CS 25.20 Scope

ED Decision 2003/2/RM

(a) The requirements of this Subpart B apply to aeroplanes powered with turbine engines –

(1) Without contingency thrust ratings, and

(2) For which it is assumed that thrust is not increased following engine failure during take-off except as specified in sub-paragraph (c).

(b) In the absence of an appropriate investigation of operational implications these requirements do not necessarily cover –

(1) Automatic landings.

(2) Approaches and landings with decision heights of less than 60 m (200 ft).

(3) Operations on unprepared runway surfaces.

(c) If the aeroplane is equipped with an engine control system that automatically resets the power or thrust on the operating engine(s) when any engine fails during take-off, additional requirements pertaining to aeroplane performance and limitations and the functioning and reliability of the system, contained in Appendix I, must be complied with.

CS 25.21 Proof of compliance

ED Decision 2016/010/R

(a) Each requirement of this Subpart must be met at each appropriate combination of weight and centre of gravity within the range of loading conditions for which certification is requested. This must be shown –

(1) By tests upon an aeroplane of the type for which certification is requested, or by calculations based on, and equal in accuracy to, the results of testing; and

(2) By systematic investigation of each probable combination of weight and centre of gravity, if compliance cannot be reasonably inferred from combinations investigated.

(b) Reserved

(c) The controllability, stability, trim, and stalling characteristics of the aeroplane must be shown for each altitude up to the maximum expected in operation.

(d) Parameters critical for the test being conducted, such as weight, loading (centre of gravity and inertia), airspeed, power, and wind, must be maintained within acceptable tolerances of the critical values during flight testing. (See AMC 25.21(d))

(e) If compliance with the flight characteristics requirements is dependent upon a stability augmentation system or upon any other automatic or power-operated system, compliance must be shown with CS 25.671 and 25.672.

(f) In meeting the requirements of CS 25.105(d), 25.125, 25.233 and 25.237, the wind velocity must be measured at a height of 10 metres above the surface, or corrected for the difference between the height at which the wind velocity is measured and the 10-metre height.

(g) The requirements of this subpart associated with icing conditions apply only if the applicant is seeking certification for flight in icing conditions. (See AMC 25.21(g))

(1) Each requirement of this subpart, except CS 25.121(a), 25.123(c), 25.143(b)(1) and (b)(2), 25.149, 25.201(c)(2), and 25.251(b) through (e), must be met in the icing conditions specified in Appendix C. CS 25.207(c) and (d) must be met in the landing configuration in the icing conditions specified in Appendix C but need not be met for other configurations. Compliance must be shown using the ice accretions defined in part II of Appendix C, assuming normal operation of the aeroplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Aeroplane Flight Manual.

(2)  If the applicant does not seek certification for flight in all icing conditions defined in Appendix O, each requirement of this subpart, except CS 25.105, 25.107, 25.109, 25.111, 25.113, 25.115, 25.121, 25.123, 25.143(b)(1), (b)(2), and (c)(1), 25.149, 25.201(c)(2), 25.207(c), (d) and (e)(1), and 25.251(b) through (e), must be met in the Appendix O icing conditions for which certification is not sought in order to allow a safe exit from those conditions. Compliance must be shown using the iceaccretions defined in part II, paragraphs (b) and (d) of Appendix O, assuming normal operation of the aeroplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Aeroplane Flight Manual. If applicable, a comparative analysis (refer to CS 25.1420) may be used to show compliance as an alternative to using the ice accretions defined in part II, paragraphs (b) and (d) of Appendix O.

(3)  If the applicant seeks certification for flight in any portion of the icing conditions of Appendix O, each requirement of this subpart, except paragraphs CS 25.121(a), 25.123(c), 25.143(b)(1) and (b)(2), 25.149, 25.201(c)(2), and 25.251(b) through (e), must be met in the Appendix O icing conditions for which certification is sought. CS 25.207(c) and (d) must be met in the landing configuration in the icing conditions specified in Appendix O for which certification is sought but need not be met for other configurations. Compliance must be shown using the ice accretions defined in part II, paragraphs (c) and (d) of Appendix O, assuming normal operation of the aeroplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Aeroplane Flight Manual. If applicable, a comparative analysis (refer to CS 25.1420) may be used to show compliance as an alternative to using the ice accretions defined in part II, paragraphs (c) and (d) of Appendix O.

(4) No changes in the load distribution limits of CS 25.23, the weight limits of CS 25.25 (except where limited by performance requirements of this subpart), and the centre of gravity limits of CS 25.27, from those for non-icing conditions, are allowed for flight in icing conditions or with ice accretion.

[Amdt 25/3]

[Amdt 25/6]

[Amdt 25/16]

[Amdt 25/17]

[Amdt 25/18]

AMC 25.21(d) Proof of compliance

ED Decision 2003/2/RM

1 Where variation of the parameter on which a tolerance is permitted will have an appreciable effect on the test, the result should be corrected to the specified value of the parameter; otherwise no correction is necessary.

2 In areas of critical handling or stability, notwithstanding the tolerance of CS 25.21(d) (7% total travel), aft centre of gravity tests should be flown at a centre of gravity not more forward than the certificate aft centre of gravity limit. Tests which are critical on the forward centre of gravity limit should be flown at centres of gravity at least as forward as the certificate forward limit.

AMC 25.21(g) Performance and handling characteristics in icing conditions

ED Decision 2018/005/R

Table of Contents

Para. Title

1 Purpose

2 Related Requirements

3 Reserved

4 Requirements and Guidance

4.1 General

4.2 Proof of Compliance (CS 25.21(g))

4.3 Propeller Speed and Pitch Limits (CS 25.33)

4.4 Performance - General (CS 25.101)

4.5 Stall Speed (CS 25.103)

4.6 Failure Conditions (CS 25.1309)

4.7 Flight-related Systems

4.8 Aeroplane Flight Manual (CS 25.1581)

5 Acceptable Means of Compliance - General

5.1 General

5.2 Flight Testing

5.3 Wind Tunnel Testing and Analysis

5.4 Engineering Simulator Testing and Analysis

5.5 Engineering Analysis

5.6 Ancestor Aeroplane Analysis

6 Acceptable Means of Compliance - Flight Test Programme

6.1 General

6.2 Stall Speed (CS 25.103)

6.3 Accelerate-stop Distance (CS 25.109)

6.4 Take-off Path (CS 25.111)

6.5 Landing Climb: All-engines-operating (CS 25.119)

6.6 Climb: One-engine-inoperative (CS 25.121)

6.7 En-route Flight Path (CS 25.123)

6.8 Landing (CS 25.125)

6.9 Controllability and Manoeuvrability - General (CS 25.143)

6.10 Longitudinal Control (CS 25.145)

6.11 Directional and Lateral Control (CS 25.147)

6.12 Trim (CS 25.161)

6.13 Stability - General (CS 25.171)

6.14 Demonstration of Static Longitudinal Stability (CS 25.175)

6.15 Static Directional and Lateral Stability (CS 25.177)

6.16 Dynamic Stability (CS 25.181)

6.17 Stall Demonstration (CS 25.201)

6.18 Stall Warning (CS 25.207)

6.19 Wind Velocities (CS 25.237)

6.20 Vibration and Buffeting (CS 25.251)

6.21 Natural Icing Conditions

6.22 Failure Conditions (CS 25.1309)

A1 Appendix 1 - Airframe Ice Accretion

A1.1 General

A1.2 Operative Ice Protection System

A1.3 Ice Protection System Failure Cases

A1.4 Additional guidance for Appendix O ice accretions

A2 https://dxweb.easa.europa.eu/dx4/Topics/Cloned-908a3904-6301-4e9d-a841-… - Artificial Ice Shapes

A2.1 General

A2.2 Shape and Texture of Artificial Ice

A2.3 "Sandpaper Ice"

A3 Appendix 3 - Design Features

A3.1 Aeroplane Configuration and Ancestry

A3.2 Wing

A3.3 Empennage

A3.4 Aerodynamic Balancing of Flight Control Surfaces

A3.5 Ice Protection/Detection System

A4 Appendix 4 - Examples of Aeroplane Flight Manual Limitations and Operating Procedures for Operations    in Supercooled Large Drop Icing Conditions

A5 Appendix 5 - Related Acceptable Means of Compliance (AMC) and FAA Advisory Circulars (AC)

A6 Appendix 6 - Acronyms and definitions

1 Purpose.

1.1 This AMC describes an acceptable means for showing compliance with the requirements related to performance and handling characteristics of Large Aeroplanes as affected by flight in icing conditions. The means of compliance described in this AMC is intended to provide guidance to supplement the engineering and operational judgement that should form the basis of any compliance findings relative to handling characteristics and performance in Appendix C and Appendix O icing conditions.

1.2 The guidance information is presented in sections 4 to 6 and three appendices.

1.3 Section 4 explains the various performance and handling requirements in relation to the flight conditions that are relevant for determining the shape and texture of ice accretions for the aeroplane in the atmospheric icing conditions of CS-25, Appendix C and Appendix O.

1.4 Section 5 describes acceptable methods and procedures that an applicant may use to show that an aeroplane meets these requirements. Depending on the design features of a specific aeroplane as discussed in Appendix 3 of this AMC, its similarity to other types or models, and the service history of those types or models, some judgement will often be necessary for determining that any particular method or procedure is adequate for showing compliance with a particular requirement. AMC 25.1420(f) provides guidance for comparative analysis as an acceptable means of compliance to meet these requirements.

1.5 Section 6 provides an acceptable flight test programme where flight testing is selected by the applicant and agreed by the Agency as being the primary means of compliance.

1.6 The three appendices provide additional reference material associated with ice accretion, artificial ice shapes, and aeroplane design features.

2 Related Requirements. The following paragraphs of CS-25 are related to the guidance in this AMC:

—             CS 25.21 (Proof of compliance)

—             CS 25.103 (Stall speed)

—             CS 25.105 (Take-off)

—             CS 25.107 (Take-off speeds)

—             CS 25.111 (Take-off path)

—             CS 25.119 (Landing climb)

—             CS 25.121 (Climb: One-engine-inoperative)

—             CS 25.123 (En-route flight paths)

—             CS 25.125 (Landing)

—             CS 25.143 (Controllability and Manoeuvrability - General)

—             CS 25.207 (Stall warning)

—             CS 25.237 (Wind velocities)

—             CS 25.253 (High-speed characteristics)

—             CS 25.1309 (Equipment, systems, and installations)

—             CS 25.1419 (Ice protection)

—             CS 25.1420 (Supercooled large drop icing conditions)

—             CS 25.1581 (Aeroplane Flight Manual)

—             CS-25, Appendix C

—             CS 25, Appendix O

3 Reserved.

4 Requirements and Guidance.

4.1 General. This section provides guidance for showing compliance with Subpart B requirements for flight in the icing conditions of Appendix C and Appendix O to CS-25.

4.1.1 Operating rules for commercial operation of large aeroplanes (e.g. Part-CAT¹, CAT.OP.MPA.250) require that the aeroplane is free of any significant ice contamination at the beginning of the take-off roll due to application of appropriate ice removal and ice protection procedures during flight preparation on the ground.

4.1.2 For certification for flight in the icing conditions described in Appendix C of CS-25, CS 25.21(g)(1) requires that an aeroplane meet certain performance and handling qualities requirements while operating in the icing environment defined in Appendix C. In addition, CS 25.1420 requires applicants to consider icing conditions beyond those covered by Appendix C. The additional icing conditions that must be considered are the supercooled large drop icing conditions defined in Appendix O. CS 25.21(g)(2) and (3) respectively provide the performance and handling qualities requirements to be met by applicants not seeking certification in the icing conditions of Appendix O and by applicants seeking certification in any portion of the icing conditions of Appendix O. Appendix 1 of this AMC provides detailed guidance for determining ice accretions in both Appendix C and Appendix O icing conditions that can be used for showing compliance.

CS 25.1420 requires applicants to choose to do one of the following:

(a) Not seek approval for flight in the supercooled large drop atmospheric icing conditions defined in Appendix O.

(b) Seek approval for flight in only a portion of Appendix O icing conditions.

(c) Seek approval for flight throughout the entire Appendix O atmospheric icing envelope.

4.1.3 Because an aeroplane may encounter supercooled large drop icing conditions at any time while flying in icing conditions, certain safety requirements must be met for the supercooled large drop icing conditions of Appendix O, even if the aeroplane will not be certified for flight in the complete range of Appendix O atmospheric icing conditions. CS 25.21(g)(2) requires the stall speed (CS 25.103), landing climb (CS 25.119), and landing (CS 25.125) requirements to be met in supercooled large drop atmospheric icing conditions beyond those the aeroplane will be certified for. Compliance with these requirements plus the requirements for flight in Appendix C icing conditions are intended to provide adequate performance capability for a safe exit from all icing conditions after an encounter with supercooled large drop atmospheric icing conditions beyond those the aeroplane is certified for.

4.1.4 If the aeroplane is not to be certified for flight in all of the supercooled large drop icing conditions of Appendix O, there must be a means of indicating when the aeroplane has encountered icing conditions beyond those it is certified for. See AMC 25.1420 for guidance on acceptable means of detecting and indicating when the aeroplane has encountered icing conditions beyond those it is certified for. The applicant should provide procedures in the aeroplane flight manual to enable a safe exit from all icing conditions after an encounter with icing conditions beyond those the aeroplane is certified for.

