J 0 I N T CENTER

AEI-BROOKINGS JOINT CENTER FOR REGULATORY STUDIES

EXHIBIT

Z7EJtY/J

Improved Standards for Determining Rejected Takeoff and

Landing Performance

Federal Register

Department of Transportation

Office of Aviation Policy and Plans

RIN: 2120-AB17

63 Federal Register 8298

February 18, 1998

This analysis was issued by the agency and collected by the AEI-Brookings Joint Center in order

to promote regulatory transparency. The views expressed in this document are those of the

agency and do not necessarily reflect those of the Joint Center.
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Wednesday

February 18, 1998

Part IV

Department of

Transportation

Federal Aviation Administration

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

8297
8298 Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations

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.

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 UAR-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-F AA-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 rule making and final

rule making 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 httpi//www.faa.gov and

may send electronic inquiries to the

following internet address: 9-A WASBREFA@faa.dot.gov.

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 VI.

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

VI 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 VI

speed and then brought to a complete

stop. This distance is known as the

accelerate-stop distance.

The choice of V I speed affects the

accelerate-go and accelerate-stop

distances. A lower VI 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 V Ispeed decreases the

accelerate-go distance and increases the

accelerate-stop distance. When V 1 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 V 1 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
Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations 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. SR422, 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 VI with a distance

equal to two seconds at the VIspeed.

The distance equal to two seconds at

constant VI, while shorter than that

resulting from the continued

acceleration beyond VI required by

Amendment 25-42, is a distance margin

that must be added to the acceleratestop 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 VI 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. VI 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 VI 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 VI

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
8300 Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations

determined with brakes that are worn to

their overhaul limit. Lastly, the two

seconds of continued acceleration

beyond VI speed would be replaced by

a distance equal to two seconds at VI

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 OAA) of Europe to promote

harmonization between the FAR,

particularly the airworthiness standards,

and the European Joint Aviation

Requirements OAR). 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.

Berrnann, Columbia University School

of Law, in May 1991 as a consultant to

the Administrative Conference of the

United States (ACUS). A copy of

Professor Berrnann'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 Berrnann'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

rule making 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 VI

(mandated by Amendment 25-42) with

a distance margin equal to two seconds

at VI 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 acceleratestop distance prescribed in §25.109 by

replacing the two seconds of continued

acceleration after reaching VI with a

distance equal to two seconds at VI

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 VI,

rather than from the speed reached after

two seconds of acceleration beyond VI).

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 §25.109, as applied to the

certification of recent U.S.-

manufactured airplanes.

Proposal 2

The FAA proposed to amend § 25.105

to require that airplane takeoff

performance data be based on wet, in
Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations 8301

addition to dry, runways. Section

25.l587(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

§ 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 onehalf 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, §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 §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 VI 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 (Le., 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

§25.113 would not permit the

combination of clearway credit and a

l5-foot screen height. The FAA

proposed to modify § 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 §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

§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)
8302 Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations

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

§ 25.101 (f) 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 §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" (VI) 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 § 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 V J 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 § 1.2 to add the

definition of VEF, which currently

appears in §25.107(a)(I). 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 §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 ]AA issued substantively the same

proposals to amend ]AR-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 ]AA 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

provtsions. would have been
Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations 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 OAR-OPS 1). In this

NP A, 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 VI 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 VI.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 ajoint 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
8304 Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations

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 (VI)' 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 VI

speed.

The diversity displayed in the

comments illustrates a great deal of

misunderstanding and disagreement

regarding the definition and use of the

VIspeed. In general. inconsistent

terminology used over the years in

reference to VI has probably contributed

to this confusion. As noted by the

cornmenters, VI 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. SR422, effective August 27,1957,

originally referred to VI 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

VI, 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

VI. For certification purposes, the FAA

considered VI 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 VI, and delays in accomplishing

each subsequent action for stopping the

airplane were applied after VI. Allowing

for the time delays, the actual engine

failure was therefore assumed to occur

prior to VI.

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. VI 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 pilafs

decision process. The preamble to

Amendment 25-42, however, states that

"VI 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 pilafs

application of the first retarding means

during accelerate-stop tests." This same

definition was codified as §25.107 (a)(2).

Not only is VI 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 VI, 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 VI.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 VI.

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 VI. The

method of determining this adjustment

has varied, but the objective has always

been the same-to provrde 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 VI. 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 pilafs

first action determines VI, there are

typically two pilot actions occurring

after VI. 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 VI, 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 VI 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 VI

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

VI speed to be the minimum acceptable
Federal Register / Vol. 63, No. 32/ Wednesday, February 18, 1998/ Rules and Regulations 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, VI 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 VI 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 cornmenter'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 VI

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

§25. 107(a)(2). The proposal to define

takeoff decision speed in § 1.1 is also

withdrawn. The adopted definition

represents a change to the definition of

V1 in § 1.2, rather than an addition to

§ 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 VI concept.

The proposed addition of the

definition for VEF to § 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 §25. 107 (a)(l) by

Amendment 25-42. The amendment

adopted in this rule adds the existing

definition for VEF to the list of

abbreviations and symbols in § 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

§ 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 §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 cornmenter's goal.

Section 25.10 1(e) does not require

applicants to establish an optimum

configuration to meet the applicable

requirements. Instead, §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 §25.1 05(a) (2) to require the

takeoff data to be determined in the

optimum configuration for the takeoff

conditions specified in §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 cornmenter'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
8306 Federal Register I VoL 63, No. 32 I Wednesday, February 18, 1998 I Rules and Regulations

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

§25.101 (r). 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

§25.735(g). The FAA concurs with the

intent of this suggestion. Instead of

modifying the proposed §25.101 (i),

however, the FAA is revising the

proposed §25.735(g) and relocating it as

a new §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 §25.735(g).

A commenter proposes a wording

change to §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 com menter, joined

by a second com menter, proposes that

§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 acceleratestop 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, §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
Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations 8307

amend § 25.109 to replace two seconds

of acceleration beyond V1 speed with

the distance traversed in two seconds at

VI 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-engineinoperative and all-engines-operating

accelerate-stop distances. as required by

the proposed §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 VI." Also, the

proposed distance traversed during two

seconds at VI speed is the same for both

cases. as is the deceleration distance

from V] 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

VI 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 VI. as

discussed earlier, is one second. During

the period after VI. 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 acceleratestop distances. the operating engines (on

a turbojet powered airplane) will

continue to produce forward thrust.

Therefore (for turbojet airplanes). the

distance to stop from VI 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 allengines-operating case as opposed to the

one-engine-inoperative case depends on

the time intervals between VEF and VI.

VI 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 allengines-operating. In general, the FAA

expects the dry runway accelerate-stop

distances to be based on the all-enginesoperating 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 VI.

