[Federal Register Volume 61, Number 151 (Monday, August 5, 1996)]
[Proposed Rules]
[Pages 40710-40712]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-19361]
[[Page 40709]]
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Part II
Department of Transportation
_______________________________________________________________________
Federal Aviation Administration
_______________________________________________________________________
14 CFR Part 25
Braked Roll Conditions; Proposed Rule
Federal Register / Vol. 61, No. 151 / Monday, August 5, 1996 /
Proposed Rules
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. 28643; Notice No. 96-10]
RIN 2120-AF83
Braked Roll Conditions
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking.
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SUMMARY: This notice proposes to amend the requirements for landing
gear braking on transport category airplanes to require that the
airplane be designed to withstand main landing gear maximum braking
forces during ground operations. This action would ensure that the
landing gear and fuselage are capable of withstanding the dynamic loads
associated with the maximum dynamic braking condition, and would also
relieve a burden on industry by eliminating differences between the
Federal Aviation Regulations (FAR) and European Joint Aviation
Requirements (JAR).
DATES: Comments must be received on or before November 4, 1996.
ADDRESSES: Comments on this proposal may be mailed in triplicate to:
Federal Aviation Administration, Office of the Chief Counsel,
Attention: Rules Docket (AGC-10), Docket No. 28643, 800 Independence
Avenue SW., Washington, DC 20591; or delivered in triplicate to: Room
915G, 800 Independence Avenue SW., Washington, DC 20591. Comments
delivered must be marked Docket No. 28643. Comments may also be
submitted electronically to: nprmcmts@mail.hq.faa.gov. The official
docket may be examined in Room 915G weekdays, except Federal holidays,
between 8:30 a.m. and 5:00 p.m. In addition, the FAA is maintaining an
information docket of comments in the Office of the Assistant Chief
Counsel (ANM-7), FAA, Northwest Mountain Region, 1601 Lind Avenue SW.,
Renton, Washington 98055-4056. Comments in the information docket may
be examined in the Office of the Assistant Chief Counsel weekdays,
except Federal holidays, between 7:30 a.m. and 4:00 p.m.
FOR FURTHER INFORMATION CONTACT:
Iven D. Connally, FAA, Airframe and Propulsion Branch (ANM-112),
Transport Airplane Directorate, Aircraft Certification Service, 1601
Lind Avenue SW., Renton, Washington 98055-4056; telephone (206) 227-
2120.
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 the environmental, energy, or economic
impact that might result from adopting the proposal contained in this
notice are also invited. Substantive comments should be accompanied by
cost estimates. Commenters should identify the regulatory docket or
notice number and submit comments in triplicate to the Rules Docket
address specified 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. The proposal contained in this
notice may be changed in light of comments received. All comments will
be available in the Rules Docket, both before and after the closing
date for comments, for examination by interested persons. A report
summarizing each substantive public contact with FAA personnel
concerning this rulemaking will be filed in the docket. Commenters
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. 28643.'' The
postcard will be the date stamped and returned to the commenter.
Availability of the 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 online Federal Register database through GPO Access
(telephone: 202-512-1661), or the FAA's Aviation Rulemaking Advisory
Committee Bulletin Board service (telephone: 202-267-5948).
Internet users may reach the FAA's web page at http://www.faa.gov
or GPO's Federal Register web page at http://www.access.gpo.gov/
su__docs for access to recently published rulemaking documents.
Any person may obtain a copy of this NPRM by submitting a request
to the Federal Aviation Administration, Office of Rulemaking, ARM-1,
800 Independence Avenue SW., Washington, D.C. 20591, or by calling
(202) 267-9677. Communications must identify the notice number of this
NPRM. Persons interested in being placed on a mailing list for future
rulemaking documents should request from the Office of Public Affairs,
Attention: Public Inquiry Center, APA-230, 800 Independence Ave SW.,
Washington, D.C. 20591, or by calling (202) 267-3484, a copy of
Advisory Circular No. 11-2A, Notice of Proposed Rulemaking Distribution
System, which describes the application procedure.
