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