Harmonization of Airworthiness Standards-Miscellaneous Structures Requirements, 59423-59431 [2014-23373]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 79, Number 191 (Thursday, October 2, 2014)]
[Rules and Regulations]
[Pages 59423-59431]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-23373]



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Federal Register / Vol. 79, No. 191 / Thursday, October 2, 2014 / 
Rules and Regulations

[[Page 59423]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No.: FAA-2013-0109; Amdt. No. 25-139]
RIN 2120-AK13


Harmonization of Airworthiness Standards--Miscellaneous 
Structures Requirements

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

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 the European Aviation Safety Agency (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. This final rule revises the structural test requirements 
necessary when analysis has not been found reliable; clarifies the 
quality control, inspection, and testing requirements for critical and 
non-critical castings; adds control system requirements that consider 
structural deflection and vibration loads; expands the fuel tank 
structural and system requirements regarding emergency landing 
conditions and landing gear failure conditions; adds a requirement that 
engine mount failure due to overload must not cause hazardous fuel 
spillage; and revises the inertia forces requirements for cargo 
compartments by removing the exclusion of compartments located below or 
forward of all occupants in the airplane.

DATES: Effective December 1, 2014.

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, 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 Todd.Martin@faa.gov.
    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 Sean.Howe@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.'' 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 of transport category 
airplanes.

I. Overview of Final Rule

    The FAA is amending Title 14, Code of Federal Regulations (14 CFR) 
25.307(a), 25.621, 25.683, 25.721, 25.787(a), 25.963(d), and 25.994 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).
    1. Section 25.307(a), ``Proof of structure,'' currently requires 
structural strength testing, unless the applicant has demonstrated that 
analysis alone is reliable. Paragraph (a) is revised to clarify the 
load levels to which testing is required, when such testing is 
required.
    2. Section 25.621, ``Casting factors,'' is revised to clarify the 
quality control, inspection, and testing requirements for critical and 
non-critical castings.
    3. Section 25.683, ``Operation tests,'' is revised to add a 
requirement that--
     The control system must remain free from jamming, 
friction, disconnection, and permanent damage in the presence of 
structural deflection and
     Under vibration loads, no hazard may result from 
interference or contact of the control system with adjacent elements.
    4. Section 25.721, ``Landing Gear--General,'' is revised to--
     Expand the landing gear failure conditions to include side 
loads, in addition to up and aft loads, and expand this requirement to 
include nose landing gear in addition to the main landing gear,
     Specify that the wheels-up landing conditions are assumed 
to occur at a descent rate of 5 feet per second,
     Add a sliding-on-ground condition, and
     Require the engine mount be designed so that, when it 
fails due to overload, this failure does not cause the spillage of 
enough fuel to constitute a fire hazard.
    5. Section 25.787, ``Stowage compartments,'' is revised to expand 
the inertia forces requirements for cargo compartments by removing the 
exclusion of compartments located below or forward of all occupants in 
the airplane.
    6. Section 25.963, ``Fuel tanks: general,'' is revised to--
     Require that fuel tanks be designed so that no fuel is 
released in or near the fuselage, or near the engines, in quantities 
that would constitute a fire hazard in otherwise survivable emergency 
landing conditions,
     Define fuel tank pressure loads for fuel tanks located 
within and outside the fuselage pressure boundary and near the fuselage 
or near the engines, and

[[Page 59424]]

     Specify the wheels-up landing conditions and landing gear 
and engine mount failure conditions that must be considered when 
evaluating fuel tank structural integrity.
    7. Section 25.994, ``Fuel system components,'' is revised to 
specify the wheels-up landing conditions to be considered when 
evaluating fuel system components.

II. Background

A. Statement of the Problem

    Part 25 of 14 CFR 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. To 
resolve those differences, the FAA tasked ARAC through the Loads and 
Dynamics Harmonization Working Group (LDHWG) and the General Structures 
Harmonization Working Group (GSHWG) to review existing structures 
regulations and recommend changes that would eliminate differences 
between the U.S. and European airworthiness standards. The LDHWG and 
GSHWG 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 February 14, 2013, the FAA issued a Notice of Proposed 
Rulemaking (NPRM), Notice No. 25-137, Docket No. FAA-2013-0109, to 
amend Sec. Sec.  25.307(a), 25.621, 25.683, 25.721, 25.787(a), 
25.963(d), and 25.994. That NPRM was published in the Federal Register 
on March 1, 2013 (78 FR 13835). (The NPRM Notice No. was corrected to 
``13-03'' in the Federal Register on April 16, 2014 (79 FR 21413)). In 
the NPRM, the FAA proposed to (1) revise the structural test 
requirements necessary when analysis has not been found reliable; (2) 
clarify the quality control, inspection, and testing requirements for 
critical and non-critical castings; (3) add control system requirements 
that consider structural deflection and vibration loads; (4) expand the 
fuel tank structural and system requirements regarding emergency 
landing conditions and landing gear failure conditions; (5) add a 
requirement that engine mount failure due to overload must not cause 
hazardous fuel spillage; and (6) revise the inertial forces 
requirements for cargo compartments by removing the exclusion of 
compartments located below or forward of all occupants in the airplane. 
The FAA proposed these changes to eliminate regulatory differences 
between the airworthiness standards of the FAA and EASA. The NPRM 
comment period closed on May 30, 2013.

