Originally Posted by
212man
Surely it's a question of whether they have an FAA STC? Anything attached to the aircraft will need one I think. Or there's a lower level of approval but can't recall the Form number.
Not sure that's the case. The harness wouldn't require an STC as it is inside the aircraft and requires no tools to remove/install, doesn't interface with the electrical system, and would only attach to existing hardpoints. Don't see why it would require a 337 either.
To KiwiNedNZ's question, I believe it's more a question of if the equipment would meet TSO standards:
https://www.rotor.org/news/tso.pdf
However, that TSO only applies to HEC (133D) / "dope-on-a-rope" operations, not for those with the personnel inside the airframe.