[Federal Register Volume 63, Number 32 (Wednesday, February 18, 1998)]
[Rules and Regulations]
[Pages 8298-8321]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-3898]



[[Page 8297]]

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Part IV





Department of Transportation





_______________________________________________________________________



Federal Aviation Administration



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14 CFR Parts 1 et al.



Improved Standards for Determining Rejected Takeoff and Landing 
Performance; Final Rule Proposed Revisions to Advisory Circular--Flight 
Test Guide for Certification of Transport Category Airplanes; Notice

  Federal Register / Vol. 63, No. 32 / Wednesday, February 18, 1998 / 
Rules and Regulations  

[[Page 8298]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 1, 25, 91, 121, and 135

[Docket No. 25471; Amendment Nos. 1-48, 25-92, 91-256, 121-268, 135-71]
RIN 2120-AB17


Improved Standards for Determining Rejected Takeoff and Landing 
Performance

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: This action amends the airworthiness standards for transport 
category airplanes to: revise the method for taking into account the 
time needed for the pilot to accomplish the procedures for a rejected 
takeoff; require that takeoff performance be determined for wet 
runways; and require that rejected takeoff and landing stopping 
distances be based on worn brakes. The FAA is taking this action to 
improve the airworthiness standards, reduce the impact of the standards 
on the competitiveness of new versus derivative airplanes without 
adversely affecting safety, and harmonize with revised standards of the 
European Joint Aviation Requirements-25 (JAR-25). These standards, 
which affect manufacturers and operators of transport category 
airplanes, are not being applied retroactively to either airplanes 
currently in use or airplanes of existing approved designs that will be 
manufactured in the future.

EFFECTIVE DATE: March 20, 1998.

FOR FURTHER INFORMATION CONTACT:
Donald K. Stimson, FAA, Airplane & Flightcrew Interface Branch, ANM-
111, Transport Airplane Directorate, Aircraft Certification Service, 
1601 Lind Avenue SW., Renton, WA 98055-4056; telephone (425) 227-1129, 
facsimile (425) 227-1320.

SUPPLEMENTARY INFORMATION: 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: 202-512-1661) or the FAA's Aviation Rulemaking 
Advisory Committee Bulletin Board service (telephone: 800-FAA-ARAC).
    Internet users may reach the FAA's web page at http://www.faa.gov 
or the Federal Register's webpage at http://www.access.gpo.gov/su__docs 
for access to recently published rulemaking documents.
    Any person may obtain a copy of this final rule 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 amendment 
number or document number of this final rule.
    Persons interested in being placed on the mailing list for future 
notices of proposed rulemaking and final rulemaking and final rules 
should request from the above office of copy of Advisory Circular No. 
11-2A, Notices of Proposed Rulemaking Distribution System, that 
describes the application procedure.

Small Entity Inquiries

    The Small Business Regulatory Enforcement Fairness Act of 1996 
(SBREFA) requires the FAA to report inquiries from small entities 
concerning information on, and advice about, compliance with statutes 
and regulations within the FAA's jurisdiction, including interpretation 
and application of the law to specific sets of facts supplied by a 
small entity.
    The FAA's definitions of small entities may be accessed through the 
FAA's web page (http://www.faa.gov.avr/arm/sbrefa.htm), by contacting a 
local FAA official, or by contacting the FAA's Small Entity Contact 
listed below.
    If you are a small entity and have a question, contact your local 
FAA official. If you do not know how to contact your local FAA 
official, you may contact Charlene Brown, Program Analyst Staff, Office 
of Rulemaking, ARM-27, Federal Aviation Administration, 800 
Independence Avenue, SW, Washington, DC 20591, 1-888-551-1594. Internet 
users can find additional information on SBREFA in the ``Quick Jump'' 
section of the FAA's web page at http://www.faa.gov and may send 
electronic inquiries to the following internet address: 9-AWA-
[email protected].

Background

    These amendments are based on notice of proposed rulemaking (NPRM) 
93-8, which was published in the Federal Register on July 8, 1993 (58 
FR 36738). In that notice, the FAA proposed amendments to 14 CFR parts 
1, 25, 91, 121, and 135 to improve the standards for determining the 
accelerate-stop and landing distances for transport category airplanes. 
The FAA received over 100 comments from 22 different commenters on the 
proposals contained in NPRM 93-8. As a result of these comments, the 
FAA has modified some of the original proposals.
    As explained in NPRM 93-8, the operator of a turbine-powered 
category airplane must determine that the runway being used, plus any 
available stopway or clearway, is long enough to either safely continue 
or reject the takeoff from a defined go/no-go point. The go/no-go point 
occurs while the airplane is accelerating down the runway for takeoff 
when the airplane reaches a speed known as V1.
    The assure that the takeoff can be safely continued from the go/no-
go point, the length of the runway plus any clearway must be long 
enough for the airplane to reach a height of 35 feet by the end of that 
distance, even if a total loss of power from the most critical engine 
occurs just before reaching the V1 speed. This distance is 
commonly referred to as the accelerate-go distance.
    In case the pilot finds it necessary to reject the takeoff, the 
runway plus any stopway must be long enough for the airplane to be 
accelerated to the V1 speed and then brought to a complete 
stop. This distance is known as the accelerate-stop distance.
    The choice of V1 speed affects the accelerate-go and 
accelerate-stop distances. A lower V1 speed, corresponding 
to an engine failure early in the takeoff roll, increases the 
accelerate-go distance and decreases the accelerate-stop distance. 
Conversely, a higher V1 speed decreases the accelerate-go 
distance and increases the accelerate-stop distance. When V1 
is selected such that the accelerate-stop distance is equal to the 
accelerate-go distance, this distance is known as the balanced field 
length. In general, the balanced field length represents the minimum 
runway length that can be used for takeoff.
    The V1 speed selected for any takeoff depends on several 
variables, including the airplane's takeoff weight and configuration 
(flap setting), the runway length, the air temperature, and the runway 
surface elevation (airport altitude). The takeoff performance and 
limitation charts in the Airplane Flight Manual (AFM) are developed in 
accordance with the FAA airworthiness standards in subpart B of the 
Federal Aviation Regulations (FAR), part 25--``Airworthiness Standards: 
Transport Category Airplanes,'' using data gathered during 
comprehensive flight tests completed as a part of the FAA's approval of 
the airplane's type design.
    Part 25, subpart B, also prescribes the FAA airworthiness standards 
for determining the length of runway required for safe landing under 
various airplane and atmospheric conditions. Landing performance charts 
must be published in the AFM, and are used by

[[Page 8299]]

the operator to determine whether a particular runway is long enough 
for landing.
    The FAA, through the general operating rules contained in parts 91, 
121, and 135, requires operators to use the appropriate performance and 
limitation charts published in the AFM to plan their takeoffs and 
landings.
    In NPRM 93-8, the FAA proposed amendments to several sections of 
parts 25, 91, 121, and 135 concerning the methods for determining and 
applying the takeoff and landing performance standards for turbine-
powered transport category airplanes. Also, the FAA proposed to amend 
part 1, which contains terms and abbreviations used in the FAR, to add 
a definition of the term ``takeoff decision speed'' and an explanation 
for the abbreviation ``VEF.''
    The proposed amendments retained the fundamental principle that the 
pilot should be able to either safety complete a takeoff or bring the 
airplane to a complete stop, even if power is lost from the most 
critical engine just before the airplane reaches a defined go/no-go 
point. This principle has formed the basis of the takeoff performance 
standards required for the type certification of turbine-powered 
transport category airplanes since Special Civil Air Regulation No. SR-
422, effective August 27, 1957. The amendments proposed in NPRM 93-8 
were intended to provide a more rational method to take into account 
the various operational aspects affecting the takeoff distance. By the 
phrase ``more rational method,'' the FAA means a method that explicitly 
addresses the specific elements affecting the takeoff distance, rather 
than providing for critical conditions by applying more restrictive 
standards to all takeoffs.
    If the takeoff performance standards are made more restrictive, 
longer distances are needed for takeoff. However, the operator cannot 
change the length of the runway (although a longer runway, if 
available, could be used). Instead, the operator must usually reduce 
the airplane's takeoff weight in order to shorten the distance needed 
for takeoff. The more restrictive the takeoff performance standards 
are, the more takeoff weight may have to be reduced to be able to 
operate from a particular runway.
    To reduce the airplane's takeoff weight, the operator must either 
reduce the amount of fuel to be carried, or reduce the number of 
passengers or amount of cargo to be transported. Since the amount of 
fuel to be carried is dictated primarily by the route being flown, the 
operator's only option may be to reduce the number of passengers or 
amount of cargo to be transported. When the number of passengers or 
amount of cargo must be reduced for a given flight, the airplane 
operator can suffer a loss of revenue.
    Amendment 25-42, which became effective on March 1, 1978, revised 
the takeoff performance standards to make them more restrictive. Prior 
to Amendment 25-42, variations in pilot reaction time were provided for 
in the AFM accelerate-stop distances by adding one second to the flight 
test demonstrated time interval between each of the pilot actions 
necessary to stop the airplane. Typically, there are three such 
actions. The pilot reduces the power, applies the brakes, and raises 
the spoilers. Adding one second between each of these actions results 
in a total of two seconds being added to the time taken by the flight 
test pilots to accomplish the procedures for stopping the airplane. In 
calculating the resulting accelerate-stop distances for the AFM, no 
credit was allowed for any deceleration during this two-second time 
period.
    The revised standards of Amendment 25-42 required the accelerate-
stop distance to include two seconds of continued acceleration beyond 
V1 speed before the pilot takes any action to stop the 
airplane. This revision resulted in longer accelerate-stop distances 
for airplanes whose application for a type certificate was made after 
Amendment 25-42 became effective. Consequently, turbine-powered 
transport category airplanes that are currently being manufactured 
under a type certificate that was applied for prior to March 1, 1978, 
have a significant operational economic advantage over airplanes whose 
type certificate was applied for after that date. This competitive 
disparity resulting from applying different performance standards 
created a compelling need to amend the takeoff performance standards of 
part 25 without adversely affecting safety. In addition, operational 
experience indicated a need to specifically address the detrimental 
effects of worn brakes and wet runways on airplane stopping 
performance.
    Amendment 25-42 was a broad brush approach, applying to all 
takeoffs, to increase the required accelerate-stop distance. This broad 
brush approach did not explicitly account for many of the important 
operational factors that may affect takeoff performance. For example, 
the standards did not distinguish between dry and wet runways, nor were 
the effects of worn brakes taken into account. Wet runways and worn 
brakes typically result in longer accelerate-stop distances than with 
new brakes on a dry runway. By requiring wet runway performance to be 
determined and included in the AFM, and by requiring the use of worn 
brakes to determine the airplane's stopping capability, the proposed 
amendments would provide additional accelerate-stop distance for the 
conditions in which it is specifically needed in operational service.
    Because wet runways and worn brakes would be specifically addressed 
in the revised standards proposed in NPRM 93-8, the FAA also proposed 
to replace the two seconds of continued acceleration beyond 
V1 with a distance equal to two seconds at the V1 
speed. The distance equal to two seconds at constant V1, 
while shorter than that resulting from the continued acceleration 
beyond V1 required by Amendment 25-42, is a distance margin 
that must be added to the accelerate-stop distance demonstrated during 
flight testing for type certification. The FAA intends for this 
distance margin to take into account the variability in the time it 
takes for pilots, in actual operations, to accomplish the procedures 
for stopping the airplane.
    Amendment 25-42 required the two seconds of time delay to be 
applied prior to the pilot taking any action to stop the airplane. This 
more restrictive approach assumes that the airplane reaches a higher 
speed during the accelerate-stop maneuver and, therefore, results in a 
longer distance than the distance equal to two seconds at constant 
V1 speed. Inserting the time delay before the pilot takes 
any action to stop the airplane, however, does not accurately reflect 
the procedures that pilots are trained to use in operational service. 
V1 is intended to be the speed by which the pilot has 
already made the decision to rejected the takeoff and has begun taking 
action to stop the airplane. The time it takes for the pilot to 
recognize the need for a rejected takeoff, which occurs before 
V1 is reached, is considered separately within the 
airworthiness standards. Therefore, the amendments proposed in NPRM 93-
8 were intended to more accurately reflect the rejected takeoff 
procedures taught in training and the intended use of the V1 
speed.
    In summary, the purpose of the amendments to the takeoff 
performance standards of parts 25, 91, 121, and 135, as proposed in 
NPRM 93-8, was to more rationally reflect the operational factors 
involved and reduce the impact of the standards on the competitiveness 
of new versus derivative airplanes. More restrictive standards were 
proposed for takeoffs from wet runways. In addition, the proposed 
standards would require accelerate-stop distances to be

[[Page 8300]]

determined with brakes that are worn to their overhaul limit. Lastly, 
the two seconds of continued acceleration beyond V1 speed 
would be replaced by a distance equal to two seconds at V1 
speed.
    In NPRM 93-8, the FAA also proposed to amend the landing distance 
standards of part 25 to account for worn brakes. The FAA proposed this 
change to be consistent with the proposal for taking worn brakes into 
account for the takeoff accelerate-stop distances. Because airplanes 
generally require more distance to take off than to land, the allowable 
landing weight is rarely limited by the available runway length. 
Therefore, the proposed landing distance rule change was not expected 
to have a significant effect on the number of passengers or amount of 
cargo that can be carried.

International Harmonization of Airworthiness Standards

    For more than ten years, the FAA has been cooperating with the 
Joint Aviation Authorities (JAA) of Europe to promote harmonization 
between the FAR, particularly the airworthiness standards, and the 
European Joint Aviation Requirements (JAR). The aircraft certification 
authorities of 23 European countries are members of JAA. An annual 
meeting is held between FAA senior management officials and senior 
management officials of the JAA member authorities to identify 
technical subject areas where cooperation is needed to promote greater 
harmonization between the FAR of the United States and the European 
JAR. A large portion of these meetings have been open to the public. A 
comprehensive study of this activity was completed by Professor George 
A. Bermann, Columbia University School of Law, in May 1991 as a 
consultant to the Administrative Conference of the United States 
(ACUS). A copy of Professor Bermann's final report to ACUS, titled: 
``Regulatory Cooperation with Counterpart Agencies Abroad: The FAA's 
Aircraft Certification Experience,'' dated May 1991, is included in the 
docket. Based on Professor Bermann's report. ACUS has confirmed the 
administrative appropriateness of this effort and has indicated strong 
support for this activity in their Recommendation 91-1, titled 
``Federal Agency Cooperation with Foreign Government Regulators,'' 
adopted June 13, 1991.
    At the annual FAA/JAA meeting in June 1989, the FAA and JAA 
discussed the competitive disparity caused by the differences between 
the takeoff performance standards applied to airplanes that met the 
later standards of Amendment 25-42, as compared with airplanes that 
were only required to meet the takeoff performance standards that 
preceded Amendment 25-42. Even though the airplane types were 
originally type certificated at different times, thus allowing the use 
of different amendments, both groups of airplanes are continuing in 
production and both are competing for sales and for use over some 
common routes. Airplanes whose designs were type certificated to the 
standards introduced by Amendment 25-42 could be penalized in terms of 
the number of passengers or amount of cargo they can carry over a 
common route, even though the airplane's takeoff performance might be 
better from a safety perspective than a competing airplane design that 
was not required to meet the later standards. Currently, most of the 
transport category airplane types that have been required to meet the 
later standards of Amendment 25-42 were designed and manufactured 
outside the U.S. (mostly in Europe). These airplanes are competing for 
sales against airplanes that were designed and manufactured in the U.S. 
that were not required to meet the standards of Amendment 25-42. This 
situation has led to claims by a major European manufacturer of 
transport category airplanes that this disparity in the airworthiness 
standards has created an unfair international trade situation affecting 
the competitiveness of their airplane types of a later design.
    At the June 1990 annual meeting, the FAA and JAA agreed to jointly 
review the current takeoff performance standards and their 
applicability with respect to airplanes currently in use and airplanes 
produced in the future under existing approved designs. The goal was to 
reduce the inequities described above without adversely affecting 
safety. The study consisted of two parts: First, the current takeoff 
performance standards were reviewed to determine if they were too 
restrictive; and second, the merits of making the resulting standards 
apply retroactively were considered for both airplanes currently in use 
and airplanes produced in the future under existing approved designs. 
The FAA and JAA also agreed to initiate substantively the same 
rulemaking within their respective systems to harmonize the European 
and U.S. takeoff performance standards for transport category 
airplanes.
    The FAA concluded that the takeoff performance standards of part 25 
could be made more rational, and thus less restrictive overall, without 
adversely affecting safety and proposed to amend the standards 
accordingly. However, considering the safety benefits and available 
economic impact information, the FAA could not support a recommendation 
to make the standards proposed by NPRM 93-8 retroactive to either 
airplanes currently in use or future production airplanes of designs 
that have already been type certificated. If additional information to 
support making these proposed standards retroactive became available at 
a later date, the FAA proposed to review such information and determine 
if further rulemaking would be appropriate.
    In March 1992, the JAA issued its Notice of Proposed Amendment 
(NPA) 25B, D, G-244: ``Accelerate-Stop Distances and Related 
Performance Matters'' to amend the takeoff performance standards of 
JAR-25. The amendments proposed in NPRM 93-8 were substantively the 
same as the amendments proposed by the JAA NPA for JAR-25.

Discussion of the Proposals

    In NPRM 93-8, the FAA proposed the following rule changes:
    1. Replace the two seconds of continued acceleration beyond 
V1 (mandated by Amendment 25-42) with a distance margin 
equal to two seconds at V1 speed;
    2. Require that the runway surface condition (dry or wet) be taken 
into account when determining the runway length that must be available 
for takeoff; and
    3. Require that the capability of the brakes to absorb energy and 
stop the airplane during landings and rejected takeoffs be based on 
brakes that are worn to their overhaul limit.

