[Federal Register Volume 79, Number 238 (Thursday, December 11, 2014)]
[Rules and Regulations]
[Pages 73462-73469]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-28938]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No.: FAA-2013-0142; Amdt. No. 25-141]
RIN 2120-AK12


Harmonization of Airworthiness Standards--Gust and Maneuver Load 
Requirements

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: This final rule amends certain airworthiness regulations for 
transport category airplanes, based on recommendations from the FAA-
sponsored Aviation Rulemaking Advisory Committee (ARAC). This amendment 
eliminates regulatory differences between the airworthiness standards 
of the FAA and European Aviation Safety Agency (EASA). It does not add 
new requirements beyond what manufacturers currently meet for EASA 
certification and does not affect current industry design practices. 
This final rule revises the pitch maneuver design loads criteria; 
revises the gust and turbulence design loads criteria; revises the 
application of gust loads to engine mounts, high lift devices, and 
other control surfaces; adds a ``round-the-clock'' discrete gust 
criterion and a multi-axis discrete gust criterion for airplanes 
equipped with wing-mounted engines; revises the engine torque loads 
criteria; adds an engine failure dynamic load condition; revises the 
ground gust design loads criteria; revises the criteria used to 
establish the rough air design speed; and requires the establishment of 
a rough air Mach number.

DATES: Effective February 9, 2015.

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'' in the SUPPLEMENTARY INFORMATION 
section of this document.

FOR FURTHER INFORMATION CONTACT: For technical questions concerning 
this action, contact Todd Martin, Airframe and Cabin Safety Branch, 
ANM-115,

[[Page 73463]]

Transport Airplane Directorate, Aircraft Certification Service, Federal 
Aviation Administration, 1601 Lind Avenue SW., Renton, WA 98057-3356; 
telephone (425) 227-1178; facsimile (425) 227-1232; email 
[email protected].
    For legal questions concerning this action, contact Sean Howe, 
Office of the Regional Counsel, ANM-7, Federal Aviation Administration, 
1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone (425) 
227-2591; facsimile (425) 227-1007; email [email protected].

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.'' Under that section, the FAA is charged with promoting 
safe flight of civil aircraft in air commerce by prescribing 
regulations and minimum standards for the design and performance of 
aircraft that the Administrator finds necessary for safety in air 
commerce. This regulation is within the scope of that authority. It 
prescribes new safety standards for the design and operation of 
transport category airplanes.

I. Overview of Final Rule

    The FAA is amending Title 14, Code of Federal Regulations (14 CFR) 
Part 25 as described below. This action harmonizes part 25 requirements 
with the corresponding requirements in Book 1 of the EASA Certification 
Specifications and Acceptable Means of Compliance for Large Aeroplanes 
(CS-25). As such, this action--
    1. Revises Sec.  25.331, ``Symmetric maneuvering conditions,'' to 
prescribe both positive and negative checked pitch maneuver loads that 
take into account the size of the airplane and any effects of the 
flight control system. The introductory paragraph, Sec.  25.331(c), is 
revised by moving some criteria to Sec.  25.331(c)(2) where those 
criteria apply.
    2. Removes appendix G to part 25, ``Continuous Gust Design 
Criteria,'' and Sec.  25.341(b) now clearly sets forth the continuous 
turbulence requirement.
    3. Revises Sec.  25.341, ``Gust and turbulence loads,'' to--
     Remove the optional mission analysis method currently 
specified in appendix G in favor of the design envelope analysis 
method.
     Update the turbulence intensity criteria in Sec.  
25.341(b) to take into account in-service measurements of derived gust 
intensities.
     Update Sec.  25.341(a) to require evaluation of discrete 
gust conditions at airplane speeds from design speed for maximum gust 
intensity, VB, to design cruising speed, VC, 
(previously required only at VC) and to specify reference 
gust velocities up to 60,000 feet, rather than the previously specified 
50,000 feet.
     Add a new paragraph Sec.  25.341(c) that specifies a 
``round-the-clock'' discrete gust criterion and a multi-axis discrete 
gust criterion for airplanes equipped with wing-mounted engines.
    4. Revises Sec.  25.343, ``Design fuel and oil loads,'' Sec.  
25.345, ``High lift devices,'' Sec.  25.371, ``Gyroscopic loads,'' 
Sec.  25.373, ``Speed control devices,'' and Sec.  25.391, ``Control 
surface loads: General,'' by adding to each of these regulations a 
requirement to evaluate the continuous turbulence loads criteria in 
Sec.  25.341(b).
    5. Revises Sec.  25.361, ``Engine and auxiliary power unit 
torque,'' to--
     Remove the requirement to assess engine torque loads due 
to engine structural failures (this requirement is re-established in 
the new Sec.  25.362, outlined below).
     Provide specific engine torque load criteria for auxiliary 
power unit installations.
     Remove the requirements that apply to reciprocating 
engines.
     Change the title of Sec.  25.361 from ``Engine torque'' to 
``Engine and auxiliary power unit torque.''
    6. Adds new Sec.  25.362, ``Engine failure loads,'' to require 
engine mounts and supporting airframe structure be designed for 1g 
flight loads combined with the most critical transient dynamic loads 
and vibrations resulting from failure of a blade, shaft, bearing or 
bearing support, or bird strike event.
    7. Revises Sec.  25.391, ``Control surface loads: General,'' and 
Sec.  25.395, ``Control system,'' to remove references to the ground 
gust requirements in Sec.  25.415.
    8. Revises Sec.  25.415, ``Ground gust conditions'' to--
     Reorganize and clarify the design conditions to be 
considered.
     Identify the components and parts of the control system to 
which each of the conditions apply.
     Make it stand alone in regard to the required multiplying 
factors and to provide an additional multiplying factor to account for 
dynamic amplification.
    9. Revises Sec.  25.1517, ``Rough air speed, VRA'' to 
remove the reference to VB in the definition of rough air speed and to 
require that a rough air Mach number, MRA, be established in addition 
to rough air speed. Also, this action removes the reference to Sec.  
25.1585, ``Operating procedures,'' because it is no longer applicable 
since that regulation was modified.

