Document ID: FAA-2016-9409-0003
Agency: faa
Document Type: Rule
Title: Special Conditions: Cranfield Aerospace Limited, Textron Aviation Inc. Model 525-Series Airplanes; Tamarack Load Alleviation System and Cranfield Winglets-Interaction of Systems and Structures
Posted Date: 2018-07-19T04:00Z

[Federal Register Volume 83, Number 139 (Thursday, July 19, 2018)]
[Rules and Regulations]
[Pages 34022-34028]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-15354]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 23

[Docket No. FAA-2016-9409; Special Conditions No. 23-279A-SC]

Special Conditions: Cranfield Aerospace Limited, Textron Aviation 
Inc. Model 525-Series Airplanes; Tamarack Load Alleviation System and 
Cranfield Winglets--Interaction of Systems and Structures

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Amended final special conditions; request for comments.

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SUMMARY: These amended special conditions are issued for the Textron 
Aviation Inc. Model 525-series airplanes. These airplanes--as modified 
by Cranfield Aerospace Limited--will have a novel or unusual design 
feature associated with the installation of a Tamarack Active 
Technology Load Alleviation System and Cranfield Winglets. The 
applicable airworthiness regulations do not contain adequate or 
appropriate safety standards for this design feature. These amended 
special conditions contain the additional safety standards the 
Administrator considers necessary to establish a level of safety 
equivalent to that established by the existing airworthiness standards, 
change the Type Certificate holder, and remove the special flight 
permit requirement.

DATES: These special conditions are effective July 19, 2018 and are 
applicable on July 10, 2018.
    We must receive your comments by September 17, 2018.

ADDRESSES: Send comments identified by docket number FAA-2016-9409 
using any of the following methods:
    [square] Federal eRegulations Portal: Go to http://www.regulations.gov and follow the online instructions for sending your 
comments electronically.
    [square] 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.
    [square] Hand Delivery of Courier: Deliver comments to the ``Mail'' 
address between 9 a.m. and 5 p.m., Monday through Friday, except 
Federal holidays.
    [square] Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: The FAA will post all comments it receives, without 
change, to http://regulations.gov, including any personal information 
the commenter provides. Using the search function of the docket 
website, anyone can find and read the electronic form of all comments 
received into any FAA docket, including the name of the individual 
sending the comment (or signing the comment for an association, 
business, labor union, etc.). DOT's complete Privacy Act Statement can 
be found in the Federal Register published on April 11, 2000 (65 FR 
19477-19478), as well as at http://DocketsInfo.dot.gov.
    Docket: You can read the background documents or comments received 
at http://www.regulations.gov. Follow the online instructions for 
accessing the docket or go to the Docket Operations in Room @12-140 of 
the West Building

[[Page 34023]]

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: Mike Reyer, Continued Operational 
Safety, ACE-113, Small Airplane Directorate, Aircraft Certification 
Service, 901 Locust, Kansas City, Missouri 64106; telephone (816) 329-
4131; facsimile (816) 329-4090.

SUPPLEMENTARY INFORMATION: 

Reason for No Prior Notice and Comment Before Adoption

    These special conditions have been subjected to the notice and 
comment period previously and this amendment is without substantive 
change from those previously issued. It is unlikely that prior public 
comment would result in a significant change from the substance 
contained herein. Therefore, the FAA has determined that prior public 
notice and comment are unnecessary and finds good cause exists for 
adopting these amended special conditions upon issuance. The FAA is 
requesting comments to allow interested persons to submit views that 
may not have been submitted in response to the prior opportunities for 
comment.

Comments Invited

    We invite 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 special conditions, explain the 
reason for any recommended change, and include supporting data. We will 
consider all comments we receive by the closing date for comments.
    We will consider comments filed late if it is possible to do so 
without incurring additional expense or delay. We may change these 
special conditions based on the comments we receive.

