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Improved Standards forDetermining Rejected Takeoff and

Landing Performance

Federal Register

Department ofTransportation Office ofAviation Policy and Plans

RIN: 2120-AB17 63Federal Register 8298 February 18, 1998

This analysis was issuedbythe agency andcollected bytheAEI-Brookings JointCenter inorder to promote regulatory transparency. The views expressed in this document are those of the agency and donotnecessarily reflectthose oftheJointCenter.

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# - Wednesday February 18, 1998



# Part IV 

# Department of Transportation

FederalAviation 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

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

DEPARTMENT OFTRANSPORTATION

Federal Aviation Administration

14CFR Parts 1,25, 91,121, and 135 [Docket No. 25471; Amendment Nos. 1-48, 25-92,91-256, 121-268, 135-71]
RIN2120-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 fortransport category airplanes to: revise the method fortaking into account the time needed forthe pilot to accomplish the procedures forarejected 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 ofthe standards on the competitiveness ofnew versus derivative airplanes without adversely affecting safety, and harmonize with revised standards ofthe 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 orairplanes 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 ofthis document may be downloaded using amodem and suitable communications software from the FAA regulations section ofthe 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 orthe Federal Register's webpage at http:// www.access.gpo.gov/su_docs for

access torecently published rulemaking documents. Any person may obtain acopy ofthis final rule by submitting arequest to the Federal Aviation Administration, Office ofRulemaking, ARM-1, 800 Independence Avenue, SW., Washington, DC20591, orby calling (202) 267-9680. Communications must identify the amendment number or document number ofthis final rule. Persons interested in being placed on the mailing list forfuture notices of proposed rulemaking and final rulemaking and final rules should request from the above office ofcopy 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 toreport inquiries from small entities concerning information on, and advice about, compliance with statutes and regulations within the FAA's jurisdiction, including interpretation and application ofthe law to specific sets offacts supplied by asmall entity. The FAA's definitions ofsmall entities may be accessed through the FAA's web page (http:// www.faa.gov.avr/arm/sbrefa.htm).by contacting alocal FAA official, orby contacting the FAA's Small Entity Contact listed below. Ifyou are asmall entity and have a question, contact your local FAA official. Ifyou do not know how to contact your local FAA official, you may contact Charlene Brown, Program Analyst Staff, Office ofRulemaking, ARM-27, Federal Aviation Administration, 800 Independence Avenue, SW, Washington, DC20591,1- 888-551-1594. Internet users can find additional information on SBREFAin the "Quick Jump" section ofthe FAA's web page athttpi//www.faa.gov and may send electronic inquiries to the following internet address: 9-AWASBREFA@faa.dot.gov. Background
These amendments are based on notice ofproposed rulemaking (NPRM) 93-8, which was published in the Federal Register onJuly 8, 1993 (58FR 36738). In that notice, the FAA proposed amendments to 14CFRparts 1,25, 91, 121, and 135to improve the standards fordetermining the accelerate-stop and landing distances fortransport category airplanes. The FAA received over 100comments from 22 different commenters on the proposals contained in NPRM 93-8. As

aresult ofthese comments, the FAA has modified some ofthe original proposals. As explained in NPRM 93-8, the operator ofaturbine-powered category airplane must determine that the runway being used, plus any available stopway orclearway, is long enough to either safely continue orreject the takeoff from adefined go/no-go point. The go/no-go point occurs while the airplane is accelerating down the runway fortakeoff when the airplane reaches aspeed known as VI. The assure that the takeoff can be safely continued from the go/no-go point, the length ofthe runway plus any clearway must belong enough for the airplane toreach aheight of35 feet by the end ofthat distance, even ifatotal loss ofpower 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 tobe accelerated to the VI speed and then brought to acomplete stop. This distance is known as the accelerate-stop distance. The choice ofV I speed affects the accelerate-go and accelerate-stop distances. Alower 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 VIspeed decreases the accelerate-go distance and increases the accelerate-stop distance. When V1is selected such that the accelerate-stop distance isequal 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 fortakeoff. The V1speed 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 Bofthe Federal Aviation Regulations (FAR), part 25- "Airworthiness Standards: Transport Category Airplanes," using data gathered during comprehensive flight tests completed as apart ofthe FAA's approval ofthe airplane's type design. Part 25, subpart B,also prescribes the FAA airworthiness standards for determining the length ofrunway required forsafe landing under various airplane and atmospheric conditions. Landing performance charts must be published in the AFM, and are used by

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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 touse 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 ofparts 25,91, 121, and 135concerning the methods fordetermining and applying the takeoff and landing performance standards forturbine-powered transport category airplanes. Also, the FAA proposed to amend part 1,which contains terms and abbreviations used in the FAR, to add adefinition ofthe term "takeoff decision speed" and an explanation forthe abbreviation "VEF." The proposed amendments retained the fundamental principle that the pilot should be able to either safety complete

atakeoff orbring the airplane to a complete stop, even ifpower is lost from the most critical engine just before the airplane reaches adefined go/no-go point. This principle has formed the basis ofthe takeoff performance standards required forthe type certification ofturbine-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 amore rational method totake into account the various operational aspects affecting the takeoff distance. Bythe 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. Ifthe takeoff performance standards

are made more restrictive, longer distances are needed fortakeoff. However, the operator cannot change the length ofthe runway (although a longer runway, ifavailable, could be used). Instead, the operator must usually reduce the airplane's takeoff weight in order to shorten the distance needed fortakeoff. The more restrictive the takeoff performance standards are, the more takeoff weight may have tobe reduced tobe able to operate from a particular runway. To reduce the airplane's takeoff weight, the operator must either reduce the amount offuel tobe carried, or reduce the number ofpassengers or amount ofcargo tobe transported. Since the amount offuel tobecarried is dictated primarily bythe route being flown, the operator's only option may be to reduce the number ofpassengers or amount ofcargo to betransported. When the number ofpassengers or amount ofcargo must bereduced for a given flight, the airplane operator can suffer aloss ofrevenue. 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 forin the AFM accelerate-stop distances by adding one second to the flight test demonstrated time interval between each ofthe 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 ofthese actions results in atotal of two seconds being added tothe time taken bythe flight test pilots to accomplish the procedures for stopping the airplane. In calculating the resulting accelerate-stop distances forthe AFM,

no credit was allowed forany deceleration during this two-second time period. The revised standards ofAmendment 25-42 required the accelerate-stop distance toinclude two seconds of continued acceleration beyond V1speed before the pilot takes any action to stop the airplane. This revision resulted in longer accelerate-stop distances for airplanes whose application foratype certificate was made after Amendment 25-42 became effective. Consequently, turbine-powered transport category airplanes that are currently being manufactured under atype certificate that was applied forprior toMarch 1, 1978, have asignificant operational economic advantage over airplanes whose type certificate was applied for after that date. This competitive disparity resulting from applying different performance standards created

acompelling need to amend the takeoff performance standards ofpart 25 without adversely affecting safety. In addition, operational experience indicated aneed to specifically address the detrimental effects ofworn brakes and wet runways on airplane stopping performance. Amendment 25-42 was abroad brush approach, applying to all takeoffs, to increase the required accelerate-stop distance. This broad brush approach did not explicitly account formany ofthe important operational factors that may affect takeoff performance. For example, the standards did not distinguish between dry and wet runways, nor were the effects ofworn brakes taken into account. Wetrunways and worn brakes typically result in longer accelerate-stop distances than with new brakes on adry runway. Byrequiring wet runway performance tobe determined and included in the AFM, and by requiring the use ofworn brakes to determine the airplane's stopping capability, the proposed amendments would provide additional accelerate-stop distance for the conditions in which itis 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 ofcontinued acceleration beyond VIwith adistance equal totwo seconds atthe VIspeed. The distance equal totwo seconds at constant VI, while shorter than that resulting from the continued acceleration beyond VIrequired by Amendment 25-42, isadistance margin that must be added to the acceleratestop distance demonstrated during flight testing fortype certification. The FAA intends forthis distance margin to take into account the variability in the time ittakes forpilots, in actual operations, to accomplish the procedures for stopping the airplane. Amendment 25-42 required the two seconds oftime delay to be applied prior tothe pilot taking any action to stop the airplane. This more restrictive approach assumes that the airplane reaches ahigher speed during the accelerate-stop maneuver and, therefore, results in alonger 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 bethe speed by which the pilot has already made the decision torejected the takeoff and has begun taking action to stop the airplane. The time ittakes forthe pilot to recognize the need for arejected takeoff, which occurs before VI isreached, 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 ofthe VI speed. In summary, the purpose ofthe amendments tothe takeoff performance standards ofparts 25, 91, 121, and 135,

as proposed in NPRM 93-8, was to more rationally reflect the operational factors involved and reduce the impact ofthe 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 tobe

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determined with brakes that are worn to their overhaul limit. Lastly, the two seconds ofcontinued acceleration beyond VI speed would bereplaced by

adistance equal to two seconds atVI speed. InNPRM 93-8, the FAA also proposed to amend the landing distance standards ofpart 25 toaccount forworn brakes. The FAA proposed this change tobe consistent with the proposal for taking worn brakes into account forthe takeoff accelerate-stop distances. Because airplanes generally require

more distance to take offthan 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 asignificant effect on the number ofpassengers or amount of cargo that can becarried. 

### International Harmonization of Airworthiness Standards
For more than ten years, the FAA has been cooperating with the Joint Aviation Authorities OAA)ofEurope topromote harmonization between the FAR, particularly the airworthiness standards, and the European Joint Aviation Requirements OAR).The aircraft certification authorities of23 European countries are members ofJAA. An annual meeting is held between FAA senior management officials and senior management officials ofthe JAA member authorities to identify technical subject areas where cooperation is needed to promote greater harmonization between the FARofthe United States and the European JAR.A large portion ofthese meetings have been open to the public. A comprehensive study ofthis activity

was completed byProfessor George A. Berrnann, Columbia University School ofLaw, in May 1991 as aconsultant to the Administrative Conference ofthe United States (ACUS). Acopy 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 ofthis effort and has indicated strong support forthis activity in their Recommendation 91-1, titled "Federal Agency Cooperation with Foreign Government Regulators," adopted June 13, 1991. Atthe annual FAA/JAA meeting in June 1989, the FAA and JAAdiscussed the competitive disparity caused bythe 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 atdifferent times, thus allowing the use ofdifferent amendments, both groups ofairplanes

are continuing in production and both

are competing forsales and foruse over
some common routes. Airplanes whose designs were type certificated tothe standards introduced byAmendment 25-42 could bepenalized in terms of the number ofpassengers oramount of cargo they can carry over acommon route, even though the airplane's takeoff performance might bebetter from a safety perspective than acompeting airplane design that was not required to meet the later standards. Currently, most ofthe transport category airplane types that have been required to meet the later standards ofAmendment 25- 42were designed and manufactured outside the U.S. (mostly in Europe). These airplanes are competing forsales against airplanes that were designed and manufactured in the U.S. that were not required tomeet the standards of Amendment 25-42. This situation has led to claims by amajor European manufacturer oftransport category airplanes that this disparity in the airworthiness standards has created an unfair international trade situation affecting the competitiveness oftheir airplane types ofalater design. Atthe June 1990 annual meeting, the FAA and JAAagreed tojointly 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 oftwo parts: First, the current takeoff performance standards

were reviewed to determine ifthey were too restrictive; and second, the merits of making the resulting standards apply retroactively were considered forboth 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 ofpart 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 byNPRM 93-8 retroactive to either airplanes currently in use or future production airplanes ofdesigns that have already been type certificated. Ifadditional information to support making these proposed standards retroactive became available at alater date, the FAA proposed to review such information and determine iffurther rulemaking would be appropriate. InMarch 1992, the JAA issued its Notice ofProposed Amendment (NPA) 25B, D,G-244: "Accelerate-Stop Distances and Related Performance Matters" to amend the takeoff performance standards ofJAR-25. The amendments proposed in NPRM 93-8

were substantively the same as the amendments proposed by the JAA NPA forJAR-25. 

### Discussion oftheProposals
In NPRM 93-8, the FAA proposed the following rule changes: 1.Replace the two seconds of continued acceleration beyond VI (mandated byAmendment 25-42) with

adistance margin equal totwo seconds atVI speed; 2.Require that the runway surface condition (dry orwet) betaken into account when determining the runway length that must be available for takeoff; and 3. Require that the capability ofthe brakes to absorb energy and stop the airplane during landings and rejected takeoffs bebased on brakes that are
worn totheir overhaul limit. 

