Federal Register / Vol. 76, No. 231 / Thursday, December 1, 2011 / Rules and Regulations 74655 

§ 25.253 High-speed characteristics. 

(a) * * * 

(4) Adequate roll capability to assure 

a prompt recovery from a lateral upset 

condition must be available at any 

speed up to VDF/MDF. 

(5) With the airplane trimmed at VMO/ 

MMO, extension of the speedbrakes over 

the available range of movements of the 

pilot’s control, at all speeds above VMO/ 

MMO, but not so high that VDF/MDF

would be exceeded during the 

maneuver, must not result in: 

(i) An excessive positive load factor 

when the pilot does not take action to 

counteract the effects of extension; 

(ii) Buffeting that would impair the 

pilot’s ability to read the instruments or 

control the airplane for recovery; or 

(iii) A nose down pitching moment, 

unless it is small. 

(b) Maximum speed for stability 

characteristics, VFC/MFC. VFC/MFC is the 

maximum speed at which the 

requirements of §§ 25.143(g), 25.147(f), 

25.175(b)(1), 25.177(a) through (c), and 

25.181 must be met with flaps and 

landing gear retracted. Except as noted 

in § 25.253(c), VFC/MFC may not be less 

than a speed midway between VMO/ 

MMO and VDF/MDF, except that, for 

altitudes where Mach number is the 

limiting factor, MFC need not exceed the 

Mach number at which effective speed 

warning occurs. 

(c) Maximum speed for stability 

characteristics in icing conditions. The 

maximum speed for stability 

characteristics with the ice accretions 

defined in appendix C, at which the 

requirements of §§ 25.143(g), 25.147(f), 

25.175(b)(1), 25.177(a) through (c), and 

25.181 must be met, is the lower of: 

* * * * * 

Issued in Washington, DC, on November 1, 

2011. 

J. Randolph Babbitt, 

Administrator. 

[FR Doc. 2011–30954 Filed 11–30–11; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Parts 27 and 29 

[Docket No.: FAA–2009–0660; Amdt. Nos. 

27–47, 29–54] 

RIN 2120–AJ52 

Damage Tolerance and Fatigue 

Evaluation of Composite Rotorcraft 

Structures 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final rule. 

SUMMARY: This rule revises 

airworthiness standards for type 

certification requirements of normal and 

transport category rotorcraft. The 

amendment requires evaluation of 

fatigue and residual static strength of 

composite rotorcraft structures using a 

damage tolerance evaluation, or a 

fatigue evaluation if the applicant 

establishes that a damage tolerance 

evaluation is impractical. The 

amendment addresses advances in 

composite structures technology and 

provides internationally harmonized 

standards. 

DATES: Effective January 30, 2012. 

ADDRESSES: For information on where to 

obtain copies of rulemaking documents 

and other information related to this 

final rule, see ‘‘How To Obtain 

Additional Information’’ at the end of 

the SUPPLEMENTARY INFORMATION section 

of this document. 

FOR FURTHER INFORMATION CONTACT: For 

technical questions concerning this 

action, contact Sharon Y. Miles, 

Regulations and Policy Group, 

Rotorcraft Directorate, ASW–111, 

Federal Aviation Administration, 2601 

Meacham Boulevard Fort Worth, Texas 

76137–0111; telephone (817) 222–5122; 

facsimile (817) 222–5961; email 

sharon.y.miles@faa.gov. For legal 

questions concerning this action, 

contact Steve C. Harold, Directorate 

Counsel, ASW–7G1, Federal Aviation 

Administration, 2601 Meacham 

Boulevard Fort Worth, Texas 76137– 

0007, telephone (817) 222–5099; 

facsimile (817) 222–5945, email 

steve.c.harold@faa.gov. 

SUPPLEMENTARY INFORMATION: 

Authority for This Rulemaking 

The FAA’s authority to issue rules on 

aviation safety is found in Title 49 of the 

United States Code. Subtitle I, section 

106, describes the authority of the FAA 

Administrator. Subtitle VII, Aviation 

Programs, describes in more detail the 

scope of the agency’s authority. 

This rulemaking is promulgated 

under the authority described in subtitle 

VII, part A, subpart III, section 44701, 

‘‘General Requirements,’’ Section 44702, 

‘‘Issuance of Certificates,’’ and Section 

44704, ‘‘Type Certificates, Production 

Certificates, and Airworthiness 

Certificates.’’ Under Section 44701, the 

FAA is charged with prescribing 

regulations and minimum standards for 

practices, methods, and procedures the 

Administrator finds necessary for safety 

in air commerce. Under Section 44702, 

the Administrator may issue various 

certificates including type certificates, 

production certificates, air agency 

certificates, and airworthiness 

certificates. Under Section 44704, the 

Administrator must issue type 

certificates for aircraft, aircraft engines, 

propellers, and specified appliances 

when the Administrator finds the 

product is properly designed and 

manufactured, performs properly, and 

meets the regulations and minimum 

standards prescribed under section 

44701(a). This regulation is within the 

scope of these authorities because it will 

promote safety of composite structures 

by updating the existing minimum 

prescribed standards, used during the 

type certification process, to address 

advances in composite structural fatigue 

substantiation technology. It will also 

harmonize this standard with 

international standards for evaluating 

the fatigue strength of normal and 

transport category rotorcraft composite 

primary structural elements. 

I. Overview of Final Rule 

Composite structures present unique 

material behaviors and react differently 

from metallic structures to damage and 

loading conditions. This rule addresses 

the unique characteristics of composite 

materials and requires applicants to 

evaluate these materials in a different 

manner from traditional metallic 

materials. This rulemaking addresses 

the type certification requirements for 

substantiating and certifying composite 

rotorcraft structures, including different 

aspects of the evaluation for the most 

critical issues for each class of materials. 

This rule changes the certification 

standards in areas of frequent nonstandardization and misinterpretation 

by applicants for certification of 

rotorcraft composite structures. This 

rule is intended to require damage 

tolerance and fatigue evaluation of 

composite structures in order to prevent 

reduction of structural strength of 

rotorcraft. In composite structures, low 

cycle fatigue often yields minimal 

damage growth, whereas accidental 

damage from impact can immediately 

reduce residual structural strength. This 

is different in metals, where any critical 

damage to the structure is sensitive to 

cyclic fatigue loads. 

These rule changes also address 

material and process variability and 

environmental effects. A strength 

requirement for ultimate loads will be 

applied when maximum acceptable 

manufacturing defects and service 

damage are present. However, these rule 

changes provide an exception to the 

requirement for a damage tolerance 

evaluation if the applicant can establish 

that the damage tolerance evaluation is 

impractical within the limits of 

geometry, inspectability, and good 

design practice. In that instance, the 


emcdonald on DSK5VPTVN1PROD with RULES
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applicant may be allowed to perform a 

fatigue evaluation for some rotorcraft 

structures and damage scenarios based 

on supplemental procedures, such as 

establishing a retirement time. Under 

this exception, an applicant could 

demonstrate that certain damage will 

not grow or does not grow beyond a 

certain threshold or size, and that the 

damaged structure could still carry 

ultimate loads. In this case, an 

inspection may not be necessary and the 

structure could be assigned a retirement 

life instead of a required inspection 

program. Further, this rule will require 

an applicant to conduct a threat 

assessment, which is associated with 

the service history of composite 

structures. 