4.1.5 To certify an aeroplane for operations in Appendix O icing conditions only for certain flight phase(s), the applicant should define the flight phase(s) for which approval is sought in a way that will allow a flight crew to easily determine whether the aeroplane is operating inside or outside its certified icing envelope. The critical ice accretion or accretions used to show compliance with the applicable requirements should cover the range of aeroplane configurations, operating speeds, angles-of-attack, and engine thrust or power settings that may be encountered during that phase of flight (not just at the conditions specified in the CS-25 subpart B requirements). For the ice accretion scenarios defined in paragraph A1.4.3(c) of Appendix 1 to this AMC, the applicable flight phases are take-off (including the ground roll, take-off, and final take-off segments), en route, holding, and approach/landing (including both the approach and landing segments).

4.1.6 Ice accretions used to show compliance with the applicable CS-25 subpart B regulations should be consistent with the extent of the desired certification for flight in icing conditions. Appendices C and O define the ice accretions, as a function of flight phase, that must be considered for certification for flight in those icing conditions. Any of the applicable ice accretions (or a composite accretion representing a combination of accretions) may be used to show compliance with a particular subpart B requirement if it is either the ice accretion identified in the requirement or one shown to be more conservative than that. In addition, the ice accretion with the most adverse effect on handling characteristics may be used for compliance with the aeroplane performance requirements if each difference in performance is conservatively taken into account. Ice accretion(s) used to show compliance should take into account the speeds, configurations (including configuration changes), angles of attack, power or thrust settings, etc. for the flight phases and icing conditions they are intended to cover. For example, if the applicant desires certification for flight in the supercooled large drop icing conditions of Appendix O in addition to those of Appendix C, compliance with the applicable subpart B requirements may be shown using the most critical of the Appendix C and Appendix O ice accretions.

4.1.7 Certification experience has shown that it is not necessary to consider ice accumulation on the propeller, induction system or engine components of an inoperative engine for handling qualities substantiation.  Similarly, the mass of the ice need not normally be considered.

4.1.8 Flight in icing conditions includes operation of the aeroplane after leaving the icing conditions, but with ice accretion remaining on the critical surfaces of the aeroplane.

4.1.9 Ice-contaminated tailplane stall (ICTS) refers to a phenomenon identified as a causal factor in several aeroplane incidents and accidents. It results from airflow separation on the lower surface of the tailplane because ice is present. ICTS can occur if the angle-of-attack of the horizontal tailplane exceeds its stall angle-of-attack. Even very small quantities of ice on the tailplane leading edge can significantly reduce the angle-of-attack at which the tailplane stalls. An increase in tailplane angle-of-attack, which may lead to a tailplane stall, can result from changes in aeroplane configuration (for example, extending flaps, which increases the downwash angle at the tail or the pitch trim required) or flight conditions (a high approach speed, gusts, or manoeuvring, for example). An ICTS is characterized by reduction or loss of pitch control or pitch stability while in, or soon after leaving, icing conditions. A flight test procedure for determining susceptibility to ICTS is presented in paragraph 6.9.4, Low g Manoeuvres and Sideslips, of this AMC.

(a)  For aeroplanes with unpowered longitudinal control systems, the pressure differential between the upper and lower surfaces of the stalled tailplane may result in a high elevator hinge moment, forcing the elevator trailing edge down. This elevator hinge moment reversal can be of sufficient magnitude to cause the longitudinal control (for example, the control column) to suddenly move forward with a force beyond the capability of the flight crew to overcome. On some aeroplanes, ICTS has been caused by a lateral flow component coming off the vertical stabilizer, as may occur in sideslip conditions or because of a wind gust with a lateral component.

(b)  Aerodynamic effects of reduced tailplane lift should be considered for all aeroplanes, including those with powered controls. Aeroplanes susceptible to this phenomenon are those having a near zero or negative tailplane stall margin with tailplane ice contamination.

4.1.10  There have been aeroplane controllability incidents in icing conditions as a result of ice on unprotected leading edges of extended trailing edge flaps or flap vanes. The primary safety concern illustrated by these incidents is the potential for controllability problems due to the accretion of ice on trailing edge flap or flap vane leading edges while extending flaps in icing conditions. The flight tests specified in Table 4 of this AMC, in which handling characteristics are tested at each flap position while ice is being accreted in natural icing conditions, are intended to investigate this safety concern. Unless controllability concerns arise from these tests, it is not necessary to conduct flight tests with artificial ice shapes on the extended trailing edge flap or flap vanes or to include extended trailing edge flap or flap vane ice accretions when evaluating aeroplane performance with flaps extended.

4.1.11  Supercooled large drop icing conditions, or runback ice in any icing condition, can cause a ridge of ice to form aft of the protected area on the upper surface of the wing. This can lead to separated airflow over the aileron. Ice-induced airflow separation upstream of the aileron can have a significant effect on aileron hinge moment. Depending on the extent of the separated flow and the design of the flight control system, ice accretion upstream of the aileron may lead to aileron hinge moment reversal, reduced aileron effectiveness, and aileron control reversal. Although aeroplanes with de-icing boots and unpowered aileron controls are most susceptible to this problem, all aeroplanes should be evaluated for roll control capability in icing conditions. Acceptable flight test procedures for checking roll control capability are presented in paragraphs 6.9.3, 6.15, and 6.17.2.e of this AMC and consist of bank-to-bank roll manoeuvres, steady heading sideslips, and rolling manoeuvres at stall warning speed.

4.1.12  Appendix 5 contains related Acceptable Means of Compliance and FAA Advisory Circulars. Appendix 6 contains acronyms and definitions used in this AMC.

4.2 Proof of Compliance (CS 25.21(g)).

4.2.1 Demonstration of compliance with certification requirements for flight in icing conditions may be accomplished by any of the means discussed in paragraph 5.1 of this AMC.

4.2.2 Certification experience has shown that aeroplanes of conventional design do not require additional detailed substantiation of compliance with the requirements of the following paragraphs of CS-25 for flight in icing conditions or with ice accretions:

25.23, Load distribution limits

25.25, Weight limits

25.27, Centre of gravity limits

25.29, Empty weight and corresponding centre of gravity

25.31, Removable ballast

25.231, Longitudinal stability and control

25.233, Directional stability and control

25.235, Taxiing condition

25.253(a) and (b), High-speed characteristics, and

25.255, Out-of-trim characteristics

4.2.3 Where normal operation of the ice protection system results in changing the stall warning system and/or stall identification system activation settings, it is acceptable to establish a procedure to return to the non icing settings when it can be demonstrated that the critical wing surfaces are free of ice accretion.

4.3 Propeller Speed and Pitch Limits (CS 25.33). Certification experience has shown that it may be necessary to impose additional propeller speed limits for operations in icing conditions.

4.4 Performance - General (CS 25.101).

4.4.1 The propulsive power or thrust available for each flight condition must be appropriate to the aeroplane operating limitations and normal procedures for flight in icing conditions. In general, it is acceptable to determine the propulsive power or thrust available by suitable analysis, substantiated when required by appropriate flight tests (e.g. when determining the power or thrust available after 8 seconds for CS 25.119). The following aspects should be considered:

a. Operation of induction system ice protection.

b. Operation of propeller ice protection.

c. Operation of engine ice protection.

d. Operation of airframe ice protection system.

4.4.2 The following should be considered when determining the change in performance due to flight in icing conditions:

a. Thrust loss due to ice accretion on propulsion system components with normal operation of the ice protection system, including engine induction system and/or engine components, and propeller spinner and blades.

b. The incremental airframe drag due to ice accretion with normal operation of the ice protection system.

c. Changes in operating speeds due to flight in icing conditions.

4.4.3 Certification experience has shown that any increment in drag (or decrement in thrust) due to the effects of ice accumulation on the landing gear, propeller, induction system and engine components may be determined by a suitable analysis or by flight test.

4.4.4 Apart from the use of appropriate speed adjustments to account for operation in icing conditions, any changes in the procedures established for take-off, balked landing, and missed approaches should be agreed with the Agency.

4.4.5 Performance associated with flight in icing conditions is applicable after exiting icing conditions until the aeroplane critical surfaces are free of ice accretion and the ice protection systems are selected “Off.”

4.4.6 Certification experience has also shown that runback ice may be critical for propellers, and propeller analyses do not always account for it. Therefore, runback ice on the propeller should be addressed. Research has shown that ice accretions on propellers, and resulting thrust decrement, may be larger in Appendix O (supercooled large drop) icing conditions than in Appendix C icing conditions for some designs. This may be accomplished through aeroplane performance checks in natural icing conditions, icing tanker tests, icing wind tunnel tests, aerodynamic analysis, or the use of an assumed (conservative) loss in propeller efficiency. Testing should include a range of outside air temperatures, including warmer (near freezing) temperatures that could result in runback icing. For the Appendix O icing conditions, the applicant may use a comparative analysis. AMC 25.1420(f) provides guidance for comparative analysis.

4.5 Stall speed (CS 25.103). Certification experience has shown that for aeroplanes of conventional design it is not necessary to make a separate determination of the effects of Mach number on stall speeds for the aeroplane with ice accretions.

4.6 Failure Conditions (CS 25.1309).

4.6.1 The failure modes of the ice protection system and the resulting effects on aeroplane handling and performance should be analysed in accordance with CS 25.1309. In determining the probability of a failure condition, it should be assumed that the probability of entering icing conditions defined in CS-25 Appendix C is one. As explained in AMC 25.1420, on an annual basis, the average probability of encountering the icing conditions defined in Appendix O may be assumed to be 1 × 10_-2 per flight hour. This probability should not be reduced on a phase-of-flight basis. The "Failure Ice" configuration is defined in Appendix 1, paragraph A1.3.

4.6.2 For probable failure conditions that are not annunciated to the flight crew, the guidance in this AMC for a normal condition is applicable with the "Failure Ice" configuration.

4.6.3 For probable failure conditions that are annunciated to the flight crew, with an associated procedure that does not require the aeroplane to exit icing conditions, the guidance in this AMC for a normal condition is applicable with the "Failure Ice" configuration.

4.6.4 For probable failure conditions that are annunciated to the flight crew, with an associated operating procedure that requires the aeroplane to leave the icing conditions as soon as possible, it should be shown that the aeroplane’s resulting performance and handling characteristics with the failure ice accretion are commensurate with the hazard level as determined by a system safety analysis in accordance with CS 25.1309. The operating procedures and related speeds may restrict the aeroplane’s operating envelope, but the size of the restricted envelope should be consistent with the safety analysis.

4.6.5 For failure conditions that are extremely remote but not extremely improbable, the analysis and substantiation of continued safe flight and landing, in accordance with CS 25.1309, should take into consideration whether annunciation of the failure is provided and the associated operating procedures and speeds to be used following the failure condition.

4.7 Flight-related Systems. In general, systems aspects are covered by the applicable systems and equipment requirements in other subparts of CS-25, and associated guidance material.  However, certification experience has shown that other flight related systems aspects should be considered when determining compliance with the flight requirements of subpart B.  For example, the following aspects may be relevant:

a. The ice protection systems may not anti-ice or de-ice properly at all power or thrust settings. This may result in a minimum power or thrust setting for operation in icing conditions which affects descent and/or approach capability. The effect of power or thrust setting should also be considered in determining the applicable ice accretions. For example, a thermal bleed air system may be running wet resulting in the potential for runback ice.

b. Ice blockage of control surface gaps and/or freezing of seals causing increased control forces, control restrictions or blockage.

c. Airspeed, altitude and/or angle of attack sensing errors due to ice accretion forward of the sensors (e.g. radome ice). Dynamic pressure ("q") operated feel systems using separate sensors also may be affected.

d. Ice blockage of unprotected inlets and vents that may affect the propulsive thrust available, aerodynamic drag, powerplant control, or flight control.

e. Operation of stall warning and stall identification reset features for flight in icing conditions, including the effects of failure to operate.

f. Operation of icing condition sensors, ice accretion sensors, and automatic or manual activation of ice protection systems.

g. Flight guidance and automatic flight control systems operation. See AMC No. 1 and 2 to 25.1329 for guidance on compliance with CS 25.1329 for flight in icing conditions, including stall and manoeuvrability evaluations with the aeroplane under flight guidance system control.

h. Installed thrust. This includes operation of ice protection systems when establishing acceptable power or thrust setting procedures, control, stability, lapse rates, rotor speed margins, temperature margins, Automatic Take-Off Thrust Control System (ATTCS) operation, and power or thrust lever angle functions.

4.8 Aeroplane Flight Manual (CS 25.1581).

4.8.1 Limitations.

4.8.1.1 Where limitations are required to ensure safe operation in icing conditions, these limitations should be stated in the AFM.

4.8.1.2 The Limitations section of the AFM should include, as applicable, a statement similar to the following: “In icing conditions the aeroplane must be operated, and its ice protection systems used, as described in the operating procedures section of this manual. Where specific operational speeds and performance information have been established for such conditions, this information must be used."

4.8.1.3 For aeroplanes without leading edge high-lift devices, unless an acceptable means exists to ensure that the protected surfaces of the wing leading edges are free of ice contamination immediately prior to take-off, the wing ice protection system should be operative and efficient before take-off (at least during the final taxi phase) whenever the outside air temperature is below 6°C (42 °F) and any of the following applies:

—             Visible moisture is present in the air or on the wing,

—              The difference between the dew point temperature and the outside air temperature is less than 3°C (5 °F), or

—              Standing water, slush, ice, or snow is present on taxiways or runways.

An acceptable means to ensure that the wing leading edges are free of ice contamination immediately prior to take-off would be the application of anti-icing fluid with adequate hold over time and compliant with SAE AMS 1428, Types II, III, or IV.