C. General Overview of Comments

    The FAA received 16 comments from 5 commenters. All commenters 
generally support the proposal, but they suggested changes discussed 
more fully below. The FAA received comments on each of the sections 
being changed, as follows:
     Section 25.307(a)--four comments
     Section 25.621--four comments
     Section 25.683--one comment
     Section 25.721--one comment
     Section 25.787(a)--two comments
     Section 25.963(d)--three comments
     Section 25.994--one comment

III. Discussion of Public Comments and Final Rule

A. Section 25.307, Proof of Structure

    In the NPRM, the FAA proposed revising paragraph (a) of Sec.  
25.307 to require that, when structural analysis has not been shown to 
be reliable, substantiating tests must be made to load levels that are 
sufficient to verify structural behavior up to limit and ultimate loads 
of Sec.  25.305.
    One commenter stated that Sec.  25.305 includes both limit and 
ultimate loads, so it is unclear which ``loads'' were intended by this 
change. More importantly, ``up to'' could mean any load level below 
limit or below ultimate and as such is indefinite. For example, an 
applicant could choose a load level of 10 percent of limit load and be 
in compliance with the proposed rule. The commenter proposed changing 
``up to loads specified in Sec.  25.305'' to ``at least limit load as 
specified in Sec.  25.305.''
    The FAA believes the wording proposed in the NPRM is correct, and 
no change is necessary. The phrase ``up to'' does not apply to the test 
load level; it applies to the design load level--the loads specified in 
Sec.  25.305, including ultimate loads--which must be verified. The 
intent of the rule is that, when analysis has not been shown to be 
reliable, tests must be conducted to ``sufficient'' load levels. 
Normally, testing to ultimate load levels is required, but when 
previous relevant test evidence can be used to support the analysis, a 
lower level of testing may be accepted. The rule allows this 
intermediate level of testing. Advisory Circular (AC) 25.307-1, ``Proof 
of Structure,'' which the FAA is issuing concurrently with the final 
rule, provides detailed guidance on means of compliance with the rule.
    Another commenter recommended changing the word ``reliable'' in the 
proposed rule to ``dependable and conservative.'' The term ``reliable'' 
has been in place since this rule was originally published in 1965. As 
stated in the NPRM, while the rule has changed, the rule intent remains 
the same. We believe ``reliable'' is appropriate and clear, and no 
change is necessary.
    The same commenter also recommended noting that, where justified, 
test load levels may be less than ultimate. We do not believe this 
change is necessary because it is already expressed in the rule that 
substantiating tests must be made to load levels that are sufficient to 
verify structural behavior up to loads specified in Sec.  25.305.
    The same commenter also recommended the FAA add further explanation 
about the absolute need to validate models and when lack of validation 
might be acceptable. We do not believe it is necessary to revise the 
rule to address validation, since that subject relates to the 
acceptability of an applicant's showing of compliance rather than to 
the airworthiness standard itself. This subject is thoroughly addressed 
in the accompanying AC 25.307-1. We have not revised the final rule in 
this regard.

B. Section 25.621, Casting Factors

    With this rulemaking, the FAA clarifies ``critical castings'' as 
each casting whose failure could preclude continued safe flight and 
landing of the airplane or could result in serious injury to occupants. 
One commenter agreed that improved foundry methods have resulted in 
higher quality castings but not to the point where a casting factor 
less than 1.25 is justified. The commenter recommended to either (1) 
eliminate the option for casting factors of 1.0 for critical castings, 
or (2) ensure that the characterization of material properties that are 
equivalent to those of wrought alloy products of similar composition 
includes the effect of defects in the static strength, fatigue, and 
damage tolerance requirements. The commenter provided the following 
examples of defects that could affect material properties: shell 
defects, hard-alpha contamination, shrink, porosity, weld defects, 
grain size, hot tears, incomplete densifications, and prior particle 
boundaries, among others.

[[Page 59425]]