The rule requires that applicants 

consider varying types of damage, 

loading conditions, threat assessments, 

manufacturing defects, and the residual 

strength associated with composite 

structures. In developing these 

requirements, the FAA recognized that 

it may be impractical within the limits 

of geometry, inspectability, or good 

design practice to evaluate all the 

composite structures of a rotorcraft 

using a damage tolerance evaluation. 

Therefore, the rule allows for a fatigue 

evaluation of particular rotorcraft 

composite structures under §§ 27.573(e) 

and 29.573(e), where appropriate, if the 

applicant can establish that performing 

a damage tolerance evaluation is 

impractical within the limits of 

geometry, inspectability, and good 

design practice for those principal 

structural elements (PSEs). As part of 

the approval process for fatigue 

evaluation of a particular rotorcraft 

composite structure, the applicant will 

be required to identify the PSEs and the 

types of damage considered, establish 

supplemental procedures to minimize 

the risk of catastrophic failure 

associated with those types of damage, 

and include procedures in the 

Airworthiness Limitation section of the 

Instructions for Continued 

Airworthiness. These requirements 

minimize the risk of catastrophic failure 

of composite structures used on 

rotorcraft certificated in accordance 

with part 27 and part 29 standards. 

A. Key Provisions in the New Rule 

Some of the requirements for 

evaluating composite structures came 

from the current § 29.571 standards. 

These requirements in the evaluation 

process include certain steps, such as 

identification of the PSEs, the in-flight 

measurements of loads, and the use of 

loading spectra, as severe as those 

expected in-service. These rule changes 

add more detailed steps and do not refer 

to the current flaw tolerant safe-life and 

fail-safe evaluations because there are 

more suitable ways of describing each 

approach under damage tolerance. 

Further, this rule does not refer to the 

traditional safe-life method because 

composites have sensitivities to defects 

and damage that must be considered in 

design and certification testing that 

makes the traditional safe-life method 

inappropriate. 

These rule changes revise the 

standards for determining inspection 

intervals and retirement times based on 

results of damage tolerance and fatigue 

evaluation. Currently, the minimum 

residual structural strength requirement 

for any damage or defect that can be 

found by inspection is tied to limit 

loads (maximum loads to be expected in 

service). These rule changes link the 

required residual structural strength to 

the probability of a given damage type, 

inspection interval, and damage 

detectability. This link is necessary for 

at least two reasons. First, one of the 

more critical threats—impact damage— 

could immediately lower residual 

structural strength to well below 

ultimate loads (limit loads multiplied by 

prescribed factors of safety) if it occurs. 

These requirements will help ensure 

that, as the residual structural strength 

is lowered, the earlier damage will be 

detected and repaired. Inspections will 

be required that will be frequent and 

comprehensive enough to reveal any 

damage or defect growth to minimize 

the time that the rotorcraft might be 

operated at less than an ultimate load 

capability. Second, the requirements 

address rare damage (such as a highenergy, blunt impact) that is not 

detectable with the currently prescribed 

inspection schemes for aircraft in 

operational service. Although such 

damage may have a low probability of 

occurring, the rules require that 

sufficient residual structural strength 

exists to compensate for such damage. 

These rule changes require that all 

PSEs, the failure of which could result 

in catastrophic failure of the rotorcraft, 

meet ultimate load residual structural 

strength requirements or require a 

retirement time if there could be any 

damage that may not be found by a 

maintenance inspection. Under this 

rule, an applicant will establish a 

retirement time to address the damage 

that may not be found by inspection or 

to eliminate the burden of the repeated 

inspection by the rotorcraft owners. For 

damage detectable by inspection, the 

rule establishes a limit load requirement 

to repair and restore the structure to its 

ultimate strength capability. 

These rule changes add all PSE 

assessments for damage threats, residual 

strength, and fatigue characteristics to 

the list of requirements for inspection 

intervals or require replacement times 

as stated in §§ 27.573(d)(2) and 

29.573(d)(2). The fatigue evaluation will 

include the PSEs of the airframe, main 

and tail rotor drive systems, main and 

tail rotor blades and hubs, rotor 

controls, fixed and movable control 

surfaces, engine and transmission 

mountings, landing gear, and other 

parts. In addition, performing damage 

tolerance evaluations of the strength of 

composite detail design points and 

fabrication techniques is considered 

critical by the FAA to avoid catastrophic 

failure due to static or fatigue loads. 

The rule requires consideration of the 

effects of fatigue damage on stiffness, 

dynamic behavior, loads, and functional 

performance of composite structures. 

These characteristics are not considered 

to be a serious threat to residual 

structural strength. Currently, such 

requirements are limited to fail-safe 

evaluations. 

The FAA recognizes there may be 

limited cases in which a damage 

tolerance evaluation may be impractical. 

In these rare cases, the applicant is 

required to identify the nature of the 

evaluation and provide a justification to 

the FAA for the impracticality 

determination. The justification must 

support the specific types of damage to 

the PSE to qualify for a fatigue 

evaluation. Finally, the rule requires the 

applicant to establish replacement 

times, structural inspection intervals, 

and related structural inspection 

procedures to minimize the risk of 

catastrophic failure because of PSE 

damage. The required replacement 

times, inspection intervals, and 

structural inspections will be included 

in the Instructions for Continued 

Airworthiness as required by §§ 27.1529 

and 29.1529. 

Additionally, the FAA recognizes that 

rare types of damage, such as highenergy, blunt impacts may not be 

uncovered as part of a base field 

inspection during scheduled 

maintenance inspection intervals. 

Therefore, this rule requires that the 

applicant substantiate sufficient 

residual structural strength to maintain 

an adequate level of safety in the event 

of an occurrence of rare damage. 

Supplemental procedures may be 

required to adequately address rare 

impact damage. 

B. Airworthiness Limitations Section 

(Appendix A to Parts 27 and 29) 

These sections require the mandatory 

replacement times, structural inspection 

intervals, and related structural 

inspection procedures produced under 


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Federal Register / Vol. 76, No. 231 / Thursday, December 1, 2011 / Rules and Regulations 74657 

1Published in the Federal Register, April 5, 2000 

(65 FR 17936). 

the requirements of §§ 27.571 and 

29.571, the new §§ 27.573 and 29.573, 

and any other similar requirement for 

type certification be included in the 

Airworthiness Limitations Section of 

the Instructions for Continued 

Airworthiness. 

C. Benefit-Cost Comparison 

This final rule adopts as regulatory 

requirements past FAA and industry 

practice regarding the use of composites 

on rotorcraft, including special 

conditions and advisory circulars. 