Background

    On January 25, 2016, Cranfield Aerospace Limited (CAL) applied for 
a supplemental type certificate to install winglets on the Textron 
Aviation Inc. (Textron) Model 525, with a Tamarack Active Technology 
Load Alleviation System to mitigate the winglet's adverse structural 
effects. The Textron Model 525 twin-turbofan engine airplane is 
certified in the normal category for eight seats, including a pilot, a 
maximum gross weight of 10,700 pounds, and a maximum altitude of 41,000 
feet mean sea level. Because the applicable airworthiness regulations 
do not contain adequate or appropriate safety standards for this design 
feature, the FAA issued special conditions to provide an equivalent 
level of safety. After notice and opportunity for comment (81 FR 83737, 
November 22, 2016), Special Conditions No. 23-279-SC published in the 
Federal Register on January 5, 2017 (82 FR 1163).
    These special conditions address several issues with the operation 
and failure of the load-relief system. Special Conditions No. 23-279-
SC, paragraph 2(h), Further flights with known load-relief system 
failure, required a special flight permit (``ferry permit'') for 
additional flights after an annunciated failure or obvious system 
failure.
    On February 15, 2018, CAL requested the FAA amend Special Condition 
No. 23-279-SC to remove the paragraph 2(h) and replace it with flight 
limitations used by the European Aviation Safety Agency. In the event 
of a load-relief system failure, these flight limitations allow the 
airplane to be moved to an appropriate maintenance facility without the 
need for a special flight permit.
    The FAA will amend the special conditions to remove the special 
flight permit requirements, but finds no need to include any additional 
requirement regarding flights with known load relief system failure in 
these special conditions. Current regulatory requirements address this 
condition. Inoperative equipment requirements are contained in 14 CFR 
part 91. Section 91.213, Inoperative instruments and equipment, 
prohibits taking off in an aircraft with inoperative instruments or 
equipment unless there is an FAA-approved Minimum Equipment List (MEL) 
for the specific aircraft type. Without an FAA-approved MEL, operators 
must obtain a special flight permit in accordance with Sec. Sec.  
21.197, Special flight permits, and 21.199, Issue of special flight 
permits. Additional operational restrictions are not necessary for 
these special conditions.
    On July 29, 2015, Cessna Aircraft Company transferred Type 
Certificate No. A1WI to Textron. As a result, these proposed amended 
special conditions reflect the current type certificate holder. In 
addition, these special conditions were intended to apply to all Model 
525 airplanes on Type Certificate No. A1WI, and we have clarified that 
in this amendment.

Type Certification Basis

    Under the provisions of Sec.  21.101, Cranfield Aerospace Limited 
must show that the Textron Model 525-series airplanes, as changed, 
continue to meet the applicable provisions of the regulations 
incorporated by reference in Type Certificate No. A1WI, revision 26, or 
the applicable regulations in effect on the date of application for the 
change. The regulations incorporated by reference in the type 
certificate are commonly referred to as the ``original type 
certification basis.'' The regulations incorporated by reference in 
Type Certificate No. A1WI, revision 26, are 14 CFR part 23 effective 
February 1, 1965, amendments 23-1 through 23-38 and 23-40.
    If the Administrator finds the applicable airworthiness regulations 
(i.e., 14 CFR part 23) do not contain adequate or appropriate safety 
standards for the Textron Model 525-series because of a novel or 
unusual design feature, special conditions are prescribed under the 
provisions of Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Textron Model 525-series 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 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type-
certification basis under Sec.  21.101.
    Special conditions are initially applicable to the model for which 
they are issued. Should the applicant apply for a supplemental type 
certificate to modify any other model included on the same type 
certificate to incorporate the same or similar novel or unusual design 
feature, the FAA would apply these special conditions to the other 
model under Sec.  21.101.

Novel or Unusual Design Features

    The Textron Model 525-series will incorporate the following novel 
or unusual design features:

Cranfield winglets with a Tamarack Active Technology Load Alleviation 
System.

Discussion

    For airplanes equipped with systems that affect structural 
performance, either directly or as a result of a failure or 
malfunction, the applicant must take into account the influence of 
these systems and their failure conditions when showing compliance with 
the requirements of part 23, subparts C and D.
    The applicant must use the following criteria for showing 
compliance with these special conditions for airplanes equipped with 
flight control systems, autopilots, stability augmentation systems, 
load alleviation systems, flutter control systems, fuel management 
systems, and other systems that either

[[Page 34024]]

directly or as a result of failure or malfunction affect structural 
performance. If these special conditions are used for other systems, it 
may be necessary to adapt the criteria to the specific system.