II. Background

A. Statement of the Problem

    Part 25 prescribes airworthiness standards for type certification 
of transport category airplanes for products certified in the United 
States. EASA CS-25 Book 1 prescribes the corresponding airworthiness 
standards for products certified in Europe. While part 25 and CS-25 
Book 1 are similar, they differ in several respects.
    The FAA tasked ARAC through the Loads and Dynamics Harmonization 
Working Group (LDHWG) to review existing structures regulations and 
recommend changes that would eliminate differences between the U.S. and 
European airworthiness standards. The LDHWG developed recommendations, 
which EASA has incorporated into CS-25 with some changes. The FAA 
agrees with the ARAC recommendations as adopted by EASA, and this final 
rule amends part 25 accordingly.

B. Summary of the NPRM

    On May 6, 2013, the FAA issued a Notice of Proposed Rulemaking 
(NPRM), Notice No. 25-139,\1\ Docket No. FAA-2013-0142, to amend 
Sec. Sec.  25.331, 25.341, 25.343, 25.345, 25.361, 25.371, 25.373, 
25.391, 25.395, 25.415, and 25.1517; to add Sec.  25.362; and to remove 
appendix G of 14 CFR part 25. That NPRM was published in the Federal 
Register on May 28, 2013 (78 FR 31851). In the NPRM, the FAA proposed 
to (1) revise the pitch maneuver design loads criteria; (2) revise the 
gust and turbulence design loads criteria; (3) revise the application 
of gust loads to engine mounts, high lift devices, and other control 
surfaces; (4) add a ``round-the-clock'' discrete gust criterion and a 
multi-axis discrete gust criterion for airplanes equipped with wing-
mounted engines; (5) revise the engine torque loads criteria and add an 
engine failure dynamic load condition; (6) revise the ground gust 
design loads criteria; (7) revise the criteria used to establish the 
rough air design speed; and (8) require the establishment of a rough 
air Mach number.
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    \1\ On April 16, 2014, the Federal Register published a 
correction (79 FR 21413) changing the Notice No. to ``13-04'' for 
the NPRM that published May 28, 2013 (78 FR 31851) and for 
subsequent NPRM corrections that published June 24, 2013 (78 FR 
37722) and July 16, 2013 (78 FR 42480).

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[[Page 73464]]

    The FAA proposed these changes to eliminate regulatory differences 
between the airworthiness standards of the FAA and EASA. The NPRM 
comment period closed on August 26, 2013.
    On June 24, 2013, the Federal Register published a correction to 
the NPRM to correct three equations in the proposed amendments to Sec.  
25.341 (78 FR 37722). On July 16, 2013, the Federal Register published 
a second correction to one equation in the proposed amendments to Sec.  
25.341 (78 FR 42480). The equations in this final rule have not changed 
from those in the corrected NPRM.

