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

counties for the 504 Rural Pilot, which 

may not be the same as the rural areas 

identified by the U.S. Department of 

Agriculture.) SBA Regions are defined 

as follows: 

• Region I: Connecticut, Maine, 

Massachusetts, New Hampshire, 

Rhode Island, and Vermont 

• Region II: New York, New Jersey, 

Puerto Rico, and The U.S. Virgin 

Islands 

• Region III: Delaware, Maryland, 

Pennsylvania, Virginia, Washington, 

DC, and West Virginia 

• Region IV: Alabama, Florida, Georgia, 

Kentucky, Mississippi, North 

Carolina, South Carolina, and 

Tennessee 

• Region V: Illinois, Indiana, Michigan, 

Minnesota, Ohio, and Wisconsin 

• Region VI: Arkansas, Louisiana, New 

Mexico, Oklahoma, and Texas 

• Region VII: Iowa, Kansas, Missouri, 

and Nebraska 

• Region VIII: Colorado, Montana, 

North Dakota, South Dakota, Utah, 

and Wyoming 

• Region IX: Arizona, California, Guam, 

Hawaii, and Nevada 

• Region X: Alaska, Idaho, Oregon, and 

Washington. 

In making, closing, servicing, or 

liquidating a 504 Rural Pilot loan, CDCs 

must follow all other Loan Program 

Requirements under the 504 Loan 

Program, except that 504 Rural Pilot 

loans cannot be made using the CDC’s 

delegated authority (i.e., PCLP or ALP 

authority). Although, as described 

above, CDCs will not be required ‘‘to 

demonstrate’’ that they can adequately 

fulfill their 504 program responsibilities 

for each 504 Rural Pilot loan before 

making the loan, CDCs will still be 

expected to fulfill all such program 

responsibilities with respect to these 

loans. 

Unlike a Multi-State CDC, a CDC 

making a loan under this pilot will not 

be required to establish a separate loan 

committee to cover the State in which 

the rural 504 Project is located. In 

addition, the CDC must advise the local 

District Counsel where the 504 Project 

is located which Designated Attorney, 

or other attorney, will be closing the 

loan. (The attorney must be licensed in 

the State where the loan is being made.) 

CDCs should note that the CDC may not 

close the loan as an expedited loan 

unless the attorney is a Designated 

Attorney licensed to practice in the 

State where the 504 Project is located. 

The CDC is responsible for notifying the 

SLPC that a 504 loan application is 

being submitted under the 504 Rural 

Pilot. 

SBA’s waiver of the above 

requirements is authorized by 13 CFR 

120.3 of its regulations, which provides 

that the SBA Administrator may 

suspend, modify or waive rules for a 

limited period of time to test new 

programs or ideas. The 504 Rural Pilot 

will be available for a two year period 

beginning today. 

SBA will limit the number of loans 

made under the 504 Rural Pilot to not 

more than ten percent of the total 

number of 504 loans guaranteed by SBA 

in any fiscal year. While SBA does not 

expect the number of 504 Rural Pilot 

loans to reach that limit, SBA will 

provide public notice of the need to 

suspend lending under the 504 Rural 

Pilot for the remainder of the fiscal year 

if SBA determines that the number of 

pilot loans is approaching the limit. 

SBA will be using the following 

criteria to evaluate the 504 Rural Pilot 

to determine how well it is achieving its 

objectives and other aspects of 

performance: (1) The measurable 

objectives to be achieved through the 

504 Rural Pilot, including the number of 

small business concerns served, and the 

delinquency and default rates on the 

504 Rural Pilot loans compared to 

regular 504 loans; (2) the number of 

CDCs that participate in the 504 Rural 

Pilot and their performance in making 

and servicing 504 Rural Pilot loans; and 

(3) the costs and standards of 

performance which, in order to be 

acceptable, must not impact the overall 

subsidy rate for the 504 Loan Program. 

For data collections to evaluate the 

effectiveness of this pilot, SBA will use 

ETran, SBA’s electronic system for loan 

submission and servicing. 

Authority: 13 CFR 120.3. 

Dated: July 6, 2018. 

Linda E. McMahon, 

Administrator. 

[FR Doc. 2018–15312 Filed 7–18–18; 8:45 am] 

BILLING CODE 8025–01–P 

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. 

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: 

b Federal eRegulations Portal: Go to 

http://www.regulations.gov and follow 

the online instructions for sending your 

comments electronically. 

b 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. 

b Hand Delivery of Courier: Deliver 

comments to the ‘‘Mail’’ address 

between 9 a.m. and 5 p.m., Monday 

through Friday, except Federal holidays. 

b 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 


sradovich on DSK3GMQ082PROD with RULES
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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 loadrelief 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 FAAapproved Minimum Equipment List 

(MEL) for the specific aircraft type. 

Without an FAA-approved MEL, 

operators must obtain a special flight 

permit in accordance with §§ 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 § 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 

§ 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 § 11.38, and they become part of 

the type-certification basis under 

§ 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 § 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 


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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 


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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 §§ 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 §§ 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 § 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 

§ 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 

§ 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. 


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

(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 § 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 

§ 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 

§§ 23.321, 23.331, 23.333, 23.345, 

23.421, 23.423, and 23.445. 

(B) The limit gust and turbulence 

conditions specified in §§ 23.341, 

23.345, 23.425, 23.443, and 23.445. 

(C) The limit rolling conditions 

specified in § 23.349 and the limit 

unsymmetrical conditions specified in 

§§ 23.347, 23.427, and 23.445. 

(D) The limit yaw maneuvering 

conditions specified in §§ 23.351, 

23.441, and 23.445. 

(E) The limit ground loading 

conditions specified in §§ 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. 


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Federal Register / Vol. 83, No. 139 / Thursday, July 19, 2018 / Rules and Regulations 34027 

(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 § 23.629. 


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34028 Federal Register / Vol. 83, No. 139 / Thursday, July 19, 2018 / Rules and Regulations 

(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 §§ 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 

§§ 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 


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