83_FR_34161 83 FR 34022 - Special Conditions: Cranfield Aerospace Limited, Textron Aviation Inc. Model 525-Series Airplanes; Tamarack Load Alleviation System and Cranfield Winglets-Interaction of Systems and Structures

83 FR 34022 - Special Conditions: Cranfield Aerospace Limited, Textron Aviation Inc. Model 525-Series Airplanes; Tamarack Load Alleviation System and Cranfield Winglets-Interaction of Systems and Structures

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration

Federal Register Volume 83, Issue 139 (July 19, 2018)

Page Range34022-34028
FR Document2018-15354

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.

Federal Register, Volume 83 Issue 139 (Thursday, July 19, 2018)
[Federal Register Volume 83, Number 139 (Thursday, July 19, 2018)]
[Rules and Regulations]
[Pages 34022-34028]
From the Federal Register Online  [www.thefederalregister.org]
[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



                                              34022              Federal Register / Vol. 83, No. 139 / Thursday, July 19, 2018 / Rules and Regulations

                                              counties for the 504 Rural Pilot, which                  120.3 of its regulations, which provides               ACTION: Amended final special
                                              may not be the same as the rural areas                   that the SBA Administrator may                         conditions; request for comments.
                                              identified by the U.S. Department of                     suspend, modify or waive rules for a
                                              Agriculture.) SBA Regions are defined                    limited period of time to test new                     SUMMARY:    These amended special
                                              as follows:                                              programs or ideas. The 504 Rural Pilot                 conditions are issued for the Textron
                                                                                                                                                              Aviation Inc. Model 525-series
                                              • Region I: Connecticut, Maine,                          will be available for a two year period
                                                                                                       beginning today.                                       airplanes. These airplanes—as modified
                                                 Massachusetts, New Hampshire,
                                                                                                          SBA will limit the number of loans                  by Cranfield Aerospace Limited—will
                                                 Rhode Island, and Vermont
                                              • Region II: New York, New Jersey,                       made under the 504 Rural Pilot to not                  have a novel or unusual design feature
                                                 Puerto Rico, and The U.S. Virgin                      more than ten percent of the total                     associated with the installation of a
                                                 Islands                                               number of 504 loans guaranteed by SBA                  Tamarack Active Technology Load
                                              • Region III: Delaware, Maryland,                                                                               Alleviation System and Cranfield
                                                                                                       in any fiscal year. While SBA does not
                                                 Pennsylvania, Virginia, Washington,                                                                          Winglets. The applicable airworthiness
                                                                                                       expect the number of 504 Rural Pilot
                                                 DC, and West Virginia                                                                                        regulations do not contain adequate or
                                                                                                       loans to reach that limit, SBA will
                                              • Region IV: Alabama, Florida, Georgia,                                                                         appropriate safety standards for this
                                                                                                       provide public notice of the need to
                                                 Kentucky, Mississippi, North                                                                                 design feature. These amended special
                                                                                                       suspend lending under the 504 Rural
                                                 Carolina, South Carolina, and                                                                                conditions contain the additional safety
                                                                                                       Pilot for the remainder of the fiscal year
                                                 Tennessee                                                                                                    standards the Administrator considers
                                                                                                       if SBA determines that the number of
                                              • Region V: Illinois, Indiana, Michigan,                 pilot loans is approaching the limit.
                                                                                                                                                              necessary to establish a level of safety
                                                 Minnesota, Ohio, and Wisconsin                                                                               equivalent to that established by the
                                                                                                          SBA will be using the following
                                              • Region VI: Arkansas, Louisiana, New                    criteria to evaluate the 504 Rural Pilot
                                                                                                                                                              existing airworthiness standards, change
                                                 Mexico, Oklahoma, and Texas                                                                                  the Type Certificate holder, and remove
                                                                                                       to determine how well it is achieving its
                                              • Region VII: Iowa, Kansas, Missouri,                                                                           the special flight permit requirement.
                                                                                                       objectives and other aspects of
                                                 and Nebraska                                                                                                 DATES: These special conditions are
                                              • Region VIII: Colorado, Montana,                        performance: (1) The measurable
                                                                                                       objectives to be achieved through the                  effective July 19, 2018 and are
                                                 North Dakota, South Dakota, Utah,                                                                            applicable on July 10, 2018.
                                                 and Wyoming                                           504 Rural Pilot, including the number of
                                                                                                       small business concerns served, and the                   We must receive your comments by
                                              • Region IX: Arizona, California, Guam,                                                                         September 17, 2018.
                                                 Hawaii, and Nevada                                    delinquency and default rates on the
                                                                                                       504 Rural Pilot loans compared to                      ADDRESSES: Send comments identified
                                              • Region X: Alaska, Idaho, Oregon, and                                                                          by docket number FAA–2016–9409
