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CS 25.207 Stall warning

Large Aeroplanes (CS-25) · CS-25 · EAR revision 26 Jan 2023

IRImplementing rule

CS 25.207Stall warning

(a)Stall warning with sufficient margin to prevent inadvertent stalling with the flaps and landing gear in any normal position must be clear and distinctive to the pilot in straight and turning flight.

(b)The warning must be furnished either through the inherent aerodynamic qualities of the aeroplane or by a device that will give clearly distinguishable indications under expected conditions of flight. However, a visual stall warning device that requires the attention of the crew within the cockpit is not acceptable by itself. If a warning device is used, it must provide a warning in each of the aeroplane configurations prescribed in sub-paragraph (a) of this paragraph at the speed prescribed in sub-paragraphs (c) and (d) of this paragraph. Except for the stall warning prescribed in subparagraph (h)(3)(ii) of this paragraph, the stall warning for flight in icing conditions must be provided by the same means as the stall warning for flight in non-icing conditions. (See AMC 25.207(b).)

(c)When the speed is reduced at rates not exceeding 0.5 m/s2 (one knot per second), stall warning must begin, in each normal configuration, at a speed, VSW, exceeding the speed at which the stall is identified in accordance with CS 25.201(d) by not less than 9.3 km/h (five knots) or five percent CAS, whichever is greater. Once initiated, stall warning must continue until the angle of attack is reduced to approximately that at which stall warning began. (See AMC 25.207(c) and (d)).

(d)In addition to the requirement of subparagraph(c) of this paragraph, when the speed is reduced at rates not exceeding 0.5 m/s2 (one knot per second), in straight flight with engines idling and at the centre-of-gravity position specified in CS 25.103(b)(5), VSW, in each normal configuration, must exceed VSR by not less than 5.6 km/h (three knots) or three percent CAS, whichever is greater. (See AMC 25.207(c) and (d)).

(e)In icing conditions, the stall warning margin in straight and turning flight must be sufficient to allow the pilot to prevent stalling (as defined in CS 25.201(d)) when the pilot starts a recovery manoeuvre not less than three seconds after the onset of stall warning. When demonstrating compliance with this paragraph, the pilot must perform the recovery manoeuvre in the same way as for the airplane in non-icing conditions. Compliance with this requirement must be demonstrated in flight with the speed reduced at rates not exceeding 0.5 m/sec2 (one knot per second), with –

(1)The most critical of the take-off ice and final take-off ice accretions defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), for each configuration used in the take-off phase of flight;

(2)The most critical of the en route ice accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), for the en route configuration;

(3)The most critical of the holding ice accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), for the holding configuration(s);

(4)The most critical of the approach ice accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), for the approach configuration(s); and

(5)The most critical of the landing ice accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), for the landing and go-around configuration(s).

(f)The stall warning margin must be sufficient in both non-icing and icing conditions to allow the pilot to prevent stalling when the pilot starts a recovery manoeuvre not less than one second after the onset of stall warning in slowdown turns with at least 1.5g load factor normal to the flight path and airspeed deceleration rates of at least 1 m/sec2 (2 knots per second), When demonstrating compliance with this paragraph for icing conditions, the pilot must perform the recovery manoeuvre in the same way as for the airplane in non-icing conditions. Compliance with this requirement must be demonstrated in flight with –

(1)The flaps and landing gear in any normal position;

(2)The aeroplane trimmed for straight flight at a speed of 1.3 VSR; and

(3)The power or thrust necessary to maintain level flight at 1.3 VSR.

(g)Stall warning must also be provided in each abnormal configuration of the high lift devices that is likely to be used in flight following system failures (including all configurations covered by Aeroplane Flight Manual procedures).

(h)The following stall warning margin is required for flight in icing conditions before the ice protection system has been activated and is performing its intended function. Compliance must be shown using 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). The stall warning margin in straight and turning flight must be sufficient to allow the pilot to prevent stalling without encountering any adverse flight characteristics when:

(1)The speed is reduced at rates not exceeding 0.5 m/sec² (one knot per second);

(2)The pilot performs the recovery manoeuvre in the same way as for flight in non-icing conditions; and

(3)The recovery manoeuvre is started no earlier than:

(i)One second after the onset of stall warning if stall warning is provided by the same means as for flight in non-icing conditions; or

(ii)Three seconds after the onset of stall warning if stall warning is provided by a different means than for flight in non-icing conditions.

