[Federal Register Volume 64, Number 153 (Tuesday, August 10, 1999)]
[Proposed Rules]
[Pages 43570-43578]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-20518]
[[Page 43569]]
_______________________________________________________________________
Part VIII
Department of Transportation
_______________________________________________________________________
Federal Aviation Administration
_______________________________________________________________________
14 CFR Part 25
Revision of Braking Systems Airworthiness Standards To Harmonize With
European Airworthiness Standards for Transport Category Airplanes;
Proposed Rule
Proposed Technical Standard Order (TSO)-C135, Transport Airplane Wheels
and Wheel and Brake Assemblies; Proposed Rule
Proposed Advisory Circular (AC) 25.735-1X, Brakes and Braking Systems
Certification Tests and Analysis; Proposed Rule
Federal Register / Vol. 64, No. 153 / Tuesday, August 10, 1999 /
Proposed Rules
[[Page 43570]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-1999-6063; Notice No. 99-16]
RIN 2120-AG80
Revision of Braking Systems Airworthiness Standards To Harmonize
With European Airworthiness Standards for Transport Category Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking.
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SUMMARY: The Federal Aviation Administration proposes to revise the
airworthiness standards for transport category airplanes to harmonize
braking systems design and test requirements with standards proposed
for the European Joint Aviation Requirements (JAR). These proposals
were 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), and are intended to
benefit the public interest by standardizing certain requirements,
concepts, and procedures contained in the airworthiness standards
without reducing, but potentially enhancing, the current level of
safety.
DATES: Comments must be received on or before November 8, 1999.
ADDRESSES: Comments on this document should be mailed or delivered, in
duplicate, to U.S. Department of Transportation Dockets, Docket No.
FAA-1999-6063, 400 Seventh Street SW., Room Plaza 401, Washington DC
20590. Comments may also be sent electronically to the following
Internet address: [email protected] Comments may be filed and/or
examined in Room Plaza 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),
Federal Aviation Administration, Northwest Mountain Region, 1601 Lind
Avenue SW., Renton, WA 98055-4056. Comments in the information docket
may be examined between 7:30 a.m. and 4:00 p.m. weekdays, except
Federal holidays.
FOR FURTHER INFORMATION CONTACT: Mahinder K. Wahi, FAA, Propulsion/
Mechanical Systems/Cabin Safety Branch, ANM-112, Transport Airplane
Directorate, 1601 Lind Avenue SW., Renton, WA 98055-4056; telephone
(425) 227-2142; facsimile (425) 227-1320.
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, federalism,
or economic impact that might result from adopting the proposals in
this notice are also invited. Substantive comments should be
accompanied by cost estimates. Commenters must identify the regulatory
docket or notice number and submit comments in duplicate to the Docket
address specified above.
All comments received, as well as a report summarizing each
substantive public contact with FAA personnel concerning this
rulemaking, will be filed in the docket. The Docket is available for
public inspection before and after the comment closing date.
All comments received on or before the closing date will be
considered by the Administrator before taking action on this proposed
rulemaking. Comments filed late will be considered to the extent
practicable. The proposals in this notice may be changed in light of
the comments received.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this notice must include with those comments a
pre-addressed, stamped postcard on which the following statement is
made: ``Comments to Docket No. FAA-1999-6063.'' The postcard will be
date stamped and mailed 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 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/nprm.htm or the Government Printing Office's webpage at
http://www.access.gpo.gov/nara 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, DC 20591, or by calling 202-
267-9680. Communications must identify the notice number of docket
number of this NPRM.
Persons interested in being placed on the mailing list for future
NPRM's should request from the above office a copy of Advisory Circular
No. 11-2A, Notice of Proposed Rulemaking Distribution System, which
describes the application procedure.
Background
The airworthiness standards for transport category airplanes are
contained in 14 CFR part 25. Manufacturers of transport category
airplanes must show that each airplane they produce of a different type
design complies with the relevant standards of part 25. These standards
apply to airplanes manufactured within the U.S. for use by U.S.-
registered operators and to airplanes manufactured in other countries
and imported under a bilateral airworthiness agreement.
In Europe, the Joint Aviation Requirements (JAR) were developed by
the Joint Aviation Authorities (JAA) to provide a common set of
airworthiness standards for use within the Europe aviation community.
The airworthiness standards for European type certification of
transport category airplanes, JAR-25, are based on part 25 of Title 14.
Airplanes certificated to the JAR-25 standards, including airplanes
manufactured in the U.S. for export to Europe, receive type
certificates that are accepted by the aircraft certification
authorities of 23 European countries.
Although part 25 and JAR-25 are very similar, they are not
identical. Differences between the FAR and the JAR can result in
substantial additional costs when airplanes are type certificated to
both standards. These additional costs, however, frequently do not
bring about an increase in safety. For example, part 25 and JAR-25 may
use different means to accomplish the same safety intent. In this case,
the manufacturer is usually burdened with meeting both requirements,
although the level of safety is not increased correspondingly.
Recognizing that a common set of standards would not only economically
benefit the aviation industry, but would also maintain the necessary
high level of safety, the FAA and JAA consider harmonization to be a
high priority.
In 1988, the FAA, in cooperation with the JAA and other
organizations representing the American and European aerospace
industries, began a process to harmonize the airworthiness requirements
of the United States and
[[Page 43571]]
the airworthiness requirements of Europe, especially in the areas of
Flight Test and Structures.
The Aviation Rulemaking Advisory Committee
The Aviation Rulemaking Advisory Committee (ARAC) was formally
established by the FAA on January 22, 1991 (56 FR 2190) to provide
advice and recommendations concerning the full range of the FAA's
safety-related rulemaking activity. This advice was sought to develop
better rules in less overall time using fewer FAA resources than are
currently needed. The committee provides the opportunity for the FAA to
obtain firsthand information and insight from interested parties
regarding proposed new rules or revisions of existing rules.