Proposal 1

    The FAA proposed to amend the method of determining the accelerate-
stop distance prescribed in Sec. 25.109 by replacing the two seconds of 
continued acceleration after reaching V1 with a distance 
equal to two seconds at V1 speed. This proposal would reduce 
the accelerate-stop distance that must be available for a rejected 
takeoff because the airplane would be assumed to begin stopping from a 
lower speed (from V1, rather than from the speed reached 
after two seconds of acceleration beyond V1). The FAA's 
intent was to replace the most costly aspect of Amendment 25-42 with a 
requirement that closely represents the pre-Amendment 25-42 criteria of 
Sec. 25.109, as applied to the certification of recent U.S.-
manufactured airplanes.

Proposal 2

    The FAA proposed to amend Sec. 25.105 to require that airplane 
takeoff performance data be based on wet, in

[[Page 8301]]

addition to dry, runways. Section 25.1587(b) would be amended to 
require that performance information for wet runways be included in the 
Airplane Flight Manual (AFM). Sections 91.605, 121.189, and 135.379 of 
the operating rules would be amended to require that wet runways be 
taken into account when determining the runway length that must be 
available for takeoff, if wet runway performance information exists in 
the AFM. Thus, this rule would apply only to airplane designs for which 
the application for type certification occurs after the amendment 
becomes effective, and to those previously certificated airplane 
designs for which the manufacturer chooses to re-certify to the amended 
standards.
    Section 25.109 would be revised to provide the details of how the 
accelerate-stop distance would be calculated for a wet runway. The FAA 
proposed the following approach to determining the wet runway takeoff 
performance: (1) Take into account the reduced braking force due to the 
wet surface; (2) permit performance credit for using available reverse 
thrust as an additional stopping force; and (3) permit the minimum 
airplane height over the end of the runway after takeoff to be reduced 
from 35 feet to 15 feet. This approach would reduce the risk of 
overruns during rejected takeoffs on wet runways while retaining safety 
margins for continued takeoffs similar to those required for dry 
runways.
    The reduced braking force available is the most significant 
variable affecting the stopping performance on a wet runway. The FAA 
proposed to revise Sec. 25.109 to specify that the wet runway braking 
force would be one-half the dry runway braking force, unless the 
applicant demonstrated a higher wet runway braking force. Under this 
proposal, the one-half of the dry braking force level would apply 
regardless of whether the dry runway braking force is limited by the 
torque capability of the brake (which is the friction force generated 
within the brake) or the friction capability of the runway surface. 
Although it can be argued that the torque capability of a brake is 
independent of the runway surface condition, the proposed use of this 
simple relationship between wet and dry runway braking capability would 
depend on using the one-half dry relationship throughout the braking 
phase.
    Data published in Engineering Science Data Unit (ESDU) 71026, 
entitled ``Frictional and Retarding Forces on Aircraft Types--Part II: 
Estimation of Braking Force,'' shows that the relationship between wet 
and dry braking coefficient varies significantly with speed. At high 
speeds, the wet runway braking coefficient is typically less than one-
half the dry runway braking coefficient. At low speeds, the wet runway 
braking coefficient is typically more than one-half the dry runway 
braking coefficient. Used over the entire speed range for the stopping 
portion of a rejected takeoff, however, the wet runway braking 
coefficient can justifiably be approximated as one-half the dry braking 
coefficient. The ESDU report is included in the docket.
    Under this proposal, Sec. 25.109 would also be revised to permit 
the use of available reverse thrust when determining the accelerate-
stop distance for a wet runway. ``Available'' reverse thrust was 
interpreted as meaning the thrust from engines with thrust reversers 
that are operating during the stopping portion of the rejected takeoff. 
Credit for reverse thrust was included in the proposal because the most 
significant variable that affects the stopping performance on a wet 
runway, reduced braking friction, was also included as part of the 
rational approach to wet runway rejected takeoff.
    On dry runways, the FAA proposed to explicitly deny credit for 
reverse thrust when calculating the accelerate-stop distance. This 
proposal would codify current FAA policy. Although reverse thrust 
should and probably would be used during most rejected takeoffs, the 
FAA believes that the additional safety provided by not accounting for 
reverse thrust in calculating the accelerate-stop distance on a dry 
runway is necessary to offset other variables that can significantly 
affect the dry runway accelerate-stop performance determined under the 
current standards. For wet runways, credit for reverse thrust would be 
permitted because taking into account the reduced braking force 
available on the wet surface, as proposed in this notice, greatly 
outweighs the effects of these other variables. Examples of variables 
that can significantly affect the dry runway accelerate-stop 
performance include: runway surfaces that provide poorer friction 
characteristics than the runway used during flight tests to determine 
stopping performance, dragging brakes, brakes whose stopping capability 
is reduced because of heat retained from previous braking efforts, etc.
    The FAA proposed to revise Sec. 25.113 to allow the distance 
required for a continued takeoff from a wet runway to include taking 
off and climbing to a height of 15 feet, rather than the height of 35 
feet required on a dry runway. This lower screen height (which is the 
height of an imaginary screen that the airplane would just clear with 
the wings in a level attitude when taking off or landing) would reduce 
the balanced field length V1 speed, thereby reducing the 
number of high-speed rejected takeoffs on wet runways. The FAA 
considers lowering the screen height to 15 feet to be an acceptable 
method of reducing the risk of overruns on wet runways because of the 
similarity to current rules when operating from dry runways that have a 
clearway. The minimum height permitted over the end of the runway for 
current dry runway takeoffs may be 13 to 17 feet, depending on the 
airplane, when a clearway is present. In addition, a 15-foot minimum 
screen height and vertical obstacle clearance distance has been allowed 
for many years by the United Kingdom Civil Aviation Authority for wet 
runway operations without any problems being reported.
    The combination of a clearway with the proposed 15-foot screen 
height for wet runways could result in a minimum height over the end of 
the runway of near zero (i.e., liftoff very near the end of the 
runway), if clearway credit were to be permitted for wet runways in the 
same manner that it is currently permitted for dry runways. The FAA 
considers this situation to be unacceptable. The possible presence of 
standing water or other types of precipitation (e.g., slush or snow) 
and numerous operational factors (e.g., late or slow rotation to 
liftoff attitude) emphasize the need to provide more of a safety margin 
than would be present if liftoff were permitted so near the end of the 
runway. Therefore, the proposed Sec. 25.113 would not permit the 
combination of clearway credit and a 15-foot screen height. The FAA 
proposed to modify Sec. 25.113, however, to ensure that the presence of 
a clearway does not result in requiring longer runway lengths than if 
there were no clearway.
    In addition to the reduced screen height for wet runways, the 
minimum vertical distance required between the takeoff flight path 
defined in Sec. 25.115 and obstacles (e.g., trees, hills, buildings, 
etc.) would be reduced by a corresponding amount. To accomplish this, 
the FAA proposed to revise Sec. 25.115 to state that the takeoff flight 
path shall be considered to begin at a height of 35 feet at the end of 
the takeoff distance.
    This revised definition of the takeoff flight path would apply 
equally to dry and wet runways, even though the height of the airplane 
at the end of the takeoff distance (i.e., the screen height)

[[Page 8302]]

for wet runways is proposed to be only 15 feet. The effect of this 
proposal would be to make it possible to use the flight path 
information currently contained in the AFM even if the runway is wet. 
Because the screen height would be reduced from 35 feet to 15 feet for 
a wet runway, the height of an airplane at any point in the flight path 
will therefore be approximately 20 feet lower from a wet runway than 
from a dry runway. Under this proposal, the airplane's actual height 
over obstacles would be reduced by approximately 20 feet when taking 
off from a wet runway.
    Under the current regulations, the airplane's flight path must be 
higher than any obstacles by a combination of an increment of height 
and an increment of gradient (i.e., the slope of the flight path). 
Although this proposal would reduce the height increment by 
approximately 20 feet, the gradient increment would be unchanged. As 
the distance from the end of the takeoff distance increases, the 
gradient increment provides an increasingly greater portion of the 
total height difference between the airplane and the obstacle. 
Therefore, the effect of reducing the height increment over obstacles 
by 20 feet diminishes as the distance from the end of the takeoff 
distance increases.

Proposal 3

    The FAA proposed to amend Sec. 25.101(i) to require that 
accelerate-stop and landing distances must be determined with all the 
airplane brakes at the fully worn limit of their allowable wear range. 
Section 25.735 would be revised to require that the maximum brake 
energy capacity rating must be determined with each brake at the fully 
worn limit of the allowable wear range. In addition Sec. 25.735 would 
be amended to add a requirement for a flight test demonstration of the 
maximum kinetic energy rejected takeoff with not more than 10 percent 
of the allowable brake wear range remaining.

Miscellaneous

    Additionally, the FAA proposed to add one new definition and one 
new abbreviation to part 1, Definitions and Abbreviations.
    As a result of their special investigation of rejected takeoff 
accidents, the National Transportation Safety Board (NTSB) recommended 
that the FAA clearly define the term ``takeoff decision speed'' 
(V1) in part 1. This recommendation is contained in the 
NTSB's Special Investigative Report, ``Runway Overruns Following High 
Speed Rejected Takeoffs,'' published on February 27, 1990.
    Concurring with the NTSB recommendation, the FAA proposed to add a 
definition of takeoff decision speed to Sec. 1.1 in order to remove 
apparent confusion over the meaning of this term. The FAA's proposed 
definition was intended to make it clear that the decision to reject 
the takeoff, indicated by the pilot activating the first deceleration 
device, must be made no later than V1 for the airplane to be 
stopped within the accelerate-stop distance.
    The abbreviation VEF is used in several places within 
part 25. The FAA proposed to amend Sec. 1.2 to add the definition of 
VEF, which currently appears in Sec. 25.107(a)(1). 
VEF is the speed at which the critical engine is assumed to 
fail during takeoff.
    As stated previously, the FAA did not intend to apply these 
proposed amendments retroactively to either airplanes currently in use 
or future production airplanes of designs that have already been 
approved. However, manufacturers or operators of these airplanes may 
elect to comply with these proposed amendments by a change to the type 
design. The benefits of the revision to the time delay criteria of 
Sec. 25.109 would then be available to relieve the economic burden 
imposed by Amendment 25-42. The proposed amendments to take into 
account the effects of wet runways and worn brakes must also be 
included in such a recertification. The FAA expects that, for airplanes 
whose certification basis includes Amendment 25-42, most applicants 
will elect to comply with this proposal because it will be economically 
beneficial for them to do so.

Discussion of the Comments

    The FAA received over 100 comments from 22 different commenters 
regarding the proposals presented in NPRM 93-8. The commenters include 
airplane pilots, manufacturers, operators, and the associations 
representing them, foreign airworthiness authorities, and another 
agency of the U.S. government. Because of the increasing emphasis 
placed on international harmonization of the airworthiness standards, 
and because the JAA issued substantively the same proposals to amend 
JAR-25, the FAA also received many comments from foreign and 
international sources.
    In general, the pilots, and the airworthiness authorities of Canada 
and the Netherlands oppose the proposed amendments unless the FAA 
imposes the new standards retroactively. Conversely, the airplane 
manufacturers and operators generally support the proposals as long as 
they are not imposed retroactively. The JAA strongly supports the 
proposals, but also believes that these requirements should be imposed 
retroactively. The association representing European manufacturers 
supports applying the proposed standards to new derivatives of existing 
approved designs as well as to completely new airplane designs.
    Another issue that generated strong contrasting views concerns the 
distance needed to align an airplane on the runway for takeoff. 
Typically, airplanes enter the takeoff runway from an intersecting 
taxiway. The airplane must then be turned so that it is pointed down 
the runway in the direction for takeoff. FAA regulations do not 
explicitly require airplane operators to take into account the runway 
distance used to align the airplane on the runway for takeoff. The 
commenters who support retroactivity also support amending the 
regulations to require operators to take this runway alignment distance 
into account. Those who oppose retroactivity also oppose proposals to 
require taking into account the runway alignment distance.
    In NPRM 93-8, the FAA stated that ``with the safety benefits and 
economic impact information available at this time, the FAA cannot 
support a recommendation to make the standards proposed by this notice 
retroactive to either airplanes currently in use or future production 
airplanes of designs that have already been type certificated.'' This 
conclusion was reached after a review of the estimated costs and the 
potential benefits that would result from applying the proposed 
standards retroactively and mandating that operators take into account 
the runway alignment distance.
    It should be noted, however, that one part of the proposed 
standards has effectively already been imposed retroactively. The FAA 
has issued airworthiness directives (AD's) concerning brake wear limits 
for every FAA-certificated transport category airplane with a maximum 
takeoff weight of over 75,000 pounds. These AD's ensure that the brakes 
on these airplanes, even when fully worn, can absorb the energy from a 
maximum energy rejected takeoff.
    In addition to the economic impact of retroactively applying the 
proposed standards, the FAA was influenced by the increasing emphasis 
on international harmonization of the airworthiness standards. 
Retroactivity of the proposed standards and the requirement to take 
runway alignment distance into account, had the FAA decided to proceed 
with these provisions, would have been

[[Page 8303]]

accomplished through revisions to the operating rules of the FAR. At 
the time NPRM 93-8 was being developed, the JAA lacked operating rules 
with which to impose these requirements. Although the introduction and 
justification sections of JAA NPA 25B, D, G-244 discussed an intent to 
apply the standards retroactively, and to require that runway alignment 
distance be taken into account, the JAA lacked a regulatory mechanism 
for doing so. Therefore, the proposed standards would not have been 
harmonized had the FAA proposed such amendments to the part 91, 121, 
and 135 operating rules.
    Shortly thereafter, the JAA published NPA OPS-2, containing 
proposed JAR operating rules for commercial air transportation (JAR-OPS 
1). In this NPA, the JAA proposed to retroactively require operators to 
take into account the performance effects of wet runways and runways 
contaminated by slush, snow, ice or standing water, and to require 
operators to apply adjustments for runway alignment distance. NPA OPS-2 
did not address retroactive application of the proposed requirements 
related to worn brakes. The JAR-OPS 1 final rule, which retained the 
proposals noted above, was issued by the JAA on May 22, 1995. It 
becomes effective on April 1, 1998, for operators of airplanes with a 
maximum takeoff weight of over 10,000 pounds or a maximum approved 
seating capacity of 20 or more passengers.
    Due to the controversial nature of the issues of retroactivity and 
runway alignment distance, the FAA has decided to: (1) Proceed with the 
proposed rules without requiring retroactive application of these 
standards or adding a new requirement concerning runway alignment 
distance, and (2) recommend that the issues of retroactive application 
of these standards and runway alignment distance be added to the FAA/
JAA harmonization work program. Except in the treatment of these two 
issues, the final rule adopted by this amendment is completely 
harmonized with the applicable JAA standards. These two issues reflect 
differences between the FAA and JAA operating rules; the applicable 
airworthiness standards of part 25 and JAR-25 are completely harmonized 
by this amendment and a corresponding amendment to JAR-25.
    The harmonization work program is the formal method developed by 
the FAA and the JAA to harmonize relations and policies. Tasks on the 
harmonization work program are assigned to FAR/JAR harmonization 
working groups in accordance with the respective rulemaking procedures 
of the FAA and the JAA. For the FAA, these tasks are assigned to the 
Aviation Rulemaking Advisory Committee (ARAC).
    The ARAC was established to provide advice and recommendations to 
the FAA on all rulemaking activity. There are over 60 member 
organizations on the committee, representing a wide range of interest 
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. For issues on the harmonization work program, 
the ARAC assigns members, who work on behalf of the FAA, to the FAR/JAR 
harmonization working group. Although working group meetings are 
generally not open to the public, working group task assignments are 
published in the Federal Register, and all interested parties are 
invited to participate as working group members. Working groups report 
directly to the ARAC, and the ARAC must concur with a working group 
proposal before that proposal can be presented to the FAA as an 
advisory committee recommendation. After an ARAC recommendation is 
received and found acceptable by the FAA, the agency proceeds with the 
normal public rulemaking procedures.
    Most of the commenters who oppose the proposed rulemaking also 
claim that the proposals would degrade the level of safety provided by 
the current standards. Specifically, these commenters oppose the 
proposal to replace the two seconds of continued acceleration beyond 
V1 with a distance margin equal to two seconds at 
V1 speed (Proposal 1), because it would allow an increase in 
the maximum allowable takeoff weight when that weight is limited by the 
length of the runway. Although the FAA agrees with the commenters on 
the effect of this particular proposal on takeoff weight limits, and 
discussed this effect in NPRM 93-8, the FAA disagree that safety is 
degraded when this proposal is considered in combination with the other 
proposals presented in NPRM 93-8.
    In addition to Proposal 1, the FAA proposed other amendments that 
would make the current standards more stringent. As explained in NPRM 
93-8, the purpose of the FAA proposals was to present a more rational 
approach of explicitly providing for the specific elements affecting 
takeoff performance, rather than the broad brush approach represented 
by the two seconds of acceleration beyond V1. The FAA 
considers the proposed standards for worn brakes and wet runways, which 
the current standards do not explicitly address, to significantly 
improve takeoff safety. Combined with Proposal 1, the proposed 
amendments provide an equivalent or higher level of safety than the 
current standards.
    Depending on whether the runway is wet or dry and on the particular 
airplane's stopping capability with worn brakes, the maximum allowable 
takeoff weight for a given runway length could end up being either 
increased or decreased under the proposed standards. Although its 
effects are variable, the FAA estimates that Proposal 1 would reduce, 
on average, the runway length needed for takeoff by 150 feet. For 
airplanes equipped with typical steel brakes, the proposed worn brake 
requirements would add an average of 150 feet to the runway length 
needed for takeoff. The FAA estimates that the proposed wet runway 
requirements would result in an average increase of 220 feet in the 
runway length required for takeoff when the runway is wet. It should be 
emphasized that these estimates are average effects that can vary 
considerably depending on the airplane type and the specific takeoff 
conditions. For example, airplanes equipped with carbon brakes or 
certain heavy-duty steel brakes, usually will be uaffected by the worn 
brake requirements because these brakes provide the same stopping 
capability in the worn condition as the new condition. (The proposed 
worn brake requirement represent an important safety improvement, 
however, regardless of whether this improvement comes from taking into 
account a loss in brake capability, or because the requirements act as 
an incentive to provide brakes that do not suffer this loss in 
capability.)
    Along with this rulemaking effort, the FAA also participated in a 
joint FAA/industry team to produce the Takeoff Safety Training Aid. 
This training aid, first made available in August 1992, represents the 
findings of the team relative to training and procedural actions that 
could be taken to increase takeoff safety. The goal of the training aid 
is to minimize the probability of rejected takeoff accidents and 
incidents by: (1) Improving the ability of pilots to take advantage of 
opportunities to maximize takeoff performance margins; (2) improving 
the ability of pilots to make appropriate go/no-go decisions; and (3) 
improving the ability of crews to effectively accomplish the rejected 
takeoff procedures. Simulation trials and in-depth analyses of takeoff 
accidents and incidents were used to develop the training aid material. 
The FAA urges operators to use the Takeoff

