[Federal Register Volume 64, Number 117 (Friday, June 18, 1999)]
[Proposed Rules]
[Pages 32978-32981]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-15381]



[[Page 32977]]

_______________________________________________________________________

Part V





Department of Transportation





_______________________________________________________________________



Federal Aviation Administration



_______________________________________________________________________



14 CFR Part 25



Revised Landing Gear Shock Absorption Test Requirements and Proposed 
Advisory Circular 25.723-1, Shock Absorption Test; Proposed Rule and 
Notice

  Federal Register / Vol. 64, No. 117 / Friday, June 18, 1999 / 
Proposed Rules  

[[Page 32978]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-1999-5835; Notice No. 99-08]
RIN 2120-AG72


Revised Landing Gear Shock Absorption Test Requirements

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: This document proposes to revise the landing gear shock 
absorption test requirements for transport category airplanes by 
incorporating changes developed in cooperation with the Joint Aviation 
Authorities (JAA) of Europe and the U.S. and European aviation industry 
through the Aviation Rulemaking Advisory Committee (ARAC). This action 
is necessary because the increasing complexity of landing gear shock 
absorption systems and the improvements in other requirements 
concerning landing loads have rendered the current requirements 
inconsistent and outdated. In addition, differences between the current 
United States and European requirements impose unnecessary costs on 
airplane manufacturers. These proposals are intended to update the 
landing gear requirements to be consistent with other requirements, to 
reflect modern technology, and to achieve common requirements and 
language between the Federal Aviation Regulations and the European 
Joint Aviation Requirements (JAR) without reducing the level of safety 
provided by the regulations and industry practices.

DATES: Comments must be received on or before October 18, 1999.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
U.S. Department of Transportation, Dockets, Docket No. FAA-1999-5835, 
400 Seventh Street SW., Room Plaza 401, Washington, D.C. 20590. 
Comments may also be submitted electronically to the following address: 
[email protected]. Comments may be examined in Room Place 401 between 
10 a.m. and 5 p.m., weekdays, except Federal holidays. In addition, the 
FAA is maintaining an information docket of comments in the Transport 
Airplane Directorate (ANM-100), FAA, 1601 Lind Avenue SW., Renton, WA 
98055-4056. Comments in the information docket may be examined 
weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: James Haynes, Airframe/Cabin Safety 
Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification 
Service, FAA, 1601 Lind Avenue, SW., Renton, WA 98055-4056; telephone 
(425) 227-2131.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in this proposed 
rulemaking by submitting such written data, views, or arguments as they 
may desire. Comments relating to any environmental, energy, or economic 
impact that might result from adopting the proposals contained in this 
action are invited. Substantive comments should be accompanied by cost 
estimates. Commenters should identify the regulatory docket or notice 
number and submit comments in duplicate to the Docket address above. 
All comments received on or before the closing date for comments will 
be considered by the Administrator before taking action on this 
proposed rulemaking. Late filed comments will be considered to the 
extent practicable. The proposals contained in this action may be 
changed in light of comments received. All comments received will be 
available in the Docket, both before and after the comment period 
closing date, for examination by interested persons. A report 
summarizing each substantive public contact with FAA personnel 
concerning this rulemaking will be filed in the docket. Persons wishing 
the FAA to acknowledge receipt of their comments must submit with those 
comments a self-addressed, stamped postcard on which the following 
statement is made: ``Comments to Docket No. FAA-1999-5835.'' The 
postcard will be date/time stamped and returned to the commenter.

Availability of NPRM

    An electronic copy of this document may be downloaded using a modem 
and suitable communications software from the FAA regulations section 
of the Fedworld electronic bulletin board service (telephone: 703-321-
3339), the Government Printing Office's electronic bulletin board 
service (telephone: 202-512-1661), or the FAA's Aviation Rulemaking 
Advisory Committee Bulletin Board service (telephone: 800-322-2722 or 
202-267-5948).
    Internet users may reach the FAA's web page at http://www.faa.gov/
avr/arm/nprm.htm or the Government Printing Office's web page at http:/
/www.access.gpo.gov/nara for access to recently published rulemaking 
documents.
    Any person may obtain a copy of this document by submitting a 
request to the Federal Aviation Administration, Office of Rulemaking, 
ARM-1, 800 Independence Avenue SW., Washington, DC 20591; or by calling 
(202) 267-9680. Communications must identify the docket or notice 
number of this NPRM. Persons interested in being placed on a mailing 
list for future rulemaking documents should also request a copy of 
Advisory Circular No. 11-2A, Notice of Proposed Rulemaking Distribution 
System, which describes the application procedure.

