1、Designation: E3188 19Standard Terminology forAircraft Braking Performance1This standard is issued under the fixed designation E3188; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses
2、 indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 The terms and definitions listed provide a common setof definitions and concepts that have been agreed upon by theSociety of Aircraft Performance and Operat
3、ions Engineers.While historical reports and studies may use different terms, allconcepts should be relatable to the definitions listed.1.2 Several discussion sections are included to providecontext. The definitions and discussions serve to formallycapture industry best practices and common methods t
4、hat relateto aircraft certification, aircraft operation, and airport opera-tions under standard FAA and ICAO guidance.1.3 UnitsThe values stated in SI units are to be regardedas standard. There are no SI units used in these definitions.New values relating to braking coefficients are describedbelow.1
5、.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.
6、1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to
7、 Trade (TBT) Committee.2. Referenced Documents2.1 FAA Documents:2AC 25-31 Takeoff Performance Data for Operations onContaminated RunwaysAC 25-32 Landing Performance Data for Time-of-ArrivalLanding Performance AssessmentsAC 91-79A Mitigating the Risks of a Runway OverrunUpon LandingAC 150/5200-30D Ai
8、rport Field Condition Assessments andWinter Operations Safety2.2 Federal Aviation Regulation:3FAR 25.109 Accelerate-Stop Distance3. Significance and Use3.1 The terminology listed below allows for standardizedand specific language to be given to concepts surrounding theidentification of, recording, a
9、nd communication of vehiclewheel braking. The terms are designed to specifically allowmanufacturers, operators, regulators, research agencies, andinvestigative agencies the ability to communicate essentialconcepts in a manner that can be directly applied to operationalrequirements.4. Terminology4.1
10、Definitions:aircraft braking action report, na report given describing alevel of braking action using data from the aircraft.aircraft braking coefficient, Aircraft, nthe ratio of thedeceleration force from the braked and unbraked wheels ofa braked aircraft relative to the sum of the vertical (normal
11、)force acting on the aircraft. Aircraft braking coefficient isdetermined by using the weight of the aircraft (W-L) andencompasses all the braking forces of all the gear, even thosethat are not braked.DISCUSSIONThe practice of calculating this type of braking coeffi-cient value has been used in the p
12、ast, most commonly with reference toBoeing aircraft. The industry is moving away from this practice, andmodern guidance will most often refer to wheel braking coefficients.aircraft braking simulation equipment, nground-basedequipment that is used to simulate or model an aircraftbraking system and it
13、s wheel braking coefficient.airport friction measurements, nthe value obtainedthrough ground measurement devices approved for use inmeasuring runway surface friction characteristics.DISCUSSIONThese machines are not required to utilize the samesystem components nor analysis methods as used for certif
14、ied aircraft.Ground equipment runway friction coefficient values are normally the1This terminology is under the jurisdiction of ASTM Committee E17 on Vehicle- Pavement Systems and is the direct responsibility of Subcommittee E17.26 onAircraft Friction.Current edition approved Feb. 1, 2019. Published
15、 February 2019. Originallyapproved in 2019. DOI: 10.1520/E3188-19.2Available from Federal Aviation Administration (FAA), 800 IndependenceAve., SW, Washington, DC 20591, http:/www.faa.gov.3Available from U.S. Government Printing Office, Superintendent ofDocuments, 732 N. Capitol St., NW, Washington,
16、DC 20401-0001, http:/www.access.gpo.gov.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision o
17、n Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1result of two major classes of equipment. A continuous frictionmeasuring device (CFME) normally applies a fixed slip into a conti
18、nu-ously rotating tire to measure friction. A decelerometer (DEC) mea-sures the deceleration force (in Gs) associated with the braking of avehicle. Measurements from both types of devices are normally givenin numerical format but represent different values. It is alwaysimportant to understand which
19、device is being used and what the valuethe delivered number represents. The FAA has determined that thereexists no correlation between these devices and wheel braking coeffi-cients from airplanes.DISCUSSIONRunway friction coefficient values are commonly re-ferred to using the term “MU” or its associ