[[Page 8304]]

Safety Training Aid in their qualification and recurrent aircrew 
training programs. The FAA is convinced that adoption of this material 
will further improve safety during the critical takeoff phase of 
flight.
    The FAA received a large number of comments on the proposed 
definition of takeoff decision speed (V1), including its 
relationship to the broader subject of the process by which the pilot 
recognizes a failure, decides to reject the takeoff, and acts on that 
decision. One commenter submitted several documents as additional 
supporting material, including a detailed study of pilot reaction times 
during rejected takeoff accidents. This commenter, accompanied by 
several others, believes that the proposed standards inadequately 
provide for the time it takes the average pilot to complete the 
recognition, decision, and reaction process. Other commenters support 
the FAA proposal, and some of these commenters also offered suggestions 
to further clarify the purpose of the V1 speed.
    The diversity displayed in the comments illustrates a great deal of 
misunderstanding and disagreement regarding the definition and use of 
the V1 speed. In general, inconsistent terminology used over 
the years in reference to V1 has probably contributed to 
this confusion. As noted by the commenters, V1 has been 
referred to at various times as the critical engine failure speed, the 
engine failure recognition speed, and the takeoff decision speed.
    Special Civil Air Regulation No. SR-422, effective August 27, 1957, 
originally referred to V1 as ``the critical engine failure 
speed.'' These same standards, which were later recodified into part 
25, defined the accelerate-stop distance as the distance to accelerate 
to V1, and then to stop from that speed. Although an 
allowance was required for any time delays that may reasonably be 
expected in service, SR-422 did not explicitly state where or how the 
time delays should be introduced relative to V1. For 
certification purposes, the FAA considered V1 to be the 
speed at which the pilot took the first action to stop the airplane. 
Time delays for recognition and reaction to that failure were applied 
prior to V1, and delays in accomplishing each subsequent 
action for stopping the airplane were applied after V1. 
Allowing for the time delays, the actual engine failure was therefore 
assumed to occur prior to V1.
    With Amendment 25-42, effective March 1, 1978, the FAA amended the 
airworthiness standards to clarify and standardize the method of 
applying these time delays. V1 was referred to as the 
``takeoff decision speed,'' which turned out to be ambiguous in that it 
could be interpreted to mean either the beginning or the end of the 
pilot's decision process. The preamble to Amendment 25-42, however, 
states that ``V1 is determined by adding to VEF 
[the speed at which the critical engine is assumed to fail] the speed 
gained with the critical engine inoperative during the time interval 
between the instant at which the critical engine is failed and the 
instant at which the test pilot recognizes and reacts to the engine 
failure, as indicated by the pilot's application of the first retarding 
means during accelerate-stop tests.'' This same definition was codified 
as Sec. 25.107(a)(2). Not only is V1 intended to occur at 
the end of the decision process, but it also includes the time it takes 
for the pilot to perform the first action to stop the airplane.
    The FAA requires applicants to demonstrate, by flight test, the 
time intervals between VEF and V1, and between 
each subsequent action taken by the pilot to stop the airplane. FAA 
pilots and engineers witness and participate in these tests, which must 
include at least six rejected takeoffs. Because the test pilots know 
that they are going to reject the takeoff, human factors literature 
refers to this process as a simple task. In actual operations, the 
rejected takeoff maneuver is unexpected, and is referred to as a 
complex task. In consideration of this complex task, the time intervals 
measured during certification flight tests are increased when the 
accelerate-stop distances published in the AFM are calculated. These 
additional time increments are not intended to allow extra time for 
making a decision to stop after passing through V1. Their 
purpose is to allow sufficient time (and distance) for a pilot, in 
actual operations, to accomplish the procedures for stopping the 
airplane.
    The first adjustment is made to the time interval between 
VEF and V1. During the certification flight 
tests, the pilot expects to reject the takeoff and reacts very quickly. 
To take this into account, the time interval used to calculate the AFM 
accelerate-stop distances must be the longer of either the demonstrated 
time or one second. This standard has been applied to the certification 
of every turbine-powered transport category airplane since the late 
1960's, and the FAA has not proposed to change it.
    The second adjustment concerns the time increment applied after 
V1. The method of determining this adjustment has varied, 
but the objective has always been the same--to provide enough time and 
distance for a pilot to accomplish the procedures for stopping the 
airplane. Prior to Amendment 25-42, a one-second increment was added to 
the time interval between each pilot action occurring after 
V1. For most transport category airplanes, the rejected 
takeoff involves three separate pilot actions. The pilot applies the 
brakes, reduces the thrust or power, and raises the spoilers. The 
applicant defines the order in which the actions occur, but must 
demonstrate that the resulting procedures do not require exceptional 
skill to perform. Since the test pilot's first action determines 
V1, there are typically two pilot actions occurring after 
V1. Therefore, two seconds of additional time (and the 
resulting distance) were added to the time intervals determined by the 
certification flight tests.
    Amendment 25-42 changed the method of applying these time 
increments. The provisions added by Amendment 25-42 require the AFM 
accelerate-stop distance to be calculated by inserting a two-second 
time increment after V1, but before the pilot takes the 
first action to stop the airplane. During this two-second time 
increment, the airplane continues to accelerate. No further time 
increments are added to the time intervals between the actions taken by 
the pilot to stop the airplane.
    It is important to note that Amendment 25-42 did not change the 
certification flight test procedures. The two-second time increment is 
applied analytically during the calculation of the AFM accelerate-stop 
distances, not by directing the pilot to delay action for two seconds 
after V1 during the rejected takeoff flight tests.
    The proposal presented in NPRM 93-8 would change the method of 
applying this two second time increment to a method similar to that 
existing prior to Amendment 25-42. However, the proposed method uses a 
distance increment rather than a time increment, to ensure that no 
credit is taken during this time period for system transient effects 
(e.g., engine spindown, brake pressure ramp-up, etc.). The distance 
increment is equal to the distance traversed in two seconds at the 
V1 speed. Unlike the pre-Amendment 25-42 method, this 
distance increment cannot be reduced when fewer than three pilot 
actions are used in the rejected takeoff procedures (e.g., for 
airplanes using automated systems that take the place of one or more of 
the usual pilot actions). The FAA considers the distance traveled in 
two seconds at V1 speed to be the minimum acceptable

[[Page 8305]]

distance allowance needed to provide for the element of surprise and 
other operational factors missing from the certification flight test 
demonstrations.
    As long as there are no more than three pilot actions needed to 
accomplish a rejected takeoff, the accelerate-stop distance is 
determined using the demonstrated time intervals between pilot actions 
with no additional time or distance increments applied. For each 
additional pilot action beyond the first three actions, however, a one-
second time (and distance) increment must be added to the demonstrated 
time interval for that action.
    The FAA disagrees with those commenters who believe that the 
proposed standards inadequately provide for the time it takes the 
average pilot to complete the recognition, decision, and reaction 
process. Not only does the FAA require applicants to determine by 
flight test the length of time needed for the pilot to complete this 
process, but this demonstrated time interval is also increased to take 
into account the element of surprise and other operational factors 
missing from the certification flight test demonstrations.
    Operationally, V1 represents the minimum speed from 
which the takeoff can be safely continued within the takeoff distance 
shown in the AFM, and the maximum speed from which the airplane can be 
stopped within the accelerate-stop distance shown in the AFM. 
Typically, the pilot not flying the airplane will call out 
V1 as the airplane accelerates through this speed. If the 
pilot flying the airplane has not taken action to stop the airplane 
before this callout is made, the takeoff should be continued unless the 
airplane is unsafe to fly.
    One commenter states that airplane manufacturers produce 
performance data for use by the U.S. military that provides the engine 
failure speed, rather than the speed at which the pilot must respond to 
the failure. This commenter believes that the military airworthiness 
rejected takeoff standards, which provide the crew with the engine 
failure speed, are safer than the civil airworthiness standards, which 
provide the crew with the V1 speed. The commenter further 
notes that many commercial pilots with a military background operate 
under the belief that the civil airworthiness standards provide 
equivalent safety to the military standards. In the commenter's 
opinion, the civil standards provide a lower level of safety, and these 
pilots have been given a false sense of security.
    The FAA is aware of many differences between the civil and military 
takeoff requirements. These differences are indicative of the different 
operating needs and environments between civil and military flight 
operations. For example, the military standards allow liftoff to occur 
at the very end of the runway and obstacles to be cleared with no 
safety margin in the event of the failure of the critical engine at the 
designated ``go'' speed. In contrast, part 25 requires the airplane to 
be at a height of 35 feet at the end of the takeoff distance (on a dry 
runway), and obstacles must be cleared by 35 feet plus an additional 
safety margin related to the flight path gradient. In summary, the 
civil and military airworthiness standards provide for safe operations 
within their respective operating environments. It would be 
inappropriate, however, to apply unique procedures and techniques from 
one operating environment to the other.
    One commenter noted that the proposed definition for takeoff 
decision speed tends to perpetuate the confusion over the meaning and 
use of the V1 speed. The commenter points out that 
V1 is really a ``pilot action speed'' that occurs 
immediately after the pilot makes the decision to reject the takeoff. 
Another commenter suggests that the proposed definition is technically 
inaccurate because reducing thrust during a rejected takeoff would not 
normally be construed as activating a deceleration device. Hence, the 
commenter suggested alternative wording for the words ``the pilot 
activates the first deceleration device.''
    The FAA agrees with these commenters and has revised the proposal 
accordingly. The term ``takeoff decision speed'' has been deleted both 
from the proposed definition and from Sec. 25.107(a)(2). The proposal 
to define takeoff decision speed in Sec. 1.1 is also withdrawn. The 
adopted definition represents a change to the definition of 
V1 in Sec. 1.2, rather than an addition to Sec. 1.1. This 
revised definition clarifies that V1 represents the minimum 
speed from which the takeoff can be safely continued within the takeoff 
distance shown in the AFM and the maximum speed from which the airplane 
can be stopped within the accelerate-stop distance shown in the AFM. In 
addition, the preamble discussion of the proposals has been edited for 
additional clarity to present a consistent description of the 
V1 concept.
    The proposed addition of the definition for VEF to 
Sec. 1.2 is adopted as proposed. One commenter misunderstood this 
proposal as representing the first time the FAA has sought to define 
VEF. For clarification, the term VEF and its 
definition were originally added to Sec. 25.107(a)(1) by Amendment 25-
42. The amendment adopted in this rule adds the existing definition for 
VEF to the list of abbreviations and symbols in Sec. 1.2.
    In addition to the definitions proposed in NPRM 93-8, one commenter 
suggests revising the definition of rated takeoff thrust to allow its 
use for up to ten minutes of operation. The current definition in 
Sec. 1.1 limits the use of takeoff thrust to five minutes or less. The 
FAA is currently considering the change proposed by this commenter as 
part of a harmonization effort with the European JAA. In the interim, 
the FAA has developed a procedure to review and approve specific 
requests for the use of takeoff thrust for up to ten minutes duration 
on transport category airplanes in the event of an engine failure or 
shutdown.
    One commenter recommended adding ``wet and dry runway conditions'' 
to the variables listed in Sec. 25.101(e) for which the airplane 
configuration may vary. The rationale the commenter provides for this 
recommendation is to encourage optimization of the airplane 
configuration. The FAA does not believe that the suggested change will 
accomplish the commenter's goal. Section 25.101(e) does not require 
applicants to establish an optimum configuration to meet the applicable 
requirements. Instead, Sec. 25.101(e) allows applicants to establish 
different configurations (e.g., flap settings) to obtain better 
performance at different weight, altitude, and temperature conditions.
    The same commenter recommends revising Sec. 25.105(a)(2) to require 
the takeoff data to be determined in the optimum configuration for the 
takeoff conditions specified in Sec. 25.105(c). The commenter believes 
that this change would require operators to use the optimum flap 
setting for takeoff, rather than allow the use of any flap setting that 
meets the applicable regulations. The FAA does not concur with this 
recommendations for the following reasons. First, the commenter's 
recommendation should be directed at the airplane operating 
requirements, rather than the part 25 airworthiness standards. The 
effect of the recommended revision to part 25 would be to prohibit 
takeoff data from being provided for configurations that were not 
deemed to be the optimum configuration. Second, the commenter does not 
define how to determine the optimum configuration. The commenter 
appears to support using the configuration that would provide the 
shortest takeoff and accelerate-stop

[[Page 8306]]

distances. However, this configuration also typically results in the 
poorest climb capability after takeoff, and may not be the optimum 
configuration from the standpoint of obstacle clearance, noise, 
standardization of crew procedures, or fuel use.
    The FAA received several comments regarding the proposed change to 
Sec. 25.101(i). One commenter recommends deletion of the proposed 
requirement to determine the landing distances with worn brakes. This 
commenter claims that the effects of worn brakes on landing is 
insignificant, and notes that the FAA does not expect this requirement 
to reduce the amount of payload that can be carried. The commenter also 
notes that there has never been a landing incident or accident in which 
a deficiency in brake energy due to wear was a factor, nor is there any 
reasonable likelihood that there would ever be one. The commenter goes 
on to say that the proposed requirement would result in additional 
certification test and flight manual development costs with no 
resultant safety benefit to the public.
    Although the FAA agrees that the proposed requirement is not likely 
to reduce the amount of payload that can be carried for most landings, 
the FAA disagrees that the effects of worn brakes on landing will 
always be insignificant. The effect of brake wear at the braking energy 
levels associated with a landing stop depends on the particular brake 
design. To provide for those cases in which the landing distance is 
critical, the AFM landing distance data must be based on fully worn 
brakes. The proposed requirement only specifies the wear condition of 
the brakes for determining the landing distances. No additional AFM 
information, and, therefore, no additional flight manual development 
costs would be required. The proposed requirement also would not 
necessarily result in additional certification testing. The only flight 
test that must be performed with worn brakes is the maximum energy 
rejected takeoff condition, in which the brakes must be worn to within 
10 percent of the fully worn condition. All other data must only meet 
the condition that sufficient data be available from airplane flight 
tests or wheel-brake dynamometer tests to enable adjustment of all of 
the takeoff and landing flight test results to the fully worn level. 
For example, the testing performed to determine the effect of worn 
brakes on accelerate-stop distances may also be used to determine the 
effect of worn brakes on landing distances, if it can be shown to be 
applicable.
    Another commenter suggests adding the stipulation that the 
determination of the accelerate-stop and landing distances must be 
based on the demonstrated results obtained by flight test in accordance 
with the proposed Sec. 25.735(g). The FAA concurs with the intent of 
this suggestion. Instead of modifying the proposed Sec. 25.101(i), 
however, the FAA is revising the proposed Sec. 25.735(g) and relocating 
it as a new Sec. 25.109(i). The adopted wording clarifies that the 
applicant must conduct a flight test demonstration of the maximum brake 
kinetic energy accelerate-stop distance with no more than 10 percent of 
the allowable wear range remaining on each of the airplane wheel 
brakes. This change to the original proposal is also discussed later 
relative to the comments received on the proposed Sec. 25.735(g).
    A commenter proposes a wording change to Sec. 25.101(i) to 
anticipate possible future brake materials that might show an improving 
brake performance as the brake wears. This commenter suggests that the 
proposed requirement should reference the wear condition that 
dynamometer testing indicates as producing the least effective braking 
performance. The FAA agrees that the most critical wear condition 
should be used to determine the stopping distances and energy capacity 
of the brakes. In practice, however, the FAA believes this condition 
will always be the fully worn brake. The FAA does not believe that an 
extensive dynamometer survey of different wear states is warranted.
    One commenter suggests that stopping distances be based on brakes 
that are worn to 90 percent of the allowable wear level instead of the 
proposed level of fully worn. This commenter states that, in actual 
operations, it would be virtually impossible for all the airplane's 
brake assemblies to simultaneously be at the fully worn limit of their 
allowable wear range. In addition, this commenter believes that such 
conservatism in determining the stopping distances to be unwarranted 
when combined with the worn brake requirements relating to brake energy 
absorption capability. As an alternative, this commenter, joined by a 
second commenter, proposes that Sec. 25.101(i) optionally allow 
stopping performance to be based on the actual amount of brake wear 
existing at the time of each flight. The two commenters state that it 
is unnecessary and inappropriate for the regulations to assume the 
worst case capability when satisfactory means to determine the actual 
capability can be provided. They believe that the proposed regulation 
would inhibit the development of technical and procedural advances that 
would take into account the actual wear condition of the brakes.
    The FAA does not concur with the recommendation to base the 
stopping distances on brakes worn to 90 percent of the allowable wear 
level. Although operators may typically overhaul brakes before they are 
fully worn, and the brakes on different wheels are usually at different 
levels of wear, airplanes may legally be operated with all of the brake 
assemblies in their fully worn condition. The FAA agrees that it would 
be inappropriate for the regulations to assume the worst case 
capability when satisfactory means exist to determine the true 
capability; however, the operational aspects must also be 
satisfactorily addressed.
    Regarding the commenters' proposal to allow stopping distances to 
be based on the actual brake wear level, the FAA has significant 
concerns over the operational aspects. Although it may be possible to 
determine the accelerate-stop and landing distances as a function of 
brake wear, the FAA considers it unacceptable to use, on a flight-by-
flight basis, the brake wear level as an additional takeoff performance 
variable. The added complexity caused by this additional variable would 
increase the chances of error in determining the allowable takeoff 
weight and the takeoff speeds. Also, the FAA questions whether an 
acceptable means can be developed to accurately and reliably determine 
the actual wear state of the brake under all operational and 
environmental conditions. Finally, extensive certification testing 
would be required to determine the stopping distances as a function of 
the brake wear level. A linear relationship between these variables 
cannot be assumed. Therefore, Sec. 25.101(i) is adopted as proposed, 
except for a minor editorial revision for clarification purposes.
    Since the certified accelerate-stop and landing distances will 
correspond to brakes that are at the fully worn limit of their 
allowable wear range, the allowable brake wear range must be specified 
as part of the approved type design for the airplane. This information 
should be provided on the type certificate data sheet. The allowable 
wear range should be defined in terms of a linear dimension in the 
axial direction, which is typically determined by measuring the 
extension of a pin used to indicate the amount of wear. At the fully 
worn limit of the allowable brake wear range, the brake must be removed 
from the airplane for overhaul.
    Both favorable and adverse comments were received on the FAA's 
proposal to

