Proposed Rule2023-24311
Special Conditions: Airbus Model A321neo XLR Airplanes; Flight Envelope Protection, Icing and Non-Icing Conditions; High Incidence Protection.
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
November 3, 2023
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
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.
Full Text
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[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 [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2023-24311]
========================================================================
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.
========================================================================
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 <a href="https://www.regulations.gov/">https://www.regulations.gov/</a> 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
<a href="https://www.regulations.gov/">https://www.regulations.gov/</a> 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 <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>,
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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