What must be true of a small unmanned aircraft's exposed rotating parts for it to be eligible for Category 1, 2, or 3 operations over people?

Why: 14 CFR §§ 107.110(a)(2), 107.120(a)(2), and 107.130(a)(2) each require that exposed rotating parts not be capable of lacerating human skin upon impact. AC 107-2A § 8.6.2, p. 8-17, notes internal/ducted designs, guards, or non-lacerating materials are all acceptable means of meeting this performance outcome — a rigid shroud is only one example, not the requirement itself.

• This overstates the requirement; AC § 8.6.2 and § 8.7 describe multiple acceptable approaches — internal ducted fans, propeller guards, or flexible materials that break away on impact — beyond a rigid metal shroud, since the regulation states a performance outcome, not a specific design.
• No RPM ceiling appears anywhere in part 107 or AC 107-2A; the standard is the laceration outcome upon impact, not the rotational speed of the part.