In reviewing the comments. the FAA

discovered that the proposed wording

for §25.109 (a) could be interpreted such

that speeds greater than VI need not be

considered in determining the

accelerate-stop distances. However. the

airplane will typically exceed VI speed

during the stop. particularly with allengines-operating. even when the pilot

applies the brakes at V]. The proposed

amendments to §25.109(a) have been

modified to clarify that the acceleratestop distances must include the highest

speed reached during the rejected

takeoff maneuver. As modified. these

proposed amendments to §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

approx imation to the significantly
8308 Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations

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 VI 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 § 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 cornrnenter'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 (Le., 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 cornmenter'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 cornmenter'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

cornrnenter'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, §25.109(b) has been

revised and new §§ 25.109 (c) and (d)

have been added to prescribe wet

runway accelerate-stop distance

standards in a manner consistent with

the cornmenter'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

cornrnenter'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

§ 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 § 25.109(c) (1) for
Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations 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, § 25. 109(c)(l) 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.

ESOU 71026 provides braking data for

both ribbed and smooth tires on

runways of different surface textures. A

method is also provided in ESOU 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 1hz inch (l.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 §25.109(c)(l) are based on

a tire tread depth of 2 mm. Since the

tread depth of new tires is usually 10-

12 rnm, 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

ESOU 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

"0" 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

§ 25.109(c)(l), 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 § 25.109(c)(l) represent a

well-soaked runway, but with no

significant areas of standing water.

In summary. the curves prescribed in

§ 25. 109 (c)(l) 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 ESOU 71026 for

runway surface categories Band C,

adjusted to represent tires with 2 mm

tread depth remaining. and extrapolated

to cover the range of VIspeeds 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,

§ 25. 109(b)(2)(i) limits the stopping

force from the wheel brakes used to

determine the wet runway acceleratestop distance to the stopping force

determined in meeting the requirements

of § 25.10 1(i) (worn brakes) and

§ 25.1 09(a) (the dry runway acceleratestop 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, § 25. 109(c)(2) requires

applicants to adjust the maximum tireto-ground wet runway braking

coefficient determined in § 25. 109 (c)(l)

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 §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

§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 § 25.735. Therefore, for applicants

using the anti-skid efficiency values

specified in § 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, § 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
8310 Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations

Anti-Skid Systems." The efficiency

values prescribed in § 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 reapplied 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 preprogrammed 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 .instrurnentation. 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, §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 (l.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 (r.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 §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 §§ 9 1.605 (b)(3), 121.l89(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
Federal Register/Vol. 63, No. 3Z/Wednesday, February 18, 1998/Rules and Regulations 8311

airworthiness and operating rules is

maintained.

The FAA did not intend, by the

proposed wording §§ 9 1.605 (b)(3),

121.l89(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

§§ 91.605(b)(3), 121.l89(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

cornmenters' 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 0 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 § 25.1 09(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

§ 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)(l) 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 § 25. 109(d) is

revised to remove the words "smooth"

and "hard-surfaced" and redesignated

as §25.l09(h).

Section 25.l533(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,

§§91.605(b)(3), 121.l89(e), and

l35.379(e) of the operating rules are
8312 Federal Register/Vol. 63, No, 32/Wednesday, February 18, 1998/Rules and Regulations

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 acceleratestop 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 acceleratestop 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 150/5320-128 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.l95(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 §§ 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 § 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 § 25.1 09(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 §§ 25. 109(c) and

25.1309, the FAA already reviews the

system operation and intercompatibility issues that would be

addressed by the com menter's proposed

changes to §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
Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations 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 cornrnenters' 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, §§ 25. 109(c)

and (d) are amended as proposed in

NPRM 93~8, except that they have been

re-designated as paragraphs (e) and (t),

respectively.

As part of the proposed wet runway

standards, §§ 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

cornrnenter's proposed change to

§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

VIspeed can be used. The effect of

lower VI 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 VIspeed,

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 §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 § 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 §§ 25.ll3(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 l5-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 § 25.113

accordingly. The phrase "but not

beyond the end of the runway,"

contained in the proposed

§25.ll3(b)(2), is removed. The

proposed § 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
8314 Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations

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, § 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§§25.109(b)(l) and 25.ll3(b)(l).

These sections require the acceleratestop and takeoff distances on a wet

runway (at the wet runway VI 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

§25.ll5(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, § 25.ll5(a) is amended as

proposed.

The FAA received several comments

on the proposed changes to § 25.735.

One commenter proposed that

§ 25.735 (f) refer to the wear condition

that provides the least effective braking

performance. This comment is related to

a similar comment regarding § 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 § 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 § 25.735(g) refer to the most severe

stop rather than a rejected takeoff.

The flight test proposed in § 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 § 25.735(g) should include

a two-second overshoot of VI, before

applying the brakes, to allow for the

average pilot response time. The FAA

does not concur with this comment

because VI 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

§ 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 § 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 § 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 § 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

§ 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
Federal Register/Vol. 63, No. 32/Wednesday, February 18, 1998/Rules and Regulations 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 § 25.735(f) and the TSO, any

change to the definition of the energy

level in § 25. 735(f) would presumably

also apply to the TSO. Since the TSO

l Otl-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

cornrnenter, 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 § 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

§ 25.735(f)(2) is relevant.

The FAA concurs with these

proposals. As amended. § 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

§ 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 l Ou-stop test may

begin with a brake in any condition

representative of service use. including

new. In addition. a new § 25.735(h).

based on JAR 25.735(h). has been added.

This section is similar to § 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

§ 25.735(f) (2) and the new § 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 § 25. 735(f) (2).

with respect to this provision. has been

adjusted to conform to Federal Register

formatting guidelines. and the new

§ 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 § 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-C 135.

One commenter suggests that the

proposed § 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

§ 25. 735(g) has been reworded to clarify

that the airplane must stop within the

accelerate-stop distance and is adopted

as § 25.109(i). Existing § 25.735(g),

which would have been redesignated as

§ 25.735(h). remains as § 25.735(g) in the

adopted rule.

The FAA received one comment

regarding the proposed amendment to

§ 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 § 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

§ 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 §25.1587(b) has

been removed. and §25.1533(a)(3) is

revised accordingly. The adopted

amendment also corrects a

typographical error in existing

§25.1533(a). identified by this

cornrnenter, by replacing the reference

to § 25.103 with a reference to § 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

comrnenter, 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
8316 Federal Register / Vol. 63, No. 32/ Wednesday, February 18, 1998/ Rules and Regulations

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.

H 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 §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 §25.111, §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: (l)

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: (l) 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- VI 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 Z-second-at-V, 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
Federal Register I Vol. 63, No. 32 I Wednesday, February 18, 1998 I Rules and Regulations 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 nineairplane 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. l534(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 anyone 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 tradesensitive 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 OAA)

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
8318 Federal Register IVaI. 63, No. 32 I Wednesday, February 18, 1998 I Rules and Regulations

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

I. 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

"V I" to read as follows:

§1.2 Abbreviations and symbols.

