CS 25.1333 Instrument systems — CS-25

IRImplementing rule

CS 25.1333Instrument systems

(See AMC 25.1333)

(a)For systems that operate the instruments required by CS 25.1303(b), which are located at each pilot’s station, means must be provided to connect the required instruments at the first pilot’s station to operating systems, which are independent of the operating systems at other flight crew stations, or other equipment.

(b)Equipment, systems, and installations must be designed so that sufficient information is available to assure control of the aeroplane in airspeed, altitude, direction and attitude by one of the pilots without additional flight crew action after any single failure or combination of failures that is not assessed to be extremely improbable (see AMC 25.1333(b)); and

(c)Additional instruments, systems, or equipment may not be connected to the operating systems for the instruments required by CS 25.1303(b), unless provisions are made to ensure the continued normal functioning of the required instruments in the event of any malfunction of the additional instruments, systems, or equipment which is not shown to be extremely improbable.

[Amdt 25/18]

IR · CS 25.1333 — CS-25 · ED Decision 2016/010/R · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

AMCAcceptable means of compliance

AMC 25.1333(b)Instruments systems

Show the text

1.Attitude displays systems. If three displays are used to show compliance with CS 25.1333(b), the reliability and independence of those displays should be confirmed by a suitable assessment in accordance with CS 25.1309. 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). 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.

AMC · AMC 25.1333(b) — CS-25 · ED Decision 2003/2/RM · CS-25 Easy Access Rules · EAR revision 26 Jan 2023