I read somewhere, years ago that any mil-spec item is OK to install in an aircraft, directly.
It was claimed that instruments (e.g. temperature indicators and even altimeters) from a military aircraft have been installed with just a logbook entry.
I doubt this was ever true (I mean legal) but it is a valid question whether a mil approval is good as Approved Data. I don't think it is the case necessarily.
Moving further down the significance scale, is a mil-spec Amphenol connector like e.g. these automatically acceptable as a connector for an unpressurised GA installation?
All items used in an aircraft with an ICAO CofA are supposed to come with evidence of traceability (8130-3 is just one of the possibilities but most small parts don't come with an 8130-3) but that leaves the question of suitability for the application. A simple connector is not going to be a PMA or TSO part (unless the vendor has done a TSO for marketing reasons) but in terms of e.g. the environmental and electrical performance a milspec connector will be easily good enough.
It is a fact that avionics installers everywhere have a big box of mil-spec circular and other connectors which they use as needed, and any paperwork for those was lost long ago.
It is also a fact that you can buy a $10000 TSOd instrument which uses connectors of way lower quality e.g. el-cheapo DB25 Chinese types with formed (not machined) pins. So TSO does not imply any specific quality level.
What are the rules on this?
I thought the whole point of Mil Spec was that all components were traceable to source; no paperwork, no Mil Spec!
Define 'mil-spec'.
If someone points at a component and says "that is mil-spec" then how can it be verified? I'd want to know which military specified it, when, and what they specified it for. And I'd want a paper-trail to prove it - I'm not just going to believe someone who sounds confident about it, and I wouldn't necessarily believe the manufacturer either.
Once all that is overcome, just because a military force once used it that doesn't make it perfect, or even at all appropriate for the application concerned.
Used on it's own, and without detailed knowledge of a particular component and application, I find a term like that essentially meaningless.
In semiconductors Mil Spec would be identifiable by the part number printed on the device. That is rather more than you could do with say an Altimeter. I could point to it and say it's Easa approved and you would not know whether it is or is not.
As Peter says, "approval" in an aviation sense is nothing more than a paperwork exercise. Mil-spec components are genuinely made or selected to a specific quality standard or specification.
Given the amount of counterfeit aviation parts around which presumably have audit trails, I wouldn't have a lot of confidence in the aviation paperwork either. All you need is a £50 inkjet printer and hey presto, EASA form 1.
Mil-spec components are genuinely made or selected to a specific quality standard
I still wouldn't overly trust them.
I remember an experiment by AMSAT where they sent a couple of relays into space. The relay that failed first was space qualified (and grossly expensive), while the commercial ones happily continued to work.
If you make a commercial product and ship millions of it, you better had your processes under control, because otherwise the returns alone would kill you financially.
If you make tens a year of a high priced MIL product a year, you don't have your processes that well under control (because you have so little operational experience), and returns don't kill you, given the high margins.
So I'd still trust a commercial product with a proven track record far more than some expensive MIL part that comes with JANTXV stamped on it.
I think much depends on what it is.
Take connectors - as in my original post. It's obvious which are probably very good and which are probably crap. The €20-50 circular ones from e.g. Amphenol are of a very high standard. At the other end of the scale you can get a tin plated formed-pin DB9 connector for €0.20 which will corrode rapidly.
As regards relays, that's more tricky. In an aircraft you probably want sealed relays, because humidity is a killer, and also in case of a fuel leak. Most of those are expensive. A lot of aircraft relays are motor vehicle relays, which are clearly reliable (nowadays) in cars but they are not sealed, and in an aircraft they are not in a sealed box which nowadays is the case in cars. As an example, Socata use four €3.50 non-sealed car relays on the "avionics master" relay board which they sell for €700. Those relays do pack up, despite the infrequent use in an aircraft. If I was doing this, I would use sealed relays, and they would probably be milspec.
However my original question was whether milspec amounted to some level of "approved data". Both Minor and Major mods are supposed to be supported by approved data.
American Mil-Spec is actually one of the main things making light aircraft practical - specifically because if we couldn't buy MS and AN fasteners commercially, we'd be stuck sourcing hardware from an airframe or PMA manufacturer.
Re the 'approved data or not' question, I'd imagine any part conforming to the Mil-Spec is OK if the aircraft parts book specifies the part by Mil-Spec instead of by a specific manufacturer part number. Otherwise, for a modification, the Mil-Specification itself (which is typically available on-line) can be used as supporting data in a field approval. Just my guess.
As it happens, all automotive relays are sealed these days, but we are increasingly using Smart FET devices. If the TB20 uses plug in automotive relays there are sealed versions of many types, I can possibly help there...
