--- title: "CS 25.301 – CS 25.581: SUBPART C – STRUCTURE (CS-25) — rule index · Avioverse" description: "CS 25.301 – CS 25.581, CS-25. (See AMC 25.301) (a) Strength requirements are specified in terms of limit loads (the maximum loads to be expected in…" url: "https://avioverse.aero/regulations/easa/cs-25/subpart-c" --- # SUBPART C – STRUCTURE Large Aeroplanes (CS-25) · CS-25 · CS 25.301 – CS 25.581 On this page 1. ## [CS 25.301 Loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-301) (See AMC 25.301) (a) Strength requirements are specified in terms of limit loads (the maximum loads to be expected in service) and ultimate loads (limit… 2. ## [AMC No. 1 to 25.301(b) Loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/amc-no-1-to-25-301-b-loads) The engine and its mounting structure are to be stressed to the loading cases for the aeroplane as a whole. 3. ## [AMC No. 2 to 25.301(b) Flight Load Validation](https://avioverse.aero/regulations/easa/cs-25/subpart-c/amc-no-2-to-25-301-b-flight-load-validation) PURPOSE This AMC sets forth an acceptable means, but not the only means, of demonstrating compliance with the provisions of CS-25 related to the… 4. ## [CS 25.302 Interaction of systems and structures](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-302) For aeroplanes equipped with systems that affect structural performance, either directly or as a result of a failure or malfunction, the influence of… 5. ## [CS 25.303 Factor of safety](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-303) Unless otherwise specified, a factor of safety of 1·5 must be applied to the prescribed limit load which are considered external loads on the structure. 6. ## [CS 25.305 Strength and deformation](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-305) The structure must be able to support limit loads without detrimental permanent deformation. 7. ## [CS 25.307 Proof of structure](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-307) (See AMC 25.307) (a) Compliance with the strength and deformation requirements of this Subpart must be shown for each critical loading condition. [AMC 25.307 Proof of structure](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-307#amc-25-307) 8. ## [CS 25.321 General](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-321) Flight load factors represent the ratio of the aerodynamic force component (acting normal to the assumed longitudinal axis of the aeroplane) to the… 9. ## [CS 25.331 Symmetric manoeuvring conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-331) (See AMC 25.331) (a) Procedure. For the analysis of the manoeuvring flight conditions specified in sub-paragraphs (b) and (c) of this paragraph, the… [AMC 25.331(c)(1) Maximum pitch control displacement at VA](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-331#amc-25-331-c-1) [AMC 25.331(c)(2) Checked manoeuvre between VA and VD](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-331#amc-25-331-c-2) 10. ## [CS 25.333 Flight manoeuvring envelope](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-333) (See AMC 25.333) (a) General. The strength requirements must be met at each combination of airspeed and load factor on and within the boundaries of the… [AMC 25.333(b) Manoeuvring envelope](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-333#amc-25-333-b) 11. ## [CS 25.335 Design airspeeds](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-335) (See AMC 25.335) The selected design airspeeds are equivalent airspeeds (EAS). [AMC 25.335(b)(1)(ii) Design Dive Speed - High speed protection function](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-335#amc-25-335-b-1-ii) [AMC 25.335(b)(2) Design Dive Speed](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-335#amc-25-335-b-2) 12. ## [CS 25.337 Limit manoeuvring load factors](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-337) (See AMC 25.337) (a) Except where limited by maximum (static) lift coefficients, the aeroplane is assumed to be subjected to symmetrical manoeuvres… [AMC 25.337 Limit manoeuvring load factors](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-337#amc-25-337) 13. ## [CS 25.341 Gust and turbulence loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-341) (See AMC 25.341) (a) Discrete Gust Design Criteria. The aeroplane is assumed to be subjected to symmetrical vertical and lateral gusts in level flight. [AMC 25.341 Gust and Continuous Turbulence Design Criteria (Acceptable Means of Compliance)](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-341#amc-25-341) 14. ## [CS 25.343 Design fuel and oil loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-343) The disposable load combinations must include each fuel and oil load in the range from zero fuel and oil to the selected maximum fuel and oil load. 15. ## [CS 25.345 High lift devices](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-345) (See AMC 25.345) (a) If wing-flaps are to be used during take-off, approach, or landing, at the design flap speeds established for these stages of flight… [AMC 25.345(a) High lift