Avionics upgrade on N-reg in Europe

What you figured is roughly correct. If the equipment is being installed under an STC, any A&P IA is authorized to sign off the 337s, so any issue he has is personal or business related. Another IA should be found. Assuming the shop is technically competent and can show the IA how the work was done in accordance with the STC, the only IA competence issue is whether he can generate a proper 337 write up, which isn’t rocket science. Also, 337s regardless of quality aren’t further reviewed or further approved after IA sign off, only mailed to the FAA. For work under an STC you don’t need any discussion with a FSDO.

I’m with you on Garmin.

Is it pressurised? In EASA world (if I remember rightly) installing new avionics in a pressurised aircraft might be a major mod, not sure how it is in FAA world…

A general avionics upgrade will always be a major mod under FAA regs, pressurized or not. That’s assuming you are adding more than the odd non-primary instrument not connected to anything else.

I agree with Silvaire. Find another IA that will support you. I have upgraded my aircraft’s avionics several times over the past 20 years and up until last year all those upgrades were done by the avionics shop and signed off by the A&P/IA who does my annual. The avionics shop recently obtained their own FAA certification so they can now sign the work off themselves. There are several of these around Europe, if you are prepared to travel. But it is always nicer to be near the aircraft while the work is being done so you are available personally for any discussions that might arise.

Try to get it all done under STC(s) if you possibly can. Otherwise you’d need a field approval which in Europe is costly and a PITA. For field approval of a major avionics upgrade you’ll want a DER to sign off on the paperwork which pretty much guarantees that the FAA will rubber stamp it without any questions asked. But using a DER will normally involve some back and forth which takes time and adds $$$. For simpler field approvals (e.g. installing a heated AOA), your A&P/IA will likely be confident enough to do it herself.

I think in the given context – a sizeable avionics upgrade on a twin TP which is likely pressurised – this will be a Major alteration.

Otherwise, you can do quite a lot under Minor. For example there is an old general FAA concession (sorry I don’t have the ref but @ncyankee may have it) for installing something like a GNS530, so long as there is no autopilot connection. You can connect the usual stuff to it e.g. fuel totaliser. The issue with the AP connection is that the AFMS for the AP needs amending and that is a big job in regulatory terms.

This search digs out some very good threads containing the various options. In Europe, a Field Approval is indeed hard (I have done 3 of them, all via contacts in the US since the FSDO responsible for Europe is totally dysfunctional) so for many years European avionics shops have paid a US based DER to do the 8110 form route, which normally cost the client another 2k, as a baseline, but the great advantage is that the finished package gets sent to the FAA with the 337 for filing and nobody there looks at it, so it is “zero risk”. Some kit has gone in under the original factory TC (use the MM/IPC as the approved data) which is great because often the factory has approved what you want some years after you bought the plane, but often this route is airframe S/N restricted only to the later airframes.

A pressurised hull complicates antenna installations. @wigglyamp should know quite a lot about this. I’ve never done this but believe a DER is generally used.

All completed Major work is sent to the FAA for filing with a 337 form. Upon completion of the job, it is as Silvaire says. Any A&P/IA is authorised to inspect and sign this. Every A&P/IA knows this, and, IME, if one doesn’t want to be involved it is because something “smells”. In one case which cost me a massive amount of hassle and grounded me for 2-3 months, it turned out the guy was moonlighting (had a full time job, and was not supposed to work elsewhere) but didn’t want to disclose this to the client so he did the classic thing of being “non-responsive”, in the hope that the client will “get the message” and find somebody else. The problem was that the client was the hangar owner so the politics got really tricky. I did eventually find another A&P/IA and sorted it. There are other scenarios which can come up, with freelance people; aviation is full of politics.

As silly as it may sound, will the A&P/IA that does your annual not work with the shop to make the install happen? I mean, even when all the t’s are dotted and all the i’s crossed, the annual is when skeletons come out of closets. Or PPI, but it is not the case here.

It does not take much skill to write up a 337, I’ve done 100’s of them. I just can’t do the work or sign one off. The IA should review the installation to make sure it complies with the STC IM and with AC 43.13-1B/2A..There are usually specific instructions that need to be complied with in addition to the wiring. An updated equipment list needs to be generated along with a W&B. The electrical load analysis should be determined to ensure the alternator continuous load is within limits, usually to not exceed 80% of capacity. Components need to be mounted in the correct locations and structurally sound. The wiring should follow standards a be properly tied up. Circuits should be properly protected with circuit protectors. The configuration should be validated and all the ground tests performed. There is usually a check list in the IM for this. Interference with wiring or components and controls should be inspected. Antennas should be inspected. Everything should comply with the STC The IA does not need to have an avionics background to determine the interconnect or use of avionics test equipment to inspect the installation.

I got some avionics prices lately for a big upgrade a guy wanted to do on an aeroplane I was selling. He didn’t buy it, someone else did. Multiflight in Leeds Bradford were very reasonably priced, maybe 35% less than the other quotes. I think they are well worth a call.

tmo wrote:

As silly as it may sound, will the A&P/IA that does your annual not work with the shop to make the install happen?

It’s not silly in any way… any electrical major mods done on my plane (e.g. new transponder and ADS-B/antenna installation) has had 337s signed off by the same mechanic who does my Annuals. The work itself has been done by another guy who is a great avionics and electrical A&P, but who is terrible with any kind of paperwork and doesn’t have an IA. He can just barely manage an airframe logbook entry if I help him

One thing that may be unclear reading the posts above is that work requiring a 337 is by definition a major modification (or major repair). However if an STC is available for the modification, as with the avionics mentioned by the OP, all that is required for approval is that any A&P IA sign off the 337 and that it be mailed to FAA for inclusion in their file on the aircraft.