Although we anticipate both cost 

savings and improved safety as a 

consequence of the requirement for 

testing, inspection, and replacement 

schedules, we are unable to quantify 

these benefits. Nevertheless, based on 

industry-provided data, we believe that 

this final rule will yield benefits 

exceeding the estimated costs. 

II. Background and Statement of the 

Issues 

The evolution of composite 

technology used in rotorcraft structures 

is advancing rapidly. These rapid 

changes, along with the increased use of 

composites in rotorcraft structures, 

issues discovered during certification of 

composite structures, and service 

experiences of composite rotorcraft 

structures over the last 25 years, have 

caused us to reconsider the current 

regulations and guidance materials for 

damage tolerance and fatigue evaluation 

and to address the state of technology in 

composite structures. The current 

certification process is based on a broad 

interpretation of metallic fatigue 

substantiation and the design and 

construction airworthiness standards. 

However, composite and metal 

structures are different. Composites are 

complex materials that have unique 

advantages in fatigue strength, weight, 

and tolerance to damage. The 

methodologies for evaluating metallic 

structures are not necessarily suitable 

for composite structures. Because 

composite structures differ from 

metallic structures, the current 

regulations, §§ 27.571 and 29.571, do 

not adequately provide the fatigue 

certification requirements for composite 

rotorcraft structures. 

This may lead to inconsistent 

interpretations from one rotorcraft 

certification project to another, resulting 

in different burdens on applicants to 

substantiate their composite rotorcraft 

structures. It has also caused confusion 

for some certification applicants. These 

applicants state there is no clear, 

complete guidance for certification of 

composite rotorcraft structures. 

To address these concerns, the FAA 

tasked the Aviation Rulemaking 

Advisory Committee (ARAC) 1 through 

its Composite Rotorcraft Structure 

working group to provide advice and 

recommendations as follows: 

• Recommend revisions to FAA 

Regulations/Joint Aviation Regulations 

(JAR) parts 27 and 29 for composite 

structures that are harmonized. 

• Evaluate and recommend, as 

appropriate, regulations, advisory 

material, and related guidance to 

achieve the goal of improved tolerance 

to flaws and defects in composite 

structure with methodology and 

procedures that are practical and 

appropriate to rotorcraft. 

This rule is based on ARAC’s 

recommendations to the FAA. The 

recommendations have been placed in 

the docket for this rulemaking. 

A. Related Activity 

At the same time ARAC was tasked 

with providing advice and 

recommendations for composite 

rotorcraft structures, they were also 

tasked with providing advice and 

recommendations for metallic rotorcraft 

structures. However, because of the 

unique characteristics and structural 

capabilities of composite structures, the 

FAA established a separate rule for the 

damage tolerance and fatigue 

evaluations of rotorcraft composite 

structures. In response to the ARAC 

recommendations for improved 

standards for metallic structures, the 

FAA has developed a separate rule 

entitled ‘‘Fatigue Tolerance Evaluation 

of Metallic Structures.’’ 

B. Summary of the NPRM 

The FAA published the NPRM for this 

composite structures rule in the Federal 

Register on January 6, 2010 (75 FR 793). 

The comment period for the NPRM 

closed on April 6, 2010. However, in 

response to a European Aviation Safety 

Agency (EASA) request, the FAA 

subsequently reopened the comment 

period to July 16, 2010 (published in the 

Federal Register on May 5, 2010, 75 FR 

24502). The FAA received 12 comments 

to the docket on the NPRM. 

Commenters included two 

manufacturers, a government agency, 

and an engineering company. 

C. General Overview of Comments 

The FAA received various comments 

from four commenters—Adhesion 

Associates, Eurocopter France, Sikorsky 

Aircraft, and Transport Canada. All of 

the commenters generally supported the 

proposed changes; however, some 

suggested changes and clarifications to 

the rule, as discussed more fully in the 

next section of this document. The FAA 

received comments on the following 

general areas of the proposal. 

• Definition of the term 

‘‘composites.’’ 

• Reconciling differences related to 

compliance methodology approval 

authority between § 29.571 (metallics) 

and § 29.573 (composites). 

• Reevaluating the economic impact 

of the rule. 

• The manner of the application of 

‘‘safe life evaluation’’ as established in 

the Advisory Circular (AC) 27–1B or 29– 

2C, Miscellaneous Guidance-08 and its 

relationship to these new rule changes. 

• Rewording To clarify that the 

application of the changes to the 

Appendix A required by this rule 

applies to structures only. 

• Requesting further rulemaking to 

address the potential for subsequent 

service adhesion failures and the effect 

of micro-voiding on bonding strength. 

III. Discussion of Public Comments and 

Final Rule 

Definition of the Term ‘‘Composites’’ 

Sikorsky Aircraft recommended a 

further definition of ‘‘composites,’’ 

beyond that contained in Advisory 

Circular (AC) 21–26, because it believes 

this is a necessary part of compliance 

for determining, for a given structure, 

whether to use § 29.571 or § 29.573. 

The term ‘‘composites’’ is widely 

understood throughout the aviation 

industry to be different materials that 

are bonded or composed to create a 

structural component material. It has 

been defined in AC 21–26 as a material 

containing two or more distinct 

materials (fillers, reinforcing materials, 

and compatible plastic resin) designed 

to exhibit specific performance 

properties. A further definition is 

unnecessary. This definition is 

consistent with the FAA intent when it 

uses the term ‘‘composites’’ in both 

§§ 27.573 and 29.573. Therefore, the 

FAA is adopting the rule as proposed. 

Reconciling Difference Between This 

Rule and the § 29.571 (Metallics) Rule, 

in the Approval Authority of 

Compliance Methodology and 

Methodology Results 

Sikorsky Aircraft identified the 

difference between §§ 27.573 and 

29.573, which refer to FAA approval, 

and § 29.571 (metallics), which refers to 

the Administrator’s approval. It states 

that the language used in the approval 

process should be similar for § 29.571 

(metallics) and § 29.573 (composites). 


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The FAA agrees that this could cause 

confusion. The wording is changed in 

this rule to make it consistent with the 

wording in § 29.571 (metallics). The 

intent of §§ 29.571, 27.573, and 29.573 

is that the approval of the methodology 

for the evaluation remains with the FAA 

(Administrator). 

Re-Wording To Clarify That Changes to 

the Appendix Apply to Structures Only 

Eurocopter France recommended 

rewording the proposed amended 

language to part 29, Appendix A, from 

‘‘required for type certification’’ to 

‘‘required for type certification of 

structures’’ to eliminate addressing nonstructural elements. It further 

recommended implementation of the 

policy statement ASW–100–09–003 

(Subj: Policy Statement Concerning Life 

Limits and Instructions for Continued 

Airworthiness for Rotorcraft), and for 

the FAA to address mandatory 

Instruction for Continued Airworthiness 

(ICA) for non-structural elements 

through a new rulemaking task, in 

coordination with the European 

Aviation Safety Agency (EASA). 

