Part 25: Airworthiness Standards: Transport Category Part 25ASA 125PART 25AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANESSPECIAL FEDERAL AVIATION REGULATIONSSFAR No. 13SFAR No. 109Subpart AGeneralSec.25.1 Applicability.25.2 Special retroactive requirements.25.3 Special provisions for ETOPS type design approvals.25.5 Incorporations by reference.Subpart BFlightGENERAL25.21 Proof of compliance.25.23 Load distribution limits.25.25 Weight limits.25.27 Center of gravity limits.25.29 Empty weight and corresponding center of gravity.25.31 Removable ballast.25.33 Propeller speed and pitch limits.PERFORMANCE25.101 General.25.103 Stall speed.25.105 Takeoff.25.107 Takeoff speeds.25.109 Accelerate-stop distance.25.111 Takeoff path.25.113 Takeoff distance and takeoff run.25.115 Takeoff ight path.25.117 Climb: general.25.119 Landing climb: All-engines-operating.25.121 Climb: One-engine-inoperative.25.123 En route ight paths.25.125 Landing.CONTROLLABILITY AND MANEUVERABILITY25.143 General.25.145 Longitudinal control.25.147 Directional and lateral control.25.149 Minimum control speed.TRIM25.161 Trim.STABILITY25.171 General.25.173 Static longitudinal stability.25.175 Demonstration of static longitudinal stability.25.177 Static lateral-directional stability.25.181 Dynamic stability.STALLS25.201 Stall demonstration.25.203 Stall characteristics.25.207 Stall warning.GROUND AND WATER HANDLINGCHARACTERISTICS25.231 Longitudinal stability and control.25.233 Directional stability and control.25.235 Taxiing condition.25.237 Wind velocities.25.239 Spray characteristics, control, and stability on water.MISCELLANEOUS FLIGHT REQUIREMENTS25.251 Vibration and buffeting.25.253 High-speed characteristics.25.255 Out-of-trim characteristics.Subpart CStructureGENERAL25.301 Loads.25.303 Factor of safety.25.305 Strength and deformation.25.307 Proof of structure.FLIGHT LOADS25.321 General.FLIGHT MANEUVER AND GUST CONDITIONS25.331 Symmetric maneuvering conditions.25.333 Flight maneuvering envelope.25.335 Design airspeeds.25.337 Limit maneuvering load factors.25.341 Gust and turbulence loads.25.343 Design fuel and oil loads.25.345 High lift devices.25.349 Rolling conditions.25.351 Yaw maneuver conditions.SUPPLEMENTARY CONDITIONS25.361 Engine torque.25.363 Side load on engine and auxiliary power unit mounts.25.365 Pressurized compartment loads.25.367 Unsymmetrical loads due to engine failure.25.371 Gyroscopic loads.25.373 Speed control devices.Part 25 Federal Aviation Regulations2 ASACONTROL SURFACE AND SYSTEM LOADS25.391 Control surface loads: general.25.393 Loads parallel to hinge line.25.395 Control system.25.397 Control system loads.25.399 Dual control system.25.405 Secondary control system.25.407 Trim tab effects.25.409 Tabs.25.415 Ground gust conditions.25.427 Unsymmetrical loads.25.445 Auxiliary aerodynamic surfaces.25.457 Wing aps.25.459 Special devices.GROUND LOADS25.471 General.25.473 Landing load conditions and assumptions.25.477 Landing gear arrangement.25.479 Level landing conditions.25.481 Tail-down landing conditions.25.483 One-gear landing conditions.25.485 Side load conditions.25.487 Rebound landing condition.25.489 Ground handling conditions.25.491 Taxi, takeoff and landing roll.25.493 Braked roll conditions.25.495 Turning.25.497 Tail-wheel yawing.25.499 Nose-wheel yaw and steering.25.503 Pivoting.25.507 Reversed braking.25.509 Towing loads.25.511 Ground load: unsymmetrical loads on multiple-wheel units.25.519 Jacking and tie-down provisions.WATER LOADS25.521 General.25.523 Design weights and center of gravity positions.25.525 Application of loads.25.527 Hull and main oat load factors.25.529 Hull and main oat landing conditions.25.531 Hull and main oat takeoff condition.25.533 Hull and main oat bottom pressures.25.535 Auxiliary oat loads.25.537 Seawing loads.EMERGENCY LANDING CONDITIONS25.561 General.25.562 Emergency landing dynamic conditions.25.563 Structural ditching provisions.FATIGUE EVALUATION25.571 Damage-tolerance and fatigue evaluation of structure.LIGHTNING PROTECTION25.581 Lightning protection.Subpart DDesign and ConstructionGENERAL25.601 General.25.603 Materials.25.605 Fabrication methods.25.607 Fasteners.25.609 Protection of structure.25.611 Accessibility provisions.25.613 Material strength properties and material design values.25.619 Special factors.25.621 Casting factors.25.623 Bearing factors.25.625 Fitting factors.25.629 Aeroelastic stability requirements.25.631 Bird strike damage.CONTROL SURFACES25.651 Proof of strength.25.655 Installation.25.657 Hinges.CONTROL SYSTEMS25.671 General.25.672 Stability augmentation and automatic and power-operated systems.25.675 Stops.25.677 Trim systems.25.679 Control system gust locks.25.681 Limit load static tests.25.683 Operation tests.25.685 Control system details.25.689 Cable systems.25.693 Joints.25.697 Lift and drag devices, controls.25.699 Lift and drag device indicator.25.701 Flap and slat interconnection.25.703 Takeoff warning system.LANDING GEAR25.721 General.25.723 Shock absorption tests.25.725 [Reserved]25.727 [Reserved]25.729 Retracting mechanism.25.731 Wheels.25.733 Tires.25.735 Brakes and braking systems.25.737 Skis.Part 25: Airworthiness Standards: Transport Category Part 25ASA 325FLOATS AND HULLS25.751 Main oat buoyancy.25.753 Main oat design.25.755 Hulls.PERSONNEL AND CARGO ACCOMMODATIONS25.771 Pilot compartment.25.772 Pilot compartment doors.25.773 Pilot compartment view.25.775 Windshields and windows.25.777 Cockpit controls.25.779 Motion and effect of cockpit controls.25.781 Cockpit control knob shape.25.783 Fuselage doors.25.785 Seats, berths, safety belts, and harnesses.25.787 Stowage compartments.25.789 Retention of items of mass in passenger and crew compartments and galleys.25.791 Passenger information signs and placards.25.793 Floor surfaces.25.795 Security considerations.EMERGENCY PROVISIONS25.801 Ditching.25.803 Emergency evacuation.25.807 Emergency exits.25.809 Emergency exit arrangement.25.810 Emergency egress assist means and escape routes.25.811 Emergency exit marking.25.812 Emergency lighting.25.813 Emergency exit access.25.815 Width of aisle.25.817 Maximum number of seats abreast.25.819 Lower deck surface compartments (including galleys).25.820 Lavatory doors.VENTILATION AND HEATING25.831 Ventilation.25.832 Cabin ozone concentration.25.833 Combustion heating systems.PRESSURIZATION25.841 Pressurized cabins.25.843 Tests for pressurized cabins.FIRE PROTECTION25.851 Fire extinguishers.25.853 Compartment interiors.25.854 Lavatory re protection.25.855 Cargo or baggage compartments.25.856 Thermal/Acoustic insulation materials.25.857 Cargo compartment classication.25.858 Cargo or baggage compartment smoke or re detection systems.25.859 Combustion heater re protection.25.863 Flammable uid re protection.25.865 Fire protection of ight controls, engine mounts, and other ight structure.25.867 Fire protection: other components.25.869 Fire protection: systems.MISCELLANEOUS25.871 Leveling means.25.875 Reinforcement near propellers.25.899 Electrical bonding and protection against static electricity.Subpart EPowerplantGENERAL25.901 Installation.25.903 Engines.25.904 Automatic takeoff thrust control system (ATTCS).25.905 Propellers.25.907 Propeller vibration and fatigue.25.925 Propeller clearance.25.929 Propeller deicing.25.933 Reversing systems.25.934 Turbojet engine thrust reverser system tests.25.937 Turbopropeller-drag limiting systems.25.939 Turbine engine operating characteristics.25.941 Inlet, engine, and exhaust compatibility.25.943 Negative acceleration.25.945 Thrust or power augmentation system.FUEL SYSTEM25.951 General.25.952 Fuel system analysis and test.25.953 Fuel system independence.25.954 Fuel system lightning protection.25.955 Fuel ow.25.957 Flow between interconnected tanks.25.959 Unusable fuel supply.25.961 Fuel system hot weather operation.25.963 Fuel tanks: general.25.965 Fuel tank tests.25.967 Fuel tank installations.25.969 Fuel tank expansion space.25.971 Fuel tank sump.25.973 Fuel tank ller connection.25.975 Fuel tank vents and carburetor vapor vents.25.977 Fuel tank outlet.25.979 Pressure fueling system.25.981 Fuel tank explosion prevention.FUEL SYSTEM COMPONENTS25.991 Fuel pumps.25.993 Fuel system lines and ttings.25.994 Fuel system components.25.995 Fuel valves.Part 25 Federal Aviation Regulations4 ASA25.997 Fuel strainer or lter.25.999 Fuel system drains.25.1001 Fuel jettisoning system.OIL SYSTEM25.1011 General.25.1013 Oil tanks.25.1015 Oil tank tests.25.1017 Oil lines and ttings.25.1019 Oil strainer or lter.25.1021 Oil system drains.25.1023 Oil radiators.25.1025 Oil valves.25.1027 Propeller feathering system.COOLING25.1041 General.25.1043 Cooling tests.25.1045 Cooling test procedures.INDUCTION SYSTEM25.1091 Air induction.25.1093 Induction system icing protection.25.1101 Carburetor air preheater design.25.1103 Induction system ducts and air duct systems.25.1105 Induction system screens.25.1107 Inter-coolers and after-coolers.EXHAUST SYSTEM25.1121 General.25.1123 Exhaust piping.25.1125 Exhaust heat exchangers.25.1127 Exhaust driven turbo-superchargers.POWERPLANT CONTROLS AND ACCESSORIES25.1141 Powerplant controls: general.25.1142 Auxiliary power unit controls.25.1143 Engine controls.25.1145 Ignition switches.25.1147 Mixture controls.25.1149 Propeller speed and pitch controls.25.1153 Propeller feathering controls.25.1155 Reverse thrust and propeller pitch settings below the ight regime.25.1157 Carburetor air temperature controls.25.1159 Supercharger controls.25.1161 Fuel jettisoning system controls.25.1163 Powerplant accessories.25.1165 Engine ignition systems.25.1167 Accessory gearboxes.POWERPLANT FIRE PROTECTION25.1181 Designated re zones; regions included.25.1182 Nacelle areas behind rewalls, and engine pod attaching structures containing ammable uid lines.25.1183 Flammable uid-carrying components.25.1185 Flammable uids.25.1187 Drainage and ventilation of re zones.25.1189 Shutoff means.25.1191 Firewalls.25.1192 Engine accessory section diaphragm.25.1193 Cowling and nacelle skin.25.1195 Fire extinguishing systems.25.1197 Fire extinguishing agents.25.1199 Extinguishing agent containers.25.1201 Fire extinguishing system materials.25.1203 Fire detector system.25.1207 Compliance.Subpart FEquipmentGENERAL25.1301 Function and installation.25.1303 Flight and navigation instruments.25.1305 Powerplant instruments.25.1307 Miscellaneous equipment.25.1309 Equipment, systems, and installations.25.1310 Power source capacity and distribution.25.1316 System lightning protection.25.1317 High-Intensity Radiated Fields (HIRF) Protection.INSTRUMENTS: INSTALLATION25.1321 Arrangement and visibility.25.1322 Warning, caution, and advisory