C. General Overview of Comments

    The FAA received two comments. One commenter supported the NPRM and 
the ongoing international harmonization of certification requirements. 
The other comment addressed Sec.  25.341 and is discussed below.

III. Discussion of Public Comments and Final Rule

A. Section 25.341, ``Gust and Turbulence Loads''

    Section 25.341(a)(6) uses the term Zmo, which is the 
maximum operating altitude, in feet, specifically defined in Sec.  
25.1527. A commenter noted that the units for the term Zmo 
are not provided in the current rule. While Sec.  25.341(a)(6) was not 
being revised as part of this rulemaking, the commenter recommended 
that this paragraph be revised to include the appropriate units for 
Zmo (feet) for ease of reference. We agree, and revise the 
rule as recommended.

B. Section 25.415, ``Ground Gust Conditions''

    After further FAA review of what we proposed by NPRM, we now 
specify that control system gust locks are to be taken into account 
only when the airplane is so equipped. As proposed, Sec.  25.415 would 
have required that the airplane be evaluated while taxiing with the 
controls locked and unlocked, and while parked with the controls 
locked. However, many transport category airplanes with powered flight 
controls do not have control system gust locks. As noted in the NPRM, 
these airplanes rely on their hydraulic actuators to provide protection 
from ground gusts. We, therefore, now revise Sec.  25.415 to clarify 
that, for all airplanes, the ground gust conditions apply when the 
airplane is taxiing and while parked. For airplanes that include 
control system gust locks, the taxiing condition must be evaluated with 
the controls locked and unlocked, and the parked condition must be 
evaluated with the controls locked. Airplanes not equipped with gust 
locks are to be evaluated in their normal configuration while taxiing 
and while parked. With these changes to Sec.  25.415, the rule wording 
will no longer be exactly the same as CS 25.415; however, the intent of 
the two rules is the same in how airplanes with and without gust locks 
are evaluated.

C. Advisory Material

    On May 31, 2013, the FAA published and solicited public comments on 
three proposed ACs that describe acceptable means for showing 
compliance with the NPRM's proposed regulations. The comment period for 
the proposed ACs closed on September 26, 2013. The FAA did not receive 
any comments on the proposed ACs. Concurrently with this final rule, 
the FAA is issuing the following final ACs to provide guidance material 
for the new regulations adopted by this amendment:
     AC 25.341-1, ``Dynamic Gust Loads.''
     AC 25.362-1, ``Engine Failure Loads.''
     AC 25.415-1, ``Ground Gust Conditions.''

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 
(Public Law 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, the 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 final rule.
    Department of Transportation Order DOT 2100.5 prescribes policies 
and procedures for simplification, analysis, and review of regulations. 
If the expected cost impact is so minimal that a proposed or final rule 
does not warrant a full evaluation, this order permits that a statement 
to that effect and the basis for it be included in the preamble if a 
full regulatory evaluation of the cost and benefits is not prepared. 
Such a determination has been made for this final rule. The reasoning 
for this determination follows.
    The FAA is amending certain airworthiness standards for transport 
category airplanes. Adopting this final rule will eliminate regulatory 
differences between the airworthiness standards of the FAA and EASA. 
This final rule does not add new requirements beyond what manufacturers 
currently meet for EASA certification and does not affect current 
industry design practices. Meeting two sets of certification 
requirements raises the cost of developing new transport category 
airplanes with little to no increase in safety. In the interest of 
fostering international trade, lowering the cost of manufacturing new 
transport category airplanes, and making the certification process more 
efficient, the FAA, EASA, and several industry working groups came 
together to create, to the maximum extent possible, a single set of 
certification requirements that would be accepted in both the United 
States and Europe. Therefore, as a result of these harmonization 
efforts, the FAA is amending the airworthiness regulations described in 
section I of this final rule, ``Overview of Final Rule.'' This action 
harmonizes part 25 requirements with the corresponding requirements in 
EASA CS-25 Book 1.
    Currently, all manufacturers of transport category airplanes, 
certificated under part 25 are expected to continue their current 
practice of compliance with the EASA certification requirements in CS-
25 Book 1. Since future certificated transport airplanes are expected 
to meet CS-25 Book 1, and this rule simply adopts EASA requirements, 
manufacturers will incur minimal or no additional cost resulting from 
this final rule. The FAA made this same determination in the NPRM and 
received no comments.
    The FAA has, therefore, determined that this final rule is not a 
``significant regulatory action'' as defined in section 3(f) of 
Executive Order 12866, and is not ``significant'' as defined in DOT's 
Regulatory Policies and Procedures.