20、ated Greek symbol, “.” Thisis also a term used to describe wheel braking coefficient values foraircraft, although it is common to see aircraft terms associated withsubscript qualifiers such as “Brakes.” It is important to understand thatrunway friction values and aircraft braking values are not equi
21、valent. Itis considered a best practice to use the more specific terms listed in thisdocument rather than the general term “MU” to avoid confusion.anti-skid efficiency, na value, given as a percentage, thatrepresents an anti-skid systems ability to optimize thetire-to-ground friction coefficient clo
22、se to the maximumvalue. This is usually taken as an average over time duringfriction limited braking.assumed (predicted) wheel braking coefficient, na coeffi-cient value that is used to predict braking performance.DISCUSSIONThe values listed in AC 25-32 allow the creation ofpredicted wheel braking c
23、oefficient values.autobrakes, nan automated aircraft control system thatnormally allows a flight crew to select a targeted decelera-tion rate to be achieved for the landing rollout.DISCUSSIONThis rate is normally obtained by modulating the wheelbrakes as necessary to achieve the rate desired if the
24、other forces actingto slow the aircraft do not by themselves achieve the desired decelera-tion.DISCUSSIONAutobrake deceleration rates can be displayed as in-dexed numbers on a flight deck selector control. These numbersnormally relate to fixed levels of deceleration that the aircraft as awhole is pr
25、ogrammed to achieve. It is important not to confuse thesedeceleration rate values with runway friction values.average braking coefficient, na braking coefficient numberrepresenting the average of all recorded values over a giventime, distance, or change in groundspeed.braking action, na means of des
26、cribing the maximumcapability of a vehicles braking system on a wet orcontaminated surface that references a standardized report-ing scale.DISCUSSION“Maximum capability” and “friction limited” are usedinterchangeably here. The term “capability” is used to referencesubjective human observations, whil
27、e the term “friction limited” is usedas an engineering term. AC 150/5200-30D and AC 91-79A provide arelation between the descriptors and human observation, while AC25-32 provides a relation between the descriptors and wheel brakingcoefficients. An example of the human observations is given below.Bra
28、king Action Deceleration or Direction Control ObservationGood Braking deceleration is normal for the wheelbraking effort applied AND directional control isnormalGood to Medium Braking deceleration OR directional control isbetween Good and MediumMedium Braking deceleration is noticeably reduced forth
29、e wheel braking effort applied, OR directionalcontrol is noticeably reducedMedium to Poor Braking deceleration OR directional control isbetween Medium and PoorPoor Braking deceleration is significantly reduced forthe wheel braking effort applied, OR directioncontrol is significantly reducedNil Braki
30、ng deceleration is minimal to non-existentfor the wheel braking effort applied, ORdirectional control is uncertainDISCUSSIONAC 91-79A and other related FAA guidance referringbraking observation guidance uses the terms “normal” and “reduced”braking in a specific context. In this case, “normal” is a l
31、evel of brakingaction associated with a wet surface that meets established standards forrunway friction maintenance. Under “normal” conditions, pilot controlinput would be supported by the relatively substantial directional anddeceleration responses expected under standard wet runway conditions.“Red
32、uced” braking occurs when deceleration and directional control isless than “normal.” This level of braking most often occurs when therunway surface is contaminated or when the surface cannot supportnormal wet friction standards. “Reduced” braking is then articulatedthrough the series of terms that d
33、escribe braking of a lower value than“good.”DISCUSSIONIt is important to note here how the philosophy of theNOTAM system intersects with that of the braking report. The NOTAMsystem is designed to only report non-normal conditions which, in thiscase, means a runway that is other than dry. This has th
34、e effect ofcreating three large classifications of braking action: dry (usually notreported), “good” for standard wet runways, followed by a series ofclassifications pertaining to “reduced” braking (medium, medium topoor, etc.).friction-limited braking, na condition of aircraft grounddeceleration pe