                                                 Washington.                                           regular 504 loans; (2) the number of
                                                                                                       CDCs that participate in the 504 Rural                 using any of the following methods:
                                                 In making, closing, servicing, or                                                                               b Federal eRegulations Portal: Go to
                                              liquidating a 504 Rural Pilot loan, CDCs                 Pilot and their performance in making
                                                                                                       and servicing 504 Rural Pilot loans; and               http://www.regulations.gov and follow
                                              must follow all other Loan Program                                                                              the online instructions for sending your
                                              Requirements under the 504 Loan                          (3) the costs and standards of
                                                                                                       performance which, in order to be                      comments electronically.
                                              Program, except that 504 Rural Pilot                                                                               b Mail: Send comments to Docket
                                              loans cannot be made using the CDC’s                     acceptable, must not impact the overall
                                                                                                                                                              Operations, M–30, U.S. Department of
                                              delegated authority (i.e., PCLP or ALP                   subsidy rate for the 504 Loan Program.
                                                                                                                                                              Transportation (DOT), 1200 New Jersey
                                              authority). Although, as described                       For data collections to evaluate the
                                                                                                                                                              Avenue SE, Room W12–140, West
                                              above, CDCs will not be required ‘‘to                    effectiveness of this pilot, SBA will use
                                                                                                                                                              Building Ground Floor, Washington, DC
                                              demonstrate’’ that they can adequately                   ETran, SBA’s electronic system for loan
                                                                                                                                                              20590–0001.
                                              fulfill their 504 program responsibilities               submission and servicing.                                 b Hand Delivery of Courier: Deliver
                                              for each 504 Rural Pilot loan before                          Authority: 13 CFR 120.3.                          comments to the ‘‘Mail’’ address
                                              making the loan, CDCs will still be                        Dated: July 6, 2018.                                 between 9 a.m. and 5 p.m., Monday
                                              expected to fulfill all such program                     Linda E. McMahon,                                      through Friday, except Federal holidays.
                                              responsibilities with respect to these                   Administrator.
                                                                                                                                                                 b Fax: Fax comments to Docket
                                              loans.                                                                                                          Operations at 202–493–2251.
                                                                                                       [FR Doc. 2018–15312 Filed 7–18–18; 8:45 am]
                                                 Unlike a Multi-State CDC, a CDC                                                                                 Privacy: The FAA will post all
                                              making a loan under this pilot will not                  BILLING CODE 8025–01–P                                 comments it receives, without change,
                                              be required to establish a separate loan                                                                        to http://regulations.gov, including any
                                              committee to cover the State in which                                                                           personal information the commenter
                                              the rural 504 Project is located. In                                                                            provides. Using the search function of
                                              addition, the CDC must advise the local                  DEPARTMENT OF TRANSPORTATION                           the docket website, anyone can find and
                                              District Counsel where the 504 Project                   Federal Aviation Administration                        read the electronic form of all comments
                                              is located which Designated Attorney,                                                                           received into any FAA docket,
                                              or other attorney, will be closing the                   14 CFR Part 23                                         including the name of the individual
                                              loan. (The attorney must be licensed in                                                                         sending the comment (or signing the
                                              the State where the loan is being made.)                                                                        comment for an association, business,
                                              CDCs should note that the CDC may not                    [Docket No. FAA–2016–9409; Special                     labor union, etc.). DOT’s complete
                                                                                                       Conditions No. 23–279A–SC]
                                              close the loan as an expedited loan                                                                             Privacy Act Statement can be found in
                                              unless the attorney is a Designated                      Special Conditions: Cranfield                          the Federal Register published on April
                                              Attorney licensed to practice in the                     Aerospace Limited, Textron Aviation                    11, 2000 (65 FR 19477–19478), as well
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                                              State where the 504 Project is located.                  Inc. Model 525-Series Airplanes;                       as at http://DocketsInfo.dot.gov.
                                              The CDC is responsible for notifying the                 Tamarack Load Alleviation System and                      Docket: You can read the background
                                              SLPC that a 504 loan application is                      Cranfield Winglets—Interaction of                      documents or comments received at
                                              being submitted under the 504 Rural                      Systems and Structures                                 http://www.regulations.gov. Follow the
                                              Pilot.                                                                                                          online instructions for accessing the
                                                 SBA’s waiver of the above                             AGENCY:Federal Aviation                                docket or go to the Docket Operations in
                                              requirements is authorized by 13 CFR                     Administration (FAA), DOT.                             Room @12–140 of the West Building