### Proposal 1
The FAA proposed to amend the method ofdetermining the acceleratestop distance prescribed in §25.109 by replacing the two seconds ofcontinued acceleration after reaching VIwith a distance equal to two seconds atVI speed. This proposal would reduce the accelerate-stop distance that must be available forarejected takeoff because the airplane would be assumed to begin stopping from alower speed (from VI, rather than from the speed reached after two seconds ofacceleration beyond VI). The FAA's intent was toreplace the most costly aspect ofAmendment 25-42 with arequirement that closely represents the pre-Amendment 25-42 criteria of§25.109, as applied to the certification ofrecent U.S.- manufactured airplanes. 

### Proposal 2 The FAA proposed to amend §25.105 to require that airplane takeoff performance data bebased on wet, in

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addition to dry, runways. Section 25.l587(b) would be amended to require that performance information forwet runways beincluded in the Airplane Flight Manual (AFM). Sections 91.605, 121.189, and 135.379 ofthe operating rules would be amended torequire that wet runways betaken into account when determining the runway length that must be available fortakeoff, ifwet runway performance information exists in the AFM. Thus, this rule would apply only to airplane designs forwhich the application fortype certification occurs after the amendment becomes effective, and to those previously certificated airplane designs forwhich the manufacturer chooses tore-certify tothe amended standards. Section 25.109 would be revised to provide the details ofhow the accelerate-stop distance would be calculated for awet runway. The FAA proposed the following approach to determining the wet runway takeoff performance: (1)Take into account the reduced braking force due tothe 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 ofthe runway after takeoff to be reduced from 35 feet to 15feet. This approach would reduce the risk of

overruns during rejected takeoffs on wet runways while retaining safety margins for continued takeoffs similar tothose required fordry runways. The reduced braking force available is the most significant variable affecting the stopping performance on awet runway. The FAA proposed torevise §25.109 to specify that the wet runway braking force would be one-half the dry runway braking force, unless the applicant demonstrated ahigher wet runway braking force. Under this proposal, the one-half ofthe dry braking force level would apply regardless of whether the dry runway braking force is limited bythe torque capability ofthe brake (which is the friction force generated within the brake) orthe friction capability ofthe runway surface. Although itcan be argued that the torque capability ofabrake is independent ofthe runway surface condition, the proposed use ofthis 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 ofBraking Force," shows that the relationship between wet and dry braking coefficient varies Significantly with speed. Athigh speeds, the wet runway braking coefficient istypically 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 forthe stopping portion ofarejected takeoff, however, the wet runway braking coefficient canjustifiably be approximated as one-half the dry braking coefficient. The ESDUreport is included in the docket. Under this proposal, §25.109 would also berevised topermit the use of available reverse thrust when determining the accelerate-stop distance forawet runway. "Available" reverse thrust was interpreted as meaning the thrust from engines with thrust

reversers that are operating during the stopping portion ofthe rejected takeoff. Credit forreverse thrust was included in the proposal because the most significant variable that affects the stopping performance on awet runway, reduced braking friction, was also included aspart ofthe rational approach towet runway rejected takeoff. On dry runways, the FAA proposed to explicitly deny credit forreverse 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 bynot accounting forreverse thrust in calculating the accelerate-stop distance on adry runway is necessary to offset other variables that can significantly affect the dry runway accelerate-stop performance determined under the current standards. Forwet runways, credit forreverse thrust would be permitted because taking into account the reduced braking force available on the wet surface, as proposed inthis notice, greatly outweighs the effects ofthese other variables. Examples ofvariables 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 ofheat retained from previous braking efforts, etc. The FAA proposed to revise §25.113 to allow the distance required for a continued takeoff from awet runway to include taking offand climbing to a height of 15feet, rather than the height of35 feet required on adry runway. This lower screen height (which is the height ofan imaginary screen that the airplane would just clear with the Wings in alevel attitude when taking offor landing) would reduce the balanced field length VI speed, thereby reducing the number ofhigh-speed rejected takeoffs on wet runways. The FAA considers lowering the screen height to 15feet to be an acceptable method of reducing the risk ofoverruns on wet runways because ofthe similarity to current rules when operating from dry runways that have aclearway. The minimum height permitted over the end ofthe runway for current dry runway takeoffs may be 13to 17feet, depending

on the airplane, when aclearway is present. 

### Inaddition, a 15-foot minimum

screen height and vertical obstacle clearance distance has been allowed for many years by the United Kingdom Civil Aviation Authority forwet runway operations without any problems being reported. The combination ofaclearway with the proposed 15-foot screen height for wet runways could result in aminimum height over the end ofthe runway of

near zero (Le.,liftoff very near the end ofthe runway), ifclearway credit were to bepermitted forwet runways in the

same manner that itis currently permitted for dry runways. The FAA considers this situation tobe unacceptable. The possible presence of standing water orother types of precipitation (e.g.,slush or snow) and

numerous operational factors (e.g., late

orslow rotation to liftoff attitude) emphasize the need to provide more of

asafety margin than would be present ifliftoff were permitted so near the end ofthe runway. Therefore. the proposed §25.113 would not permit the combination ofclearway credit and a l5-foot screen height. The FAA proposed to modify §25.113, however, to ensure that the presence ofaclearway does not result in requiring longer runway lengths than ifthere were no clearway. 

### Inaddition tothe reduced screen height forwet 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 torevise §25.115 to state that the takeoff flight path shall be considered tobegin at a height of35 feet atthe end ofthe takeoff distance. This revised definition ofthe takeoff flight path would apply equally to dry and wet runways, even though the height ofthe airplane atthe end ofthe takeoff distance (i.e., the screen height)

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forwet runways is proposed to beonly 15feet. The effect ofthis proposal would be to make itpossible to use the flight path information currently contained in the AFM even ifthe runway iswet. Because the screen height would bereduced from 35feet to 15feet for awet runway, the height of

an airplane at any point in the flight path will therefore be approximately 20 feet lower from awet runway than from

adry runway. Under this proposal, the airplane's actual height over obstacles would bereduced by approximately 20 feet when taking offfrom awet runway. Under the current regulations, the airplane's flight path must be higher than any obstacles by acombination of

an increment ofheight and an increment ofgradient (i.e., the slope of the flight path). Although this proposal would reduce the height increment by approximately 20feet, the gradient increment would be unchanged. Asthe distance from the end ofthe takeoff distance increases, the gradient increment provides an increasingly greater portion ofthe total height difference between the airplane and the obstacle. Therefore, the effect of reducing the height increment over obstacles by 20feet diminishes as the distance from the end ofthe takeoff distance increases. 

### Proposal 3 The FAA proposed to amend §25.101 (f) torequire that accelerate-stop and landing distances must be determined with all the airplane brakes atthe fully worn limit oftheir allowable

wear range. Section 25.735 would be revised to require that the maximum brake energy capacity rating must be determined with each brake atthe fully

worn limit ofthe allowable wear range. In addition §25.735 would be amended to add arequirement foraflight test demonstration ofthe maximum kinetic energy rejected takeoff with not more than 10percent ofthe 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 aresult oftheir special investigation ofrejected takeoff accidents, the National Transportation Safety Board (NTSB)recommended that the FAA clearly define the term "takeoff decision speed" (VI) inpart 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 adefinition oftakeoff decision speed to §1.1 in order to remove apparent confusion over the meaning of this term. The FAA's proposed definition was intended tomake itclear that the decision toreject the takeoff, indicated by the pilot activating the first deceleration device, must be made no later than VJ forthe airplane tobe stopped within the accelerate-stop distance. The abbreviation VEF isused in several places within part 25.The FAA proposed to amend §1.2to add the definition ofVEF, which currently appears in §25.107(a)(I). VEF is the speed atwhich the critical engine is assumed tofail during takeoff. As stated previously, the FAA did not intend to apply these proposed amendments retroactively to either airplanes currently in use orfuture production airplanes ofdesigns that have already been approved. However, manufacturers oroperators ofthese airplanes may elect to comply with these proposed amendments by a change tothe type design. The benefits ofthe revision tothe time delay criteria of§25.109 would then be available to relieve the economic burden imposed by Amendment 25-42. The proposed amendments totake into account the effects ofwet runways and worn brakes must also beincluded in such a recertification. The FAA expects that, forairplanes whose certification basis includes Amendment 25-42, most applicants will elect to comply with this proposal because itwill be economically beneficial forthem to do

so. Discussion ofthe Comments The FAA received over 100comments from 22different 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 ofthe U.S. government. Because ofthe increasing emphasis placed on international harmonization ofthe 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 ofCanada 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 tonew derivatives ofexisting approved designs as well as to completely new airplane designs. Another issue that generated strong contrasting views concerns the distance needed toalign an airplane on the runway fortakeoff. Typically, airplanes enter the takeoff runway from an intersecting taxiway. The airplane must then beturned so that itispointed 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 fortakeoff. The commenters who support retroactivity also support amending the regulations to require operators totake this runway alignment distance into account. Those who oppose retroactivity also oppose proposals torequire taking into account the runway alignment distance. InNPRM 93-8, the FAA stated that "with the safety benefits and economic impact information available atthis time, the FAA cannot support a recommendation to make the standards proposed bythis notice retroactive to either airplanes currently in use or future production airplanes ofdesigns that have already been type certificated." This conclusion was reached after areview ofthe 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. Itshould be noted, however, that one part ofthe proposed standards has effectively already been imposed retroactively. The FAA has issued airworthiness directives (AD's) concerning brake wear limits forevery FAA-certificated transport category airplane with amaximum takeoff weight ofover 75,000 pounds. These AD's

ensure that the brakes on these airplanes, even when fully worn, can absorb the energy from amaximum energy rejected takeoff. Inaddition to the economic impact of retroactively applying the proposed standards, the FAA was influenced by the increasing emphasis on international harmonization ofthe airworthiness standards. Retroactivity of the proposed standards and the requirement totake runway alignment distance into account, had the FAA decided toproceed with these provtsions. would have been

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accomplished through revisions to the operating rules ofthe FAR. Atthe time NPRM 93-8 was being developed, the jAA lacked operating rules with which to impose these requirements. Although the introduction andjustification sections ofjAA NPA 25B, D,G-244 discussed an intent to apply the standards retroactively, and to require that runway alignment distance be taken into account, thejAA 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, thejAA published NPA OPS-2, containing proposed JAR operating rules for commercial air transportation OAR-OPS 1).