lights.25.1323 Airspeed indicating system.25.1325 Static pressure systems.25.1326 Pitot heat indication systems.25.1327 Magnetic direction indicator.25.1329 Flight guidance system.25.1331 Instruments using a power supply.25.1333 Instrument systems.25.1335 Flight director systems.25.1337 Powerplant instruments.ELECTRICAL SYSTEMS AND EQUIPMENT25.1351 General.25.1353 Electrical equipment and installations.25.1355 Distribution system.25.1357 Circuit protective devices.25.1360 Precautions against injury.25.1362 Electrical supplies for emergency conditions.25.1363 Electrical system tests.25.1365 Electrical appliances, motors, and transformers.LIGHTS25.1381 Instrument lights.25.1383 Landing lights.25.1385 Position light system installation.25.1387 Position light system dihedral angles.25.1389 Position light distribution and intensities.Part 25: Airworthiness Standards: Transport Category Part 25ASA 52525.1391 Minimum intensities in the horizontal plane of forward and rear position lights.25.1393 Minimum intensities in any vertical plane of forward and rear position lights.25.1395 Maximum intensities in overlapping beams of forward and rear position lights.25.1397 Color specications.25.1399 Riding light.25.1401 Anticollision light system.25.1403 Wing icing detection lights.SAFETY EQUIPMENT25.1411 General.25.1415 Ditching equipment.25.1419 Ice protection.25.1421 Megaphones.25.1423 Public address system.MISCELLANEOUS EQUIPMENT25.1431 Electronic equipment.25.1433 Vacuum systems.25.1435 Hydraulic systems.25.1438 Pressurization and pneumatic systems.25.1439 Protective breathing equipment.25.1441 Oxygen equipment and supply.25.1443 Minimum mass ow of supplemental oxygen.25.1445 Equipment standards for the oxygen distributing system.25.1447 Equipment standards for oxygen dispensing units.25.1449 Means for determining use of oxygen.25.1450 Chemical oxygen generators.25.1453 Protection of oxygen equipment from rupture.25.1455 Draining of uids subject to freezing.25.1457 Cockpit voice recorders.25.1459 Flight data recorders.25.1461 Equipment containing high energy rotors.Subpart GOperating Limitations and Information25.1501 General.OPERATING LIMITATIONS25.1503 Airspeed limitations: general.25.1505 Maximum operating limit speed.25.1507 Maneuvering speed.25.1511 Flap extended speed.25.1513 Minimum control speed.25.1515 Landing gear speeds.25.1516 Other speed limitations.25.1517 Rough air speed, VRA.25.1519 Weight, center of gravity, and weight distribution.25.1521 Powerplant limitations.25.1522 Auxiliary power unit limitations.25.1523 Minimum ight crew.25.1525 Kinds of operation.25.1527 Ambient air temperature and operating altitude.25.1529 Instructions for Continued Airworthiness.25.1531 Maneuvering ight load factors.25.1533 Additional operating limitations.25.1535 ETOPS approval.MARKINGS AND PLACARDS25.1541 General.25.1543 Instrument markings: general.25.1545 Airspeed limitation information.25.1547 Magnetic direction indicator.25.1549 Powerplant and auxiliary power unit instruments.25.1551 Oil quantity indication.25.1553 Fuel quantity indicator.25.1555 Control markings.25.1557 Miscellaneous markings and placards.25.1561 Safety equipment.25.1563 Airspeed placard.AIRPLANE FLIGHT MANUAL25.1581 General.25.1583 Operating limitations.25.1585 Operating procedures.25.1587 Performance information.Subpart HElectrical Wiring Interconnection Systems (EWIS)25.1701 Denition.25.1703 Function and installation: EWIS.25.1705 Systems and functions: EWIS.25.1707 System separation: EWIS.25.1709 System safety: EWIS.25.1711 Component identication: EWIS.25.1713 Fire protection: EWIS.25.1715 Electrical bonding and protection against static electricity: EWIS.25.1717 Circuit protective devices: EWIS.25.1719 Accessibility provisions: EWIS.25.1721 Protection of EWIS.25.1723 Flammable uid re protection: EWIS.25.1725 Powerplants: EWIS.25.1727 Flammable uid shutoff means: EWIS.25.1729 Instructions for Continued Airworthiness: EWIS.25.1731 Powerplant and APU re detector system: EWIS.25.1733 Fire detector systems, general: EWIS.SFAR No. 13 to Part 25 Federal Aviation Regulations6 ASAAPPENDICES TO PART 25Appendix A to Part 25Appendix B to Part 25Appendix C to Part 25Appendix D to Part 25Appendix E to Part 25Appendix F to Part 25Appendix G to Part 25 Continuous Gust Design CriteriaAppendix H to Part 25 Instructions for Continued AirworthinessAppendix I to Part 25 Installation of an Automatic Takeoff Thrust Control System (ATTCS)Appendix J to Part 25 Emergency EvacuationAppendix K to Part 25Extended Operations (ETOPS)Appendix L to Part 25HIRF Environments and Equipment HIRF Test LevelsAppendix M to Part 25Fuel Tank System Flammability Reduction MeansAppendix N to Part 25Fuel Tank Flammability Exposure and Reliability AnalysisAuthority: 49 U.S.C 106(g), 40113, 44701, 44702 and44704.Source: Docket No. 5066, 29 FR 18291, Dec. 24, 1964,unless otherwise noted.SFAR NO. 13 TO PART 251. Applicability. Contrary provisions of the CivilAir Regulations regarding certication notwith-standing,1this regulation shall provide the basisfor approval by the Administrator of modicationsof individual Douglas DC-3 and Lockheed L-18airplanes subsequent to the effective date of thisregulation.1It is not intended to waive compliance with suchairworthiness requirements as are included in theoperating parts of the Civil Air Regulations forspecic types of operation.2. General modications. Except as modied insections 3 and 4 of this regulation, an applicantfor approval of modications to a DC-3 or L-18 air-plane which result in changes in design or inchanges to approved limitations shall show thatthe modications were accomplished in accor-dance with the rules of either Part 4a or Part 4b ineffect on September 1, 1953, which are applica-ble to the modication being made: Provided,That an applicant may elect to accomplish a mod-ication in accordance with the rules of Part 4b ineffect on the date of application for the modica-tion in lieu of Part 4a or Part 4b as in effect onSeptember 1, 1953: And provided further, Thateach specic modication must be accomplishedin accordance with all of the provisions containedin the elected rules relating to the particular modi-cation.3. Specic conditions for approval. An appli-cant for any approval of the following specicchanges shall comply with section 2 of this regu-lation as modied by the applicable provisions ofthis section.(a) Increase in take-off power limitation1,200to 1,350 horsepower. The engine take-off powerlimitation for the airplane may be increased tomore than 1,200 horsepower but not to more than1,350 horsepower per engine if the increase inpower does not adversely affect the ight charac-teristics of the airplane.(b) Increase in take-off power limitation to morethan 1,350 horsepower. The engine take-offpower limitation for the airplane may be increasedto more than 1,350 horsepower per engine if com-pliance is shown with the ight characteristics andground handling requirements of Part 4b.(c) Installation of engines of not more than1,830 cubic inches displacement and not having acerticated take-off rating of more than 1,350horsepower. Engines of not more than 1,830 cu-bic inches displacement and not having a certi-cated take-off rating of more than 1,350 horse-power which necessitate a major modication ofredesign of the engine installation may be in-stalled, if the engine re prevention and re pro-tection are equivalent to that on the prior engineinstallation.(d) Installation of engines of more than 1,830cubic inches displacement or having certicatedtake-off rating of more than 1,350 horsepower.Engines of more than 1,830 cubic inches dis-placement or having certicated take-off rating ofmore than 1,350 horsepower may be installed ifcompliance is shown with the engine installationrequirements of Part 4b: Provided, That where lit-eral compliance with the engine installation re-quirements of Part 4b is extremely difcult to ac-complish and would not contribute materially tothe objective sought, and the Administrator ndsthat the experience with the DC-3 or L-18 air-planes justies it, he is authorized to accept suchmeasures of compliance as he nds will effec-tively accomplish the basic objective.4. Establishment of new maximum certicatedweights. An applicant for approval of new maxi-mum certicated weights shall apply for anamendment of the airworthiness certicate of theairplane and shall show that the weights soughthave been established, and the appropriate man-ual material obtained, as provided in this section.Part 25: Airworthiness Standards: Transport Category SFAR No. 109 to Part 25ASA 725Note: Transport category performance require-ments result in the establishment of maximumcerticated weights for various altitudes.(a) Weights 25,200 to 26,900 for the DC-3and 18,500 to 19,500 for the L-18. New maximumcerticated weights of more than 25,200 but notmore than 26,900 pounds for DC-3 and more than18,500 but not more than 19,500 pounds for L-18airplanes may be established in accordance withthe transport category performance requirementsof either Part 4a or Part 4b, if the airplane at thenew maximum weights can meet the structural re-quirements of the elected part.(b) Weights of more than 26,900 for the DC-3and 19,500 for the L-18. New maximum certi-cated weights of more than 26,900 pounds forDC-3 and 19,500 pounds for L-18 airplanes shallbe established in accordance with the structuralperformance, ight characteristics, and groundhandling requirements of Part 4b: Provided, Thatwhere literal compliance with the structural re-quirements of Part 4b is extremely difcult to ac-complish and would not contribute materially tothe objective sought, and the Administrator ndsthat the experience with the DC-3 or L-18 air-planes justies it, he is authorized to accept suchmeasures of compliance as he nds will effec-tively accomplish the basic objective.(c) Airplane ight manual-performance operat-ing information. An approved airplane ight man-ual shall be provided for each DC-3 and L-18 air-plane which has had new maximum certicatedweights established under this section. The air-plane ight manual shall contain the applicableperformance information prescribed in that part ofthe regulations under which the new certicatedweights were established and such additional in-formation as may be necessary to enable the ap-plication of the take-off, en route, and landing lim-itations prescribed for transport category air-planes in the operating parts of the Civil AirRegulations.