§25.1310 Power source capacity and distribution

(See AMC 25.1310) (a) Each installation whose functioning is required for type certification or by operating rules and that requires a power supply is an "essential load" on the power supply. The power sources and the system must be able to supply the following power loads in probable operating combinations and for probable durations (see AMC 25.1310(a)): (1) Loads connected to the system with the system functioning normally. (2) Essential loads, after failure of any one prime mover, power converter, or energy storage device. (3) Essential loads after failure of - (i) Any one engine on two-engine aeroplanes; and (ii) Any two engines on three-or-more engine aeroplanes. (4) Essential loads for which an alternate source of power is required, after any failure or malfunction in any one-power supply system, distribution system, or other utilisation system. (b) In determining compliance with sub-paragraphs (a)(2) and (3) of this paragraph, the power loads may be assumed to be reduced under a monitoring procedure consistent with safety in the kinds of operation authorised. Loads not required in controlled flight need not be considered for the two-engine-inoperative condition on aeroplanes with three or more engines.