[Federal Register Volume 67, Number 79 (Wednesday, April 24, 2002)]
[Rules and Regulations]
[Pages 20414-20421]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-9845]



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Part VI





Department of Transportation





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Federal Aviation Administration



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14 CFR Part 25



Revision of Braking Systems Airworthiness Standards to Harmonize With 
European Airworthiness Standards for Transport Category Airplanes; 
Final Rule and Notice

  Federal Register / Vol. 67, No. 79 / Wednesday, April 24, 2002 / 
Rules and Regulations  

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

[14 CFR Part 25]

[Docket No. FAA-1999-6063; Amendment No. 25-107]
RIN 2120-AG80


Revision of Braking Systems Airworthiness Standards to Harmonize 
With European Airworthiness Standards for Transport Category Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: This amendment revises the braking systems design and test 
requirements of the airworthiness standards for transport category 
airplanes. The amendment moves some of the existing regulatory text, 
considered to be of an advisory nature, to an advisory circular and 
adds regulations addressing automatic brake systems, brake wear 
indicators, pressure release devices, and system compatibility. These 
revisions were developed in cooperation with the Joint Aviation 
Authorities (JAA) of Europe, Transport Canada, and the U.S. and 
European aviation industry through the Aviation Rulemaking Advisory 
Committee (ARAC). These changes 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: Effective May 24, 2002.

FOR FURTHER INFORMATION CONTACT: Mahinder K. Wahi, FAA, Propulsion/
Mechanical Systems Branch, ANM-112, Transport Airplane Directorate, 
1601 Lind Avenue SW., Renton, WA 98055-4056; telephone (425) 227-2142; 
facsimile (425) 227-1320, e-mail [email protected].

SUPPLEMENTARY INFORMATION:

Availability of Rulemaking Documents

    You can get an electronic copy using the Internet by taking the 
following steps:
    (1) Go to the search function of the Department of Transportation's 
electronic Docket Management System (DMS) Web page (http://dms.dot.gov/search).
    (2) On the search page type in the last four digits of the Docket 
number shown at the beginning of this notice. Click on ``search.''
    (3) On the next page, which contains the Docket summary information 
for the Docket you selected, click on the document number for the item 
you wish to view.
    You can also get an electronic copy using the Internet through the 
Office of Rulemaking's web page at http://www.faa.gov/avr/armhome.htm 
or the Federal Register's web page at http://www.access.gpo.gov/su_docs/aces/aces140.html.
    You can also get a copy 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. Make 
sure to identify the amendment number or docket number of this 
rulemaking.

Small Business Regulatory Enforcement Fairness Act

    The Small Business Regulatory Enforcement Fairness Act (SBREFA) of 
1996 requires FAA to comply with small entities' requests for 
information or advice about compliance with statutes and regulations 
within its jurisdiction. Therefore, any small entity that has a 
question regarding this document may contact their local FAA official, 
or the person listed under FOR FURTHER INFORMATION CONTACT. You can 
find out more about SBREFA on the internet at our site, http://www.faa.gov/avr/arm/sbrefa.htm. For more information on SBREFA, e-mail 
us [email protected].

Background

    This amendment is based on Notice of Proposed Rulemaking (NPRM) No. 
99-16, which was published in the Federal Register on August 10, 1999 
(64 FR 43570) and Supplemental Notice of Proposed Rulemaking (SNPRM) 
No. 99-16A, which was published in the Federal Register on December 18, 
2000 (65 FR 79298). The related background leading to NPRM No. 99-16, 
and SNPRM No. 99-16A is discussed below.
    In 1988, the FAA, in cooperation with the Joint Aviation Authority 
(JAA) and other organizations representing the American and European 
aerospace industries, began a process to harmonize the airworthiness 
requirements of the United States and the airworthiness requirements of 
Europe, especially in the areas of Flight Test and Structures. Starting 
in 1992, the FAA harmonization effort for various systems related 
airworthiness requirements was undertaken by the ARAC. An ARAC working 
group of industry and government braking systems specialists of Europe, 
the United States, and Canada was chartered and named as the Braking 
System Harmonization Working Group (HWG) by notice in the Federal 
Register (59 FR 30080, June 10, 1994).