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                                                                 Federal Register / Vol. 83, No. 139 / Thursday, July 19, 2018 / Rules and Regulations                                          34023

                                              Ground Floor at 1200 New Jersey                          equivalent level of safety. After notice              the date of application for the change.
                                              Avenue SE, Washington, DC, between 9                     and opportunity for comment (81 FR                    The regulations incorporated by
                                              a.m., and 5 p.m., Monday through                         83737, November 22, 2016), Special                    reference in the type certificate are
                                              Friday, except Federal holidays.                         Conditions No. 23–279–SC published in                 commonly referred to as the ‘‘original
                                              FOR FURTHER INFORMATION CONTACT:                         the Federal Register on January 5, 2017               type certification basis.’’ The regulations
                                              Mike Reyer, Continued Operational                        (82 FR 1163).                                         incorporated by reference in Type
                                              Safety, ACE–113, Small Airplane                             These special conditions address                   Certificate No. A1WI, revision 26, are 14
                                              Directorate, Aircraft Certification                      several issues with the operation and                 CFR part 23 effective February 1, 1965,
                                              Service, 901 Locust, Kansas City,                        failure of the load-relief system. Special            amendments 23–1 through 23–38 and
                                              Missouri 64106; telephone (816) 329–                     Conditions No. 23–279–SC, paragraph                   23–40.
                                              4131; facsimile (816) 329–4090.                          2(h), Further flights with known load-                   If the Administrator finds the
                                              SUPPLEMENTARY INFORMATION:                               relief system failure, required a special             applicable airworthiness regulations
                                                                                                       flight permit (‘‘ferry permit’’) for                  (i.e., 14 CFR part 23) do not contain
                                              Reason for No Prior Notice and                           additional flights after an annunciated               adequate or appropriate safety standards
                                              Comment Before Adoption                                  failure or obvious system failure.                    for the Textron Model 525-series
                                                 These special conditions have been                       On February 15, 2018, CAL requested                because of a novel or unusual design
                                              subjected to the notice and comment                      the FAA amend Special Condition No.                   feature, special conditions are
                                              period previously and this amendment                     23–279–SC to remove the paragraph                     prescribed under the provisions of
                                              is without substantive change from                       2(h) and replace it with flight                       § 21.16.
                                              those previously issued. It is unlikely                  limitations used by the European                         In addition to the applicable
                                              that prior public comment would result                   Aviation Safety Agency. In the event of               airworthiness regulations and special
                                              in a significant change from the                         a load-relief system failure, these flight            conditions, the Textron Model 525-
                                              substance contained herein. Therefore,                   limitations allow the airplane to be                  series must comply with the fuel vent
                                              the FAA has determined that prior                        moved to an appropriate maintenance                   and exhaust emission requirements of
                                              public notice and comment are                            facility without the need for a special               14 CFR part 34 and the noise
                                              unnecessary and finds good cause exists                  flight permit.                                        certification requirements of 14 CFR
                                              for adopting these amended special                          The FAA will amend the special                     part 36.
                                              conditions upon issuance. The FAA is                     conditions to remove the special flight                  The FAA issues special conditions, as
                                              requesting comments to allow interested                  permit requirements, but finds no need                defined in 14 CFR 11.19, in accordance
                                              persons to submit views that may not                     to include any additional requirement                 with § 11.38, and they become part of
                                              have been submitted in response to the                   regarding flights with known load relief              the type-certification basis under
                                              prior opportunities for comment.                         system failure in these special                       § 21.101.
                                                                                                       conditions. Current regulatory                           Special conditions are initially
                                              Comments Invited                                         requirements address this condition.                  applicable to the model for which they
