CS 25.1420 Supercooled large drop icing conditions

• ED Decision 2016/010/R found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

CS 25.1420 Supercooled large drop icing conditions ED Decision 2016/010/R (see [AMC 25.1420](#_DxCrossRefBm1709820703)) (a) If certification for flight in icing conditions is sought, in addition to the requirements of [CS 25.1419](#_DxCrossRefBm1709821102), the aeroplane must be capable of operating in accordance with sub-paragraphs (a)(1), (a)(2), or (a)(3) of this paragraph. (1) Operating safely after encountering the icing conditions defined in Appendix O: (i) The aeroplane must have a means to detect that it is operating in Appendix O icing conditions; and (ii) Following detection of [Appendix O](#_DxCrossRefBm1709820665) icing conditions, the aeroplane must be capable of operating safely while exiting all icing conditions. (2) Operating safely in a portion of the icing conditions defined in [Appendix O](#_DxCrossRefBm1709820665) as selected by the applicant. (i) The aeroplane must have a means to detect that it is operating in conditions that exceed the selected portion of [Appendix O](#_DxCrossRefBm1709820665) icing conditions; and (ii) Following detection, the aeroplane must be capable of operating safely while exiting all icing conditions. (3) Operating safely in the icing conditions defined in [Appendix O](#_DxCrossRefBm1709820665). (b) To establish that the aeroplane can operate safely as required in sub-paragraph (a) of this paragraph, an applicant must show through analysis that the ice protection for the various components of the aeroplane is adequate, taking into account the various aeroplane operational configurations. To verify the analysis, one, or more as found necessary, of the following methods must be used: (1) Laboratory dry air or simulated icing tests, or a combination of both, of the components or models of the components. (2) Laboratory dry air or simulated icing tests, or a combination of both, of models of the aeroplane. (3) Flight tests of the aeroplane or its components in simulated icing conditions, measured as necessary to support the analysis. (4) Flight tests of the aeroplane with simulated ice shapes. (5) Flight tests of the aeroplane in natural icing conditions, measured as necessary to support the analysis. (c) For an aeroplane certified in accordance with sub-paragraph (a)(2) or (a)(3) of this paragraph, the requirements of [CS 25.1419(e), (f), (g), and (h)](#_DxCrossRefBm1709821102) must be met for the icing conditions defined in Appendix O in which the aeroplane is certified to operate. (d) A comparative analysis may be used as an alternative to CS 25.1420(b) to establish that the aeroplane can operate safely as required in CS 25.1420(a), and as an alternative to CS 25.1420(c) regarding methods of icing detection and activation of the airframe ice protection system. In this case, tests may not be required (see AMC 25.1420(f)). [Amdt 25/16] [Amdt 25/18]