[[Page 8307]]

amend Sec. 25.109 to replace two seconds of acceleration beyond 
V1 speed with the distance traversed in two seconds at 
V1 speed. The commenters who objected to the proposed 
amendments believe the proposal would reduce safety. One commenter who 
disagrees with the proposed amendment also states that the comparison 
between the one-engine-inoperative and all-engines-operating 
accelerate-stop distances, as required by the proposed Sec. 25.109(a), 
would become almost meaningless. This commenter claims that ``test 
pilot response in the order of milliseconds preempts any significant 
difference in acceleration distance between engine out and all engine 
acceleration before V1.'' Also, the proposed distance 
traversed during two seconds at V1 speed is the same for 
both cases, as is the deceleration distance from V1 until 
the airplane is stopped.
    As discussed previously, the FAA considers the proposed additions 
of worn brake and wet runway requirements to significantly improve 
takeoff safety. These additional requirements, along with the proposal 
to replace the two seconds of acceleration with a distance equal to two 
seconds at V1 speed, would provide more rational takeoff 
airworthiness standards and an equivalent or higher level of safety 
than the current standards. Regarding the comparison of one-engine-
inoperative and all-engines-operating distances, the minimum time 
between the critical engine failure speed (VEF) and 
V1, as discussed earlier, is one second. During the period 
after V1, unless reducing thrust is the first pilot action 
following the engine failure, there will be another time interval 
before thrust is reduced on the remaining operating engine(s). Since 
thrust reversers may not be used in determining the dry runway 
accelerate-stop distances, the operating engines (on a turbojet powered 
airplane) will continue to produce forward thrust. Therefore (for 
turbojet airplanes), the distance to stop from V1 will 
usually be longer for all-engines-operating case than for the one-
engine-inoperative case. Whether the sum of the accelerate and stop 
distances is greater for the all-engines-operating case as opposed to 
the one-engine-inoperative case depends on the time intervals between 
VEF and V1, V1 and the pilot action to 
reduce thrust, and on the engine transient response (spindown) 
characteristics. For wet runways, in which the effect of reverse thrust 
would be included, the stopping distance with one-engine-inoperative 
will usually be longer than that with all-engines-operating. In 
general, the FAA expects the dry runway accelerate-stop distances to be 
based on the all-engines-operating case, and the wet runway accelerate-
stop distances to be based on the one-engine-inoperative case.
    One commenter suggests that the FAA should provide a statement 
proclaiming that the standards proposed in NPRM 93-8 ``reflect the full 
intent of the accelerate-stop transition segment AFM distance 
construction'' and that ``additional time delays are not envisioned.'' 
This commenter states that FAA advisory material imposed an additional 
two-second time delay beyond that prescribed by Amendment 25-42, and 
the commenter desires a clarification that such a situation will not 
recur. The FAA intends to revise Advisory Circular (AC) 25-7, ``Flight 
Test Guide for Certification of Transport Category Airplanes,'' to be 
consistent with this adopted rule and the description of the time 
delays provided in this preamble discussion regarding the definition of 
V1.
    In reviewing the comments, the FAA discovered that the proposed 
wording for Sec. 25.109(a) could be interpreted such that speeds 
greater than V1 need not be considered in determining the 
accelerate-stop distances. However, the airplane will typically exceed 
V1 speed during the stop, particularly with all-engines-
operating, even when the pilot applies the brakes at V1. The 
proposed amendments to Sec. 25.109(a) have been modified to clarify 
that the accelerate-stop distances must include the highest speed 
reached during the rejected takeoff maneuver. As modified, these 
proposed amendments to Sec. 25.109(a) are adopted.
    The FAA received a large number of comments regarding the proposed 
method for determining takeoff performance on wet runways. One of the 
provisions of the proposed method would allow applicants to use a 
simplified approach to determine the braking capability on a wet runway 
without the need for specific wet runway flight testing. Based on the 
extensive wet runway testing conducted over the past 30 years by the 
National Aeronautics and Space Administration (NASA), the FAA, the 
aerospace industry, and other organizations around the world (a 
compilation of which appears in the docket in ESDU item number 71026), 
the FAA proposed using a braking coefficient of one-half the 
demonstrated dry braking coefficient. The FAA intended for this one-
half factor to be applied even if the dry runway braking coefficient is 
limited by the maximum torque capability of the brake, rather than the 
maximum friction capability available from the runway surface.
    Several commenters disagree with using a simple one-half factor to 
determine the wet runway braking coefficient. One commenter feels the 
factor is arbitrary and that using a simple factor is inappropriate. 
Another commenter claims that other easily applied methods exist and 
should be used to provide a wet runway braking coefficient. This 
commenter believes that the proposed method effectively makes the low 
speed accelerate-stop data more conservative than the high speed data, 
which would be the opposite of what the commenter feels should be done 
to increase safety. These commenters did not propose any alternative 
methods for determining the wet runway braking coefficient.
    Several commenters object to the specific aspect of applying the 
one-half factor when the dry runway braking coefficient corresponds to 
the maximum torque capability of the brake. In spite of the explanation 
provided in the preamble discussion in NPRM 93-8, these commenters 
oppose this provision on the basis that the maximum torque capability 
of the brake is independent of the runway surface condition. One 
commenter conducted laboratory tests of a simulated wet runway to show 
that the stopping ability of an airplane on a wet runway is not a 
function of the size or torque limit of the brakes. Another commenter 
claims that this provision appears to prohibit the effective and safe 
use of braking capacity up to the limit of the wet runway braking 
coefficient. This commenter points out that an airplane with brakes 
that have a low maximum torque capability would be unfairly penalized 
relative to an airplane equipped with brakes of a higher maximum torque 
capability. Another commenter questions whether the proposed 
requirement is a conservative approach resulting from a lack of 
appropriate test data.
    The FAA agrees that the torque capability of the brake is usually 
not a limiting factor on a smooth wet runway. The FAA proposed applying 
a factor to the torque limited braking coefficient to represent the 
varying relationship between the wet and dry runway braking 
coefficients as a function of ground speed. At higher ground speeds, 
the wet runway braking coefficient is typically less than one-half the 
dry runway braking coefficient. At these higher speeds, the dry runway 
braking coefficient is usually limited by the brake's maximum torque 
capability. For the typical airplane/brake combination, factoring the 
torque limited braking coefficient obtained on a dry runway by one-half 
provides a reasonable approximation to the significantly

[[Page 8308]]

reduced braking coefficients observed at high speeds on wet runways. 
Because the total stopping distance for a high speed stop is affected 
more by the stopping capability at high speeds than at low speeds, 
applying the one-half factor only to the non-torque limited braking 
coefficient would be inadequate for determining the total distance 
needed to stop on a wet runway.
    The FAA does not concur with the comment that this proposal would 
prohibit the safe and effective use of braking capability on a wet 
runway. This proposal only addressed the method for determining the wet 
runway accelerate-stop distances presented in the AFM. It would not 
affect the manner in which the pilot uses the brakes. The FAA 
recognizes, however, that not all airplanes share the same relationship 
between V1 speeds and maximum brake torque capability, and 
that some airplane types could be affected more than others by this 
provision. In recognition of this potential disparity, the proposed 
Sec. 25.109(b)(2) would have allowed applicants the option of 
demonstrating a higher wet runway braking coefficient.
    One commenter suggested that an advisory circular may be necessary 
to provide guidance regarding an acceptable method for demonstrating a 
wet runway braking coefficient higher than one-half the dry runway 
value. Another commenter noted that one flight test, for example, 
performed on a damp grooved runway with excellent friction capability 
would be an insufficient basis for developing the AFM information 
applicable to all wet runways. Another commenter recommended a change 
to the FAA proposal to allow the use of methods other than flight 
testing to demonstrate a higher wet runway braking coefficient. This 
commenter believes that in the near future it may become feasible to 
use data obtained from either an analysis, a simulation of the 
airplane's braking system, or other sources.
    One of the commenters who opposed portions of the FAA proposal 
submitted an alternative proposal based on the same ESDU 71026 data 
source used to develop the FAA proposal. The commenter proposes an 
alternative method to replace the option for demonstrating a braking 
coefficient higher than one-half the dry runway braking coefficient. 
The following summary represents a brief synopsis of the commenter's 
detailed proposal:
    a. Derive a standard wet runway braking coefficient versus speed 
curve from the ESDU 71026 data. This curve, representing the maximum 
braking coefficient available from the runway surface, would be used 
for all transport category airplanes as the basis for developing 
airplane type specific curves.
    b. Apply adjustments to this curve to reflect the capability of an 
individual airplane type's anti-skid system on a wet runway. The anti-
skid system capability would be determined either directly from wet 
runway testing, or a conservative capability (i.e., somewhat worse than 
would be expected if testing were performed) would be assumed, based on 
the capability of existing comparable anti-skid systems.
    c. Allow higher braking coefficients for suitably maintained 
grooved or porous friction course runways.
    d. Use the brake torque limitations (i.e., the amount of torque the 
brake is capable of producing) that are determined on a dry runway for 
both wet and dry runways.
    The FAA considers the commenter's proposal to have considerable 
merit, not just as a replacement for the demonstration option as the 
commenter proposes, but also as a replacement for the one-half the dry 
braking coefficient methodology. The commenter's proposal addresses the 
shortcomings inherent in the NPRM 93-8 methodology of determining the 
wet runway braking coefficient by applying a single adjustment factor 
to the dry runway braking coefficient. Under the commenter's proposal, 
the wet runway braking capability would more accurately reflect the 
significant variation in braking capability with speed that occurs on a 
wet runway. Properly reflecting this variation with speed would remove 
the need to apply a factor to the dry runway brake torque capability.
    As adopted, Sec. 25.109(b) has been revised and new Secs. 25.109 
(c) and (d) have been added to prescribe wet runway accelerate-stop 
distance standards in a manner consistent with the commenter's 
proposal. This final rule is based on the same information as the 
original FAA proposal; however, the methodology for determining wet 
runway accelerate-stop distances has been changed to more rationally 
reflect the various factors affecting wet runway braking. The 
methodology adopted by this amendment provides a more accurate 
portrayal of wet runway stopping performance than had been proposed in 
NPRM 93-8.
    Significant issues related to the commenter's proposal, which had 
to be addressed prior to preparing this final rule, included:
    a. Defining the standard wet runway braking coefficient versus 
speed curve, considering the various parameters that affect wet runway 
stopping performance.
    b. Defining a method for determining the capability of an 
airplane's anti-skid system on a wet runway.
    c. Establishing conservative levels of anti-skid capability that 
could be used in lieu of determining this capability directly from test 
data.
    d. Determining whether a higher braking capability is appropriate 
for use with grooved or porous friction course runways. (This issue is 
discussed later along with other comments received on this topic).
    ESDU 71026 contains curves of wet runway braking coefficients 
versus speed for smooth and treaded tires at varying inflation 
pressures. These data are presented for runways of various surface 
roughness, including grooved and porous friction course runways. 
Included in the data presentation are bands about each of the curves, 
which represent variations in: water depths from damp to flooded, 
runway surface texture within the defined texture levels, tire 
characteristics, and experimental methods. From these data, it is 
readily apparent that wet runway stopping performance is significantly 
affected by many more variables than dry runway stopping performance. 
In order to determine the wet runway stopping distance, a value must be 
specified (or assumed) for each of these variables. Since it would be 
impractical to try to measure or evaluate each of these variables for 
every takeoff, the takeoff data must take into account the conditions 
likely to occur in operational service.
    It was the FAA's intent with the proposals of NPRM 93-8 to define a 
wet runway performance level that would ensure safe operation for the 
vast majority of wet runway rejected takeoffs likely to occur. This 
same principle was used in specifying values for each of the variables 
considered by the adopted wet runway methodology. The resulting 
accelerate-stop distances, coupled with information provided to 
operators and pilots concerning the use of these data, should greatly 
reduce the risk of runway overruns during wet runway operations.
    In defining the standard curves of wet runway braking coefficient 
versus speed that are prescribed by the equations in Sec. 25.109(c)(1), 
the effects of the following variables were considered: Tire pressure, 
tire tread depth, runway surface texture, and the depth of the water on 
the runway.

Tire Pressure

    The effect of tire pressure is taken into account by providing 
separate curves (i.e., equations) in Sec. 25.109(c)(1) for

[[Page 8309]]

several tire pressures. As stated in the adopted rule, linear 
interpolation may be used for tire pressures other than those listed. 
To provide additional safety, Sec. 25.109(c)(1) requires applicants to 
base the accelerate-stop distances on the maximum tire pressure 
approved for operation. Operating at a tire pressure that is lower than 
the maximum tire pressure approved for that airplane will tend to 
improve the airplane's stopping capability on a wet runway. Typically, 
manufacturer recommended tire pressures are a function of airplane 
weight; for operations at less than the maximum approved weight, the 
recommended tire pressure would be less than the maximum approved tire 
pressure.

Tire Tread Depth

    The degree to which water can be channeled out from under the tires 
significantly affects wet runway stopping capability. Airplane tires 
have ribbed grooves around the circumference of the tire for this 
purpose. The texture of the runway surface plays an equally important 
role. ESDU 71026 provides braking data for both ribbed and smooth tires 
on runways of different surface textures. A method is also provided in 
ESDU 71026 for assessing the effects of tire wear. As ribbed tires 
wear, the depth of the ribbed grooves decreases, impairing their 
ability to channel water out from under the tire.
    Surveys conducted by U.S. airplane and tire manufacturers, and 
information from major tire retreaders, indicate that the typical 
groove depth remaining at the time of tire removal can vary from about 
1.5 to 5 mm. Airplane manufacturers' maintenance manuals usually 
recommend removal when the tread depth is less than \1/32\ inch (1.2 
mm), although operation with zero tread depth is not prohibited. Loss 
of tread depth is not the sole criterion for tire removal, however. 
Tires with significant tread depth remaining may be removed for other 
reasons. Also, it is unlikely that all the tires on a particular 
airplane would be worn to the same extent.
    The standard curves (i.e., equations) of braking coefficient versus 
speed prescribed in Sec. 25.109(c)(1) are based on a tire tread depth 
of 2 mm. Since the tread depth of new tires is usually 10-12 mm, 2 mm 
represents no more than 20 percent of the original tread depth. FAA 
Advisory Circular 121.195(d)-1A, which provides guidance for 
determining operational landing distances on wet runways, specifies 
that the tires used in flight tests to determine wet runway landing 
distances should be worn to a point where no more than 20 percent of 
the original tread depth remains. Therefore, the adopted rule, which 
reflects industry practice, is also consistent with existing FAA 
guidance in this area.

Runway Surface Texture

    ESDU 71026 groups runways into five categories. These categories 
are labeled ``A'' through ``E,'' with ``A'' being the smoothest and 
``C'' the most heavily textured ungrooved runways. Categories ``D'' and 
``E'' represent grooved and other open textured surfaces. Category A 
represents a very smooth texture (an average texture depth of less than 
0.004 inches), and is not very prevalent in runways used by transport 
category airplanes. The majority of ungrooved runways fall into the 
category C grouping. The curves represented in Sec. 25.109(c)(1), as 
adopted, represent a texture midway between categories B and C.

