AMC 25.1333(b) Instruments systems

• ED Decision 2003/2/RM found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

AMC 25.1333(b) Instruments systems ED Decision 2003/2/RM 1. *Attitude displays systems.* If three displays are used to show compliance with [CS 25.1333(b)](#_DxCrossRefBm1709821584), the reliability and independence of those displays should be confirmed by a suitable assessment in accordance with [CS 25.1309](#_DxCrossRefBm1709820691). Each display should have independent sensors and power supplies. If a total failure of the generated electrical power causes the loss of both main instruments, the power supply to the third (standby) attitude indicator and its appropriate lighting should be such that the display is usable from each pilot’s station for a time duration in accordance with [AMC 25.1351(d)](#_DxCrossRefBm1709821648). Note: the time for which the display remains usable will be stated in the Aeroplane Flight Manual (AFM). 2. *Airspeed, altitude, and direction display systems.* The reliability and independence of the displays used to show compliance with CS 25.1333(b) should be sufficient to ensure continued safe flight and landing appropriate to the intended operation of the aeroplane. Historically, “sufficient information” to control attitude, airspeed, altitude, and direction has been provided by specific indicators of the state of each parameter. However, since control is considered to be the ability to change or maintain a given parameter to a desired value, it is assumed that these parameters will be available without flight crew action. There may be alternate parameters in the cockpit that provide equivalent means to control attitude, airspeed, altitude and direction, without displaying those parameters directly (for example, without display of standby airspeed, by using a suitable angle-of-attack display). For these alternate cases, compliance to CS 25.1333(b) must be shown by analysis and flight test.