CS-VLA 1351  General

ED Decision 2003/18/RM

(a)                            Electrical system capacity. Each electrical system must be adequate for the intended use. In addition -

(1)                            Electric power sources, their transmission cables, and their associated control and protective devices, must be able to furnish the required power at the proper voltage to each load circuit essential for safe operation; and

(2)                            Compliance with sub-paragraph (a)(1) of this paragraph must be shown by an electrical load analysis, or by electrical measurements, that account for the electrical loads applied to the electrical system in probable combinations and for probable durations.

(b)                            Functions. For each electrical system, the following apply:

(1)                            Each system, when installed, must be -

(i)                             Free from hazards in itself, in its method of operation, and in its effects on other parts of the aeroplane;

(ii)                            Protected from fuel, oil, water, other detrimental substances, and mechanical damage; and

(iii)                           So designed that the risk of electrical shock to occupants and ground personnel is reduced to a minimum.

(2)                            Electric power sources must function properly when connected in combination or independently, except that alternators may depend on a battery for initial excitation or for stabilisation.

(3)                            No failure or malfunction of any electric power source may impair the ability of any remaining source to supply load circuits essential for safe operation, except that the operation of an alternator that depends on a battery for initial excitation or for stabilisation may be stopped by failure of that battery.

(4)                            Each electric power source control must allow the independent operation of each source, except that controls associated with alternators that depend on a battery for initial excitation or for stabilisation need not break the connection between the alternator and its battery.

(c)                            Generating system. There must be at least one generator if the electrical system supplies power to load circuits essential for safe operation. In addition -

(1)                            Each generator must be able to deliver its continuous rated power;

(2)                            Generator voltage control equipment must be able to dependably regulate the generator output within rated limits;

(3)                            Each generator must have a reverse current cut out designed to disconnect the generator from the battery and from the other generators when enough reverse current exists to damage that generator;

(4)                            There must be a means to give immediate warning to the pilot of a failure of any generator; and

(5)                            Each generator must have an overvoltage control designed and installed to prevent damage to the electrical system, or to equipment supplied by the electrical system, that could result if that generator were to develop an overvoltage condition.

(d)                            Instruments. There must be a means to indicate to the pilot that the electrical power supplies are adequate for safe operation. For direct current systems, an ammeter in the battery feeder may be used.

(e)                            Fire resistance. Electrical equipment must be so designed and installed that in the event of a fire in the engine compartment, during which the surface of the firewall adjacent to the fire is heated to 1100°C for 5 minutes or to a lesser temperature substantiated by the applicant, the equipment essential to continued safe operation and located behind the firewall will function satisfactorily and will not create an additional fire hazard. This may be shown by test or analysis.

(f)                             External power. If provisions are made for connecting external power to the aeroplane, and that external power can be electrically connected to equipment other than that used for engine starting, means must be provided to ensure that no external power supply having a reverse polarity, or a reverse phase sequence, can supply power to the aeroplane's electrical system.