[[Page 73465]]

B. Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (Public Law 96-354) (RFA) 
establishes ``as a principle of regulatory issuance that agencies shall 
endeavor, consistent with the objectives of the rule and of applicable 
statutes, to fit regulatory and informational requirements to the scale 
of the businesses, organizations, and governmental jurisdictions 
subject to regulation. To achieve this principle, agencies are required 
to solicit and consider flexible regulatory proposals and to explain 
the rationale for their actions to assure that such proposals are given 
serious consideration.'' 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 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 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.
    In the NPRM, the FAA determined that this rule would not impose 
more than minimal cost.
    The FAA believes that this final rule does not have a significant 
economic impact on a substantial number of small entities for the 
following reasons. We did not receive any comments from small entities. 
All United States transport category airplane manufacturers exceed the 
Small Business Administration small-entity criteria of 1,500 employees. 
Therefore, as provided in section 605(b), the head of the FAA certifies 
that this rulemaking will not result in a significant economic impact 
on a substantial number of small entities.

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, the establishment of 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 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 final rule and determined that it 
is in accord with the Trade Agreements Act as the rule furthers the 
legitimate domestic objectives of safety, creates no unnecessary 
obstacles to foreign commerce, does not exclude imports, and uses 
European standards as the basis for United States regulation.

D. Unfunded Mandates Assessment

    Title II of the Unfunded Mandates Reform Act of 1995 (Public Law 
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 
(in 1995 dollars) in any one 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 $151 million in lieu of $100 
million. This final rule does not contain such a mandate; therefore, 
the requirements of Title II of the Act do not apply.

E. Paperwork Reduction Act

    The Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d)) requires 
that the FAA consider the impact of paperwork and other information 
collection burdens imposed on the public. The FAA has determined that 
there is no new requirement for information collection associated with 
this final rule.

F. International Compatibility and Cooperation

    (1) In keeping with U.S. obligations under the Convention on 
International Civil Aviation, it is FAA policy to conform 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.
    (2) Executive Order (EO) 13609, Promoting International Regulatory 
Cooperation (77 FR 26413, May 4, 2012), promotes international 
regulatory cooperation to meet shared challenges involving health, 
safety, labor, security, environmental, and other issues and reduce, 
eliminate, or prevent unnecessary differences in regulatory 
requirements. The FAA has analyzed this action under the policy and 
agency responsibilities of Executive Order 13609, Promoting 
International Regulatory Cooperation. The agency has determined that 
this action would eliminate differences between U.S. aviation standards 
and those of other civil aviation authorities by creating a single set 
of certification requirements for transport category airplanes that 
would be acceptable in both the United States and Europe.

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 of Order 1050.1E and involves no 
extraordinary circumstances.

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.

[[Page 73466]]

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 eRulemaking Portal (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.gpo.gov/fdsys/.
    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 the 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 in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

The Amendment

    In consideration of the foregoing, the Federal Aviation 
Administration amends part 25 of title 14, Code of Federal Regulations 
as follows:

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

0
1. The authority citation for part 25 continues to read as follows:

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


0
2. Amend Sec.  25.331 by revising paragraph (c) introductory text and 
paragraph (c)(2) to read as follows:


Sec.  25.331  Symmetric maneuvering conditions.

* * * * *
    (c) Maneuvering pitching conditions. The following conditions must 
be investigated:
* * * * *
    (2) Checked maneuver between VA and VD. Nose-up checked pitching 
maneuvers must be analyzed in which the positive limit load factor 
prescribed in Sec.  25.337 is achieved. As a separate condition, nose-
down checked pitching maneuvers must be analyzed in which a limit load 
factor of 0g is achieved. In defining the airplane loads, the flight 
deck pitch control motions described in paragraphs (c)(2)(i) through 
(iv) of this section must be used:
    (i) The airplane is assumed to be flying in steady level flight at 
any speed between VA and VD and the flight deck 
pitch control is moved in accordance with the following formula:

