SUBPART C – STRUCTURE
Large Aeroplanes (CS-25) · CS-25 · CS 25.301 – CS 25.581
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CS 25.301 Loads
(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…
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.
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…
CS 25.302 Interaction of systems and structures
For aeroplanes equipped with systems that affect structural performance, either directly or as a result of a failure or malfunction, the influence of…
CS 25.303 Factor of safety
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.
CS 25.305 Strength and deformation
The structure must be able to support limit loads without detrimental permanent deformation.
CS 25.307 Proof of structure
(See AMC 25.307) (a) Compliance with the strength and deformation requirements of this Subpart must be shown for each critical loading condition.
CS 25.321 General
Flight load factors represent the ratio of the aerodynamic force component (acting normal to the assumed longitudinal axis of the aeroplane) to the…
CS 25.331 Symmetric manoeuvring conditions
(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…
CS 25.333 Flight manoeuvring envelope
(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…
CS 25.335 Design airspeeds
(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
CS 25.337 Limit manoeuvring load factors
(See AMC 25.337) (a) Except where limited by maximum (static) lift coefficients, the aeroplane is assumed to be subjected to symmetrical manoeuvres…
CS 25.341 Gust and turbulence loads
(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)
CS 25.343 Design fuel and oil loads
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.
CS 25.345 High lift devices
(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)
AMC 25.345(c) High lift devices (Procedure flight condition)
CS 25.349 Rolling conditions
(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.
CS 25.351 Yaw manoeuvre conditions
(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…
CS 25.353 Rudder control reversal conditions
(See AMC 25.353) The aeroplane must be designed for loads, considered to be ultimate, resulting from the yaw manoeuvre conditions specified in…
CS 25.361 Engine and auxiliary power unit torque
(See AMC 25.361) (a) For engine installations: Each engine mount, pylon and adjacent supporting airframe structures must be designed for the effects of…
CS 25.362 Engine failure loads
(See AMC 25.362.) (a) For engine mounts, pylons and adjacent supporting airframe structure, an ultimate loading condition must be considered that…
CS 25.363 Side load on engine and auxiliary power unit mounts
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…
CS 25.365 Pressurised compartment loads
(See AMC 25.365) For aeroplanes with one or more pressurised compartments the following apply:
CS 25.367 Unsymmetrical loads due to engine failure
The aeroplane must be designed for the unsymmetrical loads resulting from the failure of the critical engine.
CS 25.371 Gyroscopic loads
The structure supporting any engine or auxiliary power unit must be designed for the loads, including gyroscopic loads, arising from the conditions…
CS 25.373 Speed control devices
If speed control devices (such as spoilers and drag flaps) are installed for use in en-route conditions:
CS 25.391 Control surface loads: general
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…
CS 25.393 Loads parallel to hinge line
(See AMC 25.393) (a) Control surfaces and supporting hinge brackets must be designed for inertia loads acting parallel to the hinge line.
CS 25.395 Control system
Longitudinal, lateral, directional and drag control systems and their supporting structures must be designed for loads corresponding to 125% of the…
CS 25.397 Control system loads
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…
CS 25.399 Dual control system
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…
CS 25.405 Secondary control system
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…
CS 25.407 Trim tab effects
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.
CS 25.409 Tabs
Trim tabs. Trim tabs must be designed to withstand loads arising from all likely combinations of tab setting, primary control position, and aeroplane…
CS 25.415 Ground gust conditions
(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…
CS 25.427 Unsymmetrical loads
In designing the aeroplane for lateral gust, yaw manoeuvre and roll manoeuvre conditions, account must be taken of unsymmetrical loads on the empennage…
CS 25.445 Outboard fins
When significant, the aerodynamic influence between auxiliary aerodynamic surfaces, such as outboard fins and winglets, and their supporting aerodynamic…
CS 25.457 Wing-flaps
Wing flaps, their operating mechanisms, and their supporting structures must be designed for critical loads occurring in the conditions prescribed in CS…
CS 25.459 Special devices
The loading for special devices using aero-dynamic surfaces (such as slots, slats and spoilers) must be determined from test data.
CS 25.471 General
Loads and equilibrium. For limit ground loads – (1) Limit ground loads obtained under this Subpart are considered to be external forces applied to the…
CS 25.473 Landing load conditions and assumptions
(a)For the landing conditions specified in CS 25.479 to 25.485, the aeroplane is assumed to contact the ground:
CS 25.477 Landing gear arrangement
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…
CS 25.479 Level landing conditions
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…
CS 25.481 Tail-down landing conditions
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…
CS 25.483 One-gear landing conditions
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…
CS 25.485 Side load conditions
In addition to CS 25.479(d)(2) the following conditions must be considered:
CS 25.487 Rebound landing condition
The landing gear and its supporting structure must be investigated for the loads occurring during rebound of the aeroplane from the landing surface.
CS 25.489 Ground handling conditions
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…
CS 25.491 Taxi, take-off and landing roll
(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…
CS 25.493 Braked roll conditions
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.
CS 25.495 Turning
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…
CS 25.497 Tail-wheel yawing
A vertical ground reaction equal to the static load on the tail wheel, in combination with a side component of equal magnitude, is assumed.
CS 25.499 Nose-wheel yaw and steering
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…
CS 25.503 Pivoting
The aeroplane is assumed to pivot about one side of the main gear with the brakes on that side locked.
CS 25.507 Reversed braking
The aeroplane must be in a three point static ground attitude.
CS 25.509 Towing Loads
(See AMC 25.509) (a) The towing loads specified in sub-paragraph (d) of this paragraph must be considered separately.
CS 25.511 Ground load: unsymmetrical loads on multiple-wheel units
General. Multiple-wheel landing gear units are assumed to be subjected to the limit ground loads prescribed in this Subpart under sub-paragraphs (b)…
CS 25.519 Jacking and tie-down provisions
General. The aeroplane must be designed to withstand the limit load conditions resulting from the static ground load conditions of sub-paragraph (b) of…
CS 25.561 General
(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…
CS 25.562 Emergency landing dynamic conditions
(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…
CS 25.563 Structural ditching provisions
Structural strength considerations of ditching provisions must be in accordance with CS 25.801(e).
CS 25.571 Damage tolerance and fatigue evaluation of structure
(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
Appendix 1 Crack growth analysis and tests
Crack growth characteristics should be determined for each detail design point identified in accordance with 7(f) above.
Appendix 2 Full-scale fatigue test evidence
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…
Appendix 3 Methods for inspection threshold determination
Different approaches have been used to calculate inspection thresholds, although these are essentially variants of one of two methods, being:
Appendix 4 Examples of changes that may require full-scale fatigue testing
The following are examples of types of modifications that may require full-scale fatigue testing:
Appendix 5 PSE, FCS, and WFD-susceptible structure
Overview Four key terms used when showing compliance to the damage tolerance and fatigue requirements of CS-25 and EASA guidance for the continued…
CS 25.581 Lightning protection
(See AMC 25.581) (a) The aeroplane must be protected against catastrophic effects from lightning.
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