Statement of the Problem

    The ARAC 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 (AC), concerning 
new or revised requirements and the associated test conditions for 
wheels, brakes and braking systems, installed in transport category 
airplanes (Secs. 25.731 and 25.735). The harmonization task was 
completed by the ARAC working group and recommendations were submitted 
to the FAA by letter dated May 1, 1998. The FAA concurred with the 
recommendations and proposed them in NPRM No. 99-16. A Notice of 
Availability of proposed AC 25.735-1X and request for comments, and a 
Notice of Availability of proposed TSO-C135 and request for comments, 
were also published in the Federal Register on August 10, 1999 (64 FR 
43579). On August 25, 1999, the JAA issued a Notice of Proposed 
Amendment (NPA) 25D-291 and NPA TSO-7: ``Brakes and Braking Systems,'' 
which included the proposed advisory material joint (AMJ) 25.735. The 
amendments proposed in NPA 25D-291 and the advisory material proposed 
in AMJ 25.735 were substantively the same as the amendments proposed by 
the FAA in Notice No. 99-16 and the advisory material in proposed AC 
25.735-1X. The NPA TSO-7 was substantively the same as proposed in FAA 
TSO-C135.
    As a result, the FAA received comments from the public in response 
to the proposed rule (Notice No. 99-16), as well as comments on the 
proposed AC and the proposed TSO. The JAA received comments from the 
public in response to NPA 25D-291 and NPA TSO-7 (which includes the AMJ 
25.735). The comments received on the FAA and the JAA notices are 
interlinked and addressed jointly. Therefore, the FAA has considered 
both sets of comments in preparing the final rule contained herein, the 
new AC, and the new TSO. The FAA will publish a Notice of Availability 
in the Federal Register when the final version of AC 25.735-1 and TSO-
C135 are issued. Interested persons have been given an opportunity to 
participate in this

[[Page 20415]]

rulemaking, and due consideration has been given to all matters 
presented.
    The FAA determined that an incremental cost identified by 
commenters to Notice No. 99-16 must be subject to public scrutiny. 
Therefore, this resulted in a supplemental notice of proposed 
rulemaking (SNPRM), No. 99-16A, being published for public comment on 
December 18, 2000 (65 FR 79278).
    Comments received on Notice No. 99-16 are discussed first, followed 
by comments received on Notice No. 99-16A.

Discussion of Comments: Notice No. 99-16

    Twenty-one commenters responded to the request for comments 
contained in Notice No. 99-16, the notices of availability of proposed 
AC 25.735-1, and TSO-C135, and the corresponding JAA documents NPA 25D-
291, NPA TSO-7, and AMJ 25.735.
    Comments were received from eight foreign and domestic airplane and 
brake manufacturers, nine foreign airworthiness authorities, one 
operator, and three foreign and domestic industry organizations. The 
majority of the commenters agree with the proposal and recommend its 
adoption. However, some commenters disagree with the proposal while 
providing alternative proposals that appear to merit further 
consideration by ARAC. Therefore, the FAA tasked the ARAC on Transport 
Airplane and Engine (TAE) issues area by letter dated February 8, 2000, 
to consider the comments and provide recommendations for the 
disposition of the comments along with any recommendations for changes 
to the proposal. The disposition of the comments below is based on the 
agreement reached by the Braking Systems HWG and submitted by ARAC on 
TAE issues area to the FAA by letter dated June 19, 2000. Several of 
the commenters address multiple issues, while many commenters address 
the same issue. As a result, the FAA responses to the comments are 
organized by individual comment under each proposal, i.e., proposals 1 
through 17.

Proposals 1, 2, 4, 5, 6, 8, 9, 12, 15, and 17: Secs. 25.735(a), (b), 
(c), (c)(2), (e), (e)(1), (g), (i) and (k)

    No comments were received for these proposals. Sections 25.735(a), 
(c), (c)(2), (e), (e)(1), (g), (i), and (k) are therefore adopted as 
proposed.

Proposal 3, Sec. 25.735(b)

    One commenter questions the justification of deleting the 
parenthetical phrase ``(excluding the operating pedal or handle)'' from 
the current Sec. 25.735(b). The commenter states that excluding the 
operating pedal or handle is justified to allow use of maximum 
asymmetric braking capability, use of auto-brakes, and/or thrust 
reversers in stopping scenarios involving a jammed pedal or high rudder 
deflection.
    FAA's Response: The FAA disagrees with the commenter. Currently, 
certified airplanes can meet this requirement using rudder and 
nosewheel steering while providing full braking on one side of the 
airplane without reverse thrust or autobrakes. The regulations do not 
require consideration of adverse crosswinds.

Proposal 7, Sec. 25.735(d)

    One commenter recommends deleting the idle thrust requirement as 
use of idle thrust may result in nose gear sliding on high thrust twin 
engine aircraft. The commenter's suggested text is ``Thrust on any, or 
all, other engine(s) is to be determined by the applicant.''
    FAA's Response: The FAA disagrees with the commenter. The rule, as 
stated, does not preclude the use of thrust in excess of idle on other 
engines. The advisory material is expanded to state that compliance is 
not limited to ground idle thrust; therefore, the applicant may choose 
what is critical.

Proposal 10, Sec. 25.735(e)(2)

    One commenter states that the intent of the rule could probably be 
better expressed by changing the text from ``(2) It must, at all times, 
have priority over the automatic braking system, if installed'' to ``If 
both Anti-Skid and Auto-Brake systems are fitted to the aircraft, then 
the anti-skid system shall always work independently of the auto-brake 
and irrespective of the auto-brake configuration/status.''
    FAA's Response: The FAA does not concur with the comment. The 
intent of the rule is to make sure the antiskid function releases a 
wheel which is going into a skid regardless if the braking is commanded 
by the pilot or the autobrake function. An explanation to this effect 
is added in the AC.