Depth of Water on the Runway

    Obviously, the greater the water depth, the greater the degradation 
in braking capability. The curves prescribed in Sec. 25.109(c)(1) 
represent a well-soaked runway, but with no significant areas of 
standing water.
    In summary, the curves prescribed in Sec. 25.109(c)(1) represent 
the maximum tire-to-ground braking coefficient likely to be available 
from a wet runway during a rejected takeoff. They were derived by 
interpolating between the curves presented in ESDU 71026 for runway 
surface categories B and C, adjusted to represent tires with 2 mm tread 
depth remaining, and extrapolated to cover the range of V1 
speeds to be expected. The resulting curves were then smoothed and 
reduced to a mathematical form for inclusion in the rule. The 
capability for a particular airplane type to achieve this braking 
coefficient depends on: (1) The amount of torque its brakes are capable 
of producing, and (2) the performance of its anti-skid system. How the 
revised regulation addresses these two components is discussed in the 
ensuring paragraphs.
    The torque capability of the brakes is evaluated during the flight 
testing that applicants conduct to determine the dry runway accelerate-
stop distance. Since the torque capability is independent of the runway 
surface condition, the torque capability demonstrated by the dry runway 
flight tests also represents the maximum torque available during a wet 
runway stop. As adopted, Sec. 25.109(b)(2)(i) limits the stopping force 
from the wheel brakes used to determine the wet runway accelerate-stop 
distance to the stopping force determined in meeting the requirements 
of Sec. 25.101(i) (worn brakes) and Sec. 25.109(a) (the dry runway 
accelerate-stop distance). This provision prohibits applicants from 
using a brake torque that exceeds the dry runway torque limits when 
determining the wet runway accelerate-stop distance.
    An airplane's anti-skid system varies the braking action to prevent 
locked wheel skids and to maximize stopping performance to the extent 
possible. How close the anti-skid system comes to obtaining the maximum 
braking friction available between the tires and the runway is referred 
to as the anti-skid system efficiency.
    As adopted, Sec. 25.109(c)(2) requires applicants to adjust the 
maximum tire-to-ground wet runway braking coefficient determined in 
Sec. 25.109(c)(1) for the efficiency of the anti-skid system. 
Applicants will have the option of either determining the anti-skid 
system efficiency directly from flight tests on a wet runway, or using 
one of the anti-skid efficiency values specified in Sec. 25.109(c)(2). 
Regardless of which method is used, an appropriate level of flight 
testing must be performed to verify that the anti-skid system operates 
in a manner consistent with the efficiency value used, and that the 
system has been properly tuned for operation on wet runways.
    For applicants using the anti-skid efficiency values specified in 
Sec. 25.109(c)(2), a minimum of one complete wet runway stop, or 
equivalent segmented stops, should be conducted at an appropriate speed 
and energy to cover the critical operating mode of the anti-skid 
system. This testing can be performed as part of the anti-skid 
compatibility testing on a wet runway that is already required for 
brake and anti-skid system approval under Sec. 25.735. Therefore, for 
applicants using the anti-skid efficiency values specified in 
Sec. 25.109(c)(2), no additional flight tests need actually be 
performed. Existing flight test may need to be modified somewhat to 
ensure that appropriate data are obtained to verify that the anti-skid 
system operates in a manner consistent with the efficiency value used, 
and that the system has been properly tuned for operation on wet 
runways.
    As revised, Sec. 25.109(c)(2) identifies three different classes of 
anti-skid systems, and specifies a unique efficiency value associated 
with each one. This classification of anti-skid system types and the 
assigned efficiency values are based on information contained in 
Society of Automotive Engineers (SAE) Aerospace Information Report 
(AIR) 1739, title ``Information on

[[Page 8310]]

Anti-Skid Systems.'' The efficiency values prescribed in 
Sec. 25.109(c)(2) represent the worst system performance expected for 
each type of system after being properly tuned for operation on wet 
runways. The SAE document is available in the public docket for this 
rulemaking.
    The three classes of anti-skid systems represent evolving levels of 
technology and differing performance capabilities on dry and wet 
runways. On/off systems are the simplest of the three types of anti-
skid systems. For these systems, full metered brake pressure (as 
commanded by the pilot) is applied until wheel locking is sensed. Brake 
pressure is then released to allow the wheel to spin back up. When the 
system senses that the wheel is accelerating back to synchronous speed 
(i.e., ground speed), full metered pressure is again applied. The cycle 
of full pressure application/complete pressure release is repeated 
throughout the stop (or until the wheel ceases to skid with pressure 
applied).
    Quasi-modulating systems, the second type of anti-skid system, 
attempt to continuously regulate brake pressure as a function of wheel 
speed. Typically, brake pressure is released when the wheel 
deceleration rate exceeds a preselected value. Brake pressure is re-
applied at a lower level after a length of time appropriate to the 
depth of the skid. Brake pressure is then gradually increased until 
another incipient skid condition is sensed. In general, the corrective 
actions taken by these systems to exit the skid condition are based on 
a pre-programmed sequence rather than the wheel speed time history.
    Fully modulating systems, the third type of anti-skid system, are a 
further refinement of the quasi-modulating systems. The major 
difference between these two types of anti-skid systems is in the 
implementation of the skid control logic. During a skid, corrective 
action is based on the sensed wheel speed signal, rather than a pre-
programmed response. Specifically, the amount of pressure reduction or 
reapplication is based on the rate at which the wheel is going into or 
recovering from a skid. Also, higher fidelity transducers and upgraded 
control systems are used, which respond more quickly.
    For applicants who elect to determine the anti-skid efficiency 
directly from flight tests, sufficient flight testing, with adequate 
instrumentation, must be conducted to ensure confidence in the 
efficiency obtained. Although additional flight testing will be 
necessary, the FAA does not expect applicants to use this method for 
determining the anti-skid efficiency unless proportionate benefits 
(i.e., an increase in takeoff weight) are obtained. A minimum of three 
complete stops, or equivalent segmented stops, should be conducted on a 
wet runway at appropriate speeds and energies to cover the critical 
operating modes of the anti-skid system.
    As adopted, Sec. 25.109(b)(2)(ii) also requires applicants to 
adjust the wheel brakes stopping force to take into account the effect 
of the distribution of the normal load between braked and unbraked 
wheels at the most adverse center-of-gravity position approved for 
takeoff. The stopping force due to braking is equal to the braking 
coefficient multiplied by the normal load (i.e., the effective weight) 
on the braked wheels. The location of the airplane's center-of-gravity, 
which is a function of the airplane's configuration and how it is 
loaded (i.e., the position of passengers, baggage, cargo, etc.), 
affects how the load is distributed between braked and unbraked wheels. 
Typically, the nose wheels of transport category airplanes are 
unbraked, although some airplanes also have some of the main gear 
wheels unbraked). This effect must be taken into account for the most 
adverse center-of-gravity position approved for takeoff. The most 
adverse center-of-gravity position is that which results in the least 
load on the braked wheels.
    For the following reasons, the FAA regards the wet runway 
methodology issued in this final rule to be a logical outgrowth of the 
proposal published in NPRM 93-8. First, the final rule methodology 
relies on the same technical basis as the original proposal. Second, it 
responds to a comment raised during the NPRM 93-8 public comment 
process. And third, it is consistent with the overall intent of this 
rulemaking, which is to more rationally address relevant operational 
factors rather than applying more restrictive standards to all 
operating conditions. This methodology also provides applicants with 
the ability to better control any increased costs resulting from the 
addition of wet runway accelerate-stop requirements to part 25, while 
ensuring safer wet runway operations. Depending on the desired balance 
between manufacturing costs (including design and flight testing) and 
operational capabilities, an applicant can make informed choices 
regarding design characteristics (e.g., type of anti-skid system, 
takeoff speeds) and the level of wet runway testing to perform (i.e., 
use of the anti-skid efficiency values provided in the rule versus 
determining the efficiency directly from flight tests).
    The FAA recognizes that extensive guidance material will be 
necessary to assist applicants in complying with the wet runway 
accelerate-stop distance requirements incorporated in this amendment. 
Published elsewhere in this issue of the Federal Register is a notice 
of availability for a proposed revision to AC 25-7, ``Flight Test Guide 
for Certification of Transport Category Airplanes.'' A request for 
comments is included in that notice of availability. The proposed 
revision includes detailed guidance for:
    a. Using reverse thrust in determining wet runway accelerate-stop 
distances;
    b. classifying the types of anti-skid systems;
    c. Verifying the type of anti-skid system installed on the airplane 
and that it is properly tuned for operation on wet and slippery 
runways;
    d. Determining the anti-skid efficiency value; and
    e. Developing an analytical model of wet runway braking performance 
in accordance with Sec. 25.109(c).
    One commenter points out that many operators already use a form of 
wet runway takeoff performance data, which is provided to them by the 
airplane manufacturers as unapproved guidance information. These data, 
used on a voluntary basis to provide additional safety on wet runways, 
are typically developed using criteria similar to those proposed in 
NPRM 93-8. Another commenter believes that the proposed wording for 
Secs. 91.605(b)(3), 121.189(e), and 135.379(e) would result in 
retroactive changes to those airplanes for which the AFMs contain wet 
runway information carried over from previous foreign certifications. 
(Some foreign certification authorities, notably the United Kingdom 
Civil Aviation Authority, have required wet runway performance 
information to be included in the AFM.) This commenter notes that use 
of such data has not been required in the past in U.S. operations and 
does not necessarily reflect the standards proposed in NPRM 93-8. 
Although the commenter supports the proposal in general, it is 
suggested that the wording be changed to specify that the wet runway 
requirements apply only to airplanes certificated after the proposed 
amendment becomes effective.
    The FAA acknowledges that airplane manufacturers have for many 
years produced guidance information, including takeoff performance 
data, for wet runway operations. In general, the FAA supports the 
voluntary use of these available data to provide additional safety on 
wet runways for existing transport category airplanes, as long as 
compliance with the applicable

[[Page 8311]]

airworthiness and operating rules is maintained.
    The FAA did not intend, by the proposed wording Secs. 91.605(b)(3), 
121.189(e), and 135.379(e), to effectively apply the proposed wet 
runway standards retroactively. Operators should be aware that the 
approved portion of the AFM (containing the operating limitations) for 
a U.S. operator should only reflect the FAR and should not contain 
extraneous information carried over from a foreign certification. Such 
information may, however, appear in an unapproved portion of the AFM as 
supplementary guidance information. Operators may use this information 
(as long as it does not conflict with the FAR), but are not required to 
abide by it.
    The FAA does not agree with the comment to limit application of the 
proposed operating rules only to those airplanes certificated after 
this amendment becomes effective. Some manufacturers have elected to 
comply with the standards proposed in NPRM 93-8 prior to the adoption 
of this final rule. The AFMs for the affected airplane types contain 
takeoff and accelerate-stop distance limitations for takeoffs on wet 
runways, and operators must comply with these limitations, regardless 
of the date the airplane was certificated. Therefore, these amendments 
to Secs. 91.605(b)(3), 121.189(e), and 135.379(e) are adopted 
essentially as proposed, but with a clarification that this provision 
applies to operating limitations, if they exist, associated with the 
minimum distances required for takeoff from wet runways. As discussed 
earlier, further consideration of retroactive application of the 
requirements adopted by this final rule will be added to the FAA/JAA 
harmonization work program.
    Several commenters recommend that the proposed standards be revised 
to allow a higher wet runway braking coefficient to be used for grooved 
runways or runways treated with a porous friction course (PFC) overlay, 
without the need for additional flight testing. These commenters point 
out that runway friction measurement tests show that a wet runway with 
grooves or a PFC surface overlay has much better friction 
characteristics than a smooth surface. According to these commenters, 
providing credit for the improved stopping capability on these surfaces 
will result in significant public safety benefits by helping to 
expedite future runway improvements and by providing a strong incentive 
to properly maintain these surfaces. The commenters believe it is 
neither necessary nor in the public interest to avoid or defer this 
issue, considering the significant effort that has already been made by 
airport operators, both domestic and foreign, to improve runway 
surfaces.
    To facilitate timely action on this issue, these commenters propose 
that the FAA initially adopt a value that the commenters consider to be 
very conservative (i.e., a much lower wet runway braking coefficient 
than would be expected). Most of these commenters propose using a wet 
runway braking coefficient for grooved and PFC runways equal to 70 
percent of the dry runway braking coefficient, although one commenter 
proposed a factor of 80 percent. For comparison purposes, one commenter 
reports that tests conducted using a Boeing 737-300 airplane showed wet 
grooved runway braking capability that was equal to, or in some cases 
greater than, 95 percent of that obtained on a dry runway. The 
commenters note that a longer term rulemaking activity could be 
undertaken in the future to establish a higher factor, if warranted.
    One of these commenters provided information relative to grooved 
and PFC runway credit in Japan. This commenter states that the Japanese 
Civil Aviation Bureau allows a wet runway braking coefficient of 70 to 
80 percent of the dry runway value to be used for grooved or PFC 
runways. In Japan, Most of the runways at civil airports are grooved, 
and periodic friction surveys are conducted to assure that the surfaces 
are properly maintained. These surveys are done by using a combination 
of visual inspections and friction measuring devices.
    The FAA agrees that grooved and PFC runways can offer substantial 
safety benefits in wet conditions. The FAA has taken an active role 
since the late 1960's in evaluating the benefits of these runway 
surface treatments and supports their use throughout the U.S. Tests 
conducted by the FAA, NASA, and others confirm that applying a factor 
of 70 percent to the dry runway braking coefficient, as proposed by the 
commenters, would conservatively represent the stopping performance on 
properly designed, constructed, and maintained grooved and PFC runways. 
A summary of these test data has been placed in the docket. The actual 
friction capability of grooved and PFC runways varies, however, 
depending on variables such as groove shape, depth, and spacing, method 
used to construct the grooves, type of pavement surface, volume and 
type of airplane traffic, frequency of pavement evaluations, and 
maintenance. The FAR currently do not contain mandatory standards 
regarding the design, construction, and maintenance of grooved or PFC 
runways, but AC 150/5320-12B, ``Measurement, Construction, and 
Maintenance of Skid-Resistant Airport Pavement Surfaces,'' provides 
relevant guidelines and procedures.
    The FAA concurs with the commenters' proposal and agrees that it 
presents an opportunity to provide an additional incentive for airport 
operators to install and maintain grooved and PFC runways. The FAA 
agrees that 70 percent of the dry runway braking coefficient 
conservatively represents the stopping performance on properly 
designed, constructed, and maintained grooved or PFC runways. Using a 
simple factor applied to the dry runway braking coefficient is 
appropriate for grooved and PFC runways because the braking 
coefficient's variation with speed is much lower on these types of 
runways.
    As noted in the earlier discussion of the parameters affecting wet 
runway stopping performance, ESDU 71026 contains data corresponding to 
grooved and PFC surfaces. An evaluation of the ESDU data reveals that 
using a surface texture mid-way between surfaces D and E in combination 
with typical anti-skid efficiencies provides approximately the same 
airplane stopping performance as using 70 percent of the dry runway 
braking capability.
    In response to the comments regarding grooved and PFC runways, a 
new Sec. 25.109(d) is adopted to establish an optional wet runway 
braking coefficient for grooved or PFC runways. The braking coefficient 
for determining the accelerate-stop distance on grooved and PFC runways 
is defined in Sec. 25.109(d) as either 70 percent of the value used to 
determine the dry runway accelerate-stop distances, or a value based on 
the ESDU data and derived in a manner consistent with that used for 
ungrooved runways. Section 25.105(c)(1) is revised to allow applicants, 
at their option, to provide data for grooved and PFC runways, in 
addition to the smooth surface runway data that is currently required. 
In addition, the existing Sec. 25.109(d) is revised to remove the words 
``smooth'' and ``hard-surfaced'' and redesignated as Sec. 25.109(h).
    Section 25.1533(a)(3) is amended to allow wet runway takeoff 
distances on grooved and PFC runways to be established as additional 
operating limitations, but approval to use these distances is limited 
to runways that have been designed, constructed, and maintained in a 
manner acceptable to the FAA Administrator. In conjunction, 
Secs. 91.605(b)(3), 121.189(e), and 135.379(e) of the operating rules 
are