Background
The current 14 CFR part 25 airworthiness standards, Sec. 25.493,
and its predecessor rule, Civil Air Regulations (CAR) 4b.235(b),
prescribe conditions that the airplane structure and landing gear must
be designed to withstand during airplane taxing with a constant
(steady) application of brakes (``braked roll'' condition). The taxi
condition is generally the most critical condition regarding nose gear
and forward fuselage loading during the braking event, due to the
increased braking coefficient of friction at low speeds and the lack of
lift on the wings and lack of aerodynamic damping. Both rules treat the
braked roll condition as a static equilibrium condition that accounts
for the airplane weight and the added nose down force caused by steady
braking. Neither rule accounts for the additional dynamic loads on the
nose gear and fuselage caused by the initial pitching motion of the
airplane due to sudden application of main landing gear brakes.
Adequate strength has been achieved on existing airplanes by
application of other part 25 design requirements and by the
manufacturers' need to comply with the more stringent British Civil
Airworthiness Requirements (BCAR).
For many years the BCAR have included a dynamic braking condition
that requires that consideration be given to the maximum likely
combination of dynamic vertical reaction and sudden increase in drag
load that could occur on the nose gear as a result of sudden main gear
braking while encountering obstacles. The BCAR address obstacles such
as overruns onto semi-prepared surfaces during rejected takeoffs,
running off the edge then back on to the runway during avoidance
maneuvers, running over displaced or lowered edges of runway paving,
and inadvertent use of runways under repair. In application of the BCAR
requirement, it was found that U.S. designed airplanes generally have
had adequate strength to meet this condition without requiring any
modifications. However, this may not always be the case, especially if
new airplane designs are significantly different from past conventional
configurations in vertical and longitudinal mass distributions of
[[Page 40711]]
fuel, payload, engine location, etc. As the takeoff weight increases
with respect to landing weight, the dynamic braked roll condition can
become more critical for the nose gear and fuselage. Without a specific
dynamic braked roll condition, the current braked roll requirements do
not guarantee that such strength will always be present.
In 1988, the FAA, in cooperation with the JAA and other
organizations representing American and European aerospace industries,
began a process to harmonize the airworthiness requirements of the
United States and the airworthiness requirements of Europe. The
objective was to achieve common requirements for the certification of
transport airplanes without a substantive change in the level of
safety. Other airworthiness authorizes such as Transport Canada also
participated in the process.
In 1992, the harmonization effort was undertaken by the Aviation
Rulemaking Advisory Committee (ARAC) to harmonize the loads
requirements. A working group of industry and government structural
loads specialists from Europe, the Untied States, and Canada was
chartered by notice in the Federal Register (58 FR 13819, March 15,
1993). On June 10, 1994 (58 FR 30081), the Loads & Dynamics
Harmonization Working Group was assigned the additional task of
reviewing and harmonizing the braked roll condition. That harmonization
effort has now progressed to the point where a specific proposal has
been developed by the working group, adopted by the ARAC, and
recommended to the FAA by letter dated November 6, 1995.
Discussion
The European Joint Aviation Authorities (JAA) consider the BCAR
braked roll condition too severe a condition to be considered for an
airplane design requirement. For instance, it is unlikely that maximum
braking will occur at the same instant the gear runs off the runway or
during an avoidance maneuver. Nevertheless, the JAA has recognized that
sudden application of main gear maximum braking during ground
operations is a likely event that the airplane should be able to
withstand; and since October 1988, the European Joint Aviation
Requirements (JAR-25) have included a dynamic braked roll condition,
which now supersedes the previously cited BCAR requirement.