[delta](t) = [delta]1 sin([omega]t) for 0 <= t <=t 
max

Where--

[delta]1 = the maximum available displacement of the 
flight deck pitch control in the initial direction, as limited by 
the control system stops, control surface stops, or by pilot effort 
in accordance with Sec.  25.397(b);
[delta](t) = the displacement of the flight deck pitch control as a 
function of time. In the initial direction, [delta](t) is limited to 
[delta]1. In the reverse direction, [delta](t) may be 
truncated at the maximum available displacement of the flight deck 
pitch control as limited by the control system stops, control 
surface stops, or by pilot effort in accordance with 25.397(b);
tmax = 3[pi]/2[omega];
[omega] = the circular frequency (radians/second) of the control 
deflection taken equal to the undamped natural frequency of the 
short period rigid mode of the airplane, with active control system 
effects included where appropriate; but not less than:
[GRAPHIC] [TIFF OMITTED] TR11DE14.023

Where

V = the speed of the airplane at entry to the maneuver.
VA = the design maneuvering speed prescribed in Sec.  
25.335(c).

    (ii) For nose-up pitching maneuvers, the complete flight deck pitch 
control displacement history may be scaled down in amplitude to the 
extent necessary to ensure that the positive limit load factor 
prescribed in Sec.  25.337 is not exceeded. For nose-down pitching 
maneuvers, the complete flight deck control displacement history may be 
scaled down in amplitude to the extent necessary to ensure that the 
normal acceleration at the center of gravity does not go below 0g.
    (iii) In addition, for cases where the airplane response to the 
specified flight deck pitch control motion does not achieve the 
prescribed limit load factors, then the following flight deck pitch 
control motion must be used:

[delta](t) = [delta]1 sin([omega]t) for 0 <= t <= 
t1
[delta](t) = [delta]1 for t1 <= t <= 
t2
[delta](t) = [delta]1 sin([omega][t + t1 - 
t2]) for t2 <= t <= tmax

Where--

t1 = [pi]/2[omega]
t2 = t1 + [Delta]t
tmax = t2 + [pi]/[omega];
[Delta]t = the minimum period of time necessary to allow the 
prescribed limit load factor to be achieved in the initial 
direction, but it need not exceed five seconds (see figure below).

[[Page 73467]]

[GRAPHIC] [TIFF OMITTED] TR11DE14.024

    (iv) In cases where the flight deck pitch control motion may be 
affected by inputs from systems (for example, by a stick pusher that 
can operate at high load factor as well as at 1g), then the effects of 
those systems shall be taken into account.
    (v) Airplane loads that occur beyond the following times need not 
be considered:
    (A) For the nose-up pitching maneuver, the time at which the normal 
acceleration at the center of gravity goes below 0g;
    (B) For the nose-down pitching maneuver, the time at which the 
normal acceleration at the center of gravity goes above the positive 
limit load factor prescribed in Sec.  25.337;
    (C) tmax..

0
3. Amend Sec.  25.341 by revising paragraphs (a)(5)(i), (a)(6), and 
(b), and by adding paragraph (c) to read as follows:


Sec.  25.341  Gust and turbulence loads.

    (a) * * *
* * * * *
    (5) * * *
    (i) At airplane speeds between VB and VC: 
Positive and negative gusts with reference gust velocities of 56.0 ft/
sec EAS must be considered at sea level. The reference gust velocity 
may be reduced linearly from 56.0 ft/sec EAS at sea level to 44.0 ft/
sec EAS at 15,000 feet. The reference gust velocity may be further 
reduced linearly from 44.0 ft/sec EAS at 15,000 feet to 20.86 ft/sec 
EAS at 60,000 feet.
* * * * *
    (6) * * *

Zmo = Maximum operating altitude defined in Sec.  25.1527 
(feet).

* * * * *
    (b) Continuous turbulence design criteria. The dynamic response of 
the airplane to vertical and lateral continuous turbulence must be 
taken into account. The dynamic analysis must take into account 
unsteady aerodynamic characteristics and all significant structural 
degrees of freedom including rigid body motions. The limit loads must 
be determined for all critical altitudes, weights, and weight 
distributions as specified in Sec.  25.321(b), and all critical speeds 
within the ranges indicated in Sec.  25.341(b)(3).
    (1) Except as provided in paragraphs (b)(4) and (5) of this 
section, the following equation must be used:

PL = PL-1g  U[sigma]A

Where--

PL = limit load;
PL-1g = steady 1g load for the condition;
A = ratio of root-mean-square incremental load for the condition to 
root-mean-square turbulence velocity; and
U[sigma] = limit turbulence intensity in true airspeed, specified in 
paragraph (b)(3) of this section.