(d) Performance operating limitations. Each air-plane for which new maximum certicated weightsare established in accordance with paragraphs (a)or (b) of this section shall be considered a trans-port category airplane for the purpose of comply-ing with the performance operating limitations ap-plicable to the operations in which it is utilized.5. Reference. Unless otherwise provided, allreferences in this regulation to Part 4a and Part4b are those parts of the Civil Air Regulations ineffect on September 1, 1953.This regulation supersedes Special Civil AirRegulation SR-398 and shall remain effective un-til superseded or rescinded by the Board.[19 FR 5039, Aug. 11, 1954. Redesignated at 29 FR19099, Dec. 30, 1964]SFAR NO. 109 TO PART 251. Applicability. Contrary provisions of 14CFR parts 21, 25, and 119 of this chapter notwith-standing, an applicant is entitled to an amendedtype certicate or supplemental type certicate inthe transport category, if the applicant complieswith all applicable provisions of this SFAR.OPERATIONS2. General.(a) The passenger capacity may not exceed 60.If more than 60 passenger seats are installed,then:(1) If the extra seats are not suitable for occu-pancy during taxi, takeoff and landing, each extraseat must be clearly marked (e.g., a placard onthe top of an armrest, or a placard sewn into thetop of the back cushion) that the seat is not to beoccupied during taxi, takeoff and landing.(2) If the extra seats are suitable for occupancyduring taxi, takeoff and landing (i.e., meet all thestrength and passenger injury criteria in part 25),then a note must be included in the LimitationsSection of the Airplane Flight Manual that thereare extra seats installed but that the number ofpassengers on the airplane must not exceed 60.Additionally, there must be a placard installed ad-jacent to each door that can be used as a passen-ger boarding door that states that the maximumpassenger capacity is 60. The placard must beclearly legible to passengers entering the air-plane.(b) For airplanes outtted with interior doorsunder paragraph 10 of this SFAR, the airplaneight manual (AFM) must include an appropriatelimitation that the airplane must be staffed with atleast the following number of ight attendants whomeet the requirements of 14 CFR 91.533(b):(1) The number of ight attendants required by91.533(a)(1) and (2) of this chapter, and(2) At least one ight attendant if the airplanemodel was originally certied for 75 passengersor more.(c) The AFM must include appropriate limita-tion(s) to require a preight passenger briengdescribing the appropriate functions to be per-formed by the passengers and the relevant fea-tures of the airplane to ensure the safety of thepassengers and crew.(d) The airplane may not be offered for com-mon carriage or operated for hire. The operatinglimitations section of the AFM must be revised toprohibit any operations involving the carriage ofpersons or property for compensation or hire. Theoperators may receive remuneration to the extentconsistent with parts 125 and 91, subpart F, ofthis chapter.(e) A placard stating that Operations involvingthe carriage of persons or property for compensa-SFAR No. 109 to Part 25 Federal Aviation Regulations8 ASAtion or hire are prohibited, must be located in thearea of the Airworthiness Certicate holder at theentrance to the ightdeck.(f) For passenger capacities of 45 to 60 pas-sengers, analysis must be submitted that demon-strates that the airplane can be evacuated in lessthan 90 seconds under the conditions specied in25.803 and Appendix J to part 25.(g) In order for any airplane certied under thisSFAR to be placed in part 135 or part 121 opera-tions, the airplane must be brought back into fullcompliance with the applicable operational part.EQUIPMENT AND DESIGN3. General. Unless otherwise noted, compli-ance is required with the applicable certicationbasis for the airplane. Some provisions of thisSFAR impose alternative requirements to certainairworthiness standards that do not apply to air-planes certicated to earlier standards. Those air-planes with an earlier certication basis are notrequired to comply with those alternative require-ments.4. Occupant Protection.(a) Firm Handhold. In lieu of the requirementsof 25.785(j), there must be means provided toenable persons to steady themselves in moder-ately rough air while occupying aisles that arealong the cabin sidewall, or where practicable,bordered by seats (seat backs providing a 25-pound minimum breakaway force are an accept-able means of compliance).(b) Injury criteria for multiple occupancy side-facing seats. The following requirements are onlyapplicable to airplanes that are subject to25.562.(1) Existing Criteria. All injury protection criteriaof 25.562(c)(1) through (c)(6) apply to the occu-pants of side-facing seating. The Head Injury Cri-terion (HIC) assessments are only required forhead contact with the seat and/or adjacent struc-tures.(2) Body-to-Body Contact. Contact betweenthe head, pelvis, torso or shoulder area of one An-thropomorphic Test Dummy (ATD) with the head,pelvis, torso or shoulder area of the ATD in the ad-jacent seat is not allowed during the tests con-ducted in accordance with 25.562(b)(1) and(b)(2). Contact during rebound is allowed.(3) Thoracic Trauma. If the torso of an ATD atthe forward-most seat place impacts the seatand/or adjacent structure during testing, compli-ance with the Thoracic Trauma Index (TTI) injurycriterion must be substantiated by dynamic test orby rational analysis based on previous test(s) of asimilar seat installation. TTI data must be ac-quired with a Side Impact Dummy (SID), as de-ned by 49 CFR part 572, subpart F, or an equiv-alent ATD or a more appropriate ATD and must beprocessed as dened in Federal Motor VehicleSafety Standards (FMVSS) part 571.214, sectionS6.13.5 (49 CFR 571.214). The TTI must be lessthan 85, as dened in 49 CFR part 572, subpart F.Torso contact during rebound is acceptable andneed not be measured.(4) Pelvis. If the pelvis of an ATD at any seatplace impacts seat and/or adjacent structure dur-ing testing, pelvic lateral acceleration injury crite-ria must be substantiated by dynamic test or byrational analysis based on previous test(s) of asimilar seat installation. Pelvic lateral accelerationmay not exceed 130g. Pelvic acceleration datamust be processed as dened in FMVSS part571.214, section S6.13.5 (49 CFR 571.214).(5) Body-to-Wall/Furnishing Contact. If the seatis installed aft of a structuresuch as an interiorwall or furnishing that may contact the pelvis, up-per arm, chest, or head of an occupant seatednext to the structurethe structure or a conserva-tive representation of the structure and its stiff-ness must be included in the tests. It is recom-mended, but not required, that the contact surfaceof the actual structure be covered with at least twoinches of energy absorbing protective padding(foam or equivalent) such as Ensolite.(6) Shoulder Strap Loads. Where upper torsostraps (shoulder straps) are used for sofa occu-pants, the tension loads in individual straps maynot exceed 1,750 pounds. If dual straps are usedfor restraining the upper torso, the total strap ten-sion loads may not exceed 2,000 pounds.(7) Occupant Retention. All side-facing seatsrequire end closures or other means to preventthe ATDs pelvis from translating beyond the endof the seat at any time during testing.(8) Test Parameters.(i) All seat positions need to be occupied byATDs for the longitudinal tests.(ii) A minimum of one longitudinal test, con-ducted in accordance with the conditions speci-ed in 25.562(b)(2), is required to assess the in-jury criteria as follows. Note that if a seat is in-stalled aft of structure (such as an interior wall orfurnishing) that does not have a homogeneoussurface, an additional test or tests may be re-quired to demonstrate that the injury criteria aremet for the area which an occupant could contact.For example, different yaw angles could result indifferent injury considerations and may requireseparate tests to evaluate.(A) For congurations without structure (suchas a wall or bulkhead) installed directly forward ofthe forward seat place, Hybrid II ATDs or equiva-lent must be in all seat places.(B) For congurations with structure (such as awall or bulkhead) installed directly forward of theforward seat place, a side impact dummy orequivalent ATD or more appropriate ATD must bePart 25: Airworthiness Standards: Transport Category SFAR No. 109 to Part 25ASA 925in the forward seat place and a Hybrid II ATD orequivalent must be in all other seat places.(C) The test may be conducted with or withoutdeformed oor.(D) The test must be conducted with either noyaw or 10 degrees yaw for evaluating occupant in-jury. Deviating from the no yaw condition may notresult in the critical area of contact not being eval-uated. The upper torso restraint straps, where in-stalled, must remain on the occupants shoulderduring the impact condition of 25.562(b)(2).(c) For the vertical test, conducted in accor-dance with the conditions specied in25.562(b)(1), Hybrid II ATDs or equivalent mustbe used in all seat positions.5. Direct View. In lieu of the requirements of25.785(h)(2), to the extent practical without com-promising proximity to a required oor level emer-gency exit, the majority of installed ight attendantseats must be located to face the cabin area forwhich the ight attendant is responsible.6. Passenger Information Signs. Compliancewith 25.791 is required except that for25.791(a), when smoking is to be prohibited, no-tication to the passengers may be provided by asingle placard so stating, to be conspicuously lo-cated inside the passenger compartment, easilyvisible to all persons entering the cabin in the im-mediate vicinity of each passenger entry door.7. Distance Between Exits. For an airplanethat is required to comply with 25.807(f)(4), in ef-fect as of July 24, 1989, which has more than onepassenger emergency exit on each side of the fu-selage, no passenger emergency exit may bemore than 60 feet from any adjacent passengeremergency exit on the same side of the samedeck of the fuselage, as measured parallel to theairplanes longitudinal axis between the nearestexit edges, unless the following conditions aremet:(a) Each passenger seat must be locatedwithin 30 feet from the nearest exit on each sideof the fuselage, as measured parallel to the air-planes longitudinal axis, between the nearest exitedge and the front of the seat bottom cushion.(b) The number of passenger seats located be-tween two adjacent pairs of emergency exits(commonly referred to as a passenger zone) orbetween a pair of exits and a bulkhead or a com-partment door (commonly referred to as a dead-end zone), may not exceed the following:(1) For zones between two pairs of exits, 50percent of the combined rated capacity of the twopairs of emergency exits.