    The FAA does not agree with the commenter's first recommendation to 
eliminate the option for using a casting factor of 1.0 for critical 
castings. The criteria specified in the final rule will ensure product 
quality that is sufficient to justify using a casting factor of 1.0. 
According to the rule, to qualify for a casting factor of 1.0, the 
applicant must demonstrate, through process qualification, proof of 
product, and process monitoring, that the casting has coefficients of 
variation of the material properties that are equivalent to those of 
wrought alloy products of similar composition. The rule requires 
process monitoring that includes testing of coupons and, on a sampling 
basis, coupons cut from critical areas of production castings. In 
addition, the applicant must inspect 100 percent of the casting surface 
of each casting, as well as structurally significant internal areas and 
areas where defects are likely to occur. The applicant must also test 
one casting to limit and ultimate loads. The purpose of the minimum 
casting factor of 1.25 in the current rule is to increase the strength 
of the casting to account for variability in the casting process. In 
the final rule, the additional process, inspection, and test 
requirements required to use a casting factor less than 1.25 ensure a 
more consistent product and maintain the same level of safety as the 
existing standards. AC 25.621-1, ``Casting Factors,'' provides detailed 
guidance on the premium casting process necessary to allow a casting 
factor of 1.0, and the FAA is issuing that AC concurrently with this 
final rule.
    The FAA partially agrees with the commenter's second 
recommendation, which is to ensure that the characterization of 
material properties that are equivalent to those of wrought alloy 
products of similar composition includes the effect of defects in the 
static strength, fatigue, and damage tolerance requirements. The rule 
requires that the characterization of material properties includes the 
effect of defects with regard to static strength. If any type of defect 
is discovered during process qualification, proof of product, or 
process monitoring, or by any inspection or static strength test, such 
that the coefficients of variation of the material properties are not 
equivalent to those of wrought alloy products of similar composition, 
then that casting would not qualify for a casting factor of 1.0. These 
defects include each of the examples identified by the commenter, as 
well as any other type of defect that could affect material properties. 
In addition, as noted previously, AC 25.621-1, which the FAA is issuing 
concurrently with the final rule, provides detailed guidance on the 
premium casting process necessary to allow a casting factor of 1.0. The 
AC includes reference to and addresses defects as proposed by the 
commenter.
    We do not, however, agree that the characterization of material 
properties to determine the appropriate casting factor should include 
the effect of defects on fatigue and damage tolerance properties. Since 
casting factors apply only to strength requirements, rather than 
fatigue and damage tolerance requirements, the comparison of cast 
material to wrought material should only be based on material strength 
properties, rather than fatigue and damage tolerance characteristics.
    Section 25.621(c)(2)(ii)(B) specifies a factor of 1.15 be applied 
to limit load test values to allow an applicant to use a casting factor 
of 1.25. Section 25.621(c)(3)(ii)(B) also specifies a factor of 1.15 be 
applied to limit load test values to allow a casting factor of 1.5. One 
commenter recommended that the 1.15 test factor in Sec.  
25.621(c)(3)(ii)(B) be scaled up by a factor of 1.2 (1.5/1.25), so as 
to align with the corresponding ultimate requirement. The 1.15 limit 
load test factor in Sec.  25.621(c)(3)(ii)(B) would then be 1.38 (i.e., 
1.5/1.25 x 1.15; 1.15 being required already in conjunction with the 
1.25 casting factor for ultimate).
    The FAA does not agree that for critical castings with a casting 
factor of 1.25 or 1.5, the limit load test factor should be linked to 
the ultimate load test factor. The ultimate and limit load tests have 
different purposes. The ultimate load test confirms ultimate load 
capability, while the limit load test confirms that no deformation will 
occur up to a much lower load level. Therefore, we see no reason to 
link the two test factors, and we believe the 1.15 factor specified in 
Sec.  25.621(c)(3)(ii)(B) is appropriate, as recommended by ARAC and as 
currently specified in EASA CS 25.621.
    The same commenter recommended modifying Sec.  25.621(c) by adding 
a reference to Sec.  25.305 for clarity--that each critical casting 
must have a factor associated with it for showing compliance with the 
strength and deformation requirement ``of Sec.  25.305.'' We agree and 
have revised the final rule as recommended.
    The same commenter noted that Sec.  25.621 only refers to static 
testing and does not include any requirements for fatigue testing. The 
commenter stated that critical castings should also comply with Sec.  
25.571 concerning fatigue and damage tolerance. The commenter 
recommended including information to remind manufacturers of this 
requirement. The FAA agrees with the commenter that Sec.  25.571 
applies to critical castings. We believe the current wording in Sec.  
25.571 and the new wording in Sec.  25.621 is sufficiently clear on 
this point, and no changes to these requirements are necessary.
    No other public comments were received on Sec.  25.621. However, 
after further FAA review, we revised the rule in several places to 
specify ``visual inspection and liquid penetrant or equivalent 
inspection methods.'' This change is to clarify ``equivalent inspection 
methods'' refers to the liquid penetrant inspection, and not the visual 
inspection. Although there is some textual difference between this and 
CS 25.621, there is no substantive difference between the two 
harmonized rules.

