[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]


      
      

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Part II





Department of Transportation





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Federal Aviation Administration



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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: [email protected]. 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