[Federal Register Volume 88, Number 212 (Friday, November 3, 2023)]
[Proposed Rules]
[Pages 75513-75517]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-24311]


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Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of 
the proposed issuance of rules and regulations. The purpose of these 
notices is to give interested persons an opportunity to participate in 
the rule making prior to the adoption of the final rules.

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Federal Register / Vol. 88, No. 212 / Friday, November 3, 2023 / 
Proposed Rules

[[Page 75513]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2021-1032; Notice No. 25-23-03-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: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for the Airbus Model 
A321neo XLR airplane. The airplane will have a novel or unusual design 
feature when compared to the state of technology envisioned in the 
airworthiness standards for transport-category airplanes. This design 
feature is associated with 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: Send comments on or before December 4, 2023.

ADDRESSES: Send comments identified by Docket No. FAA-2021-1032 using 
any of the following methods:
    Federal eRegulations Portal: Go to https://www.regulations.gov/ and 
follow the online instructions for sending your comments 
electronically.
    Mail: Send comments to Docket Operations, M-30, U.S. Department of 
Transportation (DOT), 1200 New Jersey Avenue SE, Room W12-140, West 
Building Ground Floor, Washington, DC 20590-0001.
    Hand Delivery or Courier: Take comments to Docket Operations in 
Room W12-140 of the West Building Ground Floor at 1200 New Jersey 
Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday through 
Friday, except Federal holidays.
    Fax: Fax comments to Docket Operations at 202-493-2251.
    Docket: Background documents or comments received may be read at 
https://www.regulations.gov/ at any time. Follow the online 
instructions for accessing the docket or go to Docket Operations in 
Room W12-140 of the West Building Ground Floor at 1200 New Jersey 
Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday through 
Friday, except Federal holidays.

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 <a href="/cdn-cgi/l/email-protection#ef9b9d8096c18ec18d9d809881af898e8ec1888099"><span class="__cf_email__" data-cfemail="780c0a17015619561a0a170f16381e1919561f170e">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION: 

Comments Invited

    The FAA invites interested people to take part in this rulemaking 
by sending written comments, data, or views. The most helpful comments 
reference a specific portion of the proposed special conditions, 
explain the reason for any recommended change, and include supporting 
data.
    Certification of the Airbus Model A321neo XLR airplane is currently 
scheduled for December 2023. The substance of these special conditions, 
in all material respects, has been subject to the notice and public-
comment procedure in several prior instances. Therefore, because a 
delay would significantly affect the applicant's installation of the 
novel or unusual design feature, and delay certification of the 
airplane, the FAA is reducing the public-comment period to 30 days.
    The FAA will consider all comments received by the closing date for 
comments, and will consider comments filed late if it is possible to do 
so without incurring delay. The FAA may change these special conditions 
based on the comments received.

Privacy

    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other information as described in title 
14, Code of Federal Regulations (14 CFR) 11.35, the FAA will post all 
comments received without change to https://www.regulations.gov/, 
including any personal information you provide. The FAA will also post 
a report summarizing each substantive verbal contact received about 
these special conditions.

Confidential Business Information

    Confidential Business Information (CBI) is commercial or financial 
information that is both customarily and actually treated as private by 
its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), 
CBI is exempt from public disclosure. If your comments responsive to 
these special conditions contain commercial or financial information 
that is customarily treated as private, that you actually treat as 
private, and that is relevant or responsive to these special 
conditions, it is important that you clearly designate the submitted 
comments as CBI. Please mark each page of your submission containing 
CBI as ``PROPIN.'' The FAA will treat such marked submissions as 
confidential under the FOIA, and the indicated comments will not be 
placed in the public docket of these special conditions. Send 
submissions containing CBI to the individual listed in the For Further 
Information Contact section below. Comments the FAA receives, which are 
not specifically designated as CBI, will be placed in the public docket 
for these special conditions.

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

[[Page 75514]]

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 Features

    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 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 14 CFR 25.203 
and 25.207 apply, although slightly modified. If there are failures not 
shown to be extremely improbable, the flight characteristics at the 
angle-of-attack for C<INF>LMAX</INF> 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 these novel or unusual design 
features 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.

Applicability

    As discussed above, these special conditions apply to Airbus Model 
A321neo XLR airplane. Should Airbus apply later for a change to the 
type certificate to include another model incorporating the same novel 
or unusual design feature, the special conditions would apply to that 
model as well.

Conclusion

    This action affects only certain novel or unusual design features 
on one model series of airplanes. 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, and 
44704.

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for Airbus Model A321neo XLR airplane. These special conditions are 
issued in lieu of the paragraphs of 14 CFR part 25 referenced below.

Foreword

    In the following paragraphs, ``In icing conditions'' means with the 
ice accretions, relevant for the flight phase, as defined in part 25, 
amendment 121, appendix C.