                                                 We invite interested people to take                   Inoperative equipment requirements are                are issued. Should the applicant apply
                                              part in this rulemaking by sending                       contained in 14 CFR part 91. Section                  for a supplemental type certificate to
                                              written comments, data, or views. The                    91.213, Inoperative instruments and                   modify any other model included on the
                                              most helpful comments reference a                        equipment, prohibits taking off in an                 same type certificate to incorporate the
                                              specific portion of the special                          aircraft with inoperative instruments or              same or similar novel or unusual design
                                              conditions, explain the reason for any                   equipment unless there is an FAA-                     feature, the FAA would apply these
                                              recommended change, and include                          approved Minimum Equipment List                       special conditions to the other model
                                              supporting data. We will consider all                    (MEL) for the specific aircraft type.                 under § 21.101.
                                              comments we receive by the closing                       Without an FAA-approved MEL,
                                                                                                       operators must obtain a special flight                Novel or Unusual Design Features
                                              date for comments.
                                                 We will consider comments filed late                  permit in accordance with §§ 21.197,                    The Textron Model 525-series will
                                              if it is possible to do so without                       Special flight permits, and 21.199, Issue             incorporate the following novel or
                                              incurring additional expense or delay.                   of special flight permits. Additional                 unusual design features:
                                              We may change these special conditions                   operational restrictions are not                      Cranfield winglets with a Tamarack
                                              based on the comments we receive.                        necessary for these special conditions.                 Active Technology Load Alleviation
                                                                                                          On July 29, 2015, Cessna Aircraft                    System.
                                              Background
                                                                                                       Company transferred Type Certificate
                                                 On January 25, 2016, Cranfield                        No. A1WI to Textron. As a result, these               Discussion
                                              Aerospace Limited (CAL) applied for a                    proposed amended special conditions                     For airplanes equipped with systems
                                              supplemental type certificate to install                 reflect the current type certificate                  that affect structural performance, either
                                              winglets on the Textron Aviation Inc.                    holder. In addition, these special                    directly or as a result of a failure or
                                              (Textron) Model 525, with a Tamarack                     conditions were intended to apply to all              malfunction, the applicant must take
                                              Active Technology Load Alleviation                       Model 525 airplanes on Type Certificate               into account the influence of these
                                              System to mitigate the winglet’s adverse                 No. A1WI, and we have clarified that in               systems and their failure conditions
                                              structural effects. The Textron Model                    this amendment.                                       when showing compliance with the
                                              525 twin-turbofan engine airplane is                                                                           requirements of part 23, subparts C
                                              certified in the normal category for eight               Type Certification Basis                              and D.
                                              seats, including a pilot, a maximum                        Under the provisions of § 21.101,                     The applicant must use the following
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                                              gross weight of 10,700 pounds, and a                     Cranfield Aerospace Limited must show                 criteria for showing compliance with
                                              maximum altitude of 41,000 feet mean                     that the Textron Model 525-series                     these special conditions for airplanes
                                              sea level. Because the applicable                        airplanes, as changed, continue to meet               equipped with flight control systems,
                                              airworthiness regulations do not contain                 the applicable provisions of the                      autopilots, stability augmentation
                                              adequate or appropriate safety standards                 regulations incorporated by reference in              systems, load alleviation systems, flutter
                                              for this design feature, the FAA issued                  Type Certificate No. A1WI, revision 26,               control systems, fuel management
                                              special conditions to provide an                         or the applicable regulations in effect on            systems, and other systems that either


