CS 25.101 General

ED Decision 2016/010/R

(See AMC 25.101)

(a) Unless otherwise prescribed, aeroplanes must meet the applicable performance requirements of this Subpart for ambient atmospheric conditions and still air.

(b) The performance, as affected by engine power or thrust, must be based on the following relative humidities:

(1) 80%, at and below standard temperatures; and

(2) 34%, at and above standard temperatures plus 28°C (50°F).

Between these two temperatures, the relative humidity must vary linearly.

(c) The performance must correspond to the propulsive thrust available under the particular ambient atmospheric conditions, the particular flight condition, and the relative humidity specified in sub-paragraph (b) of this paragraph. The available propulsive thrust must correspond to engine power or thrust, not exceeding the approved power or thrust, less –

(1) Installation losses; and

(2) The power or equivalent thrust absorbed by the accessories and services appropriate to the particular ambient atmospheric conditions and the particular flight condition. (See AMCs No 1 and No 2 to CS 25.101(c).)

(d) Unless otherwise prescribed, the applicant must select the take-off, en-route, approach, and landing configuration for the aeroplane.

(e) The aeroplane configurations may vary with weight, altitude, and temperature, to the extent they are compatible with the operating procedures required by sub-paragraph (f) of this paragraph.

(f) Unless otherwise prescribed, in determining the accelerate-stop distances, take-off flight paths, take-off distances, and landing distances, changes in the aeroplane’s configuration, speed, power, and thrust, must be made in accordance with procedures established by the applicant for operation in service.

(g) Procedures for the execution of balked landings and missed approaches associated with the conditions prescribed in CS 25.119 and 25.121(d) must be established. (See AMC 25.101(g))

(h) The procedures established under sub-paragraphs (f) and (g) of this paragraph must –

(1) Be able to be consistently executed in service by crews of average skill,

(2) Use methods or devices that are safe and reliable, and

(3) Include allowance for any time delays in the execution of the procedures, that may reasonably be expected in service. (See AMC 25.101(h)(3).)

(i) The accelerate-stop and landing distances prescribed in CS 25.109 and 25.125, respectively, must be determined with all the aeroplane wheel brake assemblies at the fully worn limit of their allowable wear range. (See AMC 25.101(i).)

[Amdt 25/2]

[Amdt 25/18]

AMC 25.101 General

ED Decision 2003/2/RM

The test aeroplane used in the determination of the scheduled performance should be in a condition which, as far as is reasonably possible, is representative of the average new production aeroplane. Where the test aeroplane differs from this standard (e.g. with regard to engine idle thrust settings, flap rigging, etc.) it will be necessary to correct the measured performance for any significant performance effects of such differences.

AMC No. 1 to CS 25.101(c) Extrapolation of Performance with Weight

ED Decision 2003/2/RM

The variation of take-off, climb and landing performance with weight may be extrapolated without conservatism to a weight greater, by up to 10%, than the maximum weight tested and to a weight lower, by up to 10%, than the lowest weight tested. These ranges may not be applicable if there are significant discontinuities, or unusual variations, in the scheduling of the relevant speeds with weight, in the weight ranges covered by extrapolation.

AMC No. 2 to CS 25.101(c) General

ED Decision 2003/2/RM

1 GENERAL - CS 25.101

1.1 Explanation - Propulsion System Behaviour. CS 25.101(c) requires that aeroplane “performance must correspond to the propulsive thrust available under the particular ambient atmospheric conditions, the particular flight condition, . . .” The propulsion system’s (i.e., turbine engines and propellers, where appropriate) installed performance characteristics are primarily a function of engine power setting, airspeed, propeller efficiency (where applicable), altitude, and ambient temperature. The effects of each of these variables must be determined in order to establish the thrust available for aeroplane performance calculations.

1.2 Procedures.

1.2.1 The intent is to develop a model of propulsion system performance that covers the approved flight envelope. Furthermore, it should be shown that the combination of the propulsion system performance model and the aeroplane performance model are validated by the takeoff performance test data, climb performance tests, and tests used to determine aeroplane drag. Installed propulsion system performance characteristics may be established via the following tests and analyses:

a. Steady-state engine power setting vs. thrust (or power) testing. Engines should be equipped with adequate instrumentation to allow the determination of thrust (or power). Data should be acquired in order to validate the model, including propeller installed thrust, if applicable, over the range of power settings, altitudes, temperatures, and airspeeds for which approval is sought. Although it is not possible to definitively list or foresee all of the types of instrumentation that might be considered adequate for determining thrust (or power) output, two examples used in past certification programmes are: (1) engine pressure rakes, with engines calibrated in a ground test cell, and (2) fan speed, with engines calibrated in a ground test cell and the calibration data validated by the use of a flying test bed. In any case, the applicant should substantiate the adequacy of the instrumentation to be used for determining the thrust (or power) output.