[[Page 8312]]

amended to limit the use of the grooved and PFC wet runway accelerate-
stop distances to runways that the operator has determined have been 
designed, constructed, and maintained in a manner acceptable to the FAA 
Administrator. The page(s) in the AFM containing the wet runway 
accelerate-stop distances for grooved and PFC runways should contain a 
note equivalent to the following: ``These accelerate-stop distances 
apply only to runways that are grooved or treated with a porous 
friction course (PFC) overlay that the operator has determined have 
been designed, constructed, and maintained in a manner acceptable to 
the FAA Administrator.''
    Airplane operators who wish to use the grooved or PFC runway 
accelerate-stop distances must determine that the design, construction, 
and maintenance aspects are acceptable for each runway for which such 
credit is sought. In making these determinations, operators may rely on 
certifications from airport operators or independent evaluations of 
runways. In either case, it is expected that operators will be able to 
demonstrate that their determinations are well founded. Acceptable 
runways should be listed in Part C of the operator's approved 
operations specifications (for those operators required to have 
operations specifications).
    FAA AC 150/5320-12B provides guidance regarding grooved and PFC 
runway construction and maintenance techniques that are considered 
acceptable to the Administrator. These criteria for obtaining 
operational approval to use the grooved and PFC wet runway accelerate-
stop distances are consistent with the guidance provided in AC 
121.195(d)-1A for approval to use operational landing distance for wet 
runways. After adoption of this final rule, the FAA also intends to 
include this information in an update to AC 91-6A, ``Water, Slush, and 
Snow on the Runway.''
    Under the proposals for Secs. 25.109 (c) and (d) in NPRM 93-8, wet 
runway accelerate-stop distances may include the additional stopping 
force provided by reverse thrust; however, including this stopping 
force would be prohibited when determining the dry runway accelerate-
stop distances. Most of the commenters supported the proposal for wet 
runways, although several commenters noted that several important 
aspects were not addressed. These aspects include issues such as 
reliability of the trust reversers, piloting procedures, 
controllability in crosswinds, flight test methods, etc.
    The FAA agrees that detailed guidance material is needed, relative 
to thrust reversers, to define an acceptable means to comply with the 
proposed requirements of Sec. 25.109(c). As mentioned earlier, the FAA 
intends to propose specific guidance material soon as part of a 
revision to AC 25-7. In general, the FAA intends to propose that: (1) 
Acceptable procedures should be developed and demonstrated, including 
the time needed to accomplish these procedures; (2) the responses and 
interactions of airplane systems should be taken into account; (3) the 
recommended level of reverse thrust should be easily obtainable under 
in-service conditions (e.g., by providing a detent or other tactile 
method of thrust selection); (4) directional control should be 
demonstrated with maximum braking on a wet runway with a ten-knot 
crosswind from the most adverse direction; (5) the probability of 
failure should be no more than 1 per 1000 selections; (6) inoperative 
thrust reversers at dispatch should be taken into account; (7) 
satisfactory engine operating characteristics should be demonstrated; 
and (8) appropriate flight tests should be conducted to determine the 
effective stopping force provided by reverse thrust, and to validate 
the total stopping force provided by all of the decelerating means.
    One commenter proposed an amendment to the existing Sec. 25.109(c) 
to clarify that a finding of ``safe and reliable'' for any deceleration 
means other than wheel brakes must take into account the interactions 
and interdependencies of the various systems involved, and that 
consistent results must be expected under all conditions covered by the 
AFM. This comment is directed primarily at a landing situation in which 
slippery runways and higher than normal approach speeds could thwart or 
delay sensing logic for determining whether the airplane is on the 
ground. Consequently, the operation of any deceleration means that can 
only be activated on the ground (e.g., ground spoilers and thrust 
reversers) would also be delayed.
    Under the existing Secs. 25.109(c) and 25.1309, the FAA already 
reviews the system operation and inter-compatibility issues that would 
be addressed by the commenter's proposed changes to Sec. 25.109(c). 
Therefore, the FAA considers these proposed changes to be unnecessary.
    One commenter noted that the same reasons in the FAA's proposal for 
denying accelerate-stop distance credit for the use of reverse thrust 
on dry runways also apply to wet runways. Therefore, if dry runway 
accelerate-stop distances need the safety margin provided by not 
including the effects of reverse thrust, then so do the wet runway 
accelerate-stop distances. The FAA does not concur. As stated in the 
discussion of the proposal, the FAA believes that the additional safety 
provided by not accounting for reverse thrust in calculating the 
accelerate-stop distance on a dry runway is necessary to offset other 
variables that can significantly affect the dry runway accelerate-stop 
performance. Examples of variables that can significantly affect the 
dry runway accelerate-stop performance include: runway surfaces that 
provide poorer friction characteristics than the runway used during 
flight tests to determine stopping performance, dragging brakes, brakes 
whose stopping capability is reduced because of heat retained from 
previous braking efforts, etc. Although these variables may also be 
present for wet runways, their effects are adequately covered by the 
adopted method of determining the stopping capability on a wet runway. 
This method provides a margin of safety by using conservative 
assumptions regarding runway surface texture, tire tread depth, tire 
inflation pressure, anti-skid efficiency, etc.
    Despite the reasons the FAA presented in NPRM 93-8 for denying 
accelerate-stop distance credit for the use of reverse thrust on dry 
runways, several commenters propose that reverse thrust credit be 
permitted, at least to the extent that it offsets any performance 
degradation due to worn brakes. These commenters claim that the 
majority of the factors degrading accelerate-stop performance have been 
taken into account; therefore, it would be appropriate to include the 
positive effect of reverse thrust. These commenters also note that 
reverse thrust capability is provided on nearly all commercial jet 
transport airplanes, current thrust reversers are reliable, flightcrews 
are trained to use reverse thrust, and its use is a normal part of 
operational stopping procedures. Also, the probability of a thrust 
reverser failing to operate, combined with the probability of all 
brakes being at the fully worn limit, is very low, and there would be 
an even lower probability of these factors occurring in combination 
with a takeoff rejected from a critically high speed. Under the 
proposal offered by most of these commenters, the dry runway 
accelerate-stop distance would be required to be the greater of either: 
(1) The distance determined using new brakes without reverse thrust, or 
(2) the distance determined using worn brakes

[[Page 8313]]

with reverse thrust. Since item (1) corresponds to the current 
standards, this proposal would not reduce the accelerate-stop distance 
to less than what is currently required. The effect of the commenters' 
proposal would be to offset any loss in stopping capability associated 
with worn brakes.
    As stated previously, the FAA considers that the additional safety 
provided by not including the effect of reverse thrust for the 
accelerate-stop distance on a dry runway is necessary to offset other 
variables that can significantly affect the dry runway accelerate-stop 
performance. The effect of these other variables on the dry runway 
accelerate-stop distance are unchanged by this rulemaking. Although the 
part 25 airworthiness standards are being made more stringent by adding 
requirements related to worn brakes and wet runways, the overall effect 
of these additions are partially offset by the change in the method 
used to account for the time it takes the pilot to perform the 
procedures for rejecting the takeoff. Further alleviating provisions 
are inappropriate because they would unacceptably reduce the level of 
safety. Therefore, Secs. 25.109(c) and (d) are amended as proposed in 
NPRM 93-8, except that they have been re-designated as paragraphs (e) 
and (f), respectively.
    As part of the proposed wet runway standards, Secs. 25.13 (a) and 
(b) would allow the airplane's height over the end of the runway (known 
as the screen height) to be reduced from 35 feet on dry runways to 15 
feet on wet runways. Some commenters object to reducing the screen 
height for wet runways, stating that safety margins would be reduced 
for takeoffs that are continued following an engine failure. One 
commenter would accept a reduced screen height only if operators are 
first required to use the configuration that provides the best short 
field performance. The FAA response to the latter comment was provided 
in the discussion of the commenter's proposed change to 
Sec. 25.105(a)(2).
    The FAA proposed reducing the required screen height for wet 
runways to re-balance the available safety margins, in a manner that 
does not impose significant costs on airplane operators, when taking 
off from a wet runway. On a wet runway, the distance needed to stop the 
airplane increases significantly due to the reduced braking 
effectiveness. On the other hand, the distance needed to complete a 
continued takeoff is generally unchanged from that needed for a dry 
runway. By reducing the required screen height on a wet runway, a lower 
V1 speed can be used. The effect of lower V1 
speeds will be to reduce the number of rejected takeoffs that occur on 
wet runways, and to reduce the speed from which these takeoffs are 
rejected. The latter effect is considered especially important because 
the braking capability on a wet runway is significantly poorer at 
higher speeds.
    As noted by one of the commenters, any reduction in the number of 
takeoffs that are rejected will produce an equal number of additional 
continued takeoffs. Because of the lower V1 speed, the 
airplane's height over the end of the runway for these takeoffs, as 
well as the ensuring flight path, will be lower than would normally be 
achieved on a dry runway. If a clearway area is available, however, the 
minimum height of the airplane over the end of a dry runway may, under 
the current standards, be as low as 13 to 17 feet. On this basis, the 
FAA considers a minimum screen height of 15 feet to be acceptable when 
the runway is wet.
    Allowing the screen height to be reduced on wet runways also 
reduces the cost burden imposed on airplane operators by the wet runway 
standards. By taking into account the degraded braking capability on 
wet runways, these standards may reduce the maximum weight at which the 
airplane would be allowed to take off from a given runway. If a screen 
height of 35 feet were retained for wet runways, an even greater 
reduction in takeoff weight capability could be necessary.
    In the proposed Sec. 25.113(c), the FAA intended to require that 
the minimum screen height on a wet runway with a clearway would not be 
lower than either: (1) 15 feet, or (2) the screen height that could be 
achieved if the runway were dry. A clearway is an area at least 500 
feet wide beyond the departure end of the runway that has not obstacles 
protruding above a 1.25 percent upward sloping gradient. On a dry 
runway, up to one-half of the distance traversed between liftoff and a 
height of 35 feet may be over the clearway. As noted earlier, the 
screen height (i.e., the height at the end of the runway) achieved on a 
dry runway with clearway may end up being as low as 13 feet. 
Accordingly, a higher takeoff weight is possible when a clearway is 
present. The words ``but not beyond the end of the runway'' included in 
the proposal for Sec. 25.113(b)(2) would effectively require the wet 
runway screen height to be not less than 15 feet. Under the proposed 
wording, therefore, the presence of clearway could not be used to 
increase the takeoff weight on a wet runway. Also, in some instances, 
the minimum screen height on a wet runway would be higher than that for 
a dry runway.
    Several commenters expressed confusion over the discrepancy between 
the FAA's intent, as expressed in the preamble to NPRM 93-8, and the 
proposed wording for Secs. 25.113(b) (2) and (c). One commenter noted 
that the words ``but not beyond the end of the runway'' appear to 
inappropriately introduce an operating rule into the type design 
standards. This commenter also notes that the quoted phrase does not 
appear in the JAA's equivalent NPA. This commenter further suggests 
that removing the quoted phrase would accomplish the FAA's stated 
intent of allowing a very limited takeoff weight increase on wet 
runways when clearway is present.
    Another commenter recommends that maximum clearway credit be 
permitted in combination with the 15-foot screen height on a wet 
runway. The commenter notes that V1 speed could then be 
reduced even further, thus providing additional safety in the event of 
a rejected takeoff on a wet runway. The FAA infers that this commenter 
is proposing that half of the distance traversed between liftoff and a 
height of 15 feet be permitted to occur over the clearway. Because of 
the parabolic shape of the flight path, the airplane may end up being 
only five to eight feet high at the end of the runway. The point at 
which the airplane lifts off would thus be very near the end of the 
runway. As discussed in NPRM 93-8, the FAA considers such a situation 
to be unacceptable. The possibility of standing water on the wet 
runway, or operational considerations such as a late or slow rotation 
to the liftoff attitude, emphasize the need to require liftoff to occur 
well before the end of the runway.
    Other commenters, including an international association 
representing airplane operators, suggest that the potential benefit 
provided by the FAA's intended proposal regarding clearway on a wet 
runway is so small that it is insignificant. These commenters are 
willing to accept the slight conservatism associated with prohibiting 
credit for clearway in conjunction with the 15-foot screen height on 
wet runways in favor of simplifying and clarifying the rule language. 
The FAA concurs with this comment and is amending Sec. 25.113 
accordingly. The phrase ``but not beyond the end of the runway,'' 
contained in the proposed Sec. 25.113(b)(2), is removed. The proposed 
Sec. 25.113(c) is clarified to prohibit a screen height of less than 15 
feet on a wet runway. If the limiting takeoff distance is determined by 
the all-engines-operating condition, where

[[Page 8314]]

the minimum height at the end of the takeoff distance remains 35 feet, 
clearway credit is allowed on a wet runway in the same manner as it is 
allowed on a dry runway. Also, Sec. 25.113 is amended to add the 
provision that in the absence of clearway, the takeoff run is equal to 
the takeoff distance. This provision is added only to ensure 
completeness of the definition of takeoff run within the airworthiness 
standards and is in accordance with standard industry practice. The 
current requirement does not define the takeoff run when clearway is 
not present.
    Some commenters apparently misunderstand some aspects of the wet 
runway standards, especially the effect of Secs. 25.109(b)(1) and 
25.113(b)(1). These sections require the accelerate-stop and takeoff 
distances on a wet runway (at the wet runway V1 speed) to be 
at least as long as the corresponding distances on a dry runway (at the 
dry runway V1 speed). These requirements therefore ensure 
that the maximum takeoff weight for a wet runway can never be higher 
than that allowed when the runway is dry. In practice, applicants 
should use the following procedure to determine takeoff performance 
when the runway is wet. First, conduct the takeoff performance analysis 
assuming the runway is dry. Then, repeat the analysis using wet runway 
data, including the wet runway V1 speed. The lowest takeoff 
weight from these analyses is the maximum takeoff weight that can be 
used when the runway is wet. For this takeoff weight, determine and 
compare the accelerate-stop and takeoff distances applicable to both 
dry and wet conditions. The longer of each of these accelerate-stop and 
takeoff distances apply when the runway is wet.
    The FAA received only one comment related to the proposed change to 
Sec. 25.115(a). This proposed change would allow the airplane's height 
over any obstacles to be reduced by an amount corresponding to the 
reduced screen height allowed when taking off from a wet runway. The 
commenter suggested that the current obstacle clearance criteria should 
be updated to represent more realistic operational conditions. The 
commenter is referring to the criteria used to evaluate whether the 
obstacle must be cleared vertically, or whether an operator can 
consider the obstacle to be laterally outside of the airplane's path. 
The FAA is currently developing an advisory circular that will address 
this issue in detail. Therefore, Sec. 25.115(a) is amended as proposed.
    The FAA received several comments on the proposed changes to 
Sec. 25.735. One commenter proposed that Sec. 25.735(f) refer to the 
wear condition that provides the least effective braking performance. 
This comment is related to a similar comment regarding Sec. 25.101(i). 
As discussed in response to the earlier comment, the FAA believes that 
the fully worn condition will always provide the least effective 
braking performance.
    This commenter also suggests that the flight test proposed under 
Sec. 25.735(g) is unnecessary. The commenter proposes that a flight 
test should be required only if poor correlation exists between 
dynamometer test results and flight test results. The commenter also 
believes that a rejected takeoff may not represent the most severe 
stopping condition. For example, landing at the maximum landing weight 
with the flaps retracted may involve higher stopping energies. For this 
reason, the commenter suggests that Sec. 25.735(g) refer to the most 
severe stop rather than a rejected takeoff.
    The flight test proposed in Sec. 25.735(g) is the only flight test 
that would be required to be conducted at a specific brake wear level. 
The FAA considers this test to be a necessary demonstration of the 
airplane's ability to safely stop under the most critical rejected 
takeoff condition. For the remainder of the flight testing to determine 
the rejected takeoff and landing stopping distances, the brakes may be 
at any wear level desired by the applicant (including new brakes). 
Dynamometer testing could be used to determine the difference in 
stopping capability between fully worn brakes and the brake wear level 
used in the flight tests. This difference would be applied to the 
flight test results to determine the stopping distances for fully worn 
brakes.
    For the purposes of this demonstration, the FAA considers the 
maximum kinetic energy rejected takeoff to be the most critical 
stopping condition. Therefore, the FAA does not concur with the 
commenter's suggestion to replace the reference to rejected takeoff in 
the flight test demonstration with a reference to the most severe stop. 
However, from a brake approval standpoint, the FAA agrees that the 
brakes, in the fully worn condition, should be capable of absorbing the 
energy produced during the most severe stopping condition. The FAA has 
tasked a harmonization working group with recommending new or revised 
requirements for approval of brakes installed on transport category 
airplanes, and this working group is expected to recommend proposed 
standards addressing this issue.
    Another commenter suggests that the flight test demonstration 
referenced by the proposed Sec. 25.735(g) should include a two-second 
overshoot of V1, before applying the brakes, to allow for 
the average pilot response time. The FAA does not concur with this 
comment because V1 represents the highest speed at which the 
pilot should take the first action to reject the takeoff. Also, the 
procedures used during the flight test demonstration, including the 
time at which the pilot applies the brakes, should be consistent with 
the rejected takeoff procedures provided by the applicant in the AFM.
    One commenter proposed that Sec. 25.735(f) be clarified to allow 
for other devices inherent in a particular airplane design that may be 
used to dissipate energy. Failure to allow such credit, claims the 
commenter, will diminish the value of technological improvements in 
energy dissipation devices that are likely to be introduced to improve 
airplane stopping performance under wet runway conditions.
    The current Sec. 25.735(f) allows for the use of the same 
decelerating means to determine the brake kinetic energy capacity 
rating as are used to determine the dry runway accelerate-stop 
distances. The energy absorption capability of the brake is generally 
more of a concern on a dry runway than on a wet runway because of the 
difference in deceleration capability. To receive credit for energy 
dissipation devices that are likely to be introduced to improve 
airplane stopping performance under wet runway conditions, these 
devices must also provide proportionate benefits when the runway is 
dry, as well as meet the safety and reliability criteria of the amended 
Sec. 25.109(e). Within these constraints, the FAA will consider any 
technological improvements in energy deceleration devices at the time 
such devices are proposed for evaluation.
    Two commenters suggest that the proposed amendment to associate the 
brake energy rating of Sec. 25.735(f) with brakes in the fully worn 
condition is inappropriate and could lead to confusion during the brake 
approval process. These commenters concur with the intent that each 
wheel-brake assembly, when fully worn, be capable of absorbing the 
maximum kinetic energy for which it is approved. However, these 
commenters note that the kinetic energy level defined in Sec. 25.735(f) 
is the same energy level used in Technical Standard Order (TSO)-C26c 
for demonstrating the capability of the brake to successfully complete 
100 landing stops with no refurbishment or other changes made to brake 
system components (except for one change in