(2) For zones between one pair of exits and abulkhead, 40 percent of the rated capacity of thepair of emergency exits.(c) The total number of passenger seats in theairplane may not exceed 33 percent of the maxi-mum seating capacity for the airplane model us-ing the exit ratings listed in 25.807(g) for theoriginal certied exits or the maximum allowableafter modication when exits are deactivated,whichever is less.(d) A distance of more than 60 feet betweenadjacent passenger emergency exits on the sameside of the same deck of the fuselage, as mea-sured parallel to the airplanes longitudinal axisbetween the nearest exit edges, is allowed onlyonce on each side of the fuselage.8. Emergency Exit Signs. In lieu of the re-quirements of 25.811(d)(1) and (2) a single signat each exit may be installed provided:(a) The sign can be read from the aisle while di-rectly facing the exit, and(b) The sign can be read from the aisle adja-cent to the passenger seat that is farthest fromthe exit and that does not have an interveningbulkhead/divider or exit.9. Emergency Lighting.(a) Exit Signs. In lieu of the requirements of25.812(b)(1), for airplanes that have a passen-ger seating conguration, excluding pilot seats, of19 seats or less, the emergency exit signs re-quired by 25.811(d)(1), (2), and (3) must havered letters at least 1-inch high on a white back-ground at least 2 inches high. These signs may beinternally electrically illuminated, or self illumi-nated by other than electrical means, with an ini-tial brightness of at least 160 microlamberts. Thecolor may be reversed in the case of a sign that isself-illuminated by other than electrical means.(b) Floor Proximity Escape Path Marking. Inlieu of the requirements of 25.812(e)(1), forcabin seating compartments that do not have themain cabin aisle entering and exiting the compart-ment, the following are applicable:(1) After a passenger leaves any passengerseat in the compartment, he/she must be able toexit the compartment to the main cabin aisle us-ing only markings and visual features not morethat 4 feet above the cabin oor, and(2) Proceed to the exits using the marking sys-tem necessary to accomplish the actions in25.812(e)(1) and (e)(2).(c) Transverse Separation of the Fuselage. Inthe event of a transverse separation of the fuse-lage, compliance must be shown with 25.812(l)except as follows:(1) For each airplane type originally type certif-icated with a maximum passenger seating capac-ity of 9 or less, not more than 50 percent of allelectrically illuminated emergency lights requiredby 25.812 may be rendered inoperative in addi-tion to the lights that are directly damaged by theseparation.(2) For each airplane type originally type certif-icated with a maximum passenger seating capac-ity of 10 to 19, not more than 33 percent of allelectrically illuminated emergency lights requiredSFAR No. 109 to Part 25 Federal Aviation Regulations10 ASAby 25.812 may be rendered inoperative in addi-tion to the lights that are directly damaged by theseparation.10. Interior doors. In lieu of the requirementsof 25.813(e), interior doors may be installed be-tween passenger seats and exits, provided thefollowing requirements are met.(a) Each door between any passenger seat,occupiable for taxi, takeoff, and landing, and anyemergency exit must have a means to signal tothe ightcrew, at the ightdeck, that the door is inthe open position for taxi, takeoff and landing.(b) Appropriate procedures/limitations must beestablished to ensure that any such door is in theopen conguration for takeoff and landing.(c) Each door between any passenger seat andany exit must have dual means to retain it in theopen position, each of which is capable of react-ing the inertia loads specied in 25.561.(d) Doors installed across a longitudinal aislemust translate laterally to open and close, e.g.,pocket doors.(e) Each door between any passenger seatand any exit must be frangible in either direction.(f) Each door between any passenger seat andany exit must be operable from either side, and ifa locking mechanism is installed, it must be capa-ble of being unlocked from either side without theuse of special tools.11. Width of Aisle. Compliance is requiredwith 25.815, except that aisle width may be re-duced to 0 inches between passenger seats dur-ing in-ight operations only, provided that the ap-plicant demonstrates that all areas of the cabinare easily accessible by a crew member in theevent of an emergency (e.g., in-ight re, decom-pression). Additionally, instructions must be pro-vided at each passenger seat for restoring theaisle width required by 25.815. Procedures mustbe established and documented in the AFM to en-sure that the required aisle widths are providedduring taxi, takeoff, and landing.12. Materials for Compartment Interiors.Compliance is required with the applicable provi-sions of 25.853, except that compliance with Ap-pendix F, parts IV and V, to part 25, need not bedemonstrated if it can be shown by test or a com-bination of test and analysis that the maximumtime for evacuation of all occupants does not ex-ceed 45 seconds under the conditions specied inAppendix J to part 25.13. Fire Detection. For airplanes with a typecerticated passenger capacity of 20 or more,there must be means that meet the requirementsof 25.858(a) through (d) to signal the ightcrewin the event of a re in any isolated room not oc-cupiable for taxi, takeoff and landing, which canbe closed off from the rest of the cabin by a door.The indication must identify the compartmentwhere the re is located. This does not apply tolavatories, which continue to be governed by25.854.14. Cooktops. Each cooktop must be de-signed and installed to minimize any potentialthreat to the airplane, passengers, and crew.Compliance with this requirement must be foundin accordance with the following criteria:(a) Means, such as conspicuous burner-on in-dicators, physical barriers, or handholds, must beinstalled to minimize the potential for inadvertentpersonnel contact with hot surfaces of both thecooktop and cookware. Conditions of turbulencemust be considered.(b) Sufcient design means must be includedto restrain cookware while in place on the cook-top, as well as representative contents, e.g., soup,sauces, etc., from the effects of ight loads andturbulence. Restraints must be provided to pre-clude hazardous movement of cookware and con-tents. These restraints must accommodate anycookware that is identied for use with the cook-top. Restraints must be designed to be easily uti-lized and effective in service. The cookware re-straint system should also be designed so that itwill not be easily disabled, thus rendering it unus-able. Placarding must be installed which prohibitsthe use of cookware that cannot be accommo-dated by the restraint system.(c) Placarding must be installed which prohibitsthe use of cooktops (i.e., power on any burner)during taxi, takeoff, and landing.(d) Means must be provided to address thepossibility of a re occurring on or in the immedi-ate vicinity of the cooktop. Two acceptable meansof complying with this requirement are as follows:(1) Placarding must be installed that prohibitsany burner from being powered when the cooktopis unattended. (Note: This would prohibit a singleperson from cooking on the cooktop and intermit-tently serving food to passengers while anyburner is powered.) A re detector must be in-stalled in the vicinity of the cooktop which pro-vides an audible warning in the passenger cabin,and a re extinguisher of appropriate size and ex-tinguishing agent must be installed in the immedi-ate vicinity of the cooktop. Access to the extin-guisher may not be blocked by a re on or aroundthe cooktop.(2) An automatic, thermally activated re sup-pression system must be installed to extinguish are at the cooktop and immediately adjacent sur-faces. The agent used in the system must be anapproved total ooding agent suitable for use inan occupied area. The re suppression systemmust have a manual override. The automatic acti-vation of the re suppression system must alsoautomatically shut off power to the cooktop.(e) The surfaces of the galley surrounding thecooktop which would be exposed to a re on thecooktop surface or in cookware on the cooktopPart 25: Airworthiness Standards: Transport CategoryASA 1125must be constructed of materials that comply withthe ammability requirements of part III of Appen-dix F to part 25. This requirement is in addition tothe ammability requirements typically required ofthe materials in these galley surfaces. During theselection of these materials, consideration mustalso be given to ensure that the ammability char-acteristics of the materials will not be adverselyaffected by the use of cleaning agents and uten-sils used to remove cooking stains.(f) The cooktop must be ventilated with a sys-tem independent of the airplane cabin and cargoventilation system. Procedures and time intervalsmust be established to inspect and clean or re-place the ventilation system to prevent a re haz-ard from the accumulation of ammable oils andbe included in the instructions for continued air-worthiness. The ventilation system ducting mustbe protected by a ame arrestor. [Note: The appli-cant may nd additional useful information in So-ciety of Automotive Engineers, Aerospace Rec-ommended Practice 85, Rev. E, entitled Air Con-ditioning Systems for Subsonic Airplanes, datedAugust 1, 1991.](g) Means must be provided to contain spilledfoods or uids in a manner that will prevent thecreation of a slipping hazard to occupants and willnot lead to the loss of structural strength due toairplane corrosion.(h) Cooktop installations must provide ade-quate space for the user to immediately escape ahazardous cooktop condition.(i) A means to shut off power to the cooktopmust be provided at the galley containing thecooktop and in the cockpit. If additional switchesare introduced in the cockpit, revisions to smokeor re emergency procedures of the AFM will berequired.(j) If the cooktop is required to have a lid to en-close the cooktop there must be a means to auto-matically shut off power to the cooktop when thelid is closed.15. Hand-Held Fire Extinguishers.(a) For airplanes that were originally type certif-icated with more than 60 passengers, the numberof hand-held re extinguishers must be thegreater of(1) That provided in accordance with the re-quirements of 25.851, or(2) A number equal to the number of originallytype certicated exit pairs, regardless of whetherthe exits are deactivated for the proposed cong-uration.