There are 64 member organizations on the committee, representing a
wide range of interests within the aviation community. Meetings of the
committee are open to the public, except as authorized by section 10(d)
of the Federal Advisory Committee Act.
The ARAC establishes working groups to develop proposals to
recommend to the FAA for resolving specific issues. Tasks assigned to
working groups are published in the Federal Register. Although working
group meetings are not generally open to the public, all interested
parties are invited to participate as working group members. Working
groups report directly to the ARAC, and the ARAC must accept a working
group proposal before that proposal can be presented to the FAA as an
advisory committee recommendation.
The activities of the ARAC will not, however, circumvent the public
rulemaking procedures. After an ARAC recommendation is received and
found acceptable by the FAA, the agency proceeds with the normal public
rulemaking procedures. Any ARAC participation in a rulemaking package
will be fully disclosed in the public docket.
Starting in 1992, the FAA harmonization effort for various systems
related airworthiness requirements was undertaken by the ARAC. A
working group of industry and government braking systems specialists of
Europe, the United States, and Canada was chartered by notice in the
Federal Register (59 FR 30080, June 10, 1994). The working group was
tasked to develop a harmonized standard, such as a Technical Standard
Order (TSO), for approval of wheels and brakes to be installed on
transport category airplanes and to develop a draft notice of proposed
rulemaking (NPRM), with supporting economic and other required
analyses, and/or any other related guidance material or collateral
documents, such as advisory circulars, concerning new or revised
requirements and the associated test conditions for wheels, brakes and
braking systems, installed in transport category airplanes (Sec. 25.731
and 25.735). The JAA is to develop a similar proposal to amend JAR-25,
as necessary, to achieve harmonization.
The rulemaking proposal contained in this notice is based on a
recommendation developed by the Braking Systems Harmonization Working
Group, and presented to the FAA by the ARAC as a recommendation.
General Discussion of the Proposals
The FAA proposes to amend 14 CFR 25.731 and 25.735 to harmonize
these sections with JAR-25. The JAA intends to publish a Notice of
Proposed Amendment (NPA), also developed by the Braking Systems
Harmonization Working Group, to revise JAR-25 as necessary to ensure
harmonization in those areas for which the proposed amendments differ
from the current JAR-25, Change 14. When published, the NPA will be
placed in the docket for this rulemaking.
Generally, the FAA proposes to: (1) add appropriate existing JAR
requirements to achieve harmonization; (2) move some of the existing
regulatory text, considered to be of an advisory nature, to an advisory
circular; (3) add regulations addressing automatic brake systems, brake
wear indicators, pressure release devices, and system compatibility;
and (4) consolidate and/or separate requirement subparagraphs for
clarity.
A new proposed Advisory Circular (AC) 25.735-1X, Brakes and Braking
Systems Certification Tests and Analysis, has been developed by the
ARAC Harmonization Working Group to ensure consistent application of
these proposed revised standards. Public comments concerning AC 25.735-
1X are invited by separate notice published elsewhere in this issue of
the Federal Register. The JAA intends to publish an Advisory Material
Joint (AMJ), also developed by the Harmonization Working Group, to
accompany its NPA. The proposed AC and the proposed AMJ contain
harmonized advisory information.
A new proposed TSO-C135 has also been developed by the
Harmonization Working Group as a harmonized standard for approval of
transport airplane wheels and wheel and brake assemblies to replace
applicable parts of the existing TSO-C26c, Aircraft Wheels and Wheel-
Brakes Assemblies, dated May 18, 1984. Pubic comments concerning TSO-
C135 are invited by separate notice published elsewhere in this issue
of the Federal Register. The JAA intends to adopt TSO-C135 as Joint
Technical Standard Order (JTSO)-C135 and publish it to accompany their
NPA.
Section by Section Discussion of the Proposals
Proposal 1. The FAA proposes to revise the current heading of
Sec. 25.735, ``Brakes,'' to read ``Sec. 25.735 Brakes and braking
systems.''
Discussion: This section covers not only the brakes and their
performance requirements and safety considerations, but also provides
requirements for the systems and equipment associated with the brakes.
As examples, the proposed additional paragraph (b)(2) refers to the
brake hydraulic system and the hydraulic fluid supplying the brakes,
and the proposed paragraph (e) refers to the antiskid system. The
proposed change is of an editorial nature only, and consequently would
have no impact on the current level of safety.
Proposal 2. The FAA proposes to add a heading to and revise the
text of Sec. 25.735(a) to read, ``(a) Approval. Each assembly
consisting of a wheel(s) and brake(s) must be approved.''
Discussion: The current Sec. 25.735(a), which states that each
brake must be approved, is considered incomplete. Although a wheel not
associated with a brake (non-braked) may be approved on its own per the
applicable TSO, a brake approval is always considered in combination
with its associated wheel(s) (i.e., for a combined wheel(s) and
brake(s) assembly). The proposed change is of an editorial nature only
and therefore would have no impact on the current level of safety.
Applicable advisory information would be included in proposed AC
25.735-1X.
Proposal 3. The FAA proposes to add the heading ``Brake system
capability'' to Sec. 25.735(b), to separate and revise the current text
of the first sentence of Sec. 25.735(b) into Secs. 25.735(b) and
(b)(1), and to delete the current text of the entire second sentence to
read:
``(b) Brake system capability. The brake system, associated systems
and components must be designed and constructed so that: (1) if any
electrical, pneumatic, hydraulic or mechanical connecting or
transmitting element fails, or if any single source of hydraulic or
other brake operating energy supply is lost, it is possible to bring
the airplane to rest with a braked roll stopping distance of not more
than two times that
[[Page 43572]]
obtained in determining the landing distance as prescribed in
Sec. 25.125.''
