14 CFR §29.65

1. (a)The steady rate of climb must be determined—
   1. (1)With maximum continuous power;
   2. (2)With the landing gear retracted; and
   3. (3)At Vy for standard sea level conditions and at speeds selected by the applicant for other conditions.
2. (b)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.