I work in the airline industry and arguments about what is MAJOR and MINOR repair or alteration still abound.
Yep. Same anywhere else in the industry; we bash our heads against Major vs. Minor all the time. And most places (in my experience) tend to the side of caution/CYA and assume it's Major if there's any question at all.
ADS-B does not effect, structural strength, performance, flight characteristics or other qualities affecting airworthiness. Same with autopilot. Both effects W&B but not significantly.
My best understanding of a "significant effect" on W&B means a change to the weight and balance
limits. Burning gas changes weight and balance but that's not a major alteration. But something that increases allowable zero-fuel weight or increases gross weight, or changes the allowable CG envelope, would be Major.
Part 43 Appendix A below is a good guide. Both these can be tested on the ground, but to verify operationally it requires a flight test. I would not say it requires FAA approval or Phase I. But both, especially the AP Servo are safety issues in that it could jamb-up the flight controls. Both require wiring and that could lead to an electrical fire.
Now, I'm not a DER, but I'd read the addition of an autopilot as a Major alteration because it changes the control system (Ref Part 43 Appendix A below) as well as having an effect on safety of flight. I'd say installing ADS-B on a homebuilt is not, as it doesn't affect those things any more than the installation of any other radio equipment would, and the required flight test for ADS-B is to ensure compliance with legally-required accuracy, not a safety-of-flight and performance check like the autopilot installation would be (more below).
Well I'm going to disagree with the AP install being a "major" alteration.
The AP is an add-on to the control system but does not alter it in a way that would change flight characteristics.
Rather than get into the nuts-n-bolts of control system alterations I'll use an example:
Current generation of STC's for AP installations on certified aircraft (GFC500) require only ground checks be performed, there is no flight test requirement.
So are we are being held to a higher standard than the certified world, I think not.
Are we just looking for ways to make life more difficult?
Installing an autopilot on a certified airplane via STC does not require flight testing under an experimental ticket, or even a flight test at all, because those installs are performed with known equipment, to known and controlled configurations, on specific aircraft types. All the design, analysis, and testing that went into that STC, and all the paperwork and such that went into the TSOs and other certs required to produce the parts, is meant to ensure safe repeatable results without having to duplicate the testing all over again. Indeed, that's a big part of the entire type and production certificate process--showing that building this exact design, with this exact process, will repeatably yield this exact performance.
Homebuilts don't have that. Each one is different, and (in the eyes of the FAA) considered a one-off aircraft type. You have to do the testing on a homebuilt to show that the modification is safe and to demonstrate proper performance (which in our case may likely involve tweaking the gains). We don't have configuration control, testing data, etc. to fall back on, so we have to demonstrate it. With the caveat that I too am a little annoyed at having to formally get The Man involved each time, I'd say that's a pretty small price to pay for the immense flexibility and freedom we enjoy with E-AB.
As an aside, that's why building an RV-12 as E-LSA has a shorter test period. You're gaining the repeatability benefits of a defined, exact configuration, although without the process control that accompanies a production certificate (or any other QC-controlled process).
But regardless, now we're back to the FAA's definition in Part 43 Appendix A:
(a) Major alterations -
(1) Airframe major alterations. Alterations of the following parts and alterations of the following types, when not listed in the aircraft specifications issued by the FAA, are airframe major alterations:
(i) Wings.
(ii) Tail surfaces.
(iii) Fuselage.
(iv) Engine mounts.
(v) Control system.
(vi) Landing gear.
(vii) Hull or floats.
(viii) Elements of an airframe including spars, ribs, fittings, shock absorbers, bracing, cowling, fairings, and balance weights.
(ix) Hydraulic and electrical actuating system of components.
(x) Rotor blades.
(xi) Changes to the empty weight or empty balance which result in an increase in the maximum certificated weight or center of gravity limits of the aircraft.
(xii) Changes to the basic design of the fuel, oil, cooling, heating, cabin pressurization, electrical, hydraulic, de-icing, or exhaust systems.
(xiii) Changes to the wing or to fixed or movable control surfaces which affect flutter and vibration characteristics.
Whether it "alters it in a way that would change flight characteristics" doesn't matter; the FAA says
any change to the control system is Major.
The only thing consistent with the FAA is inconsistency.
I often think the inconsistency and vagueness is deliberate,