Note: The aircraft must be de-iced in compliance with applicable operational rules.

4.8.1.4 To comply with CS 25.1583(e), Kinds of operation, the AFM Limitations section should clearly identify the extent of each approval to operate in icing conditions, including the extent of any approval to operate in the supercooled large drop atmospheric icing conditions defined in CS-25 Appendix O.

4.8.1.5 For aeroplanes not certified to operate throughout the atmospheric icing envelope of CS-25 Appendix O for every flight phase, the Limitations section of the AFM should also identify the means for detecting when the certified icing conditions have been exceeded and state that intentional flight, including take-off and landing, into these conditions is prohibited. A requirement to exit all icing conditions must be included if icing conditions for which the aeroplane is not certified are encountered.

4.8.2 Operating Procedures.

4.8.2.1 AFM operating procedures for flight in icing conditions should include normal operation of the aeroplane including operation of the ice protection system and operation of the aeroplane following ice protection system failures. Any changes in procedures for other aeroplane system failures that affect the capability of the aeroplane to operate in icing conditions should be included.

4.8.2.2 Normal operating procedures provided in the AFM should reflect the procedures used to certify the aeroplane for flight in icing conditions.  This includes configurations, speeds, ice protection system operation, power plant and systems operation, for take-off, climb, cruise, descent, holding, go-around, and landing. For aeroplanes not certified for flight in all of the supercooled large drop atmospheric icing conditions defined in Appendix O to CS-25, procedures should be provided for safely exiting all icing conditions if the aeroplane encounters Appendix O icing conditions that exceed the icing conditions the aeroplane is certified for. Information to be provided in the AFM may be based on the information provided in the reference fleet AFM(s), or other operating manual(s) furnished by the TC holder, when comparative analysis is used as the means of compliance.

4.8.2.3 For aeroplanes without leading edge high-lift devices, the AFM normal operating procedures section should contain a statement similar to the following:

“WARNING

Minute amounts of ice or other contamination on the leading edges or wing upper surfaces can result in a stall without warning, leading to loss of control on take-off.”

4.8.2.4 Abnormal operating procedures should include the procedures to be followed in the event of annunciated ice protection system failures and suspected unannunciated failures. Any changes to other abnormal procedures contained in the AFM, due to flight in icing conditions, should also be included.

4.8.3 Performance Information. Performance information, derived in accordance with subpart B of CS-25, must be provided in the AFM for all relevant phases of flight.

4.8.4 Examples of AFM limitations and operating procedures are contained in Appendix 4 of this AMC.

5 Acceptable Means of Compliance - General.

5.1 General.

5.1.1 This section describes acceptable methods and procedures that an applicant may use to show that an aeroplane meets the performance and handling requirements of subpart B in the atmospheric conditions of Appendix C and Appendix O to CS-25.

5.1.2 Compliance with CS 25.21(g) should be shown by one or more of the methods listed in this section.

5.1.3 The compliance process should address all phases of flight, including take-off, climb, cruise, holding, descent, landing, and go-around as appropriate to the aeroplane type, considering its typical operating regime and the extent of its certification approval for operation in the atmospheric icing conditions of Appendix O to CS-25.

5.1.4 The design features included in Appendix 3 of this AMC should be considered when determining the extent of the substantiation programme.

5.1.5 Appropriate means for showing compliance include the actions and items listed in Table 1 below. These are explained in more detail in the following sections of this AMC.

TABLE 1: Means for Showing Compliance

Flight Testing	Flight testing in dry air using artificial ice shapes or with ice shapes created in natural icing conditions.
Wind Tunnel Testing and Analysis	An analysis of results from wind tunnel tests with artificial or actual ice shapes.
Engineering Simulator Testing and Analysis	An analysis of results from engineering simulator tests.
Engineering Analysis	An analysis which may include the results from any of the other means of compliance as well as the use of engineering judgment.
Ancestor Aeroplane Analysis	An analysis of results from a closely related ancestor aeroplane.
Comparative analysis for showing compliance in SLD icing conditions	An analysis which substantiates that a new or derivative aeroplane model has at least the same level of safety in all supercooled liquid water icing conditions that a reference fleet has achieved. Guidance is provided in AMC 25.1420(f). The use of a comparative analysis is only an option for showing compliance with CS-25 specifications relative to Appendix O icing conditions; it is not an option for showing compliance with CS-25 specifications relative to Appendix C icing conditions.

5.1.6 Various factors that affect ice accretion on the airframe with an operative ice protection system and with ice protection system failures are discussed in Appendix 1 of this AMC.

5.1.7 An acceptable methodology to obtain agreement on the artificial ice shapes is given in Appendix 2 of this AMC. That appendix also provides the different types of artificial ice shapes to be considered.

5.2 Flight Testing.

5.2.1 General.

5.2.1.1 The extent of the flight test programme should consider the results obtained with the non-contaminated aeroplane and the design features of the aeroplane as discussed in Appendix 3 of this AMC.

5.2.1.2 It is not necessary to repeat an extensive performance and flight characteristics test programme on an aeroplane with ice accretion. A suitable programme that is sufficient to demonstrate compliance with the requirements can be established from experience with aeroplanes of similar size, and from review of the ice protection system design, control system design, wing design, horizontal and vertical stabiliser design, performance characteristics, and handling characteristics of the non-contaminated aeroplane. In particular, it is not necessary to investigate all weight and centre of gravity combinations when results from the non-contaminated aeroplane clearly indicate the most critical combination to be tested.  It is not necessary to investigate the flight characteristics of the aeroplane at high altitude (i.e. above the highest altitudes specified in Appendix C and Appendix O to CS-25). An acceptable flight test programme is provided in section 6 of this AMC.

5.2.1.3 Certification experience has shown that tests are usually necessary to evaluate the consequences of ice protection system failures on handling characteristics and performance and to demonstrate continued safe flight and landing.

5.2.2 Flight Testing Using Approved Artificial Ice Shapes.

5.2.2.1 The performance and handling tests may be based on flight testing in dry air using artificial ice shapes that have been agreed with the Agency.

5.2.2.2 Additional limited flight tests are discussed in paragraph 5.2.3, below.

5.2.3 Flight Testing In Natural Icing Conditions.

5.2.3.1 Where flight testing with ice accretion obtained in natural atmospheric icing conditions is the primary means of compliance, the conditions should be measured and recorded. The tests should ensure good coverage of CS-25 Appendix C and Appendix O conditions (consistent with the extent of the certification approval sought for operation in Appendix O icing conditions) and, in particular, the critical conditions. The conditions for accreting ice (including the icing atmosphere, configuration, speed and duration of exposure) should be agreed with the Agency.

5.2.3.2 Where flight testing with artificial ice shapes is the primary means of compliance, additional limited flight tests should be conducted with ice accretion obtained in natural icing conditions. The objective of these tests is to corroborate the handling characteristics and performance results obtained in flight testing with artificial ice shapes. As such, it is not necessary to measure the atmospheric characteristics (i.e. liquid water content (LWC) and median volumetric diameter (MVD)) of the flight test icing conditions. For some derivative aeroplanes with similar aerodynamic characteristics as the ancestor, it may not be necessary to carry out additional flight test in natural icing conditions if such tests have been already performed with the ancestor. Depending on the extent of the Appendix O icing conditions that certification is being sought for, and the means used for showing compliance with the performance and handling characteristics requirements, it may also not be necessary to conduct flight tests in the natural icing conditions of Appendix O. See AMC 25.1420 for guidance on when it is necessary to conduct flight tests in the natural atmospheric icing conditions of Appendix O.

5.3 Wind Tunnel Testing and Analysis. Analysis of the results of dry air wind tunnel testing of models with artificial ice shapes, as defined in Part II of Appendix C and Appendix O to CS-25, may be used to substantiate the performance and handling characteristics.

5.4 Engineering Simulator Testing and Analysis. The results of an engineering simulator analysis of an aeroplane that includes the effects of the ice accretions as defined in Part II of Appendix C and Appendix O to CS-25 may be used to substantiate the handling characteristics. The data used to model the effects of ice accretions for the engineering simulator may be based on results of dry air wind tunnel tests, flight tests, computational analysis, and engineering judgement.

5.5 Engineering Analysis. An engineering analysis that includes the effects of the ice accretions as defined in Part II of Appendix C and Appendix O to CS-25 may be used to substantiate the performance and handling characteristics. The effects of the ice shapes used in this analysis may be determined by an analysis of the results of dry air wind tunnel tests, flight tests, computational analysis, engineering simulator analysis, and engineering judgement.

5.6 Ancestor Aeroplane Analysis.

5.6.1 To help substantiate acceptable performance and handling characteristics, the applicant may use an analysis of an ancestor aeroplane that includes the effect of the ice accretions as defined in Part II of Appendix C and Appendix O to CS-25. This analysis should consider the similarity of the configuration, operating envelope, performance and handling characteristics, and ice protection system of the ancestor aeroplane to the one being certified.

5.6.2 The analysis may include flight test data, dry air wind tunnel test data, icing tunnel test data, engineering simulator analysis, service history, and engineering judgement.

5.7  Comparative Analysis.

  For showing compliance with the CS-25 certification specifications relative to SLD icing conditions represented by Appendix O, the applicant may use a comparative analysis. AMC 25.1420 (f) provides guidance for comparative analysis.

6 Acceptable Means of Compliance - Flight Test Programme.

6.1 General.

6.1.1 This section provides an acceptable flight test programme where flight testing is selected by the applicant and agreed by the Agency as being the primary means for showing compliance.

6.1.2 Where an alternate means of compliance is proposed for a specific paragraph in this section, it should enable compliance to be shown with at least the same degree of confidence as flight test would provide (see CS 25.21(a)(1)).

6.1.3 Ice accretions for each flight phase are defined in Part II of Appendix C and Part II of Appendix O to CS-25. Additional guidance for determining the applicable ice accretions is provided in Appendix 1 to this AMC.

6.1.4 This test programme is based on the assumption that the applicant will choose to use the holding Ice accretion for the majority of the testing assuming that it is the most conservative ice accretion. In general, the applicant may choose to use an ice accretion that is either conservative or is the specific ice accretion that is appropriate to the particular phase of flight. In accordance with Part II of Appendix C and Part II(e) of Appendix O to CS-25, if the holding ice accretion is not as conservative as the ice accretion appropriate to the flight phase, then the ice accretion appropriate to the flight phase (or a more conservative ice accretion) must be used.

6.1.5 For the approach and landing configurations, in accordance with the guidance provided in paragraph 4.1.10 of this AMC, the flight tests in natural icing conditions specified in Table 4 of this AMC are usually sufficient to evaluate whether ice accretions on trailing edge flaps adversely affect aeroplane performance or handling qualities. If these tests show that aeroplane performance or handling qualities are adversely affected, additional tests may be necessary to show compliance with the aeroplane performance and handling qualities requirements.

6.2 Stall Speed (CS 25.103).

6.2.1 The stall speed for intermediate high lift configurations can normally be obtained by interpolation. However if a stall identification system (e.g. stick pusher) activation point is set as a function of the high lift configuration and/or the activation point is reset for icing conditions, or if significant configuration changes occur with extension of trailing edge flaps (such as wing leading edge high-lift device position movement), additional tests may be necessary.

6.2.2 Acceptable Test Programme. The following represents an acceptable test programme subject to the provisions outlined above:

a. Forward centre of gravity position appropriate to the configuration.

b. Normal stall test altitude.

c. In the configurations listed below, trim the aeroplane at an initial speed of 1.13 to 1.30 V_SR. Decrease speed at a rate not to exceed 0.5 m/sec² (1 knot per second) until an acceptable stall identification is obtained.

i. High lift devices retracted configuration, "Final Take-off Ice."

ii. High lift devices retracted configuration, "En-route Ice."

iii. Holding configuration, "Holding Ice."

iv. Lowest lift take-off configuration, "Holding Ice."

v. Highest lift take-off configuration, "Take-off Ice."

vi. Highest lift landing configuration, "Holding Ice."

6.3 Accelerate-stop Distance (CS 25.109). The effect of any increase in V1 due to take-off in icing conditions may be determined by a suitable analysis.

6.4 Take-off Path (CS 25.111). If VSR in the configuration defined by CS 25.121(b) with the “Take-off Ice" accretion defined in Appendix C and Appendix O to CS-25 exceeds VSR for the same configuration without ice accretions by more than the greater of 5.6 km/h (3 knots) or 3%, the take-off demonstrations should be repeated to substantiate the speed schedule and distances for take-off in icing conditions.  The effect of the take-off speed increase, thrust loss, and drag increase on the take-off path may be determined by a suitable analysis.

6.5 Landing Climb: All-engines-operating (CS 25.119). Acceptable Test Programme. The following represents an acceptable test programme:

a. The "Holding Ice" accretion should be used.

b. Forward centre of gravity position appropriate to the configuration.

c. Highest lift landing configuration, landing climb speed no greater than VREF.

d. Stabilise at the specified speed and conduct 2 climbs or drag polar checks as agreed with the Agency.

6.6 Climb: One-engine-inoperative (CS 25.121). Acceptable Test Programme. The following represents an acceptable test programme:

a. Forward centre of gravity position appropriate to the configuration.

b. In the configurations listed below, stabilise the aeroplane at the specified speed with one engine inoperative (or simulated inoperative if all effects can be taken into account) and conduct 2 climbs in each configuration or drag polar checks substantiated for the asymmetric drag increment as agreed with the Agency.

i. High lift devices retracted configuration, final take-off climb speed, "Final Take-off Ice."

ii. Lowest lift take-off configuration, landing gear retracted, V₂ climb speed, "Take-off Ice."

iii. Approach configuration appropriate to the highest lift landing configuration, landing gear retracted, approach climb speed, "Holding Ice."