Proposal 11, Sec. 25.735(f)

    For the comments and response that follow, the heat sink is the 
mass of the brake that is primarily responsible for absorbing energy 
during a stop. For a typical brake, this would consist of the 
stationary and rotating disc assemblies. One commenter states: ``It 
does not appear that the proposed Sec. 25.735(f) requires the brake 
with fully worn heat sink to complete 100 cycles of the design landing 
stop. A brake assembly with fully worn heat sink will not be capable of 
completing these 100 landing stops. If the proposed Sec. 25.735(f) 
requires the wheel and brake assembly with fully worn heat sink to 
complete ONE design landing stop dynamometer test, this test would be 
unnecessary since the maximum kinetic energy accelerate-stop test will 
be much more severe. The energy capacity of the accelerate-stop is 
generally three times the energy capacity of the design landing stop.''
    FAA's Response: The FAA concurs; the proposed TSO-C135 does not 
require the brake with fully worn heat sink to complete 100 cycles of 
the design landing stop. However, the FAA disagrees that one design 
landing stop with fully worn brakes is unnecessary; it is required 
because the one design landing stop requirement cannot be met by the 
worn brake accelerate-stop test due to differing deceleration 
requirements.
    The same commenter also states that ``the most severe landing stop 
should not be added until this new regulation is harmonized with other 
part 25 sections, especially subpart B-Flight (Performance) and 
Sec. 25.1001, Fuel jettisoning system.''
    FAA's Response: The FAA does not agree. The Sec. 25.775(f)(3) 
requirement is for brake qualification via a dynamometer test per TSO-
C135 standard, and not a flight performance test on the aircraft. 
Compliance with the current Sec. 25.1001 may also result in similar 
design requirements, especially for aircraft without fuel jettisoning 
systems.
    A second commenter, while supporting the general intent of 
harmonizing, expresses a concern

with some aspects of the proposed rule that create significant 
additional constraints on braking system design and other systems 
architecture, and on compliance demonstration, without any clear 
safety benefit. In particular, the Summary of Costs and Benefits in 
the NPRM preamble, indicates a type certification testing cost 
increase from $20,000-$60,000, resulting from proposal 11 on ``most 
severe landing stop'' that would be balanced by the savings expected 
from rule harmonization. Then this summary adds considerations on 
potential safety benefits: ``Although there were numerous 
(approximately 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.''

    The commenter concludes ``that, in fact, the expected safety 
benefit is so

[[Page 20416]]