The intent of the policy statement and 

this rule is to require that any life limit 

or required inspection interval for type 

certification is included in the 

Airworthiness Limitations Section of 

the Instructions for Continued 

Airworthiness. This is the same wording 

used in the current 14 CFR part 23, 

Appendix G23.4. This is also consistent 

with the intent of the airworthiness 

limitations section of the Appendix to 

highlight certification limitations 

regardless of whether they are structural 

or non-structural. 

The FAA does not anticipate further 

rulemaking to implement the policy 

statement because it does not 

differentiate between structural or nonstructural elements. Therefore, the FAA 

is adopting the provision as proposed. 

Cost Estimates to the Economic Impact 

of the Rules 

Sikorsky Aircraft believes the cost 

estimates for this rule should be 

calculated based on 12,000 hours per 

certification project. 

Based on this commenter’s cost 

estimate of 12,000 hours, at $86 per 

hour, the total nominal dollar estimate 

will be $1,032,000 ($567,000 in present 

value). The original hours provided in 

the ARAC recommendation were 8290 

hours at $86 per hour. Taking into 

account the intervening 27 years, the 

present value difference between these 

estimates is $175,000. Based on this 

information, we estimate the nominal 

total compliance costs of this final rule 

to be between our original estimate of 

$713,000 and the commenter based 

estimate of $1,032,000. 

Acceptability of ‘‘Traditional Safe Life’’ 

Approach in the Context of Flaw 

Tolerance Requirements, and the 

Application of ACs 27–1B and 29–2C, 

Miscellaneous Guidance (MG) 8, 

Paragraph g(6)(iii)(C)) (Safe Life 

Evaluation) 

Transport Canada requested 

confirmation of the FAA’s position 

concerning the acceptability of the 

‘‘traditional safe life’’ approach for flaw 

tolerance requirements, and asks that 

the FAA consider amending MG 8 to 

clarify that the ‘‘traditional safe life’’ is 

not appropriate for composites, if that is 

the case. Transport Canada further 

suggested that the FAA amend §§ 27.573 

and 29.573 to include clarification to 

this effect, since the flaw tolerance 

concept is applicable to both static and 

fatigue strength, and to consider 

incorporating into the new rule 

requirements for environmental 

conditions, maximum manufacturing 

defects and service damages, and the 

effect of repeat loading (after fatigue). 

Intentionally, the proposed rule did 

not address flaw tolerance or safe life. 

This was only addressed in MG 8 based 

on the requirements of the current 

§ 29.571. The requirement is for 

evaluating damage tolerance as 

addressed in paragraphs (d) of §§ 27.573 

and 29.573. If impractical, paragraph (e) 

will require a fatigue evaluation. The 

proposed rule did not specifically 

address static requirements because 

they are covered in the current 

requirements of §§ 27.305 and 29.305. 

The draft AC for this rule is similar in 

format to the current MG 8, but has been 

updated to address the damage 

tolerance fatigue requirements of 

composite structures. All of these 

damage tolerance concerns must be 

considered under the requirements of 

paragraphs (d) and (e) of this rule. The 

miscellaneous guidance referred to in 

the comment is the applicable guidance 

for compliance until §§ 27.573 and 

29.573 become effective; it is not the 

guidance for this new rule. Therefore, 

the FAA is adopting the rule as 

proposed. 

Request for Further Rulemaking To 

Address Subsequent Service Adhesion 

Failures 

Adhesion Associates Proprietary, 

Limited, recommended that the FAA 

address the in-service degradation of the 

chemical bonds in a new regulation 

(§ 2x.605 for parts 27 and 29); and that 

information on the significance, causes, 

and management procedures for microvoids be incorporated into AC 20–107B. 

The recommendation for a new 

regulation is beyond the scope of this 

rulemaking. However, it will be 

considered in future rulemaking. 

Likewise, the recommended changes to 

AC 20–107B will be considered in 

future AC revisions. 

Differences Between the NPRM and the 

Final Rule 

Sections §§ 27.573(b) and 29.573(b) 

are reworded to be consistent with the 

wording in § 29.571 for metallic 

structures. 

IV. Regulatory Notices and Analyses 

A. Regulatory Evaluation 

Changes to Federal regulations must 

undergo several economic analyses. 

First, Executive Order 12866 and 

Executive Order 13563 direct that each 

Federal agency shall propose or adopt a 

regulation only upon a reasoned 

determination that the benefits of the 

intended regulation justify its costs. 

Second, the Regulatory Flexibility Act 

of 1980 (Pub. L. 96–354) requires 

agencies to analyze the economic 

impact of regulatory changes on small 

entities. Third, the Trade Agreements 

Act (Pub. L. 96–39) prohibits agencies 

from setting standards that create 

unnecessary obstacles to the foreign 

commerce of the United States. In 

developing U.S. standards, this Trade 

Act requires agencies to consider 

international standards and, where 

appropriate, that they be the basis of 

U.S. standards. Fourth, the Unfunded 

Mandates Reform Act of 1995 (Pub. L. 

104–4) requires agencies to prepare a 

written assessment of the costs, benefits, 

and other effects of proposed or final 

rules that include a Federal mandate 

likely to result in the expenditure by 

State, local, or tribal governments, in the 

aggregate, or by the private sector, of 

$100 million or more annually (adjusted 

for inflation with base year of 1995). 

This portion of the preamble 

summarizes the FAA’s analysis of the 

economic impacts of this proposed rule. 

We suggest readers seeking greater 

detail read the full regulatory 

evaluation, a copy of which we have 

placed in the docket for this rulemaking. 

In conducting these analyses, FAA 

has determined that this final rule: 

(1) Has benefits that justify its costs; 

(2) Is not an economically ‘‘significant 

regulatory action’’ as defined in section 

3(f) of Executive Order 12866; 

(3) Is ‘‘non-significant’’ as defined in 

DOT’s Regulatory Policies and 

Procedures; 

(4) Would not have a significant 

economic impact on a substantial 

number of small entities; 


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Federal Register / Vol. 76, No. 231 / Thursday, December 1, 2011 / Rules and Regulations 74659 

(5) Would not have a significant effect 

on international trade; and 

(6) Would not impose an unfunded 

mandate on state, local, or tribal 

governments, or on the private sector by 

exceeding the monetary threshold 

identified. 

These analyses are summarized below. 

Total Benefits and Costs of This 

Rulemaking 

The estimated total cost of this final 

rule is between $713,000 ($392,000 in 

present value at 7%) and $1,032,000 

($567,000 in present value at 7%). The 

final rule systematizes past FAA and 

industry practice regarding the use of 

composites on rotorcraft, including 

special conditions and advisory 

circulars. Although we anticipate both 

cost savings and improved safety as a 

result of required inspection and 

replacement schedules, we are unable to 

quantify these benefits. Nevertheless, 

we believe that the qualitatively 

estimated benefits are real and 

significant and exceed the final rule’s 

costs. 

Who is Potentially Affected by this 

Rulemaking? 

• Manufacturers of U.S.-registered 

part 27 and part 29 rotorcraft. 

Our Cost Assumptions and Sources of 

Information. 

• Discount rate—7%. 