### Inthis NPA, thejAA proposed to retroactively require operators to take into account the performance effects ofwet 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 ofthe proposed requirements related to worn brakes. The jAR-OPS 1final 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 ofairplanes with amaximum takeoff weight ofover 10,000 pounds or
amaximum approved seating capacity of20 or more passengers. Due to the controversial nature ofthe issues ofretroactivity and runway alignment distance, the FAA has decided to: (1)Proceed with the proposed rules without requiring retroactive application ofthese standards or adding anew requirement concerning runway alignment distance, and (2)recommend that the issues of retroactive application ofthese standards and runway alignment distance be added to the FAA/jAA harmonization work program. Except in the treatment ofthese 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 tojAR-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 ofthe 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 awide range of interest within the aviation community. Meetings ofthe committee are open to the public, except as authorized by section 10(d) ofthe 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

aworking group proposal before that proposal can be presented tothe FAA as
an advisory committee recommendation. After an ARAC recommendation isreceived and found acceptable bythe FAA, the agency proceeds with the normal public rulemaking procedures. Most ofthe 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 ofcontinued acceleration beyond V1with adistance margin equal to two seconds atVI speed (Proposal 1),because itwould allow an increase in the maximum allowable takeoff weight when that weight is limited by the length ofthe runway. Although the FAA agrees with the commenters on the effect ofthis 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 ofthe FAA proposals was to present amore 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 orhigher level ofsafety 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 agiven runway length could end up being either increased or decreased under the proposed standards. Although its effects are variable, the FAA estimates that Proposal 1would reduce, on average, the runway length needed for takeoff by 150feet. For airplanes equipped with typical steel brakes, the proposed worn brake requirements would add an average of 150feet to the runway length needed fortakeoff. The FAA estimates that the proposed wet runway requirements would result in an average increase of220 feet in the runway length required fortakeoff when the runway is wet. Itshould 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 ofwhether this improvement

comes from taking into account aloss in brake capability, orbecause 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 ofthe team relative to training and procedural actions that could be taken to increase takeoff safety. The goal ofthe training aid isto minimize the probability of rejected takeoff accidents and incidents by: (1)Improving the ability ofpilots to take advantage ofopportunities to maximize takeoff performance margins; (2)improving the ability ofpilots to make appropriate go/no-go decisions; and (3)improving the ability ofcrews to effectively accomplish the rejected takeoff procedures. Simulation trials and in-depth analyses oftakeoff accidents and incidents were used to develop the training aid material. The FAA urges operators to use the Takeoff

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Safety Training Aid in their qualification and recurrent aircrew training programs. The FAA is convinced that adoption ofthis material will further improve safety during the critical takeoff phase offlight. The FAA received alarge number of comments on the proposed definition of takeoff decision speed (VI)'including its relationship tothe broader subject ofthe process bywhich the pilot recognizes a failure, decides toreject the takeoff, and acts on that decision. One commenter submitted several documents as additional supporting material. including adetailed study ofpilot reaction times during rejected takeoff accidents. This commenter, accompanied by several others, believes that the proposed standards inadequately provide forthe time it takes the average pilot to complete the recognition, decision, and reaction process. Other commenters support the FAA proposal. and some ofthese commenters also offered suggestions to further clarify the purpose ofthe VI speed. The diversity displayed in the comments illustrates agreat deal of misunderstanding and disagreement regarding the definition and use ofthe VIspeed. Ingeneral. inconsistent terminology used over the years in reference toVIhas probably contributed tothis confusion. As noted bythe 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 toVI 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 orhow the time delays should be introduced relative to VI. For certification purposes, the FAA considered VI to be the speed atwhich the pilot took the first action to stop the airplane. Time delays forrecognition and reaction tothat failure were applied prior toVI,and delays in accomplishing each subsequent action forstopping the airplane were applied after VI. Allowing forthe time delays, the actual engine failure was therefore assumed to occur prior toVI. With Amendment 25-42, effective March 1. 1978, the FAA amended the airworthiness standards to clarify and standardize the method ofapplying these time delays. VIwas referred to as the "takeoff decision speed." which turned out tobe ambiguous in that it could beinterpreted to mean either the beginning orthe end ofthe pilafs decision process. The preamble to Amendment 25-42, however, states that "VI isdetermined by adding toVEF [the speed atwhich the critical engine is assumed tofail] the speed gained with the critical engine inoperative during the time interval between the instant at which the critical engine isfailed and the instant atwhich the test pilot recognizes and reacts tothe engine failure, as indicated bythe pilafs application ofthe first retarding means during accelerate-stop tests." This same definition was codified as §25.107(a)(2). Not only isVIintended to occur atthe end ofthe decision process, but italso includes the time ittakes forthe pilot to perform the first action to stop the airplane. The FAA requires applicants to demonstrate, byflight test, the time intervals between VEF and VI, and between each subsequent action taken bythe pilot to stop the airplane. FAA pilots and engineers witness and participate in these tests, which must include atleast six rejected takeoffs. Because the test pilots know that they

are going to reject the takeoff, human factors literature refers tothis process as
asimple task. Inactual operations, the rejected takeoff maneuver is unexpected, and isreferred to as a complex task. In consideration ofthis 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 adecision to stop after passing through VI.Their purpose is to allow sufficient time (and distance) for apilot. in actual operations, to accomplish the procedures forstopping the airplane. The first adjustment is made tothe time interval between VEFand 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 bethe longer ofeither the demonstrated time orone second. This standard has been applied tothe certification ofevery 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 ofdetermining this adjustment has varied, but the objective has always been the same-to provrde enough time and distance for apilot 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 orpower, 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 toperform. 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 tothe time intervals determined bythe certification flight tests. Amendment 25-42 changed the method ofapplying these time increments. The provisions added by Amendment 25-42 require the AFM accelerate-stop distance to be calculated by inserting atwo-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. Nofurther time increments

are added tothe time intervals between the actions taken by the pilot to stop the airplane. Itisimportant tonote 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 bydirecting the pilot to delay action for two seconds after VIduring the rejected takeoff flight tests. The proposal presented in NPRM 93- 8would change the method ofapplying this two second time increment to a method similar to that existing prior to Amendment 25-42. However, the proposed method uses adistance increment rather than atime 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 isequal tothe distance traversed in two seconds atthe VI speed. Unlike the pre-Amendment 25- 42method. this distance increment cannot bereduced when fewer than three pilot actions are used in the rejected takeoff procedures (e.g., for airplanes using automated systems that take the place ofone ormore ofthe usual pilot actions). The FAA considers the distance traveled in two seconds at VI speed tobe the minimum acceptable

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distance allowance needed to provide forthe element ofsurprise 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

arejected 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, aone-second time (and distance) increment must be added tothe demonstrated time interval for that action. The FAA disagrees with those commenters who believe that the proposed standards inadequately provide forthe time ittakes the average pilot to complete the recognition, decision, and reaction process. Not only does the FAA require applicants to determine byflight test the length of time needed forthe pilot to complete this process, but this demonstrated time interval is also increased totake into account the element ofsurprise 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 V1as the airplane accelerates through this speed. Ifthe 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 isunsafe to fly. One commenter states that airplane manufacturers produce performance data foruse bythe U.S. military that provides the engine failure speed, rather than the speed atwhich the pilot must respond tothe 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 amilitary background operate under the belief that the civil airworthiness standards provide equivalent safety tothe military standards. Inthe cornmenter's opinion, the civil standards provide alower level ofsafety, and these pilots have been given afalse sense ofsecurity. The FAA is aware ofmany differences between the civil and military takeoff requirements. These differences are indicative ofthe different operating needs and environments between civil and military flight operations. For example, the military standards allow liftoff to occur atthe very end ofthe runway and obstacles tobecleared with

no safety margin in the event ofthe failure ofthe critical engine atthe designated "go" speed. In contrast, part 25requires the airplane tobe ataheight of35 feet atthe end ofthe takeoff distance (onadry runway), and obstacles must becleared by 35 feet plus

an additional safety margin related to the flight path gradient. In summary, the civil and military airworthiness standards provide forsafe operations within their respective operating environments. Itwould be inappropriate, however, to apply unique procedures and techniques from one operating environment to the other. One commenter noted that the proposed definition fortakeoff decision speed tends to perpetuate the confusion

over the meaning and use ofthe VI speed. The commenter points out that V1is really a "pilot action speed" that

occurs immediately after the pilot makes the decision toreject the takeoff. Another commenter suggests that the proposed definition is technically inaccurate because reducing thrust during arejected takeoff would not normally beconstrued as activating a deceleration device. Hence, the commenter suggested alternative wording forthe 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 achange tothe definition of V1 in §1.2,rather than an addition to §1.1.This revised definition clarifies that V1represents 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 ofthe proposals has been edited foradditional clarity topresent aconsistent description ofthe VI concept. The proposed addition ofthe definition forVEFto §1.2isadopted as proposed. One commenter misunderstood this proposal as representing the first time the FAA has sought to define VEF•For clarification, the term VEFand its definition were originally added to §25.107(a)(l) by Amendment 25-42. The amendment adopted in this rule adds the existing definition forVEFto 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 ofrated takeoff thrust to allow its use forup to ten minutes of operation. The current definition in § 1.1 limits the use oftakeoff thrust to five minutes orless. The FAA is currently considering the change proposed bythis commenter as part of

aharmonization effort with the European JAA. In the interim, the FAA has developed aprocedure to review and approve specific requests forthe

use oftakeoff thrust forup to ten minutes duration on transport category airplanes in the event ofan engine failure orshutdown. One commenter recommended adding "wet and dry runway conditions" tothe variables listed in §25.101 (e)forwhich the airplane configuration may vary. The rationale the commenter provides forthis recommendation is to encourage optimization ofthe 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 §25.105(a)(2)to require the takeoff data tobe determined in the optimum configuration forthe takeoff conditions specified in §25.105(c). The commenter believes that this change would require operators touse the optimum flap setting for takeoff. rather than allow the use ofany flap setting that meets the applicable regulations. The FAA does not concur with this recommendations forthe following

reasons. First, the cornmenter's recommendation should bedirected at the airplane operating requirements, rather than the part 25 airworthiness standards. The effect ofthe recommended revision to part 25 would be toprohibit takeoff data from being provided forconfigurations that were not deemed to bethe 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

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distances. However, this configuration also typically results in the poorest climb capability after takeoff, and may not bethe optimum configuration from the standpoint ofobstacle clearance, noise, standardization ofcrew procedures, orfuel use. The FAA received several comments regarding the proposed change to §25.101 (r).One commenter recommends deletion ofthe 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 toreduce the amount ofpayload that can be carried. The commenter also notes that there has

never been alanding incident or accident in which adeficiency in brake energy due to wear was afactor, 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 ofpayload that can be carried formost landings, the FAA disagrees that the effects ofworn brakes

on landing will always be insignificant. The effect ofbrake wear atthe braking energy levels associated with alanding stop depends on the particular brake design. To provide forthose 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 ofthe brakes for determining the landing distances. No additional AFM information, and, therefore, no additional flight manual development costs would berequired. The proposed requirement also would not necessarily result in additional certification testing. The only flight test that must be performed with worn brakes isthe maximum energy rejected takeoff condition, in which the brakes must beworn to within 10percent of the fully worn condition. All other data must only meet the condition that sufficient data be available from airplane flight tests orwheel-brake dynamometer tests to enable adjustment ofall ofthe takeoff and landing flight test results to the fully worn level. For example, the testing performed to determine the effect ofworn brakes on accelerate-stop distances may also be used to determine the effect ofworn brakes on landing distances, ifitcan be shown tobe applicable. Another commenter suggests adding the stipulation that the determination of the accelerate-stop and landing distances must bebased on the demonstrated results obtained byflight test in accordance with the proposed §25.735(g). The FAA concurs with the intent ofthis suggestion. Instead of modifying the proposed §25.101 (i), however, the FAA is revising the proposed §25.735(g) and relocating itas
anew §25.109(i). The adopted wording clarifies that the applicant must conduct

aflight test demonstration ofthe maximum brake kinetic energy accelerate-stop distance with no more than 10percent ofthe allowable wear range remaining on each ofthe airplane wheel brakes. This change tothe original proposal is also discussed later relative tothe comments received on the proposed §25.735(g). Acommenter proposes awording 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 asproducing the least effective braking performance. The FAA agrees that the most critical wear condition should beused to determine the stopping distances and energy capacity ofthe brakes. In practice, however, the FAA believes this condition will always bethe fully worn brake. The FAA does not believe that an extensive dynamometer survey ofdifferent wear states iswarranted. One commenter suggests that stopping distances be based onbrakes that are worn to 90percent ofthe allowable wear level instead ofthe proposed level offully worn. This commenter states that, in actual operations, itwould bevirtually impossible for all the airplane's brake assemblies to simultaneously be atthe fully worn limit oftheir allowable wear range. In addition, this commenter believes that such conservatism in determining the stopping distances tobe unwarranted when combined with the

worn brake requirements relating to brake energy absorption capability. As

an alternative, this commenter, joined by asecond commenter, proposes that §25.101 (i)optionally allow stopping performance tobe based on the actual amount ofbrake wear existing atthe time ofeach flight. The two commenters state that itis unnecessary and inappropriate forthe 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 ofthe brakes. The FAA does not concur with the recommendation tobase the stopping distances on brakes worn to 90 percent ofthe 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 ofwear, airplanes may legally be operated with all ofthe brake assemblies in their fully worn condition. The FAA agrees that itwould be inappropriate forthe 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 tobe based

on the actual brake wear level, the FAA has significant concerns over the operational aspects. Although itmay be possible to determine the acceleratestop and landing distances as afunction ofbrake wear, the FAA considers it unacceptable to use, on aflight-by-flight basis, the brake wear level as an additional takeoff performance variable. The added complexity caused bythis additional variable would increase the chances oferror 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 ofthe brake under all operational and environmental conditions. Finally, extensive certification testing would be required to determine the stopping distances as afunction ofthe brake wear level. Alinear relationship between these variables cannot be assumed. Therefore, §25.101 (i) is adopted as proposed, except for aminor editorial revision forclarification purposes. Since the certified accelerate-stop and landing distances will correspond to brakes that are atthe fully worn limit of their allowable wear range, the allowable brake wear range must be specified aspart ofthe approved type design forthe airplane. This information should be provided on the type certificate data sheet. The allowable

wear range should bedefined in terms ofalinear dimension in the axial direction, which is typically determined by measuring the extension ofapin used to indicate the amount ofwear. At the fully worn limit ofthe 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

