14 CFR § 29.65

The steady rate of climb must be determined—

With maximum continuous power;

With the landing gear retracted; and

At Vy for standard sea level conditions and at speeds selected by the applicant for other conditions.

For each Category B rotorcraft except helicopters, the rate of climb determined under paragraph (a) of this section must provide a steady climb gradient of at least 1:6 under standard sea level conditions.