6.7 En-route Flight Path (CS 25.123). Acceptable Test Programme. The following represents an acceptable test programme:

a. The "En-route Ice" accretion should be used.

b. Forward centre of gravity position appropriate to the configuration.

c. En-route configuration and climb speed.

d. Stabilise at the specified speed with one engine inoperative (or simulated inoperative if all effects can be taken into account) and conduct 2 climbs or drag polar checks substantiated for the asymmetric drag increment as agreed with the Agency.

6.8 Landing (CS 25.125). The effect of landing speed increase on the landing distance may be determined by a suitable analysis.

6.9 Controllability and Manoeuvrability - General (CS 25.143 and 25.177).

6.9.1 A qualitative and quantitative evaluation is usually necessary to evaluate the aeroplane's controllability and manoeuvrability. In the case of marginal compliance, or the force limits or stick force per g limits of CS 25.143 being approached, additional substantiation may be necessary to establish compliance. In general, it is not necessary to consider separately the ice accretion appropriate to take-off and en-route because the "Holding Ice" is usually the most critical.

6.9.2 General Controllability and Manoeuvrability. The following represents an acceptable test programme for general controllability and manoeuvrability, subject to the provisions outlined above:

a. The "Holding Ice" accretion should be used.

b. Medium to light weight, aft centre of gravity position, symmetric fuel loading.

c In the configurations listed in Table 2, trim at the specified speeds and conduct the following manoeuvres:

i. 30° banked turns left and right with rapid reversals;

ii. Pull up to 1.5g (except that this may be limited to 1.3g at V_REF), and pushover to 0.5g (except that the pushover is not required at V_MO and V_FE); and

iii. Deploy and retract deceleration devices.

TABLE 2: Trim Speeds

Configuration	Trim Speed
High lift devices retracted configuration:	1.3 VSR, and
	VMO or 463 km/h (250 knots) IAS , whichever is less
Lowest lift takeoff configuration:	1.3 VSR, and
	VFE or 463 km/h (250 knots) IAS, whichever is less
Highest lift landing configuration:	VREF, and
	VFE or 463 km/h (250 knots) IAS, whichever is less.

V_{SR —} Reference Stall Speed

V_{MO —} Maximum operating limit speed

IAS _— Indicated air speed

V_{FE —} Maximum flap extended speed

V_{REF —} Reference landing speed

d. Lowest lift take-off configuration: At the greater of 1.13 V_SR or V₂ MIN, with the critical engine inoperative (or simulated inoperative if all effects can be taken into account), conduct 30° banked turns left and right with normal turn reversals and, in wings-level flight, a 9.3 km/h (5 knot) speed decrease and increase.

e. Conduct an approach and go-around with all engines operating using the recommended procedure.

f. Conduct an approach and go-around with the critical engine inoperative (or simulated inoperative if all effects can be taken into account) using the recommended procedure.

g. Conduct an approach and landing using the recommended procedure. In addition satisfactory controllability should be demonstrated during a landing at VREF minus 9.3 km/h (5 knots). These tests should be done at heavy weight and forward centre of gravity.

h. Conduct an approach and landing with the critical engine inoperative (or simulated inoperative if all effects can be taken into account) using the recommended procedure.

6.9.3 Evaluation of Lateral Control Characteristics. Aileron hinge moment reversal and other lateral control anomalies have been implicated in icing accidents and incidents. The following manoeuvre, along with the evaluation of lateral controllability during a deceleration to the stall warning speed covered in paragraph 6.17.2(e) of this AMC and the evaluation of static lateral-directional stability covered in paragraph 6.15 of this AMC, is intended to evaluate any adverse effects arising from both stall of the outer portion of the wing and control force characteristics.

For each of the test conditions specified in subparagraphs (a) and (b) below, perform the manoeuvres described in subparagraphs 1 through 6 below.

(a) Holding configuration, holding ice accretion, maximum landing weight, forward centre-of-gravity position, minimum holding speed (highest expected holding angle-of-attack); and

(b) Landing configuration, most critical of holding, approach, and landing ice accretions, medium to light weight, forward centre-of-gravity position, V_REF (highest expected landing approach angle-of-attack).

1 Establish a 30-degree banked level turn in one direction.

2 Using a step input of approximately 1/3 full lateral control deflection, roll the aeroplane in the other direction.

3 Maintain the control input as the aeroplane passes through a wings level attitude.

4 At approximately 20 degrees of bank in the other direction, apply a step input in the opposite direction to approximately 1/3 full lateral control deflection.

5 Release the control input as the aeroplane passes through a wings level attitude.

6 Repeat this test procedure with 2/3 and up to full lateral control deflection unless the roll rate or structural loading is judged excessive.  It should be possible to readily arrest and reverse the roll rate using only lateral control input, and the lateral control force should not reverse with increasing control deflection.

6.9.4 Low g Manoeuvres and Sideslips. The following represents an example of an acceptable test program for showing compliance with controllability requirements in low g manoeuvres and in sideslips to evaluate susceptibility to ice-contaminated tailplane stall.

6.9.4.1 CS 25.143(i)(2) states: “It must be shown that a push force is required throughout a pushover manoeuvre down to zero g 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).

6.9.4.2 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. Discontinuities in the control force characteristic, unless so small as to be unnoticeable, would not be considered to meet the requirement that the force be steadily increasing. A gradual change in control force is a change that is not abrupt and does not have a steep gradient that can be easily managed by a pilot of average skill, alertness, and strength. Control forces in excess of those permitted by CS 25.143(c) would be considered excessive.

(See paragraph 6.15.1 of this AMC for lateral-directional aspects).

6.9.4.3 The test manoeuvres described in paragraphs 6.9.4.1 and 6.9.4.2, above, should be conducted using the following configurations and procedures:

a. The "Holding Ice" accretion should be used. For aeroplanes with unpowered elevators, these tests should also be performed with "Sandpaper Ice."

b. Medium to light weight, the most critical of aft or forward centre of gravity position, symmetric fuel loading.

c. In the configurations listed below, with the aeroplane in trim, or as nearly as possible in trim, at the specified trim speed, perform a continuous manoeuvre (without changing trim) to reach zero g normal load factor or, if limited by elevator control authority, the lowest load factor obtainable at the target speed.

i. Highest lift landing configuration at idle power or thrust, and the more critical of:

—             Trim speed 1.23 V_SR, target speed not more than 1.23 V_SR, or

—             Trim speed V_FE, target speed not less than V_FE - 37 km/h (20 knots)

ii. Highest lift landing configuration at go-around power or thrust, and the more critical of:

—             Trim speed 1.23 V_SR, target speed not more than 1.23 V_SR, or

—             Trim speed V_FE, target speed not less than V_FE - 37 km/h (20 knots)

d. Conduct steady heading sideslips to full rudder authority, 801 N. (180 lbf) rudder force or full lateral control authority (whichever comes first), with highest lift landing configuration, trim speed 1.23 V_SR, and power or thrust for -3° flight path angle.

6.9.5 Controllability prior to Activation and Normal Operation of the Ice Protection System. The following represents an acceptable test programme for compliance with controllability requirements with the ice accretion prior to activation and normal operation of the ice protection system.

In the configurations, speeds, and power settings listed below, with the ice accretion specified in the requirement, trim the aeroplane at the specified speed. Conduct pull up to 1.5g and pushover to 0.5g without longitudinal control force reversal.

i. High lift devices retracted configuration (or holding configuration if different), holding speed, power or thrust for level flight.

ii. Landing configuration, VREF for non-icing conditions, power or thrust for landing approach (limit pull up to stall warning).

6.10 Longitudinal Control (CS 25.145).

6.10.1 No specific quantitative evaluations are required for demonstrating compliance with CS 25.145(b) and (c). Qualitative evaluations should be combined with the other testing. The results from the non-contaminated aeroplane tests should be reviewed to determine whether there are any cases where there was marginal compliance. If so, these cases should be repeated with ice.

6.10.2 Acceptable Test Programme. The following represents an acceptable test programme for compliance with CS 25.145(a):

a. The "Holding ice" accretion should be used.

b. Medium to light weight, aft centre of gravity position, symmetric fuel loading.

c. In the configurations listed below, trim the aeroplane at 1.3 V_SR.  Reduce speed using elevator control to stall warning plus one second and demonstrate prompt recovery to the trim speed using elevator control.

i. High lift devices retracted configuration, maximum continuous power or thrust.

ii. Maximum lift landing configuration, maximum continuous power or thrust.

6.11 Directional and Lateral Control (CS 25.147). Qualitative evaluations should be combined with the other testing. The results from the non-contaminated aeroplane tests should be reviewed to determine whether there are any cases where there was marginal compliance. If so, these cases should be repeated with ice.

6.12 Trim (CS 25.161).

6.12.1 Qualitative evaluations should be combined with the other testing. The results from the non-contaminated aeroplane tests should be reviewed to determine whether there are any cases where there was marginal compliance. If so, these cases should be repeated with ice. In addition a specific check should be made to demonstrate compliance with CS 25.161(c)(2).

6.12.2 The following represents a representative test program for compliance with 25.161(c)(2).

a. The "Holding ice" accretion should be used.

b. Most critical landing weight, forward centre of gravity position, symmetric fuel loading.

c. In the configurations below, trim the aircraft at the specified speed.

i. Maximum lift landing configuration, landing gear extended, and the most critical of:

—             Speed 1.3V_SR1 with Idle power or thrust; or,

—             Speed V_REF with power or thrust corresponding to a 3 deg glidepath'

6.13 Stability - General (CS 25.171). Qualitative evaluations should be combined with the other testing.  Any tendency to change speed when trimmed or requirement for frequent trim inputs should be specifically investigated.

6.14 Demonstration of Static Longitudinal Stability (CS 25.175).

6.14.1 Each of the following cases should be tested. In general, it is not necessary to test the cruise configuration at low speed (CS 25.175(b)(2)) or the cruise configuration with landing gear extended (CS 25.175(b)(3)); nor is it necessary to test at high altitude. The maximum speed for substantiation of stability characteristics in icing conditions (as prescribed by CS 25.253(c)) is the lower of 556 km/h (300 knots) CAS, V_FC, or a speed at which it is demonstrated that the airframe will be free of ice accretion due to the effects of increased dynamic pressure.

6.14.2 Acceptable Test Programme. The following represents an acceptable test programme for demonstration of static longitudinal stability:

a. The "Holding ice" accretion should be used.

b. High landing weight, aft centre of gravity position, symmetric fuel loading.

c. In the configurations listed below, trim the aeroplane at the specified speed. The power or thrust should be set and stability demonstrated over the speed ranges as stated in CS 25.175(a) through (d), as applicable.

i.  Climb:  With high lift devices retracted, trim at the speed for best rate-of-climb, except that the speed need not be less than 1.3 VSR.

ii. Cruise: With high lift devices retracted, trim at V_MO or 463 km/h (250 knots) CAS, whichever is lower.

iii. Approach: With the high lift devices in the approach position appropriate to the highest lift landing configuration, trim at 1.3 V_SR.

iv. Landing: With the highest lift landing configuration, trim at 1.3V_SR.

6.15 Static Directional and Lateral Stability (CS 25.177).

6.15.1 Compliance should be demonstrated using steady heading sideslips to show compliance with directional and lateral stability. The maximum sideslip angles obtained should be recorded and may be used to substantiate a crosswind value for landing (see paragraph 6.19 of this AMC).

6.15.2 Acceptable Test Programme. The following represents an acceptable test programme for static directional and lateral stability:

a. The "Holding ice" accretion should be used.

b. Medium to light weight, aft centre of gravity position, symmetric fuel loading.

c. In the configurations listed below, trim the aeroplane at the specified speed and conduct steady heading sideslips to full rudder authority, 801 N. (180 lbf) rudder pedal force, or full lateral control authority, whichever comes first.

i. High lift devices retracted configuration:  Trim at best rate-of-climb speed, but need not be less than 1.3 V_SR.

ii. Lowest lift take-off configuration:  Trim at the all-engines-operating initial climb speed.

iii. Highest lift landing configuration:  Trim at V_REF.

6.16 Dynamic Stability (CS 25.181). Provided that there are no marginal compliance aspects with the non-contaminated aeroplane, it is not necessary to demonstrate dynamic stability in specific tests. Qualitative evaluations should be combined with the other testing. Any tendency to sustain oscillations in turbulence or difficulty in achieving precise attitude control should be investigated.

6.17 Stall Demonstration (CS 25.201).

6.17.1 Sufficient stall testing should be conducted to demonstrate that the stall characteristics comply with the requirements. In general, it is not necessary to conduct a stall programme which encompasses all weights, centre of gravity positions (including lateral asymmetry), altitudes, high lift configurations, deceleration device configurations, straight and turning flight stalls, power off and power on stalls. Based on a review of the stall characteristics of the non-contaminated aeroplane, a reduced test matrix can be established. However, additional testing may be necessary if:

—             the stall characteristics with ice accretion show a significant difference from the non-contaminated aeroplane,

—             testing indicates marginal compliance, or

—             a stall identification system (e.g. stick pusher) is required to be reset for icing conditions.