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                                              34024              Federal Register / Vol. 83, No. 139 / Thursday, July 19, 2018 / Rules and Regulations

                                              directly or as a result of failure or                       (a) A warning, which is clearly                    adequate control for safe flight and
                                              malfunction affect structural                            distinguishable to the pilot under                    landing is available.
                                              performance. If these special conditions                 expected flight conditions without                       (c) The load alleviation system must
                                              are used for other systems, it may be                    requiring the pilot’s attention, must be              be irreversible unless the control surface
                                              necessary to adapt the criteria to the                   provided for any failure in the load                  is properly balanced and has no unsafe
                                              specific system.                                         alleviation system or in any other                    flutter characteristics. The system must
                                                                                                       automatic system that could result in an              have adequate rigidity and reliability in
                                              Discussion of Comments
                                                                                                       unsafe condition if the pilot was not                 the portion of the system from the
                                                Notice of proposed Special                             aware of the failure. Warning systems                 control surface to the attachment of the
                                              Conditions No. 23–16–03–SC for the                       must not activate the control system.                 irreversible unit to the airplane
                                              Cessna Model 525 airplane was                               (b) The design of the load alleviation             structure.
                                              published in the Federal Register on                     system or of any other automatic system                  (d) It must be demonstrated the
                                              November 22, 2016 (81 FR 83737). No                      must permit initial counteraction of                  airplane is safely controllable and a
                                              comments were received, and the                          failures without requiring exceptional                pilot can perform all maneuvers and
                                              special conditions were adopted—as                       pilot skill or strength, by either the                operations necessary to affect a safe
                                              proposed—in Special Condition No. 23–                    deactivation of the system or a failed                landing following any load alleviation
                                              279–SC (82 FR 1163, January 5, 2017).                    portion thereof, or by overriding the                 system runaway not shown to be
                                              Accordingly, these amended special                       failure by movement of the flight                     extremely improbable, allowing for
                                              conditions are being issued as final                     controls in the normal sense.                         appropriate time delay after pilot
                                              special conditions.                                         (1) If deactivation of the system is               recognition of the system runaway. The
                                              Applicability                                            used to counteract failures, the control              demonstration must be conducted at
                                                                                                       for this initial counteraction must be                critical airplane weights and center of
                                                 As discussed above, these special                                                                           gravity positions.
                                                                                                       readily accessible to each pilot while
                                              conditions are applicable to the Textron
                                                                                                       operating the control wheel and thrust                SC 23.683 Operation Tests
                                              Model 525-series airplanes. Should
                                                                                                       control levers.
                                              Cranfield Aerospace Limited apply at a                                                                            (a) It must be shown by operation
                                                                                                          (2) If overriding the failure by
                                              later date for a supplemental type                                                                             tests that, when the flight control system
                                                                                                       movement of the flight controls is used,
                                              certificate to modify any other model                                                                          and the load alleviation systems are
                                                                                                       the override capability must be
                                              included on A1WI, revision 26, to                                                                              operated and loaded as prescribed in
                                                                                                       operationally demonstrated.
                                              incorporate the same novel or unusual                                                                          paragraph (c) of this section, the flight
                                              design feature, the FAA would apply                         (c) It must be shown that, after any
                                                                                                       single failure of the load alleviation                control system and load alleviation
                                              these special conditions to that model as                                                                      systems are free from—
                                              well.                                                    system, the airplane must be safely
                                                                                                                                                                (1) Jamming;
                                                                                                       controllable when the failure or                         (2) Excessive friction; and
                                              Conclusion                                               malfunction occurs at any speed or                       (3) Excessive deflection.
                                                This action affects only certain novel                 altitude within the approved operating                   (b) The operation tests in paragraph
                                              or unusual design features on one model                  limitations that is critical for the type of          (a) of this section must also show the
                                              series of airplanes. It is not a rule of                 failure being considered;                             load alleviation system and associated
                                              general applicability and it affects only                   (d) It must be shown that, while the               surfaces do not restrict or prevent
                                              the applicant who applied to the FAA                     system is active or after any single                  aileron control surface movements, or
                                              for approval of these features on the                    failure of the load alleviation system—               cause any adverse response of the
                                              airplane.                                                   (1) The controllability and                        ailerons, under the loading prescribed
                                                                                                       maneuverability requirements of part                  in paragraph (c) of this section that
                                              List of Subjects in 14 CFR Part 23                       23, subpart D, are met within a practical             would prevent continued safe flight and
                                                Aircraft, Aviation safety, Signs and                   operational flight envelope (e.g., speed,             landing.
                                              symbols.                                                 altitude, normal acceleration, and                       (c) The prescribed test loads are for
                                                                                                       airplane configuration) that is described             the entire load alleviation and flight
                                              Citation
                                                                                                       in the Airplane Flight Manual (AFM);                  control systems, loads corresponding to
                                                The authority citation for these                       and                                                   the limit air loads on the appropriate
                                              special conditions is as follows:                           (2) The trim, stability, and stall                 surfaces.
                                                Authority: 49 U.S.C. 106(g), 40113, 44701,             characteristics are not impaired below a                 Note: Advisory Circular (AC) 23–17C,
                                              44702, 14 CFR 21.16, 21.101; and 14 CFR                  level needed to permit continued safe                 ‘‘Systems and Equipment Guide to
                                              11.38 and 11.19.                                         flight and landing.                                   Certification of Part 23 Airplanes,’’
                                              The Special Conditions                                   SC 23.677 Load Alleviation Active                     provides guidance on potential methods
                                                                                                       Control Surface                                       of compliance with this section and
                                                Accordingly, pursuant to the
                                                                                                                                                             other regulations applicable to this STC
                                              authority delegated to me by the                            (a) Proper precautions must be taken               project.
                                              Administrator, the following special                     to prevent inadvertent or improper
                                              conditions are issued as part of the type                operation of the load alleviation system.             SC 23.685 Control System Details
                                              certification basis for Textron Aviation                 It must be demonstrated that with the                   (a) Each detail of the load alleviation
                                              Inc. Model 525-series airplanes                          load alleviation system operating                     system and related moveable surfaces
                                              modified by Cranfield Aerospace                          throughout its operational range, a pilot             must be designed and installed to
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                                              Limited.                                                 of average strength and skill level is able           prevent jamming, chafing, and
                                              1. Active Technology Load Alleviation                    to continue safe flight with no                       interference from cargo, passengers,
                                              System (ATLAS)                                           objectionable increased workload.                     loose objects, or the freezing of
                                                                                                          (b) The load alleviation system must               moisture.
                                              SC 23.672 Load Alleviation System                        be designed so that, when any one                       (b) There must be means in the
                                                The load alleviation system must                       connecting or transmitting element in                 cockpit to prevent the entry of foreign
                                              comply with the following:                               the primary flight control system fails,              objects into places where they would


