A recent case is a flap relay for the Socata TB20/21. This is a Panasonic (formerly Matsushita) HG2-DC24V-F. There are two of them per aircraft.
The data sheet is here. It’s non-F predecessor is here.
The F was discontinued in 2012 and does not seem to exist anymore. It was on a 1 year lead time for many years. In recent years, some were found in the USA, at extortionate prices, and I have just enough as spares for myself.
The non-F appears to have the same specification for all practical purposes and does exist in the Far East but since this was discontinued c. 2004 this will be pretty old stock. And the P/N is “not the same” as the Socata part.
Socata still sell these, from some ancient stock, but at a crazy price – $1000 was reported by one US owner. The original price was about $20 in small quantities.
Eventually even the gold plated Socata (EASA 1 Form of course) option will dry up and then Socata will either abandon owners or, more likely, develop a mod kit involving a new bracket to carry a different relay base (there are obviously countless 20A 2PCO relays out there, but none fit the HG2 base). This mod kit is likely to cost four figures.
Obviously this question has been asked before – bypassing the documentation system is world’s second oldest profession and is a significant factor in the lower operating cost of a homebuilt plane 
AIUI, on an N-reg there is a procedure whereby an A&P can inspect a candidate part and if he can satisfy himself it is the same part as the one being replaced, he can install it. On EASA-reg this option appears to be entirely missing, except maybe for the curious route described here
Another route, probably illegal but not unknown on the G-reg scene, is for the mechanic to sign it off as having been removed from another aircraft of the same type (one 145 company told me they want the “donor” aircraft to have a valid CofA at the time – not sure if they invented this on the spot).
Another route, presumably legal, is for the 145 company to inspect the part and generate an EASA-1 form for it. But who can do that? Socata, like any airframe manufacturer, do this all day long and it is the cornerstone of the parts business being so valuable.
Another route may be to develop the whole mod kit and use a current model relay, but this will be viable only if it can be done as an EASA Minor Mod. But then if that is a Minor mod, why can’t one fit a “provably Panasonic HG2-DC24V-F” without paperwork, as a Minor Mod too?
As EASA C of A’s don’t expire I can’t see the valid C of A being an issue, there is no reason why a component can’t be inspected and a Form 1 issued as long as the inspector can trace the history of the item, it has not reached the end of its service life ( if it has one ) and it has been demonstrated to function correctly.
The minor mod route is avalable, and the new parts used in the mod given a form 1 as long as the EASA145 company doing the work has a certificate of conformity from the original manufacture.
Sometimes thing like that just mysteriously get fitted with no paperwork at all, never to be mentioned again. After all, no mechanic ever checks every serviceable part of a serviceable aeroplane
I don’t know whether the TC for the TB20 was issued before Jan 1st 1980, but if it was I presume you have read AC23-27….
http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_23-27.pdf
Edit: I think the TB series TC was first approved in 1984….Probably more applicable is AC20-62E….specifically para 11b….
http://www.faa.gov/documentLibrary/media/Advisory_Circular/AC%2020-62E.pdf
I don’t know about non N-reg….
Hmmm… well spotted! I have seen this before a long time ago and I think this bit
was done by the FAA to stop companies like Honeywell charging $500 for a capacitor (e.g. the 2.2uF capacitor here)
The Q is whether this allows the substitution of a relay.
EASA has no such concession AFAIK.
Yes it’s a pity relay isn’t specifically listed, but the wording is such that I don’t believe it is intended to be exhaustive….i.e. It is not lumped with ICs as being too specialized to be considered standard…..the other point in 11b is that it reads like it should only apply where there is no manufacturer’s part number (Socata in this case) listed for the part….so that may kill it…except that I believe the intent is to allow such substitution especially for non-Major Repairs…(Part43 App A does not included such parts in the listing for Major Repairs)…no 337 required…. If it were me I would just install the similar part with a logbook entry from my A&P referring to AC20-62E….
The curious thing about that (b) clause above is that the context (i.e. repairing some bit of electronics gear) is clearly outside pilot privileges, and outside A&P privileges (an A&P cannot do instrument repairs for example).
The context for radio gear repairs is usually a 145 company (true both FAA and EASA). I think we all know of small radio repair shops working out of a shed in the corner of the airfield; they can’t generate any paperwork AFAIK so their work is done “off the books”.
So it appears to be mainly a concession to 145 radio repair shops who no longer have to pay silly money for common components.
it should only apply where there is no manufacturer’s part number (Socata in this case) listed for the part….so that may kill it…except that I believe the intent is to allow such substitution especially for non-Major Repairs
Socata have a P/N for every last washer, but then so do most current or recent aircraft manufacturers. It’s a trick whose aim is to con lazy (or documentation-loving) maintenance personnel into buying commodity parts at 5x the price. It helps revenue generation too, of course, at the customer end. And if you look in the MM for say the KFC225 you find a King P/N for every resistor too.
This is a really interesting and potentially useful thread!
Peter wrote:
And if you look in the MM for say the KFC225 you find a King P/N for every resistor too.
In my understanding, this is no problem, as long as you can read the resistor / e.g. color code / size etc. I think the trick is that it says: “if not specifically marked by the equipment manufacturer’s part number or marking scheme. "
The resistor, is on the part list, The part itself is not MARKED with a Bendix/King P/N or Bendix/King logo, therefore it a standard part.
On a whelen strobe box, for example, many parts are standard parts, you will also have some parts (capacitors and some other IC’s) which are Whelen branded. As these are marked with Whelen IMHO you can not legally replace these capacitors by non Whelen one, while for those non branded resistor or small capacitors you can.
That’s interesting, Jesse. You think this applies to EASA-reg too?
BTW back to the flap relays, I have discovered that the old non-F version contains cadmium and is no longer legal for sale in Europe and USA. Aviation and military applications are exempted 
Yes I believe so, though the CAA inspectors don’t always agree during an audit, it will always be a point of discussion. I think this mainly is due to the fact that they have little or no handson electronic experiance and have a hard time believing that in electronics that is the way to do things. Also had discussion on Whelen lights, where we have Whelen supplied schematics and test specifications, but no manual. Some inspectors then tend to say that you can not repair, because there is no repair manual.
Same on coax cable, some would like you to order coax cable from an aviation vendor. When I ask which one, aircraft or avionics, they are unsure. Then I will them them they will issue a MIL standard, or says something like RG-58 or better. Which IMHO allows my to install RG-400 (which allows to MIL spec) and has a better performance then RG-58.
There will always be some struggle on those issues I guess.