6.17.2  Acceptable Test Programme. Turning flight stalls at decelerations greater than 1 knot/sec are not required.  Slow decelerations (much slower than 1 knot/sec) may be critical on aeroplanes with anticipation logic in their stall protection system or on aeroplanes with low directional stability, where large sideslip angles could develop. The following represents an acceptable test programme subject to the provisions outlined above.

a. The "Holding ice" accretion should be used.

b. Medium to light weight, aft centre of gravity position, symmetric fuel loading.

c. Normal stall test altitude.

d. In the configurations listed below, trim the aeroplane at the same initial stall speed factor used for stall speed determination. For power-on stalls, use the power setting as defined in CS 25.201 (a)(2) but with ice accretions on the aeroplane. Decrease speed at a rate not to exceed 1 knot/sec to stall identification and recover using the same test technique as for the non-contaminated aeroplane.

i. High lift devices retracted configuration: Straight/Power Off, Straight/Power On, Turning/Power Off, Turning/Power On.

ii. Lowest lift take-off configuration: Straight/Power On, Turning/Power Off.

iii. Highest lift take-off configuration: Straight/Power Off, Turning/Power On.

iv. Highest lift landing configuration: Straight/Power Off, Straight/Power On, Turning/Power Off, Turning/Power On.

e. For the configurations listed in paragraph 6.17.2(d)i and iv, and any other configuration if deemed more critical, in 1 knot/second deceleration rates down to stall warning with wings level and power off, roll the aeroplane left and right up to 10 degrees of bank using the lateral control.

6.18 Stall Warning (CS 25.207).

6.18.1 Stall warning should be assessed in conjunction with stall speed testing and stall demonstration testing (CS 25.103, CS 25.201 and paragraphs 6.2 and 6.17 of this AMC, respectively) and in tests with faster entry rates.

6.18.2 Normal Ice Protection System Operation. The following represents an acceptable test programme for stall warning in slow down turns of at least 1.5g and at entry rates of at least 1 m/sec² (2 knot/sec):

a. The "Holding ice" accretion should be used.

b. Medium to light weight, aft centre of gravity position, symmetric fuel loading.

c. Normal stall test altitude.

d. In the configurations listed below, trim the aeroplane at 1.3V_SR with the power or thrust necessary to maintain straight level flight. Maintain the trim power or thrust during the test demonstrations.  Increase speed as necessary prior to establishing at least 1.5g and a deceleration of at least 1 m/sec² (2 knot/sec). Decrease speed until 1 sec after stall warning and recover using the same test technique as for the non-contaminated aeroplane.

i. High lift devices retracted configuration;

ii. Lowest lift take-off configuration; and

iii. Highest lift landing configuration.

6.18.3 Ice Accretion Prior to Activation and Normal System Operation. The following represent acceptable means for evaluating stall warning margin with the ice accretion prior to activation and normal operation of the ice protection system.

a. In the configurations listed below, with the ice accretion specified in the requirement, trim the aeroplane at 1.3 V_SR.

i. High lift devices retracted configuration: Straight/Power Off.

ii. Landing configuration: Straight/Power Off.

b. At decelerations of up to 0.5 m/sec² (1 knot per second), reduce the speed to stall warning plus 1 second, and demonstrate that stalling can be prevented using the same test technique as for the non-contaminated aeroplane, without encountering any adverse characteristics (e.g., a rapid roll-off). As required by CS 25.207(h)(3)(ii), where stall warning is provided by a different means than for the aeroplane without ice accretion, the stall characteristics must be satisfactory and the delay must be at least 3 seconds.

6.19 Wind Velocities (CS 25.237).

6.19.1 Crosswind landings with "Landing Ice" should be evaluated on an opportunity basis.

6.19.2 The results of the steady heading sideslip tests with “Landing Ice” may be used to establish the safe cross wind component. If the flight test data show that the maximum sideslip angle demonstrated is similar to that demonstrated with the non-contaminated aeroplane, and the flight characteristics (e.g. control forces and deflections) are similar, then the non-contaminated aeroplane crosswind component is considered valid.

6.19.3 If the results of the comparison discussed in paragraph 6.19.2, above, are not clearly similar, and in the absence of a more rational analysis, a conservative analysis based on the results of the steady heading sideslip tests may be used to establish the safe crosswind component. The crosswind value may be estimated from:

V_CW = V_{REF  *} sin (sideslip angle) / 1.5

Where:

V_CW is the crosswind component,

V_REF  is the landing reference speed appropriate to a minimum landing weight, and sideslip angle is that demonstrated at V_REF (see paragraph 6.15 of this AMC).

6.20 Vibration and Buffeting (CS 25.251).

6.20.1 Qualitative evaluations should be combined with the other testing, including speeds up to the maximum speed obtained in the longitudinal stability tests (see paragraph 6.14 of this AMC).

6.20.2 It is also necessary to demonstrate that the aeroplane is free from harmful vibration due to residual ice accumulation.  This may be done in conjunction with the natural icing tests.

6.20.3 An aeroplane with pneumatic de-icing boots should be evaluated to V_DF/M_DF with the de-icing boots operating and not operating.  It is not necessary to do this demonstration with ice accretion.

6.21 Natural Icing Conditions.

6.21.1 General.

6.21.1.1 Whether the flight testing has been performed with artificial ice shapes or in natural icing conditions, additional limited flight testing described in this section should be conducted in natural icing conditions specified in Appendix C to CS-25 and, if necessary, in the icing conditions described in Appendix O to CS-25. (AMC 25.1420 provides guidance on when it is necessary to perform flight testing in the atmospheric icing conditions of Appendix O.) Where flight testing with artificial ice shapes is the primary means for showing compliance, the objective of the tests described in this section is to corroborate the handling characteristics and performance results obtained in flight testing with artificial ice shapes.

6.21.1.2 It is acceptable for some ice to be shed during the testing due to air loads or wing flexure, etc.  However, an attempt should be made to accomplish the test manoeuvres as soon as possible after exiting the icing cloud to minimise the atmospheric influences on ice shedding.

6.21.1.3 During any of the manoeuvres specified in paragraph 6.21.2, below, the behaviour of the aeroplane should be consistent with that obtained with artificial ice shapes. There should be no unusual control responses or uncommanded aeroplane motions. Additionally, during the level turns and bank-to-bank rolls, there should be no buffeting or stall warning.

6.21.2 Ice Accretion/Manoeuvres.

6.21.2.1 Holding scenario.

a. The manoeuvres specified in Table 3, below, should be carried out with the following ice accretions representative of normal operation of the ice protection system:

i. On unprotected Parts: A thickness of 75 mm (3 inches) on those parts of the aerofoil where the collection efficiency is highest should be the objective. (A thickness of 50 mm (2 inches) is normally a minimum value, unless a lesser value is agreed by the Agency.)

ii. On protected parts: The ice accretion thickness should be that resulting from normal operation of the ice protection system.

b. For aeroplanes with control surfaces that may be susceptible to jamming due to ice accretion (e.g. elevator horns exposed to the air flow), the holding speed that is critical with respect to this ice accretion should be used.

Table 3: Holding Scenario – Manoeuvres

Configuration	Centre of Gravity Position	Trim speed	Manoeuvre
Flaps up, gear up	Optional (aft range)	Holding, except 1.3 VSR for the stall manoeuvre	Level, 40° banked turn, Bank-to-bank rapid roll, 30° - 30°, Speedbrake extension, retraction, Full straight stall (1 knot/second deceleration rate, wings level, power off).
Flaps in intermediate positions, gear up	Optional (aft range)	1.3 VSR	Deceleration to the speed reached 3 seconds after activation of stall warning in a 1 knot/second deceleration.
Landing flaps, gear down	Optional (aft range)	VREF	Level, 40° banked turn, Bank-to-bank rapid roll, 30° - 30°, Speedbrake extension, retraction (if approved), Full straight stall (1 knot/second deceleration rate, wings level, power off).

6.21.2.2 Approach/Landing Scenario. The manoeuvres specified in Table 4, below, should be carried out with successive accretions in different configurations on unprotected surfaces. Each test condition should be accomplished with the ice accretion that exists at that point. The final ice accretion (Test Condition 3) represents the sum of the amounts that would accrete during a normal descent from holding to landing in icing conditions.

TABLE 4: Approach/Landing Scenario – Manoeuvres

Test Condition	Ice accretion thickness (*)	Configuration	Centre of Gravity Position	Trim speed	Manoeuvre
_	First 13 mm (0.5 in.)	Flaps up, gear up	Optional (aft range)	Holding	No specific test
1	Additional 6.3 mm (0.25 in.) (19 mm (0.75 in.) total)	First intermediate flaps, gear up	Optional (aft range)	Holding	-Level 40° banked turn, -Bank-to-bank rapid roll, 30°- 30°, -Speed brake extension and retraction (if approved), -Deceleration to stall warning.
2	Additional 6.3 mm (0.25 in.) (25 mm (1.00 in.) total)	Further intermediate flaps, gear up (as applicable)	Optional (aft range)	1.3 VSR	-Bank-to-bank rapid roll, 30° - 30°, -Speed brake extension and retraction (if approved), -Deceleration to stall warning.
3	Additional 6.3 mm (0.25 in.) (31 mm (1.25 in.) total)	Landing flaps, gear down	Optional  (aft range)	VREF	-Bank-to-bank rapid roll, 30° - 30°, -Speed brake extension and retraction (if approved), -Bank to 40°, -Full straight stall.

(*) The indicated thickness is that obtained on the parts of the unprotected aerofoil with the highest collection efficiency.

6.21.3  For aeroplanes with unpowered elevator controls, in the absence of an agreed substantiation of the criticality of the artificial ice shape used to demonstrate compliance with the controllability requirement, the pushover test of paragraph 6.9.4 should be repeated with a thin accretion of natural ice on the unprotected surfaces.

6.21.4  Existing propeller speed limits or, if required, revised propeller speed limits for flight in icing, should be verified by flight tests in natural icing conditions.

6.22 Failure Conditions (CS 25.1309).

6.22.1 For failure conditions which are annunciated to the flight crew, credit may be taken for the established operating procedures following the failure.

6.22.2 Acceptable Test Programme.  In addition to a general qualitative evaluation, the following test programme (modified as necessary to reflect the specific operating procedures) should be carried out for the most critical probable failure condition where the associated procedure requires the aeroplane to exit the icing condition:

a. The ice accretion is defined as a combination of the following:

i. On the unprotected surfaces - the “Holding ice” accretion described in paragraph A1.2.1 of this AMC;

ii. On the normally protected surfaces that are no longer protected - the “Failure ice” accretion described in paragraph A1.3.2 of this AMC; and

iii. On the normally protected surfaces that are still functioning following the segmental failure of a cyclical de-ice system – the ice accretion that will form during the rest time of the de-ice system following the critical failure condition.

b. Medium to light weight, aft centre of gravity position, symmetric fuel loading.

c. In the configurations listed below, trim the aeroplane at the specified speed. Conduct 30° banked turns left and right with normal reversals. Conduct pull up to 1.5g and pushover to 0.5g.

i. High lift devices retracted configuration (or holding configuration if different): Holding speed, power or thrust for level flight.  In addition, deploy and retract deceleration devices.

ii. Approach configuration: Approach speed, power or thrust for level flight.

iii. Landing configuration: Landing speed, power or thrust for landing approach (limit pull up to 1.3g). In addition, conduct steady heading sideslips to angle of sideslip appropriate to type and landing procedure.

d. In the configurations listed below, trim the aeroplane at estimated 1.3 V_SR Decrease speed to stall warning plus 1 second, and demonstrate prompt recovery using the same test technique as for the non-contaminated aeroplane. Natural stall warning is acceptable for the failure case.

i. High lift devices retracted configuration: Straight/Power Off.

ii. Landing configuration: Straight/Power Off.

e. Conduct an approach and go-around with all engines operating using the recommended procedure.

f. Conduct an approach and landing with all engines operating (unless the one-engine-inoperative condition results in a more critical probable failure condition) using the recommended procedure.

6.22.3  For improbable failure conditions, flight test may be required to demonstrate that the effect on safety of flight (as measured by degradation in flight characteristics) is commensurate with the failure probability or to verify the results of analyses and/or wind tunnel tests. The extent of any required flight test should be similar to that described in paragraph 6.22.2, above, or as agreed with the Agency for the specific failure condition.

[Amdt No: 25/3]

[Amdt No: 25/6]

[Amdt No: 25/13]

[Amdt No: 25/16]

[Amdt No: 25/18]

[Amdt No: 25/21]

Appendix 1 – Airframe Ice Accretion

ED Decision 2016/010/R

A1.1 General.

a.  In accordance with CS 25.1419, each aeroplane certified for flight in icing conditions must be capable of safely operating in the continuous maximum and intermittent maximum icing conditions of Appendix C. Therefore, at a minimum, certification for flight in icing conditions must include consideration of ice accretions that can occur in Appendix C icing conditions.

b.  In accordance with CS 25.1420(a)(1), each aeroplane certified for flight in icing conditions must, at a minimum, be capable of safely operating:

i.  In the atmospheric icing conditions of Appendix C to CS-25, and

ii.  After encountering the atmospheric icing conditions of Appendix O, and subsequently while exiting all icing conditions.