• Period of analysis of 27 years equals 

the 27 years of National Transportation 

Safety Board accident history. During 

this period, manufacturers will seek 

new certifications for 10.5 part 27 

rotorcraft and six part 29 rotorcraft. 

Benefits of This Rule 

The final rule adopts as regulatory 

requirements past FAA and industry 

practice regarding the use of composites 

on rotorcraft, including special 

conditions and advisory circulars. 

Although we anticipate both cost 

savings and improved safety as a result 

of required inspection and replacement 

schedules, we are unable to quantify 

these benefits. Nevertheless, we believe 

that the qualitatively estimated benefits 

are real and significant and exceed the 

final rule’s costs. We did not receive any 

comments regarding our conclusion that 

the benefits exceed the costs. 

Cost of This Rule 

Based upon the ARAC 

recommendation, we estimated the costs 

of this final rule to be about $713,000 

($392,000 in present value) over the 27- 

year analysis period. Manufacturers of 

14 CFR part 27 rotorcraft would incur 

costs of about $101,000 ($55,000 in 

present value) and manufacturers of 14 

CFR part 29 helicopters would incur 

costs of about $612,000 ($337,000 in 

present value). 

One commenter provided a cost 

estimate of 12,000 hours as the cost of 

the rule. Converting the hours to dollars 

results in a nominal cost of $1,032,000 

($567,000 in present value); therefore, 

we estimate that the nominal cost of the 

final rule will have a range of $713,000 

to $1,032,000. 

B. Regulatory Flexibility Determination 

The Regulatory Flexibility Act of 1980 

(RFA) establishes ‘‘as a principle of 

regulatory issuance that agencies shall 

endeavor, consistent with the objective 

of the rule and of applicable statutes, to 

fit regulatory and informational 

requirements to the scale of the 

business, organizations, and 

governmental jurisdictions subject to 

regulation.’’ To achieve that principle, 

the RFA requires agencies to solicit and 

consider flexible regulatory proposals 

and to explain the rationale for their 

actions. The RFA covers a wide-range of 

small entities, including small 

businesses, not-for-profit organizations 

and small governmental jurisdictions. 

Agencies must perform a review to 

determine whether a proposed or final 

rule will have a significant economic 

impact on a substantial number of small 

entities. If the agency determines that it 

will, the agency must prepare a 

regulatory flexibility analysis as 

described in the RFA. 

However, if an agency determines that 

a proposed or final rule is not expected 

to have a significant economic impact 

on a substantial number of small 

entities, section 605(b) of the RFA 

provides that the head of the agency 

may so certify and a regulatory 

flexibility analysis is not required. The 

certification must include a statement 

providing the factual basis for this 

determination, and the reasoning should 

be clear. 

This final rule directly affects 

rotorcraft manufacturers. 

Part 27 Helicopter Manufacturers 

Size Standards 

Size standards for small entities are 

published by the Small Business 

Administration (SBA) on their Web site 

at http://www.sba.gov/size. The size 

standards used herein are from ‘‘SBA 

U.S. Small Business Administration, 

Table of Small Business Size Standards, 

Matched to North American Industry 

Classification System Codes.’’ The table 

is effective August 22, 2008 and uses the 

NAICS 2007 NAICS codes. 

Helicopter manufacturers are listed in 

the referenced table under Sector 31– 

33—Manufacturing; Subsector 336— 

Transportation Equipment 

Manufacturing; NAICS Code 336411— 

Aircraft Manufacturing. The small entity 

size standard is 1,500 employees. 

Table R1 shows there are six U.S. part 

27 helicopter manufacturers that 

produce composite helicopters. MD 

Helicopters, with 400 employees, is the 

only part 27 helicopter manufacturer to 

qualify as a small entity. It is estimated 

that MD Helicopters has annual 

revenues of $175,000,000. The cost of 

this rule for one part 27 helicopter 

certification for a part 27 manufacturer 

is estimated to be $9,600. This is less 

than 0.01 percent of MD Helicopters 

annual revenue. We do not believe that 

is a significant cost. Therefore, it is not 

anticipated that this final rule would 

have a significant economic impact on 

a substantial number of part 27 

helicopter manufacturers. 


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Part 29 Helicopter Manufacturers 

Size Standards 

Size standards for part 29 

manufacturers are the same as the size 

standards for part 27 manufacturers. 

Table R2 shows there are four U.S. 

part 29 helicopter manufacturers 

currently producing helicopters. None 

of these manufacturers qualify as a 

small entity. Therefore, this final rule 

will not have a significant economic 

impact on a substantial number of part 

29 helicopter manufacturers. 


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Federal Register / Vol. 76, No. 231 / Thursday, December 1, 2011 / Rules and Regulations 74661 

For the initial regulatory flexibility 

analysis we made the same 

determination that this rule would not 

have a significant economic impact on 

a substantial number of small entities 

and we did not receive any comments 

regarding our analysis or determination 

regarding small entities. Consequently, 

the FAA Administrator certifies that this 

final rule will not have a significant 

economic impact on a substantial 

number of part 27 or part 29 rotorcraft 

manufacturers. 

C. International Trade Impact 

Assessment 

The Trade Agreements Act of 1979 

(Pub. L. 96–39), as amended by the 

Uruguay Round Agreements Act (Pub. 

L. 103–465), prohibits Federal agencies 

from establishing standards or engaging 

in related activities that create 

unnecessary obstacles to the foreign 

commerce of the United States. 

Pursuant to these Acts, establishing 

standards is not considered an 

unnecessary obstacle to the foreign 

commerce of the United States, so long 

as the standard has a legitimate 

domestic objective, such as the 

protection of safety, and does not 

operate in a manner that excludes 

imports that meet this objective. The 

statute also requires consideration of 

international standards and, where 

appropriate, that they be the basis for 

U.S. standards. 

The FAA has assessed the potential 

effect of this proposed rule and 

determined that it would impose the 

same costs on domestic and 

international entities and thus has a 

neutral trade impact. 

D. Unfunded Mandates Assessment 

Title II of the Unfunded Mandates 

Reform Act of 1995 (Pub. L. 104–4) 

requires each Federal agency to prepare 

a written statement assessing the effects 

of any Federal mandate in a proposed or 

final agency rule that may result in an 

expenditure of $100 million or more 

(adjusted annually for inflation) in any 

1 year by State, local, and tribal 

governments, in the aggregate, or by the 

private sector; such a mandate is 

deemed to be a ‘‘significant regulatory 

action.’’ The FAA currently uses an 

inflation-adjusted value of $140.8 

million in lieu of $100 million. This 

proposed rule does not contain such a 

mandate. 

E. Paperwork Reduction Act 

The Paperwork Reduction Act of 1995 

requires that the FAA consider the 

impact of paperwork and other 

information collection burdens imposed 

on the public. According to the 1995 

amendments to the Paperwork 

Reduction Act (5 CFR 1320.8(b)(2)(vi)), 

an agency may not collect or sponsor 

the collection of information, nor may it 

impose any information collection 

requirement unless it displays a 

currently valid Office of Management 

and Budget (OMB) control number. 