Background

    The manufacturing, marketing and certification of transport 
airplanes is increasingly an international endeavor. In order for U.S. 
manufacturers to export transport airplanes to other countries the 
airplane must be designed to comply, not only with the U.S. 
airworthiness requirements for transport airplanes (14 CFR part 25), 
but also with the transport airworthiness requirements of the countries 
to which the airplane is to be exported.
    The European countries have developed a common airworthiness code 
for transport airplanes that is administered by the Joint Aviation 
Authorities (JAA) of Europe. This code is the result of a European 
effort to harmonize the various airworthiness codes of the European 
countries and is called the Joint Aviation Requirements (JAR)-25. It 
was developed in a format similar to part 25. Many other countries have 
airworthiness codes that are aligned closely to part 25 or to JAR-25, 
or they use these codes directly for their own certification purposes.
    The Aviation Rulemaking Advisory Committee (ARAC) was established 
by the FAA on February 15, 1991, with the purpose of providing 
information, advice, and recommendations to be considered in rulemaking 
activities. By notice in the Federal Register (59 FR 30081, June 10, 
1994), the FAA assigned several new tasks to an ARAC working group of 
industry and government structural loads specialists from Europe, the 
United States, and Canada. Task 6 of the working group charter 
concerned the shock absorption test requirements for landing gear. The 
ARAC working group has completed its work for this task and the ARAC 
has made recommendations to the FAA by letter dated October 29, 1997.
    Although the requirements for landing gear shock absorption tests 
are essentially the same between the Federal Aviation Regulations and 
JAR, the requirements do not address the capabilities of modern 
technology and

[[Page 32979]]

do not take into account other related changes in the requirements for 
landing gear load conditions that have already been incorporated into 
other sections of the Federal Aviation Regulations. When the landing 
loads requirements for transport airplanes were originally developed, 
they required the landing load factors to be determined and applied to 
the airplane. The airplane was treated as a rigid body and the landing 
loads were applied to this rigid representation of the airplane for the 
purpose of structural analysis. For the early landing gear systems, 
analysis alone was considered sufficient for determining the landing 
load factor that would be applied to the rigid airplane. It was only 
necessary to determine the landing load factor (by analysis or tests) 
and this load factor would then be used to design and substantiate the 
airplane for the landing load conditions.
    The development of more complex landing gear systems, for which 
analysis alone was unreliable, led to the adoption of a requirement to 
verify the landing load factor by actual shock absorption tests. This 
requirement was added to the Civil Air Regulations (CAR) part 4b, which 
was the predecessor to part 25. These shock absorption tests were 
allowed by Sec. 4b.200 of the CAR to be free drop tests in which the 
gear alone, could be dropped in free fall to impact the ground. In 
these tests, mass is added to represent the proportion of the airplane 
weight on the landing gear unit, and the mass may be reduced to account 
for the effects of airplane lift acting during the landing impact. 
Later, the corresponding requirement in Sec. 25.723(a), was modified to 
allow the substantiation of some changes to the landing gear shock 
absorption systems by analysis alone without verification by tests.
    Part 25 currently requires the landing loads to be determined by 
accounting for the dynamic flexible airplane. In addition, the landing 
gear shock absorption systems have become even more sophisticated. At 
the same time, the ability to develop highly sophisticated computer 
models of landing gear and airplane structures has also improved. In 
order to determine the airplane loads from the landing load conditions, 
it is no longer sufficient to determine just the load factor from a 
drop test of a landing gear unit. A comprehensive analysis of the 
combined dynamic systems for the landing gear and airplane are 
essential in order to determine the structural design loads for the 
airplane. In developing this dynamic model, it is necessary to provide 
an accurate representation of all the landing gear dynamic 
characteristics. This includes the energy absorption characteristics 
and the time histories of force and displacement during a landing 
impact. The current Secs. 25.473(d) and 25.723(a) for shock absorption 
tests require just the determination of the limit landing load factor 
from the drop test.