[[Page 8315]]

brake lining material). (TSO-C26c contains minimum performance 
standards for aircraft landing wheels and wheel-brake assemblies and 
specifies the brake dynamometer tests to demonstrate compliance with 
these standard.) Because of the relationship between Sec. 25.735(f) and 
the TSO, any change to the definition of the energy level in 
Sec. 25.735(f) would presumably also apply to the TSO. Since the TSO 
100-stop test is intended to verify that the brake has acceptable 
structural durability, rather than to demonstrate the capability to 
successfully complete a high energy stop in the fully worn condition, 
the combination of the worn condition with the TSO energy level would 
be inappropriate. A brake that is fully worn at the beginning of the 
100-stop test would be unable to successfully complete the test.
    One of the commenters notes that the TSO also requires a test 
involving one stop at the maximum rejected takeoff kinetic energy. 
According to the commenter, it is this test that should be conducted 
with a fully worn brake. The energy rating demonstrated by this test is 
not explicitly referenced in part 25, but is contained in JAR-25 as JAR 
25.735(h). The commenter proposes adding JAR 25.735(h) to part 25 to 
harmonize the two standards and to help clarify the application of the 
worn brake requirements. This commenter also suggests adding references 
to the applicable TSO and clarifying that the formula provided in 
Sec. 25.735(f)(2) need only be modified in cases of designed unequal 
braking distributions. Uneven braking distributions can unintentionally 
occur during flight tests, but this characteristic cannot be predicted 
during the design or qualification stages for which Sec. 25.735(f)(2) 
is relevant.
    The FAA concurs with these proposals. As amended, Sec. 25.735(f) 
defines the landing kinetic energy rating to be used during 
qualification testing per the applicable TSO or other qualification 
testing used to show an equivalent level of safety, as necessary to 
obtain the approval required by Sec. 25.735(a). The proposed reference 
to a fully worn brake is inappropriate in this section and has been 
removed. In the proposed revision to AC 25-7, for which the notice of 
availability is published elsewhere in this issue of the Federal 
Register, the FAA proposes to clarify that the relevant TSO 100-stop 
test may begin with a brake in any condition representative of service 
use, including new. In addition, a new Sec. 25.735(h), based on JAR 
25.735(h), has been added. This section is similar to Sec. 25.735(f), 
but defines the rejected takeoff, rather than the landing kinetic 
energy rating used in the applicable TSO. Unlike the landing brake 
kinetic energy rating, the rejected takeoff brake kinetic energy rating 
must be demonstrated with a fully worn brake. Finally, both the revised 
Sec. 25.735(f)(2) and the new Sec. 25.735(h)(2) require the referenced 
formulae for determining the brake energy capacity rating to be 
modified only in the case of designed unequal braking distributions. 
The format of the existing Sec. 25.735(f)(2), with respect to this 
provision, has been adjusted to conform to Federal Register formatting 
guidelines, and the new Sec. 25.735(h)(2) has been formatted similarly. 
With these changes, the final rule better matches the intent of the 
NPRM 93-8 proposals, and also harmonizes these sections with JAR-25.
    The FAA intends to revise TSO-C26c to be consistent with these 
amendments to Sec. 25.735. The Aviation Rulemaking Advisory Committee 
(ARAC) has been chartered with recommending appropriate changes to the 
TSO. Currently, the FAA envisions issuing the revised TSO, applicable 
to transport category airplanes, under a new designation, TSO-C135.
    One commenter suggests that the proposed Sec. 25.735(g) should be 
deleted. This commenter believes that this proposed flight test 
requirement is misplaced in the brake design and construction section 
of part 25. The commenter suggests that this issue should be addressed 
in the flight test guidance provided in AC 25-7.
    The FAA concurs that the proposed flight test requirement would be 
better placed elsewhere, but does not concur with completely removing 
it from part 25. As stated previously, the FAA considers this test to 
be a necessary demonstration of the airplane's ability to safely stop 
under the most critical rejected takeoff condition. In addition, the 
FAA intends for this test to determine or validate the AFM accelerate-
stop distance for this condition. Therefore, the proposed 
Sec. 25.735(g) has been reworded to clarify that the airplane must stop 
within the accelerate-stop distance and is adopted as Sec. 25.109(i). 
Existing Sec. 25.735(g), which would have been redesignated as 
Sec. 25.735(h), remains as Sec. 25.735(g) in the adopted rule.
    The FAA received one comment regarding the proposed amendment to 
Sec. 25.1587(b). The objective of this proposal is to require that 
takeoff performance information for wet runways be included in the AFM. 
The commenter agrees with this objective, but notes that 
Sec. 25.1587(b) addresses performance information other than that which 
would be affected by the surface condition of the takeoff runway. The 
commenter suggests that the proposed amendment instead be placed in 
Sec. 25.1533(a)(3), which addresses operating limitations based on the 
minimum takeoff distances. The FAA concurs with this comment. 
Therefore, the proposed change to Sec. 25.1587(b) has been removed, and 
Sec. 25.1533(a)(3) is revised accordingly. The adopted amendment also 
corrects a typographical error in existing Sec. 25.1533(a), identified 
by this commenter, by replacing the reference to Sec. 25.103 with a 
reference to Sec. 25.109.
    One commenter strongly endorses a requirement to add a takeoff 
performance monitor to the flight deck of all airplanes to help pilots 
determine whether a takeoff should be rejected or continued. The 
commenter notes that modern transport category airplanes already 
contain most of the necessary instrumentation. According to the 
commenter, all that would be needed would be a display and a dedicated 
processor to compute the data to be displayed.
    The FAA has participated in past evaluations of systems designed to 
monitor the performance of the airplane during the takeoff. Such 
systems typically compare the airplane's actual performance, as 
determined by airplane instrumentation, with the performance predicted 
by the AFM. If the airplane's performance is less than predicted, the 
performance shortfall would be indicated by the monitor. In addition, 
the takeoff speeds, V1 and VR, could be 
correlated with the point on the runway at which they should be 
reached. This information could assist pilots in determining whether it 
is safer to reject or to continue the takeoff.
    The FAA supports efforts at improving the go/no-go decision 
process. Advisory Circular 25-15. ``Approval of Flight Management 
Systems in Transport Category Airplanes,'' provides a means to obtain 
FAA approval of a takeoff performance monitor function as part of a 
flight management system. However, takeoff performance monitors are not 
yet sufficiently reliable nor are they sophisticated enough to warrant 
requiring their addition to the flight deck of transport category 
airplanes. Varying winds during the takeoff or a runway with a variable 
slope may cause the monitor to provide a false indication. The FAA is 
also concerned that the number of high speed rejected takeoffs could 
increase as pilots delay action to determine, for example, if an 
initially sub-par acceleration is corrected. Also, unnecessary rejected 
takeoffs could occur as a result of small

[[Page 8316]]

differences between the predicted airplane acceleration and the actual 
airplane's acceleration as determined by the onboard instrumentation. A 
takeoff performance monitor would need to consider all of the variables 
reflected in the takeoff performance data, such as atmospheric 
conditions, airplane flap setting, thrust level (including reduced and 
derated takeoff thrust), runway length, slope, and surface condition, 
etc. It is possible to design such a system, but current systems have 
not demonstrated a safety benefit over the information currently 
available to the pilot.
    The same commenter recommends that the FAA undertake a study using 
research simulators to validate airplane/pilot performance in obstacle 
limited takeoffs with engine failures. The objective of this study 
would be to determine if there is a high degree of reliability that the 
combined airplane/pilot performance is acceptable. The commenter feels 
that such a study is essential to considerations of lower screen 
heights, tailwind takeoffs, and pilot decision making when the takeoff 
weight is limited by obstacle clearance considerations. In the interim, 
the commenter suggests that the FAA adopt more stringent obstacle 
clearance criteria, such as those contained in the International Civil 
Aviation Organization's (ICAO) Annex 6, Attachment C, Paragraph 3--
Takeoff Obstacle Clearance Limitations.
    Section 25.111 currently requires applicants to determine the 
airplane's takeoff path, which begins with the start of the takeoff 
roll and ends approximately 1,500 feet above the takeoff surface. Under 
Sec. 25.111(d), applicants must conduct flight tests to ensure that the 
airplane can achieve the takeoff path presented in the AFM. The takeoff 
path data, and the flight test demonstrations, must be based on the 
procedures established by the applicant for operation in service, and 
assume that one engine fails at VEF. Except for automatic 
propeller feathering and retraction of the landing gear, the airplane 
configuration must remain constant, and changes in power or thrust that 
require action by a pilot may not be made until the airplane reaches a 
height of 400 feet above the takeoff surface.
    In addition to the takeoff path determined under Sec. 25.111, 
Sec. 25.115 requires applicants to determine the net takeoff flight 
path. The net takeoff flight path begins at the end of the takeoff 
distance and is equal to the takeoff flight path with the gradient of 
climb reduced by: 0.8 percent for two-engine airplanes; 0.9 percent for 
three-engine airplanes; and 1.0 percent for four-engine airplanes. 
These adjustments to the airplane's demonstrated climb gradient 
capability represent a safety margin for use in complying with the 
obstacle clearance requirements prescribed by the applicable operating 
rules. For airplanes operated under parts 121 or 135, the net takeoff 
flight path not only must clear all applicable obstacles, but must 
clear them by a height of at least 35 feet.
    The current airworthiness standards already address the issues the 
commenter proposes for further study. For each part 25 airplane type 
design, applicants must conduct flight tests to validate the capability 
of the airplane, using normal piloting actions, to achieve the 
published flight path. Safety margins are then added to ensure that 
this flight path adequately clears all applicable obstacles.
    The obstacle clearance criteria recommended by ICAO would require 
airplane operators to consider a larger ground area to be under the 
takeoff flight path when determining which obstacles must be cleared 
vertically. An obstacle that can be considered to be cleared laterally 
under current FAA practices may have to be cleared vertically under the 
ICAO recommendations. This change could result in restricting the 
amount of cargo or passengers to be carried because the airplane's 
vertical flight path capability is directly related to its takeoff 
weight. The FAA is currently drafting an advisory circular to provide 
standardized guidelines regarding the extent of the ground area that 
must be considered when determining which obstacles must be cleared 
vertically.

Regulatory Evaluation Summary

    Proposed changes to Federal regulations must undergo several 
economic analyses. First, Executive Order 12866 directs that each 
Federal agency shall propose or adopt a regulation only upon a reasoned 
determination that the benefits of the intended regulation justify its 
costs. Second, the Regulatory Flexibility Act of 1980 requires agencies 
to analyze the economic effect of regulatory changes on small entities. 
Third, the Office of Management and Budget directs agencies to assess 
the effects of regulatory changes on international trade. In conducting 
these analyses, the FAA has determined that this rule: (1) Will 
generate benefits that justify its costs as defined in the Executive 
Order; (2) will not have a significant impact on a substantial number 
of small entities; and (3) will not constitute a barrier to 
international trade. These analyses, available in the docket, are 
summarized below.
    In order to analyze the potential net costs of the rule, this 
evaluation considers a hypothetical production program for a 
representative new type certification. This example assumes that: (1) 
Incremental certification costs are incurred in year ``0'', (2) 
production starts in year ``4'', (3) the first airplane enters service 
in year ``5'', (4) 50 airplanes are produced per year for ten years so 
that total production equals 500, (5) each airplane is retired at the 
end of its 25 year design service goal, and (6) the discount rate is 7 
percent.
    The analysis of incremental costs is divided into two cases: one 
which assumes a brake design that exhibits little decline in brake 
performance with wear, and another which assumes a brake design that 
exhibits a decline in brake performance with wear.
    In the former case, the average reduction in dry runway accelerate-
stop distance associated with the revised 2-second-at-V1 
requirement is greater than the average increase in accelerate-stop 
distance associated with the worn brake requirement. This will result 
in a reduction in operating costs of approximately $5,105 per airplane 
per year, or $128,000 per airplane over its service life (in nominal 
terms). However, approximately one third of takeoffs would be conducted 
using the wet runway accelerate-stop distance. Under the production run 
and cost assumptions enumerated above, the wet runway amendments will 
add approximately $2,700 to operating costs per airplane per year, or 
$68,000 per airplane over its service life. Therefore, net operating 
costs under this design assumption will decline by approximately $2,400 
per airplane per year, or $59,400 per airplane over its service life. 
Total costs (including consideration of incremental certification and 
development costs), then, will be reduced by approximately $28.9 
million for the 500 airplane fleet over its 34 year service life. On a 
discounted basis, total fleet costs will be reduced by approximately 
$7.5 million.
    In the case where brake performance is assumed to decline with 
wear, the average reduction in dry runway accelerate-stop distance 
associated with the revised 2-second-at-V1 requirement is 
offset by the average increase in dry runway accelerate-stop distance 
associated with the worn brake requirement. Again, however, the wet 
runway requirements will add approximately $2,700 (in nominal terms) 
per year per airplane to operating costs. Therefore, lifetime 
incremental costs (again including consideration of

[[Page 8317]]

incremental certification and development costs) for the 500 airplane 
fleet are approximately $34.9 million, or $9.6 million on a discounted 
basis. It should be emphasized, however, that FAA anticipates that 
future airplane models will incorporate brake designs that exhibit 
little reduction in braking force with wear.
    The rule will have significant safety implications owing to the 
fact that it creates economic incentives for manufacturers, operators, 
and airports to adopt procedures which reduce takeoff hazards. While 
these ancillary safety benefits are not directly valued in this 
economic analysis, they are discussed in a qualitative way below.
    The rule's worn-brake provisions will have important safety 
impacts. For airplanes that continue to make use of brake designs in 
which braking capacity declines with wear, the rule provides an 
incentive to reduce the specified level of allowable wear in return for 
some reduction in accelerate-stop distances. In this way, accelerate-
stop distances are more closely related to actual brake performance.
    Existing regulations do not distinguish between dry and wet runway 
surface conditions. The accident history, however, shows that wet 
runway rejected takeoff overrun accidents account for a 
disproportionate share of the total. In fact, the wet runway rejected 
takeoff accident rate (involving substantial damage or hull loss) is 
seven times greater than the dry runway accident rate. The rule 
enhances safety by taking into account this hazardous takeoff 
condition. First, it directly increases accelerate-stop margins for wet 
runway conditions. Second, it creates an economic incentive to develop 
more stringent maintenance programs for skid-resistant runway surfaces.

Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (RFA) was enacted by 
Congress to ensure that small entities are not unnecessarily and 
disproportionately burdened by government regulations. The RFA requires 
agencies to review rules which may have ``a significant economic impact 
on a substantial number of small entities.'' FAA Order 2100.14A, 
Regulatory Flexibility Criteria and Guidance, specifies small entity 
size and cost thresholds by Standard Industrial Classification (SIC). 
Entities potentially affected by the rule include manufacturers of 
transport category airplanes (SIC 3721) and operators of aircraft for 
hire (SIC 4511).
    There are no manufacturers of transport category airplanes that 
meet the SIC 3721 size threshold for small entities (75 employees). 
However, small air carriers operating transport category airplanes 
could be affected by the rule. Order 2100.14A defines a small carrier 
as one owning 9 or fewer aircraft. The definition of ``significant 
economic impact'' varies by air carrier type: for operators whose 
fleets consist entirely of aircraft having a seating capacity of more 
than 60 passengers the threshold is $123,445, for other operators the 
threshold is $69,005.
    Under the most conservative (that is, most costly) compliance 
assumptions, the rule will increase operating costs by approximately 
$2,700 per airplane per year; or $24,300 per year for a nine-airplane 
fleet. Assuming that all incremental certification costs are passed on 
to the operator, the rule would increase the price of an airplane by 
$1,570. When this is amortized over the 25-year life of the airplane 
(assuming a 7% discount rate), the incremental cost per airplane is 
approximately $126 per year or $1,134 per year for a nine-airplane 
fleet. An upper-bound estimate of the annual impact of the proposed 
rule to small operators, then, is approximately $24,300+$1,134=$25,434. 
FAA holds, therefore, that the rule will not have a significant 
economic impact on a substantial number of small entities.

Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (the Act), 
enacted as Pub. L. 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 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 rule does not contain any Federal intergovernmental or private 
sector mandate. Therefore, the requirements of Title II of the Unfunded 
Mandates Reform Act of 1995 do not apply.

Trade Impact Assessment

    Recognizing that nominally domestic regulations often affect 
international trade, the Office of Management and Budget directs 
Federal agencies to assess whether or not a rule or regulation will 
have the effect of lessening the restraints of any trade-sensitive 
actively. The FAA determines that the subject rule will reduce barriers 
to international trade.
    The rule collectively places U.S. and foreign transport airplanes 
on a more equitable basis regarding their marketability. The 
standardization of certification criteria between the FAA and the Joint 
Aviation Authorities (JAA) of Europe, and the equalization of safety 
levels for pre- and post-Amendment 25-42 airplanes eliminates the 
slight comparative disadvantage experienced by certain foreign 
airplanes. The requirement regarding the two-second margin allows 
European-produced airplanes certified under Amendment 25-42 to become 
slightly more competitive against current production U.S. airplanes 
that were not certified under Amendment 25-42 by marginally expanding 
their takeoff envelope.

Federalism Implications

    The regulations adopted herein will not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this final 
rule will not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.

International Civil Aviation Organization (ICAO) and Joint Aviation 
Regulations

    In keeping with U.S. obligations under the Convention on 
International Civil Aviation, it is FAA policy to comply with ICAO 
Standards and Recommended Practices to the maximum extent practicable. 
The FAA has determined that this rule does not

[[Page 8318]]

conflict with any international agreement of the United States.

Paperwork Reduction Act

    In accordance with the Paperwork Reduction Act of 1990 (44 U.S.C. 
3501 et seq.). there are not reporting or recordkeeping requirements 
associated with this rule.

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 airplane and their subsequent operation, it could affect 
interstate aviation in Alaska. The Administrator has considered the 
extent to which Alaska is not served by transportation modes other than 
a 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.

 List of Subjects

14 CFR Part 1

    Air transportation.

14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

14 CFR Part 91

    Aircraft, Airmen, Aviation safety, Reporting and recordkeeping 
requirements.

14 CFR Part 121

    Air carriers, Aircraft, Airmen, Aviation safety, Charter flights, 
Reporting and recordkeeping requirements, Safety, Transportation.

14 CFR Part 135

    Aircraft, Airplane, Airworthiness, Air transportation.