The FAA agrees with the JAA that the sudden application of main
gear maximum braking force during ground operations is a likely
operational event that the airplane must be able to withstand, and that
the BCAR requirement that combines high vertical loads with extreme
drag load is an unrealistic condition for the nose gear. However, the
current braked roll condition of 14 CFR 25.493 does not ensure that the
nose landing gear and fuselage structure are capable of withstanding
the loads developed from sudden application of main gear maximum
braking force.
The FAA considers the JAR dynamic braked roll condition to be a
realistic method to account for dynamic loads that could exceed the
static load requirements of Sec. 25.493(b) on future designs. The
proposed rule would amend the current FAR braked roll conditions, which
address only the loads produced by airplane weight and steady braking
forces, to add a requirement to include the effects of dynamic braking.
This would account for the effects of airplane pitch inertia on the
nose gear and fuselage. The proposed new Sec. 25.439(e) provides a
mathematical expression, in terms of airplane weight, geometry,
coefficient of friction, and dynamic response factor, that may be used
in the absence of a more rational analysis to account for the dynamic
loads developed on the nose landing gear during hard braking
conditions. An analytical expression is also provided for the dynamic
response factor, f, that may be used if there is no data to more
accurately define this parameter. Regardless of the FAR requirements,
the existing JAR requirement will be imposed on U.S. manufactured
airplanes seeking approval to the JAR. It is therefore proposed to
harmonize the FAR with the JAR by incorporating the dynamic braked roll
condition in the FAR.
Since there is no evidence to suggest that the current fleet of
transport category airplanes does not have adequate strength to
withstand the proposed dynamic braked roll condition, the FAA does not
consider it necessary to apply this requirement retroactively.
Regulatory Evaluation Summary
Preliminary Regulatory Evaluation, Initial Regulatory Flexibility
Determination, and Trade Impact Assessment
Proposed 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 effects of regulatory changes on small
entities. Third, the Office of Management and Budget directs agencies
to assess the effects of regulatory changes on international trade. In
conducting these analyses, the FAA has determined that this proposal:
(1) Would generate benefits that justify its costs; (2) is not a
``significant regulatory action'' as defined in the 'Executive Order
and is not ``significant'' as defined in DOT's Regulatory Policies and
Procedures; (3) would not have a significant economic impact on a
substantial number of small entities; and (4) would not constitute a
barrier to international trade. These analyses, available in the
docket, are summarized below.
The proposed amendment would codify current industry practice and
would not impose additional costs on manufacturers of transport
category airplanes. By conforming Sec. 25.493 of the FAR with
Sec. 25.493 of the JAR, the proposed amendment would increase
harmonization between American and European airworthiness standards and
reduce duplicate certification costs.
Regulatory Flexibility Determination
The Regulatory Flexibility Act of 1980 (RFA) was enacted by
Congress to ensure that small entities are not unnecessarily or
disproportionately burdened by Government regulations. The RFA requires
a Regulatory Flexibility Analysis, in which alternatives are considered
and evaluated, if a rule is expected to have ``a significant economic
impact on a substantial number of small entities.'' FAA Order 2100.14A,
Regulatory Flexibility Criteria and Guidance, prescribes standards for
complying with RFA review requirements in FAA rulemaking actions. The
Order defines ``small entities'' in terms of size thresholds,
``significant economic impact'' in terms of annualized cost thresholds,
and ``substantial number'' as a number which is not less than eleven
and which is more than one-third of the small entities subject to the
proposed or final rule.
The proposed amendment would affect manufacturers of transport
category airplanes produced under new type certificates. For airplane
manufacturers, Order 2100.14A specifies a size threshold for
classification as a small entity as 75 or fewer employees. Since no
part 25 airplane manufacturer has 75 or fewer employees, the proposed
amendment would not have a significant economic
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impact on a substantial number of small airplane manufacturers.
International Trade Impact Assessment
The proposed amendment would not constitute a barrier to
international trade, including the export of American airplanes to
foreign countries and the import of foreign airplanes into the United
States. Instead, by harmonizing standards of the FAR with those of the
JAR, it would lessen restraints on trade.