devices (Gust conditions)](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-345#amc-25-345-a) [AMC 25.345(c) High lift devices (Procedure flight condition)](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-345#amc-25-345-c) 16. ## [CS 25.349 Rolling conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-349) (See AMC 25.349) The aeroplane must be designed for loads resulting from the rolling conditions specified in sub-paragraphs (a) and (b) of this paragraph. [AMC 25.349(a) Rolling conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-349#amc-25-349-a) 17. ## [CS 25.351 Yaw manoeuvre conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-351) (see AMC 25.351) The aeroplane must be designed for loads resulting from the yaw manoeuvre conditions specified in subparagraphs (a) through (d) of this… [AMC 25.351 Yaw manoeuvre conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-351#amc-25-351) 18. ## [CS 25.353 Rudder control reversal conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-353) (See AMC 25.353) The aeroplane must be designed for loads, considered to be ultimate, resulting from the yaw manoeuvre conditions specified in… [AMC 25.353 Rudder control reversal conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-353#amc-25-353) 19. ## [CS 25.361 Engine and auxiliary power unit torque](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-361) (See AMC 25.361) (a) For engine installations: Each engine mount, pylon and adjacent supporting airframe structures must be designed for the effects of… [AMC 25.361 Engine and auxiliary power unit torque](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-361#amc-25-361) 20. ## [CS 25.362 Engine failure loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-362) (See AMC 25.362.) (a) For engine mounts, pylons and adjacent supporting airframe structure, an ultimate loading condition must be considered that… [AMC 25.362 Engine Failure Loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-362#amc-25-362) 21. ## [CS 25.363 Side load on engine and auxiliary power unit mounts](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-363) Each engine and auxiliary power unit mount and its supporting structure must be designed for a limit load factor in a lateral direction, for the side… 22. ## [CS 25.365 Pressurised compartment loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-365) (See AMC 25.365) For aeroplanes with one or more pressurised compartments the following apply: [AMC 25.365(e) Pressurised compartment loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-365#amc-25-365-e) 23. ## [CS 25.367 Unsymmetrical loads due to engine failure](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-367) The aeroplane must be designed for the unsymmetrical loads resulting from the failure of the critical engine. 24. ## [CS 25.371 Gyroscopic loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-371) The structure supporting any engine or auxiliary power unit must be designed for the loads, including gyroscopic loads, arising from the conditions… 25. ## [CS 25.373 Speed control devices](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-373) If speed control devices (such as spoilers and drag flaps) are installed for use in en-route conditions: 26. ## [CS 25.391 Control surface loads: general](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-391) The control surfaces must be designed for the limit loads resulting from the flight conditions in CS 25.331, CS 25.341(a) and (b), CS 25.349 and CS… 27. ## [CS 25.393 Loads parallel to hinge line](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-393) (See AMC 25.393) (a) Control surfaces and supporting hinge brackets must be designed for inertia loads acting parallel to the hinge line. [AMC 25.393(a) Loads parallel to hinge line](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-393#amc-25-393-a) 28. ## [CS 25.395 Control system](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-395) Longitudinal, lateral, directional and drag control systems and their supporting structures must be designed for loads corresponding to 125% of the… 29. ## [CS 25.397 Control system loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-397) General. The maximum and minimum pilot forces, specified in sub-paragraph (c) of this paragraph, are assumed to act at the appropriate control grips or… 30. ## [CS 25.399 Dual control system](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-399) Each dual control system must be designed for the pilots operating in opposition, using individual pilot forces not less than – (1) 0·75 times those… 31. ## [CS 25.405 Secondary control system](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-405) Secondary controls, such as wheel brake, spoiler, and tab controls, must be designed for the maximum forces that a pilot is likely to apply to those… 32. ## [CS 25.407 Trim tab effects](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-407) The effects of trim tabs on the control surface design conditions must be accounted for only where the surface loads are limited by maximum pilot effort. 