    (2) Values of A must be determined according to the following 
formula:
[GRAPHIC] [TIFF OMITTED] TR11DE14.025

Where--

H([Omega]) = the frequency response function, determined by dynamic 
analysis, that relates the loads in the aircraft structure to the 
atmospheric turbulence; and
[Phi]([Omega]) = normalized power spectral density of atmospheric 
turbulence given by--
[GRAPHIC] [TIFF OMITTED] TR11DE14.026

Where--

[Omega] = reduced frequency, radians per foot; and
L = scale of turbulence = 2,500 ft.

    (3) The limit turbulence intensities, U[sigma], in feet per second 
true airspeed required for compliance with this paragraph are--
    (i) At airplane speeds between VB and VC: 
U[sigma] = U[sigma]ref Fg

Where--

U[sigma]ref is the reference turbulence intensity that varies 
linearly with altitude from 90 fps (TAS) at sea level to 79 fps 
(TAS) at 24,000 feet and is then constant at 79 fps (TAS) up to the 
altitude of 60,000 feet.
Fg is the flight profile alleviation factor defined in 
paragraph (a)(6) of this section;

    (ii) At speed VD: U[sigma] is equal to \1/2\ the values 
obtained under paragraph (b)(3)(i) of this section.
    (iii) At speeds between VC and VD: U[sigma] 
is equal to a value obtained by linear interpolation.
    (iv) At all speeds, both positive and negative incremental loads 
due to continuous turbulence must be considered.
    (4) When an automatic system affecting the dynamic response of the 
airplane is included in the analysis, the effects of system non-
linearities on loads at the limit load level must be taken into account 
in a realistic or conservative manner.
    (5) If necessary for the assessment of loads on airplanes with 
significant non-linearities, it must be assumed that the turbulence 
field has a root-mean-square velocity equal to 40 percent of the 
U[sigma] values specified in paragraph (b)(3) of this section. The 
value of limit load is that load with the same probability of 
exceedance in the turbulence field as AU[sigma] of the same load 
quantity in a linear approximated model.
    (c) Supplementary gust conditions for wing-mounted engines. For 
airplanes equipped with wing-mounted engines, the engine mounts, 
pylons, and wing supporting structure must be designed for the maximum 
response at the nacelle center of gravity derived from the following 
dynamic gust conditions applied to the airplane:
    (1) A discrete gust determined in accordance with Sec.  25.341(a) 
at each angle normal to the flight path, and separately,
    (2) A pair of discrete gusts, one vertical and one lateral. The 
length of each of these gusts must be independently tuned to the 
maximum response in accordance with Sec.  25.341(a). The penetration of 
the airplane in the combined gust field and the phasing of

[[Page 73468]]

the vertical and lateral component gusts must be established to develop 
the maximum response to the gust pair. In the absence of a more 
rational analysis, the following formula must be used for each of the 
maximum engine loads in all six degrees of freedom:
[GRAPHIC] [TIFF OMITTED] TR11DE14.027

Where--

PL = limit load;
PL-1g = steady 1g load for the condition;
LV = peak incremental response load due to a vertical 
gust according to Sec.  25.341(a); and
LL = peak incremental response load due to a lateral gust 
according to Sec.  25.341(a).


0
4. Amend Sec.  25.343 by revising paragraph (b)(1)(ii) to read as 
follows:


Sec.  25.343  Design fuel and oil loads.

* * * * *
    (b) * * *
    (1) * * *
    (ii) The gust and turbulence conditions of Sec.  25.341(a) and (b), 
but assuming 85% of the gust velocities prescribed in Sec.  
25.341(a)(4) and 85% of the turbulence intensities prescribed in Sec.  
25.341(b)(3).
* * * * *

0
5. Amend Sec.  25.345 by revising paragraph (c)(2) to read as follows:


Sec.  25.345  High lift devices.

* * * * *
    (c) * * *
    (2) The vertical gust and turbulence conditions prescribed in Sec.  
25.341(a) and (b).
* * * * *

0
6. Revise Sec.  25.361 to read as follows:


Sec.  25.361  Engine and auxiliary power unit torque.