C. Section 25.683, Operation Tests

    A commenter noted that the control systems to which Sec.  25.683(b) 
applies are those control systems that obtain the pitch, roll, and yaw 
limit maneuver loads of the airplane structure. For example, an 
applicant must take into account the elevator, rudder, and aileron 
because these control surfaces obtain the referenced maneuver loads, 
while high lift systems do not need to be considered under Sec.  
25.683(b). The commenter suggested that we clarify this in the preamble 
to the final rule. The FAA agrees and hereby clarifies that Sec.  
25.683 only applies to those control systems that are loaded to obtain 
the specified maneuver loads. No change to the final rule text is 
necessary.
    No other public comments were received on Sec.  25.683. We would 
like to explain what is meant by ``where necessary'' as used in Sec.  
25.683(b). The rule states: ``It must be shown by analysis and, where 
necessary, by tests, that in the presence of deflections of the 
airplane structure,'' the control system operates without jamming, 
excessive friction, or permanent damage. The FAA may accept analysis 
alone to comply with this requirement. However, the FAA or the 
applicant may determine that, in certain cases, some testing is 
necessary to verify the analysis. For example, some testing may be 
necessary if the structure or control system is significantly more 
complex than a previous design, or if the analysis shows areas where 
the control system could be susceptible to jamming, friction, 
disconnection or damage. Testing may include component testing or full-
scale tests.

[[Page 59426]]

D. Section 25.721, Landing Gear--General

    A commenter proposed to add a paragraph (d) to Sec.  25.721 to 
state that the conditions in paragraphs (a) through (c) must be 
considered regardless of the corresponding probabilities. The FAA does 
not believe this addition is necessary. The various failure conditions 
in the rule are stated directly, and the FAA intended no implication 
that the probability of these failure conditions may be taken into 
account. However, because the FAA proposed that a failure mode not be 
likely to cause the spillage of enough fuel to constitute a fire 
hazard, the proposal may have implied that an applicant should take 
probability into account to determine whether the failure conditions 
would lead to fuel spillage. The FAA did not intend this. Probability 
should not be taken into account to determine whether the failure mode 
will lead to fuel spillage.
    No other public comments were received on Sec.  25.721. However, 
after further FAA review, we revised Sec.  25.721(b) to clarify its 
intent. We removed the phrase ``as separate conditions,'' which was 
proposed in Sec.  25.721(b)(1)(i) and (b)(2)(i), because we believe 
that phrase is confusing. In Sec.  25.721(b)(1)(ii) and (b)(2)(ii), we 
also changed the proposed phrase ``any other combination of landing 
gear legs not extended'' to ``any one or more landing gear legs not 
extended'' which is the same phrase used in Sec.  25.721(b) at 
Amendment 25-32. We made this change to ensure that applicants are 
required to address every possible combination of landing gear legs not 
extended, including single landing gear legs not extended. This is 
consistent with the way EASA has applied its rule.
    Both Sec. Sec.  25.721(b) and 25.994 final rules use the phrase 
``wheels-up landing.'' This phrase has been used in Sec.  25.994 since 
that rule was adopted at Amendment 25-23. A ``wheels-up landing'' 
includes every possible combination of landing gear legs not extended, 
including single landing gear legs not extended, and all gears fully 
retracted.

E. Section 25.787, Stowage Compartments

    To date, Sec.  25.787(a) has required that cargo compartments be 
designed to the emergency landing conditions of Sec.  25.561(b), but 
excluded compartments located below or forward of all occupants in the 
airplane. The FAA now revises Sec.  25.787(a) to include compartments 
located below or forward of all occupants in the airplane. This change 
would ensure that, in these compartments, inertia forces in the up and 
aft direction will not injure passengers, and inertia forces in any 
direction will not cause penetration of fuel tanks or lines, or cause 
other hazards.
    A commenter recommended revising the text to clarify that only 
those specific emergency landing conditions that would result in one of 
the three listed effects need to be considered. The FAA agrees, and we 
have revised the text to clarify this intent.
    The same commenter suggested that fires only need to be protected 
against if they can result in injury to occupants, and the rule text 
should be revised to clarify that intent. The FAA does not agree that 
fires only need to be protected against if they can result in injury to 
occupants. The FAA believes that the wording proposed in the NPRM is 
correct, and no change is necessary. The requirement intends protection 
against any fire or explosion on the airplane. Although the FAA agrees 
the objective of the rule is to prevent injuries to occupants, the FAA 
considers any fuel tank fire or explosion in an otherwise survivable 
landing as potentially injury-causing.