(b) Extinguishers must be evenly distributedthroughout the cabin. These extinguishers are inaddition to those required by paragraph 14 of thisSFAR, unless it can be shown that the cooktopwas installed in the immediate vicinity of the origi-nal exits.16. Security. The requirements of 25.795 arenot applicable to airplanes approved in accor-dance with this SFAR.[Docket No. FAA200728250, SFAR No. 109; 74 FR21541, May 8, 2009]25.1 Federal Aviation Regulations12 ASASubpart AGeneral25.1 Applicability.(a) This part prescribes airworthiness standardsfor the issue of type certicates, and changes tothose certicates, for transport category airplanes.(b) Each person who applies under Part 21 forsuch a certicate or change must show compli-ance with the applicable requirements in this part.25.2 Special retroactive requirements.The following special retroactive requirementsare applicable to an airplane for which the regula-tions referenced in the type certicate predate thesections specied below(a) Irrespective of the date of application, eachapplicant for a supplemental type certicate (or anamendment to a type certicate) involving an in-crease in passenger seating capacity to a totalgreater than that for which the airplane has beentype certicated must show that the airplane con-cerned meets the requirements of:(1) Sections 25.721(d), 25.783(g), 25.785(c),25.803(c) (2) through (9), 25.803 (d) and (e),25.807 (a), (c), and (d), 25.809 (f) and (h), 25.811,25.812, 25.813 (a), (b), and (c), 25.815, 25.817,25.853 (a) and (b), 25.855(a), 25.993(f), and25.1359(c) in effect on October 24, 1967, and(2) Sections 25.803(b) and 25.803(c)(1) in ef-fect on April 23, 1969.(b) Irrespective of the date of application, eachapplicant for a supplemental type certicate (or anamendment to a type certicate) for an airplanemanufactured after October 16, 1987, must showthat the airplane meets the requirements of25.807(c)(7) in effect on July 24, 1989.(c) Compliance with subsequent revisions tothe sections specied in paragraph (a) or (b) ofthis section may be elected or may be required inaccordance with 21.101(a) of this chapter.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2572, 55 FR 29773, July 20, 1990;Amdt. No. 2599, 65 FR 36266, June 7, 2000; Amdt. 2599, 66 FR 56989, Nov. 14, 2001]25.3 Special provisions for ETOPS type design approvals.(a) Applicability. This section applies to an ap-plicant for ETOPS type design approval of an air-plane:(1) That has an existing type certicate on Feb-ruary 15, 2007; or(2) For which an application for an original typecerticate was submitted before February 15,2007.(b) Airplanes with two engines.(1) For ETOPS type design approval of an air-plane up to and including 180 minutes, an appli-cant must comply with 25.1535, except that itneed not comply with the following provisions ofAppendix K, K25.1.4, of this part:(i) K25.1.4(a), fuel system pressure and owrequirements;(ii) K25.1.4(a)(3), low fuel alerting; and(iii) K25.1.4(c), engine oil tank design.(2) For ETOPS type design approval of an air-plane beyond 180 minutes an applicant mustcomply with 25.1535.(c) Airplanes with more than two engines.An applicant for ETOPS type design approvalmust comply with 25.1535 for an airplane manu-factured on or after February 17, 2015, exceptthat, for an airplane congured for a three personight crew, the applicant need not comply with Ap-pendix K, K25.1.4(a)(3), of this part, low fuel alert-ing.[Docket No. FAA20026717, 72 FR 1873, Jan. 16,2007]25.5 Incorporations by reference.(a) The materials listed in this section are incor-porated by reference in the corresponding sec-tions noted. These incorporations by referencewere approved by the Director of the Federal Reg-ister in accordance with 5 U.S.C. 552(a) and 1CFR part 51. These materials are incorporated asthey exist on the date of the approval, and noticeof any change in these materials will be publishedin the Federal Register. The materials are avail-able for purchase at the corresponding addressesnoted below, and all are available for inspection atthe National Archives and Records Administration(NARA), and at FAA, Transport Airplane Director-ate, Aircraft Certication Service, 1601 Lind Ave-nue SW, Renton, Washington 98057-3356. For in-formation on the availability of this material atNARA, call 202-741-6030, or go to:http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html(b) The following materials are available forpurchase from the following address: The Na-tional Technical Information Services (NTIS),Springeld, Virginia 22166.(1) Fuel Tank Flammability AssessmentMethod Users Manual, dated May 2008, docu-ment number DOT/FAA/AR-05/8, IBR approvedfor 25.981 and Appendix N. It can also be ob-tained at the following Web site:http://www.re.tc.faa.gov/systems/fueltank/FTFAM.stm(2) [Reserved][Docket No. FAA200522997, 73 FR 42494, July 21,2008]Part 25: Airworthiness Standards: Transport Category 25.25ASA 1325Subpart BFlightGENERAL25.21 Proof of compliance.(a) Each requirement of this subpart must bemet at each appropriate combination of weightand center of gravity within the range of loadingconditions for which certication is requested.This must be shown(1) By tests upon an airplane of the type forwhich certication is requested, or by calculationsbased on, and equal in accuracy to, the results oftesting; and(2) By systematic investigation of each proba-ble combination of weight and center of gravity, ifcompliance cannot be reasonably inferred fromcombinations investigated.(b) [Reserved](c) The controllability, stability, trim, and stallingcharacteristics of the airplane must be shown foreach altitude up to the maximum expected in op-eration.(d) Parameters critical for the test being con-ducted, such as weight, loading (center of gravityand inertia), airspeed, power, and wind, must bemaintained within acceptable tolerances of thecritical values during ight testing.(e) If compliance with the ight characteristicsrequirements is dependent upon a stability aug-mentation system or upon any other automatic orpower-operated system, compliance must beshown with 25.671 and 25.672.(f) In meeting the requirements of 25.105(d),25.125, 25.233, and 25.237, the wind velocitymust be measured at a height of 10 meters abovethe surface, or corrected for the difference be-tween the height at which the wind velocity is mea-sured and the 10-meter height.(g) The requirements of this subpart associ-ated with icing conditions apply only if the appli-cant is seeking certication for ight in icing condi-tions.(1) Each requirement of this subpart, except25.121(a), 25.123(c), 25.143(b)(1) and (b)(2),25.149, 25.201(c)(2), 25.207(c) and (d), 25.239,and 25.251(b) through (e), must be met in icingconditions. Compliance must be shown using theice accretions dened in appendix C, assumingnormal operation of the airplane and its ice pro-tection system in accordance with the operatinglimitations and operating procedures establishedby the applicant and provided in the AirplaneFlight Manual.(2) No changes in the load distribution limits of25.23, the weight limits of 25.25 (except wherelimited by performance requirements of this sub-part), and the center of gravity limits of 25.27,from those for non-icing conditions, are allowedfor ight in icing conditions or with ice accretion.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2523, 35 FR 5671, April 8, 1970;Amdt. 2542, 43 FR 2320, Jan. 16, 1978; Amdt. 2572,55 FR 29774, July 20, 1990; Amdt. 25121, 72 FR44665, Aug. 8, 2007]25.23 Load distribution limits.(a) Ranges of weights and centers of gravitywithin which the airplane may be safely operatedmust be established. If a weight and center ofgravity combination is allowable only within cer-tain load distribution limits (such as spanwise)that could be inadvertently exceeded, these limitsand the corresponding weight and center of grav-ity combinations must be established.(b) The load distribution limits may not ex-ceed(1) The selected limits;(2) The limits at which the structure is proven; or(3) The limits at which compliance with eachapplicable ight requirement of this subpart isshown.25.25 Weight limits.(a) Maximum weights. Maximum weights corre-sponding to the airplane operating conditions(such as ramp, ground or water taxi, takeoff, enroute, and landing), environmental conditions(such as altitude and temperature), and loadingconditions (such as zero fuel weight, center ofgravity position and weight distribution) must beestablished so that they are not more than(1) The highest weight selected by the appli-cant for the particular conditions; or(2) The highest weight at which compliancewith each applicable structural loading and ightrequirement is shown, except that for airplanesequipped with standby power rocket engines themaximum weight must not be more than the high-est weight established in accordance with Appen-dix E of this part; or(3) The highest weight at which compliance isshown with the certication requirements of Part36 of this chapter.(b) Minimum weight. The minimum weight (thelowest weight at which compliance with each ap-plicable requirement of this part is shown) mustbe established so that it is not less than(1) The lowest weight selected by the applicant;(2) The design minimum weight (the lowestweight at which compliance with each structuralloading condition of this part is shown); or(3) The lowest weight at which compliance witheach applicable ight requirement is shown.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2523, 35 FR 5671, April 8, 1970;Amdt. 2563, 53 FR 16365, May 6, 1988]25.27 Federal Aviation Regulations14 ASA25.27 Center of gravity limits.The extreme forward and the extreme aft cen-ter of gravity limitations must be established foreach practicably separable operating condition.No such limit may lie beyond(a) The extremes selected by the applicant;(b) The extremes within which the structure isproven; or(c) The extremes within which compliance witheach applicable ight requirement is shown.25.29 Empty weight and corresponding center of gravity.(a) The empty weight and corresponding centerof gravity must be determined by weighing the air-plane with(1) Fixed ballast;(2) Unusable fuel determined under 25.959;and(3) Full operating uids, including(i) Oil;(ii) Hydraulic uid; and(iii) Other uids required for normal operation ofairplane systems, except potable water, lavatoryprecharge water, and uids intended for injectionin the engine.(b) The condition of the airplane at the time ofdetermining empty weight must be one that is welldened and can be easily repeated.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2542, 43 FR 2320, Jan. 16, 1978;Amdt. 2572, 55 FR 29774, July 20, 1990]25.31 Removable ballast.Removable ballast may be used on showingcompliance with the ight requirements of thissubpart.25.33 Propeller speed and pitch limits.