Text in force at 27-51: from 27-23, effective 3 Oct 1988.
For multiengine helicopters, the steady rate of climb (or descent), at VY (or at the speed for minimum rate of descent), must be determined with--
(a) Maximum weight;
(b) [The critical engine inoperative and the remaining engines at either--
(1) Maximum continuous power and, for helicopters for which certification for the use of 30-minute OEI power is requested, at 30-minute OEI power; or
(2) Continuous OEI power for helicopters for which certification for the use of continuous OEI power is requested.]
53 FR 34210 · Source