Discussion: The current text of the first sentence of
Sec. 25.735(b) reads, ``The brake systems and associated systems must
be designed and constructed so that if any electrical, pneumatic,
hydraulic, or mechanical connecting or transmitting element (excluding
the operating pedal or handle) fails, or if any single source of
hydraulic or other brake operating energy supply is lost, it is
possible to bring the airplane to rest under conditions specified in
Sec. 25.125 with a mean deceleration during the landing roll of at
least 50 percent of that obtained in determining the landing distance
as prescribed in that section.''
Under this proposal, the term ``components'' would be added to the
terms ``brake system and associated systems'' in the first sentence to
make it more comprehensive. The parenthetical phrase ``(excluding the
operating pedal or handle)'' would be deleted because no justification
could be found for such an exclusion. The words ``braked roll stopping
distance'' would be inserted in place of ``landing roll'' to clarify
that the requirement refers only to the distance covered while the
brakes are applied. The change in concept from at least 50 percent mean
deceleration to not more than two times the landing distance is
intended to eliminate any possible confusion between ``mean'' and
``average'' deceleration, and to state the requirement more clearly in
terms of its real intent. The other changes in text are editorial and
are made for clarity.
The current second sentence reads ``subcomponents within the brake
assembly, such as brake drum, shoes, and actuators (or their
equivalents), shall be considered as connecting or transmitting
elements, unless it is shown that leakage of hydraulic fluid resulting
from failure of the sealing elements in these subcomponents within the
brake assembly would not reduce the braking effectiveness below that
specified in this paragraph.'' The current second sentence would be
removed and, due to its advisory content, included as guidance material
in proposed AC 25.735-1X.
The proposed changes are clarifications of current regulations and
the associated terminology and therefore would have no impact on the
current level of safety. Applicable advisory information would be
included in proposed AC 25.735-1X.
Proposal 4. The FAA proposes to add a new Sec. 25.735(b)(2) that
would contain the intent and content of the ACJ 25.735(b) of JAR-25
regarding protection against fire resulting from hydraulic fluid
leakage, spillage, or spraying on hot brakes. The proposal would state
that, ``(2) Fluid lost from a brake hydraulic system, following a
failure in, or in the vicinity of, the brakes, is insufficient to cause
or support a hazardous fire on the ground or in flight.''
Discussion: Although the proposed requirement was previously
included in ACJ 25.735(b) as acceptable means of compliance and
interpretative material, it is now thought more appropriate that these
practices should be considered as requirements as they have generally
been treated as such in the past by both airplane manufacturers and
regulatory authorities. The current level of safety would not be
affected by this proposed change as it would adopt an existing industry
practice. Applicable advisory material would be included in proposed AC
25.735-1X.
Proposal 5. The FAA proposes to add the heading ``Brake controls''
to Sec. 25.735(c), and to separate and revise the current text of
Sec. 25.735(c) into Secs. 25.735(c) and (c)(1) to read: ``(c) Brake
Controls. The brake controls must be designed and constructed so that:
(1) Excessive control force is not required for their operation.''
Discussion: The current text reads, ``Brake controls may not
require excessive control force in their operation.'' The proposed
changes are clarifications of current regulations and the associated
terminology and therefore the current level of safety would not be
impacted. Applicable advisory material would be included in proposed AC
25.735-1X.
Proposal 6. The FAA proposes to add a new Sec. 25.735(c)(2) to
read: ``(2) If an automatic braking system is installed, means are
provided to (i) arm and disarm the system, and (ii) allow the pilot(s)
to override the system by use of manual braking.''
Discussion: The intent and content of the proposed changes have
generally been adopted in the design of current automatic braking
systems and are currently included in FAA Order 8110.8, ``Engineering
Flight Test Guide for Transport Category Airplanes,'' as interpretative
and acceptable means of compliance. Consequently, both the airplane
manufacturers and the regulatory authorities have generally considered
them as standard practices; therefore, they would not impact the
current level of safety. Applicable advisory material would be included
in proposed AC 25.735-1X.
Proposal 7. The FAA proposes to amend Sec. 25.735(d) by adding the
heading, ``Parking brake,'' and by modifying the current text from,
``The airplane must have a parking control that, when set by the pilot,
will without further attention, prevent the airplane from rolling on a
paved, level runway with takeoff power on the critical engine.'' to
``(d) Parking brake. The airplane must have a parking brake control
that, when selected on, will, without further attention, prevent the
airplane from rolling on a dry and level paved runway when the most
adverse combination of maximum thrust on one engine and up to maximum
ground idle thrust on any, or all, other engine(s) is applied. The
control must be suitably located or be adequately protected to prevent
inadvertent operation. There must be indication in the cockpit when the
parking brake is not fully released.''
Discussion: Introduction of the word ``brake'' before ``control''
clarifies that the paragraph refers to the means provided to the
flightcrew for the application of the wheel brakes in the airplane
parking mode. By revising the text, as proposed, the requirements would
be enhanced to cover not only the case of a single engine takeoff
thrust check with all other engines stopped, but would also cover an
equally if not more probable case where any or all other engines are
operating and producing up to a maximum ground idle thrust. The
proposal also clarifies the extent of the takeoff thrust to be
considered for the ``critical'' engine as the maximum that can be
achieved, and by implication also requires the relevant thrust cases
for remaining engine(s) according to the environmental circumstances
that are dictated for the achievement of the maximum takeoff thrust on
the critical engine. The word ``dry'' is added solely for clarification
of the current understanding of this requirement.
The requirement for suitable location or protection against
inadvertent operation of the parking brake control is derived from the
current ACJ 25.735(d) of JAR-25 and is introduced because it is
believed that such considerations should be regarded as requirements,
and have generally been treated as such in the past by both airplane
manufacturers and regulatory authorities. The additional requirement
for cockpit indication when the parking brake is ``not fully released''
is to caution the pilot against a takeoff with the parking brake set.
The proposed changes potentially enhance the current level of safety by
clarifying intent and addressing come critical cases. Applicable
advisory material would be included in proposed AC 25.735-1X.