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amend §25.109 to replace two seconds ofacceleration beyond V1 speed with the distance traversed in two seconds at V I 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. asrequired by the proposed §25.109(a). would become almost meaningless. This commenter claims that "test pilot response in the order ofmilliseconds preempts any significant difference in acceleration distance between engine out and all engine acceleration before VI." Also, the proposed distance traversed during two seconds atVI speed isthe same forboth

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 ofacceleration with adistance equal totwo seconds at VI speed. would provide more rational takeoff airworthiness standards and an equivalent orhigher level ofsafety than the current standards. Regarding the comparison ofone-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 isthe 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 beused in determining the dry runway acceleratestop distances. the operating engines (on

aturbojet powered airplane) will continue to produce forward thrust. Therefore (forturbojet airplanes). the distance to stop from VI will usually be longer for all-engines-operating case than forthe one-engine-inoperative

case. Whether the sum ofthe accelerate and stop distances is greater forthe allengines-operating case as opposed tothe one-engine-inoperative case depends on the time intervals between VEF and VI. VI and the pilot action toreduce thrust, and on the engine transient response (spindown) characteristics. For wet runways, in which the effect ofreverse thrust would be included, the stopping distance with one-engine-inoperative will usually be longer than that with allengines-operating. Ingeneral, the FAA expects the dry runway accelerate-stop distances tobe based on the all-enginesoperating case. and the wet runway accelerate-stop distances tobebased on the one-engine-inoperative case. One commenter suggests that the FAA should provide astatement proclaiming that the standards proposed in NPRM 93-8 "reflect the full intent ofthe 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 asituation will not recur. The FAA intends torevise Advisory Circular (AC)25-7. "Flight Test Guide forCertification ofTransport Category Airplanes." tobe consistent with this adopted rule and the description ofthe time delays provided in this preamble discussion regarding the definition ofVI. 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 atV]. 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 FAAreceived alarge number of comments regarding the proposed method fordetermining takeoff performance on wet runways. One of the provisions ofthe proposed method would allow applicants touse a simplified approach to determine the braking capability on awet runway without the need forspecific wet runway flight testing. Based on the extensive wet runway testing conducted

over the past 30years bythe National Aeronautics and Space Administration (NASA). the FAA, the aerospace industry. and other organizations around the world (acompilation of which appears in the docket in ESDU item number 71026). the FAA proposed using abraking coefficient ofone-half the demonstrated dry braking coefficient. The FAA intended forthis one-half factor tobe applied even ifthe dry runway braking coefficient is limited bythe maximum torque capability ofthe brake, rather than the maximum friction capability available from the runway surface. Several commenters disagree with using asimple 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 toprovide awet 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 ofwhat the commenter feels should bedone 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 ofapplying the one-half factor when the dry runway braking coefficient corresponds to the maximum torque capability ofthe brake. In spite ofthe explanation provided in the preamble discussion in NPRM 93-8. these commenters oppose this provision

on the basis that the maximum torque capability ofthe brake is independent of the runway surface condition. One commenter conducted laboratory tests ofasimulated wet runway to show that the stopping ability ofan airplane on a wet runway is not afunction ofthe size

ortorque limit ofthe brakes. Another commenter claims that this provision appears toprohibit the effective and safe

use ofbraking capacity up to the limit ofthe wet runway braking coefficient. This commenter points out that an airplane with brakes that have alow maximum torque capability would be unfairly penalized relative to an airplane equipped with brakes ofa higher maximum torque capability. Another commenter questions whether the proposed requirement is a conservative approach resulting from a lack ofappropriate test data. The FAA agrees that the torque capability ofthe brake is usually not a limiting factor on asmooth wet runway. The FAA proposed applying afactor to the torque limited braking coefficient to represent the varying relationship between the wet and dry runway braking coefficients as afunction of ground speed. Athigher ground speeds, the wet runway braking coefficient is typically less than one-half the dry runway braking coefficient. Atthese higher speeds. the dry runway braking coefficient isusually limited by the brake's maximum torque capability. For the typical airplane/brake combination. factoring the torque limited braking coefficient obtained on adry runway by one-half provides areasonable approx imation tothe significantly

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reduced braking coefficients observed at high speeds on wet runways. Because the total stopping distance forahigh speed stop is affected more bythe stopping capability athigh speeds than atlow speeds, applying the one-half factor only tothe non-torque limited braking coefficient would be inadequate for determining the total distance needed to stop on awet runway. The FAA does not concur with the comment that this proposal would prohibit the safe and effective use of braking capability on awet runway. This proposal only addressed the method fordetermining the wet runway accelerate-stop distances presented in the AFM. Itwould 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 bythis provision. In recognition ofthis potential disparity, the proposed §25.109(b)(2)would have allowed applicants the option of demonstrating ahigher 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 achange tothe FAA proposal to allow the use ofmethods other than flight testing to demonstrate

ahigher wet runway braking coefficient. This commenter believes that in the

near future itmay become feasible to
use data obtained from either an analysis, asimulation ofthe airplane's braking system, or other sources. One ofthe commenters who opposed portions ofthe 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 toreplace the option for demonstrating abraking coefficient higher than one-half the dry runway braking coefficient. The following summary represents abrief synopsis of the cornrnenter's detailed proposal:

a. Derive astandard 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 beused for all transport category airplanes as the basis for developing airplane type specific

curves. b. Apply adjustments to this curve to reflect the capability ofan individual airplane type's anti-skid system on a wet runway. The anti-skid system capability would bedetermined either directly from wet runway testing, ora conservative capability (Le.,somewhat

worse than would beexpected iftesting

were performed) would be assumed, based on the capability ofexisting comparable anti-skid systems.
c. Allow higher braking coefficients forsuitably maintained grooved or porous friction course runways. d. Use the brake torque limitations (I.e.,the amount oftorque the brake is capable ofproducing) that are determined on adry runway forboth wet and dry runways. The FAA considers the cornmenter's proposal to have considerable merit, not just as areplacement forthe demonstration option as the commenter proposes, but also as areplacement for the one-half the dry braking coefficient methodology. The cornmenter's proposal addresses the shortcomings inherent in the NPRM 93-8 methodology ofdetermining the wet runway braking coefficient by applying

aSingle adjustment factor tothe dry runway braking coefficient. Under the cornrnenter's proposal. the wet runway braking capability would more accurately reflect the Significant variation inbraking capability with speed that occurs on awet runway. Properly reflecting this variation with speed would remove the need to apply

afactor tothe dry runway brake torque capability. As adopted, §25.109(b) has been revised and new §§25.109 (c)and (d) have been added toprescribe wet runway accelerate-stop distance standards in amanner consistent with the cornmenter's proposal. This final rule isbased on the same information as the original FAA proposal: however, the methodology fordetermining wet runway accelerate-stop distances has been changed tomore rationally reflect the various factors affecting wet runway braking. The methodology adopted by this amendment provides amore accurate portrayal ofwet runway stopping performance than had been proposed in NPRM 93-8. Significant issues related tothe cornrnenter's proposal, which had tobe addressed prior topreparing 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 amethod for determining the capability ofan airplane's anti-skid system on awet runway. c. Establishing conservative levels of anti-skid capability that could be used in lieu ofdetermining this capability directly from test data. d. Determining whether ahigher braking capability is appropriate foruse with grooved orporous friction course runways. (This issue is discussed later along with other comments received on this topic). ESDU 71026 contains curves ofwet runway braking coefficients versus speed forsmooth and treaded tires at varying inflation pressures. These data

are presented forrunways ofvarious surface roughness, including grooved and porous friction course runways. Included in the data presentation are bands about each ofthe 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, itis 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, avalue must be specified (orassumed) for each ofthese variables. Since itwould beimpractical to try to measure or evaluate each of these variables forevery takeoff, the takeoff data must take into account the conditions likely to occur in operational service. Itwas the FAA's intent with the proposals ofNPRM 93-8 to define awet runway performance level that would

ensure safe operation forthe vast majority ofwet runway rejected takeoffs likely to occur. This same principle was used in specifying values for each ofthe variables considered by the adopted wet runway methodology. The resulting accelerate-stop distances, coupled with information provided to operators and pilots concerning the use ofthese data, should greatly reduce the risk ofrunway
overruns during wet runway operations. In defining the standard curves ofwet runway braking coefficient versus speed that are prescribed by the equations in §25.109(c) (1),the effects ofthe following variables were considered: Tire pressure, tire tread depth, runway surface texture, and the depth ofthe water on the runway. 

### TirePressure The effect oftire pressure is taken into account by providing separate curves (i.e., equations) in §25.109(c) (1)for

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several tire pressures. As stated in the adopted rule, linear interpolation may be used fortire pressures other than those listed. To provide additional safety, §25.109(c)(l) requires applicants tobase the accelerate-stop distances on the maximum tire pressure approved for operation. Operating at atire pressure that is lower than the maximum tire pressure approved forthat airplane will tend to improve the airplane's stopping capability on awet runway. Typically, manufacturer recommended tire pressures are afunction ofairplane weight; foroperations at less than the maximum approved weight, the recommended tire pressure would be less than the maximum approved tire pressure. 

### TireTreadDepth
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 ofthe tire forthis purpose. The texture ofthe runway surface plays an equally important role. ESOU 71026 provides braking data for both ribbed and smooth tires on runways ofdifferent surface textures. A method is also provided in ESOU 71026 for assessing the effects oftire wear. As ribbed tires wear, the depth ofthe 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 oftire removal can vary from about 1.5to 5 mm. Airplane manufacturers' maintenance manuals usually recommend removal when the tread depth is less than 1hzinch (l.2 mm), although operation with zero tread depth is not prohibited. Loss oftread depth is not the sole criterion fortire removal, however. Tires with significant tread depth remaining may beremoved for other reasons. Also, itis unlikely that all the tires on aparticular airplane would beworn tothe same extent. The standard curves (i.e., equations) ofbraking coefficient versus speed prescribed in §25.109(c)(l) are based on
atire tread depth of2mm. Since the tread depth ofnew tires is usually 10- 12rnm, 2mm represents no more than 20percent ofthe 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 apoint where no more than 20 percent ofthe 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 avery smooth texture (an average texture depth ofless than 0.004 inches), and is not very prevalent in runways used bytransport category airplanes. The majority ofungrooved 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

### WaterontheRunway 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 ofstanding water. In summary. the curves prescribed in §25.109(c)(l) represent the maximum tire-to-ground braking coefficient likely tobe available from awet runway during arejected takeoff. They were derived byinterpolating between the

curves presented in ESOU 71026 for runway surface categories Band C, adjusted torepresent tires with 2mm tread depth remaining. and extrapolated to cover the range ofVIspeeds tobe expected. The resulting curves were then smoothed and reduced to a mathematical form forinclusion in the rule. The capability foraparticular airplane type to achieve this braking coefficient depends on: (1)The amount oftorque its brakes are capable of producing, and (2)the performance of its anti-skid system. How the revised regulation addresses these two components isdiscussed in the ensuring paragraphs. The torque capability ofthe 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 tothe stopping force determined in meeting the requirements of§25.10 1(i) (worn brakes) and §25.109(a) (the dry runway acceleratestop distance). This provision prohibits applicants from using abrake 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 isreferred 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) forthe efficiency ofthe anti-skid system. Applicants will have the option ofeither determining the anti-skid system efficiency directly from flight tests on awet runway, orusing one of the anti-skid efficiency values specified in §25.109(c)(2). Regardless ofwhich method is used, an appropriate level of flight testing must be performed to verify that the anti-skid system operates in amanner 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). aminimum ofone complete wet runway stop, or equivalent segmented stops. should be conducted at an appropriate speed and energy to cover the critical operating mode ofthe anti-skid system. This testing can be performed as part ofthe anti-skid compatibility testing on awet 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 toverify 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. Asrevised, §25.109(c)(2) identifies three different classes ofanti-skid systems, and specifies aunique efficiency value associated with each

one. This classification ofanti-skid system types and the assigned efficiency values are based on information contained in Society ofAutomotive Engineers (SAE)Aerospace Information Report (AIR) 1739, title "Information on