* * * * *

VEF means the speed at which the

critical engine is assumed to fail during

takeoff.

* * * * *

V I 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. V I 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:

§25.101 General.

* * * * *

[i) The accelerate-stop and landing

distances prescribed in §§ 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 § 25.105 is amended by

revising paragraph (c)(1) to read as

follows:

§ 25.105 Takeoff.

* * * * *

(c) * * *

(1) In the case ofland planes and

amphibians:

(i) Smooth, dry and wet, hardsurfaced runways; and

(ii) At the option of the applicant,

grooved or porous friction course wet,

hard-surfaced runways.

* * * * *

6. Section §25.107 is amended by

revising paragraph (a)(2) to read as

follows:

§25.107 Takeoff speeds.

(a) * * *

(2) VI. in terms of calibrated airspeed,

is selected by the applicant; however, VI

may not be less than VEl' 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), (t), and (i) to read as follows:

§ 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;

(Il) 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 V I 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 V I 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

VI for takeoff from a dry runway; and

(n) 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.
Federal Register/Vol. 63, No, 32/Wednesday. February 18. 1998/Rules and Regulations 8319

Maximum Brakin~ Coefficient (tire-tQ-~round)

~t/g =-o.0350(y'-)3 +0.306 (y'-)2 -0.851 (Y.-)+0.883

MAX 100 100 100

~tl = -0.0437 (y'-)3 +0.320 (y'-)2 -0.805 (y.-)+ 0.804

gMAX 100 100 100

II = -0.0331 (y'-)3 + 0.252 (y'-)2 - 0.658(y.-) + 0.692

r~MAX 100 100 100

II =-0.0401 (y'-)3 +0.263 (y'-)2 -0.611(Y.-)+0.614

rt/gMAX 100 100 100

(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 ofVEF

and VI are used. In determining the wet

runway accelerate-stop distance. the

Tjre Pressure (psi)

50

100

200

300

BilliNG CODE 491G-13-C

WhereTire Pressureernaximum airplane

operating tire pressure (psi);

IltigMAX=maximum tire-to-ground

braking coefficient;

Ve 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

stopping force from the wheel brakes

may never exceed:

(t) The wheel brakes stopping force

determined in meeting the requirements

of § 25.10 I (i} and paragraph (a) of this

section; and

(il) 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 un braked wheels at the most

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)(I) of this section must be

multiplied by the efficiency value

associated with the type of anti-skid

system installed on the airplane:

EffiType of anti-skid system ciency

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

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

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 acceleratestop distance; or

(2) The wet runway braking

coefficient defined in paragraph (c) of

this section. except that a specific antiskid 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
8320 Federal Register/Vol. 63. No. 32/Wednesday. February 18. 1998/Rules and Regulations

Tire Pressure (psi) Maximum Braking Coefficient (tire-to-ground)

50 f.J = 0.1470(~)5 -1.050 (~)4 +2.673(~)3 _2.683(~)2 +00403 (~) +0.859

t/gMAX 100 100 100 100 100

100 f.1tJg

MAX

=O.1ICX)C~5 -0.813C~ 4+2.130C~3 -2200C~2 +0.317C~) +0.807

200 f.1t/gMAX =0.0498C~)5 -0.398C~4 +1.140C~3 -1285C~2 +0.140C~+O.701

300 f.1t/gMAX =0.0314C~5 -0247C~Y +0.703C~3 -O.779C~2 -o.<X1J54C~+0.614

BilLING CODE 4910-13-C

WhereTire Pressure.-rnaxtrnum airplane

operating tire pressure (psi);

/ltigMAx=maximum tire-to-ground

braking coefficient;

Veairplane 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)(l). redesignating paragraph (b) as

paragraph (c) and revising it. and adding

a new paragraph (b) to read as follows:

§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 §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 §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

§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 § 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 V, before reaching 35

feet above the takeoff surface. as

determined under §25.111 for a wet

runway; or

(H) 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 §25.111.

9. Section 25.115 is amended by

revising paragraph (a) to read as follows:

§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

§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:

§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.
Federal Register/Vol. 63, No. 32/Wednesday, February 18. 1998/Rules and Regulations 8321

2

KE = 0.0443WY

N

WhereKE=Kinetic energy per wheel (ft.vlb.):

W=Design landing weight (lb.);

Y=Airplane speed in knots. V must not

be less than Vso.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:

(l) The brake kinetic energy

absorption requirements must be based

on a rational analysis of the sequence of

events expected during an acceleratestop 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:

KE = 0.0443WY2

N

WhereKE=Kinetic energy per wheel (ft.-lb.);

W=Airplane weight (lb.);

V=Airplane speed (knots);

NeNurnbcr of main wheels with brakes;

and

Wand 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:

§ 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 §§ 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:

§ 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 121-0PERATING

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:

§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 135-0PERATING

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:

§ 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 491Q-13-M
J 0 I N T CENTER

AEI-BROOKINGS JOINT CENTER FOR REGULATORY STUDIES

Improved Standards for Determining Rejected Takeoff and

Landing Performance

Regulatory Impact Analysis

Department of Transportation

Office of Aviation Policy and Plans

RIN: 2l20-ABl7

63 Federal Register 8298

February 18, 1998

This analysis was issued by the agency and collected by the AEI-Brookings Joint Center in order

to promote regulatory transparency. The views expressed in this document are those of the

agency and do not necessarily reflect those of the Joint Center.
U.S. Department of

Transportation

FEDERAL AVIATION

ADMINISTRA nON

Washington, D.C. 20.591

FINAL REGULATORY EVALUATION,

FINAL REGULATORY FLEXIBILITY DETERMINATION,

AND TRADE IMPACT ASSESSMENT

IMPROVED STANDARDS FORDETERMnaNG

REJECTED TAKEOFF AND LANDING PERFORMANCE

Final Rule

(14 CFR Part 25)

Office of Aviation Policy and Plans

Aircraft Regulatory Analysis Branch, APO-320

Gregory v, Won

March, 1996
Table of Contents

Executive Summary......................................................... i

I. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

I I. Description of Rule....... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