(a) Definitions

    These special conditions address novel or unusual design features 
of the Airbus A321neo XLR and use terminology that does not appear in 
part 25. For the purpose of these special conditions, the following 
terms describe certain aspects of these novel or unusual design 
features:

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 angle of attack (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 V<INF>CLmax</INF>, 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

    V<INF>min</INF> 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 V<INF>min</INF>.

(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.

[[Page 75515]]

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 condition (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 condition 
(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, minimum steady flight speed and reference 
stall speed, the following requirements apply:
    (1) The minimum steady flight speed, V<INF>min</INF>, 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, V<INF>min</INF>, 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 V<INF>min</INF> is required to be determined;
    (iv) The weight used when the reference stall speed, 
V<INF>SR</INF>, 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, V<INF>min1g</INF>, is the 
minimum calibrated airspeed at which the airplane can develop a lift 
force (normal to the flight path) equal to its weight, while at an 
angle of attack not greater than that at which the minimum steady 
flight speed of condition (c)(1), above, was determined. It must be 
determined in icing and non-icing conditions.
    (4) The reference stall speed, V<INF>SR</INF>, is a calibrated 
airspeed the applicant defines. V<INF>SR</INF> may not be less than a 
1g stall speed. V<INF>SR</INF> must be determined in non-icing 
conditions and expressed as:
[GRAPHIC] [TIFF OMITTED] TP03NO23.032

Where:

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

    (5) V<INF>CLmax</INF> 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 V<INF>SR</INF> is being used;
    (iii) The weight used when V<INF>SR</INF> 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 V<INF>SR</INF> and 
not greater than 1.3 V<INF>SR</INF>;
    (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 capabilities of the high-incidence protection system are 
met, then condition (b) of these Special Conditions are satisfied. 
These conditions provide an equivalent level of safety to Sec.  25.207, 
Stall Warning, so the provision of an additional, unique warning device 
is not required.
    (2) High-Incidence Protection System Failure.
    (i) In non-icing conditions, following failures of the high-
incidence protection system, not shown 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.
    (2) The power necessary to maintain level flight at 1.5 
V<INF>SR1,</INF> where V<INF>SR1</INF> 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 positions.
    (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.

[[Page 75516]]

    (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 are 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 V<INF>2</INF> 
and V<INF>ref</INF>, 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 V<INF>CLmax</INF>.
    Maneuvers with a rate of deceleration of not more than 1 knot per 
second, up to the angle of attack at which V<INF>CLmax</INF> was 
obtained as defined in condition (c)(4) 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; 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.

(g) Speed Associated With Other Requirements

    The design must meet the following modified requirements:
    a. Section 25.145(a): V<INF>min</INF> in lieu of ``stall 
identification.''
    b. Section 25.145(b): V<INF>min</INF> in lieu of V<INF>sw</INF>.
    c. Section 25.1323(d): ``From 1.23 V<INF>SR</INF> to 
V<INF>min</INF>'' in lieu of ``1.23 V<INF>SR</INF> to stall warning 
speed'' and ``speeds below V<INF>min</INF>'' in lieu of ``speeds below 
stall warning.''

(h) 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.

(i) 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.

(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, amendment 121, 
appendix C:
    (i) The V<INF>2</INF> 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 V<INF>min</INF>1g 
is increased in icing conditions, with the ``Take-off Ice'' 
accretion defined in part 25, amendment 121, 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 appendix C, if in the configuration used to 
show compliance with Sec.  25.121(b) with this take-off ice accretion:
    (i) The V<INF>2</INF> 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 V<INF>min</INF>1g 
is increased in icing conditions, with the ``Take-off Ice'' 
accretion defined in 14 CFR part 25, amendment 121, 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:
    (a) In icing conditions, with the most critical of the final take-
off ice accretion(s) defined in appendix C, if in

[[Page 75517]]

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 V<INF>FTO</INF> (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 V<INF>min</INF>1g 
is increased in icing conditions, with the ``Final Take-off Ice'' 
accretion defined in 14 CFR part 25, amendment 121, 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:
    (a) In icing conditions, with the most critical of the approach ice 
accretion(s) defined in 14 CFR part 25, amendment 121, appendix C, as 
applicable, in a configuration corresponding to the normal all-engines-
operating procedure, the V<INF>min</INF>1g for this configuration does 
not exceed 110 percent of the V<INF>min</INF>1g for the related all-
engines-operating landing configuration in icing conditions, with a 
climb speed established with normal landing procedures, but not more 
than 1.4 V<INF>SR</INF> (V<INF>SR</INF> determined in non-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, amendment 121, appendix C, if:
    (i) The V<INF>FTO</INF> 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 in Kansas City, Missouri, on October 27, 2023.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service.
[FR Doc. 2023-24311 Filed 11-2-23; 8:45 am]
BILLING CODE 4910-13-P


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