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Anti-Skid Systems." The efficiency values prescribed in §25.109(c)(2) represent the worst system performance expected foreach type ofsystem after being properly tuned for operation on wet runways. The SAE document is available in the public docket forthis rulemaking. The three classes ofanti-skid systems represent evolving levels oftechnology and differing performance capabilities

on dry and wet runways. On/off systems
are the simplest ofthe three types of anti-skid systems. For these systems, full metered brake pressure (as commanded bythe pilot) is applied until wheel locking is sensed. Brake pressure isthen 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 offull pressure application/complete pressure release is repeated throughout the stop (oruntil the wheel ceases to skid with pressure applied). Quasi-modulating systems, the second type ofanti-skid system, attempt to continuously regulate brake pressure as
afunction ofwheel speed. Typically, brake pressure is released when the wheel deceleration rate exceeds a preselected value. Brake pressure isreapplied atalower level after alength of time appropriate tothe depth ofthe 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 apre-programmed sequence rather than the wheel speed time history. Fully modulating systems, the third type ofanti-skid system, are afurther refinement ofthe quasi-modulating systems. The major difference between these two types ofanti-skid systems is in the implementation ofthe skid control logic. During askid, corrective action isbased on the sensed wheel speed signal, rather than apreprogrammed response. Specifically, the amount ofpressure reduction or reapplication isbased on the rate at which the wheel isgoing into or recovering from askid. 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 toensure confidence in the efficiency obtained. Although additional flight testing will be necessary, the FAA does not expect applicants touse this method fordetermining the anti-skid efficiency unless proportionate benefits (i.e., an increase in takeoff weight) are obtained. Aminimum ofthree complete stops, orequivalent segmented stops, should beconducted on awet runway atappropriate speeds and energies to
cover the critical operating modes ofthe anti-skid system. As adopted, §25.109(b)(2)(ii) also requires applicants to adjust the wheel brakes stopping force totake into account the effect ofthe distribution of the normal load between braked and unbraked wheels atthe most adverse center-of-gravity position approved for takeoff. The stopping force due to braking is equal tothe braking coefficient multiplied bythe normal load (l.e.. the effective weight) on the braked wheels. The location ofthe airplane's center-of-gravity, which is a function ofthe airplane's configuration and how itis loaded (I.e.,the position ofpassengers, baggage, cargo, etc.), affects how the load isdistributed between braked and unbraked wheels. Typically, the nose wheels oftransport category airplanes are unbraked, although some airplanes also have some ofthe main gear wheels unbraked). This effect must betaken into account forthe most adverse center-of-gravity position approved fortakeoff. The most adverse center-of-gravity position isthat 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 tobe alogical outgrowth ofthe proposal published in NPRM 93-8. First, the final rule methodology relies on the same technical basis as the original proposal. Second, itresponds to acomment raised during the NPRM 93-8 public comment process. And third, itisconsistent with the overall intent ofthis rulemaking, which isto more rationally address relevant operational factors rather than applying more restrictive standards to all operating conditions. This methodology also provides applicants with the ability tobetter control any increased costs resulting from the addition ofwet runway accelerate-stop requirements topart 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 ofanti-skid system, takeoff speeds) and the level of wet runway testing to perform (r.e.,use ofthe 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 ofthe Federal Register is a notice ofavailability for aproposed revision toAC 25-7, "Flight Test Guide for Certification ofTransport Category Airplanes." Arequest for comments is included in that notice ofavailability. The proposed revision includes detailed guidance for:
a. Using reverse thrust in determining wet runway accelerate-stop distances; b. classifying the types ofanti-skid systems;
c. Verifying the type ofanti-skid system installed on the airplane and that itis 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 aform ofwet runway takeoff performance data, which is provided tothem bythe 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 §§91.605(b)(3), 121.l89(e), and 135.379(e) would result in retroactive changes to those airplanes forwhich 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 tobe included in the AFM.) This commenter notes that

use ofsuch 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, itis 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 formany years produced guidance information, including takeoff performance data, for wet runway operations. In general, the FAA supports the voluntary use ofthese available data to provide additional safety on wet runways for existing transport category airplanes, as long as compliance with the applicable

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airworthiness and operating rules is maintained. The FAA did not intend, bythe proposed wording §§91.605(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 ofthe AFM (containing the operating limitations) for aU.S. operator should only reflect the FARand should not contain extraneous information carried over from aforeign certification. Such information may, however, appear in an unapproved portion ofthe AFM as supplementary guidance information. Operators may use this information (as long as itdoes not conflict with the FAR), but are not required to abide by it.The FAA does not agree with the comment to limit application ofthe proposed operating rules only tothose airplanes certificated after this amendment becomes effective. Some manufacturers have elected to comply with the standards proposed in NPRM 93-8 prior tothe adoption ofthis final rule. The AFMs forthe affected airplane types contain takeoff and accelerate-stop distance limitations fortakeoffs on wet runways, and operators must comply with these limitations, regardless ofthe 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 aclarification that this provision applies to operating limitations, ifthey exist, associated with the minimum distances required for takeoff from wet runways. As discussed earlier, further consideration of retroactive application ofthe requirements adopted bythis final rule will be added to the FAA/JAA harmonization work program. Several commenters recommend that the proposed standards berevised to allow ahigher wet runway braking coefficient tobe used forgrooved runways orrunways treated with a porous friction course (PFC)overlay, without the need foradditional flight testing. These commenters point out that runway friction measurement tests show that awet runway with grooves or
aPFC surface overlay has much better friction characteristics than asmooth surface. According to these commenters, providing credit forthe improved stopping capability on these surfaces will result in significant public safety benefits byhelping to expedite future runway improvements and by providing

astrong incentive to properly maintain these surfaces. The commenters believe itis neither necessary nor in the public interest to avoid ordefer 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 avalue that the commenters consider tobevery conservative (i.e., amuch lower wet runway braking coefficient than would beexpected). Most ofthese commenters propose using awet runway braking coefficient forgrooved and PFC runways equal to 70percent ofthe dry runway braking coefficient, although

one commenter proposed afactor of80 percent. Forcomparison purposes, one commenter reports that tests conducted using aBoeing 737-300 airplane showed wet grooved runway braking capability that was equal to, orin some
cases greater than, 95 percent ofthat obtained on adry runway. The commenters note that alonger term rulemaking activity could be undertaken in the future to establish ahigher factor, ifwarranted. One ofthese commenters provided information relative to grooved and PFC runway credit inJapan. This commenter states that the Japanese Civil Aviation Bureau allows awet runway braking coefficient of70to 80percent ofthe dry runway value tobeused forgrooved or PFCrunways. InJapan, Most ofthe runways atcivil airports are grooved, and periodic friction surveys are conducted to assure that the surfaces are properly maintained. These surveys are done byusing acombination ofvisual 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 ofthese runway surface treatments and supports their use throughout the U.S. Tests conducted bythe FAA, NASA, and others confirm that applying afactor of 70percent tothe dry runway braking coefficient, asproposed bythe commenters, would conservatively represent the stopping performance on properly designed, constructed, and maintained grooved and PFC runways. Asummary ofthese test data has been placed in the docket. The actual friction capability ofgrooved and PFCrunways varies, however, depending on variables such asgroove shape, depth, and spacing, method used to construct the grooves, type ofpavement surface, volume and type ofairplane traffic, frequency ofpavement evaluations, and maintenance. The FARcurrently do not contain mandatory standards regarding the design, construction, and maintenance ofgrooved orPFC runways, but AC 150/5320-12B, "Measurement, Construction, and Maintenance ofSkid-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 70percent ofthe dry runway braking coefficient conservatively represents the stopping performance on properly designed, constructed, and maintained grooved orPFC runways. Using aSimple factor applied to the dry runway braking coefficient is appropriate forgrooved and PFC runways because the braking coefficient's variation with speed is much lower on these types ofrunways. 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 ofthe ESDUdata reveals that using asurface texture mid-way between surfaces 0and Ein combination with typical anti-skid efficiencies provides approximately the

same airplane stopping performance as using 70percent ofthe dry runway braking capability. In response to the comments regarding grooved and PFC runways, a
new §25.109(d) is adopted to establish

an optional wet runway braking coefficient forgrooved orPFC runways. The braking coefficient for determining the accelerate-stop distance on grooved and PFCrunways is defined in §25.109(d) aseither 70percent ofthe value used to determine the dry runway accelerate-stop distances, or avalue based on the ESDU data and derived in

amanner consistent with that used for ungrooved runways. Section 25.105(c)(l) is revised to allow applicants, attheir option, to provide data forgrooved and PFCrunways, in addition tothe smooth surface runway data that is currently required. In addition, the existing §25.109(d)is revised toremove 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 PFCrunways to be established as additional operating limitations, but approval to use these distances is limited torunways that have been designed, constructed, and maintained in amanner acceptable to the FAA Administrator. Inconjunction, §§91.605(b)(3), 121.l89(e), and l35.379(e) ofthe operating rules are

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amended to limit the use ofthe grooved and PFCwet runway accelerate-stop distances to runways that the operator has determined have been designed, constructed, and maintained in a
manner acceptable tothe FAA Administrator. The page(s) in the AFM containing the wet runway acceleratestop distances for grooved and PFC runways should contain anote equivalent tothe following: "These accelerate-stop distances apply only to runways that are grooved ortreated with

aporous friction course (PFC)overlay that the operator has determined have been designed, constructed, and maintained in amanner acceptable to the FAA Administrator." Airplane operators who wish touse the grooved orPFC runway acceleratestop distances must determine that the design, construction, and maintenance aspects are acceptable for each runway forwhich such credit is sought. In making these determinations, operators may rely on certifications from airport operators orindependent evaluations of runways. In either case, itis expected that operators will be able to demonstrate that their determinations

are well founded. Acceptable runways should be listed in Part Cofthe operator's approved operations specifications (forthose operators required tohave 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 touse operational landing distance forwet runways. After adoption ofthis final rule, the FAA also intends toinclude this information in

an update toAC 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 beprohibited when determining the dry runway accelerate-stop distances. Most ofthe 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 ofthe 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 ofarevision toAC25-7. In general, the FAA intends topropose that: (1)Acceptable procedures should be developed and demonstrated, including the time needed to accomplish these procedures; (2)the responses and interactions ofairplane systems should betaken into account; (3)the recommended level ofreverse thrust should beeasily obtainable under in-service conditions (e.g.,by providing

adetent orother tactile method ofthrust selection); (4)directional control should bedemonstrated with maximum braking

on awet runway with aten-knot crosswind from the most adverse direction; (5)the probability offailure should be no more than 1per 1000 selections; (6)inoperative thrust

reversers atdispatch should betaken into account; (7)satisfactory engine operating characteristics should be demonstrated; and (8)appropriate flight tests should beconducted to determine the effective stopping force provided by
reverse thrust. and to validate the total stopping force provided by all ofthe decelerating means. One commenter proposed an amendment tothe existing §25.109(c) to clarify that afinding of"safe and reliable" forany deceleration means other than wheel brakes must take into account the interactions and interdependencies ofthe various systems involved, and that consistent results must be expected under all conditions covered bythe AFM. This comment is directed primarily ata landing situation in which slippery runways and higher than normal approach speeds could thwart ordelay sensing logic for determining whether the airplane is on the ground. Consequently, the operation ofany deceleration means that can only be activated on the ground (e.g.,ground spoilers and thrust reversers) would also bedelayed. Under the existing §§25.109(c)and 25.1309, the FAA already reviews the system operation and intercompatibility issues that would be addressed bythe commenter's proposed changes to §25.109(c). Therefore, the FAA considers these proposed changes tobeunnecessary. One commenter noted that the same
reasons in the FAA's proposal for denying accelerate-stop distance credit forthe use ofreverse thrust on dry runways also apply to wet runways. Therefore, ifdry runway accelerate-stop distances need the safety margin provided bynot 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 ofthe proposal, the FAA believes that the additional safety provided bynot accounting forreverse thrust in calculating the accelerate-stop distance on adry runway is necessary to offset other variables that can significantly affect the dry runway accelerate-stop performance. Examples ofvariables 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 ofheat retained from previous braking efforts, etc. Although these variables may also be present forwet runways, their effects are adequately covered by the adopted method of determining the stopping capability on
awet runway. This method provides a margin ofsafety 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 forthe

use ofreverse thrust on dry runways, several commenters propose that reverse thrust credit be permitted, at least to the extent that itoffsets 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, itwould be appropriate toinclude the positive effect ofreverse 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 anormal part of operational stopping procedures. Also, the probability ofathrust reverser failing to operate, combined with the probability ofall brakes being atthe fully worn limit, isvery low, and there would bean even lower probability of these factors occurring in combination with atakeoff rejected from acritically high speed. Under the proposal offered by most ofthese commenters, the dry runway accelerate-stop distance would berequired to bethe greater ofeither: (1)The distance determined using new brakes without reverse thrust. or (2)the distance determined using worn brakes