Proposal 8. The FAA proposes to add the heading ``Antiskid system''
to Sec. 25.735(e), to delete the current text
[[Page 43573]]
``no single probable malfunction will result in a hazardous loss of
braking ability or directional control of the airplane'' as being
superfluous, and in order to facilitate the introduction of the new
proposed Sec. 25.735(e)(1) and (e)(2) under proposals 9 and 10
respectively, revise the remaining current text to read:
``(e) Antiskid system. If an antiskid system is installed:''
Discussion: The current Sec. 25.735(e9 reads: ``If antiskid devices
are installed, the devices and associated systems must be designed so
that no single probable malfunction will result in hazardous loss of
braking ability or directional control of the airplane.'' The reference
to antiskid devices and associated systems would be changed to
``antiskid system,'' this being more appropriate to the paragraph's
intent. The term ``probable'' was incompatible with the terminology of
Sec. 25.1309 because a ``probable'' malfunction cannot be associated
with either major or hazardous effects and, if used in the
``Sec. 25.1309'' sense, could lead to a requirement that could be seen
as less severe than Sec. 25.1309 for that specific failure condition,
with no obvious technical/state of the art reasons. It appears that the
terminology (probable and hazardous) used was probably not
``Sec. 25.1309 related'' when the requirement was first introduced.
Rather than trying to define the words, it is considered that the
requirement is adequately covered by Sec. 25.1309 and the current
Sec. 25.735(e) is superfluous. The proposed changes are of a clarifying
and an editorial nature only and therefore would have no impact on the
current level of safety. Appropriate advisory material would be
included in proposed AC 25.735-1X.
Proposal 9. The FAA proposes to add a new Sec. 25.735(e)(1) to
read.
``(1) It must operate satisfactory over the range of expected
runway conditions, without external adjustment.''
Discussion: The intent and content of the proposed changes are
currently included in FAA Order 8110.8, ``Engineering Flight Test Guide
for Transport Category Airplanes,'' as interpretative material and
acceptable means of compliance and are deemed appropriate to be adopted
as requirements. Both the airplane manufacturers and the regulatory
authorities have, in the past, considered them as standard practices;
therefore, they would not impact the current level of safety.
Applicable advisory material would be included in proposed AC 25.735-
1X.
Proposal 10. The FAA proposes to add a new Sec. 25.735(e)(2) to
read: ``(2) It must, at all times, have priority over the automatic
braking system, if installed.''
Discussion: The intent and content of the proposed change is
currently included in FAA Order 8110.8, ``Engineering Flight Test Guide
for Transport Category Airplanes,'' as interpretative material and
acceptable means of compliance and is deemed appropriate to be adopted
as a requirement. Both the airplane manufacturers and the regulatory
authorities have, in the past, considered it as a standard practice;
therefore, it would not impact the current level of safety. Applicable
advisory material would be included in proposed AC 25.735-1X.
Proposal 11. The FAA proposes to amend Sec. 25.735(f) by adding the
heading ``Kinetic energy capacity,'' by consolidating the requirements
of current paragraphs (f) and (h), by adding similar requirements for a
high energy landing condition, by removing paragraphs (f)(1) and (2),
and paragraphs (h)(1) and (2), and by revising the text to read:
``(f) Kinetic energy capacity. The design landing stop, the maximum
kinetic energy accelerate-stop, and the most severe landing stop brake
kinetic energy absorption requirements of each wheel and brake assembly
must be determined. It must be substantiated by dynamometer testing
that, at the declared fully worn limit(s) of the brake heat sink, the
wheel and brake assemblies are capable of absorbing not less than these
levels of kinetic energy. Energy absorption rates defined by the
airplane manufacturer must be achieved. These rates must be equivalent
to mean decelerations not less than 10 fps2 [feet per
second] for the design landing stop and 6 fps2 for the
maximum kinetic energy accelerate stop. The most severe landing stop
need not be considered for extremely improbable failure conditions or
if the maximum kinetic energy accelerate-stop energy is more severe.
Design landing stop is an operational landing stop at maximum landing
weight. Maximum kinetic energy accelerate-stop is a rejected takeoff
for the most critical combination of airplane takeoff weight and speed.
Most severe landing stop is a stop at the most critical combination of
airplane landing weight and speed.
Discussion: The current paragraphs (f) and (h) state that the brake
kinetic energy capacity ratings may not be less than the determined
energy absorption requirements. The proposed paragraph (f) would
require the calculation of the necessary energy absorption capacity,
and require dynamometer test substantiation of the capability of the
wheel and brake assemblies to absorb the energy at not less than
specified rates. Usually, brakes are sized to exceed the calculated
energy absorption requirements (i.e., their capacity exceeds the
requirements, hence the heading ``Kinetic energy capacity''). The term
``rating'' would be deleted because it is more relevant to the TSO than
to the regulation. The proposed change would encompass the requirements
of current paragraph (h) without the need for complete duplication of
text.
The term ``rejected takeoff'' used under current paragraph (h)
would be replaced with ``accelerate-stop'' for compatibility with
Sec. 25.109 terminology; and the term ``most severe landing stop''
would be added to address cases such as emergency return to land after
takeoff, where the brake energy for a flaps up landing may exceed that
corresponding to the accelerate-stop energy. For the accelerate-stop
and the most severe landing stop, it is intended that the initial brake
temperature resulting from previous brake use must be accounted for as
specified in paragraphs 3.3.3.3 and 3.3.4.3 in the proposed TSO-C135.
It should be noted that the consideration for the initial temperature
(in terms of residual energy) reflects an existing British Civil
Aviation authority (CAA) Specification 17 requirement. Changing the
term ``main wheel-brake assemblies'' to ``wheel and brake assemblies,''
ensures the paragraph,'' ensures the paragraph's applicability to any
wheels fitted with brakes (i.e., includes the possibility of nose wheel
brakes, etc.) and further ensures the understanding that the absorption
requirements apply to the wheel and brake assembly. The substantiation
statement requires that the wheel and brake assemblies be capable of
absorbing the calculated levels of kinetic energy at the fully worn
limit and that the energy absorption capability substantiation testing
be conducted on the dynamometer.