Discussion

    The proposed revisions to Sec. Sec. 25.473(d) and 25.723(a) would 
provide for the new objective of the landing gear energy absorption 
tests which would be to validate the landing gear dynamic 
characteristics rather than to directly determine landing gear load 
factors. These revisions would require that these characteristics be 
substantiated over the range of landing conditions and airplane 
configurations expected in service. The manufacturer would be expected 
to substantiate the landing gear dynamic characteristics over the full 
range of weight conditions and configurations. As a minimum, the energy 
absorption characteristics would be confirmed by an energy absorption 
test at the weight condition for landing (maximum takeoff weight or 
maximum landing weight) which provides the maximum impact energy. This 
is in contrast to the current Sec. Sec. 25.473(d) and 25.723(a) which 
specifically require energy absorption tests at both the maximum 
landing weight condition and the maximum takeoff weight condition. The 
proposed rule would continue to provide for the substantiation of minor 
changes by analyses. To provide guidance in complying with the new 
proposed rule, a new advisory circular, AC 25.723-1, Shock Absorption 
Tests, is proposed.
    The proposals for the revised Sec. Sec. 25.473(d) and 25.723(a) 
take into account the potential for sophisticated computer simulations 
that accurately represent the dynamic characteristics. These are also 
consistent with improvements in the landing load requirements that 
necessitate an accurate representation of the landing gear shock 
absorption characteristics. These proposals also provide more 
flexibility for the airplane manufacturer to determine the range of 
conditions and configurations over which to validate the analytical 
model for the landing conditions. The extent to which this analytical 
model could be extrapolated to include future design changes would 
depend on the range of conditions and configurations originally 
selected by the manufacturer for validation of the model.
    The current Sec. Sec. 25.725 and 25.727 are proposed to be deleted 
as regulatory requirements and would be set forth in the new proposed 
AC 25.723-1. These criteria would be modified to reflect the advisory 
nature of the material as well as the revised objective of determining 
landing gear dynamic characteristics instead of landing gear limit 
inertia load factors. For the most part, these rules currently provide 
acceptable means of conducting energy absorption tests by means of a 
drop test. Section 25.725 provides an acceptable means of conducting a 
limit drop test for compliance with Sec. 25.723(a), and Sec. 25.727 
provides an acceptable means of conducting a reserve energy drop test 
in compliance with Sec. 25.723(b). Most of the guidance is limited to a 
``free'' drop test in which a reduced effective weight is used to 
represent lift during the landing impact. The only item in these two 
sections that is considered to be regulatory in nature is the current 
Sec. 25.725(c) concerning the attitude of the landing gear and the 
representation of drag loads during the tests. Therefore this paragraph 
has been modified to apply to all types of landing gear energy 
absorption tests (not just drop tests) and it is now set forth in 
Sec. 25.723(a)(2) of the proposed rule. It is expected that these 
revisions will have no effect on the level of safety provided by the 
requirement.

Paperwork Reduction Act

    In accordance with the Paperwork Reduction Act of 1995 (44 U.S.C. 
3507(d)), there are no requirements for information collection 
associated with this proposed rule.

International Compatibility

    The FAA has reviewed corresponding International Civil Aviation 
Organization international standards and recommended practices and 
Joint Aviation Authorities regulations, where they exist, and has 
identified no differences in these proposed amendments and the foreign 
regulations.

Regulatory Evaluation Summary

    Changes to Federal regulations must undergo several economic 
analyses. First, Executive Order 12866 directs 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 requires agencies to analyze the 
economic effect of regulatory changes on small entities. Third, the 
Office of Management and Budget directs agencies to assess the effect 
of regulatory changes on international trade. In conducting these 
analyses, the FAA has determined that this proposed