F. Section 25.963, Fuel Tanks: General

    One commenter suggested that exactly the same wording be used in 
Sec.  25.963(d) and CS 25.963(d). EASA CS 25.963(d) requires that no 
fuel be released in quantities ``sufficient to start a serious fire'' 
in otherwise survivable emergency landing conditions. Proposed Sec.  
25.963(d) would have required that no fuel be released in quantities 
``that would constitute a fire hazard.'' The FAA stated in the NPRM 
that the two phrases have the same meaning, and that proposed Sec.  
25.963(d) was more consistent with the wording of the other related 
sections.
    The FAA is adopting the wording proposed in the NPRM as more 
appropriate. As noted in the NPRM, the two phrases have the same 
meaning, and the latter phrase is consistent with the wording in CS 
25.721/Sec.  25.721, CS 25.963(d)(4)/Sec.  25.963(d)(4), and CS 25.994/
Sec.  25.994. In addition, EASA agrees with and supports the NPRM. In 
recent special conditions, the FAA has defined a hazardous fuel leak as 
``a running leak, a dripping leak, or a leak that, 15 minutes after 
wiping dry, results in a wetted airplane surface exceeding 6 inches in 
length or diameter.'' We regard this as an appropriate definition of 
the amount of fuel that would ``constitute a fire hazard'' as specified 
in Sec. Sec.  25.721, 25.963, and 25.994.
    Another commenter suggested modifying Sec.  25.963(d)(5) to 
reference landing gear before engine mounts in the rule text, since 
these are referred to respectively in Sec.  25.721(a) and (c). The FAA 
agrees and the recommended change has been made.
    EASA CS 25.963(e)(2) provides the fire protection criteria for fuel 
tank access covers. A commenter recommended that Sec.  25.963(e)(2) be 
revised to match CS 25.963(e)(2), which the commenter believes is 
clearer. The FAA notes that this paragraph was not addressed in the 
NPRM and so will not be addressed in this final rule. The FAA might 
consider harmonizing this paragraph in the future.
    No other public comments were received on Sec.  25.963. However, 
after further FAA review, we determined that further explanation of the 
various requirements in Sec.  25.963(d) would be beneficial. Section 
25.963(d), as revised by Amendment 25-**, requires that ``Fuel tanks 
must, so far as it is practicable, be designed, located, and installed 
so that no fuel is released in or near the fuselage, or near the 
engines, in quantities that would constitute a fire hazard in otherwise 
survivable emergency landing conditions. . . .'' In addition to this 
primary requirement, Sec.  25.963(d)(1) through (d)(5) provide minimum 
quantitative criteria. Survivable landing conditions may occur that 
exceed, or are not captured by, the conditions specified in Sec.  
25.963(d)(1) through (d)(5). Therefore, to meet the introductory 
requirement in Sec.  25.963(d), every practicable consideration should 
be made to ensure protection of fuel tanks in more severe crash 
conditions, especially tanks located in the fuselage below the main 
cabin floor.
    The fuel tank pressure loads specified in Sec.  25.963(d) vary 
depending on whether the fuel tank is within or outside the pressure 
boundary. For certification of unpressurized airplanes, all fuel tanks 
should be considered to be ``within'' the fuselage pressure boundary, 
unless a fire resistant barrier exists between the fuel tank and the 
occupied compartments of the airplane.
    Finally, the FAA notes that, for future rulemaking, we plan to 
consider specific crashworthiness requirements that would exceed the 
quantitative criteria specified in Sec. Sec.  25.561, 25.721, and 
25.963. Also, the FAA has recently applied special conditions on 
certain airplanes that require a crashworthiness evaluation at descent 
rates up to 30 feet per second.

[[Page 59427]]

G. Section 25.994, Fuel System Components

    To date, Sec.  25.994 has required that fuel system components in 
an engine nacelle or in the fuselage be protected from damage that 
could result in spillage of enough fuel to constitute a fire hazard as 
a result of a wheels-up landing on a paved runway. We proposed to 
revise Sec.  25.994 to specify that the wheels-up landing conditions 
that must be considered are those prescribed in Sec.  25.721(b).
    A commenter proposed two changes to what the FAA proposed: (1) Add 
a reference to Sec.  25.721(c), and (2) change the order in which the 
nacelles and the fuselage are referenced, based on the order the 
fuselage and nacelle are addressed in Sec.  25.721. We do not agree 
with the proposed changes. Adding a reference to Sec.  25.721(c) would 
not be correct because wheels-up landing conditions are only listed in 
Sec.  25.721(b). Since Sec.  25.721(c) is not referenced in Sec.  
25.994, and since Sec.  25.721(b) does not refer to the fuselage or 
nacelles, there is no reason to change the order in which the fuselage 
and nacelles are specified in Sec.  25.994.

H. Advisory Material

    On March 13, 2013, the FAA published and solicited public comments 
on three proposed ACs that describe acceptable means for showing 
compliance with the proposed regulations in the NPRM. The comment 
period for the proposed ACs closed on June 14, 2013. Concurrently with 
this final rule, the FAA is issuing the following new ACs to provide 
guidance material for the regulations adopted by this amendment:
     AC 25-30, ``Fuel Tank Strength in Emergency Landing 
Conditions.'' (AC 25-30 would provide guidance for the fuel tank 
structural integrity requirements of Sec. Sec.  25.561, 25.721, and 
25.963.)
     AC 25.307-1, ``Proof of Structure.''
     AC 25.621-1, ``Casting Factors.''