The current Secs. 25.735(f)(1) and (h)(1) would be incorporated in
proposed AC 25.735-1X, because their content is not strictly part of
the requirement, but provides advice on the primary features that
should be conservatively included in a rational analysis.
The current Secs. 25.735(f)(2) and (h)(2) are not strictly the
requirement, but advice on the method of energy calculation to be used.
Consequently, these would be incorporated in proposed AC 25.735-1X.
Because the required energy capacity of each wheel and brake
assembly must be determined, the need to refer to
[[Page 43574]]
``designed unequal braking distributions'' is no longer necessary and
would be deleted.
The current level of safety would be retained and possibly enhanced
by addressing the most severe landing stop condition. Applicable
advisory material would be included in proposed AC 25.735-1X.
Proposal 12. The FAA proposes to remove the current Sec. 25.735(g)
requirement.
Discussion: The current Sec. 25.735(g) requirement states that when
setting up the dynamometer test inertia, an increase in the initial
brake application speed is not a permissible method of accounting for a
reduced (i.e., lower than ideal) dynamometer mass. This method is not
permissible because, for a target test deceleration, a reduction in the
energy absorption rate would result, and could produce a performance
different from that which would be achieved with the correct brake
application speed. Such a situation is recognized and is similarly
stated in the proposed new TSO-C135, which would provide an acceptable
means for wheel and brake assembly approval under Sec. 25.735(a), thus
making current Sec. 25.735(g) unnecessary. The proposed change
consolidates existing requirements and deletes redundant wording, and
therefore would not impact the current level of safety.
Proposal 13. The FAA proposes to add a new Sec. 24.735(g), ``Brake
condition after high kinetic energy dynamometer stop(s),'' to read:
``(g) Brake condition after high kinetic energy dynamometer
stop(s). Following the high kinetic energy stop demonstration(s)
required by paragraph (f) of this section, with the parking brake
promptly and fully applied for at least three (3) minutes, it must be
demonstrated that for at least five (5) minutes from application of the
parking brake, no condition occurs (or has occurred during the stop),
including fire associated with the tire or wheel and brake assembly,
that could prejudice the safe and complete evacuation of the
airplane.''
Discussion: Paragraph (g) would require that the parking brake be
applied for a minimum of three minutes, which is considered to be the
minimum period of time required to cover the brake's ability to
maintain the airplane in a stationary condition to allow a safe
evacuation.
The requirement also gives consideration to the fact that the
flightcrew may not be aware of the condition of the brake assemblies at
the commencement of the flight, nor of the condition of the brake and
wheel assemblies following the braking maneuver. Furthermore, the
reason for the severe braking could encompass both airplane system and
engine failures or fires. It would therefore appear sensible that it
should be demonstrated that neither during the stop, nor for a
reasonable period of time after its completion, no condition(s) shall
occur as a result of these maneuvers that could further prejudice the
safe and complete evacuation of the airplane. On the basis that an
evacuation may be determined as prudent or necessary, and that such an
evacuation must be capable of completion, irrespective of the timely
response of the emergency services, for minutes would appear to be a
reasonable period of time for the associated brake systems and
equipment to remain free from conditions that might prejudice or
jeopardize the evacuation. It is proposed that this period should
commence at the time of initial application of the parking brake, this
being a time during which the possible need for evacuation and airport
emergency services occurs following an accelerate-stop. The proposed
changes provide for the additional demonstration of a safe condition
following high energy absorption by the wheels and brakes, which was
not previously required. Although previously approved brakes may have
been able to comply with the requirement, approval could not have been
refused had this not been the case. It is therefore believed that the
proposed changes would provide a potential enhancement of the current
level of safety. Applicable advisory material would be included in
proposed AC 25.735-1X.
Proposal 14. The FAA proposes to add a modified version of the
current JAR 25.735(i) as new 14 CFR 25.735(h), ``Stored energy
systems,'' to read:
``(h) Stored energy systems. An indication to the flightcrew of
usable stored energy must be provided if a stored energy system is used
to show compliance with paragraph (b)(1) of this section. The available
stored energy must be sufficient for:
(1) At least six (6) full applications of the brakes when an
antiskid system is not operating; and,
(2) Bringing the airplane to a complete stop when an antiskid
system is operating, under all runway surface conditions for which the
airplane is certificated.''
Discussion: A full brake application is defined as an application
from brakes fully released to brakes fully applied, and back to fully
released. For those airplanes that may provide a number of independent
braking systems, which are not ``reliant'' on a stored energy system
for the demonstration of compliance with paragraph (b)(1) of this
section, but which perhaps incorporate a stored energy device, this
requirement is not applicable. It would be unreasonable that the
requirement for a minimum energy capacity and the provision of means to
indicate the level of stored energy to the flightcrew should be
maintained, particularly if its failure would have a minimal
consequence on airplane or passenger safety.
In the event that an hydraulic accumulator is used for energy
storage and the gas pressurization depletes, a pressure indication
alone as currently required in JAR 25.735(i) would be inadequate
because it would not provide indication of such faults to the
flightcrew. In fact, the current typical flight deck presentation could
give a false sense of security to the crew because it would almost
inevitably indicate a satisfactory pressure, regardless of the real
situation. Consequently, the proposed rule would require a measure of
the stored energy, rather than pressure, to be presented to the
flightcrew.
The minimum level of stored energy required for the emergency/
standby braking means would be presented as a requirement rather than
as advisory material. In the majority of cases, this material has been
used as a virtual requirement in the past by airplane manufacturers and
regulatory authorities. The proposed change would potentially enhance
the current level of safety because the FAA is proposing to adopt a
common but not universal industry practice and an improvement over the
existing JAR rule. Applicable advisory material would be included in
the proposed new AC 25.735-1X.