    (a) For engine installations--
    (1) Each engine mount, pylon, and adjacent supporting airframe 
structures must be designed for the effects of--
    (i) A limit engine torque corresponding to takeoff power/thrust 
and, if applicable, corresponding propeller speed, acting 
simultaneously with 75% of the limit loads from flight condition A of 
Sec.  25.333(b);
    (ii) A limit engine torque corresponding to the maximum continuous 
power/thrust and, if applicable, corresponding propeller speed, acting 
simultaneously with the limit loads from flight condition A of Sec.  
25.333(b); and
    (iii) For turbopropeller installations only, in addition to the 
conditions specified in paragraphs (a)(1)(i) and (ii) of this section, 
a limit engine torque corresponding to takeoff power and propeller 
speed, multiplied by a factor accounting for propeller control system 
malfunction, including quick feathering, acting simultaneously with 1g 
level flight loads. In the absence of a rational analysis, a factor of 
1.6 must be used.
    (2) The limit engine torque to be considered under paragraph (a)(1) 
of this section must be obtained by--
    (i) For turbopropeller installations, multiplying mean engine 
torque for the specified power/thrust and speed by a factor of 1.25;
    (ii) For other turbine engines, the limit engine torque must be 
equal to the maximum accelerating torque for the case considered.
    (3) The engine mounts, pylons, and adjacent supporting airframe 
structure must be designed to withstand 1g level flight loads acting 
simultaneously with the limit engine torque loads imposed by each of 
the following conditions to be considered separately:
    (i) Sudden maximum engine deceleration due to malfunction or 
abnormal condition; and
    (ii) The maximum acceleration of engine.
    (b) For auxiliary power unit installations, the power unit mounts 
and adjacent supporting airframe structure must be designed to 
withstand 1g level flight loads acting simultaneously with the limit 
torque loads imposed by each of the following conditions to be 
considered separately:
    (1) Sudden maximum auxiliary power unit deceleration due to 
malfunction, abnormal condition, or structural failure; and
    (2) The maximum acceleration of the auxiliary power unit.

0
7. Add Sec.  25.362 to read as follows:


Sec.  25.362  Engine failure loads.

    (a) For engine mounts, pylons, and adjacent supporting airframe 
structure, an ultimate loading condition must be considered that 
combines 1g flight loads with the most critical transient dynamic loads 
and vibrations, as determined by dynamic analysis, resulting from 
failure of a blade, shaft, bearing or bearing support, or bird strike 
event. Any permanent deformation from these ultimate load conditions 
must not prevent continued safe flight and landing.
    (b) The ultimate loads developed from the conditions specified in 
paragraph (a) of this section are to be--
    (1) Multiplied by a factor of 1.0 when applied to engine mounts and 
pylons; and
    (2) Multiplied by a factor of 1.25 when applied to adjacent 
supporting airframe structure.

0
8. Revise Sec.  25.371 to read as follows:


Sec.  25.371  Gyroscopic loads.

    The structure supporting any engine or auxiliary power unit must be 
designed for the loads, including gyroscopic loads, arising from the 
conditions specified in Sec. Sec.  25.331, 25.341, 25.349, 25.351, 
25.473, 25.479, and 25.481, with the engine or auxiliary power unit at 
the maximum rotating speed appropriate to the condition. For the 
purposes of compliance with this paragraph, the pitch maneuver in Sec.  
25.331(c)(1) must be carried out until the positive limit maneuvering 
load factor (point A2 in Sec.  25.333(b)) is reached.

0
9. Amend Sec.  25.373 by revising paragraph (a) to read as follows:


Sec.  25.373  Speed control devices.

* * * * *
    (a) The airplane must be designed for the symmetrical maneuvers 
prescribed in Sec. Sec.  25.333 and 25.337, the yawing maneuvers in 
Sec.  25.351, and the vertical and lateral gust and turbulence 
conditions prescribed in Sec.  25.341(a) and (b) at each setting and 
the maximum speed associated with that setting; and
* * * * *

0
10. Amend Sec.  25.391 by revising the introductory text to read as 
follows:


Sec.  25.391  Control surface loads: General.

    The control surfaces must be designed for the limit loads resulting 
from the flight conditions in Sec. Sec.  25.331, 25.341(a) and (b), 
25.349, and 25.351, considering the requirements for--
* * * * *

0
11. Amend Sec.  25.395 by revising paragraph (b) to read as follows:


Sec.  25.395  Control system.

* * * * *
    (b) The system limit loads of paragraph (a) of this section need 
not exceed the loads that can be produced by the pilot (or pilots) and 
by automatic or power devices operating the controls.
* * * * *

0
12. Revise Sec.  25.415 to read as follows:


Sec.  25.415  Ground gust conditions.