A. Definitions...................................................... 2

B. Two-second margin. . .. . . .. . .. .. . . . .. . . ... .. . . . . . .. . . . .. . . . . . . . . . . . 3

C. Worn brake accountability.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

D. Wet runway operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

III. Evaluati9n of Net Costs................ .. . . . 6

A. Net cost {savingS} estimation procedures................. 6

1. Cost function derivation................... 6

2. Cost function parameters........ 8

3. Hypothetical production program assumptions 12

B. Effects of the revised two-second margin 12

C. Effects of the worn brake provisions 13

1. Estimated incremental impact............................... 14

2. Cost mitigating factors........ . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15

D. Effects of the wet runway provisions 15

1. Estimated incremental impact 15

2. Cost mitigating factors............................ . . . . . . .. 16

E. Net costs........................................................ Ls

1. Incremental certification costs. . . . . . . . . . . . . . . . . . . . . . . . . . .. 19

2. Net operating costs... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20

IV. Safety Aspects of the Rule 22

A. Safety benefits of the worn brake provisions 22

B. Safety benefits of the wet runway provisions 22

V. Regulatory Flexibility Determination 24

VI. Trade Impact Assessment ".. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26

Appendix: Derivation of costs by brake design
Ex.eu tive Summary

This Regulatory Evaluation considers the economic impact of a final rule that

will amend parts 1, 25, 91, 121, and 135 of Title 14 of the Code of Federal

Regulations (CFR). The rule, based on Notice of Proposed Rulemaking (NPRM)

93-8 published in the Federal Register on July a, 1993 (58 FR 36738), will:

(i) amend 14 CFR part 1 to further clarify the term "Vi'"

(ii) revise the requirement that accelerate-stop distances include a

margin equal to 2 seconds of continued acceleration after the airplane

has reached V1,

(iii) require accelerate-stop distances and landing distances that

reflect the true stopping capability of brakes at their maximum wear

limit, and

(iv) require performance accountability for takeoff on wet runways.

jhe rule

/ airplanes

is intended to enhance the safety of future transport category

during takeoff and landing. The new standards will affect future

transport category airplane type certifications. In addition, airplanes that

have been type certificated under the existing rule will be eligible, at the

manufacturer's discretion, for recertification under the new requirements.

Benefit-cost analysis. In order to analyze the potential 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 2S year design service goal, and 6)

the discount rate is 7 percent.

~ concludes that the benefits of the rule will exceed its costs. rn .

particular, assuming a brake design in which performance declines with wear,

the rule will increase costs (including certification and lifetime operating

costs) by about $69,800 per airplane ($19,000 discounted). The majority of

new type certifications, however, will incorporate brake designs that do not

exhibit a significant reduction in braking performance with wear. In thts

case, the rule will reduce discounted lifetime costs per airplane by $57,800

($15,000 discounted).

Additional safety considerations. The rule has significant safety

implications owing to the fact that it creates incentives for manufacturers,

operators, and airports to adopt procedures which reduce takeoff hazards. 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

takeoffs.

The rule also enhances safety by taking into account wet runway

First, it directly increases accelerate-stop distances on wet

second, it creates an economic incentive to develop more stringent

distances.

runways.

maintenance programs for skid-resistant runway surfaces.

ii
Regulacory flexibilicy determinacion. The Regulatory Flexibility Ace of 1980

was enacted by Congress to ensure that small entities are not unnecessarily

and disproportionately burd~ned by government regulations. While there are no

manufacturers of transport category airplanes thae meet the FAA's definition

of a small entity, some small air carriers could be affected by the rule.

The regulator¥ flexibility determination assumes: 1) ehe most severe

operating cost penalties, and 2) that all incremental certification costs are

passed on to the operator in the form of higher airplane prices. Under these

assumptions, an upper-bound estimate of the annual impact of the rule to small

operators is approximately $25,434. Under FAA Order 2100.14A, the threshold

for "significant economic impact" is $123,445 for operators whose fleets

consist entirely of aircraft having a seating capacity of more than bb

passengers and $69,005 for other operators. FAA holds, therefore, that the

rule will not have a significant economic impact on a substantial number of

small entities.

International 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 affect of lessening the restraints of any erade-sensitive

activity. 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 of

iii
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 certificated under Amendment 25-42 to

become slightly more competitive against current production U.s. airplanes

that were not certificated under Amendment 25-42 by marginally expanding their

takeoff envelope.

~.

iv
Improved Standards for Oetermining

Rejected Takeoff and Landing Performance

I. Introduction

This Regulatory Evaluation considers the economic impact of a final rule that

will amend parts 1, 25, 91, 121, and 135 of Title 14 of the Code of Federal

Regulations (CFR). The rule, based on Notice of Proposed Rulemaking (NPRM}

93-8 published in the Federal Register on July 8, 1993 (58 FR 36738), will:

(i) amend 14 CFR part 1 to further clarify the term "V1, II

(ii) revise the requirement that accelerate-stop distances include a

margin equal to 2 seconds of continued acceleration after the airplane

has reached V 1'

(iii) require accelerate-stop distances and landing distances that

reflect the true stopping capability of brakes at their maximum wear

limit, and

(iv) require performance accountability for takeoff on wet runways.

The rule is intended to enhance the safety of future transport category

airplanes during takeoff and landing. The new standards will affect future

transport category airplane type certifications. In addition, airplanes that
have been type certificated under the existing rule will be eligible, at the

manufacturer's discretion, for recertification under the new requirements.

II. De.cription of Rule

The rule includes numerous individual amendments that address different

aspects of ta!5eoff and landing safety. In order to understand the various

effects of the rule, the individual amendments are organized into categories'

of associated provisions where each grouping addresses a particular aspect of

the overall regulatory initiative.

following sections.

These groupings are described in the

A. Definitions

The rule will amend 14 CFR §1.2 by adding two definitions, "VEF" and "V1·" VEF

will be defined as the speed at which the critical engine is assumed to fail

during takeoff. V1 will denote 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

will also mean 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. No significant costs or benefits are directly attributed to these

definitions, and they are not considered further in the evaluation.

2
8. Two-second margin

Under current certification requirements, the determination of accelerate-stop

distances must include a distance equal to two seconds of continued

acceleration after the airplane has reached V1

(current 14 CFR

§25 .109 (a) (1) (ii)] . The rule will reduce this margin to the distance traveled

during two ,s.econds at a constant speed of (amended 14 CFR

§25 .109 (a) (1) (iv)]. While this provision will apply to 'future

certifications, airplanes that have been certificated under the existing rule

will be eligible, at the manufacturer's discretion, for recertification under

the new procedure.

C. Worn brake accountability

The rule includes several associated requirements concerning the

accountability for worn brake assemblies in determining stopping distances and

braking capacity ratings. These provisions were generated in response to a

rejected takeoff accident where worn brakes were identified by the National

Transportation Safety Board (NTSB) as a major factor in the accident.

Currently, brake ratings and stopping distances are typically established

using new brakes. Investigations by the NTSB and the FAA have determined that

new brakes can produce higher maximum deceleration rates than brakes, within

the range of allowable wear, that exist on airplanes in service.

The rule will require that accelerate-stop and landing distances be determined

with all of the airplane's brake assemblies at the fully worn limit of their

allowable range (amended 14 CFR §25.101(i)]. In conformance with this

3
provision, the rule will require that a flight test demonstration of the

maximum kinetic energy rejected takeoff be conducted with the brakes at not

more than 10 percent of their allowable wear range remaining [amended 14 CFR

§25.109(il]1. Each of these provisions will apply to future transport

category certifications.