Proposal 15. The FAA proposes to add a new Sec. 25.735(i), ``Brake
wear indicators,'' to read:
``(i) Brake wear indicators. Means must be provided for each brake
assembly to indicate when the heat sink is worn to the permissible
limit. The means must be reliable and readily visible.''
Discussion: In order to ensure, as far as is practicable, that the
brake heat sink is not worn beyond its allowable wear limits throughout
its operational life, it is considered necessary to provide some device
that can readily identify the fully worn limit of the heat sink. The
proposal reflects a requirement included in a series of airworthiness
directives issued between 1989 and 1994 to require establishment of
brake wear limits and to provide means to indicate the same. The
British Civil Aviation Authority (CAA) Specification No. 17
[[Page 43575]]
also specifies the provision of such an indicator, and the majority of
wheel and brake assembly designs include such a device. The proposed
rule would have no impact on the current level of safety, because the
FAA is proposing to adopt an existing industry practice. Appropriate
advisory information would be included in proposed AC 25.735-1X.
Proposal 16. The FAA proposes to add a new Sec. 25.735(j),
``Overtemperature burst prevention,'' a new Sec. 25.731(d),
``Overpressure burst prevention,'' and a new Sec. 25.731(e), ``Braked
wheels,'' to read as follows:
``Sec. 25.735(j) Overtemperature burst prevention. Means must be
provided in each braked wheel to prevent wheel failure and tire burst
that may result from elevated brake temperatures. Additionally, all
wheels must meet the requirements of Sec. 25.731(d).''
``Sec. 25.731(d) Overpressure burst prevention. Means must be
provided in each wheel to prevent wheel failure and tire burst that may
result from excessive pressurization of the wheel and tire assembly.''
``Sec. 25.731(e) Braked wheels. Each braked wheel must meet the
applicable requirements of Sec. 25.735.''
Discussion--Sec. 25.735(j): There is an existing requirement
(Sec. 25.729(f)) related to the protection of equipment in wheel wells
against the effects of bursting tires and a similar requirement is
stated in TSO-C26c, Wheels and Wheel-Brake Assemblies. JAR 25.729(f)
requires protection of equipment on the landing gear and in wheel wells
against tire burst and elevated brake temperatures, and a similar
requirement is stated in the ``Minimum Operational Performance
Specification for Wheels and Brakes on JAR Part 25 Civil Aeroplanes''
(Document ED-69). However, there is no direct requirement in either
part 25 or JAR-25 that means must be provided to prevent wheel failure
and tire burst that could result from elevated brake temperatures. As a
result, it has become an industry practice to incorporate pressure
release device(s) that function as a result of elevated wheel
temperatures to deflate the tires. Nevertheless, it is believed to be
both reasonable and prudent that such a requirement should be clearly
stated in the paragraph related to airplane brakes and braking systems.
The proposed requirement for temperature activated devices would not
impact the current level of safety. Applicable advisory information
would be included in proposed AC 25.735-1X.
Discussion--Sec. 25.731(d): Wheel failure and tire burst due to
over-inflation presents a hazard to ground personnel and the airplane.
Certain airplane manufacturers require wheel pressure release devices
that reduce this hazard. This is considered a safety issue requiring
the incorporation of these devices. Incorporation of pressure release
devices in tire inflation equipment is not considered adequate due to a
history of misuse resulting in serious injuries or fatalities.
Installation in the wheel reduces the potential for tampering or misuse
and insures proper levels of protection. The proposed change would
retain and potentially enhance the current level of safety. Applicable
advisory information would be included in proposed AC 25.735-1X.
Discussion--25.731(e): This section contains regulations applicable
to all airplane wheels. If the wheel is braked, additional regulations
apply, which are contained in Sec. 25.735. Section 25.731(e) is added
to provide a cross-reference to those additional requirements. The
proposed change would retain and potentially enhance the current level
of safety.
Proposal 17. The FAA proposes to add a new Sec. 25.735(k),
``Compatibility,'' to read:
``(k) Compatibility. Compatibility of the wheel and brake
assemblies with the airplane and its systems must be substantiated.''
Discussion: Reliable and consistent brake system performance can be
adversely affected by incompatibilities within the system and with the
landing gear and the airplane. As part of the overall substantiation of
safe and anomaly free operation, it is necessary to show that no unsafe
conditions arise from incompatibilities between the brakes and brake
system with other airplane systems and structures. Areas such as
antiskid tuning, landing gear dynamics, tire type and size, brake
combinations, brake characteristics, brake and landing gear vibrations,
etc., need to be explored and corrected if necessary. Therefore, this
requirement is introduced to address these issues which are normally
covered by airplane manufacturers during development of the airplane
and must be addressed by modifiers of the equipment. Incorporation of
this requirement would potentially enhance the current level of safety.
Appropriate advisory information would be included in proposed AC
25.735-1X.
Paperwork Reduction Act
In accordance with the Paperwork Reduction Act of 1995 (44 U.S.C.
3507(d)), the FAA has determined that there are no requirements for
information collection associated with this proposed rule.
Compatibility With ICAO Standards
In keeping with U.S. obligations under the Convention on
International Civil Aviation, it is FAA policy to comply with
International Civil Aviation Organization (ICAO) Standards and
Recommended practices to the maximum extent practicable. The FAA has
determined that there are no ICAO Standards and Recommended Practices
that correspond to these proposed 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 (OMB) directs agencies to assess the
effect of regulatory changes on international trade. In conducting
these analyses, the FAA has determined that this proposed rule is not
``a significant regulatory action'' under section 3(f) of Executive
Order 12866 and, therefore, is not subject to review by OMB. 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.
Although numerous revisions would be made to Sec. 25.735, only one
would impose additional quantified costs for both part 25 large and
small airplane manufacturers (see below--proposal 11). One ARAC member,
a manufacturer of part 25 small airplanes, claimed that proposals 7,
14, and 16 would also impose incremental costs, but provided no
specific estimates (these proposals are also discussed below).