    (a) The flight control systems and surfaces must be designed for 
the limit loads generated when the airplane is subjected to a 
horizontal 65-knot ground gust from any direction while taxiing and 
while parked. For airplanes equipped with control system gust locks, 
the taxiing condition must be evaluated with the controls locked and 
unlocked, and the parked condition must be evaluated with the controls 
locked.
    (b) The control system and surface loads due to ground gust may be

[[Page 73469]]

assumed to be static loads, and the hinge moments H must be computed 
from the formula:
H = K (1/2) [rho]o V\2\ c S

Where--

K = hinge moment factor for ground gusts derived in paragraph (c) of 
this section;
[rho]o = density of air at sea level;
V = 65 knots relative to the aircraft;
S = area of the control surface aft of the hinge line;
c = mean aerodynamic chord of the control surface aft of the hinge 
line.

    (c) The hinge moment factor K for ground gusts must be taken from 
the following table:

------------------------------------------------------------------------
               Surface                    K       Position of  controls
------------------------------------------------------------------------
(1) Aileron.........................       0.75  Control column locked
                                                  or lashed in mid-
                                                  position.
(2) Aileron.........................  * 0.5
                                           0
(3) Elevator........................  * 0.7
                                           5
(4) Elevator........................  * 0.7
                                           5
(5) Rudder..........................       0.75  Rudder in neutral.
(6) Rudder..........................       0.75  Rudder at full throw.
------------------------------------------------------------------------
* A positive value of K indicates a moment tending to depress the
  surface, while a negative value of K indicates a moment tending to
  raise the surface.

    (d) The computed hinge moment of paragraph (b) of this section must 
be used to determine the limit loads due to ground gust conditions for 
the control surface. A 1.25 factor on the computed hinge moments must 
be used in calculating limit control system loads.
    (e) Where control system flexibility is such that the rate of load 
application in the ground gust conditions might produce transient 
stresses appreciably higher than those corresponding to static loads, 
in the absence of a rational analysis substantiating a different 
dynamic factor, an additional factor of 1.6 must be applied to the 
control system loads of paragraph (d) of this section to obtain limit 
loads. If a rational analysis is used, the additional factor must not 
be less than 1.2.
    (f) For the condition of the control locks engaged, the control 
surfaces, the control system locks, and the parts of any control 
systems between the surfaces and the locks must be designed to the 
resultant limit loads. Where control locks are not provided, then the 
control surfaces, the control system stops nearest the surfaces, and 
the parts of any control systems between the surfaces and the stops 
must be designed to the resultant limit loads. If the control system 
design is such as to allow any part of the control system to impact 
with the stops due to flexibility, then the resultant impact loads must 
be taken into account in deriving the limit loads due to ground gust.
    (g) For the condition of taxiing with the control locks disengaged, 
or where control locks are not provided, the following apply:
    (1) The control surfaces, the control system stops nearest the 
surfaces, and the parts of any control systems between the surfaces and 
the stops must be designed to the resultant limit loads.
    (2) The parts of the control systems between the stops nearest the 
surfaces and the flight deck controls must be designed to the resultant 
limit loads, except that the parts of the control system where loads 
are eventually reacted by the pilot need not exceed:
    (i) The loads corresponding to the maximum pilot loads in Sec.  
25.397(c) for each pilot alone; or
    (ii) 0.75 times these maximum loads for each pilot when the pilot 
forces are applied in the same direction.

0
13. Revise 25.1517 to read as follows:


Sec.  25.1517  Rough air speed, VRA.

    (a) A rough air speed, VRA, for use as the recommended 
turbulence penetration airspeed, and a rough air Mach number, 
MRA, for use as the recommended turbulence penetration Mach 
number, must be established. VRA/MRA must be 
sufficiently less than VMO/MMO to ensure that 
likely speed variation during rough air encounters will not cause the 
overspeed warning to operate too frequently.
    (b) At altitudes where VMO is not limited by Mach 
number, in the absence of a rational investigation substantiating the 
use of other values, VRA must be less than VMO--
35 KTAS.
    (c) At altitudes where VMO is limited by Mach number, 
MRA may be chosen to provide an optimum margin between low 
and high speed buffet boundaries.

Appendix G to Part 25 [Removed and Reserved]

0
14. Remove and reserve appendix G to part 25.

    Issued under authority provided by 49 U.S.C. 106(f) and 44701(a) 
in Washington, DC, on November 14, 2014.
Michael P. Huerta,
Administrator.
[FR Doc. 2014-28938 Filed 12-10-14; 8:45 am]
BILLING CODE 4910-13-P