Therefore, at a minimum, certification for flight in icing conditions must consider ice accretions that can occur during flight in Appendix C icing conditions and during detection and exiting of Appendix O icing conditions.

c.  In accordance with CS 25.1420(a)(2), an aeroplane may also be certified for operation in a portion of the atmospheric icing conditions of Appendix O to CS-25. In that case, the aeroplane must also be capable of operating safely after encountering, and while exiting, atmospheric icing conditions in the portion of Appendix O for which operation is not approved. Ice accretions used for certification must consider:

i.  Operations in Appendix C icing conditions,

ii.  Operations in the Appendix O icing conditions for which approval is sought, and

iii.  Detection and exiting of the Appendix O icing conditions beyond those for which approval is sought.

d.  In accordance with CS 25.1420(a)(3), in addition to being certified for flight in Appendix C conditions, an aeroplane may be certified for operation throughout the atmospheric icing conditions of Appendix O to CS-25. Certification for flight throughout the atmospheric icing conditions of Appendix O must consider ice accretions resulting from:

i. Operations in Appendix C icing conditions, and

ii.  Operations in Appendix O icing conditions.

e.  The CS-25 subpart B aeroplane performance and handling characteristics requirements identify the specific ice accretions that apply in showing compliance. In accordance with Appendix C, part II(b) and Appendix O, part II(e), to reduce the number of ice accretions used for demonstrating compliance, the applicant may use any of the applicable ice accretions (or a composite accretion representing a combination of accretions) to show compliance with a particular subpart B requirement if that accretion is either the ice accretion identified in the requirement or is shown to be more conservative than the ice accretion identified in the requirement. In addition, the ice accretion with the most adverse effect on handling characteristics may be used for compliance with the aeroplane performance requirements if any difference in performance is conservatively taken into account. Ice accretion(s) used to show compliance should take into account the speeds, configurations (including configuration changes), angles of attack, power or thrust settings, etc. for the flight phases and icing conditions they are intended to cover.

f.  The applicant should determine the most critical ice accretion in terms of handling characteristics and performance for each flight phase. Parameters to be considered include:

—             flight conditions (for example, aeroplane configuration, speed, angle-of-attack, altitude) and

—             atmospheric icing conditions for which certification is desired (for example, temperature, liquid water content (LWC), mean effective drop diameter (MED), drop median volume diameter (MVD)).

  If a comparative analysis (refer to AMC 25.1420(f)) is used as the means of compliance with the CS-25 certification specifications relative to the Appendix O icing conditions, the most critical ice accretions determined for Appendix C icing conditions are acceptable.

g.  For each phase of flight, the shape, chordwise and spanwise, and the roughness of the shapes, considered in selection of a critical ice shape should accurately reflect the full range of atmospheric icing conditions for which certification is desired in terms of MED, LWC, MVD, and temperature during the respective phase of flight. Justification and selection of the most critical ice shape for each phase of flight should be agreed to by the Agency.

h.  See Appendix R of FAA Advisory Circular AC 20-73A, Aircraft Ice Protection, for additional detailed information about determining the applicable critical ice accretion (shape and roughness).

A1.2 Operative Ice Protection System.

A1.2.1 All flight phases except take-off.

A1.2.1.1 For unprotected parts, the ice accretion to be considered should be determined in accordance with Appendices C and O to CS-25.

A1.2.1.2 Unprotected parts consist of the unprotected aerofoil leading edges and all unprotected airframe parts on which ice may accrete. The effect of ice accretion on protuberances such as antennae or flap hinge fairings need not normally be investigated. However aeroplanes that are characterised by unusual unprotected airframe protuberances, e.g. fixed landing gear, large engine pylons, or exposed control surface horns or winglets, etc., may experience significant additional effects, which should therefore be taken into consideration.

A1.2.1.3 For holding ice, the applicant should determine the effect of a 45‑minute hold in continuous maximum icing conditions. The analysis should assume that the aeroplane remains in a rectangular “race track” pattern, with all turns being made within the icing cloud. Therefore, no horizontal extent correction should be used for this analysis. For some previous aeroplane certification programs, the maximum pinnacle height was limited to 75 mm (3 inches). This method of compliance may continue to be accepted for follow-on products if service experience has been satisfactory, and the designs are similar enough to conclude that the previous experience is applicable. The applicant should substantiate the critical mean effective drop diameter, liquid water content, and temperature that result in the formation of an ice accretion that is critical to the aeroplane’s performance and handling qualities. The shape and texture of the ice are important and should be agreed with the Agency.

A1.2.1.4 For protected parts, the ice protection systems are normally assumed to be operative. However, the applicant should consider the effect of ice accretion on the protected surfaces that result from:

a. The rest time of a de-icing cycle. Performance may be established on the basis of a representative intercycle ice accretion for normal operation of the de-icing system (consideration should also be given to the effects of any residual ice accretion that is not shed.) The average drag increment determined over the de-icing cycle may be used for performance calculations.

b. Runback ice which occurs on or downstream of the protected surface.

c. Ice accretion prior to activation and normal operation of the ice protection system (see paragraph A1.2.3, below).

A1.2.2 Take-off phase.

A1.2.2.1 For both unprotected and protected parts, the ice accretion identified in Appendix C and Appendix O to CS-25 for the take-off phase may be determined by calculation, assuming the following:

—             aerofoils, control surfaces and, if applicable, propellers are free from frost, snow, or ice at the start of the take-off;

—             the ice accretion starts at the end of the take-off distance

—             the critical ratio of thrust/power-to-weight;

—             failure of the critical engine occurs at VEF; and

—             flight crew activation of the ice protection system in accordance with an AFM procedure, except that after commencement of the take-off roll no flight crew action to activate the ice protection system should be assumed to occur until the aeroplane is 122 m (400 ft) above the take-off surface.

A1.2.2.2 The ice accretions identified in Appendix C and Appendix O to CS-25 for the take-off phase are:

—             "Take-off ice": The most critical ice accretion between the end of the take-off distance and 122 m (400 ft) above the takeoff surface, assuming accretion starts at the end of the take-off distance in the icing environment.

—             "Final Take-off ice": The most critical ice accretion between 122 m (400 ft) ) and the height at which the transition to the en route configuration and speed is completed, or 457 m (1500 ft) above the take-off surface, whichever is higher, assuming accretion starts at the end of the take-off distance in the icing environment.

A1.2.3 Ice accretion prior to activation and normal system operation.

A1.2.3.1 When considering ice accretion before the ice protection system has been activated and is performing its intended function, the means of activating the ice protection system and the system response time should be taken into account. System response time is defined as the time interval between activation of the system and its effective operation (for example, for a thermal ice protection system used for de-icing, the time to heat the surface and perform its de-icing function).

If activation of the ice protection system depends on flight crew recognition of icing conditions or response to a cockpit annunciation, appropriate delays in identifying the icing conditions and activating the ice protection system should be taken into account. For the icing conditions of Appendix C, the aeroplane should be assumed to be in continuous maximum icing conditions during the time between entering the icing conditions and effective operation of the ice protection system.

A1.2.3.2 For an aeroplane certified in accordance with CS 25.1420 (a)(2) or (a)(3), the requirements of CS 25.1419 (e), (f), (g), and (h) must be met for the icing conditions defined in Appendix O in which the aeroplane is certified to operate.

 CS 25.1419(e) requires one of the following three methods for detecting icing and activating the airframe ice protection system:

(a) A primary ice detection system that automatically activates or that alerts the flight crew to activate the airframe ice protection system; or

(b) A definition of visual cues for recognition of the first sign of ice accretion on a specified surface combined with an advisory ice detection system that alerts the flight crew to activate the airframe ice protection system; or

(c) Identification of conditions conducive to airframe icing as defined by an appropriate static or total air temperature and visible moisture for use by the flight crew to activate the airframe ice protection system.

A1.2.3.3 The following guidance should be used to determine the ice accretion on the unprotected and protected aerodynamic surfaces before activation and normal system operation of the ice protection system.

a. If the ice protection system activates automatically after annunciation from a primary ice detection system, the assumed ice accretion should take into account the time it takes for automatic activation of the ice protection system and the time it takes for the system to perform its intended function. The assumed ice accretion can be determined as follows:

i. The ice accretion on the protected surfaces corresponding to the time between entry into the icing conditions and activation of the system, plus

ii. The ice accretion during the system response time.

b. If ice protection system activation depends on pilot action following annunciation from a primary ice detection system, the assumed ice accretion should take into account flight crew delays in activating the ice protection system and the time it takes for the system to perform its intended function. The assumed ice accretion can be determined as follows:

i. The ice accretion corresponding to the time between entry into the icing conditions and annunciation from the primary ice detection system, plus

ii. The ice accretion corresponding to 10 additional seconds of operation in icing conditions, plus

iii. The ice accretion during the system response time.

c. If ice protection system activation depends on the flight crew visually recognizing the first indication of ice accretion on a reference surface (for example, an ice accretion probe) combined with an advisory ice detection system, the assumed ice accretion should take into account flight crew delays in detecting the accreted ice and in activating the ice protection system, and the time it takes for the system to perform its intended function. This may be determined as follows:

i. The ice accretion that would be easily recognizable by the flight crew under all foreseeable conditions (for example, at night in clouds) as it corresponds to the first indication of ice accretion on the reference surface, plus

ii. the ice accretion equivalent to 30 seconds of operation in icing conditions, plus

iii. the ice accreted during the system response time.

d. If ice protection system activation depends on pilot identification of icing conditions (as defined by an appropriate static or total air temperature in combination with visible moisture conditions) with or without an advisory ice detector, the assumed ice accretion should take into account flight crew delays in recognizing the presence of icing conditions and flight crew delays in activating the ice protection system, and the time it takes for the system to perform its intended function. This may be determined as follows:

i. the ice accretion equivalent to 30 seconds of operation in icing conditions, plus

ii. the ice accretion during the system response time.

A1.3 Ice Protection System Failure Cases.

A1.3.1 Unprotected parts. The same accretion as in paragraph A1.2.1 is applicable.

A1.3.2 Protected parts following system failure. "Failure Ice" is defined as follows:

A1.3.2.1 In the case where the failure condition is not annunciated, the ice accretion on normally protected parts where the ice protection system has failed should be the same as the accretion specified for unprotected parts.

A1.3.2.2 In the case where the failure condition is annunciated and the associated procedure does not require the aeroplane to exit icing conditions, the ice accretion on normally protected parts where the ice protection system has failed should be the same as the accretion specified for unprotected parts.

A1.3.2.3 In the case where the failure condition is annunciated and the associated procedure requires the aeroplane to exit icing conditions as soon as possible, the ice accretion on normally protected parts where the ice protection has failed, should be taken as one-half of the accretion specified for unprotected parts unless another value is agreed by the Agency.

A1.4 Additional guidance for Appendix O ice accretions.

A1.4.1 Ice Accretion in Appendix O Conditions Before those Conditions Have Been Detected by the Flight crew.

This ice accretion, defined as pre-detection ice in Appendix O, part II(b)(5), refers to the ice accretion existing at the time the flight crew become aware that they are in Appendix O icing conditions and have taken action to begin exiting from all icing conditions.

a.  Both direct entry into Appendix O icing conditions and entry into Appendix O icing conditions from flight in Appendix C icing conditions should be considered.

b.  The time that the applicant should assume it will take to detect Appendix O icing conditions exceeding those for which the aeroplane is certified should be based on the means of detection. AMC 25.1419 and AMC 25.1420 provide guidance for certifying the detection means. In general, the Agency expects that the time to detect exceedance icing conditions may be significantly longer for a detection means relying on the flight crew seeing and recognizing a visual icing cue than it is for an ice detection system that provides an attention-getting alert to the flight crew.

c.  Visual detection requires time for accumulation on the reference surface(s) of enough ice to be reliably identified by either pilot in all atmospheric and lighting conditions. Time between pilot scans of reference surface(s) should be considered.

i.  The amount of ice needed for reliable identification is a function of the distinguishing characteristics of the ice (for example, size, shape, contrast compared to the surface feature that it is adhered to), the distance from the pilots (for example, windshield vs. engine vs. wingtip), and the relative viewing angle (location with respect to the pilots’ primary fields of view).

ii.  Pilot scan time of the reference surface(s) will be influenced by many factors. Such factors include phase of flight, workload, frequency of occurrence of Appendix O conditions, pilot awareness of the possibility of supercooled large drop conditions, and ease of seeing the reference surface(s). The infrequency of Appendix O conditions (approximately 1 in 100 to 1 in 1 000, on average in all worldwide icing encounters) and the high workload associated with some phases of flight in instrument conditions (for example, approach and landing) justify using a conservative estimate for the time between pilot scans.

iii.  In the absence of specific studies or tests validating visual detection times, the following times should be used for visual detection of exceedance icing conditions following accumulation of enough ice to be reliably identified by either pilot in all atmospheric and lighting conditions:

1.  For a visual reference located on or immediately outside a cockpit window (for example, ice accretions on side windows, windshield wipers, or icing probe near the windows) – 3 minutes.