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                                                                  Federal Register / Vol. 83, No. 139 / Thursday, July 19, 2018 / Rules and Regulations                                          34025

                                              jam any one connecting or transmitting                    Applicability of Control System                       failure conditions that induce loads,
                                              element of the load alleviation system.                   Regulations to Other Control Systems                  change the response of the airplane to
                                                 (c) Each element of the load                             If applicable, other control systems                inputs such as gusts or pilot actions, or
                                              alleviation system must have design                       used on the Textron Model 525-series                  lower flutter margins).
                                              features, or must be distinctively and                    may require a showing of compliance                      (d) General. The following criteria
                                              permanently marked, to minimize the                       with §§ 23.672, 23.675, 23.677, 23.681,               (paragraphs (e) through (i)) will be used
                                              possibility of incorrect assembly that                    23.683, 23.685, 23.693, 23.697, and                   in determining the influence of a system
                                              could result in malfunctioning of the                     23.701 as written for this STC project.               and its failure conditions on the
                                              control system.                                                                                                 airplane structure.
                                                                                                        2. Interaction of Systems and Structures                 (e) System fully operative. With the
                                              SC 23.697        Load Alleviation System
                                                                                                           (a) The criteria defined herein only               system fully operative, the following
                                              Controls
                                                                                                        address the direct structural                         apply:
                                                 (a) The load alleviation control                       consequences of the system responses                     (1) Limit loads must be derived in all
                                              surface must be designed so that during                   and performances and cannot be                        normal operating configurations of the
                                              normal operation, when the surface has                    considered in isolation but should be                 system from all the limit conditions
                                              been placed in any position, it will not                  included in the overall safety evaluation             specified in subpart C (or defined by
                                              move from that position unless the                        of the airplane. These criteria may in                special condition or equivalent level of
                                              control is adjusted or is moved by the                    some instances duplicate standards                    safety in lieu of those specified in
                                              operation of a load alleviation system.                   already established for this evaluation.              subpart C), taking into account any
                                                 (b) The rate of movement of the                        These criteria are only applicable to                 special behavior of such a system or
                                              control surface in response to the load                   structure whose failure could prevent                 associated functions or any effect on the
                                              alleviation system controls must give                     continued safe flight and landing.                    structural performance of the airplane
                                              satisfactory flight and performance                       Specific criteria that define acceptable              that may occur up to the limit loads. In
                                              characteristics under steady or changing                  limits on handling characteristics or                 particular, any significant nonlinearity
                                              conditions of airspeed, engine power,                     stability requirements when operating                 (rate of displacement of control surface,
                                              attitude, flap configuration, speedbrake                  in the system degraded or inoperative                 thresholds or any other system
                                              position, and during landing gear                         mode are not provided in this special                 nonlinearities) must be accounted for in
                                              extension and retraction.                                 condition.                                            a realistic or conservative way when
                                                                                                           (b) Depending upon the specific                    deriving limit loads from limit
                                              SC 23.701 Load Alleviation System
                                                                                                        characteristics of the airplane,                      conditions.
                                              Interconnection
                                                                                                        additional studies may be required that                  (2) The airplane must meet the
                                                 (a) The load alleviation system and                    go beyond the criteria provided in this               strength requirements of part 23 (static
                                              related movable surfaces as a system                      special condition in order to                         strength and residual strength for
                                              must—                                                     demonstrate the capability of the                     failsafe or damage tolerant structure),
                                                 (1) Be synchronized by a mechanical                    airplane to meet other realistic                      using the specified factors to derive
                                              interconnection between the movable                       conditions such as alternative gust or                ultimate loads from the limit loads
                                              surfaces or by an approved equivalent                     maneuver descriptions for an airplane                 defined above. The effect of
                                              means; or                                                 equipped with a load alleviation system.              nonlinearities must be investigated
                                                 (2) Be designed so the occurrence of                      (c) The following definitions are                  beyond limit conditions to ensure the
                                              any failure of the system that would                      applicable to this special condition.                 behavior of the system presents no
                                              result in an unsafe flight characteristic                    (1) Structural performance: Capability             anomaly compared to the behavior
                                              of the airplane is extremely improbable;                  of the airplane to meet the structural                below limit conditions. However,
                                              or                                                        requirements of 14 CFR part 23.                       conditions beyond limit conditions
                                                 (b) The airplane must be shown to                         (2) Flight limitations: Limitations that           need not be considered when it can be
                                              have safe flight characteristics with any                 can be applied to the airplane flight                 shown that the airplane has design
                                              combination of extreme positions of                       conditions following an in-flight                     features that will not allow it to exceed
                                              individual movable surfaces.                              occurrence and that are included in the               those limit conditions.
                                                 (c) If an interconnection is used in                   flight manual (e.g., speed limitations,                  (3) The airplane must meet the
                                              multiengine airplanes, it must be                         avoidance of severe weather conditions,               aeroelastic stability requirements of
                                              designed to account for unsymmetrical                     etc.).                                                § 23.629.
                                              loads resulting from flight with the                         (3) Reserved.                                         (f) System in the failure condition. For
                                              engines on one side of the plane of                          (4) Probabilistic terms: The                       any system failure condition not shown
                                              symmetry inoperative and the                              probabilistic terms (probable,                        to be extremely improbable, the
                                              remaining engines at takeoff power. For                   improbable, extremely improbable) used                following apply:
                                              single-engine airplanes, and                              in this special condition are the same as                (1) At the time of occurrence. Starting
                                              multiengine airplanes with no                             those used in § 23.1309. For the                      from 1-g level flight conditions, a
                                              slipstream effects on the load alleviation                purposes of this special condition,                   realistic scenario, including pilot
                                              system, it may be assumed that 100                        extremely improbable for normal,                      corrective actions, must be established
                                              percent of the critical air load acts on                  utility, and acrobatic category airplanes             to determine the loads occurring at the
                                              one side and 70 percent on the other.                     is defined as 10¥8 per hour. For                      time of failure and immediately after
                                                                                                        commuter category airplanes, extremely                failure.
                                              Sections 23.675, ‘‘Stops;’’ 23.681, ‘‘Limit
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                                                                                                        improbable is defined as 10¥9 per hour.                  (i) For static strength substantiation,
                                              Load Static Tests;’’ and 23.693, ‘‘Joints’’                  (5) Failure condition: The term failure            these loads, multiplied by an
                                                The load alleviation system must                        condition is the same as that used in                 appropriate factor of safety that is
                                              comply with §§ 23.675, 23.681, and                        § 23.1309, however this special                       related to the probability of occurrence
                                              23.693 as written and no unique special                   condition applies only to system failure              of the failure, are ultimate loads to be
                                              condition will be required for these                      conditions that affect the structural                 considered for design. The factor of
                                              regulations.                                              performance of the airplane (e.g., system             safety is defined in figure 1.