Discussion of Comments

    Notice of proposed Special Conditions No. 23-16-03-SC for the 
Cessna Model 525 airplane was published in the Federal Register on 
November 22, 2016 (81 FR 83737). No comments were received, and the 
special conditions were adopted--as proposed--in Special Condition No. 
23-279-SC (82 FR 1163, January 5, 2017). Accordingly, these amended 
special conditions are being issued as final special conditions.

Applicability

    As discussed above, these special conditions are applicable to the 
Textron Model 525-series airplanes. Should Cranfield Aerospace Limited 
apply at a later date for a supplemental type certificate to modify any 
other model included on A1WI, revision 26, to incorporate the same 
novel or unusual design feature, the FAA would apply these special 
conditions 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 and it affects only the applicant who applied to the FAA 
for approval of these features on the airplane.

List of Subjects in 14 CFR Part 23

    Aircraft, Aviation safety, Signs and symbols.

Citation

    The authority citation for these special conditions is as follows:

    Authority:  49 U.S.C. 106(g), 40113, 44701, 44702, 14 CFR 21.16, 
21.101; and 14 CFR 11.38 and 11.19.

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 Textron Aviation Inc. Model 525-series 
airplanes modified by Cranfield Aerospace Limited.

1. Active Technology Load Alleviation System (ATLAS)

SC 23.672 Load Alleviation System

    The load alleviation system must comply with the following:
    (a) A warning, which is clearly distinguishable to the pilot under 
expected flight conditions without requiring the pilot's attention, 
must be provided for any failure in the load alleviation system or in 
any other automatic system that could result in an unsafe condition if 
the pilot was not aware of the failure. Warning systems must not 
activate the control system.
    (b) The design of the load alleviation system or of any other 
automatic system must permit initial counteraction of failures without 
requiring exceptional pilot skill or strength, by either the 
deactivation of the system or a failed portion thereof, or by 
overriding the failure by movement of the flight controls in the normal 
sense.
    (1) If deactivation of the system is used to counteract failures, 
the control for this initial counteraction must be readily accessible 
to each pilot while operating the control wheel and thrust control 
levers.
    (2) If overriding the failure by movement of the flight controls is 
used, the override capability must be operationally demonstrated.
    (c) It must be shown that, after any single failure of the load 
alleviation system, the airplane must be safely controllable when the 
failure or malfunction occurs at any speed or altitude within the 
approved operating limitations that is critical for the type of failure 
being considered;
    (d) It must be shown that, while the system is active or after any 
single failure of the load alleviation system--
    (1) The controllability and maneuverability requirements of part 
23, subpart D, are met within a practical operational flight envelope 
(e.g., speed, altitude, normal acceleration, and airplane 
configuration) that is described in the Airplane Flight Manual (AFM); 
and
    (2) The trim, stability, and stall characteristics are not impaired 
below a level needed to permit continued safe flight and landing.

SC 23.677 Load Alleviation Active Control Surface

    (a) Proper precautions must be taken to prevent inadvertent or 
improper operation of the load alleviation system. It must be 
demonstrated that with the load alleviation system operating throughout 
its operational range, a pilot of average strength and skill level is 
able to continue safe flight with no objectionable increased workload.
    (b) The load alleviation system must be designed so that, when any 
one connecting or transmitting element in the primary flight control 
system fails, adequate control for safe flight and landing is 
available.
    (c) The load alleviation system must be irreversible unless the 
control surface is properly balanced and has no unsafe flutter 
characteristics. The system must have adequate rigidity and reliability 
in the portion of the system from the control surface to the attachment 
of the irreversible unit to the airplane structure.
    (d) It must be demonstrated the airplane is safely controllable and 
a pilot can perform all maneuvers and operations necessary to affect a 
safe landing following any load alleviation system runaway not shown to 
be extremely improbable, allowing for appropriate time delay after 
pilot recognition of the system runaway. The demonstration must be 
conducted at critical airplane weights and center of gravity positions.