2.  For a visual reference located on a wing, wing mounted engine, or wing tip – 5 minutes.

A1.4.2 Ice Accretions for Encounters with Appendix O Conditions Beyond those in Which the Aeroplane is Certified to Operate.

a.  Use the ice accretions in Table 1, below, to evaluate compliance with the applicable CS-25 subpart B requirements for operating safely after encountering Appendix O atmospheric icing conditions for which the aeroplane is not approved, and then safely exiting all icing conditions.

b.  The ice accretions of Table 1 apply when the aeroplane is not certified for flight in any portion of Appendix O atmospheric icing conditions, when the aeroplane is certified for flight in only a portion of Appendix O conditions, and for any flight phase for which the aeroplane is not certified for flight throughout the Appendix O icing envelope.

c.  Table 1 shows the scenarios to be used for determining ice accretions for certification testing of encounters with Appendix O conditions beyond those in which the aeroplane is certified to operate (for detecting and exiting those conditions):

Table 1

Flight Phase/Condition -	Appendix O Detect-and-Exit Ice Accretion
Ground Roll	No accretion
Take-off	No accretion1
Final Take-off	No accretion1
En Route	En Route Detect-and-Exit Ice Combination of: (1) either Appendix C en route ice or Appendix O en route ice for which approval is sought, whichever is applicable, (2) pre-detection ice, (3) accretion from one standard cloud horizontal extent (32.2 km (17.4 nautical miles)) in Appendix O conditions for which the aeroplane is not approved, and (4) accretion from one standard cloud horizontal extent (32.2 km (17.4 nautical miles)) in Appendix C continuous maximum icing conditions.
Holding	Holding Detect-and-Exit Ice Combination of: (1) either Appendix C holding ice or Appendix O holding ice for which approval is sought, whichever is applicable, (2) pre-detection ice, (3) accretion from one standard cloud horizontal extent (32.2 km (17.4 nautical miles)) in Appendix O conditions for which the aeroplane is not approved, and (4) accretion from one standard cloud horizontal extent (32.2 km (17.4 nautical miles)) in Appendix C continuous maximum icing conditions. The total time in icing conditions need not exceed 45 minutes.
Approach	Approach Detect-and-Exit Ice The more critical of holding detect-and-exit ice or the combination of: (1) ice accreted during a descent in the cruise configuration from the maximum vertical extent of the Appendix C continuous maximum icing conditions or the Appendix O icing environment for which approval is sought, whichever is applicable, to 610 m (2 000 feet) above the landing surface, where transition to the approach configuration is made, (2) pre-detection ice, and (3) ice accreted at 610 m (2 000 feet) above the landing surface while transiting one standard cloud horizontal extent (32.2 km (17.4 nautical miles)) in Appendix O conditions for which the aeroplane is not approved and one standard cloud horizontal extent (32.2 km (17.4 nautical miles)) in Appendix C continuous maximum icing conditions.
Landing	Landing Detect-and-Exit Ice The more critical of holding detect-and-exit ice or the combination of: (1) either Appendix C or Appendix O approach and landing ice for which approval is sought, whichever is applicable, (2) pre-detection ice, and (3) ice accreted during an exit maneuver beginning with the minimum climb gradient specified in CS 25.119 from a height of 61 m (200 feet) above the landing surface and transiting through one standard cloud horizontal extent (32.2 km (17.4 nautical miles)) in Appendix O conditions for which the aeroplane is not approved, and one standard cloud horizontal extent (32.2 km (17.4 nautical miles)) in Appendix C continuous maximum icing conditions. For the purposes of defining the landing detect-and-exit ice shape, the Appendix C approach and landing ice is defined as the ice accreted during: —             a descent in the cruise configuration from the maximum vertical extent of the Appendix C continuous maximum icing environment to 610 m (2 000 feet) above the landing surface, —             a transition to the approach configuration and manoeuvring for 15 minutes at 610 m (2 000 feet) above the landing surface, and —             a descent from 610 m (2 000 feet) to 61 m (200 feet) above the landing surface with a transition to the landing configuration.
Ice Accretion Before the Ice Protection System Has Been Activated and is Performing its Intended Function	Ice accreted on protected and unprotected surfaces during the time it takes for icing conditions (either Appendix C or Appendix O) to be detected, the ice protection system to be activated, and the ice protection system to become fully effective in performing its intended function.
Ice Accretion in Appendix O Conditions Before Those Conditions Have Been Detected by the Flight crew and Actions Taken, in Accordance With the AFM, to Either Exit All Icing Conditions or Continue Flight in Appendix O Icing Conditions	Ice accreted on protected and unprotected surfaces during: —             the time it takes to detect and identify Appendix O conditions (based on the method of detection) beyond those in which the aeroplane is certified to operate, and —             the time it takes the flight crew to refer to and act on procedures, including coordinating with Air Traffic Control, to exit all icing conditions. —             a minimum time period of two minutes should be used as the time needed for the flight crew to refer to and act on the procedures to exit all icing conditions after the Appendix O icing conditions are recognised.
Failures of the Ice Protection System	No accretion2

Notes:

¹  Intentional flight, including Take-off, is not permitted into Appendix O conditions beyond those in which the aeroplane is certified to operate.

²  It is not necessary to consider an unintentional encounter with Appendix O icing conditions beyond those in which the aeroplane is certified to operate while operating with a failed ice protection system.

A1.4.3 Ice Accretions for Encounters with Appendix O Atmospheric Icing Conditions in Which the Aeroplane is Certified to Operate.

a.  The applicant should use the ice accretions in Table 2 to evaluate compliance with the applicable CS-25 subpart B requirements for operating safely in the Appendix O atmospheric icing conditions for which approval is sought.

b.  The decision about which ice accretions to use should include consideration of combinations of Appendix C and Appendix O icing conditions within the scenarios defined in paragraph A1.4.3(c) of this appendix. For example, flight in Appendix O conditions may result in ice accumulating, and potentially forming a ridge, behind a protected surface. Once this accretion site has been established, flight in Appendix C icing conditions for the remaining portion of the applicable flight phase scenario may result in a more critical additional accretion than would occur for continued flight in Appendix O icing conditions.

c.  Table 2 shows the scenarios the applicant should use for determining ice accretions for certification for flight in the icing conditions of Appendix O to CS-25.

Table 2

Flight Phase/Condition	Appendix O Ice Accretion
Ground Roll	No accretion
Take-off	Take-off Ice Ice accretion occurring between the end of the take-off distance and 122 m (400 feet) above the take-off surface assuming ice accretion starts at the end of the take-off distance.
Final Take-off	Final Take-off Ice Ice accretion occurring between a height of 122 m (400 ft) above the take-off surface and the height at which the transition to the en-route configuration and speed is completed, or 457 m (1 500 feet) above the take-off surface, whichever is higher, assuming ice accretion starts at the end of the take-off distance.
En Route	En Route Ice Ice accreted during the en route phase of flight.
Holding	Holding Ice Ice accreted during a 45-minute hold with no reduction for horizontal cloud extent (that is, the hold is conducted entirely within the 32.2 km (17.4 nautical mile) standard cloud extent).
Approach	Approach Ice More critical ice accretion of: (1) Ice accreted during a descent in the cruise configuration from the maximum vertical extent of the Appendix O icing environment to 610 m (2 000 feet) above the landing surface, followed by: —             transition to the approach configuration and —             manoeuvring for 15 minutes at 610 m (2 000 feet) above the landing surface; or (2) Holding ice (if the aeroplane is certified for holding in Appendix O conditions).
Landing	Landing Ice More critical ice accretion of: (1) Approach ice plus ice accreted during descent from 610 m (2 000 feet) above the landing surface to 61 m (200 feet) above the landing surface with: —             a transition to the landing configuration, followed by —             a go-around manoeuvre beginning with the minimum climb gradient specified in CS 25.119 from 61 m (200 feet) to 610 m (2 000 feet) above the landing surface, and —             holding for 15 minutes at 610 m (2 000 feet) above the landing surface in the approach configuration, and —             a descent to the landing surface in the landing configuration, or (2) Holding ice (if the aeroplane is certified for holding in Appendix O conditions).
Ice Accretion Before the Ice Protection System has been Activated and is Performing its Intended Function	Ice accreted during the time it takes for the flight crew to recognise icing conditions and activate the ice protection system, plus the time for the ice protection system to perform its intended function.
Ice Accretion in Appendix O Conditions Before those Conditions have been Detected by the Flight crew and Actions Taken, in Accordance With the AFM, to Either Exit All Icing Conditions or Continue Flight in Appendix O Icing Conditions	Ice accreted during the time it takes for the flight crew to detect Appendix O conditions and refer to and initiate associated procedures, and any time it takes for systems to perform their intended functions (if applicable). Pre-detection ice need not be considered if there are no specific crew actions or systems changes associated with flight in Appendix O conditions.
Failures of the Ice Protection System	Same criteria as for Appendix C (see paragraph A1.3 of this appendix), but in Appendix O conditions.

[Amdt 25/3]

[Amdt 25/16]

[Amdt 25/18]

Appendix 2 – Artificial Ice Shapes

ED Decision 2015/008/R

A2.1 General.

A2.1.1 The artificial ice shapes used for flight testing should be those which have the most adverse effects on handling characteristics. If analytical data show that other reasonably expected ice shapes could be generated which could produce higher performance decrements, then the ice shape having the most adverse effect on handling characteristics may be used for performance tests provided that any difference in performance can be conservatively taken into account.

A2.1.2 The artificial shapes should be representative of natural icing conditions in terms of location, general shape, thickness and texture. Following determination of the form and surface texture of the ice shape under paragraph A2.2, a surface roughness for the shape should be agreed with the Agency as being representative of natural ice accretion.

A2.1.3 "Sandpaper Ice" is addressed in paragraph A2.3.

A2.2 Shape and Texture of Artificial Ice.

A2.2.1 The shape and texture of the artificial ice should be established and substantiated by agreed methods. Common practices include:

—             use of computer codes,

—             flight in measured natural icing conditions,

—             icing wind tunnel tests, and

—             flight in a controlled simulated icing cloud (e.g. from an icing tanker).

A2.2.2 In absence of another agreed definition of texture the following may be used:

—             roughness height:  3 mm

—             particle density:  8 to 10/cm²

A2.3 "Sandpaper Ice."

A2.3.1 "Sandpaper Ice" is the most critical thin, rough layer of ice. Any representation of "Sandpaper Ice" (e.g. carborundum paper no. 40) should be agreed by the Agency.

 A2.3.2 Because sandpaper ice must be considered in the basic icing certification within the Appendix C environmental icing envelope, it does not need to be considered for certification of flight in Appendix O icing conditions.

A2.3.3 The spanwise and chordwise coverage should be consistent with the areas of ice accretion determined for the conditions of CS-25, Appendix C except that, for the zero g pushover manoeuvre of paragraph 6.9.4 of this AMC, the "Sandpaper Ice" may be restricted to the horizontal stabiliser if this can be shown to be conservative.

[Amdt 25/3]

[Amdt 25/16]

Appendix 3 – Design Features

ED Decision 2015/008/R

A3.1 Aeroplane Configuration and Ancestry. An important design feature of an overall aeroplane configuration that can affect performance, controllability and manoeuvrability is its size. In addition, the safety record of the aeroplane's closely-related ancestors may be taken into consideration.

A3.1.1 Size. The size of an aeroplane determines the sensitivity of its flight characteristics to ice thickness and roughness. The relative effect of a given ice height (or ice roughness height) decreases as aeroplane size increases.

A3.1.2 Ancestors. If a closely related ancestor aeroplane was certified for flight in icing conditions, its safety record may be used to evaluate its general arrangement and systems integration.

A3.2 Wing. Design features of a wing that can affect performance, controllability, and manoeuvrability include aerofoil type, leading edge devices and stall protection devices.

A3.2.1 Aerofoil. Aerodynamic effects of ice accretions result mainly from the effects of the ice accretion on the behaviour of the aerofoil’s boundary layer. The boundary layer is the layer of air close to the surface of the aerofoil that is moving across the aerofoil at a velocity lower than the freestream velocity, that is, the velocity of the aerofoil. Ice accretions that occur in areas favourable to keeping the boundary layer attached to the aircraft surface will result in effects that are less aerodynamically adverse than ice accretions that occur in areas less favourable to attached boundary layer conditions. Ice shapes that build up in areas of local airflow deceleration (positively increasing surface pressure), or result in conditions unfavourable to keeping attached flow conditions, as the airflow negotiates the ice surface, will result in the most adverse effects.

A3.2.2 Leading Edge Device. The presence of a leading edge device (such as a slat) reduces the percentage decrease in C_LMAX due to ice by increasing the overall level of C_L. Gapping the slat may improve the situation further. Leading edge devices can also reduce the loss in angle of attack at stall due to ice.

A3.2.3 Stall Protection Device. An aeroplane with an automatic slat-gapping device may generate a greater C_LMAX with ice than the certified C_LMAX with the slat sealed and a non-contaminated leading edge. This may provide effective protection against degradation in stall performance or characteristics.

A3.2.4 Lateral Control. The effectiveness of the lateral control system in icing conditions can be evaluated by comparison with closely related ancestor aeroplanes.

A3.3 Empennage. The effects of size and aerofoil type also apply to the horizontal and vertical tails. Other design features include tailplane sizing philosophy, aerofoil design, trimmable stabiliser, and control surface actuation. Since tails are usually not equipped with leading edge devices, the effects of ice on tail aerodynamics are similar to those on a wing with no leading edge devices. However, these effects usually result in changes to aeroplane handling and/or control characteristics rather than degraded performance.

A3.3.1 Tail Sizing. The effect on aeroplane handling characteristics depends on the tailplane design philosophy. The tailplane may be designed and sized to provide full functionality in icing conditions without ice protection, or it may be designed with a de-icing or anti-icing system.

A3.3.2 Horizontal Stabiliser Design. Cambered aerofoils and trimmable stabilisers may reduce the susceptibility and consequences of elevator hinge moment reversal due to ice-induced tailplane stall.

A3.3.3 Control Surface Actuation. Hydraulically powered irreversible elevator controls are not affected by ice-induced aerodynamic hinge moment reversal.

A3.3.4 Control Surface Size. For mechanical elevator controls, the size of the surface significantly affects the control force due to an ice-induced aerodynamic hinge moment reversal. Small surfaces are less susceptible to control difficulties for given hinge moment coefficients.

A3.3.5 Vertical Stabiliser Design. The effectiveness of the vertical stabiliser in icing conditions can be evaluated by comparison with closely-related ancestor aeroplanes.