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                                              34026              Federal Register / Vol. 83, No. 139 / Thursday, July 19, 2018 / Rules and Regulations




                                                (ii) For residual strength                               (2) For the continuation of the flight.                (C) The limit rolling conditions
                                              substantiation, the airplane must be able                For the airplane, in the system failed                specified in § 23.349 and the limit
                                              to withstand two thirds of the ultimate                  state and considering any appropriate                 unsymmetrical conditions specified in
                                              loads defined in subparagraph (f)(1)(i).                 reconfiguration and flight limitations,               §§ 23.347, 23.427, and 23.445.
                                                (iii) For pressurized cabins, these                    the following apply:
                                              loads must be combined with the                            (i) The loads derived from the                         (D) The limit yaw maneuvering
                                              normal operating differential pressure.                  following conditions (or defined by                   conditions specified in §§ 23.351,
                                                (iv) Freedom from aeroelastic                          special condition or equivalent level of              23.441, and 23.445.
                                              instability must be shown up to the                      safety in lieu of the following                          (E) The limit ground loading
                                              speeds defined in § 23.629(f). For failure               conditions) at speeds up to VC/MC, or                 conditions specified in §§ 23.473 and
                                              conditions that result in speeds beyond                  the speed limitation prescribed for the               23.493.
                                              VD/MD, freedom from aeroelastic                          remainder of the flight, must be                         (ii) For static strength substantiation,
                                              instability must be shown to increased                   determined:
                                                                                                                                                             each part of the structure must be able
                                              speeds, so that the margins intended by                    (A) The limit symmetrical
                                              § 23.629(f) are maintained.                              maneuvering conditions specified in                   to withstand the loads in paragraph
                                                (v) Failures of the system that result                 §§ 23.321, 23.331, 23.333, 23.345,                    (f)(2)(i) of this special condition
                                              in forced structural vibrations                          23.421, 23.423, and 23.445.                           multiplied by a factor of safety
                                              (oscillatory failures) must not produce                    (B) The limit gust and turbulence                   depending on the probability of being in
                                              loads that could result in detrimental                   conditions specified in §§ 23.341,                    this failure state. The factor of safety is
                                              deformation of primary structure.                        23.345, 23.425, 23.443, and 23.445.                   defined in figure 2.
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                                                                 Federal Register / Vol. 83, No. 139 / Thursday, July 19, 2018 / Rules and Regulations                                         34027