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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 beto 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 forthe accelerate-stop distance on adry runway is necessary to offset other variables that can significantly affect the dry runway accelerate-stop performance. The effect ofthese other variables on the dry runway accelerate-stop distance are unchanged bythis rulemaking. Although the part 25 airworthiness standards are being made more stringent by adding requirements related toworn brakes and wet runways, the overall effect ofthese additions are partially offset bythe change in the method used to account forthe time ittakes the pilot to perform the procedures forrejecting the takeoff. Further alleviating provisions are inappropriate because they would unacceptably reduce the level ofsafety. Therefore, §§25.109(c) and (d)are amended asproposed in NPRM 93~8, except that they have been re-designated asparagraphs (e)and (t), respectively. As part ofthe proposed wet runway standards, §§ 25.13 (a)and (b)would allow the airplane's height over the end ofthe runway (known as the screen height) tobe reduced from 35 feet on dry runways to 15feet on wet runways. Some commenters object to reducing the

screen height forwet runways, stating that safety margins would bereduced fortakeoffs that are continued following

an engine failure. One commenter would accept areduced screen height only ifoperators 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 ofthe cornrnenter's proposed change to §25.105(a) (2). The FAA proposed reducing the required screen height forwet runways to re-balance the available safety margins, in amanner that does not impose Significant costs on airplane operators, when taking offfrom awet runway. On awet runway, the distance needed to stop the airplane increases significantly due tothe reduced braking effectiveness. On the other hand, the distance needed to complete a continued takeoff isgenerally unchanged from that needed foradry runway. Byreducing the required

screen height on awet runway, alower VIspeed can beused. The effect of lower VI speeds will beto reduce the number ofrejected takeoffs that occur
on wet runways, and toreduce the speed from which these takeoffs are rejected. The latter effect isconsidered especially important because the braking capability on awet runway is significantly poorer athigher speeds. As noted by one ofthe commenters, any reduction in the number oftakeoffs that are rejected will produce an equal number ofadditional continued takeoffs. Because ofthe lower VIspeed, the airplane's height over the end ofthe runway forthese takeoffs, aswell as the ensuring flight path, will be lower than would normally be achieved on adry runway. Ifaclearway area is available, however, the minimum height ofthe airplane over the end ofadry runway may, under the current standards, be as low as 13to 17feet. On this basis, the FAA considers aminimum screen height of 15feet tobe acceptable when the runway iswet. Allowing the screen height tobe reduced on wet runways also reduces the cost burden imposed on airplane operators bythe wet runway standards. Bytaking into account the degraded braking capability on wet runways, these standards may reduce the maximum weight atwhich the airplane would be allowed totake offfrom a given runway. Ifascreen height of35 feet were retained forwet runways, an
even greater reduction in takeoff weight capability could be necessary. In the proposed §25.113(c), the FAA intended torequire that the minimum

screen height on awet runway with a clearway would not belower than either: (1) 15feet, or (2)the screen height that could be achieved ifthe runway were dry. Aclearway is an area at least 500 feet wide beyond the departure end ofthe runway that has not obstacles protruding above a 1.25 percent upward sloping gradient. On a dry runway, up to one-half ofthe distance traversed between liftoff and a height of35 feet may be over the clearway. As noted earlier, the screen height (i.e., the height atthe end ofthe runway) achieved on adry runway with clearway may end up being as low as 13 feet. Accordingly, ahigher takeoff weight is possible when aclearway is present. The words "but not beyond the end ofthe runway" included in the proposal for §25.113(b) (2)would effectively require the wet runway
screen height tobe not less than 15feet. Under the proposed wording, therefore, the presence ofclearway could not be used toincrease the takeoff weight on a wet runway. Also, in some instances, the minimum screen height on awet 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 toNPRM 93-8, and the proposed wording for §§25.ll3(b) (2) and (c).One commenter noted that the words "but not beyond the end ofthe 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 avery 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 awet runway. The commenter notes that V1speed could then be reduced even further, thus providing additional safety in the event ofa rejected takeoff on awet runway. The FAA infers that this commenter is proposing that half ofthe distance traversed between liftoff and aheight of 15feet bepermitted to occur over the clearway. Because ofthe parabolic shape ofthe flight path, the airplane may end up being only five to eight feet high atthe end ofthe runway. The point atwhich the airplane lifts offwould thus bevery near the end ofthe runway. As discussed in NPRM 93-8, the FAA considers such asituation tobe unacceptable. The possibility of standing water on the wet runway, or operational considerations such as alate

orslow rotation to the liftoff attitude, emphasize the need torequire liftoff to
occur well before the end ofthe 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 awet runway is so small that itis 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 ofsimplifying and clarifying the rule language. The FAA concurs with this comment and is amending §25.113 accordingly. The phrase "but not beyond the end ofthe runway," contained in the proposed §25.ll3(b)(2), isremoved. The proposed §25.113(c) is clarified to prohibit ascreen height ofless than 15 feet on awet runway. Ifthe 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 atthe end ofthe takeoff distance remains 35 feet, clearway credit is allowed on awet runway in the same manner as itis allowed on adry runway. Also, §25.113 is amended to add the provision that in the absence ofclearway, the takeoff run is equal tothe takeoff distance. This provision is added only to ensure completeness ofthe definition oftakeoff

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 ofthe 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 awet runway (atthe wet runway VI speed) to be atleast as long as the corresponding distances on adry runway (atthe dry runway V1speed). These requirements therefore ensure that the maximum takeoff weight for awet 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 iswet. First, conduct the takeoff performance analysis assuming the runway is dry. Then, repeat the analysis using wet runway data, including the wet runway V1speed. The lowest takeoff weight from these analyses is the maximum takeoff weight that can be used when the runway iswet. For this takeoff weight, determine and compare the accelerate-stop and takeoff distances applicable toboth dry and wet conditions. The longer ofeach ofthese accelerate-stop and takeoff distances apply when the runway iswet. 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 tobe reduced by an amount corresponding tothe reduced

screen height allowed when taking off from awet runway. The commenter suggested that the current obstacle clearance criteria should beupdated to represent more realistic operational conditions. The commenter is referring to the criteria used to evaluate whether the obstacle must be cleared vertically,

orwhether an operator can consider the obstacle to belaterally outside ofthe airplane's path. The FAA iscurrently 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 tothe wear condition that provides the least effective braking performance. This comment is related to
asimilar comment regarding §25.101 (i). As discussed in response tothe 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 aflight test should berequired only ifpoor correlation exists between dynamometer test results and flight test results. The commenter also believes that arejected takeoff may not represent the most severe stopping condition. For example, landing atthe maximum landing weight with the flaps retracted may involve higher stopping energies. For this reason, the commenter suggests that §25.735(g) refer tothe most severe stop rather than arejected takeoff. The flight test proposed in §25.735(g) is the only flight test that would be required tobe conducted ataspecific brake wear level. The FAA considers this test to be anecessary demonstration ofthe airplane's ability to safely stop under the most critical rejected takeoff condition. For the remainder ofthe flight testing to determine the rejected takeoff and landing stopping distances, the brakes may be atany wear level desired bythe 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 tothe flight test results to determine the stopping distances for fully worn brakes. For the purposes ofthis demonstration, the FAA considers the maximum kinetic energy rejected takeoff tobe the most critical stopping condition. Therefore, the FAA does not
concur with the commenter's suggestion to replace the reference torejected takeoff in the flight test demonstration with areference tothe most severe stop. However, from abrake approval standpoint, the FAA agrees that the brakes, in the fully worn condition, should becapable ofabsorbing the energy produced during the most severe stopping condition. The FAA has tasked

aharmonization working group with recommending new orrevised requirements forapproval ofbrakes installed on transport category airplanes, and this working group is expected torecommend proposed standards addressing this issue. Another commenter suggests that the flight test demonstration referenced by the proposed §25.735(g) should include

atwo-second overshoot ofVI, before applying the brakes, to allow forthe average pilot response time. The FAA does not concur with this comment because VI represents the highest speed atwhich the pilot should take the first action toreject the takeoff. Also, the procedures used during the flight test demonstration, including the time at which the pilot applies the brakes, should beconsistent with the rejected takeoff procedures provided by the applicant in the AFM. One commenter proposed that §25.735(f) beclarified to allow for other devices inherent in aparticular airplane design that may be used to dissipate energy. Failure to allow such credit, claims the commenter, will diminish the value oftechnological improvements in energy dissipation devices that are likely tobe introduced toimprove airplane stopping performance under wet runway conditions. The current §25.735(f) allows forthe

use ofthe 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 ofthe brake is generally more ofaconcern on adry runway than on
awet runway because ofthe 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 ofthe amended §25.109(e). Within these constraints, the FAA will consider any technological improvements in energy deceleration devices atthe 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, becapable ofabsorbing the maximum kinetic energy forwhich itis approved. However, these commenters note that the kinetic energy level defined in §25.735(f) isthe same energy level used in Technical Standard Order (TSO)- C26c fordemonstrating the capability of the brake to successfully complete 100 landing stops with no refurbishment or other changes made tobrake system components (except for one change in

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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 ofthe relationship between §25.735(f) and the TSO, any change tothe definition ofthe energy level in §25.735(f) would presumably also apply to the TSO. Since the TSO lOtl-stop test is intended toverify that the brake has acceptable structural durability, rather than to demonstrate the capability to successfully complete

ahigh energy stop in the fully worn condition. the combination ofthe worn condition with the TSO energy level would be inappropriate. Abrake that is fully worn atthe beginning ofthe 100- stop test would be unable to successfully complete the test. One ofthe commenters notes that the TSO also requires atest involving one stop atthe maximum rejected takeoff kinetic energy. According to the cornrnenter, itis this test that should be conducted with afully worn brake. The energy rating demonstrated by this test is not explicitly referenced in part 25. but is contained inJAR-25 asJAR 25.735(h). The commenter proposes adding JAR25.735(h) topart 25to harmonize the two standards and to help clarify the application ofthe worn brake requirements. This commenter also suggests adding references tothe applicable TSO and clarifying that the formula provided in §25.735(f)(2)need only be modified in cases ofdesigned unequal braking distributions. Uneven braking distributions can unintentionally occur during flight tests. but this characteristic cannot be predicted during the design or qualification stages forwhich §25.735(f)(2) isrelevant. The FAA concurs with these proposals. As amended. §25.735(f) defines the landing kinetic energy rating to beused during qualification testing per the applicable TSO orother qualification testing used to show an equivalent level ofsafety. 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 toAC 25-7. forwhich the notice ofavailability is published elsewhere in this issue ofthe Federal Register. the FAA proposes to clarify that the relevant TSO lOu-stop test may begin with abrake in any condition representative ofservice use. including