(a) The propeller speed and pitch must be lim-ited to values that will ensure(1) Safe operation under normal operating con-ditions; and(2) Compliance with the performance require-ments of 25.101 through 25.125.(b) There must be a propeller speed limitingmeans at the governor. It must limit the maximumpossible governed engine speed to a value notexceeding the maximum allowable r.p.m.(c) The means used to limit the low pitch posi-tion of the propeller blades must be set so that theengine does not exceed 103 percent of the maxi-mum allowable engine rpm or 99 percent of anapproved maximum overspeed, whichever isgreater, with(1) The propeller blades at the low pitch limitand governor inoperative;(2) The airplane stationary under standard at-mospheric conditions with no wind; and(3) The engines operating at the takeoff mani-fold pressure limit for reciprocating engine pow-ered airplanes or the maximum takeoff torquelimit for turbopropeller engine-powered airplanes.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2557, 49 FR 6848, Feb. 23, 1984;Amdt. 2572, 55 FR 29774, July 20, 1990]PERFORMANCE25.101 General.(a) Unless otherwise prescribed, airplanesmust meet the applicable performance require-ments of this subpart for ambient atmosphericconditions and still air.(b) The performance, as affected by enginepower or thrust, must be based on the followingrelative humidities;(1) For turbine engine powered airplanes, a rel-ative humidity of (i) 80 percent, at and below standard tempera-tures; and(ii) 34 percent, at and above standard tempera-tures plus 50F.Between these two temperatures, the relativehumidity must vary linearly.(2) For reciprocating engine powered air-planes, a relative humidity of 80 percent in a stan-dard atmosphere. Engine power corrections forvapor pressure must be made in accordance withthe following table:AltitudeH (ft.)Vaporpressure e (In. Hg.)Specichumidity w(Lb. moisture per lb. dry air)Density ratio / = 0.00237690 0.403 0.00849 0.995081,000 .354 .00773 .966722,000 .311 .00703 .938953,000 .272 .00638 .911784,000 .238 .00578 .885145,000 .207 .00523 .859106,000 .1805 .00472 .833617,000 .1566 .00425 .808708,000 .1356 .00382 .784349,000 .1172 .00343 .7605310,000 .1010 .00307 .7372215,000 .0463 .001710 .6286820,000 .01978 .000896 .5326325,000 .00778 .000436 .44806Part 25: Airworthiness Standards: Transport Category 25.105ASA 1525(c) The performance must correspond to thepropulsive thrust available under the particularambient atmospheric conditions, the particularight condition, and the relative humidity speciedin paragraph (b) of this section. The available pro-pulsive thrust must correspond to engine power orthrust, not exceeding the approved power orthrust less(1) Installation losses; and(2) The power or equivalent thrust absorbed bythe accessories and services appropriate to theparticular ambient atmospheric conditions andthe particular ight condition.(d) Unless otherwise prescribed, the applicantmust select the takeoff, en route, approach, andlanding congurations for the airplane.(e) The airplane congurations may vary withweight, altitude, and temperature, to the extentthey are compatible with the operating proce-dures required by paragraph (f) of this section.(f) Unless otherwise prescribed, in determiningthe accelerate-stop distances, takeoff ight paths,takeoff distances, and landing distances, changesin the airplanes conguration, speed, power, andthrust, must be made in accordance with proce-dures established by the applicant for operation inservice.(g) Procedures for the execution of balkedlandings and missed approaches associated withthe conditions prescribed in 25.119 and25.121(d) must be established.(h) The procedures established under para-graphs (f) and (g) of this section must(1) Be able to be consistently executed in ser-vice by crews of average skill;(2) Use methods or devices that are safe andreliable; and(3) Include allowance for any time delays, in theexecution of the procedures, that may reasonablybe expected in service.(i) The accelerate-stop and landing distancesprescribed in 25.109 and 25.125, respectively,must be determined with all the airplane wheelbrake assemblies at the fully worn limit of their al-lowable wear range.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2538, 41 FR 55466, Dec. 20, 1976;Amdt. 2592, 63 FR 8318, Feb. 18, 1998]25.103 Stall speed.(a) The reference stall speed, VSR, is a cali-brated airspeed dened by the applicant. VSRmay not be less than a 1-g stall speed. VSRis ex-pressed as:where:VCLMAX= Calibrated airspeed obtained when theload factor-corrected lift coefcientis rst a maximum during the maneuver prescribed in paragraph (c) of this section. In addition, when the maneuver is limited by a device that abruptly pushes the nose down at a selected angle of attack (e.g., a stick pusher), VCLMAX may not be less than the speed existing at the instant the device operates;nZW = Load factor normal to the ight path at VCLMAXW = Airplane gross weight;S = Aerodynamic reference wing area; andq = Dynamic pressure.(b) VCLMAX is determined with:(1) Engines idling, or, if that resultant thrustcauses an appreciable decrease in stall speed,not more than zero thrust at the stall speed;(2) Propeller pitch controls (if applicable) in thetakeoff position;(3) The airplane in other respects (such asaps, landing gear, and ice accretions) in the con-dition existing in the test or performance standardin which VSR is being used;(4) The weight used when VSRis being used asa factor to determine compliance with a requiredperformance standard;(5) The center of gravity position that results inthe highest value of reference stall speed; and(6) The airplane trimmed for straight ight at aspeed selected by the applicant, but not less than1.13 VSR and not greater than 1.3 VSR.(c) Starting from the stabilized trim condition,apply the longitudinal control to decelerate the air-plane so that the speed reduction does not ex-ceed one knot per second.(d) In addition to the requirements of paragraph(a) of this section, when a device that abruptlypushes the nose down at a selected angle of at-tack (e.g., a stick pusher) is installed, the refer-ence stall speed, VSR, may not be less than 2knots or 2 percent, whichever is greater, abovethe speed at which the device operates.[FAA200213902, 67 FR 70825, Nov. 26, 2002; asamended by Amdt. 25121, 72 FR 44665, Aug. 8, 2007]25.105 Takeoff.(a) The takeoff speeds prescribed by 25.107,the accelerate-stop distance prescribed by25.109, the takeoff path prescribed by 25.111,the takeoff distance and takeoff run prescribed by25.113, and the net takeoff ight path prescribedVSRVCLMAXnZW----------------- nZWWqS----------------( ,j \25.107 Federal Aviation Regulations16 ASAby 25.115, must be determined in the selectedconguration for takeoff at each weight, altitude,and ambient temperature within the operationallimits selected by the applicant(1) In non-icing conditions; and(2) In icing conditions, if in the conguration of25.121(b) with the takeoff ice accretion denedin appendix C:(i) The stall speed at maximum takeoff weightexceeds that in non-icing conditions by more thanthe greater of 3 knots CAS or 3 percent of VSR; or(ii) The degradation of the gradient of climb de-termined in accordance with 25.121(b) is greaterthan one-half of the applicable actual-to-net take-off ight path gradient reduction dened in25.115(b).(b) No takeoff made to determine the data re-quired by this section may require exceptional pi-loting skill or alertness.(c) The takeoff data must be based on(1) In the case of land planes and amphibians:(i) Smooth, dry and wet, hard-surfaced run-ways; and(ii) At the option of the applicant, grooved or po-rous friction course wet, hard-surfaced runways.(d) The takeoff data must include, within the es-tablished operational limits of the airplane, the fol-lowing operational correction factors:(1) Not more than 50 percent of nominal windcomponents along the takeoff path opposite tothe direction of takeoff, and not less than 150 per-cent of nominal wind components along the take-off path in the direction of takeoff.(2) Effective runway gradients.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2592, 63 FR 8318, Feb. 18, 1998;Amdt. 25121, 72 FR 44665, Aug. 8, 2007]25.107 Takeoff speeds.(a) V1must be established in relation to VEFasfollows:(1) VEFis the calibrated airspeed at which thecritical engine is assumed to fail. VEFmust be se-lected by the applicant, but may not be less thanVMCG determined under 25.149(e).(2) V1, in terms of calibrated airspeed, is se-lected by the applicant; however, V1may not beless than VEFplus the speed gained with criticalengine inoperative during the time interval be-tween the instant at which the critical engine isfailed, and the instant at which the pilot recog-nizes and reacts to the engine failure, as indicatedby the pilots initiation of the rst action (e.g., ap-plying brakes, reducing thrust, deploying speedbrakes) to stop the airplane during accelerate-stop tests.(b) V2MIN, in terms of calibrated airspeed, maynot be less than(1) 1.13 VSRfor(i) Two-engine and three-engine turbopropellerand reciprocating engine powered airplanes; and(ii) Turbojet powered airplanes without provi-sions for obtaining a signicant reduction in theone-engine-inoperative power-on stall speed;(2) 1.08 VSRfor(i) Turbopropeller and reciprocating enginepowered airplanes with more than three engines;and(ii) Turbojet powered airplanes with provisionsfor obtaining a signicant reduction in the one-en-gine-inoperative power-on stall speed; and(3) 1.10 times VMCestablished under 25.149.(c) V2, in terms of calibrated airspeed, must beselected by the applicant to provide at least thegradient of climb required by 25.121(b) but maynot be less than(1) V2MIN;(2) VRplus the speed increment attained (in ac-cordance with 25.111(c)(2)) before reaching aheight of 35 feet above the takeoff surface; and(3) A speed that provides the maneuvering ca-pability specied in 25.143(h).(d) VMUis the calibrated airspeed at and abovewhich the airplane can safely lift off the ground,and continue the takeoff. VMUspeeds must be se-lected by the applicant throughout the range ofthrust-to-weight ratios to be certicated. Thesespeeds may be established from free air data ifthese data are veried by ground takeoff tests.