Rule2024-10646
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
May 16, 2024
Effective
June 17, 2024
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
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.
Full Text
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<title>Federal Register, Volume 89 Issue 96 (Thursday, May 16, 2024)</title>
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[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 [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[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 <a href="/cdn-cgi/l/email-protection#1c686e7365327d327e6e736b725c7a7d7d327b736a"><span class="__cf_email__" data-cfemail="88fcfae7f1a6e9a6eafae7ffe6c8eee9e9a6efe7fe">[email protected]</span></a>.
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 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 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\ <a href="https://www.faa.gov/regulations_policies/rulemaking/committees/documents/media/09%20-%20FTHWG_Final_Report_Phase_2_RevA__Apr_2017.pdf">https://www.faa.gov/regulations_policies/rulemaking/committees/documents/media/09%20-%20FTHWG_Final_Report_Phase_2_RevA__Apr_2017.pdf</a>.
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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 V<INF>min</INF>1g 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 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. 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, 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 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, 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] TR16MY24.088
Where:
V<INF>CLmax</INF> = the 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 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
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 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 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 VCLmax
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 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): V<INF>min</INF> in lieu of ``stall
identification.''
(2) Section 25.145(b): V<INF>min</INF> in lieu of V<INF>sw</INF>.
(3) 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.''
(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 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, 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 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, 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 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, 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 V<INF>SR</INF> (V<INF>SR</INF> determined in non-
icing conditions), may be used if in a configuration corresponding to
the normal all-engines-operating procedure where 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.
(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 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 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
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