(i)In showing compliance with subparagraph (h) of this paragraph, if stall warning is provided by a different means in icing conditions than for non-icing conditions, compliance with CS 25.203 must be shown using the accretion defined in appendix C, part II(e). Compliance with this requirement must be shown using the demonstration prescribed by CS 25.201, except that the deceleration rates of CS 25.201(c)(2) need not be demonstrated.

[Amdt 25/3]

[Amdt 25/7]

[Amdt 25/16]

[Amdt 25/18]

IR · CS 25.207 — CS-25 · ED Decision 2016/010/R · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

AMCAcceptable means of compliance

AMC 25.207(b)Stall warning

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1 A warning which is clear and distinctive to the pilot is one which cannot be misinterpreted or mistaken for any other warning, and which, without being unduly alarming, impresses itself upon the pilot and captures his attention regardless of what other tasks and activities are occupying his attention and commanding his concentration. Where stall warning is to be provided by artificial means, a stick shaker device producing both a tactile and an audible warning is an Acceptable Means of Compliance. 2 Where stall warning is provided by means of a device, compliance with the requirement of CS 25.21(e) should be established by ensuring that the device has a high degree of reliability. One means of complying with this criterion is to provide dual independent systems.

AMC · AMC 25.207(b) — CS-25 · ED Decision 2003/2/RM · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

AMCAcceptable means of compliance

AMC 25.207(c)and (d) Stall warning

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1 An acceptable method of demonstrating compliance with CS 25.207(c) is to consider stall warning speed margins obtained during stall speed demonstration (CS 25.103) and stall demonstration (CS 25.201(a)) (i.e. bank angle, power and centre of gravity conditions). In addition, if the stall warning margin is managed by a system (thrust law, bank angle law, …), stall warning speed margin required by CS 25.207(c) should be demonstrated, when the speed is reduced at rates not exceeding 0.5 m/s2 (one knot per second), for the most critical conditions in terms of stall warning margin, without exceeding 40° bank angle or maximum continuous power or thrust during the demonstrations. In the case where the management system increases, by design, the stall warning speed margin from the nominal setting (flight idle, wing level), no additional demonstration needs to be done. 2 The stall warning speed margins required by CS 25.207(c) and (d) must be determined at a constant load factor (i.e. 1g for 207(d)). An acceptable data reduction method is to calculate k = √(CLID/CLSW) where CLID and CLSW are the CL values respectively at the stall identification and at the stall warning activation. 3 If the stall warning required by CS 25.207 is provided by a device (e.g. a stick shaker), the effect of production tolerances on the stall warning system should be considered when evaluating the stall warning margin required by CS 25.207(c) and (d) and the manoeuvre capabilities required by CS 25.143(g). a. The stall warning margin required by CS 25.207(c) and (d) should be available with the stall warning system set to the most critical setting expected in production. Unless another setting would be provide a lesser margin, the stall warning margin required by CS 25.207(c) should be evaluated assuming the stall warning system is operating at its high angle of attack limit. For aeroplanes equipped with a device that abruptly pushes the nose down at a selected angle-of-attack (e.g. a stick pusher), the stall warning margin required by CS 25.207(c) may be evaluated with both the stall warning and stall identification (e.g. stick pusher) systems at their nominal angle of attack settings unless a lesser margin can result from the various system tolerances. b. The manoeuvre capabilities required by CS 25.143(g) should be available assuming the stall warning system is operating on its nominal setting. In addition, when the stall warning system is operating at its low angle of attack limit, the manoeuvre capabilities should not be reduced by more than 2 degrees of bank angle from those specified in CS 25.143(g). c. The stall warning margins and manoeuvre capabilities may be demonstrated by flight testing at the settings specified above for the stall warning and, if applicable, stall identification systems. Alternatively, compliance may be shown by applying adjustments to flight test data obtained at a different system setting.

AMC · AMC 25.207(c) — CS-25 · ED Decision 2003/2/RM · CS-25 Easy Access Rules · EAR revision 26 Jan 2023

All rules in SUBPART B – FLIGHT

Consolidated from the EASA Easy Access Rules (revision 26 Jan 2023, extracted 17 Aug 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.

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