Special Conditions: Airbus Model A321neo XLR Airplanes; Flight Envelope Protection, Icing and Non-Icing Conditions; High Incidence Protection, 42788-42792 [2024-10646]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 89, Number 96 (Thursday, May 16, 2024)]
[Rules and Regulations]
[Pages 42788-42792]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-10646]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. No. FAA-2021-1032; Special Conditions No. 25-854-SC]


Special Conditions: Airbus Model A321neo XLR Airplanes; Flight 
Envelope Protection, Icing and Non-Icing Conditions; High Incidence 
Protection

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Airbus Model 
A321neo XLR airplane. This airplane will have a novel or unusual design 
feature when compared to the state of technology envisioned in the 
applicable airworthiness standards for transport category airplanes. 
This design feature is flight-envelope protections, in icing and non-
icing conditions, that use high-incidence protection and an alpha-floor 
system to automatically advance throttles when the airplane angle of 
attack reaches a predetermined value. The applicable airworthiness 
regulations do not contain adequate or appropriate safety standards for 
this design feature. These special conditions contain the additional 
safety standards that the Administrator considers necessary to 
establish a level of safety equivalent to that established by the 
existing airworthiness standards.

DATES: Effective June 17, 2024.

FOR FURTHER INFORMATION CONTACT: Troy Brown, Performance and 
Environment Unit, AIR-621A, Technical Policy Branch, Policy and 
Standards Division, Aircraft Certification Service, Federal Aviation 
Administration, 1801 S Airport Rd., Wichita, KS 67209-2190; telephone 
and fax 405-666-1050; email [email protected].

SUPPLEMENTARY INFORMATION:

Background

    On September 16, 2019, Airbus applied for an amendment to Type 
Certificate No. A28NM to include the new Model A321neo XLR airplane. 
These airplanes are twin-engine, transport-category airplanes with 
seating for 244 passengers, and a maximum take-off weight of 222,000 
pounds.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Airbus must show that the 
Model A321neo XLR airplane meets the applicable provisions of the 
regulations listed in Type Certificate No. A28NM, or the applicable 
regulations in effect on the date of application for the change, except 
for earlier amendments as agreed upon by the FAA.
    If the Administrator finds that the applicable airworthiness 
regulations (e.g., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Airbus Model A321neo XLR airplanes 
because of a novel or unusual design feature, special conditions are 
prescribed under the provisions of Sec.  21.16.
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other model that incorporates the same novel or 
unusual design feature, or should any other model already included on 
the same type certificate be modified to incorporate the same novel or 
unusual design feature, these special conditions would also apply to 
the other model under Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the Airbus Model A321neo XLR airplane must comply with the 
fuel-vent and exhaust-emission requirements of 14 CFR part 34, and the 
noise-certification requirements of 14 CFR part 36.
    The FAA issues special conditions, as defined in Sec.  11.19, in 
accordance with Sec.  11.38, and they become part of the type 
certification basis under 14 CFR 21.101.

Novel or Unusual Design Feature

    The Airbus Model A321neo XLR airplane will incorporate the 
following novel or unusual design feature:
    Flight-envelope protections, in icing and non-icing conditions, 
that use high- incidence protection and an alpha-floor function to 
automatically advance throttles when the airplane angle of attack (AoA) 
reaches a predetermined value.