new. In addition. anew §25.735(h). based onJAR25.735(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 afully 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 tobe modified only in the case of designed unequal braking distributions. The format ofthe existing §25.735(f)(2). with respect tothis provision. has been adjusted to conform toFederal Register formatting guidelines. and the new §25.735(h)(2) has been formatted similarly. With these changes. the final rule better matches the intent ofthe NPRM 93-8 proposals. and also harmonizes these sections with JAR-25. The FAA intends torevise TSO-C26c tobeconsistent with these amendments to §25.735. The Aviation Rulemaking Advisory Committee (ARAC)has been chartered with recommending appropriate changes tothe TSO. Currently. the FAA envisions issuing the revised TSO. applicable totransport category airplanes. under anew designation. TSO-C 135. One commenter suggests that the proposed §25.735(g) should bedeleted. This commenter believes that this proposed flight test requirement is misplaced in the brake design and construction section ofpart 25. The commenter suggests that this issue should be addressed in the flight test guidance provided in AC25-7. The FAA concurs that the proposed flight test requirement would bebetter placed elsewhere. but does not concur with completely removing itfrom part 25. As stated previously. the FAA considers this test tobe anecessary demonstration ofthe airplane's ability to safely stop under the most critical rejected takeoff condition. In addition. the FAA intends forthis test to determine orvalidate the AFM accelerate-stop distance forthis 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 ofthis proposal isto require that takeoff performance information forwet runways beincluded 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 bythe surface condition ofthe 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, byreplacing the reference to §25.103 with areference to §25.109. One commenter strongly endorses a requirement to add atakeoff performance monitor to the flight deck ofall airplanes to help pilots determine whether atakeoff should be rejected or continued. The commenter notes that modern transport category airplanes already contain most ofthe necessary instrumentation. According to the comrnenter, all that would be needed would be adisplay and adedicated processor to compute the data to be displayed. The FAA has participated in past evaluations ofsystems designed to monitor the performance ofthe airplane during the takeoff. Such systems typically compare the airplane's actual performance. as determined by airplane instrumentation. with the performance predicted bythe AFM. Ifthe airplane's performance is less than predicted. the performance shortfall would be indicated bythe monitor. In addition. the takeoff speeds. V1and VR. could be correlated with the point on the runway atwhich they should bereached. This information could assist pilots in determining whether itis safer to reject

orto continue the takeoff. The FAA supports efforts at improving the go/no-go decision process. Advisory Circular 25-15. "Approval ofFlight Management Systems in Transport Category Airplanes." provides ameans to obtain FAA approval ofatakeoff performance monitor function as part ofaflight 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 oftransport category airplanes. Varying winds during the takeoff or a runway with avariable slope may cause the monitor to provide afalse indication. The FAA is also concerned that the number ofhigh speed rejected takeoffs could increase as pilots delay action to determine. for example. ifan initially SUb-paracceleration is corrected. Also. unnecessary rejected takeoffs could occur as aresult ofsmall

### 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. Atakeoff performance monitor would need to consider all ofthe 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. His possible to design such asystem, but current systems have not demonstrated asafety benefit over the information currently available tothe pilot. The same commenter recommends that the FAA undertake astudy using research simulators to validate airplane/ pilot performance in obstacle limited takeoffs with engine failures. The objective ofthis study would be to determine ifthere is ahigh degree of reliability that the combined airplane/ pilot performance is acceptable. The commenter feels that such astudy is essential to considerations oflower

screen heights, tailwind takeoffs, and pilot decision making when the takeoff weight is limited by obstacle clearance considerations. Inthe 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 ofthe 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 bebased on the procedures established by the applicant for operation in service, and assume that

one engine fails atVEF

. Except for automatic propeller feathering and retraction ofthe landing gear, the airplane configuration must remain constant, and changes in power or thrust that require action by apilot may not be made until the airplane reaches

aheight of400 feet above the takeoff surface. In addition tothe takeoff path determined under §25.111, §25.115 requires applicants to determine the net takeoff flight path. The net takeoff flight path begins atthe end ofthe takeoff distance and is equal tothe takeoff flight path with the gradient ofclimb reduced by: 0.8 percent fortwo-engine airplanes; 0.9 percent forthree-engine airplanes; and 1.0percent forfour-engine airplanes. These adjustments tothe airplane's demonstrated climb gradient capability represent asafety 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 aheight ofatleast 35 feet. The current airworthiness standards already address the issues the commenter proposes forfurther study. For each part 25 airplane type design, applicants must conduct flight tests to validate the capability ofthe 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 byICAOwould require airplane operators to consider alarger ground area tobe under the takeoff flight path when determining which obstacles must be cleared vertically. An obstacle that can be considered tobe cleared laterally under current FAA practices may have tobecleared vertically under the ICAO recommendations. This change could result in restricting the amount ofcargo
orpassengers tobe 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 ofthe ground area that must be considered when determining which obstacles must becleared vertically. 

### Regulatory Evaluation Summary Proposed changes toFederal regulations must undergo several economic analyses. First. Executive Order 12866 directs that each Federal agency shall propose or adopt a regulation only upon areasoned determination that the benefits ofthe intended regulation justify its costs. Second, the Regulatory Flexibility Act of 1980requires agencies to analyze the economic effect ofregulatory 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 thatjustify its costs as defined in the Executive Order; (2)will not have asignificant impact on
asubstantial number ofsmall entities; and (3)will not constitute abarrier to international trade. These analyses, available in the docket, are summarized below. Inorder to analyze the potential net costs ofthe rule, this evaluation considers ahypothetical production program forarepresentative 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 sothat total production equals 500, (5)each airplane isretired atthe end ofits 25 year design service goal, and (6)the discount rate is 7percent. The analysis ofincremental costs is divided into two cases: one which

assumes abrake design that exhibits little decline in brake performance with wear, and another which assumes a brake design that exhibits adecline 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 isgreater 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 ofincremental certification and development costs), then, will be reduced by approximately $28.9 million forthe 500 airplane fleet

over its 34year service life. On a discounted basis, total fleet costs will be reduced by approximately $7.5 million. Inthe 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 bythe 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 (innominal terms) per year per airplane to operating costs. Therefore, lifetime incremental costs (again including consideration ofFederal Register 

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incremental certification and development costs) forthe 500 airplane fleet are approximately $34.9 million, or $9.6 million on adiscounted basis. It should be emphasized, however, that FAA anticipates that future airplane models will incorporate brake designs that exhibit little reduction inbraking 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 aqualitative 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 toreduce the specified level of allowable wear in return forsome 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 adisproportionate share ofthe total. Infact, the wet runway rejected takeoff accident rate (involving substantial damage orhull 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 forwet runway conditions. Second, itcreates an economic incentive to develop more stringent maintenance programs forskid-resistant runway surfaces. 

### RegulatoryFlexibilityDetermination 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 RFArequires agencies toreview rules which may have "a significant economic impact on asubstantial number ofsmall 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 bythe rule include manufacturers oftransport category airplanes (SIC3721) and operators of aircraft forhire (SIC4511). There are no manufacturers of transport category airplanes that meet the SIC3721 size threshold forsmall entities (75employees). However, small air carriers operating transport category airplanes could be affected bythe rule. Order 2100.14A defines asmall carrier

as one owning 9orfewer aircraft. The definition of"significant economic impact" varies by air carrier type: for operators whose fleets consist entirely ofaircraft having aseating capacity of

more than 60passengers the threshold is $123,445, forother 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 anineairplane fleet. Assuming that all incremental certification costs are passed on tothe operator, the rule would increase the price ofan airplane by $1,570. When this is amortized over the 25-year life ofthe airplane (assuming a7% discount rate), the incremental cost per airplane is approximately $126 per year or $1,134 per year for anine-airplane fleet. An upper-bound estimate ofthe annual impact ofthe 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 ofsmall entities. 

### UnfundedMandatesReformAct Title IIofthe Unfunded Mandates Reform Act of 1995 (the Act), enacted as Pub. L. 104-4 on March 22,1995, requires each Federal agency, tothe extent permitted by law, toprepare a written assessment ofthe effects ofany Federal mandate in aproposed orfinal agency rule that may result in the expenditure by State, local, and tribal governments, in the aggregate, orby the private sector, of$100 million ormore (adjusted annually forinflation) in any
one year. Section 204(a)ofthe Act, 2 U.s.C. l534(a), requires the Federal agency to develop an effective process to permit timely input by elected officers (ortheir designees) ofState, local, and tribal governments on a proposed "significant intergovernmental mandate." A "significant intergovernmental mandate" under the Act is any provision in aFederal 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 ofthe Act, 2U.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 aplan that, among other things, provides fornotice to potentially affected small governments, ifany, and for a meaningful and timely opportunity to provide input in the development of regulatory proposals. The rule does not contain any Federal intergovernmental orprivate sector mandate. Therefore, the requirements of Title IIofthe Unfunded Mandates Reform Act of 1995 do not apply. 

### TradeImpactAssessment Recognizing that nominally domestic regulations often affect international trade, the Office ofManagement and Budget directs Federal agencies to
assess whether ornot arule or regulation will have the effect of lessening the restraints ofany 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 amore equitable basis regarding their marketability. The standardization of certification criteria between the FAA and the Joint Aviation Authorities OAA) ofEurope, and the equalization ofsafety levels forpre- 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 ofpower and responsibilities among the various levels ofgovernment. Therefore, in accordance with Executive Order 12612, itisdetermined that this final rule will not have sufficient federalism implications towarrant the preparation ofaFederalism Assessment.
International Civil Aviation Organization (ICAO) and Joint Aviation Regulations
Inkeeping with U.S. obligations under the Convention on International Civil Aviation, itis FAA policy to comply with ICAO Standards and Recommended Practices to the maximum extent practicable. The FAA has determined that this rule does not

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conflict with any international agreement ofthe United States. Paperwork Reduction Act
In accordance with the Paperwork Reduction Act of 1990 (44U.s.C. 3501 

### etseq.). there are not reporting or recordkeeping requirements associated with this rule. Regulations Affecting Intrastate Aviation in Alaska Section 1205 ofthe FAA Reauthorization Act of 1996 (110 Stat. 3213) requires the Administrator, when modifying regulations in Title 14ofthe CFRin amanner affecting intrastate aviation in Alaska, to consider the extent towhich Alaska is not served by transportation modes other than aviation, and to establish such regulatory distinctions as he orshe considers appropriate. Because this final rule applies to the certification offuture designs oftransport category airplane and their subsequent operation, itcould 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, itwould be inappropriate to establish aregulatory distinction forthe intrastate operation of affected airplanes in Alaska.
List ofSubjects
14 CFRPart 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 ofthe Amendment
In consideration ofthe foregoing, the Federal Aviation Administration amends 14CFRparts 1,25, 91,121. and 135ofthe Federal Aviation Regulations (FAR)asfollows:

PART 1-DEFINITIONS AND ABBREVIATIONS
I. The authority citation forpart 1 continues toread asfollows: Authority: 49 U.s.C. 106(g), 40113, 44701. 2. Section 1.2is amended by adding

anew abbreviation "VEF" and revising the description forthe abbreviation "V I" toread as follows: §1.2 Abbreviations and symbols.



### * * * * * VEF means the speed atwhich the critical engine is assumed to fail during takeoff.



### * 

### * * * 

### * V Imeans the maximum speed in the takeoff atwhich 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 Ialso means the minimum speed in the takeoff, following afailure ofthe critical engine atVEF, atwhich 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 forpart 25 continues toread asfollows: Authority: 49 U.S.C. 106(g), 40113, 44701~ 44702,44704. 4. Section 25.101 is amended by adding anew 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 atthe fully worn limit oftheir allowable wear range. 5. Section §25.105 is amended by revising paragraph (c)(1)toread as follows: §25.105 Takeoff.



### * * *

* * (c) 

### * * * (1)Inthe case ofland planes and amphibians: (i) Smooth, dry and wet, hardsurfaced runways; and (ii)Atthe option ofthe applicant, grooved orporous friction course wet, hard-surfaced runways.



### * * * * * 6. Section §25.107 is amended by revising paragraph (a)(2)toread as follows:
§25.107 Takeoff speeds. (a) 

### * * * (2)VI. in terms ofcalibrated 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 atwhich the critical engine is failed, and the instant atwhich the pilot recognizes and reacts to the engine failure, as indicated by the pilot's initiation ofthe 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) toread as follows:
§25.109 Accelerate-stop distance. (a)The accelerate-stop distance on a dry runway is the greater ofthe following distances: (1)The sum ofthe distances necessary to-(i) Accelerate the airplane from a standing start with all engines operating toVEF fortakeoff from adry runway; (Il) Allow the airplane to accelerate from VEF to the highest speed reached during the rejected takeoff, assuming the critical engine fails atVEFand the pilot takes the first action toreject the takeoff atthe V Ifortakeoff from adry runway; and (iii) Come to afull stop on adry runway from the speed reached as prescribed in paragraph (a)(1)(ii) ofthis section; plus (iv) Adistance equivalent to 2 seconds atthe V Ifortakeoff from adry runway. (2)The sum ofthe 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 atthe VIfortakeoff from adry runway; and (n) With all engines still operating,

come to afull stop on dry runway from the speed reached as prescribed in paragraph (a)(2)(i) ofthis section; plus (iii) Adistance equivalent to 2 seconds atthe V1 fortakeoff from adry runway.