vague that it is hard to justify the additional certification expenses, 
even if balanced by administrative simplifications, especially for a 
technically questionable requirement.''
    FAA's Response: The FAA does not agree with this commenter. The 
requirement is conditional in that ``it need not be considered for 
extremely improbable failure conditions or if the maximum kinetic 
energy accelerate-stop energy is more severe.'' Without specifying it 
in the regulations, the applicant may not consider such a situation, 
however likely.
    The second commenter continues, adding: ``Contrary to what is 
indicated in the Regulatory Evaluation Summary, the Most Severe Landing 
Stop (MSL) requirement has not been in effect in Europe per British 
Civilian Aviation Authority (CAA), and there is no evidence that `many 
large part 25 airplane manufacturers currently meet this standard.' '' 
The JAR-25 does not contain this concept. Before JAR-25 adoption, 
British Civil Airworthiness Requirments (BCAR) Section D was the U.K. 
Certification code for large airplanes. The brake energy absorption 
capacity was based on different concepts, namely Certified Normal Brake 
Energy Capacity and Certified Emergency Brake Energy Capacity (BCAR 
chapter D-4-5, Sec. 3.8). It is meaningless to determine a ``most 
severe landing stop'' case for the sole purpose of brake system 
certification, without considering the global use of return to land 
capability that will take into account such other parameters as 
controllability, other retardation means, landing distances, and 
operational procedures. The commenter therefore suggests withdrawal of 
the MSL concept, and proposes modifying paragraph (f) in Sec. 25.735 as 
follows:
    (1) Replace the first sentence with: ``Kinetic energy absorption 
requirements of each wheel and brake assembly must be determined for 
the design landing stop and the maximum kinetic energy accelerate-
stop.''
    (2) Delete the last sentence: ``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.''
    (3) Replace the last sentence with: ``In addition to the design 
landing stop and maximum kinetic energy accelerate-stop, the brake 
energies associated with forseeable cases of immediate return to land 
must also be considered. For these cases, operational procedures, 
possible fuel jettisoning for a maximum of 15 minutes, use of 
retardation means, and landing distances must be taken into account.''
    The same recommendations, (1), (2), and (3) above, are made by a 
third commenter who states that ``the concept of an MSL is inter-
related to an FAA document regarding Return Landing Capability (Issue 
Paper F-7), and a recent recommendation No. 99-23 from the UK Air 
Accidents Investigation Branch (AAIB).'' A fourth commenter, the UKCAA, 
states that the AAIB recommendation is a result of a serious incident 
at London Heathrow airport in July 1998. An aircraft, following 
illumination of a caution light during climb and shutdown of one 
engine, returned for an overweight landing in a crosswind. During this 
landing, the brakes overheated, the tires deflated, and the aircraft 
went off the runway. The third commenter continues, stating that the 
problem of aircraft retardation in foreseeable abnormal operating 
conditions cannot be adequately addressed by looking at the brakes and 
brake system alone. The third commenter recommends (1) that this 
proposal should be reassessed in view of the other current regulatory 
activity (Issue Paper F-7 and AAIB recommendation No. 99-23); and (2) 
rewording the regulation per recommendations (1), (2), and (3), above.
    FAA's Response: The FAA does not agree. The FAA has reviewed the 
recommendation and determined that prior to the formation of the ARAC 
Braking Systems HWG, the requirement for the most severe landing stop 
condition was included in the European JAA-industry harmonized document 
ED-69, published in December 1992. In addition, as pointed out by two 
other commenters, an existing FAA issue paper (FAA Issue Paper F-7) has 
required applicants to address a return landing capability condition 
for compliance with Sec. 25.1001. This means the applicant should 
address the effects and consequences of typical single and multiple 
failure conditions which are foreseeable events and can necessitate 
landings at abnormal speeds and weights. The most severe landing stop 
requirement is therefore retained.
    The AAIB recommendation specifically states that the FAA, CAA, and 
JAA review the requirements for aircraft brake system certification to 
cover the need to consider overweight landing situations, together with 
the effects of crosswind and asymmetric engine thrust during ground 
roll.
    The commenter references the existing FAA Issue Paper F-7 on this 
subject that indicates that the FAA too see the need to expand the 
scope of the requirement. The commenter continues stating that the FAA 
position seems to indicate that this incident would be regarded as a 
``foreseeable operating condition'' when considering compliance with 
Sec. 25.1309(a).
    In accordance with the AAIB Safety Recommendation, the fourth 
commenter (UKCAA) proposes that JAR 25.735(f) be further amended to 
include consideration of crosswind and asymmetric engine thrust, in 
combination with the severe landing stop condition maximum weight.
    FAA's Response: The FAA does not concur with this comment. The FAA 
has reviewed the UKCAA recommendation and considers that there is 
sufficient conservatism in the proposed requirements. This 
conservatism, while not provided specifically to accommodate the 
possible crosswind effects in an overweight return to land case, is 
nevertheless available as follows:
    (a) The capability to stop the aircraft with only half the brakes 
functioning;
    (b) Dynamometer testing to demonstrate the capability to complete 
the maximum kinetic energy rejected takeoff (RTO) stop with all brakes 
worn to the limit;
    (c) Dynamometer testing to demonstrate the capability to complete 
the most severe landing stop with all brakes worn to the limit, should 
this be more severe than the maximum kinetic energy RTO stop, and not 
shown to be extremely improbable;
    (d) No allowance being given for the reverse thrust capabilities 
for the demonstration of (b) and (c) above.
    The FAA has added appropriate advisory material to the AC 25.735-1, 
Brakes and Braking Systems Certification Tests and Analysis.
    A fifth commenter suggests changing the wording of the second 
sentence of Sec. 25.735(f) from ``* * * most severe landing stop brake 
kinetic energy absorption requirements of each wheel and brake assembly 
* * *'' to ``* * * most severe landing stop kinetic energy absorption 
requirements of each brake-wheel-tire assembly * * *'' The commenter 
suggests the same change in terminology for the third sentence.
    FAA's Response: The FAA concurs with the commenter. The final rule 
text is revised accordingly.
    A sixth commenter states that, as proposed, Sec. 25.735(f) is 
difficult to read and contains too many separate requirements, which 
could create undue difficulties during the finding of compliance. The 
commenter suggests that the paragraph be rearranged such that:

[[Page 20417]]