33. ## [CS 25.409 Tabs](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-409) Trim tabs. Trim tabs must be designed to withstand loads arising from all likely combinations of tab setting, primary control position, and aeroplane… 34. ## [CS 25.415 Ground gust conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-415) (See AMC 25.415) (a) The flight control systems and surfaces must be designed for the limit loads generated when the aircraft is subjected to a… [AMC 25.415 Ground gust conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-415#amc-25-415) 35. ## [CS 25.427 Unsymmetrical loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-427) In designing the aeroplane for lateral gust, yaw manoeuvre and roll manoeuvre conditions, account must be taken of unsymmetrical loads on the empennage… 36. ## [CS 25.445 Outboard fins](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-445) When significant, the aerodynamic influence between auxiliary aerodynamic surfaces, such as outboard fins and winglets, and their supporting aerodynamic… 37. ## [CS 25.457 Wing-flaps](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-457) Wing flaps, their operating mechanisms, and their supporting structures must be designed for critical loads occurring in the conditions prescribed in CS… 38. ## [CS 25.459 Special devices](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-459) The loading for special devices using aero-dynamic surfaces (such as slots, slats and spoilers) must be determined from test data. 39. ## [CS 25.471 General](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-471) Loads and equilibrium. For limit ground loads – (1) Limit ground loads obtained under this Subpart are considered to be external forces applied to the… 40. ## [CS 25.473 Landing load conditions and assumptions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-473) (a)For the landing conditions specified in CS 25.479 to 25.485, the aeroplane is assumed to contact the ground: 41. ## [CS 25.477 Landing gear arrangement](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-477) CS 25.479 to 25.485 apply to aeroplanes with conventional arrangements of main and nose gears, or main and tail gears, when normal operating techniques… 42. ## [CS 25.479 Level landing conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-479) In the level attitude, the aeroplane is assumed to contact the ground at forward velocity components, ranging from VL1 to 1·25 VL2 parallel to the ground… 43. ## [CS 25.481 Tail-down landing conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-481) In the tail-down attitude, the aeroplane is assumed to contact the ground at forward velocity components, ranging from VL1 to VL2, parallel to the ground… 44. ## [CS 25.483 One-gear landing conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-483) For the one-gear landing conditions, the aeroplane is assumed to be in the level attitude and to contact the ground on one main landing gear, in… 45. ## [CS 25.485 Side load conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-485) In addition to CS 25.479(d)(2) the following conditions must be considered: 46. ## [CS 25.487 Rebound landing condition](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-487) The landing gear and its supporting structure must be investigated for the loads occurring during rebound of the aeroplane from the landing surface. 47. ## [CS 25.489 Ground handling conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-489) Unless otherwise prescribed, the landing gear and aeroplane structure must be investigated for the conditions in CS 25.491 to 25.509 with the aeroplane… 48. ## [CS 25.491 Taxi, take-off and landing roll](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-491) (See AMC 25.415) Within the range of appropriate ground speeds and approved weights, the aeroplane structure and landing gear are assumed to be subjected… [AMC 25.491 Taxy, take-off and landing roll](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-491#amc-25-491) [AMC 25.491 Taxy, take-off and landing roll - tables](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-491#amc-25-491-2) 49. ## [CS 25.493 Braked roll conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-493) An aeroplane with a tail wheel is assumed to be in the level attitude with the load on the main wheels, in accordance with Figure 6 of Appendix A. 50. ## [CS 25.495 Turning](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-495) In the static position, in accordance with Figure 7 of Appendix A, the aeroplane is assumed to execute a steady turn by nose gear steering, or by… 51. ## [CS 25.497 Tail-wheel yawing](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-497) A vertical ground reaction equal to the static load on the tail wheel, in combination with a side component of equal magnitude, is assumed. 