CFR /  Title 14  /  Part 27  /  Sec. 27.1301 Function and installation.

Each item of installed equipment must--

(a) Be of a kind and design appropriate to its intended function;

(b) Be labeled as to its identification, function, or operating limitations, or any applicable combination of these factors;

(c) Be installed according to limitations specified for that equipment; and

(d) Function properly when installed.