CS 25.933 Reversing systems

• ED Decision 2020/001/R found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

CS 25.933 Reversing systems ED Decision 2020/001/R (See [AMC 25.93](#_DxCrossRefBm1709821406)3) (a) For turbojet reversing systems: (1) Each system intended for ground operation only must be designed so that either: (i) The aeroplane can be shown to be capable of continued safe flight and landing during and after any thrust reversal in flight; or (ii) It can be demonstrated that any in-flight thrust reversal complies with [CS 25.1309(b).](#_DxCrossRefBm1709820691) (See [AMC 25.933(a)(1)](#_DxCrossRefBm1709821406)) (2) Each system intended for inflight use must be designed so that no unsafe condition will result during normal operation of the system, or from any failure (or reasonably likely combination of failures) of the reversing system, under any anticipated condition of operation of the aeroplane including ground operation. Failure of structural elements need not be considered if the probability of this kind of failure is extremely remote. (3) Each system must have means to prevent the engine from producing more than idle thrust when the reversing system malfunctions, except that it may produce any greater forward thrust that is shown to allow directional control to be maintained, with aerodynamic means alone, under the most critical reversing condition expected in operation. (b) For propeller reversing systems: (1) Each system intended for ground operation only must be designed so that no single failure (or reasonably likely combination of failures) or malfunction of the system will result in unwanted reverse thrust under any expected operating condition. Failure of structural elements need not be considered if this kind of failure is extremely remote. (2) Compliance with this paragraph may be shown by failure analysis or testing, or both, for propeller systems that allow propeller blades to move from the flight low-pitch position to a position that is substantially less than that at the normal flight low-pitch position. The analysis may include or be supported by the analysis made to show compliance with the requirements of CS-P 70 for the propeller and associated installation components. [Amdt 25/1] [Amdt 25/18] [Amdt 25/24]