First, the FAA (U.S.) specific items. RB1957 is right; but there is a bit of confusion out in industry. A couple years ago, Aircraft Certification and Flight Standards put their heads together (may have been the first and only occurrence) and came up with a listing of "these must be STC'd", actually more like, "this is what can be Field Approved and this is when you need engineering" (DER or ACO). See Order 8300.10, Change 21, Figure 1-3 "Major Alterations Job Aid." Under Transport Airplanes item 3.F.(1) Vol. 2 page 1-27 it says:
"Changes to the aircraft structure, cabin interiors, or equipment relocation that affect crashworthiness and/or emergency evacuation. This includes initial installation or relocation of seats."
One the one hand, this is wonderful since at least there is now guidance. On the other hand, more specific examples would be nice! Having been subjected to this for a few years now, this is how it plays out:
- first outfitting of aircraft: STC
- change of seating type (2 singles in place of divan): STC
- change of seating features (add leg rests, change to berthing divan): not an STC
- change one model seat to another similar model seat (like-TSO): not an STC
I am really hoping this thread takes off, see how it is being applied elsewhere. "Initial" is rather vague, even "relocation" can be confusing.
Second, general applicability (world-wide). Seats must be appropriate for the load factors involved. Hopefully on a data plate right on the seat. Also must meet the certification basis for the aircraft in which they are being installed (no TSO-C39b seats in a dynamically certified airplane, 25.562). Dimensionally they must be compatible. Strength has to be there. And don't forget cabin safety, which includes (but is not limited to...):
- placarding
- life vest access
- oxygen mask accessibility
- aisle width
- ordinance sign readbility
- occupant egress
- exit access
No list can be comprehensive. Interior compliance inspections always scare me heading in - what am I going to find that I never saw before? Just the other day, I saw a speaker installation that COULD be blocked by a seat. PA checks are always advisable.
Hope this helps, and more than that, I hope it starts a discussion.