SC 23.683 Operation Tests

    (a) It must be shown by operation tests that, when the flight 
control system and the load alleviation systems are operated and loaded 
as prescribed in paragraph (c) of this section, the flight control 
system and load alleviation systems are free from--
    (1) Jamming;
    (2) Excessive friction; and
    (3) Excessive deflection.
    (b) The operation tests in paragraph (a) of this section must also 
show the load alleviation system and associated surfaces do not 
restrict or prevent aileron control surface movements, or cause any 
adverse response of the ailerons, under the loading prescribed in 
paragraph (c) of this section that would prevent continued safe flight 
and landing.
    (c) The prescribed test loads are for the entire load alleviation 
and flight control systems, loads corresponding to the limit air loads 
on the appropriate surfaces.
    Note: Advisory Circular (AC) 23-17C, ``Systems and Equipment Guide 
to Certification of Part 23 Airplanes,'' provides guidance on potential 
methods of compliance with this section and other regulations 
applicable to this STC project.

SC 23.685 Control System Details

    (a) Each detail of the load alleviation system and related moveable 
surfaces must be designed and installed to prevent jamming, chafing, 
and interference from cargo, passengers, loose objects, or the freezing 
of moisture.
    (b) There must be means in the cockpit to prevent the entry of 
foreign objects into places where they would

[[Page 34025]]

jam any one connecting or transmitting element of the load alleviation 
system.
    (c) Each element of the load alleviation system must have design 
features, or must be distinctively and permanently marked, to minimize 
the possibility of incorrect assembly that could result in 
malfunctioning of the control system.

SC 23.697 Load Alleviation System Controls

    (a) The load alleviation control surface must be designed so that 
during normal operation, when the surface has been placed in any 
position, it will not move from that position unless the control is 
adjusted or is moved by the operation of a load alleviation system.
    (b) The rate of movement of the control surface in response to the 
load alleviation system controls must give satisfactory flight and 
performance characteristics under steady or changing conditions of 
airspeed, engine power, attitude, flap configuration, speedbrake 
position, and during landing gear extension and retraction.

SC 23.701 Load Alleviation System Interconnection

    (a) The load alleviation system and related movable surfaces as a 
system must--
    (1) Be synchronized by a mechanical interconnection between the 
movable surfaces or by an approved equivalent means; or
    (2) Be designed so the occurrence of any failure of the system that 
would result in an unsafe flight characteristic of the airplane is 
extremely improbable; or
    (b) The airplane must be shown to have safe flight characteristics 
with any combination of extreme positions of individual movable 
surfaces.
    (c) If an interconnection is used in multiengine airplanes, it must 
be designed to account for unsymmetrical loads resulting from flight 
with the engines on one side of the plane of symmetry inoperative and 
the remaining engines at takeoff power. For single-engine airplanes, 
and multiengine airplanes with no slipstream effects on the load 
alleviation system, it may be assumed that 100 percent of the critical 
air load acts on one side and 70 percent on the other.

Sections 23.675, ``Stops;'' 23.681, ``Limit Load Static Tests;'' and 
23.693, ``Joints''

    The load alleviation system must comply with Sec. Sec.  23.675, 
23.681, and 23.693 as written and no unique special condition will be 
required for these regulations.

Applicability of Control System Regulations to Other Control Systems

    If applicable, other control systems used on the Textron Model 525-
series may require a showing of compliance with Sec. Sec.  23.672, 
23.675, 23.677, 23.681, 23.683, 23.685, 23.693, 23.697, and 23.701 as 
written for this STC project.