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, 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 would eliminate regulatory 
differences between the airworthiness standards of the FAA and the 
EASA. This final rule does not add new requirements as U.S. 
manufacturers currently meet EASA requirements. Meeting two sets of 
certification requirements imposes greater costs for 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 
the Final Rule.'' This action harmonizes part 25 requirements with the 
corresponding requirements in EASA CS-25 Book 1.
    In order to sell their aircraft in Europe, all manufacturers of 
transport category airplanes, certificated under part 25 must be in 
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 the same EASA requirements, 
manufacturers will incur minimal or no additional cost resulting from 
this final rule. Therefore, the FAA estimates that there are no 
additional costs associated with this final rule.
    In fact, manufacturers could receive cost savings because they will 
not have to build and certificate transport category airplanes to two 
different authorities' certification specifications and rules. Further, 
harmonization of these airworthiness standards, specifically Sec.  
25.621 may benefit manufacturers by providing another option in 
developing aircraft structures. The final rule permits use of a lower 
casting factor for critical castings, provided that tight controls are 
established for the casting process, inspection, and testing, which 
lead to cost savings in terms of aircraft weight. These additional 
controls are expected to at least maintain an equivalent level of 
safety as provided by existing regulations for casting factors.
    The FAA has not attempted to quantify the cost savings that may 
accrue from this final rule, beyond noting that, while they may be 
minimal, they contribute overall to a potential harmonization savings. 
The agency concludes that because the compliance cost for this final 
rule is minimal and there may be harmonization cost savings, further 
analysis is not required.
    During the public comment period, the Agency received 16 comments 
from 5 commenters. There were no comments regarding costs to this final 
rule; however, one commenter raised concern for safety in Sec.  25.621. 
Details of this comment and the FAA's response can be found in the 
``General Overview of Comments'' section. These harmonization efforts 
ensure that the current level of safety in transport category airplanes 
is maintained while encouraging the use of modern casting process 
technology.
    The agency concludes that the changes would eliminate regulatory 
differences between the airworthiness standards of the FAA and EASA 
resulting in potential cost savings and maintaining current levels of 
safety. 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 59428]]

B. Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (Pub. L. 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.
    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. The net effect of this final rule is minimum 
regulatory cost relief, as the rule would adopt EASA requirements that 
the industry already meets. Further, all United States transport 
category aircraft manufacturers exceed the Small Business 
Administration small-entity criteria of 1,500 employees. The Agency 
received no comments regarding the Regulatory Flexibility Act during 
the public comment period.
    If an agency determines that a rulemaking will not result in a 
significant economic impact on a substantial number of small entities, 
the head of the agency may so certify under section 605(b) of the RFA. 
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 final rule uses 
European standards as the basis for United States regulation.

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 
(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 would be 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 59429]]

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 (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.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 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 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 
https://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 chapter I 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.  25.307 by revising paragraph (a) to read as follows:


Sec.  25.307  Proof of structure.

    (a) Compliance with the strength and deformation requirements of 
this subpart must be shown for each critical loading condition. 
Structural analysis may be used only if the structure conforms to that 
for which experience has shown this method to be reliable. In other 
cases, substantiating tests must be made to load levels that are 
sufficient to verify structural behavior up to loads specified in Sec.  
25.305.
* * * * *

0
3. Amend Sec.  25.621 by revising paragraphs (a), (c), and (d) to read 
as follows:


Sec.  25.621  Casting factors.

    (a) General. For castings used in structural applications, the 
factors, tests, and inspections specified in paragraphs (b) through (d) 
of this section must be applied in addition to those necessary to 
establish foundry quality control. The inspections must meet approved 
specifications. Paragraphs (c) and (d) of this section apply to any 
structural castings, except castings that are pressure tested as parts 
of hydraulic or other fluid systems and do not support structural 
loads.
* * * * *
    (c) Critical castings. Each casting whose failure could preclude 
continued safe flight and landing of the airplane or could result in 
serious injury to occupants is a critical casting. Each critical 
casting must have a factor associated with it for showing compliance 
with strength and deformation requirements of Sec.  25.305, and must 
comply with the following criteria associated with that factor:
    (1) A casting factor of 1.0 or greater may be used, provided that--
    (i) It is demonstrated, in the form of process qualification, proof 
of product, and process monitoring that, for each casting design and 
part number, the castings produced by each foundry and process 
combination have coefficients of variation of the material properties 
that are equivalent to those of wrought alloy products of similar 
composition. Process monitoring must include testing of coupons cut 
from the prolongations of each casting (or each set of castings, if 
produced from a single pour into a single mold in a runner system) and, 
on a sampling basis, coupons cut from critical areas of production 
castings. The acceptance criteria for the process monitoring 
inspections and tests must be established and included in the process 
specifications to ensure the properties of the production castings are 
controlled to within levels used in design.
    (ii) Each casting receives:
    (A) Inspection of 100 percent of its surface, using visual 
inspection and liquid penetrant or equivalent inspection methods; and
    (B) Inspection of structurally significant internal areas and areas 
where defects are likely to occur, using radiographic or equivalent 
inspection methods.
    (iii) One casting undergoes a static test and is shown to meet the 
strength and deformation requirements of Sec.  25.305(a) and (b).
    (2) A casting factor of 1.25 or greater may be used, provided 
that--
    (i) Each casting receives:
    (A) Inspection of 100 percent of its surface, using visual 
inspection and liquid penetrant or equivalent inspection methods; and
    (B) Inspection of structurally significant internal areas and areas 
where defects are likely to occur, using radiographic or equivalent 
inspection methods.
    (ii) Three castings undergo static tests and are shown to meet:
    (A) The strength requirements of Sec.  25.305(b) at an ultimate 
load corresponding to a casting factor of 1.25; and
    (B) The deformation requirements of Sec.  25.305(a) at a load of 
1.15 times the limit load.
    (3) A casting factor of 1.50 or greater may be used, provided 
that--
    (i) Each casting receives:
    (A) Inspection of 100 percent of its surface, using visual 
inspection and liquid penetrant or equivalent inspection methods; and
    (B) Inspection of structurally significant internal areas and areas 
where defects are likely to occur, using radiographic or equivalent 
inspection methods.
    (ii) One casting undergoes a static test and is shown to meet:
    (A) The strength requirements of Sec.  25.305(b) at an ultimate 
load corresponding to a casting factor of 1.50; and
    (B) The deformation requirements of Sec.  25.305(a) at a load of 
1.15 times the limit load.
    (d) Non-critical castings. For each casting other than critical 
castings, as