    (1) There is a distinct sub-paragraph that can be identified for 
the requirement for the determination of the levels of kinetic energy 
and the energy absorption rates. This should indicate that three cases 
are to be considered (design landing stop, accelerate-stop and most 
severe landing stop). This sub-paragraph could also mention the caveats 
about the need to consider, or not consider, during testing the most 
severe landing stop.
    (2) There is a distinct sub-paragraph for the requirement for the 
wheel and brake assembly to meet the levels of kinetic energy.
    (3) There is a distinct sub-paragraph for the requirement for the 
wheel and brake assembly to meet the energy absorption rates.
    (4) The definitions of the three stop cases (the last nine lines of 
the currently proposed paragraph, starting with: ``* * * Design landing 
stop is an operational * * *'') are taken out of the requirement and 
placed in the proposed AC 25.735-1X.
    FAA's Response: The FAA concurs with the commenter that rearranging 
Sec. 25.735(f) into three distinct sub-paragraphs clarifies the 
requirement. The FAA, however, has decided that it is more appropriate 
to retain the definitions as part of the regulatory text since this is 
the only place where these terms are identified. The text of this 
paragraph is divided into three subparagraphs (f)(1), (f)(2), and 
(f)(3) with appropriate headings. The subparagraphs cover each of the 
three tests and include the definitions.
    Two of the commenters suggest adding a requirement that the 
accelerate-stop test, reference: paragraph 3.3.3.2 of the proposed TSO-
C135 and Sec. 25.735(f) of Notice No. 99-16 must be completed on both a 
new brake and a fully worn brake. The fully worn brake is the worst 
case condition for energy absorption capability; however, the new brake 
condition is the worst case condition for performance for some heat 
sink materials.
    FAA's Response: The FAA concurs with these commenters. Applicable 
text in the final TSO-C135 paragraph 3.3.3.2, and the final rule new 
subparagraph Sec. 25.735(f)(2) add a new brake accelerate-stop test 
requirement with the new brake defined as a brake worn no more than 5 
percent of its usable wear range. The accelerate-stop applicable 
portion of Sec. 25.735(f) text, NPRM No. 99-16, is revised from: ``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'' 
to ``(f)(2): It must be substantiated by dynamometer testing that the 
wheel, brake, and tire assembly is capable of absorbing not less than 
this level of kinetic energy throughout the defined wear range of the 
brake.'' Although not a part of the TSO, large airplane manufacturers 
currently require a new brake RTO test as part of brake qualification. 
Small airplane manufacturers may experience a cost increase of $20,000 
per certification.

Proposal 13, Sec. 25.735(g)

    The first commenter wonders whether the case specified in the rule 
(immediate application of the parking brake after the RTO for at least 
3 minutes, with no fire allowed for at least 5 minutes) is indeed the 
worst case. The commenter opines that a more severe case, representing 
a likely in-service scenario, would be for the aircraft to taxi off the 
runway before the parking brake is applied, and that it should be 
allowable for the aircraft manufacturer to incorporate this scenario 
into the test if so desired. However, this is specifically precluded 
due to the current wording of the rule.
    FAA's Response: The FAA does not concur. The regulation does not 
preclude the applicant from considering such a scenario and addressing 
it in their brake specification.
    A second commenter states that as proposed under Sec. 25.735(g), it 
must be demonstrated that with the parking brake applied for three 
minutes after the high kinetic energy stop demonstration of 
Sec. 25.735(f), no condition (including fire) that could prejudice the 
safe and complete evacuation of the airplane shall occur for at least 
five minutes.
    The commenter continues, stating: ``In recent aircraft 
certification programs, Transport Canada (TC) has required that the 
parking brake be applied for a minimum of five minutes. This is a more 
stringent requirement that impacts the design, testing and 
certification of the braking system that is currently only being 
applied to Canadian certifications and is violating the premise of 
harmonization.''
    The commenter adds that ``the ARAC sub committee does not recommend 
the increased parking brake period, however, the significant issue is 
that all National Airworthiness Authorities must accept the same 
standard to realize the benefits of harmonization.''
    FAA's Response: The FAA agrees with the second commenter that 
clarification of the parking brake set period is needed. The FAA has 
reaffirmed the 3-minute parking brake applied period for the 
dynamometer test. There is no intent by the FAA to dictate that the 
parking brake must be released at 3 minutes, but that it must be 
applied at least that long. Figures 3-1 and 3-2 and paragraphs 3.3.3.5 
and 3.3.4.5 in the TSO will be changed to minimize ambiguity in this 
respect.
    The certification test on the airplane (worn brake RTO) need not 
follow the procedure prescribed in the TSO. But it is important that 
the brake manufacturer know early in the development period what 
procedure will be used on the airplane (i.e. the certification basis) 
since it can impact the design. This approach allows authorities that 
are not part of the harmonization process the needed flexibility.
    A third commenter adds that the new JAR 25.735(g) requires the 
parking brake to be promptly and fully applied for at least 3 minutes; 
in addition, it must be demonstrated that for at least 5 minutes no 
condition occurs that could prejudice the safe and complete evacuation 
of the airplane (a similar requirement is also included in JTSO-C135 
paragraph 3.3.3.5). Both the 3- and 5-minute timeframes, according to 
the proposals, are related to a safe evacuation of the airplane, 
however, there are no data to support the use of those figures. The 
commenter states that advice is needed from the Cabin Safety Study 
Group (CSSG) on the use of three and five minutes in conjunction to a 
safe evacuation.
    FAA's Response: The FAA does not agree that the CSSG advice is 
needed. The criteria are based on regulations for 90-second cabin 
evacuation; pilot recognition time; time to deploy slides; and time for 
fire trucks to arrive at the scene of the fire, as well as previous 
certification tests experience. If the CSSG changes the criteria (3 
minutes versus 5 minutes), then a change to Sec. 25.735(g) should be 
evaluated.