A3.4 Aerodynamic Balancing of Flight Control Surfaces. The aerodynamic balance of unpowered or boosted reversible flight control surfaces is an important design feature to consider. The design should be carefully evaluated to account for the effects of ice accretion on flight control system hinge moment characteristics. Closely balanced controls may be vulnerable to overbalance in icing. The effect of ice in front of the control surface, or on the surface, may upset the balance of hinge moments leading to either increased positive force gradients or negative force gradients.

A3.4.1 This feature is particularly important with respect to lateral flight control systems when large aileron hinge moments are balanced by equally large hinge moments on the opposite aileron. Any asymmetric disturbance in flow which affects this critical balance can lead to a sudden uncommanded deflection of the control. This auto deflection, in extreme cases, may be to the control stops.

A3.5 Ice Protection/Detection System. The ice protection/detection system design philosophy may include design features that reduce the ice accretion on the wing and/or tailplane.

A3.5.1 Wing Ice Protection/Detection. A primary ice detection system that automatically activates a wing de-icing or anti-icing system may ensure that there is no significant ice accretion on wings that are susceptible to performance losses with small amounts of ice.

A3.5.1.1 If the wing leading edge is not entirely protected, the part that is protected may be selected to provide good handling characteristics at stall, with an acceptable performance degradation.

A3.5.2 Tail Ice Protection/Detection. A primary ice detection system may automatically activate a tailplane de-icing or anti-icing system on aeroplanes that do not have visible cues for system operation.

A3.5.2.1 An ice protection system on the unshielded aerodynamic balances of aeroplanes with unpowered reversible controls can reduce the risk of ice-induced aerodynamic hinge moment reversal.

[Amdt 25/3]

[Amdt 25/16]

Appendix 4 – Examples of Aeroplane Flight Manual Limitations and Operating Procedures for Operations in Supercooled Large Drop Icing Conditions

ED Decision 2015/008/R

A4.1  Aeroplane approved for flight in Appendix C icing conditions but not approved for flight in Appendix O icing conditions.

a.  AFM Limitations.

Intentional flight, including take-off and landing, into supercooled large drop (SLD) icing conditions, which includes freezing drizzle or freezing rain, is prohibited. If freezing drizzle or freezing rain conditions are encountered, or if [insert cue description here], immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

b.  AFM Operating Procedures (Normal Procedures Section).

Freezing drizzle and freezing rain conditions are severe icing conditions for this aeroplane. Intentional flight, including take-off and landing, into freezing drizzle or freezing rain conditions is prohibited. A flight delay or diversion to an alternate airport is required if these conditions exist at the departure or destination airports.

[insert cue description here] is one indication of severe icing for this aeroplane. If severe icing is encountered, immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

c.  Flight Crew Operating Manual Operating Procedures.

Warning: Hazardous icing effects may result from environmental conditions outside of those for which this aeroplane is certified. Flight into unapproved icing conditions may result in ice build-up on protected surfaces exceeding the capability of the ice protection system, or in ice forming aft of the protected surfaces. This ice might not be shed when using the ice protection systems, and may seriously degrade performance and controllability of the aeroplane.

Operations in icing conditions were evaluated as part of the certification process for this aeroplane. Freezing drizzle and freezing rain conditions were not evaluated and are considered severe icing conditions for this aeroplane.

Intentional flight, including take-off and landing, into freezing drizzle or freezing rain conditions is prohibited. A flight delay or diversion to an alternate airport is required if these conditions exist at the departure or destination airports. [insert cue description here] is an indication of severe icing conditions that exceed those for which this aeroplane is certified. If severe icing is encountered, immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

A4.2.  Aeroplane approved for flight in Appendix C icing conditions and freezing drizzle conditions of Appendix O but not approved for flight in freezing rain conditions of Appendix O.

a.  AFM Limitations.

Intentional flight, including take-off and landing, into freezing rain conditions is prohibited. If freezing rain conditions are encountered, or if [insert cue description here], immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

b.  AFM Operating Procedures (Normal Procedures Section).

Freezing rain conditions are severe icing conditions for this aeroplane. Intentional flight, including take-off and landing, into freezing rain conditions is prohibited. A flight delay or diversion to an alternate airport is required if these conditions exist at the departure or destination airports.

[insert cue description here] is one indication of severe icing for this aeroplane. If severe icing is encountered, immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

c.  Flight Crew Operating Manual Operating Procedures.

Warning: Hazardous icing effects may result from environmental conditions outside of those for which this aeroplane is certified. Flight into unapproved icing conditions may result in ice build-up on protected surfaces exceeding the capability of the ice protection system, or may result in ice forming aft of the protected surfaces. This ice might not be shed when using the ice protection systems, and may seriously degrade the performance and controllability of the aeroplane.

Operations in icing conditions, including freezing drizzle, were evaluated as part of the certification process for this aeroplane. Freezing rain conditions were not evaluated and are considered severe icing conditions for this aeroplane.

Intentional flight, including take-off and landing, into freezing rain conditions is prohibited. A flight delay or diversion to an alternate airport is required if these conditions exist at the departure or destination airports. [insert cue description here] is an indication of severe icing conditions that exceed those for which this aeroplane is certified. If severe icing is encountered, immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

A4.3  Aeroplane approved for flight in Appendix C and Appendix O icing conditions except for en route and holding flight phases in Appendix O icing conditions.

a.  AFM Limitations.

Intentional holding or en route flight into freezing drizzle or freezing rain conditions is prohibited. If freezing drizzle or freezing rain conditions are encountered during a hold (in any aeroplane configuration) or in the en route phase of flight (climb, cruise, or descent with high lift devices and gear retracted), or if [insert cue description here], immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

b.  AFM Operating Procedures (Normal Procedures Section).

Freezing drizzle and freezing rain conditions encountered during a hold (in any aeroplane configuration) or in the en route phase of flight (climb, cruise, or descent with high lift devices and gear retracted) are severe icing conditions for this aeroplane. Intentional holding or en route flight into freezing drizzle or freezing rain conditions is prohibited.

[insert cue description here] is one indication of severe icing for this aeroplane. If severe icing is encountered, immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

c.  Flight Crew Operating Manual Operating Procedures.

Warning: Hazardous icing effects may result from environmental conditions outside of those for which this aeroplane is certified. Flight into unapproved icing conditions may result in ice build-up on protected surfaces exceeding the capability of the ice protection system, or in ice forming aft of the protected surfaces. This ice might not be shed when using the ice protection systems, and may seriously degrade the performance and controllability of the aeroplane.

Operations in icing conditions were evaluated as part of the certification process for this aeroplane. En route (climb, cruise, and descent with high lift devices and gear retracted) and holding flight (in any aeroplane configuration) in freezing drizzle and freezing rain conditions were not evaluated and are considered severe icing conditions for this aeroplane.

Intentional holding or en route flight into freezing drizzle or freezing rain conditions is prohibited. [insert cue description here] is an indication of severe icing conditions that exceed those for which the aeroplane is certified. If severe icing is encountered, immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

A4.4  Aeroplane approved for flight in Appendix C icing conditions and a portion of Appendix O icing conditions.

a.  AFM Limitations.

Intentional flight, including take-off and landing, into [insert pilot usable description here] conditions is prohibited. If [insert pilot usable description here] conditions are encountered, or if [insert cue description here], immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

b.  AFM Operating Procedures (Normal Procedures Section).

[insert pilot usable description here] are severe icing conditions for this aeroplane. Intentional flight, including take-off and landing, into [insert pilot usable description here] conditions is prohibited. A flight delay or diversion to an alternate airport is required if these conditions exist at the departure or destination airports.

[insert cue description here] is one indication of severe icing for this aeroplane. If severe icing is encountered, immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Stay clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

c.  Flight Crew Operating Manual Operating Procedures.

Warning: Hazardous icing effects may result from environmental conditions outside of those for which this aeroplane is certified. Flight into unapproved icing conditions may result in ice build-up on protected surfaces exceeding the capability of the ice protection system, or may result in ice forming aft of the protected surfaces. This ice may not be shed when using the ice protection systems, and may seriously degrade the performance and controllability of the aeroplane.

Operations in icing conditions were evaluated as part of the certification process for this aeroplane. [insert pilot usable description here] were not evaluated and are considered severe icing conditions for this aeroplane.

Intentional flight, including take-off and landing, into [insert pilot usable description here] is prohibited. A flight delay or diversion to an alternate airport is required if these conditions exist at the departure or destination airports. [insert cue description here] is an indication of severe icing conditions that exceed those for which this aeroplane is certified. If severe icing is encountered, immediately request priority handling from air traffic control to facilitate a route or altitude change to exit all icing conditions. Remain clear of all icing conditions for the remainder of the flight, including landing, unless it can be determined that ice accretions no longer remain on the airframe.

[Amdt 25/16]

Appendix 5 – Related Acceptable Means of Compliance (AMC) and FAA Advisory Circulars (AC)

ED Decision 2015/008/R

Acceptable Means of Compliance

The following AMCs are related to the guidance contained in this AMC:

AMC 25.1309, System Design and Analysis

AMC N°. 1 to CS 25.1329, Flight Guidance System

AMC N°. 2 to CS 25.1329, Flight testing of Flight Guidance Systems

AMC 25.1419, Ice Protection

AMC 25.1420, Supercooled large drop icing conditions

Advisory Circulars

The following FAA ACs are related to the guidance contained in this AMC.

AC 20-73A, Aircraft Ice Protection

[Amdt 25/16]

Appendix 6 – Acronyms and definitions

ED Decision 2015/008/R

AC	Advisory Circular
AFM	Aeroplane Flight Manual
ATTCS	Automatic Takeoff Thrust Control System
FAA	Federal Aviation Administration
ICTS	Ice-Contaminated Tailplane Stall.
LWC	Liquid Water Content
MED	Mean Effective Diameter
MVD	Median Volume Diameter
CL	Lift Coefficient
CLMAX	Maximum Lift Coefficient
Trim	A flight condition in which the aerodynamic moment acting about the axis of interest is zero. In the absence of an external disturbance no control input is needed to maintain the flight condition.

[Amdt 25/16]

CS 25.23 Load distribution limits

ED Decision 2003/2/RM

(a) Ranges of weights and centres of gravity within which the aeroplane may be safely operated must be established. If a weight and centre of gravity combination is allowable only within certain load distribution limits (such as spanwise) that could be inadvertently exceeded, these limits and the corresponding weight and centre of gravity combinations must be established.

(b) The load distribution limits may not exceed –

(1) The selected limits;

(2) The limits at which the structure is proven; or

(3) The limits at which compliance with each applicable flight requirement of this Subpart is shown.

CS 25.25 Weight Limits

ED Decision 2003/2/RM

(a) Maximum weights. Maximum weights corresponding to the aeroplane operating conditions (such as ramp, ground taxi, take-off, en-route and landing) environmental conditions (such as altitude and temperature), and loading conditions (such as zero fuel weight, centre of gravity position and weight distribution) must be established so that they are not more than –

(1) The highest weight selected by the applicant for the particular conditions; or

(2) The highest weight at which compliance with each applicable structural loading and flight requirement is shown.

(3) The highest weight at which compliance is shown with the noise certification requirements.

(b) Minimum weight. The minimum weight (the lowest weight at which compliance with each applicable requirement of this CS-25 is shown) must be established so that it is not less than –

(1) The lowest weight selected by the applicant;

(2) The design minimum weight (the lowest weight at which compliance with each structural loading condition of this CS-25 is shown); or

(3) The lowest weight at which compliance with each applicable flight requirement is shown.

CS 25.27 Centre of gravity limits

ED Decision 2003/2/RM

The extreme forward and the extreme aft centre of gravity limitations must be established for each practicably separable operating condition. No such limit may lie beyond –

(a) The extremes selected by the applicant;

(b) The extremes within which the structure is proven; or

(c) The extremes within which compliance with each applicable flight requirement is shown.

CS 25.29 Empty weight and corresponding centre of gravity

ED Decision 2003/2/RM

(a) The empty weight and corresponding centre of gravity must be determined by weighing the aeroplane with –

(1)  Fixed ballast;

(2) Unusable fuel determined under CS 25.959; and

(3) Full operating fluids, including –

(i) Oil;

(ii) Hydraulic fluid; and

(iii) Other fluids required for normal operation of aeroplane systems, except potable water, lavatory pre-charge water, and fluids intended for injection in the engine.

(b) The condition of the aeroplane at the time of determining empty weight must be one that is well defined and can be easily repeated.

CS 25.31 Removable ballast

ED Decision 2003/2/RM

Removable ballast may be used in showing compliance with the flight requirements of this Subpart.

CS 25.33 Propeller speed and pitch limits

ED Decision 2003/2/RM

(a) The propeller speed and pitch must be limited to values that will ensure –

(1) Safe operation under normal operating conditions; and

(2)Compliance with the performance requirements in CS 25.101 to 25.125.

(b) There must be a propeller speed limiting means at the governor. It must limit the maximum possible governed engine speed to a value not exceeding the maximum allowable rpm.

(c) The means used to limit the low pitch position of the propeller blades must be set so that the engine does not exceed 103% of the maximum allowable engine rpm or 99% of an approved maximum overspeed, whichever is greater, with –

(1) The propeller blades at the low pitch limit and governor inoperative;

(2) The aeroplane stationary under standard atmospheric conditions with no wind; and

(3) The engines operating at the maximum take-off torque limit for turbopropeller engine-powered aeroplanes.