[[Page 59430]]

specified in paragraph (c) of this section, the following apply:
    (1) A casting factor of 1.0 or greater may be used, provided that 
the requirements of (c)(1) of this section are met, or all of the 
following conditions are met:
    (i) Castings are manufactured to approved specifications that 
specify the minimum mechanical properties of the material in the 
casting and provides for demonstration of these properties by testing 
of coupons cut from the castings on a sampling basis.
    (ii) Each casting receives:
    (A) Inspection of 100 percent of its surface, using visual 
inspection and liquid penetrant or equivalent inspection methods; and
    (B) Inspection of structurally significant internal areas and areas 
where defects are likely to occur, using radiographic or equivalent 
inspection methods.
    (iii) Three sample castings undergo static tests and are shown to 
meet the strength and deformation requirements of Sec.  25.305(a) and 
(b).
    (2) A casting factor of 1.25 or greater may be used, provided that 
each casting receives:
    (i) Inspection of 100 percent of its surface, using visual 
inspection and liquid penetrant or equivalent inspection methods; and
    (ii) Inspection of structurally significant internal areas and 
areas where defects are likely to occur, using radiographic or 
equivalent inspection methods.
    (3) A casting factor of 1.5 or greater may be used, provided that 
each casting receives inspection of 100 percent of its surface using 
visual inspection and liquid penetrant or equivalent inspection 
methods.
    (4) A casting factor of 2.0 or greater may be used, provided that 
each casting receives inspection of 100 percent of its surface using 
visual inspection methods.
    (5) The number of castings per production batch to be inspected by 
non-visual methods in accordance with paragraphs (d)(2) and (3) of this 
section may be reduced when an approved quality control procedure is 
established.

0
4. Revise Sec.  25.683 to read as follows:


Sec.  25.683  Operation tests.

    (a) It must be shown by operation tests that when portions of the 
control system subject to pilot effort loads are loaded to 80 percent 
of the limit load specified for the system and the powered portions of 
the control system are loaded to the maximum load expected in normal 
operation, the system is free from--
    (1) Jamming;
    (2) Excessive friction; and
    (3) Excessive deflection.
    (b) It must be shown by analysis and, where necessary, by tests, 
that in the presence of deflections of the airplane structure due to 
the separate application of pitch, roll, and yaw limit maneuver loads, 
the control system, when loaded to obtain these limit loads and 
operated within its operational range of deflections, can be exercised 
about all control axes and remain free from--
    (1) Jamming;
    (2) Excessive friction;
    (3) Disconnection; and
    (4) Any form of permanent damage.
    (c) It must be shown that under vibration loads in the normal 
flight and ground operating conditions, no hazard can result from 
interference or contact with adjacent elements.

0
5. Revise Sec.  25.721 to read as follows:


Sec.  25.721  General.

    (a) The landing gear system must be designed so that when it fails 
due to overloads during takeoff and landing, the failure mode is not 
likely to cause spillage of enough fuel to constitute a fire hazard. 
The overloads must be assumed to act in the upward and aft directions 
in combination with side loads acting inboard and outboard. In the 
absence of a more rational analysis, the side loads must be assumed to 
be up to 20 percent of the vertical load or 20 percent of the drag 
load, whichever is greater.
    (b) The airplane must be designed to avoid any rupture leading to 
the spillage of enough fuel to constitute a fire hazard as a result of 
a wheels-up landing on a paved runway, under the following minor crash 
landing conditions:
    (1) Impact at 5 feet-per-second vertical velocity, with the 
airplane under control, at Maximum Design Landing Weight--
    (i) With the landing gear fully retracted; and
    (ii) With any one or more landing gear legs not extended.
    (2) Sliding on the ground, with--
    (i) The landing gear fully retracted and with up to a 20[deg] yaw 
angle; and
    (ii) Any one or more landing gear legs not extended and with 0[deg] 
yaw angle.
    (c) For configurations where the engine nacelle is likely to come 
into contact with the ground, the engine pylon or engine mounting must 
be designed so that when it fails due to overloads (assuming the 
overloads to act predominantly in the upward direction and separately, 
predominantly in the aft direction), the failure mode is not likely to 
cause the spillage of enough fuel to constitute a fire hazard.

