AMC 25.1357(f) System Power Removal

• ED Decision 2008/006/R found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

AMC 25.1357(f) System Power Removal ED Decision 2008/006/R 1 Subparagraph 25.1357(f) requires that circuit breakers are not used as the primary means to remove or reset system power for those aeroplane systems for which the ability to remove or reset power during normal operation is necessary. 2 It is not the intent of the requirement that every electrically powered system in the aeroplane has a means to remove power other than a circuit breaker. The phrase “normally requiring power removal” is used to distinguish between aeroplane systems normally turned on and off during normal operations, and those systems normally powered at all times, such as flight deck multi-function displays or the flight-management computer. But if, for example, the flight-management computer did require power cycling regularly, for whatever reason, this system would be required to have a means to do this other than using the circuit breakers. 3 Systems requiring power removal during normal operations should be designed so that power is removed from the system as closely as practical to the source of power instead of simply deactivating the outputs of the systems power supplies. 4 A separate, or integrated, power switch may be used to show compliance with [CS 25.1357(f)](#_DxCrossRefBm1709821143). If an integrated switch is used (that is, a switch that controls power to multiple aeroplane systems), then it must be shown that removing or resetting power for those multiple systems will not adversely affect safe flight. 5 A switch-rated circuit breaker can be used if it is shown to be appropriately rated for the number of switch cycles expected to be executed during the service life of the system or of the circuit breaker. [Amdt 25/5]