Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures, 74655-74664 [2011-30945]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 76, Number 231 (Thursday, December 1, 2011)]
[Rules and Regulations]
[Pages 74655-74664]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-30945]


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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.

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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 
non-standardization 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

[[Page 74656]]

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 
Sec. Sec.  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 Sec.  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 
high-energy, 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 Sec. Sec.  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 Sec. Sec.  27.1529 and 29.1529.
    Additionally, the FAA recognizes that rare types of damage, such as 
high-energy, 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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the requirements of Sec. Sec.  27.571 and 29.571, the new Sec. Sec.  
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, 
Sec. Sec.  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:
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    \1\ Published in the Federal Register, April 5, 2000 (65 FR 
17936).
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     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 Sec.  29.571 (metallics) and Sec.  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 Sec.  29.571 or 
Sec.  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 Sec. Sec.  27.573 and 29.573. 
Therefore, the FAA is adopting the rule as proposed.

Reconciling Difference Between This Rule and the Sec.  29.571 
(Metallics) Rule, in the Approval Authority of Compliance Methodology 
and Methodology Results

    Sikorsky Aircraft identified the difference between Sec. Sec.  
27.573 and 29.573, which refer to FAA approval, and Sec.  29.571 
(metallics), which refers to the Administrator's approval. It states 
that the language used in the approval process should be similar for 
Sec.  29.571 (metallics) and Sec.  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 Sec.  
29.571 (metallics). The intent of Sec. Sec.  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 non-structural 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 non-structural 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 Sec. Sec.  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 Sec.  29.571. The requirement is for evaluating damage 
tolerance as addressed in paragraphs (d) of Sec. Sec.  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 
Sec. Sec.  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 Sec. Sec.  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 (Sec.  2x.605 for parts 27 and 29); and that information on 
the significance, causes, and management procedures for micro-voids 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 Sec. Sec.  27.573(b) and 29.573(b) are reworded to be 
consistent with the wording in Sec.  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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    (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 https://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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[GRAPHIC] [TIFF OMITTED] TR01DE11.295

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.

[[Page 74661]]

[GRAPHIC] [TIFF OMITTED] TR01DE11.296

    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,

[[Page 74662]]

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 (https://www.regulations.gov);
    2. Visit the FAA's Regulations and Policies Web page at https://www.faa.gov/regulations_policies/; or
    3. Access the Government Printing Office's Web page at https://www.gpoaccess.gov/fr/.
    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 https://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 https://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

0
1. The authority citation for part 27 continues to read as follows:


[[Page 74663]]


    Authority:  49 U.S.C. 106(g), 40113, 44701-44702, 44704.


0
2. Add Sec.  27.573 to read as follows:


Sec.  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 Sec.  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 high-torque 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 Sec.  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 no-growth, 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 Sec.  27.1529.

Appendix A to Part 27 [Amended]

0
3. Amend the second sentence of section A.27.4 of Appendix A to Part 27 
by removing the phrase ``approved under Sec.  27.571'' and adding the 
phrase ``required for type certification'' in its place.

PART 29--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT

0
4. The authority citation for part 29 continues to read as follows:

    Authority:  49 U.S.C. 106(g), 40113, 44701-44702, 44704.


[[Page 74664]]



0
5. Add Sec.  29.573 to read as follows:


Sec.  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 Sec.  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 high-torque 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 Sec.  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 no-growth, 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 Sec.  29.1529.

Appendix A to Part 29 [Amended]

0
6. Amend the second sentence of section A.29.4 of Appendix A to Part 29 
by removing the phrase ``approved under Sec.  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