CS 25.121 Climb: one-engine-inoperative

• ED Decision 2015/008/R found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

CS 25.121 Climb: one-engine-inoperative ED Decision 2015/008/R (See [AMC 25.121](#_DxCrossRefBm1709820781)) (a) *Take-off; landing gear extended.* (See [AMC 25.121(a)](#_DxCrossRefBm1709820783).) In the critical take-off configuration existing along the flight path (between the points at which the aeroplane reaches VLOF and at which the landing gear is fully retracted) and in the configuration used in [CS 25.111](#_DxCrossRefBm1709820676) but without ground effect, the steady gradient of climb must be positive for two-engined aeroplanes, and not less than 0·3% for three-engined aeroplanes or 0·5% for fourengined aeroplanes, at VLOF and with – (1) The critical engine inoperative and the remaining engines at the power or thrust available when retraction of the landing gear is begun in accordance with CS 25.111 unless there is a more critical power operating condition existing later along the flight path but before the point at which the landing gear is fully retracted (see [AMC 25.121(a)(1)](#_DxCrossRefBm1709820782)); and (2) The weight equal to the weight existing when retraction of the landing gear is begun determined under CS 25.111. (b) *Take-off; landing gear retracted.* In the take-off configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in CS 25.111 but without ground effect, (1) the steady gradient of climb may not be less than 2·4% for two-engined aeroplanes, 2·7% for three-engined aeroplanes and 3·0% for four-engined aeroplanes, at V2 with – (i) The critical engine inoperative, the remaining engines at the take-off power or thrust available at the time the landing gear is fully retracted, determined under CS 25.111, unless there is a more critical power operating condition existing later along the flight path but before the point where the aeroplane reaches a height of 122 m (400 ft) above the take-off surface (see [AMC 25.121(b)(1)(i)](#_DxCrossRefBm1709820781)) ; and (ii) The weight equal to the weight existing when the aeroplane’s landing gear is fully retracted, determined under CS 25.111. (2) The requirements of sub-paragraph (b)(1) of this paragraph must be met: (i) In non-icing conditions; and (ii) In icing conditions with the most critical of the “Take-off Ice” accretion(s) defined in Appendices C and O, as applicable, in accordance with [CS 25.21(g)](#_DxCrossRefBm1709820660), if in the configuration used to show compliance with [CS 25.121(b)](#_DxCrossRefBm1709820672) with this “Take-off Ice” accretion: (A) The stall speed at maximum take-off weight exceeds that in non-icing conditions by more than the greater of 5.6 km/h (3 knots) CAS or 3% of VSR; or (B) The degradation of the gradient of climb determined in accordance with CS 25.121(b) is greater than one-half of the applicable actual-to-net take-off flight path gradient reduction defined in [CS 25.115(b)](#_DxCrossRefBm1709820674). (c) *Final take-off.* In the en-route configuration at the end of the take-off path determined in accordance with CS 25.111: (1) the steady gradient of climb may not be less than 1·2% for two-engined aeroplanes, 1·5% for three-engined aeroplanes, and 1·7% for four-engined aeroplanes, at VFTO and with – (i) The critical engine inoperative and the remaining engines at the available maximum continuous power or thrust; and (ii) The weight equal to the weight existing at the end of the take-off path, determined under CS 25.111. (2) The requirements of sub-paragraph (c)(1) of this paragraph must be met: (i) In non-icing conditions; and (ii) In icing conditions with themost critical of the “Final Take-off Ice” accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), if in the configuration used to show compliance with CS 25.121(b) with this “Take-off Ice” accretion: (A) The stall speed at maximum take-off weight exceeds that in non-icing conditions by more than the greater of 5.6 km/h (3 knots) CAS or 3% of VSR; or (B) The degradation of the gradient of climb determined in accordance with CS 25.121(b) is greater than one-half of the applicable actual-to-net take-off flight path gradient reduction defined in CS 25.115(b). (d) *Approach.* In a configuration corresponding to the normal all-engines-operating procedure in which VSR for this configuration does not exceed 110% of the VSR for the related all-engines-operating landing configuration: (1) steady gradient of climb may not be less than 2·1% for two-engined aeroplanes, 2·4% for three-engined aeroplanes and 2·7% for four-engined aeroplanes, with – (i) The critical engine inoperative, the remaining engines at the go-around power or thrust setting; (ii) The maximum landing weight; (iii) A climb speed established in connection with normal landing procedures, but not more than 1·4 VSR; and (iv) Landing gear retracted. (2) The requirements of sub-paragraph (d)(1) of this paragraph must be met: (i) In non-icing conditions; and (ii) In icing conditions with the most critical of the Approach Ice accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g). The climb speed selected for non-icing conditions may be used if the climb speed for icing conditions, computed in accordance with sub-paragraph (d)(1)(iii) of this paragraph, does not exceed that for non-icing conditions by more than the greater of 5.6 km/h (3 knots) CAS or 3%. [Amdt 25/3] [Amdt 25/16]