D. Wet runway operations

Current regulations governing stopping distances and takeoff speeds do not

differentiate between wet and dry runways. Paragraph 25.105 (c)(1) will be

amended by adding wet runways to the existing list of conditions on which

takeoff data must be based. Accordingly, 14 CFR §2S.109 will be amended to

establish a separate procedure for the determination of accelerate-st~

distances on wet runways. This distance will be the longer of either the

accelerate-stop distance on a dry runway, or the accelerate-stop distance

determined on a wet runway where reduced braking capability is assumed.

NPRM 93-8 had originally proposed that, unless the wet runway wheel brakes

stopping force is demonstrated by flight testing using worn tires, the wet

runway accelerate-stop distance must be determined using a wheel brakes

stopping force equal to 50 percent of that used to determine the dry runway

accelerate-stop distance. This criterion was based on data published in

Engineering Science Dat~ Unit (ESDU) 71026, Frictional and Retarding Forces on

Aircraft Types--Part II: Estimation of Braking Force, which showed that the

1 The rejected takeoff demonstration is an actual flight test where the. lower

wear provision is necessary to assure test safety.

4
wet runway braking coefficient can be approximated by one-half the dry braking

coefficient.

Based on public comments, however, FAA has revised the original wet runway

provisions. In the final rule, the maximum tire-to-ground wet runway braking

coefficient of friction will be computed as a function of ground speed (based

on ESDU 71026 data). This generic relationship between braking coefficient

and speed will then be adjusted to account for the capabilities of specific

airplane types. The revised procedure will more accurately reflect: 1)

variations in braking capability with velocity and tire pressure (amended 14

CFR §25.109 (c)(1)], 2) the effectiyeness of the airplane's anti-skid braking

system (amended 14 CFR §2S.109(c) (2»), and 3) the friction characteristics of

the runway surface (amended 14 CFR §25.109(d)].2

The rule, however, retains two other provisions that will offset some of the

effect of these amendments. First, the rule will allow a ls-foot minimum

necessary screen height at the end of the runway and a 15-foot vertical

obstacle clearance throughout the flight path. currently I both of these

limits are set at 35 feet [amended 14 CFR §2S.113(b)]. Second, the rule will

permit credit for the use of reverse thrust (amended 14 CFR §25.109(f)).3

2 In addition to the variables enumerated above, ESDU 71026 data show that

wet runway accelerate-stop distance is affected by other variables such as

tire tread condition and water depth. The standards defined in amended

§25.109(c) and (d) account for these other variables by assuming conditions

most likely to be encountered in service.

3 Under existing regulations I screen height clearance at the end of the

runway can be as little as 13 feet (depending on the airplane) when a clearway

is present. Paragraph 25.113, as amended, will not permit the coffiUinationof

clearway credit with the wet runway lS-foot screen height requirement.

Similarly, the amendment ensures that the presence of a clea.cway does not

result in a longer runway requirement than would be the case in the absence of

a clearway. It should be emphasized that the minimum screen height and

reverse thrust provisions apply only to the wet runway case.

5
The rule will also require that Airplane Flight Manuals (AFM) for newly

certificated part 25 aircraft incorporate performance information for wet

runway surface conditions. Changes to 14 CFR parts 91, 121 and 135, then,

will require operators to account for wet runway takeoff performance in

accordance with AFM procedures.

III. svaluation of Nat Coata

A. Net cost (savings) estimation procedures

1. Cost function derivation

Estimates of the costs (or savings) associated with various provisions of the

rule are based on a stylized model of transport airplane performance. Data

provided by the Air Transport Association (ATA) in response to a request from

the FAA indicate that approximately 0.5 percent of takeoffs are field-length

limited. Another 0.5 percent of takeoffs are within 400 feet of being fieldlength limited. Under the assumption that this relationship is approximately

linear, the incremental proportion of field-length limited departures (per

1,000) can be described by the following function:

f(x) = d +C~)x

6
Where "a" as the proportion of field-length limited departures assuming no

change to the existing (amendment 25-42) requirement, and "X" is the

incremental change in the required field length (see figure) .

The number of field-length constrained takeoffs per airplane per year (where

accelerate-stop distance is the limiting factor) can be expressed as:

g(x) :::adf(x)

Where d is the number of departures per airplane per year (in 1,000's) and a

is the proportion of takeoffs limited by accelerate-stop distance.

A cost function, relating the incremental field-length requirement fo

incremental cost, is then given by:

Where w is the weight (in pounds) that must be removed per foot increase in

the accelerate-stop distance (offload penalty), and c is the cost (in dollars)

per pound of payload removed.

Therefore, the cost imposed on operators by increasing the accelerate-stop

distance requirement by "L" feet is given by:

7
·L

fh(X)dX

o

Similarly, the savings associated with reducing the accelerate-stop distance

by "L" feet is given by:

o

fh(X)dx

-L

2. Cost function parameters

The rate of field-length limited takeoffs under Amendment 25-42. "a" is .a

measure of the rate of field-length limited takeoffs under Amendment 25-4:4-.

On the basis of performance data provided by the Aerospace Industries

Association of America (AIA), FAA estimates that the average effect of

Amendment 25-42 on the balanced field length is 150 feet. Therefore, us ing

the relationship derived from ATA takeoff data, FAA estimates that "a" is

6.875 (that is, approximately 7 field-length constrained takeoffs per 1,000).

The number of departures per aircraft per year. The number of departures per

aircraft per year, "d", is estimated as the average number of annual

departures per airplane operated by large certificated air carriers. (see

table 1) .4

4 Prior to the adoption of Commuter Operations and General Certification and

operations Requirements (amendments 91-245, 119, 121-251, 125-23, 127-45, 135-

58, SFAR 50-2, SFAR 71 and SFAR 38-12), 10 to 19 passenger seat, commuter

category airplane designs were type certificated under 14 CFR part 23, and,

therefore, were not required to demonstrate accel~rate-stop distance. Under

the "commuter rule," future 10 to 19 seat airplane designs must be type

certificated under 14 CFR part 25. No such designs are being proposed for the

8
Takeoffs where accelerate-stop distance is the controlling factor. FAA

estimates that "a," the proportion of takeoffs limited by the accelerate-stop

distance, is approximately 6b percent.s

Table l.--Departures per airplane per year6

Domestic departures, large cert. air carriers (1992)

Majors 5,870,136

Nationals 1,062,019

Large Regionals 352,424

Medium Regionals 36,013

Total 7,320,592

Active fixed-wing aircraft (1992)

Majors 3,696

Nationals 596

Large Regionals 371

Medium Regionals 166

Total 4,829

Departures per aircraft (1992)

Majors 1,588

Nationals 1,782

Large Regionals 950

Medium Regionals 217

Total 1,516

foreseeable future, however, so consideration of commuter category aircraft is

omitted from this analysis. For a complete discussion of the impact of part

25 performance requirements on part 23, SFAR 41, and pre-SFAR 41 commuter

category airplanes see" Final Regulatory Evaluation and International Trade

Impact Assessment: Commuter operations and General Certification and

Operations Requirements, FAA APO, October 17, 1995

5 It should be noted, however, that changes in stopping distance assumptions

~ssociated with this proposal could affect this percentage.