Discussion

    The current airworthiness standards do not contain adequate safety 
standards for the high-incidence protection system and the alpha-floor 
system for the Airbus Model A321neo XLR series airplanes. This is 
because the FAA's current standards were designed for more traditional 
electronic flight control systems (EFCS), which involve less advanced 
envelope protections, such as stick shakers and pushers. These special 
conditions address the more advanced flight envelope protections, 
including icing and non-icing conditions, that are part of the EFCS 
design of the A321neo XLR airplane.
    The high-incidence protection system prevents the airplane from 
stalling and, therefore, the stall warning system is not needed during 
normal flight conditions. However, during failure conditions which are 
not shown to be extremely improbable, the requirements of Sec. Sec.  
25.203 and 25.207 apply, although slightly modified by these 
conditions. If there are failures not shown to be extremely improbable, 
the flight characteristics at the angle-of-attack for CLMAX 
must be suitable in the traditional sense, and stall warning must be 
provided in a conventional manner. These special conditions address the 
need for modification during icing conditions and non-icing conditions.
    The alpha-floor function automatically advances the throttles on 
the operating engines under flight circumstances of low speed if the 
airplane reaches a predetermined high AoA. This function is intended to 
provide increased climb capability.
    These special conditions address this novel or unusual design 
feature on the Airbus Model A321neo XLR and contain the additional 
safety standards that the Administrator considers necessary to 
establish a level of safety equivalent to that established by the 
existing airworthiness standards.

Discussion of Comments

    The FAA issued Notice of Special Conditions No. 25-23-03-SC for the 
Airbus Model A321neo XLR airplane. They were published in the Federal 
Register on November 3, 2023 (88 FR 75513). The FAA received comments 
from Airbus Commercial Aircraft

[[Page 42789]]

(Airbus) and The Boeing Company (Boeing).
    Boeing requested that the FAA add statements to sections 
(e)(1)(ii)(B) and (C) of the proposed special conditions regarding the 
demonstration of satisfactory lateral control at the aft stop and the 
consideration of rapid application of go-around power or thrust. Boeing 
requested these changes for consistency with the proposed regulatory 
material for Sec.  25.202(d)(2) and (4) in the Flight Test 
Harmonization Working Group Phase 2 Rev A Final Report \1\ (FTHWG 
Report). The FAA does not agree to this change. The FAA has previously 
published special conditions on this subject. The terms of those 
special conditions were consistent with the terms of these special 
conditions, and the FAA finds that they provide an adequate level of 
safety, i.e., a level equivalent to the standards that, absent these 
special conditions, would otherwise be applicable.
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    \1\ https://www.faa.gov/regulations_policies/rulemaking/committees/documents/media/09%20-%20FTHWG_Final_Report_Phase_2_RevA__Apr_2017.pdf.
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    Boeing recommended the FAA add ``and emergency'' to the proposed 
special conditions regarding the alpha-floor setting not interfering 
with normal maneuvering because this change would be consistent with 
proposed regulatory material for Sec.  25.144(a) in the FTHWG Report. 
The FAA declines to make this change. This special condition only 
addresses the alpha-floor setting in normal maneuvering. The general 
limiting special conditions \2\ for the A321neo XLR already include 
requirements for normal and emergency operations of all flight envelope 
protection functions, which include the alpha-floor function.
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    \2\ 88 FR 12133 (Feb. 27, 2023).
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    Boeing requested the FAA revise the deceleration rate in icing 
conditions in section (e)(1)(ii)(C)(2) of the proposed special 
conditions to 3 knots per second because this change would be 
consistent with the Airbus Model A350-900 Special Conditions No. 25-
517-SC part I section 5.1(b)(3)(ii) and the proposed regulatory 
material for Sec.  25.202(d)(4) in the FTHWG Report. The FAA does not 
concur with Boeing's request because this change would not be 
appropriate for the design of the A321neo XLR. The XLR EFCS 
architecture is based on a previously certified architecture for the 
Airbus Model A321neo ACF. The A321neo ACF used a deceleration rate in 
icing conditions of 2 knots per second; therefore, using the same 
requirement for the A321neo XLR is appropriate and provides an adequate 
(equivalent) level of safety.
    Boeing requested the FAA revise section (e)(2)(i)(D) of the 
proposed special conditions related to buffeting to have the same 
requirement for icing and non-icing conditions, which Boeing said would 
also be consistent with 25-517-SC part II section 3(a)(2)(i) and the 
proposed regulatory material for 25.105(a)(2)(iii) in the FTHWG Report. 
Boeing stated that the requirement for icing conditions appears to 
indicate that buffet of a deterrent magnitude and severity would be 
acceptable for demonstration. The FAA does not concur with Boeing's 
request. The FAA does not intend the buffeting requirement for icing 
conditions to allow deterrent buffet. The wording of these special 
conditions is appropriate because the magnitude of the buffet can be a 
driver in setting the protections while still requiring the airplane be 
free from excessive vibration and buffet. Therefore, these special 
conditions provide an adequate level of safety.
    Boeing requested that the FAA remove all notes under section (j) of 
the proposed special conditions; the notes mention a tolerance for 
take-off and climb-out speeds in icing. Boeing stated that the 
tolerance in the notes appears to expand the allowable degradation in 
performance prior to calculating the icing effect and that the removal 
of the notes would align with previously released special conditions on 
this topic, such as 25-517-SC, and the recommendations in the FTHWG 
Report. The FAA does not concur with Boeing's request. The A321neo XLR 
is a derivative of an airplane (A321neo ACF) initially certified with 
tolerances to account for ice effect on performance along the take-off 
path as well as at landing. In particular, it was not needed to account 
for icing if the ice effect on Vmin1g was less than 5%/5kt. 
To reflect the intent of Sec.  25.21(g) on airplanes for which Sec.  
25.21(g) is not applicable, Airbus has proposed a standard for the 
A321neo XLR consisting of the removal of the tolerance at landing and a 
reduced tolerance to 2.5%/2.5kt for take-off path. Airbus considers 
that the requirements of these special conditions provide an adequate 
level of safety based on the in-service performance of previous A321 
models, and the FAA concurs.
    Airbus, the applicant, requested the FAA revise the special 
condition that the FAA proposed would apply in lieu of Sec.  
25.121(d)(2)(ii). Airbus provided updated wording that replaced the 
text presented in the notice with text inspired by the FTHWG report 
recommendations. Airbus stated that this text is comparable in intent 
to the text proposed by FAA in the notice but with an improved clarity 
thanks to a more modern wording, anticipating the future implementation 
of the FTHWG recommendations. The FAA concurs with this rationale and 
has modified the final special condition accordingly.
    Boeing commented that the formatting of the proposed special 
conditions related to Sec.  25.121 could lead to confusion as to which 
regulations were being addressed due to missing paragraph numbers. The 
FAA concurs and has updated the format of the final special conditions 
to clarify.