2. Interaction of Systems and Structures

    (a) The criteria defined herein only address the direct structural 
consequences of the system responses and performances and cannot be 
considered in isolation but should be included in the overall safety 
evaluation of the airplane. These criteria may in some instances 
duplicate standards already established for this evaluation. These 
criteria are only applicable to structure whose failure could prevent 
continued safe flight and landing. Specific criteria that define 
acceptable limits on handling characteristics or stability requirements 
when operating in the system degraded or inoperative mode are not 
provided in this special condition.
    (b) Depending upon the specific characteristics of the airplane, 
additional studies may be required that go beyond the criteria provided 
in this special condition in order to demonstrate the capability of the 
airplane to meet other realistic conditions such as alternative gust or 
maneuver descriptions for an airplane equipped with a load alleviation 
system.
    (c) The following definitions are applicable to this special 
condition.
    (1) Structural performance: Capability of the airplane to meet the 
structural requirements of 14 CFR part 23.
    (2) Flight limitations: Limitations that can be applied to the 
airplane flight conditions following an in-flight occurrence and that 
are included in the flight manual (e.g., speed limitations, avoidance 
of severe weather conditions, etc.).
    (3) Reserved.
    (4) Probabilistic terms: The probabilistic terms (probable, 
improbable, extremely improbable) used in this special condition are 
the same as those used in Sec.  23.1309. For the purposes of this 
special condition, extremely improbable for normal, utility, and 
acrobatic category airplanes is defined as 10-\8\ per hour. 
For commuter category airplanes, extremely improbable is defined as 
10-\9\ per hour.
    (5) Failure condition: The term failure condition is the same as 
that used in Sec.  23.1309, however this special condition applies only 
to system failure conditions that affect the structural performance of 
the airplane (e.g., system failure conditions that induce loads, change 
the response of the airplane to inputs such as gusts or pilot actions, 
or lower flutter margins).
    (d) General. The following criteria (paragraphs (e) through (i)) 
will be used in determining the influence of a system and its failure 
conditions on the airplane structure.
    (e) System fully operative. With the system fully operative, the 
following apply:
    (1) Limit loads must be derived in all normal operating 
configurations of the system from all the limit conditions specified in 
subpart C (or defined by special condition or equivalent level of 
safety in lieu of those specified in subpart C), taking into account 
any special behavior of such a system or associated functions or any 
effect on the structural performance of the airplane that may occur up 
to the limit loads. In particular, any significant nonlinearity (rate 
of displacement of control surface, thresholds or any other system 
nonlinearities) must be accounted for in a realistic or conservative 
way when deriving limit loads from limit conditions.
    (2) The airplane must meet the strength requirements of part 23 
(static strength and residual strength for failsafe or damage tolerant 
structure), using the specified factors to derive ultimate loads from 
the limit loads defined above. The effect of nonlinearities must be 
investigated beyond limit conditions to ensure the behavior of the 
system presents no anomaly compared to the behavior below limit 
conditions. However, conditions beyond limit conditions need not be 
considered when it can be shown that the airplane has design features 
that will not allow it to exceed those limit conditions.
    (3) The airplane must meet the aeroelastic stability requirements 
of Sec.  23.629.
    (f) System in the failure condition. For any system failure 
condition not shown to be extremely improbable, the following apply:
    (1) At the time of occurrence. Starting from 1-g level flight 
conditions, a realistic scenario, including pilot corrective actions, 
must be established to determine the loads occurring at the time of 
failure and immediately after failure.
    (i) For static strength substantiation, these loads, multiplied by 
an appropriate factor of safety that is related to the probability of 
occurrence of the failure, are ultimate loads to be considered for 
design. The factor of safety is defined in figure 1.

[[Page 34026]]