(e) VR, in terms of calibrated airspeed, must beselected in accordance with the conditions ofparagraphs (e) (1) through (4) of this section:(1) VR may not be less than(i) V1(ii) 105 percent of VMC;(iii) The speed (determined in accordance with25.111(c)(2)) that allows reaching V2beforereaching a height of 35 feet above the takeoff sur-face; or(iv) A speed that, if the airplane is rotated at itsmaximum practicable rate, will result in a VLOFofnot less than 110 percent of VMUin the all-en-gines-operating condition and not less than 105percent of VMU determined at the thrust-to-weightratio corresponding to the one-engine-inoperativecondition.(2) For any given set of conditions (such asweight, conguration, and temperature), a singlevalue of VR, obtained in accordance with thisparagraph, must be used to show compliancewith both the one-engine-inoperative and the all-engines-operating takeoff provisions.(3) It must be shown that the one-engine-inop-erative takeoff distance, using a rotation speed of5 knots less than VRestablished in accordancewith paragraphs (e)(1) and (2) of this section,does not exceed the corresponding one-engine-inoperative takeoff distance using the establishedPart 25: Airworthiness Standards: Transport Category 25.109ASA 1725VR. The takeoff distances must be determined inaccordance with 25.113(a)(1).(4) Reasonably expected variations in servicefrom the established takeoff procedures for theoperation of the airplane (such as over-rotation ofthe airplane and out-of-trim conditions) may notresult in unsafe ight characteristics or in markedincreases in the scheduled takeoff distances es-tablished in accordance with 25.113(a).(f) VLOFis the calibrated airspeed at which theairplane rst becomes airborne.(g) VFTO, in terms of calibrated airspeed, mustbe selected by the applicant to provide at least thegradient of climb required by 25.121(c), but maynot be less than(1) 1.18 VSR; and(2) A speed that provides the maneuvering ca-pability specied in 25.143(h).(h) In determining the takeoff speeds V1, VR,and V2for ight in icing conditions, the values ofVMCG, VMC, and VMUdetermined for non-icingconditions may be used.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2538, 41 FR 55466, Dec. 20, 1976;Amdt. 2542, 43 FR 2320, Jan. 16, 1978; Amdt. 2592,63 FR 8318, Feb. 18, 1998; Amdt. 2594, 63 FR 8848,Feb. 23, 1998; Amdt. 25108, 67 FR 70826, Nov. 26,2002; Amdt. 25121, 72 FR 44665, Aug. 8, 2007]25.109 Accelerate-stop distance.(a) The accelerate-stop distance on a dry run-way is the greater of the following distances:(1) The sum of the distances necessary to(i) Accelerate the airplane from a standing startwith all engines operating to VEFfor takeoff from adry runway;(ii) Allow the airplane to accelerate from VEFtothe highest speed reached during the rejectedtakeoff, assuming the critical engine fails at VEFand the pilot takes the rst action to reject thetakeoff at the V1for takeoff from a dry runway;and(iii) Come to a full stop on a dry runway fromthe speed reached as prescribed in paragraph(a)(1)(ii) of this section; plus(iv) A distance equivalent to 2 seconds at theV1 for takeoff from a dry runway.(2) The sum of the distances necessary to(i) Accelerate the airplane from a standing startwith all engines operating to the highest speedreached during the rejected takeoff, assuming thepilot takes the rst action to reject the takeoff atthe V1 for takeoff from a dry runway; and(ii) With all engines still operating, come to a fullstop on dry runway from the speed reached asprescribed in paragraph (a)(2)(i) of this section;plus(iii) A distance equivalent to 2 seconds at theV1 for takeoff from a dry runway.(b) The accelerate-stop distance on a wet run-way is the greater of the following distances:(1) The accelerate-stop distance on a dry run-way determined in accordance with paragraph (a)of this section; or(2) The accelerate-stop distance determined inaccordance with paragraph (a) of this section, ex-cept that the runway is wet and the correspondingwet runway values of VEFand V1are used. In de-termining the wet runway accelerate-stop dis-tance, the stopping force from the wheel brakesmay never exceed:(i) The wheel brakes stopping force determinedin meeting the requirements of 25.101(i) andparagraph (a) of this section; and(ii) The force resulting from the wet runwaybraking coefcient of friction determined in accor-dance with paragraphs (c) or (d) of this section, asapplicable, taking into account the distribution ofthe normal load between braked and unbrakedwheels at the most adverse center-of-gravity posi-tion approved for takeoff.(c) The wet runway braking coefcient of fric-tion for a smooth wet runway is dened as a curveof friction coefcient versus ground speed andmust be computed as follows:25.109 Federal Aviation Regulations18 ASA(1) The maximum tire-to-ground wet runwaybraking coefcient of friction is dened as:WhereTire Pressure = maximum airplane operating tire pressure (psi);t/gMAX= maximum tire-to-ground braking coefcient;V = airplane true ground speed (knots); andLinear interpolation may be used for tire pres-sures other than those listed.(2) The maximum tire-to-ground wet runwaybraking coefcient of friction must be adjusted totake into account the efciency of the anti-skidsystem on a wet runway. Anti-skid system opera-tion must be demonstrated by ight testing on asmooth wet runway, and its efciency must be de-termined. Unless a specic anti-skid system ef-ciency is determined from a quantitative analysisof the ight testing on a smooth wet runway, themaximum tire-to-ground wet runway braking coef-cient of friction determined in paragraph (c)(1) ofthis section must be multiplied by the efciencyvalue associated with the type of anti-skid systeminstalled on the airplane:(d) At the option of the applicant, a higher wetrunway braking coefcient of friction may be usedfor runway surfaces that have been grooved ortreated with a porous friction course material. Forgrooved and porous friction course runways, thewet runway braking coefcient of friction is de-ned as either:(1) 70 percent of the dry runway braking coef-cient of friction used to determine the dry runwayaccelerate-stop distance; or(2) The wet runway braking coefcient denedin paragraph (c) of this section, except that a spe-cic anti-skid system efciency, if determined, isappropriate for a grooved or porous frictioncourse wet runway, and the maximum tire-to-ground wet runway braking coefcient of friction isdened as:Tire Pressure (psi) Maximum Braking Coefcient (tire-to-ground)50100200300t g MAX0.0350 V100---------( ,j \3 0.306 V100---------( ,j \20.851 V100---------( ,j \ 0.883 + + =t g MAX0.0437 V100---------( ,j \3 0.320 V100---------( ,j \20.805 V100---------( ,j \ 0.804 + + =t g MAX0.0331 V100---------( ,j \3 0.252 V100---------( ,j \20.658 V100---------( ,j \ 0.692 + + =t g MAX0.0401 V100---------( ,j \3 0.263 V100---------( ,j \20.611 V100---------( ,j \ 0.614 + + =Type of anti-skid system Efciency valueOn-Off 0.30Quasi-Modulating 0.50Full Modulating 0.80Part 25: Airworthiness Standards: Transport Category 25.111ASA 1925WhereTire Pressure = maximum airplane operating tire pressure (psi);t/gMAX = maximum tire-to-ground braking coefcient;V = airplane true ground speed (knots); andLinear interpolation may be used for tire pres-sures other than those listed.(e) Except as provided in paragraph (f)(1) ofthis section, means other than wheel brakes maybe used to determine the accelerate-stop dis-tance if that means(1) Is safe and reliable;(2) Is used so that consistent results can be ex-pected under normal operating conditions; and(3) Is such that exceptional skill is not requiredto control the airplane.(f) The effects of available reverse thrust(1) Shall not be included as an additionalmeans of deceleration when determining the ac-celerate-stop distance on a dry runway; and(2) May be included as an additional means ofdeceleration using recommended reverse thrustprocedures when determining the accelerate-stopdistance on a wet runway, provided the require-ments of paragraph (e) of this section are met.(g) The landing gear must remain extendedthroughout the accelerate-stop distance.(h) If the accelerate-stop distance includes astopway with surface characteristics substantiallydifferent from those on the runway, the takeoffdata must include operational correction factorsfor the accelerate-stop distance. The correctionfactors must account for the particular surfacecharacteristics of the stopway and the variationsin these characteristics with seasonal weatherconditions (such as temperature, rain, snow, andice) within the established operational limits.(i) A ight test demonstration of the maximumbrake kinetic energy accelerate-stop distancemust be conducted with not more than 10 percentof the allowable brake wear range remaining oneach of the airplane wheel brakes.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2542, 43 FR 2321, Jan. 16, 1978;Amdt. 2592, 63 FR 8318, Feb. 18, 1998]25.111 Takeoff path.(a) The takeoff path extends from a standingstart to a point in the takeoff at which the airplaneis 1,500 feet above the takeoff surface, or at whichthe transition from the takeoff to the en route con-guration is completed and VFTOis reached,whichever point is higher. In addition(1) The takeoff path must be based on the pro-cedures prescribed in 25.101(f);(2) The airplane must be accelerated on theground to VEF, at which point the critical enginemust be made inoperative and remain inoperativefor the rest of the takeoff; and(3) After reaching VEF, the airplane must be ac-celerated to V2.(b) During the acceleration to speed V2, thenose gear may be raised off the ground at aspeed not less than VR. However, landing gear re-traction may not be begun until the airplane is air-borne.(c) During the takeoff path determination in ac-cordance with paragraphs (a) and (b) of this sec-tion(1) The slope of the airborne part of the takeoffpath must be positive at each point;(2) The airplane must reach V2before it is 35feet above the takeoff surface and must continueat a speed as close as practical to, but not lessthan V2, until it is 400 feet above the takeoff sur-face;(3) At each point along the takeoff path, start-ing at the point at which the airplane reaches 400feet above the takeoff surface, the available gradi-ent of climb may not be less than(i) 1.2 percent for two-engine airplanes;(ii) 1.5 percent for three-engine airplanes; and(iii) 1.7 percent for four-engine airplanes.Tire Pressure (psi) Maximum Braking Coefcient (tire-to-ground)50100200300t g MAX0.1470V100-------( ,j \5= 1.050V100-------( ,j \4 2.673V100-------( ,j \32.683V100-------( ,j \2 0.403V100-------( ,j \0.859 + + +t g MAX0.1106V100-------( ,j \5= 0.813V100-------( ,j \4 2.130V100-------( ,j \32.200V100-------( ,j \2 0.317V100-------( ,j \0.807 + + +t g MAX0.0498V100-------( ,j \5= 0.398V100-------( ,j \4 1.140V100-------( ,j \31.285V100-------( ,j \2 0.140V100-------( ,j \0.701 + + +t g MAX0.0314V100-------( ,j \5= 0.247V100-------( ,j \4 0.703V100-------( ,j \30.779V100-------( ,j \2 0.00954V100-------( ,j \0.614 + + +25.111 Federal Aviation Regulations20 ASA(4) The airplane conguration may not bechanged, except for gear retraction and automaticpropeller feathering, and no change in power orthrust that requires action by the pilot may bemade until the airplane is 400 feet above the take-off surface; and(5) If 25.105(a)(2) requires the takeoff path tobe determined for ight in icing conditions, the air-borne part of the takeoff must be based on the air-plane drag:(i) With the takeoff ice accretion dened in ap-pendix C, from a height of 35 feet above the take-off surface up to the point where the airplane is400 feet above the takeoff surface; and(ii) With the nal takeoff ice accretion dened inappendix C, from the point where the airplane is400 feet above the takeoff surface to the end ofthe takeoff path.