Applicability

    As discussed above, these special conditions are applicable to the 
Airbus Model A321neo XLR airplane. Should Airbus apply at a later date 
for a change to the type certificate to include another model 
incorporating the same novel or unusual design feature, these special 
conditions would apply to that model as well.
    Under standard practice, the effective date of final special 
conditions would be 30 days after the date of publication in the 
Federal Register. However, as the certification date for the Airbus 
Model A321neo XLR is imminent, the FAA finds that good cause exists to 
make these special conditions effective upon publication.

Conclusion

    This action affects only certain novel or unusual design features 
on one model A321neo XLR airplane. It is not a rule of general 
applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

Authority Citation

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for the Airbus Model A321neo XLR airplane.
    In the following paragraphs, ``In icing conditions'' means with the 
ice accretions, relevant for the flight phase, as defined in part 25, 
appendix C.

(a) Definitions

    These special conditions address a novel or unusual design feature 
of the Airbus A321neo XLR and use

[[Page 42790]]

terminology that does not appear in part 25. For the purpose of these 
special conditions, the following terms describe certain aspects of 
this novel or unusual design feature:

High-Incidence Protection System Angle-of-Attack Limiting Function

    A system that operates directly and automatically on the airplane's 
flying controls to limit the maximum AoA that can be attained to a 
value below that at which an aerodynamic stall would occur.

Alpha-Floor System

    A system that automatically increases thrust on the operating 
engines when AoA increases through a particular value.

Alpha Limit

    The maximum angle of attack at which the airplane stabilizes with 
the high-incidence protection system operating and the longitudinal 
control held on its aft stop.