b. Lapse rate takeoff testing to characterise the behaviour of power setting, rotor speeds, propeller effects (i.e., torque, RPM, and blade angle), or gas temperature as a function of time, thermal state, or airspeed, as appropriate. These tests should include the operation of an Automatic Takeoff Thrust Control System (ATTCS), if applicable, and should cover the range of power settings for which approval is sought.

i. Data for higher altitude power settings may be acquired via overboost (i.e., operating at a higher than normal power setting for the conditions) with the consent of the engine and propeller (when applicable) manufacturer(s). When considering the use of overboost on turbopropeller propulsion system installations to simulate higher altitude and ambient temperature range conditions, the capability to achieve an appropriate simulation should be evaluated based on the engine and propeller control system(s) and aircraft performance and structural considerations. Engine (gearbox) torque, rotor speed, or gas temperature limits, including protection devices to prohibit or limit exceedences, may prevent the required amount of overboost needed for performance at the maximum airport altitude sought for approval. Overboost may be considered as increased torque, reduced propeller speed, or a combination of both in order to achieve the appropriate blade angle for the higher altitude and ambient temperature range simulation. Consideration for extrapolations will depend on the applicant’s substantiation of the proper turbopropeller propulsion system simulated test conditions.

ii. Lapse rate characteristics should be validated by takeoff demonstrations at the maximum airport altitude for which takeoff approval is being sought. Alternatively, if overboost (see paragraph (i) above) is used to simulate the thrust setting parameters of the maximum airport altitude for which takeoff approval is sought, the takeoff demonstrations of lapse rate characteristics can be performed at an airport altitude up to 915 m (3,000 feet) lower than the maximum airport altitude.

c. Thrust calculation substantiation. Installed thrust should be calculated via a mathematical model of the propulsion system, or other appropriate means, adjusted as necessary to match the measured inflight performance characteristics of the installed propulsion system. The propulsion system mathematical model should define the relationship of thrust to the power setting parameter over the range of power setting, airspeed, altitude, and temperature for which approval is sought. For turbojet aeroplanes, the propulsion system mathematical model should be substantiated by ground tests in which thrust is directly measured via a calibrated load cell or equivalent means. For turbopropeller aeroplanes, the engine power measurements should be substantiated by a calibrated dynamometer or equivalent means, the engine jet thrust should be established by an acceptable engine model, and the propeller thrust and power characteristics should be substantiated by wind tunnel testing or equivalent means.

d. Effects of ambient temperature. The flight tests of paragraph 1.2.1.a. above will typically provide data over a broad range of ambient temperatures. Additional data may also be obtained from other flight or ground tests of the same type or series of engine. The objective is to confirm that the propulsion system model accurately reflects the effects of temperature over the range of ambient temperatures for which approval is being sought (operating envelope). Because thrust (or power) data can usually be normalised versus temperature using either dimensionless variables (e.g., theta exponents) or a thermodynamic cycle model, it is usually unnecessary to obtain data over the entire ambient temperature range. There is no need to conduct additional testing if:

i. The data show that the behaviour of thrust and limiting parameters versus ambient temperature can be predicted accurately; and

ii. Analysis based upon the test data shows that the propulsion system will operate at rated thrust without exceeding propulsion system limits.

1.2.2 Extrapolation of propulsion system performance data to 915 m (3,000 feet) above the highest airport altitude tested (up to the maximum takeoff airport altitude to be approved) is acceptable, provided the supporting data, including flight test and propulsion system operations data (e.g., engine and propeller control, limits exceedence, and surge protection devices scheduling), substantiates the proposed extrapolation procedures. Considerations for extrapolation depend upon an applicant's determination, understanding, and substantiation of the critical operating modes of the propulsion system. This understanding includes a determination and quantification of the effects that propulsion system installation and variations in ambient conditions have on these modes.

2 Expansion of Takeoff and Landing Data for a Range of Airport Elevations.

2.1 These guidelines are applicable to expanding aeroplane Flight Manual takeoff and landing data above and below the altitude at which the aeroplane takeoff and landing performance tests are conducted.