                                                (iii) For residual strength                            with the normal operating pressure                      (v) Freedom from aeroelastic
                                              substantiation, the airplane must be able                differential.                                         instability must be shown up to a speed
                                              to withstand two thirds of the ultimate                     (iv) If the loads induced by the failure           determined from figure 3. Flutter
                                              loads defined in paragraph (f)(2)(ii) of                 condition have a significant effect on                clearance speeds V′ and V″ may be
                                              this special condition. For pressurized                  fatigue or damage tolerance then their                based on the speed limitation specified
                                              cabins, these loads must be combined                                                                           for the remainder of the flight using the
                                                                                                       effects must be taken into account.
                                                                                                                                                             margins defined by § 23.629.
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                                              34028              Federal Register / Vol. 83, No. 139 / Thursday, July 19, 2018 / Rules and Regulations




                                                 (vi) Freedom from aeroelastic                         capability below the level required by                minimized by suitable flight limitations,
                                              instability must also be shown up to V′                  part 23 or significantly reduce the                   must be signaled to the flightcrew. The
                                              in figure 3 above, for any probable                      reliability of the remaining system. As               probability of not annunciating these
                                              system failure condition combined with                   far as reasonably practicable, the                    failure conditions must be extremely
                                              any damage required or selected for                      flightcrew must be made aware of these                improbable (unannunciated failure). For
                                              investigation by §§ 23.571 through                       failures before flight. Certain elements              example, failure conditions that result
                                              23.574.                                                  of the control system, such as                        in a factor of safety between the airplane
                                                 (3) Consideration of certain failure                  mechanical and hydraulic components,                  strength and the loads of subpart C
                                              conditions may be required by other                      may use special periodic inspections,                 below 1.25, or flutter margins below V″,
                                              sections of 14 CFR part 23 regardless of                 and electronic components may use                     must be signaled to the flightcrew
                                              calculated system reliability. Where                     daily checks, in lieu of detection and                during flight.
                                              analysis shows the probability of these                  indication systems to achieve the
                                              failure conditions to be less than 10¥8                  objective of this requirement. These                     (h) Fatigue and damage tolerance. If
                                              for normal, utility, or acrobatic category               certification maintenance requirements                any system failure would have a
                                              airplanes or less than 10¥9 for                          must be limited to components that are                significant effect on the fatigue or
                                              commuter category airplanes, criteria                    not readily detectable by normal                      damage evaluations required in
                                              other than those specified in this                       detection and indication systems and                  §§ 23.571 through 23.574, then these
                                              paragraph may be used for structural                     where service history shows that                      effects must be taken into account.
                                              substantiation to show continued safe                    inspections will provide an adequate                    Issued in Kansas City, Missouri, on July 10,
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                                              flight and landing.                                      level of safety.                                      2018.
                                                 (g) Failure indications. For system                      (2) The existence of any failure
                                                                                                                                                             Pat Mullen,
                                              failure detection and indication, the                    condition, not extremely improbable,
                                              following apply:                                         during flight that could significantly                Manager, Small Airplane Standard Branch,
                                                                                                                                                             Aircraft Certification Service.
                                                 (1) The system must be checked for                    affect the structural capability of the
                                              failure conditions, not extremely                        airplane and for which the associated                 [FR Doc. 2018–15354 Filed 7–18–18; 8:45 am]
                                              improbable, that degrade the structural                  reduction in airworthiness can be
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Document Created: 2018-07-19 01:34:33
Document Modified: 2018-07-19 01:34:33
CategoryRegulatory Information
CollectionFederal Register
sudoc ClassAE 2.7:
GS 4.107:
AE 2.106:
PublisherOffice of the Federal Register, National Archives and Records Administration
SectionRules and Regulations
ActionAmended final special conditions; request for comments.
DatesThese special conditions are effective July 19, 2018 and are applicable on July 10, 2018.
ContactMike 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.
FR Citation83 FR 34022 
CFR AssociatedAircraft; Aviation Safety and Signs and Symbols

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