0
6. Amend Sec.  25.787 by revising paragraph (a) to read as follows:


Sec.  25.787  Stowage compartments.

    (a) Each compartment for the stowage of cargo, baggage, carry-on 
articles, and equipment (such as life rafts), and any other stowage 
compartment, must be designed for its placarded maximum weight of 
contents and for the critical load distribution at the appropriate 
maximum load factors corresponding to the specified flight and ground 
load conditions, and to those emergency landing conditions of Sec.  
25.561(b)(3) for which the breaking loose of the contents of such 
compartments in the specified direction could--
    (1) Cause direct injury to occupants;
    (2) Penetrate fuel tanks or lines or cause fire or explosion hazard 
by damage to adjacent systems; or
    (3) Nullify any of the escape facilities provided for use after an 
emergency landing.

If the airplane has a passenger-seating configuration, excluding pilot 
seats, of 10 seats or more, each stowage compartment in the passenger 
cabin, except for under seat and overhead compartments for passenger 
convenience, must be completely enclosed.
* * * * *

0
7. Amend Sec.  25.963 by revising paragraph (d) to read as follows:


Sec.  25.963  Fuel tanks: general.

* * * * *
    (d) Fuel tanks must, so far as it is practicable, be designed, 
located, and installed so that no fuel is released in or near the 
fuselage, or near the engines, in quantities that would constitute a 
fire hazard in otherwise survivable emergency landing conditions, and--
    (1) Fuel tanks must be able to resist rupture and retain fuel under 
ultimate hydrostatic design conditions in which the pressure P within 
the tank varies in accordance with the formula:

P = K[rho]gL

Where--

P = fuel pressure at each point within the tank
[rho] = typical fuel density
g = acceleration due to gravity
L = a reference distance between the point of pressure and the tank 
farthest boundary in the direction of loading
K = 4.5 for the forward loading condition for those parts of fuel 
tanks outside the fuselage pressure boundary
K = 9 for the forward loading condition for those parts of fuel 
tanks within the fuselage pressure boundary, or that form part of 
the fuselage pressure boundary
K = 1.5 for the aft loading condition
K = 3.0 for the inboard and outboard loading conditions for those 
parts of fuel tanks

[[Page 59431]]

within the fuselage pressure boundary, or that form part of the 
fuselage pressure boundary
K = 1.5 for the inboard and outboard loading conditions for those 
parts of fuel tanks outside the fuselage pressure boundary
K = 6 for the downward loading condition
K = 3 for the upward loading condition

    (2) For those parts of wing fuel tanks near the fuselage or near 
the engines, the greater of the fuel pressures resulting from 
paragraphs (d)(2)(i) or (d)(2)(ii) of this section must be used:
    (i) The fuel pressures resulting from paragraph (d)(1) of this 
section, and
    (ii) The lesser of the two following conditions:
    (A) Fuel pressures resulting from the accelerations specified in 
Sec.  25.561(b)(3) considering the fuel tank full of fuel at maximum 
fuel density. Fuel pressures based on the 9.0g forward acceleration may 
be calculated using the fuel static head equal to the streamwise local 
chord of the tank. For inboard and outboard conditions, an acceleration 
of 1.5g may be used in lieu of 3.0g as specified in Sec.  25.561(b)(3).
    (B) Fuel pressures resulting from the accelerations as specified in 
Sec.  25.561(b)(3) considering a fuel volume beyond 85 percent of the 
maximum permissible volume in each tank using the static head 
associated with the 85 percent fuel level. A typical density of the 
appropriate fuel may be used. For inboard and outboard conditions, an 
acceleration of 1.5g may be used in lieu of 3.0g as specified in Sec.  
25.561(b)(3).
    (3) Fuel tank internal barriers and baffles may be considered as 
solid boundaries if shown to be effective in limiting fuel flow.
    (4) For each fuel tank and surrounding airframe structure, the 
effects of crushing and scraping actions with the ground must not cause 
the spillage of enough fuel, or generate temperatures that would 
constitute a fire hazard under the conditions specified in Sec.  
25.721(b).
    (5) Fuel tank installations must be such that the tanks will not 
rupture as a result of the landing gear or an engine pylon or engine 
mount tearing away as specified in Sec.  25.721(a) and (c).
* * * * *

0
8. Revise Sec.  25.994 to read as follows:


Sec.  25.994  Fuel system components.

    Fuel system components in an engine nacelle or in the fuselage must 
be protected from damage that could result in spillage of enough fuel 
to constitute a fire hazard as a result of a wheels-up landing on a 
paved runway under each of the conditions prescribed in Sec.  
25.721(b).

    Issued under authority provided by 49 U.S.C. 106(f), 44701(a), 
and 44703 in Washington, DC, on September 24, 2014.
Michael P. Huerta,
Administrator.
[FR Doc. 2014-23373 Filed 10-1-14; 8:45 am]
BILLING CODE 4910-13-P