Essentially all of the changes codify current industry practice or
conform 14 CFR 25.735 to corresponding sections of the JAR. Adoption of
the proposed changes would increase harmonization and commonality
between American and European airworthiness standards, thus enhancing
safety. Harmonization would eliminate unnecessary duplication of
[[Page 43576]]
airworthiness requirements, thus reducing manufacturers' certification
costs (6 substantive proposals out of 17 total in the subject NPRM
would essentially mirror the proposed European standards; the 11 others
would not differ significantly). The FAA believes the enhanced safety
benefits and harmonization cost savings would exceed the relatively low
incremental costs of the proposed rule (see Summary of Costs and
Benefits section below).
Proposal 7. Changes regarding parking brake control and cockpit
indication of the brake essentially reflect current industry practice
for the majority of part 25 manufacturers; consequently, there are no
expected incremental costs. As noted above, one manufacture of part 25
small airplanes, however, indicated that its current designs do not
meet this requirement and that costs for cockpit indication in future
designs would, in fact, be incremental. The manufacturer, however, did
not provide such costs to the FAA. The FAA invites that manufacture
(and/or other interested parties) to provide detailed cost estimates
during the public comment period.
Proposal 11. One ARAC member, a manufacturer of part 25 large
airplanes, notes that the average impact of the 10 percent residual
rejected takeoff energy requirement would be a 2 to 3 percent increase
in the brake's energy absorption requirements. Notwithstanding, this
increase is smaller than the tolerances on its ability to define brake
requirements and the brake manufacturer's conformance to the
specifications. Also, higher residual energies would enable the
manufacturer to raise its recommended brake temperatures for dispatch,
so any potential higher brake costs would be offset by more efficient
aircraft operation (shorter turnaround times, less time at gate waiting
for brakes to cool).
The term ``most severe landing stop'' (MSL) would be added to
address cases such as immediate return to land after takeoff where the
brake energy for a flaps up landing may exceed that corresponding to
the accelerate-stop energy. The MSL requirement, while a new FAA
requirement, has been in effect in Europe (per British CAA);
consequently, many large part 25 airplane manufacturers currently meet
this standard. Notwithstanding, large part 25 airframe and brake
manufacturers note that in almost all cases either the MSL stop energy
would not exceed the maximum kinetic energy accelerate-stop energy, or
the MSL stop condition is extremely improbable. One part 25 large
airplane manufacturer, however, noted that demonstrating adherence to
this requirement for its typical airplane model would add the
equivalent of two additional high-energy dynamometers tests in which
the test brake would be destroyed; estimated incremental one-time costs
for this equal approximately $60,000 per type certification. Another
manufacturer, however, estimates only one test in the $20,000-$40,000
range. Manufacturers of small part 25 airplanes would experience some
incremental one-time testing costs totaling approximately $20,000 per
type certification.
The aforementioned nonrecurring costs for either the part 25 large
or small airplane type certification would easily be offset by the
harmonization cost savings cited earlier. Any potential safety benefits
from avoiding even one minor accident would add to such benefits. The
FAA therefore finds proposal 11 to be cost beneficial.
Proposal 14. As the stored energy requirement reflects current
industry practice for most part 25 manufacturers, there would be no
expected incremental costs associated with it. However, the same
manufacturer (of part 25 small airplanes) that reported potential costs
for proposal 7, also indicated that its current designs do not include
usable stored energy indication, and compliance with this requirement
in future designs would impose incremental costs. Detailed cost
estimates, however, were not provided. The FAA requests that the
manufacturers (or others) provide detailed costs estimates during the
public comment period.
Proposal 16. In the last several years, many wheel manufacturers
have included pressure release devices in most new production wheels in
order to avoid potential liability. Codification of existing industry
practice would ensure that the enhanced level of safety is retained.
There are no expected incremental costs associated with this proposal
since it does reflect current industry practice. However, the same
manufacturer (of part 25 small airplanes) that, in contrast to other
manufacturers, reported potential costs for proposals 7 and 14
indicated that the requirement for wheel pressure release devices would
also impose incremental costs in future designs. Again, the FAA invites
that manufacturer (or others) to provide detailed cost estimates during
the public comment period.
Summary of Costs and Benefits
As delineated above, and barring more detailed information for
proposals 7, 14, and 16, the FAA concludes that only proposal 11 would
result in incremental costs attributable to the subject NPRM.
Demonstrating adherence to the MSL requirement would increase
nonrecurring testing costs from $20,000-$60,000 for a part 25 large
airplane type certification; the amount for a part 25 small airplane
type certification is estimated to be $20,000. According to one
manufacturer, cost savings from harmonization, in terms of avoiding
added costs of coordination and documentation (with the JAA and
involving, for example, additional travel overseas, reports, etc.)
would be equal to or greater than the maximum incremental cost of
$60,000. The FAA believes that potential safety benefits resulting form
specification of minimum accepted standards would supplement these
cost-savings. Although there were numerous (approx. 170) accidents
involving brake failures during landings in the period 1982-1995, none
were determined to have been directly preventable by the subject
provisions. Different designs in future type certifications, however,
could present other problems (unexpected) and raise future accident
rates. This proposed rule is expected to reduce the chances of future
accidents by codifying in 14 CFR part 25 (and therefore making
mandatory) what was prevailing, but not necessarily universal, industry
practice.
For the reasons specified, the FAA finds the proposed rule to be
cost-beneficial.
Initial Regulatory Flexibility Determination
The Regulatory Flexibility Act of 1980 (RFA) 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, organizations, and governmental jurisdictions subject to
regulation.'' To achieve that principle, 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 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
[[Page 43577]]
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 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 proposed rule would affect manufacturers of part 25 transport
category airplanes produced under future new airplane type
certifications. For manufacturers, a small entity is one with 1,500 or
fewer employees. No part 25 airplane manufacturer has 1,500 or fewer
employees. Notwithstanding, the relatively low annualized incremental
certification costs are not considered significant within the meaning
of the RFA. Consequently, the FAA certifies that the proposed rule
would not have a significant economic impact on a substantial number of
manufacturers identified as small entities.