VCLmax

    An airspeed calculated from a variety of factors, including load 
factor normal to the flight path at VCLmax, airplane gross 
weight, aerodynamic reference wing area, and dynamic pressure.

Vmin

    The minimum steady flight speed in the airplane configuration under 
consideration with the high-incidence protection system operating.

Vmin1g

    Vmin corrected to 1g conditions. This is the minimum 
calibrated airspeed at which the airplane can develop a lift force 
normal to the flight path and equal to its weight when at an angle of 
attack not greater than that determined for Vmin.

(b) Capability and Reliability of the High-Incidence Protection System

    Acceptable capability and reliability of the high-incidence 
protection system can be established by flight test, simulation, and 
analysis, as appropriate. The capability and reliability required are 
as follows:
    (1) It must not be possible, during pilot-induced maneuvers, to 
encounter a stall; and handling characteristics must be acceptable, as 
required by section (e) of these Special Conditions.
    (2) The airplane must be protected against stalling due to the 
effects of wind-shears and gusts at low speeds as required by section 
(f) of these Special Conditions.
    (3) The ability of the high-incidence protection system to 
accommodate any reduction in stalling incidence must be verified in 
icing conditions.
    (4) The high-incidence protection system must be provided in each 
abnormal configuration of the high-lift devices that are likely to be 
used in-flight following system failures.
    (5) The reliability of the system and the effects of failures must 
be acceptable in accordance with Sec.  25.1309.

(c) Minimum Steady Flight Speed and Reference Stall Speed

    In lieu of Sec.  25.103, ``Stall speed'', the following 
requirements apply:
    (1) The minimum steady flight speed, Vmin, is the final 
stabilized calibrated airspeed obtained when the airplane is 
decelerated until the longitudinal control is on its stop in such a way 
that the entry rate does not exceed 1 knot per second.
    (2) The minimum steady flight speed, Vmin, must be 
determined in icing and non-icing conditions with:
    (i) The high-incidence protection system operating normally;
    (ii) Idle thrust and alpha-floor system inhibited;
    (iii) All combinations of flaps setting and landing gear position 
for which Vmin is required to be determined;
    (iv) The weight used when the reference stall speed, 
VSR, is being used as a factor to determine compliance with 
a required performance standard;
    (v) The most unfavorable center of gravity allowable; and
    (vi) The airplane trimmed for straight flight at a speed achievable 
by the automatic trim system.
    (3) The 1g minimum steady flight speed, Vmin1g, is the 
minimum calibrated airspeed at which the airplane can develop a lift 
force normal to the flight path and equal to its weight, while at an 
angle of attack not greater than that at which the minimum steady 
flight speed of condition 3(a), above, was determined. It must be 
determined in icing and non-icing conditions.
    (4) The reference stall speed, VSR, is a calibrated 
airspeed the applicant defines. VSR may not be less than a 
1g stall speed. VSR must be determined in non-icing 
conditions and expressed as:
[GRAPHIC] [TIFF OMITTED] TR16MY24.088

Where:

VCLmax = the calibrated airspeed obtained when the load 
factor corrected lift coefficient (nzw W/qS) is first a 
maximum during the maneuver prescribed in condition (c)(5)(viii) of 
these Special Conditions;
nzw = Load factor normal to the flight path at 
VClmax;
W = Airplane gross weight;
S = Aerodynamic reference wing area; and
q = Dynamic pressure.

    (5) VClmax is determined in non-icing conditions with:
    (i) Engines idling, or, if that resultant thrust causes an 
appreciable decrease in stall speed, not more than zero thrust at the 
stall speed;
    (ii) The airplane in other respects (such as flaps and landing 
gear) in the condition existing in the test or performance standard in 
which VSR is being used;
    (iii) The weight used when VSR is being used as a factor 
to determine compliance with a required performance standard;
    (iv) The center of gravity position that results in the highest 
value of reference stall speed;
    (v) The airplane trimmed for straight flight at a speed achievable 
by the automatic trim system, but not less than 1.13 VSR and 
not greater than 1.3 VSR;
    (vi) Alpha-floor system inhibited; and
    (vii) The high-incidence protection system adjusted, at the option 
of the applicant, to allow higher incidence than is possible with the 
normal production system.
    (viii) Starting from the stabilized trim condition, apply the 
longitudinal control to decelerate the airplane so that the speed 
reduction does not exceed 1 knot per second.