52. ## [CS 25.499 Nose-wheel yaw and steering](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-499) A vertical load factor of 1·0 at the aeroplane centre of gravity, and a side component at the nose wheel ground contact equal to 0·8 of the vertical… 53. ## [CS 25.503 Pivoting](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-503) The aeroplane is assumed to pivot about one side of the main gear with the brakes on that side locked. 54. ## [CS 25.507 Reversed braking](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-507) The aeroplane must be in a three point static ground attitude. 55. ## [CS 25.509 Towing Loads](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-509) (See AMC 25.509) (a) The towing loads specified in sub-paragraph (d) of this paragraph must be considered separately. [AMC 25.509 Towbarless towing](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-509#amc-25-509) 56. ## [CS 25.511 Ground load: unsymmetrical loads on multiple-wheel units](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-511) General. Multiple-wheel landing gear units are assumed to be subjected to the limit ground loads prescribed in this Subpart under sub-paragraphs (b)… 57. ## [CS 25.519 Jacking and tie-down provisions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-519) General. The aeroplane must be designed to withstand the limit load conditions resulting from the static ground load conditions of sub-paragraph (b) of… 58. ## [CS 25.561 General](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-561) (See AMC 25.561.) (a) The aeroplane, although it may be damaged in emergency landing conditions on land or water, must be designed as prescribed in this… [AMC 25.561 General](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-561#amc-25-561) [AMC 25.561(b)(3) Commercial Accommodation Equipment](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-561#amc-25-561-b-3) [AMC 25.561(d) General](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-561#amc-25-561-d) 59. ## [CS 25.562 Emergency landing dynamic conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-562) (See AMC 25.562) (a) The seat and restraint system in the aeroplane must be designed as prescribed in this paragraph to protect each occupant during an… [AMC 25.562 Emergency landing dynamic conditions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-562#amc-25-562) 60. ## [CS 25.563 Structural ditching provisions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-563) (See AMC 25.563) If certification with ditching provisions is requested, those parts of the airframe structure that are necessary to maintain flotation… [AMC 25.563 Structural ditching provisions](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-563#amc-25-563) 61. ## [CS 25.571 Damage tolerance and fatigue evaluation of structure](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-571) (See AMC 25.571) (a) General. An evaluation of the strength, detail design, and fabrication must show that catastrophic failure due to fatigue… [AMC 25.571 Damage tolerance and fatigue evaluation of structure](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-571#amc-25-571) 62. ## [Appendix 1 Crack growth analysis and tests](https://avioverse.aero/regulations/easa/cs-25/subpart-c/appendix-1) Crack growth characteristics should be determined for each detail design point identified in accordance with 7(f) above. 63. ## [Appendix 2 Full-scale fatigue test evidence](https://avioverse.aero/regulations/easa/cs-25/subpart-c/appendix-2) Overview CS 25.571(b) requires that special consideration for widespread fatigue damage (WFD) be included where the design is such that this type of… 64. ## [Appendix 3 Methods for inspection threshold determination](https://avioverse.aero/regulations/easa/cs-25/subpart-c/appendix-3) Different approaches have been used to calculate inspection thresholds, although these are essentially variants of one of two methods, being: 65. ## [Appendix 4 Examples of changes that may require full-scale fatigue testing](https://avioverse.aero/regulations/easa/cs-25/subpart-c/appendix-4) The following are examples of types of modifications that may require full-scale fatigue testing: 66. ## [Appendix 5 PSE, FCS, and WFD-susceptible structure](https://avioverse.aero/regulations/easa/cs-25/subpart-c/appendix-5) Overview Four key terms used when showing compliance to the damage tolerance and fatigue requirements of CS-25 and EASA guidance for the continued… 67. ## [CS 25.581 Lightning protection](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-581) (See AMC 25.581) (a) The aeroplane must be protected against catastrophic effects from lightning. [AMC 25.581 Lightning protection](https://avioverse.aero/regulations/easa/cs-25/subpart-c/cs-25-581#amc-25-581) Consolidated from the EASA Easy Access Rules (revision 26 Jan 2023, extracted 13 Oct 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use. Share [LinkedIn](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Favioverse.aero%2Fregulations%2Feasa%2Fcs-25%2Fsubpart-c)[X](https://twitter.com/intent/tweet?url=https%3A%2F%2Favioverse.aero%2Fregulations%2Feasa%2Fcs-25%2Fsubpart-c\&text=SUBPART%20C%20%E2%80%93%20STRUCTURE%20%E2%80%94%20CS-25)