Proposal 14, Sec. 25.735(h)

    One commenter states that ``although this rule is only invoked if 
the aircraft relies on accumulators to provide back-up brake pressure, 
and this is generally not the case with AIRBUS aircraft, [the 
commenter] is not aware of an existing system that would satisfy this 
requirement. The display of available brake energy is a complex task, 
and a system would need to be devised to allow this information to be 
obtained.'' The commenter suggests that overall safety would probably 
be better enhanced by placing a reliability requirement on the 
accumulator system, rather than demanding a new monitoring system be 
developed which could degrade the system safety.
    FAA's Response: The FAA disagrees with this comment. Alternate 
means of

[[Page 20418]]

compliance will be discussed in AC 25-735-1. As explained in the 
preamble and advisory circular material, the intent is to ensure proper 
indication of available accumulator energy, not just pressure which has 
been determined to be insufficient indication. Unless available energy 
is displayed, there is no assurance that a backup system is available.

Proposal 16, Sec. 25.735(j)

    One commenter recommends that the proposed Sec. 25.735(j), 
Overtemperature burst prevention, should be moved to Sec. 25.731.
    FAA's Response: The FAA does not concur with this comment. The 
overtemperature condition is caused by brake heat and, therefore, needs 
to be addressed in the brake section. Cross references are provided in 
both Secs. 25.735 and 25.731.
    Another commenter suggests that the intent would be better 
expressed by changing the words ``* * * wheel failure or tire burst * * 
* '' to `` * * * wheel failure and/or tire burst * * *''
    FAA's Response: The FAA concurs that clarification is necessary. 
The final rule text is revised to read ``* * * a wheel failure, a tire 
burst, or both * * *''

Discussion of Comments: Notice No. 99-16A

    Five commenters responded to the request for comments contained in 
Notice No. 99-16A. Three commenters fully support the proposal and 
recommend its adoption. Two other commenters made recommendations as 
follows.
    The first commenter states ``Airplane braking systems differ 
between airplane models. Consideration must be given to the additional 
braking equipment, which is installed on certain model airplanes. When 
that additional equipment fails or has been rendered inoperative, a 
more critical condition can exist with the three proposed testing 
conditions for kinetic energy capacity, i.e., design landing stop, 
accelerate-stop, and most severe landing stop. This SNPRM does not 
account for model specific test qualifications for airplanes equipped 
with additional braking equipment such as brake fan systems. For 
example, the brake fan system on an airplane may be rendered 
inoperative due to system failure or by deactivation in accordance with 
the airplane minimum equipment list (AMEL). The lack of additional 
brake cooling, coupled with the additional mass (heat sink) of the 
brake fan, will further deteriorate conditions at the brake 
installation. Consequently, braking performance is reduced.'' 
Recognition of such abnormal conditions must be part of the 
qualification testing for kinetic energy capacity in all three proposed 
conditions.
    FAA's Response: The FAA does not concur with this comment. While 
the revised regulations do not specifically address items such as brake 
cooling fans, they provide the basic requirements that must be met. The 
final AC, once it is published, will provide information on how the 
regulations are applied. In the case of brake cooling fans, two 
paragraphs are appropriate. Paragraph 4a(1)(c) of the AC will state 
that the brake must meet the energy requirements without the use of 
auxiliary cooling devices. Paragraph 4f(2)(a) states that, in 
calculating the energy requirements for the accelerate-stop, use of 
cooling fans may not be considered in determining the heat sink state 
at the beginning of the stop. No change in the rule text is necessary.
    The second commenter recommends the following changes to 
Secs. 25.735(f)(2) and (f)(3) for consistency with Sec. 25.735(f)(1):
    ``(1) In Sec. 25.735(f)(2) remove the words `defined by the 
airplane manufacturer must be achieved,' and add the words, `derived 
from the airplane manufacturer's braking requirements must be 
achieved.' ''
    ``(2) In Sec. 25.735(f)(3), add the sentence `The energy absorption 
rate derived from the airplane manufacturer's braking requirements must 
be achieved.' ''
    FAA's Response: The FAA concurs with (1) and the final rule text 
has been revised accordingly. The FAA does not concur with (2) because 
the HWG specifically decided not to put a deceleration requirement on 
the most severe landing. Addition of the proposed sentence to 
Sec. 25.735(f)(3) is not necessary and doing so would not have any any 
impact on brake design.
    With the exceptions of the changes noted in Secs. 25.735(f) and 
(j), this final rule is adopted as proposed in Notice No. 99-16 and 
Notice No. 99-16A.

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 new requirements for 
information collection associated with this amendment.

International Compatibility

    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 regulations.