6 Sources: Number of active aircraft: FAA Census of U.S. Civil Aircraft

(1992, the latest year for which complete Census data are available).

Departures for large certificated air carriers: Department of Transportation,

Research and Special Projects Administration (RSPA), Air Carrier Traffic

Statistics Monthly.

9
Figure.--Field-length limited takeoffs as a function of

The change in required field length

Vertical axis: Rate of field·length lim led takeoffs (per 1.000 departures)

tt« } = a • 0 0 I 2 SA

-L o +L

Change in required field length from existing requirement

Weight penaley per fooe of addieional required field length. Based on

performance data for six transport category airplane models, FAA estimates

that approximately 32 pounds must be offloaded per foot of field length

deficit.

The case per pound of passenger/cargo offload. IIc" r the cost per pound

removed, is approximately $0.29. This estimate includes an adjustment for the

fuel consumption savings that would result from offloading. Depending on the

type of airplane, fuel consumption savings range from [10.088 x 10'3) to

[3.528 x 10'») gallons per hour per pound. The adjustment to "c"--

approximately $0.02 per pound per trip--is the average savings for six

airplane models, weighted by the average trip flight duration for each model

10
(assuming the price of jet fuel to commercial operators is approximately

$0.66) . The unadjusted cost per pound of weight offloaded is approximately

$0.31 (see table 2).'

Table 2.--Derivation of cost per pound offload8

Domestic revenue (1000's)

1 Passenger $49,742,274

2 Freight $ 4,265,978

o· 3 Mail $ 1,054,436

4 Total- $55,062,688

Revenue ton miles (1000)

5 Passenger 52,958,086

6 Freight 14,135,480

7 Mail 2,301,732

8 Total 69,395,298

Revenue per ton mile

9 Passenger $0.94

10 Freight $0.30

11 Mail $0.46

12 Total $0.79

13 Average Trip Length (miles) 780

14 Unadjusted cost per pound-trip $0.31

15 Fuel consumption adjustment $0.02

16 Adjusted cost per pound-trip $0.29

7 See: Washington Consulting Group, Impact of weight Changes on Aircraft

Fuel consumption, March 17, 1994.

8 Table notes: Rows. 1-4: Total domestic revenue (thousands of dollars),

Department of Transportation, Research and Special Projects Administration

(RSPA), Office of Airline Statistics, Air Carrier Financial Statistics, first

quarter, 1995. Rows 5-8: Total revenue ton.miles (thousands), DOT RSPA, Air

Carrier Sta tistics Monthly, March, 1995. Rows 9-12: Revenue per ton-mile

equals domestic revenue divided by revenue ton miles. Row 13: Average

passenger trip length, FAA Aviation Forecasts, Fiscal Years 1995-2006, Table 7

(rounding of 1996 forecast). Row 14: Unadjusted cost per pound trip equals

[(average revenue per ton mile!2000) 1 x 7BO. Row IS: Fuel consumption

savings adjustment. Row 16: Adjusted cost per pound trip.

II
3. Hypothetical production program assumptions

In ozder to analyze the potential net costs of the rule, the cost model is

applied to 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 enterl!'service in year "S", 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.

8. Effects of the revised two-second margin

The existing standard (implemented under Amendment 25-42) requires that

accelerate-stop distances for both the one-engine inoperative and the allengine operative conditions must include the calculated distance traveled

during 2 seconds of continued acceleration after V1 is reached. Although this

requirement has been in place since 1978, the majority of airplane models

certificated during the intervening period were determined to be derivatives

of earlier models, and as such, were not subject to the provision.

The rule will replace the required distance traveled during two seconds of

continued acceleration with the distance traveled during two seconds at

constant V1. This individual provision will shorten the required acceleratestop distance by an estimated 150 feet on average (see section III.A.2). The

reduction will only apply to future type certifications, but airplanes that

12
have been certificated under the existing rule will be eligible, at the

manufacturer's discretion, for recertification under the new procedure. 9

It is important to note that', considered alone, this provision is unacceptable

because it will reduce takeoff safety margins. It is included only because

other provisions in the rule will significantly increase overall safety. The

two-second distance requirement in Amendment 25-42 represents a generic safety

margin that, in practice, has not been applied comprehensively. By.

comparison, the new requirement will be based on the performance capabilities

of each airplane and the specific conditions under which it is operating.

C. Effects of the worn brake provisions

As previously described, the rule includes several associated provisions that

will require manufacturers to account for worn brake assemblies in determining

stopping distances and braking capacity. This will only apply to future

airplane model certifications and will affect both certification and operating

costs.

9 Recertification co.sts associated with this provision are approximately

$185,235. This includes the costs of certification data substantiation,

airplane flight manual revisions, revisions to operations manuals, and airport

analysis revisions. In addition, manufacturers applying for recertification

would have to demonstrate compliance with the other provisions of this rule.

Therefore, total recertification costs could total several hundred thousand

dollars. The rule does not mandate recertification; this decision will

reflect the economic and safety considerations on the part of airplane

manufacturers and operators. Thus, recertification is not analyzed further in

this evaluation.

13
1. Estimated incremental impact

In comments to NPRM 93-8, A~A points out that FAA failed to consider potential

incremental certification costs associated with the worn brake provisions of

this rule. In particular, the rule might require manufacturers to conduct

addi tional dynamometer tests to generate correction factors to the standard

flight test stopping-distance data. The effort to create these correction

factors, AlA argues, is new and. according to one manufacturer, could cost as.

much as $450,000.10 FAA concurs and the economic analysis has been revised

accordingly.

Engineering estimates suggest that accountability for worn brakes will add an

average of 150 feet to the calculated minimum necessary field length fC!tr

airplanes equipped with steel brakes. This requirement could necessitate a

weight reduction in those cases where takeoff is near field-length limited.

However, it should be emphasized that these costs will only apply to new

airplane models with steel brakes that are certificated in the future. Wear

is considered to have a negligible effect on the braking force of carbon

brakes and the majority of future transport category airplanes will use carbon

brakes .11

,10 This cost assumes that the worn brake amendments require five additional

dynamometer tests each costing $90,000: $60,000 for hardware; and $30,000 for

instrumentation and pre- and post-test analysis.

11 The steel-carbon dichotomy is used as a shorthand way to differentiate.

alternative brake technologies, and is intended to simplify the economic

exposition. In fact, some steel brake designs do not exhibit the same

reduction in brake force associated with wear.

