14 CFR § 29.83

For each Category B rotorcraft, the horizontal distance required to land and come to a complete stop (or to a speed of approximately 3 knots for water landings) from a point 50 feet above the landing surface must be determined with—

Speeds appropriate to the type of rotorcraft and chosen by the applicant to avoid the critical areas of the height-velocity envelope established under § 29.87; and

The approach and landing made with power on and within approved limits.

Each multiengined Category B rotorcraft that meets the powerplant installation requirements for Category A must meet the requirements of—

Sections 29.79 and 29.81; or

Paragraph (a) of this section.

It must be possible to make a safe landing on a prepared landing surface if complete power failure occurs during normal cruise.