CS 25.143 General

ED Decision 2020/024/R

(a)     (See AMC 25.143(a) and (b)) The aeroplane must be safely controllable and manoeuvrable during:

(1)     take-off;

(2)     climb;

(3)     level flight;

(4)     descent;

(5)     approach and go-around; and

(6)     approach and landing.

(b)     (See AMC 25.143(a) and (b)) It must be possible to make a smooth transition from one flight condition to any other flight condition without exceptional piloting skill, alertness, or strength, and without danger of exceeding the aeroplane limit-load factor under any probable operating conditions, including:

(1)     The sudden failure of the critical engine; (See AMC 25.143(b)(1).)

(2)     For aeroplanes with three or more engines, the sudden failure of the second critical engine when the aeroplane is in the en-route, approach, or landing configuration and is trimmed with the critical engine inoperative; and

(3)     Configuration changes, including deployment or retraction of deceleration devices; and

(4)     Go-around manoeuvres with all engines operating. The assessment must include, in addition to controllability and manoeuvrability aspects, the flight crew workload and the risk of a somatogravic illusion. (See AMC 25.143(b)(4))

(c)      The aeroplane must be shown to be safely controllable and manoeuvrable with the most critical ice accretion(s) appropriate to the phase of flight as defined in appendices C and O, as applicable, in accordance with CS 25.21(g), and with the critical engine inoperative and its propeller (if applicable) in the minimum drag position:

(1)     At the minimum V₂ for take-off;

(2)     During an approach and go-around; and

(3)     During an approach and landing.

(d)     The following table prescribes, for conventional wheel type controls, the maximum control forces permitted during the testing required by sub-paragraphs (a) through (c) of this paragraph. (See AMC 25.143(d)):

(e)     Approved operating procedures or conventional operating practices must be followed when demonstrating compliance with the control force limitations for short term application that are prescribed in sub-paragraph (d) of this paragraph. The aeroplane must be in trim, or as near to being in trim as practical, in the immediately preceding steady flight condition. For the take-off condition, the aeroplane must be trimmed according to the approved operating procedures.

(f)      When demonstrating compliance with the control force limitations for long term application that are prescribed in sub-paragraph (d) of this paragraph, the aeroplane must be in trim, or as near to being in trim as practical.

(g)     When manoeuvring at a constant airspeed or Mach number (up to V_FC/M_FC), the stick forces and the gradient of the stick force versus manoeuvring load factor must lie within satisfactory limits. The stick forces must not be so great as to make excessive demands on the pilot’s strength when manoeuvring the aeroplane (see AMC No. 1 to CS 25.143(g)), and must not be so low that the aeroplane can easily be overstressed inadvertently. Changes of gradient that occur with changes of load factor must not cause undue difficulty in maintaining control of the aeroplane, and local gradients must not be so low as to result in a danger of over-controlling. (See AMC No. 2 to CS 25.143(g)).

(h)     (See AMC 25.143(h)). The manoeuvring capabilities in a constant speed coordinated turn at forward centre of gravity, as specified in the following table, must be free of stall warning or other characteristics that might interfere with normal manoeuvring.

(1)     A combination of weight, altitude and temperature (WAT) such that the thrust or power setting produces the minimum climb gradient specified in CS 25.121 for the flight condition.

(2)     Airspeed approved for all-engines-operating initial climb.

(3)     That thrust or power setting which, in the event of failure of the critical engine and without any crew action to adjust the thrust or power of the remaining engines, would result in the thrust or power specified for the take-off condition at V₂, or any lesser thrust or power setting that is used for all-engines-operating initial climb procedures.

(i)      When demonstrating compliance with CS 25.143 in icing conditions -

(1)     Controllability must be demonstrated with the most critical of the ice accretion(s) for the particular phase of flight as defined in Appendices C and O, as applicable, in accordance with CS 25.21(g).

(2)     It must be shown that a push force is required throughout a pushover manoeuvre down to a zero g load factor, or the lowest load factor obtainable if limited by elevator power or other design characteristic of the flight control system. It must be possible to promptly recover from the manoeuvre without exceeding a pull control force of 222 N. (50 lbf); and

(3)     Any changes in force that the pilot must apply to the pitch control to maintain speed with increasing sideslip angle must be steadily increasing with no force reversals, unless the change in control force is gradual and easily controllable by the pilot without using exceptional piloting skill, alertness, or strength.

(j)      For flight in icing conditions before the ice protection system has been activated and is performing its intended function, it must be demonstrated in flight with the most critical of the ice accretion(s) defined in appendix C, part II(e), and Appendix O, part II(d), as applicable, in accordance with CS 25.21(g), that:

(1)     The aeroplane is controllable in a pull-up manoeuvre up to 1.5 g load factor; and

(2)     There is no pitch control force reversal during a pushover manoeuvre down to 0.5 g load factor.

(k)     Side stick controllers

In lieu of the maximum control forces provided in CS 25.143(d) for pitch and roll, and in lieu of specific pitch force requirements of CS 25.145(b) and CS 25.175(d), it must be shown that the temporary and maximum prolonged force levels for side stick controllers are suitable for all expected operating conditions and configurations, whether normal or non-normal.

It must be shown by flight tests that turbulence does not produce unsuitable pilot-in-the-loop control problems when considering precision path control/tasks.

(l)      Electronic flight control systems

For electronic flight control systems (EFCS) which embody a normal load factor limiting system and in the absence of aerodynamic limitation (lift capability at maximum angle of attack),

(1)     The positive limiting load factor must not be less than:

(i)      2.5 g with the EFCS functioning in its normal mode and with the high-lift devices retracted up to V_MO/M_MO. The positive limiting load factor may be gradually reduced down to 2.25 g above V_MO/M_MO.;

(ii)     2.0 g with the EFCS functioning in its normal mode and with the high-lift devices extended.

(2)     The negative limiting load factor must be equal to or more negative than:

(i)      -1.0 g with the EFCS functioning in its normal mode and with the high-lift devices retracted;

(ii)     0 g with the EFCS functioning in its normal mode and with the high-lift devices extended.

(3)     The maximum reachable positive load factor wings level may be limited by flight control system characteristics or flight envelope protections (other than load factor limitation), provided that:

(i)       the required values are readily achievable in turn, and

(ii)     wings level pitch up responsiveness is satisfactory.

(4)     The maximum reachable negative load factor may be limited by flight control system characteristics or flight envelope protections (other than load factor limitation), provided that:

(i)      pitch down responsiveness is satisfactory, and

(ii)     from level flight, 0 g is readily achievable, or, at least, a trajectory change of 5 degrees per second is readily achievable at operational speeds (from V_LS to Max speed – 10 kt. V_LS is the lowest speed that the crew may fly with auto thrust or auto pilot engaged. Max speed – 10 kt) is intended to cover typical margin from V_MO/M_MO to cruise speeds and typical margin from V_FE to standard speed in high-lift configurations.

(5)     Compliance demonstrations with the above requirements may be performed without ice accretion on the airframe.

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