This final rule will impose the 

following new information collection 

requirements. As required by 44 U.S.C. 

3507(d) of the Paperwork Reduction Act 

of 1995, the FAA has submitted 

requirements associated with this rule 

to OMB for its review. Notice of OMB 

approval for this information collection 

will be published in a future Federal 

Register document. 

Summary: This rule adds new 

certification standards for normal and 

transport category rotorcraft to address 

advances in structural damage tolerance 

and fatigue substantiation technology 

for composite rotorcraft structures. The 

rule increases the current minimum 

safety standards to require compliance 

with certain current industry practices 

and FAA policies that would result in 

higher safety standards, and result in 

harmonized international standards. 

The rule helps ensure that if damage 

occurs to composite structures during 

manufacturing or within the operational 

life of the rotorcraft, the remaining 

structure can withstand fatigue loads 

that are likely to occur, without failure, 

until the damage is detected. The 

damaged structure must be repaired or 

the part must be replaced to restore 

ultimate load capability. Sections 

27.573 and 29.573 require that 

applicants get FAA approval of their 

proposed methods for complying with 

the certification requirements for 

damage tolerance and fatigue evaluation 

of composite structures. 

Public comments: No public 

comments were received on the 

information collection requirements 

discussed in the NPRM. 

Use: The required damage tolerance 

and fatigue evaluation information will 

be determined for principal composite 

structural elements or components, 


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74662 Federal Register / Vol. 76, No. 231 / Thursday, December 1, 2011 / Rules and Regulations 

detail design points, and fabrication 

techniques and will be collected from 

rotorcraft certification applicants. The 

FAA will use the approval process for 

the applicant’s submitted compliance 

methodology to determine whether the 

proposed methods are sufficient to 

comply with the certification 

requirements for damage tolerance and 

fatigue evaluation of composite 

structures. The FAA also will use the 

approval process for the applicant’s 

submitted compliance methodology to 

determine if the rotorcraft has any 

unsafe features in the composite 

structures. 

Respondents (including number of): 

The likely respondents to this damage 

tolerance and fatigue evaluation 

information are applicants requesting 

type certification of composite 

structures. We anticipate about 16.5 

normal and transport category rotorcraft 

certification applicants (including 

supplemental type certificate 

applicants) over the 27 year analysis 

period or about 0.6 per year. 

Frequency: The frequency of 

determining the damage tolerance and 

fatigue evaluation methodologies will 

depend on how often an applicant seeks 

certification of a composite structure. 

This compliance methodology will be 

provided during each certification. We 

anticipate 16.5 certifications over the 27 

year analysis period or about 0.6 per 

year. 

Annual Burden Estimate: The 

compliance methodology will be 

required to be submitted and approved 

during each certification of a composite 

rotorcraft structure. We anticipate there 

will be 0.6 certifications each year and 

it will take 182 hours to submit and 

approve the compliance methodology 

for each certification, for a total annual 

time burden of 109 hours. We anticipate 

that submitting and approving the 

compliance methodology for each 

certification will cost $100 per hour. 

Therefore, the estimated total annual 

cost burden will be $10,900. 

F. International Compatibility 

In keeping with U.S. obligations 

under the Convention on International 

Civil Aviation, it is FAA policy to 

conform our regulations to International 

Civil Aviation Organization (ICAO) 

Standards and Recommended Practices 

to the maximum extent practicable. The 

FAA has reviewed the corresponding 

ICAO Standards and Recommended 

Practices and has identified no 

‘‘differences’’ with these regulations. 

G. Environmental Analysis 

FAA Order 1050.1E identifies FAA 

actions that are categorically excluded 

from preparation of an environmental 

assessment or environmental impact 

statement under the National 

Environmental Policy Act in the 

absence of extraordinary circumstances. 

The FAA has determined this 

rulemaking action qualifies for the 

categorical exclusion identified in 

paragraph 312f and involves no 

extraordinary circumstances. 

H. Regulations Affecting Intrastate 

Aviation in Alaska 

Section 1205 of the FAA 

Reauthorization Act of 1996 (110 Stat. 

3213) requires the FAA, when 

modifying its regulations in a manner 

affecting intrastate aviation in Alaska, to 

consider the extent to which Alaska is 

not served by transportation modes 

other than aviation, and to establish 

appropriate regulatory distinctions. In 

the NPRM, the FAA requested 

comments on whether the proposed rule 

should apply differently to intrastate 

operations in Alaska. The agency did 

not receive any comments, and has 

determined, based on the administrative 

record of this rulemaking, that there is 

no need to make any regulatory 

distinctions applicable to intrastate 

aviation in Alaska. 

V. Executive Order Determinations 

A. Executive Order 13132, Federalism 

The FAA has analyzed this final rule 

under the principles and criteria of 

Executive Order 13132, Federalism. The 

agency determined that this action will 

not have a substantial direct effect on 

the States, or the relationship between 

the Federal Government and the States, 

or on the distribution of power and 

responsibilities among the various 

levels of government, and, therefore, 

does not have Federalism implications. 

B. Executive Order 13211, Regulations 

That Significantly Affect Energy Supply, 

Distribution, or Use 

The FAA analyzed this final rule 

under Executive Order 13211, Actions 

Concerning Regulations that 

Significantly Affect Energy Supply, 

Distribution, or Use (May 18, 2001). The 

agency has determined that it is not a 

‘‘significant energy action’’ under the 

executive order and it is not likely to 

have a significant adverse effect on the 

supply, distribution, or use of energy. 

VI. How To Obtain Additional 

Information 

A. Rulemaking Documents 

An electronic copy of a rulemaking 

document may be obtained by using the 

Internet— 

1. Search the Federal Docket 

Management System (http:// 

www.regulations.gov); 

2. Visit the FAA’s Regulations and 

Policies Web page at http:// 

www.faa.gov/regulations_policies/; or 

3. Access the Government Printing 

Office’s Web page at http:// 

www.gpoaccess.gov/fr/index.html. 

Copies may also be obtained by 

sending a request (identified by notice, 

amendment, or docket number of this 

rulemaking) to the Federal Aviation 

Administration, Office of Rulemaking, 

ARM–1, 800 Independence Avenue 

SW., Washington, DC 20591, or by 

calling (202) 267–9680. 

B. Comments Submitted to the Docket 

Comments received may be viewed by 

going to http://www.regulations.gov and 

following the online instructions to 

search the docket number for this 

action. Anyone is able to search the 

electronic form of all comments 

received into any of the FAA’s dockets 

by the name of the individual 

submitting the comment (or signing the 

comment, if submitted on behalf of an 

association, business, labor union, etc.). 

C. Small Business Regulatory 

Enforcement Fairness Act 

The Small Business Regulatory 

Enforcement Fairness Act (SBREFA) of 

1996 requires FAA to comply with 

small entity requests for information or 

advice about compliance with statutes 

and regulations within its jurisdiction. 