(4) Except for gear retraction and propellerfeathering, the airplane conguration may not bechanged, and no change in power or thrust thatrequires action by the pilot may be made, until theairplane is 400 feet above the takeoff surface.(d) The takeoff path must be determined by acontinuous demonstrated takeoff or by synthesisfrom segments. If the takeoff path is determinedby the segmental method(1) The segments must be clearly dened andmust be related to the distinct changes in the con-guration, power or thrust, and speed;(2) The weight of the airplane, the congura-tion, and the power or thrust must be constantthroughout each segment and must correspondto the most critical condition prevailing in the seg-ment;(3) The ight path must be based on the air-planes performance without ground effect; and(4) The takeoff path data must be checked bycontinuous demonstrated takeoffs up to the pointat which the airplane is out of ground effect andits speed is stabilized, to ensure that the path isconservative relative to the continuous path.The airplane is considered to be out of the groundeffect when it reaches a height equal to its wingspan.(e) For airplanes equipped with standby powerrocket engines, the takeoff path may be deter-mined in accordance with section II of Appendix E.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 256, 30 FR 8468, July 2, 1965;Amdt. 2542, 43 FR 2321, Jan. 16, 1978; Amdt. 2554,45 FR 60172, Sept. 11, 1980; Amdt. 2572, 55 FR29774, July 20, 1990; Amdt. 2594, 63 FR 8848, Feb.23, 1998; Amdt. 25108, 67 FR 70826, Nov. 26, 2002;Amdt. 25121, 72 FR 44666, Aug. 8, 2007]25.113 Takeoff distance and takeoff run.(a) Takeoff distance on a dry runway is thegreater of (1) The horizontal distance along the takeoffpath from the start of the takeoff to the point atwhich the airplane is 35 feet above the takeoffsurface, determined under 25.111 for a dry run-way; or(2) 115 percent of the horizontal distance alongthe takeoff path, with all engines operating, fromthe start of the takeoff to the point at which the air-plane is 35 feet above the takeoff surface, as de-termined by a procedure consistent with 25.111.(b) Takeoff distance on a wet runway is thegreater of (1) The takeoff distance on a dry runway deter-mined in accordance with paragraph (a) of thissection; or(2) The horizontal distance along the takeoffpath from the start of the takeoff to the point atwhich the airplane is 15 feet above the takeoffsurface, achieved in a manner consistent with theachievement of V2before reaching 35 feet abovethe takeoff surface, determined under 25.111 fora wet runway.(c) If the takeoff distance does not include aclearway, the takeoff run is equal to the takeoffdistance. If the takeoff distance includes a clear-way(1) The takeoff run on a dry runway is thegreater of (i) The horizontal distance along the takeoffpath from the start of the takeoff to a point equi-distant between the point at which VLOFisreached and the point at which the airplane is 35feet above the takeoff surface, as determined un-der 25.111 for a dry runway; or(ii) 115 percent of the horizontal distance alongthe takeoff path, with all engines operating, fromthe start of the takeoff to a point equidistant be-tween the point at which VLOFis reached and thepoint at which the airplane is 35 feet above thetakeoff surface, determined by a procedure con-sistent with 25.111.(2) The takeoff run on a wet runway is thegreater of (i) The horizontal distance along the takeoffpath from the start of the takeoff to the point atwhich the airplane is 15 feet above the takeoffsurface, achieved in a manner consistent with theachievement of V2before reaching 35 feet abovethe takeoff surface, as determined under 25.111for a wet runway; or(ii) 115 percent of the horizontal distance alongthe takeoff path, with all engines operating, fromthe start of the takeoff to a point equidistant be-tween the point at which VLOFis reached and thepoint at which the airplane is 35 feet above thePart 25: Airworthiness Standards: Transport Category 25.121ASA 2125takeoff surface, determined by a procedure con-sistent with 25.111.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2523, 35 FR 5671, April 8, 1970;Amdt. 2592, 63 FR 8320, Feb. 18, 1998]25.115 Takeoff ight path.(a) The takeoff ight path shall be considered tobegin 35 feet above the takeoff surface at the endof the takeoff distance determined in accordancewith 25.113(a) or (b), as appropriate for the run-way surface condition.(b) The net takeoff ight path data must be de-termined so that they represent the actual takeoffight paths (determined in accordance with25.111 and with paragraph (a) of this section) re-duced at each point by a gradient of climb equalto(1) 0.8 percent for two-engine airplanes;(2) 0.9 percent for three-engine airplanes; and(3) 1.0 percent for four-engine airplanes.(c) The prescribed reduction in climb gradientmay be applied as an equivalent reduction in ac-celeration along that part of the takeoff ight pathat which the airplane is accelerated in level ight.[Docket No. 5066, 29 FR 18291, Dec. 24, 1964; asamended by Amdt. 2592, 63 FR 8320, Feb. 18, 1998]25.117 Climb: general.Compliance with the requirements of 25.119and 25.121 must be shown at each weight, alti-tude, and ambient temperature within the opera-tional limits established for the airplane and withthe most unfavorable center of gravity for eachconguration.25.119 Landing climb: All-engines-operating.In the landing conguration, the steady gradi-ent of climb may not be less than 3.2 percent, withthe engines at the power or thrust that is available8 seconds after initiation of movement of thepower or thrust controls from the minimum ightidle to the go-around power or thrust setting(a) In non-icing conditions, with a climb speedof VREFdetermined in accordance with25.125(b)(2)(i); and(b) In icing conditions with the landing ice ac-cretion dened in appendix C, and with a climbspeed of VREFdetermined in accordance with25.125(b)(2)(ii).[Docket No. FAA200522840, 72 FR 44666, Aug. 8,2007]25.121 Climb: One-engine-inoperative.(a) Takeoff; landing gear extended. In the criti-cal takeoff conguration existing along the ightpath (between the points at which the airplanereaches VLOFand at which the landing gear isfully retracted) and in the conguration used in25.111 but without ground effect, the steady gra-dient of climb must be positive for two-engine air-planes, and not less than 0.3 percent for three-en-gine airplanes or 0.5 percent for four-engine air-planes, at VLOF and with(1) The critical engine inoperative and the re-maining engines at the power or thrust availablewhen retraction of the landing gear is begun in ac-cordance with 25.111 unless there is a more crit-ical power operating condition existing later alongthe ight path but before the point at which thelanding gear is fully retracted; and(2) The weight equal to the weight existingwhen retraction of the landing gear is begun, de-termined under 25.111.(b) Takeoff; landing gear retracted. In the take-off conguration existing at the point of the ightpath at which the landing gear is fully retracted,and in the conguration used in 25.111 but with-out ground effect:(1) The steady gradient of climb may not beless than 2.4 percent for two-engine airplanes,2.7 percent for three-engine airplanes, and 3.0percent for four-engine airplanes, at V2 with:(i) The critical engine inoperative, the remainingengines at the takeoff power or thrust available atthe time the landing gear is fully retracted, deter-mined under 25.111, unless there is a more crit-ical power operating condition existing later alongthe ight path but before the point where the air-plane reaches a height of 400 feet above the take-off surface; and(ii) The weight equal to the weight existingwhen the airplanes landing gear is fully retracted,determined under 25.111.(2) The requirements of paragraph (b)(1) of thissection must be met:(i) In non-icing conditions; and(ii) In icing conditions with the takeoff ice accre-tion dened in appendix C, if in the congurationof 25.121(b) with the takeoff ice accretion:(A) The stall speed at maximum takeoff weightexceeds that in non-icing conditions by more thanthe greater of 3 knots CAS or 3 percent of VSR; or(B) The degradation of the gradient of climb de-termined in accordance with 25.121(b) is greaterthan one-half of the applicable actual-to-net take-off ight path gradient reduction dened in25.115(b).(c) Final takeoff. In the en route conguration atthe end of the takeoff path determined in accor-dance with 25.111:(1) The steady gradient of climb may not beless than 1.2 percent for two-engine airplanes,1.5 percent for three-engine airplanes, and 1.7percent for four-engine airplanes, at VFTO with25.123 Federal Aviation Regulations22 ASA(i) The critical engine inoperative and the re-maining engines at the available maximum contin-uous power or thrust; and(ii) The weight equal to the weight existing atthe end of the takeoff path, determined under25.111.(2) The requirements of paragraph (c)(1) of thissection must be met:(i) In non-icing conditions; and(ii) In icing conditions with the nal takeoff iceaccretion dened in appendix C, if in the congu-ration of 25.121(b) with the takeoff ice accretion:(A) The stall speed at maximum takeoff weightexceeds that in non-icing conditions by more thanthe greater of 3 knots CAS or 3 percent of VSR; or(B) The degradation of the gradient of climb de-termined in accordance with 25.121(b) is greaterthan one-half of the applicable actual-to-net take-off ight path gradient reduction dened in25.115(b).(d) Approach. In a conguration correspondingto the normal all-engines-operating procedure inwhich VSRfor this conguration does not exceed110 percent of the VSRfor the related all-engines