2.2 With installed propulsion system performance characteristics that have been adequately defined and verified, aeroplane takeoff and landing performance data obtained at one field elevation may be extrapolated to higher and lower altitudes within the limits of the operating envelope without applying additional performance conservatisms. It should be noted, however, that extrapolation of the propulsion system data used in the determination and validation of propulsion system performance characteristics is typically limited to 915 m (3,000 feet) above the highest altitude at which propulsion system parameters were evaluated for the pertinent power/thrust setting. (See paragraph 1 of this AMC for more information on an acceptable means of establishing and verifying installed propulsion system performance characteristics.)

2.3 Note that certification testing for operation at airports that are above 2438 m (8,000 feet) should also include functional tests of the cabin pressurisation system. Consideration should be given to any other systems whose operation may be sensitive to, or dependent upon airport altitude, such as: engine and APU starting, passenger oxygen, autopilot, autoland, autothrottle system thrust set/operation."

AMC 25.101(g) Go-around

ED Decision 2020/024/R

1. General

CS 25.101(g) requires that procedures must be established for the execution of go-arounds from landing configurations (identified as ‘balked landings’ in this AMC) and from approach configurations (identified as ‘missed approaches’ in this AMC) associated with the conditions prescribed in CS 25.119 and CS 25.121(d). Also, as required by CS 25.1587(b)(4), each AFM must contain the procedures established under CS 25.101(g), including any relevant limitations or information. The landing climb gradient determined under the CS 25.119 conditions, the approach climb gradient determined under the CS 25.121(d) conditions, and the additional operating limitations regarding the maximum landing weight established in accordance with CS 25.1533(a)(2) must be consistent with the established balked landing and missed approach procedures (CS 25.101(g)) provided in the aeroplane flight manual (AFM). In order to demonstrate the acceptability of the recommended missed approach and balked landing procedures, the applicant should conduct demonstrations (by flight test or pilot‑in‑the‑loop simulator tests) to include a one engine inoperative go-around at a weight, altitude, temperature (WAT)-limited or simulated WAT‑limited thrust or power condition.

The applicant should conduct the demonstrations at WAT-limited conditions that result in the greatest height loss and/or longest horizontal distance to accelerate to the scheduled approach climb speed. Alternatively, the applicant may conduct testing at simulated WAT-limited conditions (with reduced thrust or power on the operating engine) and use the resulting time delays for each crew action in a subsequent off-line simulation/analysis in accordance with the procedures below. Although compliance with CS 25.101(g) and (h) and CS 25.121(d) is not directly linked with the criteria for the approval of weather minima for approach, the minimum decision height for initiating a go-around is dependent upon the weather minima to be approved. In addition, a steeper climb gradient and the associated lower WAT-limited landing weight may be associated with CAT II operations. As such, if CAT II weather minima approval is expected, the applicant should conduct the go-around demonstration and/or analysis consistent with both CAT I and II operations for the associated decision height and WAT-limited thrust or power condition (or a critical combination thereof).

2. Procedures

The go-around demonstration specified in Chapter 1 of this AMC can be conducted at an altitude above the normal decision height/altitude (for test safety), with the height loss in the manoeuvre used to show that ground contact prior to the runway threshold would not occur if the manoeuvre was initiated at the decision height/altitude. Flight testing, simulation and/or analysis at a range of (WAT limit or simulated WAT limit) conditions throughout the approved envelope should be conducted to assess the height loss relative to the decision height/altitude consistent with the criteria for the weather minima to be approved (or higher as constrained by AFM limitations). At least one flight test or pilot-in-the-loop simulator test should be conducted at a WAT-limited condition to assess the OEI go-around procedure and establish the time delays used for any subsequent analysis/simulation.

In addition, the assessment of the go-around procedure should include consideration of the horizontal distance (based upon the minimum go-around trajectory) needed to establish the minimum engine‑out climb gradient required by CS 25.121(d) or a steeper gradient as required by specific weather minima operational criteria. It should be shown by flight test, simulation and/or analysis that the aeroplane would remain above the profile illustrated in Figure 1 below when the go-around is evaluated at the critical WAT limit condition (up to the structural maximal landing weight) and flown in accordance with the one-engine-inoperative (OEI) go‑around procedure.

This provides a minimum design standard trajectory for a missed approach with one engine inoperative and does not constitute a means to ensure obstacle clearance. It does not preclude additional missed approach procedures that may be developed to satisfy operational requirements, including special or complex missed approach path requirements. The operator should seek approval from their national aviation authority to use the additional procedures and data.