(d) Stall Warning

    In lieu of Sec.  25.207, the following requirements apply:

(1) Normal Operation

    If the design meets all conditions of section (b) of these special 
conditions,

[[Page 42791]]

then the airplane need not provide stall warning during normal 
operation. The conditions of Part I, section 2 provide a level of 
safety equal to the intent of Sec.  25.207, ``Stall warning,'' so the 
provision of an additional, unique warning device for normal operations 
is not required.

(2) High-Incidence Protection System Failure

    (i) In non-icing conditions, for any failures of the high-incidence 
protection system that the applicant cannot show to be extremely 
improbable, such that the capability of the system no longer satisfies 
conditions (b)(1), (2), and (3) of these Special Conditions, stall 
warning must be provided in accordance with Sec.  25.207(a), (b), and 
(f).
    (ii) In icing conditions, after a failure leading to the loss of 
the high-incidence protection system, a safety margin not less than 3 
percent or 3 knots between stall warning and stall must be maintained.

(e) Handling Characteristics at High Incidence

(1) High Incidence Handling Demonstrations

    In lieu of Sec.  25.201, High-incidence handling demonstration in 
icing and non-icing conditions:
    (i) Maneuvers to the limit of the longitudinal control, in the 
nose-up sense, must be demonstrated in straight flight and in 30-degree 
banked turns with:
    (A) The high-incidence protection system operating normally;
    (B) Initial power conditions of:
    (1) Power off; and
    (2) The power necessary to maintain level flight at 1.5 
VSR1, where VSR1 is the reference stall speed 
with flaps in approach position, the landing gear retracted, and 
maximum landing weight;
    (C) Alpha-floor system operating normally unless more severe 
conditions are achieved with inhibited alpha floor;
    (D) Flaps, landing gear, and deceleration devices in any likely 
combination of position;
    (E) Representative weights within the range for which certification 
is requested; and
    (F) The airplane trimmed for straight flight at a speed achievable 
by the automatic trim system.
    (ii) The following procedures must be used to show compliance in 
non-icing and icing conditions:
    (A) Starting at a speed sufficiently above the minimum steady 
flight speed to ensure that a steady rate of speed reduction can be 
established, apply the longitudinal control so that the speed reduction 
does not exceed 1 knot per second until the control reaches the stop.
    (B) The longitudinal control must be maintained at the stop until 
the airplane has reached a stabilized flight condition, and must then 
be recovered through normal recovery techniques.
    (C) Maneuvers with increased deceleration rates:
    (1) In non-icing conditions, the requirements must also be met with 
increased rates of entry to the incidence limit, up to the maximum rate 
achievable.
    (2) In icing conditions, with the anti-ice system working normally, 
the requirements must also be met with increased rates of entry to the 
incidence limit up to 2 knots per second.
    (D) Maneuvers with ice accretion prior to operation of the normal 
anti-ice system: With the ice accretion prior to operation of the 
normal anti-ice system, the requirement must also be met in 
deceleration at 1 knot per second up to full back stick maintained for 
at least 3 seconds before normal recovery is performed (requirement to 
be met with and without alpha floor operating).