A small entity with questions regarding 

this document, may contact its local 

FAA official, or the person listed under 

the FOR FURTHER INFORMATION CONTACT

heading at the beginning of the 

preamble. To find out more about 

SBREFA on the Internet, visit http:// 

www.faa.gov/regulations_policies/ 

rulemaking/sbre_act/. 

List of Subjects 

14 CFR Part 27 

Aircraft, Aviation safety. 

14 CFR Part 29 

Aircraft, Aviation safety. 

The Amendment 

In consideration of the foregoing, the 

Federal Aviation Administration 

amends chapter I, parts 27 and 29 of 

Title 14, Code of Federal Regulations as 

follows: 

PART 27—AIRWORTHINESS 

STANDARDS: NORMAL CATEGORY 

ROTORCRAFT 

■ 1. The authority citation for part 27 

continues to read as follows: 


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Federal Register / Vol. 76, No. 231 / Thursday, December 1, 2011 / Rules and Regulations 74663 

Authority: 49 U.S.C. 106(g), 40113, 44701– 

44702, 44704. 

■ 2. Add § 27.573 to read as follows: 

§ 27.573 Damage Tolerance and Fatigue 

Evaluation of Composite Rotorcraft 

Structures. 

(a) Each applicant must evaluate the 

composite rotorcraft structure under the 

damage tolerance standards of 

paragraph (d) of this section unless the 

applicant establishes that a damage 

tolerance evaluation is impractical 

within the limits of geometry, 

inspectability, and good design practice. 

If an applicant establishes that it is 

impractical within the limits of 

geometry, inspectability, and good 

design practice, the applicant must do a 

fatigue evaluation in accordance with 

paragraph (e) of this section. 

(b) The methodology used to establish 

compliance with this section must be 

submitted to and approved by the 

Administrator. 

(c) Definitions: 

(1) Catastrophic failure is an event 

that could prevent continued safe flight 

and landing. 

(2) Principal Structural Elements 

(PSEs) are structural elements that 

contribute significantly to the carrying 

of flight or ground loads, the failure of 

which could result in catastrophic 

failure of the rotorcraft. 

(3) Threat Assessment is an 

assessment that specifies the locations, 

types, and sizes of damage, considering 

fatigue, environmental effects, intrinsic 

and discrete flaws, and impact or other 

accidental damage (including the 

discrete source of the accidental 

damage) that may occur during 

manufacture or operation. 

(d) Damage Tolerance Evaluation: 

(1) Each applicant must show that 

catastrophic failure due to static and 

fatigue loads, considering the intrinsic 

or discrete manufacturing defects or 

accidental damage, is avoided 

throughout the operational life or 

prescribed inspection intervals of the 

rotorcraft by performing damage 

tolerance evaluations of the strength of 

composite PSEs and other parts, detail 

design points, and fabrication 

techniques. Each applicant must 

account for the effects of material and 

process variability along with 

environmental conditions in the 

strength and fatigue evaluations. Each 

applicant must evaluate parts that 

include PSEs of the airframe, main and 

tail rotor drive systems, main and tail 

rotor blades and hubs, rotor controls, 

fixed and movable control surfaces, 

engine and transmission mountings, 

landing gear, other parts, detail design 

points, and fabrication techniques 

deemed critical by the FAA. Each 

damage tolerance evaluation must 

include: 

(i) The identification of all PSEs; 

(ii) In-flight and ground 

measurements for determining the loads 

or stresses for all PSEs for all critical 

conditions throughout the range of 

limits in § 27.309 (including altitude 

effects), except that maneuvering load 

factors need not exceed the maximum 

values expected in service; 

(iii) The loading spectra as severe as 

those expected in service based on loads 

or stresses determined under paragraph 

(d)(1)(ii) of this section, including 

external load operations, if applicable, 

and other operations including hightorque events; 

(iv) A threat assessment for all PSEs 

that specifies the locations, types, and 

sizes of damage, considering fatigue, 

environmental effects, intrinsic and 

discrete flaws, and impact or other 

accidental damage (including the 

discrete source of the accidental 

damage) that may occur during 

manufacture or operation; and 

(v) An assessment of the residual 

strength and fatigue characteristics of all 

PSEs that supports the replacement 

times and inspection intervals 

established under paragraph (d)(2) of 

this section. 

(2) Each applicant must establish 

replacement times, inspections, or other 

procedures for all PSEs to require the 

repair or replacement of damaged parts 

before a catastrophic failure. These 

replacement times, inspections, or other 

procedures must be included in the 

Airworthiness Limitations Section of 

the Instructions for Continued 

Airworthiness required by § 27.1529. 

(i) Replacement times for PSEs must 

be determined by tests, or by analysis 

supported by tests, and must show that 

the structure is able to withstand the 

repeated loads of variable magnitude 

expected in-service. In establishing 

these replacement times, the following 

items must be considered: 

(A) Damage identified in the threat 

assessment required by paragraph 

(d)(1)(iv) of this section; 

(B) Maximum acceptable 

manufacturing defects and in-service 

damage (i.e., those that do not lower the 

residual strength below ultimate design 

loads and those that can be repaired to 

restore ultimate strength); and 

(C) Ultimate load strength capability 

after applying repeated loads. 

(ii) Inspection intervals for PSEs must 

be established to reveal any damage 

identified in the threat assessment 

required by paragraph (d)(1)(iv) of this 

section that may occur from fatigue or 

other in-service causes before such 

damage has grown to the extent that the 

component cannot sustain the required 

residual strength capability. In 

establishing these inspection intervals, 

the following items must be considered: 

(A) The growth rate, including nogrowth, of the damage under the 

repeated loads expected in-service 

determined by tests or analysis 

supported by tests; 

(B) The required residual strength for 

the assumed damage established after 

considering the damage type, inspection 

interval, detectability of damage, and 

the techniques adopted for damage 

detection. The minimum required 

residual strength is limit load; and 

(C) Whether the inspection will detect 

the damage growth before the minimum 

residual strength is reached and restored 

to ultimate load capability, or whether 

the component will require 

replacement. 

(3) Each applicant must consider the 

effects of damage on stiffness, dynamic 

behavior, loads, and functional 

performance on all PSEs when 

substantiating the maximum assumed 

damage size and inspection interval. 

(e) Fatigue Evaluation: If an applicant 

establishes that the damage tolerance 

evaluation described in paragraph (d) of 

this section is impractical within the 

limits of geometry, inspectability, or 

good design practice, the applicant must 

do a fatigue evaluation of the particular 

composite rotorcraft structure and: 

(1) Identify all PSEs considered in the 

fatigue evaluation; 

(2) Identify the types of damage for all 

PSEs considered in the fatigue 

evaluation; 

(3) Establish supplemental procedures 

to minimize the risk of catastrophic 

failure associated with the damages 

identified in paragraph (d) of this 

section; and 

(4) Include these supplemental 

procedures in the Airworthiness 

Limitations section of the Instructions 

for Continued Airworthiness required 

by § 27.1529. 