14
2. Cost mitigating factors

An important potential cost mitigating consideration is omitted from the

analysis of the worn brake provisions of this rule. Allowable brake wear is,

to some degree, a design variable that depends on brake hardware, the length

of time between brake overhaul, and the cost of overhaul. Reducing allowable

wear, ceteris paribus, increases the coats of brake maintenance (by shortening

the interval between brake overhauls). Under the current regime, there is no

explicit regulatory incentive for manufacturers or operators to trade off

increased brake performance (at least to the extent that such performance

affects accelerate-stop distance) against life cycle brake overhaul costs.

The rule places greater emphasis on this trade-off. Potentially, then,

accelerate-stop distance will not be affected to the degree assumed in this

evaluation: operators could purchase shorter distances by reducing allowable

wear (to the point at which marginal brake overhaul costs are less than or

equal to the marginal revenue associated with less restrictive accelerate-stop

distances) .

D. Effects of the wet runway provisions

1. Estimated incremental impact

The net effect of the wet runway provisions on needed runway length will be a

function of the Lndd.v.Ldua.l,airplane 1 s performance characteristics and the

ambient operating conditions. 12 Two major transport category airplane

12 Under proposed 25.109 (c)(2), anti-skid system

demonstrated by flight testing on a smooth wet runway.

operation must be

This requirement I

15
manufacturers provided data comparing dry and wet takeoff performance (not

including credit for grooved or PFC overlay runways) for six airplane

models, 13 These data were used to estimate the average impact of the proposed

wet runway amendments over the existing (amendment 25-42) requirement:

approximately 135 feet.1•

2. Cost mitigating factors

The incremental field-length requirement estimated above omits credit for

runway surface type. Under the new rule, manufacturers will have the option

to use a higher wet runway braking coefficient of friction for grooved runways

or runways treated with a porous friction course material. At the discretion

of the manufacturer, either of two methods may be used to determine the higher

braking coefficient:

1) The applicant can assume that the wet runway braking coefficient is

70% of the dry runway braking coefficient used to determine the dry

runway accelerate-stop distance [amended 14 CFR i25.109(d) (1)], or

2) The applicant can use the wet runway braking coefficient functions

defined in 14 CFR §25.109 (d)(2).

however, can be met during wet runway testing that is already required for

brake and anti-skid system approval under 14 CFR §25.735.

13 In all but one case, dry performance data were based on pre-amendment 25-

42 requirements. These data, then, were adjusted using previously obtained

estimates of the effect of amendment 25-42.

14 No determination was made concerning the representativeness of these

models. The six models represent approximately 4 percent of the current fleet

of transport category airplanes in domestic commercial passe:nger or cargo

service (based on a 1995 inventory of commercial aircraft in domestic service

obtained from the FAA's National Aviation Safety Data Analysis Center,

NASDAC). No 14 CFR part 25 commuter/regional airplane models were included.

16
According to one manufacturer, at 70 percent of the dry runway braking

coefficient, the off-load penalty associated with the subject rule's wet

runway provisions is negligible. This, in conjunction with the reduced screen

height and reverse thrust aspects of these provisions, implies that the

limiting factor for wet runway accelerate-stop distance is likely to be the

dry runway condition.15

15 Guidelines for inspecting and maintaining skid-resistant runway surfaces

are contained in Advisory Circular AC lSO/S320-12B (Measurement, Construction,

and Maintenance of Skid-Resistant Airport Pavement Surfaces), but these are

not mandatory. Therefore, operating cost savings deriving from the grooved

runway credit must be weighed against incremental runway inspection and

maintenance costs. These costs depend on runway usage both in terms of

landing frequencies and airplane type. The minimum friction survey frequency

recommended in AC 150/5320-12B ranges from once per year (if usage is less

than 15 landings per day} to once per week (greater than 210 landings per

day) . Suggested rubber removal frequency ranges from once every two years

(less than 15 landings per day) to once every two months (greater than 210

landings per day). Recommended inspection and rubber removal intervals are

adjusted if widebody transports constitute more than 20 percent of landings.

A private firm specializing in runway inspection and cleaning quotes a price

of $2,975 for friction testing for the first runway and $500 for each

additional runway. According to the same firm, the cost of removing rubber

from a runway ranges from $0.04 to $0.05 per square foot. Several factors

mitigate these incremental costs. First, owing to scale economies, costs also

vary with the size of an airport or its ability to share resources with other

airports. Second, it is often easier to remove rubber from a grooved surface

relative to a smooth surface. Third, airports, as part of the certification

process, already have inspection and maintenance programs in place--although

often not at the frequencies recommended in AC 150/5320-12B.

17
Table 3a.--Airports with grooved or PFC treated runways available

(Source: FAA, Office of Airport Planning and Programming)

Airports

with

Airport Classification Number of groovedjPFC Number of

Airports runways Enplanements

available

Commercial Service (Primary) 423 346 (81.8t) 512,492,974

Commercial Service (Non-Primary) 128 47 (36.7\) 602,541

General Aviation 1,270 292 (23.0t) 955,550

Total 1,821 685 (37.6t) 514,051,065

Table 3b.--Primary airports with grooved or PFC treated runways available

(Source: FAA, Office of Airport Planning and Programming)

Airports with

grooved or

Hub Type Number of PFC treated Number of

Airports· runways Enplanements

available

Large 28 28 (100.0t) 337,662,295

Medium 37 37 (100.0%) 108,170,558

Small 84 82 ( 97 .6%) 48,844,467

Nonhub (Primary) 274 199 ( 72.6%) 17,815,654

Total 423 346 ( 81.8%) 512,492,974

Tables 3a and b reveal that a large fraction of primary commercial service

airports (which account for over 99 percent of total commercial enplanements)

have grooved or PFC treated runways available. The degree to which operators

will be able to take advantage of the grooved runway credit, however, depends

on the extent to which such runways are maintained.

18
E. Net costs

1. Incremental certification costs

Table 4.--Increase in airplane price required to recover additional

certification costiS

(1) (2) (3) (4) (5)

Discount Rate Incremental Discounted

Year (7.00\) Production Cost Cost

0 1.0000 $ 0 $ 0

1 0.9346 $ 0 $ 0

2 0.8734 $ 0 $ 0

3 0.8163 $ 0 $ 0

4 0.7629 SO $ 78,489 $ 59,879

5 0.7130 SO $ 78,489 $ 55,961

6 0.6663 SO $ 78,489 $ 52,300

7 0.6227 SO $ 78,489 $ 48,879

8 0.5820 SO $ 78,489 $ 45,681

9 0.5083 SO $ 78,489 $ 42,693

10 0.4751 50 s 78,489 $ 39,900

11 0.4440 SO $ 78,489 $ 37,289

12 0.4150 50 $ 78,489 $ 34,850

13 0.3878 50 $ 78,489 s 32,570

14 0.3624 $ 0 $ 0

Totals 500 $784,885 $450,000

Incremental airplane unit cost: $1,569.78

Incremental certification costs arise from the need to conduct additional

dynamometer tests. According to estimates provided through AlA, such testing

could raise costs by as much as $450,000. Assuming that the aircraft price

fully reflects this additional cost, and that airplanes are paid for in the

'16 Table notes: Column (1}--year of manufacture. By assumption, incremental

certification costs are incurred in year "0", and production commences in year

"4". Column (2)--the discount factor (7\ discount rate). Colu.on (3)--annual.

aircraft production. Column (4)--annual additional revenue generated from

airplane sales. That is, annual production multiplied the required price

change: [50 x $1,569.78]. Column (5)--discounted annual incremental revenue.