(2) Characteristics in High-Incidence Maneuvers

    In lieu of Sec.  25.203, Characteristics in High Incidence.
    In icing and non-icing conditions:
    (i) Throughout maneuvers with a rate of deceleration of not more 
than 1 knot per second, both in straight flight and in 30-degree banked 
turns, the airplane's characteristics must be as follows:
    (A) The airplane must not exhibit abnormal nose-up pitching.
    (B) The airplane must not exhibit uncommanded nose-down pitching, 
which would be indicative of stall. However, reasonable attitude 
changes associated with stabilizing the incidence at alpha limit, as 
the longitudinal control reaches the stop, would be acceptable.
    (C) The airplane must not exhibit uncommanded lateral or 
directional motion, and the pilot must retain good lateral and 
directional control through conventional use of the controls, 
throughout the maneuver.
    (D) Buffeting:
    (1) In non-icing conditions, the airplane must not exhibit 
buffeting of a magnitude and severity that would act as a deterrent 
from completing the maneuver specified in condition (e)(1)(i) of these 
Special Conditions.
    (2) In icing conditions, the airplane may exhibit buffeting of a 
stronger magnitude and severity than in non-icing conditions, provided 
that the airplane is demonstrated to be free from excessive vibration 
and buffeting over the range of speeds adequate for normal operation.
    (ii) In maneuvers with increased rates of deceleration, some 
degradation of characteristics is acceptable, associated with a 
transient excursion beyond the stabilized alpha limit. However, the 
airplane must not exhibit dangerous characteristics, nor 
characteristics that would deter the pilot from holding the 
longitudinal control on the stop for a period of time appropriate to 
the maneuver.
    (iii) The pilot must always be able to reduce incidence through 
conventional use of the controls.
    (iv) The rate at which the airplane can be maneuvered from trim 
speeds associated with scheduled operating speeds such as V2 
and Vref, up to alpha limit, must not be unduly damped or be 
significantly slower than can be achieved on conventionally controlled 
transport airplanes.

(3) Characteristics up to VCLmax

    Maneuvers with a rate of deceleration of not more than 1 knot per 
second, up to the angle of attack at which VCLmax was 
obtained as defined in section (c) of these Special Conditions, must be 
demonstrated in straight flight and in 30-degree banked turns with:
    (i) The high-incidence protection system deactivated or adjusted, 
at the option of the applicant, to allow higher incidence than is 
possible with the normal production system,
    (ii) Alpha-floor system inhibited,
    (iii) Engines idling,
    (iv) Flaps and landing gear in any likely combination of positions, 
and
    (v) The airplane trimmed for straight flight at a speed achievable 
by the automatic trim system.
    During such maneuvers, the airplane must not exhibit dangerous 
characteristics and the pilot must always be able to reduce angle of 
attack by conventional use of the controls. The pilot must retain good 
lateral and directional control, by conventional use of the controls, 
throughout the maneuver.

(f) Atmospheric Disturbances

    Operation of the high-incidence protection system must not 
adversely affect airplane control during expected levels of atmospheric 
disturbances, nor impede the application of recovery procedures in case 
of wind shear. This must be demonstrated in non-icing conditions only, 
and must allow for drawing conclusion for icing conditions without 
further demonstration.

[[Page 42792]]

(g) Alpha Floor

    In icing and non-icing conditions, the alpha-floor setting must be 
such that the airplane can be flown at the speeds and bank angles 
specified in Sec.  25.143(h). The applicant also must show that the 
alpha-floor setting does not interfere with normal maneuvering of the 
airplane. In addition, the airplane must exhibit no alpha-floor 
triggering unless appropriate when the airplane is flown in usual 
operational maneuvers and in turbulence.

(h) Proof of Compliance

    In addition to the requirements in Sec.  25.21(b), the following 
requirement applies:
    The flying qualities will be evaluated at the most unfavorable 
center-of-gravity (CG) position.
    (i) Speed Associated With Other Requirements
    The design must meet the following modified requirements:
    (1) Section 25.145(a): Vmin in lieu of ``stall 
identification.''
    (2) Section 25.145(b): Vmin in lieu of Vsw.
    (3) Section 25.1323(d): ``From 1.23 VSR to 
Vmin'' in lieu of ``1.23 VSR to stall warning 
speed'' and ``speeds below Vmin'' in lieu of ``speeds below 
stall warning.''