Regulatory Evaluation Summary, Regulatory Flexibility 
Determination, International Trade Impact Assessment, and Unfunded 
Mandates Assessment

    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 
Trade Agreements Act (19 U.S.C. 2531-2533) prohibits agencies from 
setting standards that create unnecessary obstacles to the foreign 
commerce of the United States. In developing U.S. standards, this Trade 
Act requires agencies to consider international standards, and, where 
appropriate, to use those standards as the basis of U.S. standards. 
Fourth, Title II of the Unfunded Mandates Reform Act of 1995 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 in any one year. In conducting these analyses, 
the FAA has determined that this rule: (1) Will generate benefits that 
justify its costs and is not ``a significant regulatory action( as 
defined in Executive Order 12866 or in the Department of 
Transportation's Regulatory Policies and Procedures; (2) will not have 
a significant impact on a substantial number of small entities; (3) 
will not constitute a barrier to international trade, and (4) does not 
contain a Federal intergovernmental or private sector mandate that 
exceeds $100 million in any one year.
    These analyses, available in the docket, are summarized below. All 
estimates are expressed in year 2000 dollars.

Regulatory Evaluation Summary

    None of the commenters to Notice No. 99-16 disputed FAA's estimates 
of specific incremental certification costs. One commenter, however, 
questioned FAA's contention that costs would be balanced by the savings 
expected from rule harmonization.

[[Page 20419]]

    In answer to that commenter's concerns, and based on industry 
experience with recent type certifications, the FAA re-calculated both 
the harmonization cost savings and the costs attributable to the 
``proposed'' amendments (in the original NPRM), and estimated the costs 
associated with the proposed new requirement in Notice No. 99-16A. 
These cost estimates are delineated in the next several paragraphs.
    Based on the previous analyses in the economic evaluations for both 
notices, the FAA has determined that only two changes in Sec. 25.735(f) 
Kinetic energy capacity, will result in any incremental cost increases; 
those are the dynamometer testing requirements in (f)(2) and (f)(3), 
pertaining to the ``Maximum kinetic energy accelerate-stop'' and the 
``Most severe landing stop (MSL),'' respectively.
    The dynamometer test, also called a new brake rejected takeoff 
test, is currently conducted by brake manufacturers as specified by 
large airplane manufacturers in the brake qualification specification 
and is an industry practice as such. For some small airplane 
manufacturers, however, the new ``accelerate-stop'' test will result in 
a cost increase of $20,000 per certification. This incremental, but 
nonrecurring, cost for some manufacturers of part 25 small airplanes 
will easily be offset by the harmonization cost savings cited below. 
Any potential safety benefits from avoiding even one minor accident 
would add to such benefits.
    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, estimates 
one additional dynamometer test in the $20,000-$40,000 range. 
Manufacturers of small part 25 airplanes will experience incremental 
one-time testing costs totaling approximately $20,000 per type 
certification.
    These incremental, but nonrecurring, costs for some manufacturers 
of part 25 (large and small) airplanes will easily be offset by the 
estimated harmonization cost savings. Any potential safety benefits 
from avoiding even one minor accident would add to such benefits.
    In summary, the incremental costs for the aforementioned new 
dynamometer tests will total between $20,000 and $40,000 per type 
certification for one manufacturer of part 25 large airplanes. Similar 
costs for some manufacturers of part 25 small airplanes are estimated 
at $40,000 per type certification.
    As stated in the Regulatory Evaluation Summary in Notice No. 99-
16A, the FAA had contacted industry sources to obtain estimated 
harmonization cost savings attributable to the revisions originally 
proposed in Notice No. 99-16. These cost savings are estimated to be, 
at a minimum, between $50,000 and $75,000 for a part 25 small airplane 
type certification and $100,000 to $300,000 for a part 25 large 
airplane type certification. These harmonization benefits exceeded the 
incremental costs of all the revisions specified in the NPRM as well as 
the costs attributable to the SNPRM change. Since there were no public 
comments to the SNPRM disputing these estimates, the FAA includes these 
same benefits in this final rule economic assessment. Given that the 
rule's incremental benefits exceed the incremental costs for both part 
25 large and small airplane manufacturers, the FAA finds the final rule 
cost-beneficial.

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 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 subject rule will 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. Consequently, the 
FAA certifies that the final rule will not have a ``significant 
economic impact on a substantial number of small entities'' 
(manufacturers).

International Trade Impact Assessment

    The Trade Agreement Act of 1979 prohibits Federal agencies from 
engaging in any standards or related activities that create unnecessary 
obstacles to the foreign commerce of the United States. Legitimate 
domestic objectives, such as safety, are not considered unnecessary 
obstacles. The statute also requires consideration of international 
standards and where appropriate, that they be the basis for U.S. 
standards. In accordance with the above statute, the FAA has assessed 
the potential effect of this final rule and has determined that it will 
eliminate regulatory differences between the airworthiness standards of 
the U.S. and the Joint Aviation Requirements of Europe, without 
affecting current industry practice. This is consistent with the Trade 
Agreement Act.

Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (the Act), 
enacted as Public Law 104-4 on March 22, 1995, requires each Federal 
agency, to the extent permitted by law, to prepare a written assessment 
of the effects of any Federal mandate in a proposed or final agency 
rule that may result in the expenditure by State, local, and tribal 
governments, in the aggregate, or by the private sector, of $100 
million or more (adjusted annually for inflation) in any one year. 
Section 204(a) of the Act, 2 U.S.C. 1534(a), requires the Federal 
agency to develop an effective process to permit timely input by 
elected officers (or their designees) of State, local, and tribal 
governments on a proposed ``significant intergovernmental mandate.'' A 
``significant intergovernmental mandate'' under the Act is any 
provision in a Federal agency regulation that will impose an 
enforceable duty upon State, local, and tribal governments, in the 
aggregate, of $100 million (adjusted annually for inflation) in any one 
year. Section 203

[[Page 20420]]

of the Act, 2 U.S.C. 1533, which supplements section 204(a), provides 
that before establishing any regulatory requirements that might 
significantly or uniquely affect small governments, the agency shall 
have developed a plan that, among other things, provides for notice to 
potentially affected small governments, if any, and for a meaningful 
and timely opportunity to provide input in the development of 
regulatory proposals. The FAA determines that this final rule does not 
contain a significant intergovernmental or private sector mandate as 
defined by the Act.

Executive Order 3132, Federalism

    The FAA has analyzed this final rule under the principles and 
criteria of Executive Order 13132, Federalism. We determined that this 
action will not have a substantial direct effect on the States, or the 
relationship between the national Government and the States, or on the 
distribution of power and responsibilities among the various levels of 
government. Therefore, we determined that this final rule does not have 
federalism implications.

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 a 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 final 
rule applies to the certification of future designs of transport 
category airplanes and their subsequent operation, it could affect 
intrastate aviation in Alaska. The Administrator has considered the 
extent to which Alaska is not served by transportation modes other than 
aviation, and how the final rule could have been applied differently to 
intrastate operations in Alaska. However, the Administrator has 
determined that airplanes operated solely in Alaska would present the 
same safety concerns as all other affected airplanes; therefore, it 
would be inappropriate to establish a regulatory distinction for the 
intrastate operation of affected airplanes in Alaska.

Environmental Analysis

    FAA Order 1050.1D defines FAA actions that may be categorically 
excluded from preparation of a National Environmental Policy Act (NEPA) 
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 final rule has been assessed in accordance 
with the Energy Policy and Conservation Act (EPCA) Public Law 94-163, 
as amended (42 U.S.C. 6362) and FAA Order 1053.1. It has been 
determined that the final rule is not a major regulatory action under 
the provisions of the EPCA.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

The Amendment

    In consideration of the foregoing, the Federal Aviation 
Administration amends Chapter I of Title 14, Code of Federal 
Regulations as follows:

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

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

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


    2. Amend Sec. 25.731 by adding 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. 25.735.

    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.
    (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 satisfactorily 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--(1) Design landing stop. The design 
landing stop is an operational landing stop at maximum landing weight. 
The design landing stop brake kinetic energy absorption requirement of 
each wheel, brake, and tire assembly must be determined. It must be 
substantiated by dynamometer testing that the wheel, brake and tire 
assembly is capable of absorbing not less than this level of kinetic 
energy throughout the defined wear range of the brake. The energy 
absorption rate derived from the airplane manufacturer's braking 
requirements must be achieved. The mean deceleration must not be less 
than 10 fps \2\.
    (2) Maximum kinetic energy accelerate-stop. The maximum kinetic 
energy accelerate-stop is a rejected takeoff for the most critical 
combination of airplane takeoff weight and speed. The accelerate-stop 
brake kinetic energy absorption requirement of each wheel, brake, and 
tire assembly must be determined. It must be substantiated by 
dynamometer testing that the wheel, brake, and tire assembly is capable 
of absorbing not less than this level of kinetic energy throughout the 
defined wear range of the brake. The energy absorption rate derived 
from the

[[Page 20421]]

airplane manufacturer's braking requirements must be achieved. The mean 
deceleration must not be less than 6 fps \2\.
    (3) Most severe landing stop. The most severe landing stop is a 
stop at the most critical combination of airplane landing weight and 
speed. The most severe landing stop brake kinetic energy absorption 
requirement of each wheel, brake, and tire 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, brake and tire 
assembly is capable of absorbing not less than this level of kinetic 
energy. 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.
    (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 3 minutes, it must be demonstrated that for 
at least 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 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.
    (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 a wheel failure, a tire burst, or both, 
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 Renton, Washington on April 10, 2002.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 02-9845 Filed 4-23-02; 8:45 am]
BILLING CODE 4910-13-P