[GRAPHIC] [TIFF OMITTED] TR19JY18.005

    (ii) For residual strength substantiation, the airplane must be 
able to withstand two thirds of the ultimate loads defined in 
subparagraph (f)(1)(i).
    (iii) For pressurized cabins, these loads must be combined with the 
normal operating differential pressure.
    (iv) Freedom from aeroelastic instability must be shown up to the 
speeds defined in Sec.  23.629(f). For failure conditions that result 
in speeds beyond VD/MD, freedom from aeroelastic 
instability must be shown to increased speeds, so that the margins 
intended by Sec.  23.629(f) are maintained.
    (v) Failures of the system that result in forced structural 
vibrations (oscillatory failures) must not produce loads that could 
result in detrimental deformation of primary structure.
    (2) For the continuation of the flight. For the airplane, in the 
system failed state and considering any appropriate reconfiguration and 
flight limitations, the following apply:
    (i) The loads derived from the following conditions (or defined by 
special condition or equivalent level of safety in lieu of the 
following conditions) at speeds up to VC/MC, or 
the speed limitation prescribed for the remainder of the flight, must 
be determined:
    (A) The limit symmetrical maneuvering conditions specified in 
Sec. Sec.  23.321, 23.331, 23.333, 23.345, 23.421, 23.423, and 23.445.
    (B) The limit gust and turbulence conditions specified in 
Sec. Sec.  23.341, 23.345, 23.425, 23.443, and 23.445.
    (C) The limit rolling conditions specified in Sec.  23.349 and the 
limit unsymmetrical conditions specified in Sec. Sec.  23.347, 23.427, 
and 23.445.
    (D) The limit yaw maneuvering conditions specified in Sec. Sec.  
23.351, 23.441, and 23.445.
    (E) The limit ground loading conditions specified in Sec. Sec.  
23.473 and 23.493.
    (ii) For static strength substantiation, each part of the structure 
must be able to withstand the loads in paragraph (f)(2)(i) of this 
special condition multiplied by a factor of safety depending on the 
probability of being in this failure state. The factor of safety is 
defined in figure 2.

[[Page 34027]]

[GRAPHIC] [TIFF OMITTED] TR19JY18.006

    (iii) For residual strength substantiation, the airplane must be 
able to withstand two thirds of the ultimate loads defined in paragraph 
(f)(2)(ii) of this special condition. For pressurized cabins, these 
loads must be combined with the normal operating pressure differential.
    (iv) If the loads induced by the failure condition have a 
significant effect on fatigue or damage tolerance then their effects 
must be taken into account.
    (v) Freedom from aeroelastic instability must be shown up to a 
speed determined from figure 3. Flutter clearance speeds V' and V'' may 
be based on the speed limitation specified for the remainder of the 
flight using the margins defined by Sec.  23.629.

[[Page 34028]]

[GRAPHIC] [TIFF OMITTED] TR19JY18.007

    (vi) Freedom from aeroelastic instability must also be shown up to 
V' in figure 3 above, for any probable system failure condition 
combined with any damage required or selected for investigation by 
Sec. Sec.  23.571 through 23.574.
    (3) Consideration of certain failure conditions may be required by 
other sections of 14 CFR part 23 regardless of calculated system 
reliability. Where analysis shows the probability of these failure 
conditions to be less than 10-8 for normal, utility, or 
acrobatic category airplanes or less than 10-9 for commuter 
category airplanes, criteria other than those specified in this 
paragraph may be used for structural substantiation to show continued 
safe flight and landing.
    (g) Failure indications. For system failure detection and 
indication, the following apply:
    (1) The system must be checked for failure conditions, not 
extremely improbable, that degrade the structural capability below the 
level required by part 23 or significantly reduce the reliability of 
the remaining system. As far as reasonably practicable, the flightcrew 
must be made aware of these failures before flight. Certain elements of 
the control system, such as mechanical and hydraulic components, may 
use special periodic inspections, and electronic components may use 
daily checks, in lieu of detection and indication systems to achieve 
the objective of this requirement. These certification maintenance 
requirements must be limited to components that are not readily 
detectable by normal detection and indication systems and where service 
history shows that inspections will provide an adequate level of 
safety.
    (2) The existence of any failure condition, not extremely 
improbable, during flight that could significantly affect the 
structural capability of the airplane and for which the associated 
reduction in airworthiness can be minimized by suitable flight 
limitations, must be signaled to the flightcrew. The probability of not 
annunciating these failure conditions must be extremely improbable 
(unannunciated failure). For example, failure conditions that result in 
a factor of safety between the airplane strength and the loads of 
subpart C below 1.25, or flutter margins below V'', must be signaled to 
the flightcrew during flight.
    (h) Fatigue and damage tolerance. If any system failure would have 
a significant effect on the fatigue or damage evaluations required in 
Sec. Sec.  23.571 through 23.574, then these effects must be taken into 
account.

    Issued in Kansas City, Missouri, on July 10, 2018.
Pat Mullen,
Manager, Small Airplane Standard Branch, Aircraft Certification 
Service.
[FR Doc. 2018-15354 Filed 7-18-18; 8:45 am]
 BILLING CODE 4910-13-P