CS 25.21 Proof of compliance

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

CS 25.21 Proof of compliance ED Decision 2016/010/R (a) Each requirement of this Subpart must be met at each appropriate combination of weight and centre of gravity within the range of loading conditions for which certification is requested. This must be shown – (1) By tests upon an aeroplane of the type for which certification is requested, or by calculations based on, and equal in accuracy to, the results of testing; and (2) By systematic investigation of each probable combination of weight and centre of gravity, if compliance cannot be reasonably inferred from combinations investigated. (b) Reserved (c) The controllability, stability, trim, and stalling characteristics of the aeroplane must be shown for each altitude up to the maximum expected in operation. (d) Parameters critical for the test being conducted, such as weight, loading (centre of gravity and inertia), airspeed, power, and wind, must be maintained within acceptable tolerances of the critical values during flight testing. (See [AMC 25.21(d)](#_DxCrossRefBm1709820688)) (e) If compliance with the flight characteristics requirements is dependent upon a stability augmentation system or upon any other automatic or power-operated system, compliance must be shown with [CS 25.671](#_DxCrossRefBm1709820687) and [25.672](#_DxCrossRefBm1709820686). (f) In meeting the requirements of [CS 25.105(d)](#_DxCrossRefBm1709820679), [25.125](#_DxCrossRefBm1709820685), [25.233](#_DxCrossRefBm1709820684) and [25.237](#_DxCrossRefBm1709820683), the wind velocity must be measured at a height of 10 metres above the surface, or corrected for the difference between the height at which the wind velocity is measured and the 10-metre height. (g) The requirements of this subpart associated with icing conditions apply only if the applicant is seeking certification for flight in icing conditions. (See [AMC 25.21(g)](#_DxCrossRefBm1709820682)) (1) Each requirement of this subpart, except [CS 25.121(a)](#_DxCrossRefBm1709820672), [25.123(c)](#_DxCrossRefBm1709820671), [25.143(b)(1) and (b)(2)](#_DxCrossRefBm1709820670), [25.149](#_DxCrossRefBm1709820669), [25.201(c)(2)](#_DxCrossRefBm1709820668), and [25.251(b) through (e)](#_DxCrossRefBm1709820667), must be met in the icing conditions specified in Appendix C. [CS 25.207(c) and (d)](#_DxCrossRefBm1709820666) must be met in the landing configuration in the icing conditions specified in [Appendix C](#_DxCrossRefBm1709820681) but need not be met for other configurations. Compliance must be shown using the ice accretions defined in [part II of Appendix C](#_DxCrossRefBm1709820680), assuming normal operation of the aeroplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Aeroplane Flight Manual. (2) If the applicant does not seek certification for flight in all icing conditions defined in [Appendix O](#_DxCrossRefBm1709820665), each requirement of this subpart, except [CS 25.105](#_DxCrossRefBm1709820679), [25.107](#_DxCrossRefBm1709820678), [25.109](#_DxCrossRefBm1709820677), [25.111](#_DxCrossRefBm1709820676), [25.113](#_DxCrossRefBm1709820675), [25.115](#_DxCrossRefBm1709820674), [25.121](#_DxCrossRefBm1709820672), [25.123](#_DxCrossRefBm1709820671), [25.143(b)(1), (b)(2), and (c)(1)](#_DxCrossRefBm1709820670), [25.149](#_DxCrossRefBm1709820669), [25.201(c)(2)](#_DxCrossRefBm1709820668), [25.207(c), (d) and (e)(1)](#_DxCrossRefBm1709820666), and [25.251(b) through (e)](#_DxCrossRefBm1709820667), must be met in the [Appendix O](#_DxCrossRefBm1709820665) icing conditions for which certification is not sought in order to allow a safe exit from those conditions. Compliance must be shown using the iceaccretions defined in [part II](#_DxCrossRefBm1709820664), paragraphs (b) and (d) of Appendix O, assuming normal operation of the aeroplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Aeroplane Flight Manual. If applicable, a comparative analysis (refer to [CS 25.1420](#_DxCrossRefBm1709820673)) may be used to show compliance as an alternative to using the ice accretions defined in [part II](#_DxCrossRefBm1709820664), paragraphs (b) and (d) of Appendix O. (3) If the applicant seeks certification for flight in any portion of the icing conditions of Appendix O, each requirement of this subpart, except paragraphs [CS 25.121(a)](#_DxCrossRefBm1709820672), [25.123(c)](#_DxCrossRefBm1709820671), [25.143(b)(1) and (b)(2)](#_DxCrossRefBm1709820670), [25.149](#_DxCrossRefBm1709820669), [25.201(c)(2)](#_DxCrossRefBm1709820668), and [25.251(b) through (e)](#_DxCrossRefBm1709820667), must be met in the Appendix O icing conditions for which certification is sought. [CS 25.207(c) and (d)](#_DxCrossRefBm1709820666) must be met in the landing configuration in the icing conditions specified in [Appendix O](#_DxCrossRefBm1709820665) for which certification is sought but need not be met for other configurations. Compliance must be shown using the ice accretions defined in part II, paragraphs (c) and (d) of [Appendix O](#_DxCrossRefBm1709820665), assuming normal operation of the aeroplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Aeroplane Flight Manual. If applicable, a comparative analysis (refer to CS 25.1420) may be used to show compliance as an alternative to using the ice accretions defined in [part II](#_DxCrossRefBm1709820664), paragraphs (c) and (d) of Appendix O. (4) No changes in the load distribution limits of [CS 25.23](#_DxCrossRefBm1709820663), the weight limits of [CS 25.25](#_DxCrossRefBm1709820662) (except where limited by performance requirements of this subpart), and the centre of gravity limits of [CS 25.27](#_DxCrossRefBm1709820661), from those for non-icing conditions, are allowed for flight in icing conditions or with ice accretion. [Amdt 25/3] [Amdt 25/6] [Amdt 25/16] [Amdt 25/17] [Amdt 25/18]