19
year they are built; this would add $1,570 to the airplane unit price (or

approximately $785,00~ to the cost of the 500 airplane fleet). (See table 4.)

2. Net operating costs

The analysis of net operating costs is divided into two cases: one which

assumes that ~here is no decline in brake performance with wear, and another

which assumes a decline in brake performance with wear (see footnote 11) .

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

departures would be conducted using the wet runway accelerate-stop distance.17

Under the production run and cost function 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 ($59,400 per airplane over its service life).

17 In a sample of 83. major U.S. cities, it was found that, on average,

measurable precipitation fell on 114.5 days per year (31.3 percent). It is

estimated that wet runway conditions exist, on average, 20 percent of the time

on days having measurable precipitation. Thus, about 6 pe~cent (20 percent of

31 percent) of all takeoffs actually occur on wet runways. However, this

analysis conservatively assumes that costs associated with the wet runway

requirements will apply on any day having measurable precipitation, while the

benefits will only apply to actual wet runway takeoffs. This follows since it

assumed that operators would not risk using dry runway calculations under the

threat of precipitation.

20
Operating costs, then, will be reduced by approximately $28.9 million for the

500 airplane fleet over its 34 year service life.

In the case where brake pe'rformance is assumed to decline wi th 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 would add approximately $2,700 (in

nominal terms) per year per airplane to operating costs. Therefore, lifetime

incremental operating costs for the 500 airplane fleet are approximately $34.1

million.18 It should be re-emphasized, however, that FAA anticipates that

future airplane models will incorporate brake designs that exhibit little

reduction in braking force with wear. Total net costs--including incrementol

certification costs and net operating effects--for each case are shown in

table 5.

Table 5.--Total net costs

(in $1 units unless otherwise noted)

(Theae are total net coata incluaive of certification coata.)

"Steel" brakes "Carbon" brakes

Airplane Airplane Fleet Airplane Airplane Fleet

(year) (life) (millions) (year) (life) (millions)

Nominal $2,800 $69,800 $34.9 -$2,300 -$57,800 -$28.9

Discounted $ 800 $19,100 $ 9.6 -$ 600 -$15,000 -$ 7.5

18 Again, this reflects revenue lost due to passenger/cargo offload adjusted

for fuel consumption savings.

21
IV. Safety Aspects of the Rule

The rule has significant safety implications owing to the fact that it creates

incenti ves 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.

A. Safety benefits of the worn-brake provisions

The rule I 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, but include an additional safety margin (since most

airplanes will not be operating with fully worn brakes). In addition, the

requirement provides an incentive to use brake technologies that do not

exhibit this wear-related loss of capacity.

B. Safety benefits of the wet runway provisions

As noted earlier, existing regulations do not distinguish between dry and wet

runway surface conditions. The accident history, however, sho•••• s that wet

runway accidents account for a disproportionate share of the tvtal. Between

1965 and 1990, large certificated air carriers accumulated 135.2 million

22
(scheduled and non-scheduled) domestic departures. Assuming that 94% of these

were dry runway takeoffs, there were approximately 127.1 million dry and 8.1

million wet runway takeoffs (see footnote 17). In the same period, however,

u.S. wet runway overrun accidents (that resulted in substantial aircraft

damage or hull loss) accounted for 31 percent of total U.S. accidents (36

percent of the cases where runway condition was reported) .19 These statistics

imply that the wet runway rejected takeoff accident rate is seven times

greater than the dry runway accident rate (0.493 accidents per million wet

runway takeoffs versus 0.071 accidents per million dry runway takeoffs) .

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 mor~

stringent maintenance programs for skid-resistant runway surfaces.

19 In a study of 9S rejected takeoff overrun accidents, FAA determined that

accidents involving wet runways accounted for 40 percent of the total number

of accidents (where the runway condition was reported) .

23
Table 6.--U.8. Overrun accidents culminating in

Substantial damage/Hull 10ss20

Date Type Runway Fatal Serious Minor/no AC Accident

Condo Injury injury damage Cost

06-Nov-67 B707 Dry 1 0 35 Destr $ 14,564,260

26-Dec-68 8707 Unk 3 0 0 Destr $ 19,929,260

29-Jul-69 B727 Unk 0 0 3 Subst $ 1,930,361

27-Nov-70 DC8 Icy 47 49 133 Destr $163,362,260

13-Aug-72 B707 Dry 0 a 186 Subst $ 2,113,361

13-Sep-72 8707 Dry 0 0 3 Destr $ 11,832,260

25-Aug-75 DC10 Dry 0 3 227 Subst $ 3,654,361

12-Nov-75 DC10 Wet 0 0 129 Destr $ 11,958,260

16-Nov-76 DC9 Dry 0 2 84 Destr $ 12,913,260

01-Mar-78 DC10 Wet 2 31 167 Destr $ 32,896,260

17-Aug-81 8727 Wet 0 0 64 Subst $ 1,991,361

27-Jun-85 DC10 Dry 0 1 269 Subst $ 2,696,361

21-May-88 DC10 Dry 0 2 252 Destr $ 13,081,'260

Departures Accident Rate Avg Accident Value

Overall 135,199,134 0.096 per mil dep $ 22,532,530

Wet Runway 8,111,948 0.493 per mil dep $ 52,552,035

Dry Runway 127,087,186 o . 071 per mil dep $ 9,190,527

v. 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 lIa significant economic impact on a substantial number of small

entities. II 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

JO Accident costs are estimated using the following values: 1) fatality,.

$2.7 million; 2) serious injury, $500,000; 3) minor/no injury, $1,000; 4)

destroyed aircraft, $11,381,493; 5) substantial aircraft damage, $1,479,594;

6) minor aircraft damage, 100,000; 7) accident investigation costs, $447,767.

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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, tqe

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 7t 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.

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VI. Trad. Impact A•••••m.nt

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 affect of lessening the

restraints of any trade-sensitive activity. 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 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 certificated under Amendment 25-42 to

become slightly more competitive against current production U.S. airplanes

that were not certificated under Amendment 25-42 by marginally expanding their

takeoff envelope.

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