35、rformance where the amount of decelerationforce that can be applied by the aircraft brakes is limited bythe friction level of the runway surface. Any increase incommand to the brake system will be limited by the anti-skidsystem.friction-limited (aircraft/wheel) braking coefficient, nabraking coeffic
36、ient measured during conditions of friction-limited braking.DISCUSSIONStandardized reporting scales such as those found inAC 25-32 reference wheel braking coefficients. It is understood thatthese values represent friction-limited braking and, as such, define theboundaries of the reporting scale refe
37、renced. When used in this manner,these values are used to calculate data that define an operational limitfor an aircraft.maximum aircraft wheel braking performance, nanymeasurement that quantifies the highest limiting value of awheel braking system under a given condition (good,medium, poor, etc.).D
38、ISCUSSIONThe customary language for describing wheel brakingperformance uses the “braking coefficient” value as a standard metric.Future technologies, however, may in fact use new forms of data andmeasuring devices to describe braking performance. Additionally,observations such as pilot braking repo
39、rts rely on subjective criteria andare not dependent on coefficient analysis. The term therefore serves todescribe an intended function of any process that achieves the result asdefined above.E3188 192maximum tire-to-ground braking coefficient, nthe highestamount of wheel braking achievable for a gi
40、ven set ofconditions over a range of slip ratios (0 to 1).DISCUSSIONFAR 25.109 uses the term “maximum tire-to-groundwet runway braking coefficient of friction.” This term is specific to thisFAR and references specific conditions regarding runway type, tirepressure, and ground speed as well as specif
41、ic formulas.mu slip curve, na graphical plot using the tire-to-groundfriction coefficient in the y-axis and the slip ratio in thex-axis. These graphs display the relationship between slipand friction for a given surface. It can be used to display thecharacteristics of certain surfaces, as well as to
42、 show thedesigned function of an anti-skid system in regulating thebrake pressure (and thus the slip ratio) to achieve themaximum tire-to-ground friction coefficient without lettingthe wheel lock up into a skid.observed wheel braking coefficient, na wheel brakingcoefficient value that results from a
43、n actual event.DISCUSSIONPost-incident analysis done by an investigative agencytaken from recorded flight data would represent an observed brakingcoefficient.pilot braking action report, PIREP, AIREP, na reportdescribing a level of braking action resulting from theobservations of a pilot.DISCUSSIONT
44、he “deceleration or directional control observation”guidance such as that found in AC 91-79A is used to as an observationguide. In cases where braking reports are requested but no observationof maximum braking was observed, the phrase “braking not observed”should be used.SCAP, nacronym for Standardi
45、zed Computerized AircraftPerformance; an industry standard developed by IATA,ATA,and several manufacturers for interfacing computer pro-gramming input/output features related to aircraft perfor-mance.DISCUSSIONThere are six (6) SCAP specifications: (1) takeoff, (2)landing, (3) climb-out, (4) infligh
46、t, (5) noise, and (6) APM (aircraftperformance monitoring). SCAP specifications are applicable to civil,transport category airplanes.slip ratio, nthe ratio between the speed of a rotating wheeland the speed of a vehicle.DISCUSSIONAs more force is applied by the brakes, the angularvelocity of the whe
47、el slows down with respect to the absolute velocityof the wheel axle. It is this difference in speed that is called “slip.” Africtional force is then created when the two bodies slide against eachother. A slip ratio of 0 implies that the wheel is free rolling (no brakingapplied.) A slip ratio of 1 i
48、mplies that the wheel is locked (not turning)but the wheel axle is still moving forward. The slip ratio can be definedby:s 5Vx2 RRVxwhere:s = slip ratio (non-dimensional),Vx= velocity of the wheel axle, = angular velocity of the wheel, andRR= rolling radius of the wheel.time-varying braking coeffici
49、ent, na braking coefficient,whether it be wheel braking coefficient or aircraft brakingcoefficient, that varies over time with respect to the inputsrequired for its calculation.tire-to-ground friction coefficient, nthe non-dimensionalnumber determined by dividing the decelerating force of aspecific tire by the vertical load on that tire.DISCUSSIONThe value is usually less than 1.0 and will vary inmagnitude due to factors that may include:(1) Tire tread condition (new versus worn),(2) Tire inflation pressure,(3) Tire construction (bias vers