(j) Performance in Icing Conditions

(1) Take-Off

    In lieu of compliance with Sec.  25.105(a)(2)(i), the following 
special conditions apply:
    (a) In icing conditions, if in the configuration used in showing 
compliance with Sec.  25.121(b), and with the most critical of the 
``Take-off Ice'' accretion(s) defined in 14 CFR part 25, appendix C:
    (i) The V2 speed scheduled in non-icing conditions does 
not provide the maneuvering capability specified in Sec.  25.143(h) for 
the take-off configuration.

    Note: This requirement does not apply if the Vmin1g 
is increased in icing conditions, with the ``Take-off Ice'' 
accretion defined in 14 CFR part 25, appendix C, by less than 2.5 
knots or 2.5 percent, whichever is greater.

(2) Climb: One-Engine Inoperative

    In lieu of compliance with Sec.  25.121(b)(2)(ii)(A), the following 
special conditions apply:
    (a) In icing conditions, with the most critical of the take-off ice 
accretion(s) defined in 14 CFR part 25, appendix C, if in the 
configuration used to show compliance with Sec.  25.121(b) with this 
take-off ice accretion:
    (i) The V2 speed scheduled in non-icing conditions does 
not provide the maneuvering capability specified in Sec.  25.143(h), 
for the take-off configuration.

    Note: This requirement does not apply if the Vmin1g 
is increased in icing conditions, with the ``Take-off Ice'' 
accretion defined in 14 CFR part 25, appendix C, by less than 2.5 
knots or 2.5 percent, whichever is greater.

    In lieu of compliance with Sec.  25.121(c)(2)(ii)(A) and (B), the 
following special conditions apply:
    (b) In icing conditions, with the most critical of the final take-
off ice accretion(s) defined in 14 CFR part 25, appendix C, if in the 
configuration used to show compliance with Sec.  25.121(b) with the 
take-off ice accretion used to show compliance with Sec.  
25.111(c)(5)(i):
    (i) The VFTO (final take-off speed) scheduled in non-
icing conditions does not provide the maneuvering capability, specified 
in Sec.  25.143(h), for the en-route configuration.

    Note:  This requirement does not apply if the Vmin1g 
is increased in icing conditions, with the ``Final Take-off Ice'' 
accretion defined in 14 CFR part 25, appendix C, by less than 2.5 
knots or 2.5 percent, whichever is greater.

    (ii) The degradation of the gradient of climb, determined in 
accordance with Sec.  25.121(b), with the take-off ice accretion used 
in showing compliance with Sec.  25.111(c)(5)(i), is greater than one-
half of the applicable actual-to-net take-off flight path gradient 
reduction defined in Sec.  25.115(b).
    In lieu of compliance with 25.121(d)(2)(ii), the following special 
conditions apply:
    (c) In icing conditions, with the most critical of the approach ice 
accretion(s) defined in 14 CFR part 25, appendix C, as applicable,
    (i) The climb speed selected for non-icing conditions may be used 
if the climb speed for icing conditions, computed in accordance with 
Sec.  25.121(d)(3), does not exceed that for non-icing conditions by 
more than the greater of 3 knots CAS or 3 percent; or,
    (ii) The climb speed established with normal landing procedures, 
but not more than 1.4 VSR (VSR determined in non-
icing conditions), may be used if in a configuration corresponding to 
the normal all-engines-operating procedure where the Vmin1g 
for this configuration does not exceed 110 percent of the 
Vmin1g for the related all-engines-operating landing 
configuration in icing conditions.

(3) En-Route Flight Paths

    In lieu of compliance with 25.123(b)(2)(i), the following special 
conditions apply:
    (a) In icing conditions with the most critical of the en-route ice 
accretion(s) defined in 14 CFR part 25, appendix C, if:
    (i) The VFTO speed scheduled in non-icing conditions 
does not provide the maneuvering capability, specified in Sec.  
25.143(h), for the en-route configuration.

    Issued in Kansas City, Missouri, on May 10, 2024.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2024-10646 Filed 5-15-24; 8:45 am]
BILLING CODE 4910-13-P