14 CFR § 27.75

The rotorcraft must be able to be landed with no excessive vertical acceleration, no tendency to bounce, nose over, ground loop, porpoise, or water loop, and without exceptional piloting skill or exceptionally favorable conditions, with—

Approach or autorotation speeds appropriate to the type of rotorcraft and selected by the applicant;

The approach and landing made with—

Power off, for single engine rotorcraft and entered from steady state autorotation; or

One-engine inoperative (OEI) for multiengine rotorcraft, with each operating engine within approved operating limitations, and entered from an established OEI approach.

Multiengine rotorcraft must be able to be landed safely after complete power failure under normal operating conditions.