Federalism Implications
The regulation 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. Therefore, in
accordance with Executive Order 12612, it is determined that this
proposal would not have sufficient federalism implications to warrant
the preparation of a Federalism Assessment.
International Civil Aviation Organization (ICAO) and Joint Aviation
Regulations
In keeping with U.S. obligations under the Convention on
International Civil Aviation, it is FAA policy to comply with ICAO
Standards and Recommended Practices to the maximum extent practicable.
The FAA has determined that this proposed rule does not conflict with
any international agreement of the United States.
Paperwork Reduction Act
In accordance with the Paperwork Reduction Act of 1990 (44 U.S.C.
3501 et seq.), there are no reporting or recordkeeping requirements
associated with this proposed rule.
Conclusion
Because the proposed changes to the braked roll condition are not
expected to result in substantial economic cost, the FAA has determined
that this proposed rule would not be significant under Executive Order
12866. Because this is an issue that has not prompted a great deal of
public concern, the FAA has determined that this action is not
significant as defined in Department of Transportation Regulatory
Policy and procedures (44 FR 11034, February 25, 1979). In addition,
since there are no small entities affected by this proposed rulemaking,
the FAA certifies, under the criteria of the Regulatory Flexibility
Act, that this proposed rule, if adopted, would not have a significant
economic impact, positive or negative, on a substantial number of small
entities. An initial regulatory evaluation of the proposed rule,
including a Regulatory Flexibility Determination and Trade Impact
Analysis, has been placed in the docket. A copy may be obtained by
contacting the person identified under the caption, for further
information contact.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
The Proposed Amendment
Accordingly, the Federal Aviation Administration (FAA) proposes to
amend 14 CFR part 25 of the Federal Aviation Regulations (FAR) 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, 44704.
2. By amending Sec. 25.493 by revising paragraph (c), and by adding
new paragraphs (d) and (e) to read as follows:
Sec. 25.493 Braked roll conditions.
* * * * *
(c) A drag reaction lower than that prescribed in this section may
be used if it is substantiated that an effective drag force of 0.8
times the vertical reaction cannot be attained under any likely loading
condition.
(d) An airplane equipped with a nose gear must be designed to
withstand the loads arising from the dynamic pitching motion of the
airplane due to sudden application of maximum braking force. The
airplane is considered to be at design takeoff weight with the nose and
main gears in contact with the ground, and with a steady-state vertical
load factor of 1.0. The steady-state nose gear reaction must be
combined with the maximum incremental nose gear vertical reaction
caused by the sudden application of maximum braking force as described
in paragraphs (b) and (c) of this section.
(e) In the absence of a more rational analysis, the nose gear
vertical reaction prescribed in paragraph (d) of this section must be
calculated according to the following formula:
[GRAPHIC] [TIFF OMITTED] TP05AU96.001
Where:
VN= Nose gear vertical reaction.
WT= Design takeoff weight.
A = Horizontal distance between the c.g. of the airplane and the nose
wheel.
B = Horizontal distance between the c.g. of the airplane and the line
joining the centers of the main wheels.
E = Vertical height of the c.g. of the airplane above the ground in the
1.0 g static condition.
= Coefficient of friction of 0.80.
f = Dynamic response factor; 2.0 is to be used unless a lower factor is
substantiated. In the absence of other information, the dynamic
response factor f may be defined by the equation:
[GRAPHIC] [TIFF OMITTED] TP05AU96.002
Where:
is the effective critical damping ratio of the rigid body
pitching mode about the main landing gear effective ground contact
point.
Issued in Washington DC on July 24, 1996.
Elizabeth Yoest,
Acting Director, Aircraft Certification Services.
[FR Doc. 96-19361 Filed 8-2-96; 8:45 am]
BILLING CODE 4910-13-M