International Trade Impact Statement
The provisions of this proposed rule would have little or no impact
on trade for U.S. firms doing business in foreign countries and foreign
firms doing business in the United States.
This proposed rule is a direct action to respond to this policy by
increasing the harmonization of the U.S. Federal Aviation Regulations
with the European Joint Aviation Requirements. The result would be a
positive step toward removing impediments to international trade.
Federalism Implications
The regulations proposed herein would not have a substantial direct
effect 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.
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 1 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) or 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 1 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
develop 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 in any 1 year.
Environmental Analysis
FAA 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 action 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.
Regulations Affecting Intrastate Aviation in Alaska
Section 1205 of the FAA Reauthorization Act of 1996 (110 Stat.
3213) requires the Administrator, when modifying regulations in Title
14 of the CFR in manner affecting intrastate 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 intrastate aviation in Alaska. The FAA therefore
specifically requests comments on whether there is justification for
applying the proposed rule differently to intrastate operations in
Alaska.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
The Proposed Amendment
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, 44704.
2. Amend Sec. 25.731 to add new paragraphs (d) and (e) to read as
follows:
Sec. 25.731 Wheels.
* * * * *
(d) Overpressure burst prevention. Means must be provided in each
wheel to prevent wheel failure and tire burst that may result from
excessive pressurization of the wheel and tire assembly.
(e) Braked Wheels. Each braked wheel must meet the applicable
requirements of Sec. 24.735.
3. Revise Sec. 25.735 to read as follows:
Sec. 25.735 Brakes and braking systems.
(a) Approval. Each assembly consisting of a wheel(s) and brake(s)
must be approved.
(b) Brake system capability. The brake system, associated systems
and components must be designed and constructed so that:
(1) If any electrical, pneumatic, hydraulic, or mechanical
connecting or transmitting element fails, or if any single source of
hydraulic or other brake operating energy supply is lost, it is
possible to bring the airplane to rest with a braked roll stopping
distance of not more than two times that obtained in determining the
landing distance as prescribed in Sec. 25.125.
(2) Fluid lost from a brake hydraulic system following a failure
in, or in the vicinity of, the brakes is insufficient to cause or
support a hazardous fire on the ground or in flight.
(c) Brake controls. The brake controls must be designed and
constructed so that:
(1) Excessive control force is not required for their operation.
[[Page 43578]]
(2) If an automatic braking system is installed, means are provided
to:
(i) Arm and disarm the system, and
(ii) Allow the pilot(s) to override the system by use of manual
braking.
(d) Parking brake. The airplane must have a parking brake control
that, when selected on, will, without further attention, prevent the
airplane from rolling on a dry and level paved runway when the most
adverse combination of maximum thrust on one engine and up to maximum
ground idle thrust on any, or all, other engine(s) is applied. The
control must be suitably located or be adequately protected to prevent
inadvertent operation. There must be indication in the cockpit when the
parking brake is not fully released.
(e) Antiskid system. If an antiskid system is installed:
(1) It must operate satisfactory over the range of expected runway
conditions, without external adjustment.
(2) It must, at all times, have priority over the automatic braking
system, if installed.
(f) Kinetic energy capacity. The design landing stop, the maximum
kinetic energy accelerate-stop, and the most severe landing stop brake
kinetic energy absorption requirements of each wheel and brake assembly
must be determined. It must be substantiated by dynamometer testing
that, at the declared fully worn limit(s) of the brake heat sink, the
wheel and brake assemblies are capable of absorbing not less than these
levels of kinetic energy. Energy absorption rates defined by the
airplane manufacturer must be achieved. These rates must be equivalent
to mean decelerations not less than 10 fps\2\ for the design landing
stop and 6 fps\2\ for the maximum kinetic energy accelerate stop. The
most severe landing stop need not be considered for extremely
improbable failure conditions or if the maximum kinetic energy
accelerate-stop energy is more severe. Design landing stop is an
operational landing stop at maximum landing weight. Maximum kinetic
energy accelerate-stop is a rejected takeoff for the most critical
combination of airplane takeoff weight and speed. Most severe landing
stop is a stop at the most critical combination of airplane landing
weight and speed.
(g) Brake condition after high kinetic energy dynamometer stop(s).
Following the high kinetic energy stop demonstration(s) required by
paragraph (f) of this section, with the parking brake promptly and
fully applied for at least three (3) minutes, it must be demonstrated
that for at least five (5) minutes from application of the parking
brake, no condition occurs (or has occurred during the stop), including
fire associated with the tire or wheel and brake assembly, that could
prejudice the safe and complete evacuation of the airplane.
(h) Stored energy systems. An indication to the flightcrew of the
usable stored energy must be provided if a stored energy system is used
to show compliance with paragraph (b)(1) of this section. The available
stored energy must be sufficient for:
(1) At least six (6) full applications of the brakes when a
antiskid system is not operating; and
(2) Bringing the airplane to a complete stop when an antiskid
system is operating, under all runway surface conditions for which the
airplane is certificated.
(i) Brake wear indicators. Means must be provided for each brake
assembly to indicate when the heat sink is worn to the permissible
limit. The means must be reliable and readily visible.
(j) Overtemperature burst prevention. Means must be provided in
each braked wheel to prevent wheel failure and tire burst that may
result from elevated brake temperatures. Additionally, all wheels must
meet the requirements of Sec. 25.731(d).
(k) Compatibility. Compatibility of the wheel and brake assemblies
with the airplane and its systems must be substantiated.
Issued in Washington, DC, on August 3, 1999.
Ronald T. Wojnar,
Deputy Director, Aircraft Certification Service.
[FR Doc. 99-20518 Filed 8-9-99; 8:45 am]
BILLING CODE 4910-13-M