Adoption of the Amendment

    In consideration of the foregoing, the Federal Aviation 
Administration amends 14 CFR parts 1, 25, 91, 121, and 135 of the 
Federal Aviation Regulations (FAR) as follows:

PART 1--DEFINITIONS AND ABBREVIATIONS

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

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

    2. Section 1.2 is amended by adding a new abbreviation 
``VEF'' and revising the description for the abbreviation 
``V1'' to read as follows:


Sec. 1.2  Abbreviations and symbols.

* * * * *
    VEF means the speed at which the critical engine is 
assumed to fail during takeoff.
* * * * *
    V1 means the maximum speed in the takeoff at which the 
pilot must take the first action (e.g., apply brakes, reduce thrust, 
deploy speed brakes) to stop the airplane within the accelerate-stop 
distance. V1 also means the minimum speed in the takeoff, 
following a failure of the critical engine at VEF, at which 
the pilot can continue the takeoff and achieve the required height 
above the takeoff surface within the takeoff distance.
* * * * *

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

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

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

    4. Section 25.101 is amended by adding a new paragraph (i) to read 
as follows:


Sec. 25.101  General.

* * * * *
    (i) The accelerate-stop and landing distances prescribed in 
Secs. 25.109 and 25.125, respectively, must be determined with all the 
airplane wheel brake assemblies at the fully worn limit of their 
allowable wear range.
    5. Section Sec. 25.105 is amended by revising paragraph (c)(1) to 
read as follows:


Sec. 25.105  Takeoff.

* * * * *
    (c) * * *
    (1) In the case of land planes and amphibians:
    (i) Smooth, dry and wet, hard-surfaced runways; and
    (ii) At the option of the applicant, grooved or porous friction 
course wet, hard-surfaced runways.
* * * * *
    6. Section Sec. 25.107 is amended by revising paragraph (a)(2) to 
read as follows:


Sec. 25.107  Takeoff speeds.

    (a) * * *
    (2) V1, in terms of calibrated airspeed, is selected by 
the applicant; however, V1 may not be less than 
VEF plus the speed gained with critical engine inoperative 
during the time interval between the instant at which the critical 
engine is failed, and the instant at which the pilot recognizes and 
reacts to the engine failure, as indicated by the pilot's initiation of 
the first action (e.g., applying brakes, reducing thrust, deploying 
speed brakes) to stop the airplane during accelerate-stop tests.
* * * * *
    7. Section 25.109 is amended by revising paragraph (a), 
redesignating paragraph (b) as paragraph (e) and revising the 
introductory text, redesignating paragraph (c) as paragraph (g) 
redesignating paragraph (d) as paragraph (h) and revising the first 
sentence, and adding new paragraphs (b), (c), (d), (f), and (i) to read 
as follows:


Sec. 25.109  Accelerate-stop distance.

    (a) The accelerate-stop distance on a dry runway is the greater of 
the following distances:
    (1) The sum of the distances necessary to--
    (i) Accelerate the airplane from a standing start with all engines 
operating to VEF for takeoff from a dry runway;
    (ii) Allow the airplane to accelerate from VEF to the 
highest speed reached during the rejected takeoff, assuming the 
critical engine fails at VEF and the pilot takes the first 
action to reject the takeoff at the V1 for takeoff from a 
dry runway; and
    (iii) Come to a full stop on a dry runway from the speed reached as 
prescribed in paragraph (a)(1)(ii) of this section; plus
    (iv) A distance equivalent to 2 seconds at the V1 for 
takeoff from a dry runway.
    (2) The sum of the distances necessary to--
    (i) Accelerate the airplane from a standing start with all engines 
operating to the highest speed reached during the rejected takeoff, 
assuming the pilot takes the first action to reject the takeoff at the 
V1 for takeoff from a dry runway; and
    (ii) With all engines still operating, come to a full stop on dry 
runway from the speed reached as prescribed in paragraph (a)(2)(i) of 
this section; plus
    (iii) A distance equivalent to 2 seconds at the V1 for 
takeoff from a dry runway.

[[Page 8319]]

    (b) The accelerate-stop distance on a wet runway is the greater of 
the following distances:
    (1) The accelerate-stop distance on a dry runway determined in 
accordance with paragraph (a) of this section; or
    (2) The accelerate-stop distance determined in accordance with 
paragraph (a) of this section, except that the runway is wet and the 
corresponding wet runway values of VEF and V1 are 
used. In determining the wet runway accelerate-stop distance, the 
stopping force from the wheel brakes may never exceed:
    (i) The wheel brakes stopping force determined in meeting the 
requirements of Sec. 25.101(i) and paragraph (a) of this section; and
    (ii) The force resulting from the wet runway braking coefficient of 
friction determined in accordance with paragraphs (c) or (d) of this 
section, as applicable, taking into account the distribution of the 
normal load between braked and unbraked wheels at the most adverse 
center-of-gravity position approved for takeoff.
    (c) The wet runway braking coefficient of friction for a smooth wet 
runway is defined as a curve of friction coefficient versus ground 
speed and must be computed as follows:
    (1) The maximum tire-to-ground wet runway braking coefficient of 
friction is defined as:

BILLING CODE 4910-13-M
[GRAPHIC] [TIFF OMITTED] TR18FE98.004


BILLING CODE 4910-13-C
Where--

Tire Pressure=maximum airplane operating tire pressure (psi);
t/gMAX=maximum tire-to-ground braking coefficient;
V=airplane true ground speed (knots); and
Linear interpolation may be used for tire pressures other than those 
listed.

    (2) The maximum tire-to-ground wet runway braking coefficient of 
friction must be adjusted to take into account the efficiency of the 
anti-skid system on a wet runway. Anti-skid system operation must be 
demonstrated by flight testing on a smooth wet runway, and its 
efficiency must be determined. Unless a specific anti-skid system 
efficiency is determined from a quantitative analysis of the flight 
testing on a smooth wet runway, the maximum tire-to-ground wet runway 
braking coefficient of friction determined in paragraph (c)(1) of this 
section must be multiplied by the efficiency value associated with the 
type of anti-skid system installed on the airplane:

------------------------------------------------------------------------
                                                              Efficiency
                  Type of anti-skid system                       value  
------------------------------------------------------------------------
On-Off......................................................       0.30 
Quasi-Modulating............................................       0.50 
Fully Modulating............................................       0.80 
------------------------------------------------------------------------

    (d) At the option of the applicant, a higher wet runway braking 
coefficient of friction may be used for runway surfaces that have been 
grooved or treated with a porous friction course material. For grooved 
and porous friction course runways, the wet runway braking coefficent 
of friction is defined as either:
    (1) 70 percent of the dry runway braking coefficient of friction 
used to determine the dry runway accelerate-stop distance; or
    (2) The wet runway braking coefficient defined in paragraph (c) of 
this section, except that a specific anti-skid system efficiency, if 
determined, is appropriate for a grooved or porous friction course wet 
runway, and the maximum tire-to-ground wet runway braking coefficient 
of friction is defined as:

BILLING CODE 4910-13-M

[[Page 8320]]

[GRAPHIC] [TIFF OMITTED] TR18FE98.005



BILLING CODE 4910-13-C
Where--

Tire Pressure=maximum airplane operating tire pressure (psi);
t/gMAX=maximum tire-to-ground braking coefficient;
V=airplane true ground speed (knots); and
Linear interpolation may be used for tire pressures other than those 
listed.

    (e) Except as provided in paragraph (f)(1) of this section, means 
other than wheel brakes may be used to determine the accelerate-stop 
distance if that means--
* * * * *
    (f) The effects of available reverse thrust--
    (1) Shall not be included as an additional means of deceleration 
when determining the accelerate-stop distance on a dry runway; and
    (2) May be included as an additional means of deceleration using 
recommended reverse thrust procedures when determining the accelerate-
stop distance on a wet runway, provided the requirements of paragraph 
(e) of this section are met.
* * * * *
    (h) If the accelerate-stop distance includes a stopway with surface 
characteristics substantially different from those of the runway, the 
takeoff data must include operational correction factors for the 
accelerate-stop distance. * * *
    (i) A flight test demonstration of the maximum brake kinetic energy 
accelerate-stop distance must be conducted with not more than 10 
percent of the allowable brake wear range remaining on each of the 
airplane wheel brakes.
    8. Section 25.113 is amended by revising the introductory text of 
paragraph (a) and revising paragraph (a)(1), redesignating paragraph 
(b) as paragraph (c) and revising it, and adding a new paragraph (b) to 
read as follows:


Sec. 25.113  Takeoff distance and takeoff run.

    (a) Takeoff distance on a dry runway is the greater of--
    (1) The horizontal distance along the takeoff path from the start 
of the takeoff to the point at which the airplane is 35 feet above the 
takeoff surface, determined under Sec. 25.111 for a dry runway; or
* * * * *
    (b) Takeoff distance on a wet runway is the greater of--
    (1) The takeoff distance on a dry runway determined in accordance 
with paragraph (a) of this section; or
    (2) The horizontal distance along the takeoff path from the start 
of the takeoff to the point at which the airplane is 15 feet above the 
takeoff surface, achieved in a manner consistent with the achievement 
of V2 before reaching 35 feet above the takeoff surface, 
determined under Sec. 25.111 for a wet runway.
    (c) If the takeoff distance does not include a clearway, the 
takeoff run is equal to the takeoff distance. If the takeoff distance 
includes a clearway--
    (1) The takeoff run on a dry runway is the greater of--
    (i) The horizontal distance along the takeoff path from the start 
of the takeoff to a point equidistant between the point at which 
VLOF is reached and the point at which the airplane is 35 
feet above the takeoff surface, as determined under Sec. 25.111 for a 
dry runway; or
    (ii) 115 percent of the horizontal distance along the takeoff path, 
with all engines operating, from the start of the takeoff to a point 
equidistant between the point at which VLOF is reached and 
the point at which the airplane is 35 feet above the takeoff surface, 
determined by a procedure consistent with Sec. 25.111.
    (2) The takeoff run on a wet runway is the greater of--
    (i) The horizontal distance along the takeoff path from the start 
of the takeoff to the point at which the airplane is 15 feet above the 
takeoff surface, achieved in a manner consistent with the achievement 
of V2 before reaching 35 feet above the takeoff surface, as 
determined under Sec. 25.111 for a wet runway; or
    (ii) 115 percent of the horizontal distance along the takeoff path, 
with all engines operating, from the start of the takeoff to a point 
equidistant between the point at which VLOF is reached and 
the point at which the airplane is 35 feet above the takeoff surface, 
determined by a procedure consistent with Sec. 25.111.
    9. Section 25.115 is amended by revising paragraph (a) to read as 
follows:


Sec. 25.115  Takeoff flight path.

    (a) The takeoff flight path shall be considered to begin 35 feet 
above the takeoff surface at the end of the takeoff distance determined 
in accordance with Sec. 25.113(a) or (b), as appropriate for the runway 
surface condition.
* * * * *
    10. Section 25.735 is amended by revising paragraphs (f) 
introductory text and (f)(2) and adding a new paragraph (h) to read as 
follows:


Sec. 25.735  Brakes

* * * * *
    (f) The design landing brake kinetic energy capacity rating of each 
main wheel-brake assembly shall be used during qualification testing of 
the brake to the applicable Technical Standard Order (TSO) or an 
acceptable equivalent. This kinetic energy rating may not be less than 
the kinetic energy absorption requirements determined under either of 
the following methods:
    (1) * * *
    (2) Instead of a rational analysis, the kinetic energy absorption 
requirements for each main wheel-brake assembly may be derived from the 
following formula, which must be modified in cases of designed unequal 
braking distributions.

[[Page 8321]]

[GRAPHIC] [TIFF OMITTED] TR18FE98.006


Where--
KE=Kinetic energy per wheel (ft.-lb.);
W=Design landing weight (lb.);
V=Airplane speed in knots. V must not be less than VS0, the 
power off stalling speed of the airplane at sea level, at the design 
landing weight, and in the landing configuration; and
N=Number of main wheels with brakes.
* * * * *
    (h) The rejected takeoff brake kinetic energy capacity rating of 
each main wheel-brake assembly that is at the fully worn limit of its 
allowable wear range shall be used during qualification testing of the 
brake to the applicable Technical Standard Order (TSO) or an acceptable 
equivalent. This kinetic energy rating may not be less than the kinetic 
energy absorption requirements determined under either of the following 
methods:
    (1) The brake kinetic energy absorption requirements must be based 
on a rational analysis of the sequence of events expected during an 
accelerate-stop maneuver. This analysis must include conservative 
values of airplane speed at which the brakes are applied, braking 
coefficient of friction between tires and runway, aerodynamic drag, 
propeller drag or powerplant forward thrust, and (if more critical) the 
most adverse single engine or propeller malfunction.
    (2) Instead of a rational analysis, the kinetic energy absorption 
requirements for each main wheel brake assembly may be derived from the 
following formula, which must be modified in cases of designed unequal 
braking distributions:
[GRAPHIC] [TIFF OMITTED] TR18FE98.007

Where--
KE=Kinetic energy per wheel (ft.-lb.);
W=Airplane weight (lb.);
V=Airplane speed (knots);
N=Number of main wheels with brakes; and
W and V are the most critical combination of takeoff weight and ground 
speed obtained in a rejected takeoff.
    11. Section 25.1533 is amended by revising paragraph (a)(3) to read 
as follows:


Sec. 25.1533  Additional operating limitations.

    (a) * * *
    (3) The minimum takeoff distances must be established as the 
distances at which compliance is shown with the applicable provisions 
of this part (including the provisions of Secs. 25.109 and 25.113, for 
weights, altitudes, temperatures, wind components, runway surface 
conditions (dry and wet), and runway gradients) for smooth, hard-
surfaced runways. Additionally, at the option of the applicant, wet 
runway takeoff distances may be established for runway surfaces that 
have been grooved or treated with a porous friction course, and may be 
approved for use on runways where such surfaces have been designed 
constructed, and maintained in a manner acceptable to the 
Administrator.
* * * * *

PART 91--GENERAL OPERATING AND FLIGHT RULES

    12. The authority citation for part 91 continues to read as 
follows:
    Authority: 49 U.S.C. 106(g), 1155, 40103, 40113, 40120, 44101, 
44111, 44701, 44709, 44711, 44712, 44715, 44716, 44717, 44722, 
46306, 46315, 46316, 46502, 46504, 46506-46507, 47122, 47508, 47528-
47531; Articles 12 and 29 of the Convention on International Civil 
Aviation (61 Stat. 1180), 902.
    13. Section 91.605 is amended by revising paragraph (b)(3) to read 
as follows:


Sec. 91.605  Transport category civil airplane weight limitations.

* * * * *
    (b) * * *
    (3) The takeoff weight does not exceed the weight shown in the 
Airplane Flight Manual to correspond with the minimum distances 
required for takeoff, considering the elevation of the airport, the 
runway to be used, the effective runway gradient, the ambient 
temperature and wind component at the time of takeoff, and, if 
operating limitations exist for the minimum distances required for 
takeoff from wet runways, the runway surface condition (dry or wet). 
Wet runway distances associated with grooved or porous friction course 
runways, if provided in the Airplane Flight Manual, may be used only 
for runways that are grooved or treated with a porous friction course 
(PFC) overlay, and that the operator determines are designed, 
constructed, and maintained in a manner acceptable to the 
Administrator.
* * * * *

PART 121--OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL 
OPERATIONS

    14. The authority citation for part 121 continues to read as 
follows:
    Authority: 49 U.S.C. 106(g), 40113, 40119, 44101, 44701-44702, 
44705, 44709-44711, 44713, 44716-44717, 44722, 44901, 44903-44904, 
44912, 46105.
    15. Section 121.189 is amended by revising paragraph (e) to read as 
follows:


Sec. 121.189  Airplanes: Turbine engine powered: Takeoff limitations.

* * * * *
    (e) In determining maximum weights, minimum distances, and flight 
paths under paragraphs (a) through (d) of this section, correction must 
be made for the runway to be used, the elevation of the airport, the 
effective runway gradient, the ambient temperature and wind component 
at the time of takeoff, and, if operating limitations exist for the 
minimum distances required for takeoff from wet runways, the runway 
surface condition (dry or wet). Wet runway distances associated with 
grooved or porous friction course runways, if provided in the Airplane 
Flight Manual, may be used only for runways that are grooved or treated 
with a porous friction course (PFC) overlay, and that the operator 
determines are designed, constructed, and maintained in a manner 
acceptable to the Administrator.
* * * * *

PART 135--OPERATING REQUIREMENTS: COMMUTER AND ON-DEMAND OPERATIONS

    16. The authority citation for part 135 continues to read as 
follows:
    Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44705, 44709, 
44711-44713, 44715-44717, 44722.
    17. Section 135.379 is amended by revising paragraph (e) to read as 
follows:


Sec. 135.379  Large transport category airplanes: Turbine engine 
powered: Takeoff limitations.

* * * * *
    (e) In determining maximum weights, minimum distances, and flight 
paths under paragraphs (a) through (d) of this section, correction must 
be made for the runway to be used, the elevation of the airport, the 
effective runway gradient, the ambient temperature and wind component 
at the time of takeoff, and, if operating limitations exist for the 
minimum distances required for takeoff from wet runways, the runway 
surface condition (dry or wet). Wet runway distances associated with 
grooved or porous friction course runways, if provided in the Airplane 
Flight Manual, may be used only for runways that are grooved or treated 
with a porous friction course (PFC) overlay, and that the operator 
determines are designed, constructed, and maintained in a manner 
acceptable to the Administrator.
* * * * *
    Issued in Washington, DC on February 10, 1998.
Jane F. Garvey,
Administrator.
[FR Doc. 98-3898 Filed 2-17-98; 8:45 am]
BILLING CODE 4910-13-M