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

### 8319



## MaximumBrakin~ 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 ofthe following distances: (1) The accelerate-stop distance on a dry runway determined in accordance with paragraph (a)ofthis section; or (2) The accelerate-stop distance determined in accordance with paragraph (a)ofthis section. except that the runway iswet and the corresponding wet runway values ofVEF and V I are used. In determining the wet runway accelerate-stop distance. the



## TjrePressure (psi)

50

100

200

300

BilliNG CODE 491G-13-CWhereTire Pressureernaximum airplane operating tire pressure (psi); IltigMAX=maximumtire-to-ground braking coefficient; Veairplane true ground speed (knots); and Linear interpolation may beused fortire pressures other than those listed. (2) The maximum tire-to-ground wet runway braking coefficient offriction must be adjusted to take into account the efficiency ofthe anti-skid system on
awet runway. Anti-skid system operation must be demonstrated by flight testing on asmooth wet runway, and its efficiency must be determined. Unless aspecific 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)ofthis section; and (il)The force resulting from the wet runway braking coefficient offriction determined in accordance with paragraphs (c)or (d)ofthis section. as applicable. taking into account the distribution ofthe normal load between braked and unbraked wheels atthe most

quantitative analysis ofthe flight testing

on asmooth wet runway. the maximum tire-to-ground wet runway braking coefficient offriction determined in paragraph (c)(I) ofthis section must be multiplied bythe efficiency value associated with the type ofanti-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)Atthe option ofthe applicant. a higher wet runway braking coefficient of friction may beused forrunway surfaces that have been grooved or adverse center-of-gravity position approved fortakeoff. (c)The wet runway braking coefficient offriction for asmooth wet runway is defined as acurve offriction coefficient versus ground speed and must be computed as follows: (1) The maximum tire-to-ground wet runway braking coefficient offriction is defined as:

BilLING CODE 4910-13-M

treated with aporous friction course material. For grooved and porous friction course runways. the wet runway braking coefficent offriction is defined

as either: (1) 70percent ofthe dry runway braking coefficient offriction used to determine the dry runway acceleratestop distance; or (2) The wet runway braking coefficient defined in paragraph (c)of this section. except that aspecific antiskid system efficiency. ifdetermined, is appropriate for agrooved orporous friction course wet runway. and the maximum tire-to-ground wet runway braking coefficient offriction is defined

as:

BilLING CODE 4910-13-M

### 8320 Federal Register/Vol. 63. No. 32/Wednesday. February 18. 1998/Rules and Regulations



## TirePressure (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.1tJgMAX 

## =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

BilLINGCODE4910-13-CWhereTire Pressure.-rnaxtrnum airplane operating tire pressure (psi); /ltigMAx=maximum tire-to-ground braking coefficient; Veairplane true ground speed (knots); and Linear interpolation may beused fortire pressures other than those listed. (e)Except as provided in paragraph (f)(1)ofthis section. means other than wheel brakes may beused to determine the accelerate-stop distance ifthat

means-



## * * * * 

### * (f) The effects ofavailable reverse thrust- (1)Shall not be included as an additional means ofdeceleration when determining the accelerate-stop distance

on adry runway; and (2)May be included as an additional

means ofdeceleration using recommended reverse thrust procedures when determining the accelerate-stop distance on awet runway. provided the requirements ofparagraph (e)ofthis section are met.



### * * * * * (h)Ifthe accelerate-stop distance includes astopway with surface characteristics substantially different from those ofthe runway. the takeoff data must include operational correction factors forthe accelerate-stop distance. 

### * * * (i)Aflight test demonstration ofthe maximum brake kinetic energy accelerate-stop distance must be conducted with not more than 10 percent ofthe allowable brake wear range remaining on each ofthe 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

anew paragraph (b)toread as follows: §25.113 Takeoff distance andtakeoff run. (a)Takeoff distance on adry runway isthe greater of- (1)The horizontal distance along the takeoff path from the start ofthe takeoff to the point atwhich the airplane is 35 feet above the takeoff surface. determined under §25.111 for adry runway; or



### * 

## * * * * (b)Takeoff distance on awet runway isthe greater of- (1)The takeoff distance on adry runway determined in accordance with paragraph (a)ofthis section; or (2)The horizontal distance along the takeoff path from the start ofthe takeoff to the point atwhich the airplane is 15 feet above the takeoff surface. achieved in amanner consistent with the achievement ofV2before reaching 35 feet above the takeoff surface. determined under §25.111 forawet runway. (c)Ifthe takeoff distance does not include aclearway. the takeoff run is equal to the takeoff distance. Ifthe takeoff distance includes aclearway- (1)The takeoff run on adry runway isthe greater of- (i) The horizontal distance along the takeoff path from the start ofthe takeoff to apoint equidistant between the point atwhich VLOF is reached and the point atwhich the airplane is 35 feet above the takeoff surface. as determined under §25.111 for adry runway; or (ii) 115percent ofthe horizontal distance along the takeoff path. with all engines operating. from the start ofthe takeoff to apoint equidistant between the point atwhich VLOF isreached and the point atwhich the airplane is 35 feet above the takeoff surface. determined by

aprocedure consistent with §25.111. (2)The takeoff run on awet runway isthe greater of- (I)The horizontal distance along the takeoff path from the start ofthe takeoff to the point atwhich the airplane is 15 feet above the takeoff surface. achieved in amanner consistent with the achievement ofV, before reaching 35 feet above the takeoff surface. as determined under §25.111 for awet runway; or (H) 115percent ofthe horizontal distance along the takeoff path. with all engines operating. from the start ofthe takeoff to apoint equidistant between the point atwhich VLOF is reached and the point atwhich the airplane is 35 feet above the takeoff surface. determined by

aprocedure 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 tobegin 35 feet above the takeoff surface atthe end ofthe takeoff distance determined in accordance with §25.113(a) or (b).as appropriate forthe runway surface condition.



### * 

## * * 

### * * 10. Section 25.735 is amended by revising paragraphs (f) introductory text and (f)(2)and adding anew paragraph (h)toread as follows: §25.735 Brakes



## * * 

### * * * (f) The design landing brake kinetic energy capacity rating ofeach main wheel-brake assembly shall be used during qualification testing ofthe 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 ofthe following methods: (1) 

### * * * (2)Instead ofarational analysis. the kinetic energy absorption requirements for each main wheel-brake assembly may be derived from the following formula. which must bemodified in

cases ofdesigned unequal braking distributions.

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

### 8321

2 

### KE

## = 0.0443WY

NWhereKE=Kinetic energy per wheel (ft.vlb.): W=Design landing weight (lb.); Y=Airplane speed in knots. Vmust not be less than Vso.the power off stalling speed ofthe airplane at sea level. atthe design landing weight, and in the landing configuration; and N=Number ofmain wheels with brakes.



### * 

## * * * * (h)The rejected takeoff brake kinetic energy capacity rating ofeach main wheel-brake assembly that is atthe fully

worn limit ofits allowable wear range shall beused during qualification testing ofthe brake to the applicable Technical Standard Order (TSO) oran acceptable equivalent. This kinetic energy rating may not be less than the kinetic energy absorption requirements determined under either ofthe following methods: (l) The brake kinetic energy absorption requirements must bebased

on arational analysis ofthe sequence of events expected during an acceleratestop maneuver. This analysis must include conservative values ofairplane speed atwhich the brakes are applied. braking coefficient offriction between tires and runway. aerodynamic drag. propeller drag orpowerplant forward thrust. and (ifmore critical) the most adverse single engine orpropeller malfunction. (2)Instead ofarational 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 ofdesigned unequal braking distributions:



### KE

## = 0.0443WY2
NWhereKE=Kinetic energy per wheel (ft.-lb.); W=Airplane weight (lb.); V=Airplane speed (knots); NeNurnbcr ofmain wheels with brakes; and Wand Vare the most critical combination oftakeoff weight and ground speed obtained in arejected takeoff. 11. Section 25.1533 is amended by revising paragraph (a)(3)toread 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 ofthis part (including the provisions of§§25.109 and 25.113, forweights, altitudes, temperatures, wind components, runway surface conditions (dry and wet). and runway gradients) for smooth, hard-surfaced runways. Additionally, at the option ofthe applicant. wet runway takeoff distances may be established for runway surfaces that have been grooved

ortreated with aporous friction course, and may be approved foruse on runways where such surfaces have been designed constructed. and maintained in amanner acceptable to the Administrator.



### * * * 

## * *
PART 91-GENERAL OPERATING AND FLIGHT RULES
12.The authority citation forpart 91 continues toread asfollows: 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 12and 29 ofthe Convention on International Civil Aviation (61 Stat. 1180), 902. 13.Section 91.605 is amended by revising paragraph (b)(3)toread 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 tocorrespond with the minimum distances required fortakeoff. considering the elevation ofthe airport. the runway tobeused. the effective runway gradient. the ambient temperature and wind component atthe time oftakeoff, and. ifoperating limitations exist forthe minimum distances required fortakeoff from wet runways. the runway surface condition (dry orwet). Wet runway distances associated with grooved orporous friction course runways, ifprovided in the Airplane Flight Manual, may be used only forrunways that are grooved

ortreated with aporous friction course (PFC)overlay. and that the operator determines are designed. constructed. and maintained in amanner acceptable to the Administrator.



### * * * 

### * *
PART 121-0PERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL OPERATIONS
14.The authority citation forpart 121 continues toread 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)toread 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) ofthis section. correction must be made for the runway tobe used, the elevation ofthe airport. the effective runway gradient. the ambient temperature and wind component atthe time oftakeoff, and. ifoperating limitations exist for the minimum distances required fortakeoff from wet runways, the runway surface condition (dry orwet). Wet runway distances associated with grooved or porous friction course runways, if provided in the Airplane Flight Manual. may beused only forrunways that are grooved ortreated with aporous 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 forpart 135 continues toread 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)toread as follows: §135.379 Largetransport category airplanes: Turbine engine powered: Takeoff limitations.



### * * * * * (e)In determining maximum weights. minimum distances. and flight paths under paragraphs (a)through (d)ofthis section, correction must be made forthe runway tobe used. the elevation ofthe airport. the effective runway gradient, the ambient temperature and wind component atthe time oftakeoff. and. ifoperating limitations exist forthe minimum distances required for takeoff from wet runways, the runway surface condition (dry orwet). Wet runway distances associated with grooved or porous friction course runways. if provided in the Airplane Flight Manual. may be used only forrunways that are grooved ortreated with aporous friction

course (PFC)overlay, and that the operator determines are designed, constructed, and maintained in a
manner acceptable to the Administrator.



### * 

### * * * * Issued in Washington. DCon February 10. 1998. Jane F. Garvey. Administrator. [FRDoc. 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 forDetermining Rejected Takeoff and

Landing Performance

Regulatory ImpactAnalysis
Department ofTransportation OfficeofAviationPolicyandPlans

RIN:2l20-ABl7 63Federal Register 8298 

# February 18, 1998

This analysis was issuedbythe agency andcollected bytheAEI-Brookings JointCenter inorder to promote regulatory transparency. The views expressed in this document are those of the agency anddonotnecessarily reflectthoseoftheJointCenter.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 

# (14CFR Part 25)

Office ofAviation Policy and Plans Aircraft Regulatory Analysis Branch, APO-320

Gregory 

# v,Won March, 1996

### Table of Contents

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

I. Introduction.

. . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . 1

II. Description of Rule.......

. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 A. Definitions...................................................... 2 B. Two-second margin.

. .. . . .. . .. .. . . . .. . . ... .. . . . . . .. . . . .. . . . . . . . . . . . 3 C. Wornbrake accountability..

. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 3 D. Wetrunway 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.eutive 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 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.

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

The rule will reduce this margin to the distance traveled §25 

### .109 (a) (1) 

### (ii)]

.
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, using

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 0I2SA

-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. II

### c" 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 Statistics 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

additional 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 with wear, the

average reduction in dry runway accelerate-stop distance associated with the

revised 2-second-at-V1 

### requirement is offset by the average increase in dry

runway accelerate-stop distance associated with the worn brake requirement.

Again, however, the wet runway requirements 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

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.

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.

24

### 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.

25

### 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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