through any of those documents. Talk to your reliability engineer and ask if there has been any past “history” forming the basis of the overhaul policy. If not, talk to the engineer and apprise them that you are switching your policy to accept Repaired or Inspected parts. The engineer will monitor the MTBF (Mean Time Between Failure) trends. If there is a correlation between MTBF negative trends and the use of Repaired and Inspected parts vs. Overhauled parts, then your policy would be vindicated. I’m here to prophesy to you that you’ll likely not see any such negative trends. Such data would form the statistical basis for your policy if it existed. If you don’t have it, why continue doing business the same expensive way? Read on please.

  • Lack of Overhaul instructions for many parts:

Most Component Maintenance Manuals (CMM) do not literally contain “overhaul” instructions. If this is true how can repair stations accommodate your request to have parts overhauled? Let’s look at an example. Let’s assume you have an avionics computer of some sort. Its CMM does not contain any ‘overhaul’ instructions (just the typical inspection, check, and repair instructions), but you insist that it be in overhaul condition. They’ll be happy to accommodate you, and the expected higher fees they’ll charge, by following the FAA’s definition of ‘Overhaul’ found in FAR 43.2. It states that no person may describe a part as being overhauled unless “Using methods, techniques, and practices acceptable to the Administrator, it has been disassembled, cleaned, inspected, repaired as necessary, and reassembled; and it has been tested in accordance with…”. So, the CMM would not have required a disassembly and cleaning unless there was a failure of some sort, but because you insist on an Overhaul, they’ll do it anyway so as to meet the requirements of the FAA’s definition of Overhaul, and to be able to list its condition as such in block 11 of the 8130-3. Keep in mind this was a simplistic example, but it is quite realistic.

  • Possible effects of unnecessary disassembly:

One more thing, a subject for profound thought and fluttering of the eyebrows: there is a great body of folks in our industry whom believe that parts should not be disassembled unless specifically called for in a CMM because this act in itself greatly increases the risks that an error, bug, or mechanical deficiency could be introduced when reassembled; such is the reality when human factors are involved, so keep in mind that your insistence for fulfilling the requirement for an overhaul may introduce the very reliability problems you thought you’d avoid with the overhaul policy.

  • Degrees of Airworthiness?

I’d like to conclude the discussion on the OH requirement by addressing a veiled apprehension: You may be concerned about the parts you buy on the aftermarket, and thus have those concerns assuaged by having all the parts Overhauled. I may not be able to argue you out of that position, but I do suggest the following: Send it to the MRO of your choice, and ask them to inspect and repair the part as necessary. In addition, specifically ask for a hidden damage inspection on your Repair Order. They’ll look at it closer, and you’ll likely get charged less that a full overhaul. Cool idea huh? Oh, and one more thing (I feel the urge to pontificate): If you feel proud of the fact that you supposedly have a higher standard requiring the overhaul policy, I’m here to tell you that you’re selling yourself short. A higher standard than overhaul is the condition of “Rebuilt” (ref FAR 43.2). Yes this is an acceptable term for block 11 of an 8130-3. Your part will meet all the testing requirements of a new part with the exception that it did not just roll off the assembly line. Price that with the OEM!


Another black and white policy that continues to make me shake my head in amazement is some operator’s policy that any parts purchased must have tags no older than two years. When I ask why, the glasses are seen to slide to the front of the nose again. “Don’t you know (you silly boy) that parts can deteriorate or degrade just sitting on the shelf?” Oh brother…, What are the historical arguments for this policy?

  1. Concerns about deterioration of one sort or another
  2. Concerns about SB’s, AD’s, or software changes that may have taken place while sitting on the shelf

  • Concerns about degradation/deterioration

First, what ever happened to following manufacturer’s recommendations for shelf life as may be contained in a CMM if applicable? Typically, if there is a shelf or storage life, the CMM will contain it in its Storage section, or equivalent, of the manual. If it does not exist, why pay for the additional expense of having it sent back to a shop for a fresh tag? Alternatively, this is only defensible if you have supporting statistical or reliability issues as previously discussed. Do you?

  • Concerns about the latest S/Bs, ADs, or software updates

Questions about SB’s, AD’s, or software changes that may have taken place while on the shelf represent the best concerns for the 2 year tag defense.

Let’s not overlook the obvious, however: if this is indeed your concern, those issues could have manifested themselves in the two year time frame for the parts you’d accept with tags less than two years, right? So how do you currently address that possibility? The person is seen to retract the glasses to its proper position on the nose bridge. A probable response is that you know the product you are assigned to purchase, and thus would likely know about AD, SB, or software issues. Your Purchase Order (PO) should always include special instructions to your supplier that you require the part delivered with SB’s, AD’s or software installations accomplished when applicable. After all, there are many SB’s, AD’s and Software installations whose implementation method and requirements depend on the operator’s management of those issues. Finally, we are fortunate that many SB’s, AD’s, and Software installations change the part number, so if you get the part number you’ve ordered you’ve likely got the AD, SB, or software level required. If still worried, put the required level on the PO.

Over ‘n out.

Roy ‘Royboy’ Resto

Posted By Roy Resto | 4/4/2017 1:42:45 PM

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