Appendix A to Part 27 [Amended] 

■ 3. Amend the second sentence of 

section A.27.4 of Appendix A to Part 27 

by removing the phrase ‘‘approved 

under § 27.571’’ and adding the phrase 

‘‘required for type certification’’ in its 

place. 

PART 29—AIRWORTHINESS 

STANDARDS: TRANSPORT 

CATEGORY ROTORCRAFT 

■ 4. The authority citation for part 29 

continues to read as follows: 

Authority: 49 U.S.C. 106(g), 40113, 44701– 

44702, 44704. 


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74664 Federal Register / Vol. 76, No. 231 / Thursday, December 1, 2011 / Rules and Regulations 

■ 5. Add § 29.573 to read as follows: 

§ 29.573 Damage Tolerance and Fatigue 

Evaluation of Composite Rotorcraft 

Structures. 

(a) Each applicant must evaluate the 

composite rotorcraft structure under the 

damage tolerance standards of 

paragraph (d) of this section unless the 

applicant establishes that a damage 

tolerance evaluation is impractical 

within the limits of geometry, 

inspectability, and good design practice. 

If an applicant establishes that it is 

impractical within the limits of 

geometry, inspectability, and good 

design practice, the applicant must do a 

fatigue evaluation in accordance with 

paragraph (e) of this section. 

(b) The methodology used to establish 

compliance with this section must be 

submitted to and approved by the 

Administrator. 

(c) Definitions: 

(1) Catastrophic failure is an event 

that could prevent continued safe flight 

and landing. 

(2) Principal Structural Elements 

(PSEs) are structural elements that 

contribute significantly to the carrying 

of flight or ground loads, the failure of 

which could result in catastrophic 

failure of the rotorcraft. 

(3) Threat Assessment is an 

assessment that specifies the locations, 

types, and sizes of damage, considering 

fatigue, environmental effects, intrinsic 

and discrete flaws, and impact or other 

accidental damage (including the 

discrete source of the accidental 

damage) that may occur during 

manufacture or operation. 

(d) Damage Tolerance Evaluation: 

(1) Each applicant must show that 

catastrophic failure due to static and 

fatigue loads, considering the intrinsic 

or discrete manufacturing defects or 

accidental damage, is avoided 

throughout the operational life or 

prescribed inspection intervals of the 

rotorcraft by performing damage 

tolerance evaluations of the strength of 

composite PSEs and other parts, detail 

design points, and fabrication 

techniques. Each applicant must 

account for the effects of material and 

process variability along with 

environmental conditions in the 

strength and fatigue evaluations. Each 

applicant must evaluate parts that 

include PSEs of the airframe, main and 

tail rotor drive systems, main and tail 

rotor blades and hubs, rotor controls, 

fixed and movable control surfaces, 

engine and transmission mountings, 

landing gear, other parts, detail design 

points, and fabrication techniques 

deemed critical by the FAA. Each 

damage tolerance evaluation must 

include: 

(i) The identification of all PSEs; 

(ii) In-flight and ground 

measurements for determining the loads 

or stresses for all PSEs for all critical 

conditions throughout the range of 

limits in § 29.309 (including altitude 

effects), except that maneuvering load 

factors need not exceed the maximum 

values expected in service; 

(iii) The loading spectra as severe as 

those expected in service based on loads 

or stresses determined under paragraph 

(d)(1)(ii) of this section, including 

external load operations, if applicable, 

and other operations including hightorque events; 

(iv) A threat assessment for all PSEs 

that specifies the locations, types, and 

sizes of damage, considering fatigue, 

environmental effects, intrinsic and 

discrete flaws, and impact or other 

accidental damage (including the 

discrete source of the accidental 

damage) that may occur during 

manufacture or operation; and 

(v) An assessment of the residual 

strength and fatigue characteristics of all 

PSEs that supports the replacement 

times and inspection intervals 

established under paragraph (d)(2) of 

this section. 

(2) Each applicant must establish 

replacement times, inspections, or other 

procedures for all PSEs to require the 

repair or replacement of damaged parts 

before a catastrophic failure. These 

replacement times, inspections, or other 

procedures must be included in the 

Airworthiness Limitations Section of 

the Instructions for Continued 

Airworthiness required by § 29.1529. 

(i) Replacement times for PSEs must 

be determined by tests, or by analysis 

supported by tests, and must show that 

the structure is able to withstand the 

repeated loads of variable magnitude 

expected in-service. In establishing 

these replacement times, the following 

items must be considered: 

(A) Damage identified in the threat 

assessment required by paragraph 

(d)(1)(iv) of this section; 

(B) Maximum acceptable 

manufacturing defects and in-service 

damage (i.e., those that do not lower the 

residual strength below ultimate design 

loads and those that can be repaired to 

restore ultimate strength); and 

(C) Ultimate load strength capability 

after applying repeated loads. 

(ii) Inspection intervals for PSEs must 

be established to reveal any damage 

identified in the threat assessment 

required by paragraph (d)(1)(iv) of this 

section that may occur from fatigue or 

other in-service causes before such 

damage has grown to the extent that the 

component cannot sustain the required 

residual strength capability. In 

establishing these inspection intervals, 

the following items must be considered: 

(A) The growth rate, including nogrowth, of the damage under the 

repeated loads expected in-service 

determined by tests or analysis 

supported by tests; 

(B) The required residual strength for 

the assumed damage established after 

considering the damage type, inspection 

interval, detectability of damage, and 

the techniques adopted for damage 

detection. The minimum required 

residual strength is limit load; and 

(C) Whether the inspection will detect 

the damage growth before the minimum 

residual strength is reached and restored 

to ultimate load capability, or whether 

the component will require 

replacement. 

(3) Each applicant must consider the 

effects of damage on stiffness, dynamic 

behavior, loads, and functional 

performance on all PSEs when 

substantiating the maximum assumed 

damage size and inspection interval. 

(e) Fatigue Evaluation: If an applicant 

establishes that the damage tolerance 

evaluation described in paragraph (d) of 

this section is impractical within the 

limits of geometry, inspectability, or 

good design practice, the applicant must 

do a fatigue evaluation of the particular 

composite rotorcraft structure and: 

(1) Identify all PSEs considered in the 

fatigue evaluation; 

(2) Identify the types of damage for all 

PSEs considered in the fatigue 

evaluation; 

(3) Establish supplemental procedures 

to minimize the risk of catastrophic 

failure associated with the damages 

identified in paragraph (d) of this 

section; and 

(4) Include these supplemental 

procedures in the Airworthiness 

Limitations section of the Instructions 

for Continued Airworthiness required 

by § 29.1529. 

Appendix A to Part 29 [Amended] 

■ 6. Amend the second sentence of 

section A.29.4 of Appendix A to Part 29 

by removing the phrase ‘‘approved 

under § 29.571’’ and adding the phrase 

‘‘required for type certification’’ in its 

place. 

Issued in Washington, DC, on October 4, 

2011. 

J. Randolph Babbitt, 

Administrator. 

[FR Doc. 2011–30945 Filed 11–30–11; 8:45 am] 

BILLING CODE 4910–13–P 


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