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rule is not ``a significant regulatory action'' under section 3(f) of 
Executive Order 12866 and, therefore, is not subject to review by the 
Office of Management and Budget. This proposed rule is not considered 
significant under the regulatory policies and procedures of the 
Department of Transportation (44 FR 11034, February 26, 1979). This 
proposed rule would not have a significant impact on a substantial 
number of small entities and would not constitute a barrier to 
international trade. The FAA invites the public to provide comments and 
supporting data on the assumptions made in this evaluation. All 
comments received will be considered in the final regulatory 
evaluation.
    The proposed requirements, applicable to future type certificated 
transport category airplanes, would result in two regulatory changes: 
(1) Utilizing landing gear energy absorption tests to validate the 
landing gear dynamic characteristics rather than the limit load factor 
value, and (2) confirming energy absorption characteristics by 
requiring tests at either the maximum landing weight or maximum takeoff 
weight condition, whichever provides the maximum landing impact energy. 
This is in contrast to current requirements which require tests at both 
weight conditions.
    The test results would be used to develop the analytical modeling 
of the landing gear dynamic characteristics. These regulatory changes 
would not result in any physical change in the way landing gears are 
tested: the attitude of the gear being usually simulated directly by 
orienting the gear on the rig and drag loads being applied by spinning 
the wheel up to the ground speed. Therefore, it would not impose 
additional costs on manufacturers. This was confirmed by two 
manufacturers.
    Significant cost savings may result from not having to test both at 
maximum landing weight and maximum takeoff weight, but instead, 
conducting shock absorption tests only for the conditions associated 
with maximum energy. One manufacturer estimates that these tests would 
result in 15 fewer test conditions per airplane certification. At a 
cost of $5,000 per condition, the total cost savings would reach 
$75,000 per airplane certification. Another manufacturer estimates a 
cost savings of approximately $190,000 for a ten-year period. 
Additionally, by harmonizing the standards of the Federal Aviation 
Regulations and JAR, the proposed rule would yield cost savings by 
eliminating duplicate certification activities.
    Based on the finding of regulatory cost-savings, coupled with the 
cost-savings realizable from harmonization, and the expectation that 
these revisions will have no effect on the level of safety provided by 
the test requirements, the FAA has determined that the proposed rule 
would be cost-beneficial.

Initial Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 establishes ``as a principle 
of regulatory issuance that agencies shall endeavor, consistent with 
the objective of the rule and of applicable statutes, to fit regulatory 
and informational requirements to the scale of the business, 
organization, and governmental jurisdictions subject to regulation.'' 
To achieve that principal, the Act requires agencies to solicit and 
consider flexible regulatory proposals and to explain the rationale for 
their actions. The Act covers a wide range of small entities, including 
small businesses, not-for-profit organizations and small governmental 
jurisdictions.
    Agencies must perform a review to determine whether a proposed or 
final rule will have a significant economic impact on a substantial 
number of small entities. If the determination is that it will, the 
agency must prepare a regulatory flexibility analysis (RFA) as 
described in the Act. However, if an agency determines that a proposed 
or final rule is not expected to have a significant economic impact on 
a substantial number of small entities, section 605(b) of the 1980 act 
provides that the head of the agency may so certify and an RFA is not 
required. The certification must include a statement providing the 
factual basis for this determination, and the reasoning should be 
clear.
    The proposed rule would affect manufacturers of transport category 
airplanes produced under future new airplane type certifications. For 
manufacturers, a small entity has 1,500 or fewer employees. Since no 
part 25 airplane manufacturer has 1,500 or fewer employees, FAA 
certifies that the proposed rule will not have a significant economic 
impact on a substantial number of small entities.

International Trade Impact Statement

    The provisions of this proposed rule would have no adverse impact 
on trade for both U.S. firms doing business in foreign countries and 
foreign firms doing business in the United States. By making U.S. 
landing gear test requirements conform with JAR requirements, 
international trade in aircraft would be enhanced by eliminating 
redundant testing costs for part 25 airplane manufacturers, possibly 
resulting in some cost savings for users of aircraft.

Federalism Implications

    The regulations proposed herein would not have substantial direct 
effects on the states, on the relationship between the national 
government and the states, or on the distribution of power and 
responsibilities among the various levels of government. Thus, in 
accordance with Executive Order 12612, it is determined that this 
proposal does not have sufficient federalism implications to warrant 
the preparation of a federalism assessment.

Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (the Act), 
codified in 2 U.S.C. 1501-1571, requires each Federal agency, to the 
extent permitted by law, to prepare a written assessment of the effects 
of any Federal mandate in a proposed or final agency rule that may 
result in the expenditure by State, local, and tribal governments, in 
the aggregate, or by the private sector, of $100 million or more 
(adjusted annually for inflation) in any one year. Section 204(a) of 
the Act, 2 U.S.C. 1534(a), requires the Federal agency to develop an 
effective process to permit timely input by elected officers (or their 
designees) of State, local, and tribal governments on a proposed 
``significant intergovernmental mandate.'' A ``significant 
intergovernmental mandate'' under the Act is any provision in a Federal 
agency regulation that would impose an enforceable duty upon State, 
local, and tribal governments, in the aggregate, of $100 million 
(adjusted annually for inflation) in any one year. Section 203 of the 
Act, 2 U.S.C. 1533, which supplements section 204(a), provides that 
before establishing any regulatory requirements that might 
significantly or uniquely affect small governments, the agency shall 
have developed a plan that, among other things, provides for notice to 
potentially affected small governments, if any, and for a meaningful 
and timely opportunity to provide input in the development of 
regulatory proposals.
    This proposed rule does not contain a Federal intergovernmental or 
private sector mandate that exceeds $100 million a year.

Regulations Affecting Interstate Aviation in Alaska

    Section 1205 of the FAA Reauthorization Act of 1996 (110 Stat. 
3213) requires the Administrator, when

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modifying regulations in Title 14 of the CFR in a manner affecting 
interstate aviation in Alaska, to consider the extent to which Alaska 
is not served by transportation modes other than aviation, and to 
establish such regulatory distinctions as he or she considers 
appropriate. Because this proposed rule would apply to the 
certification of future designs of transport category airplanes and 
their subsequent operation, it could, if adopted, affect interstate 
aviation in Alaska. The FAA therefore specifically requests comments on 
whether there is justification for applying the proposed rule 
differently in interstate operations in Alaska.

Environmental Analysis

    Federal Aviation Administration Order 1050.1D defines FAA actions 
that may be categorically excluded from preparation of a National 
Environmental Policy Act (NEPA) environmental assessment or 
environmental impact statement. In accordance with FAA Order 1050.1D, 
appendix 4, paragraph 4(j), this rulemaking, which if implemented may 
cause a significant impact on the human environment, qualifies for a 
categorical exclusion.

Energy Impact

    The energy impact of the proposed rule has been assessed in 
accordance with the Energy Policy and Conservation Act (EPCA) and 
Public Law 94-163, as amended (42 U.S.C. 6362). It has been determined 
that it is not a major regulatory action under the provisions of the 
EPCA.

List of Subjects 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

The Proposed Amendments

    In consideration of the foregoing, the Federal Aviation 
Administration proposes to amend part 25 of Title 14, Code of Federal 
Regulations as follows:

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

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

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

    2. Section 25.473 is amended by revising paragraph (d) to read as 
follows:


Sec. 25.473  Landing load conditions and assumptions.

* * * * *
    (d) The landing gear dynamic characteristics must be validated by 
tests as defined in Sec. 25.723(a).
* * * * *
    3. Section 25.723 is amended by revising paragraph (a) to read as 
follows:


Sec. 25.723  Shock absorption tests.

    (a) Except as provided in paragraph (a)(3) of this section, the 
landing gear dynamic characteristics used for design must be validated 
by energy absorption tests. The dynamic characteristics must be 
substantiated for the range of landing conditions, airplane 
configurations, and service variations expected in operation.
    (1) The configurations subjected to energy absorption tests must 
include at least the maximum landing weight or the maximum takeoff 
weight, whichever produces the greater value of landing impact energy.
    (2) The test attitude of the landing gear unit and the application 
of appropriate drag loads during the test must simulate the airplane 
landing conditions in a manner consistent with the development of 
rational or conservative limit loads.
    (3) Changes in previously approved design weights and minor changes 
in design may be substantiated by analyses based on previous tests 
conducted on the same basic landing gear system that has similar energy 
absorption characteristics.
* * * * *


Sec. 25.725  [Removed and Reserved]

    4. Remove and reserve Sec. 25.725.


Sec. 25.727  [Removed and Reserved]

    5. Remove and reserve Sec. 25.727.
* * * * *
    Issued in Washington D.C. on June 10, 1999.
Frank Paskiewicz,
Acting Director, Aircraft Certification Service.
[FR Doc. 99-15381 Filed 6-17-99; 8:45 am]
BILLING CODE 4910-13-U