(a) In accordance with CS 25.101(h), the established procedures for executing balked landings and missed approaches must:

(i) be able to be consistently executed in service by crews of average skill,

(ii) use methods or devices that are safe and reliable, and

(iii) include allowance for any time delays in the execution of the procedures that may reasonably be expected in service (including the recovery of full go-around thrust or power if equipped with a reduced go-around (RGA) thrust or power function that requires a manual override), but should not be less than one second between successive flight crew actions, except for movements of the primary flying controls.

(b) The flight test demonstration(s), simulation and/or analysis should be made with:

(i) all engines operating (AEO) and the thrust or power initially set for a 3-degree approach, and the configuration and final approach airspeed consistent with the AEO landing procedure (not more than VREF + 5 kt) in zero wind conditions,

(ii) application of the available go-around thrust or power at the selected go-around height (initially the RGA thrust or power level, if so equipped, followed by either automatic or manual selection of full go-around thrust or power in accordance with the established missed approach and engine failure AFM procedures) with simultaneous failure of the critical engine (or with a simulated engine failure, including the effects on dependent systems), and

(iii) the high-lift system, pitch attitude, engine/propeller controls and airspeed adjusted to achieve the conditions consistent with CS 25.121(d), in accordance with the established missed approach and engine failure AFM procedures. The landing gear should be selected to the ‘up’ position only after a positive rate of climb is achieved. If the use of automatic features (autopilot, auto-throttle, flight director, etc.) is included in the procedure, these features should be considered during the demonstration.

Figure 1. Trajectory Assessment for OEI Go-around

Segment A: From the initiation of go-around at the decision height/altitude to the runway threshold – remain above a 1:50 (2.0 %) plane extended to the runway threshold for clearance of airport obstacles.

Segment B: From the runway threshold plus a distance defined by 40 seconds * VT_appr, not more than the distance indicated in the table below – remain above ground height.

Field Elevation (ft)

Distance (ft)

0-3 048 m (0-10 000 ft)

3 048 m (10 000 ft)

>3 048 m (> 10 000 ft)

= Field Elevation

Segment C: A straight line from the end of Segment B at ground height with a gradient defined by CS 25.121(d)(1) or a steeper gradient as required by specific weather minima operational criteria, up to a height, H1 – remain above the line.

Where:

VT_appr is the true airspeed for the normal recommended AEO approach speed in zero wind at the flight condition being assessed (not more than VREF + 9.3 km/h (5 kt) CAS).

H1 is the height above the runway elevation where the aeroplane has achieved the approach climb configuration and stabilised on the approach climb speed out of ground effect (1x the wingspan), not less than the height at which the go-around was initiated.

[Amdt 25/13]

[Amdt 25/26]

AMC 25.101(h)(3) General

ED Decision 2003/2/RM

CS 25.109(a) and (b) require the accelerate-stop distance to include a distance equivalent to 2 seconds at V1 in addition to the demonstrated distance to accelerate to V1 and then bring the aeroplane to a full stop. This additional distance is not intended to allow extra time for making a decision to stop as the aeroplane passes through V1, but is to account for operational variability in the time it takes pilots to accomplish the actions necessary to bring the aeroplane to a stop. It allows for the typical requirement for up to three pilot actions (i.e. brakes – throttles – spoilers) without introducing additional time delays to those demonstrated. If the procedures require more than three pilot actions, an allowance for time delays must be made in the scheduled accelerate-stop distance. These delays, which are applied in addition to the demonstrated delays, are to be 1 second (or 2 seconds if a command to another crew member to take the action is required) for each action beyond the third action. This is illustrated in Figure 1.

FIGURE 1. ACCELERATE-STOP TIME DELAYS

where:–

VEF is the calibrated airspeed selected by the applicant at which the critical engine is assumed to fail. The relationship between VEF and V1 is defined in CS 25.107.

∆tact 1 = the demonstrated time interval between engine failure and activation of the first deceleration device. This time interval is defined as beginning at the instant the critical engine is failed and ending when the pilot recognises and reacts to the engine failure, as indicated by the pilot’s application of the first retarding means during accelerate-stop tests. A sufficient number of demonstrations should be conducted using both applicant and Agency test pilots to assure that the time increment is representative and repeatable. The pilot’s feet should be on the rudder pedals, not the brakes, during the tests. For AFM data expansion purposes, in order to provide a recognition time increment that can be executed consistently in service, this time increment should be equal to the demonstrated time or 1 second, whichever is greater. If the aeroplane incorporates an engine failure warning light, the recognition time includes the time increment necessary for the engine to spool down to the point of warning light activation, plus the time increment from light ‘on’ to pilot action indicating recognition of the engine failure.

∆tact 2 = the demonstrated time interval between activation of the first and second deceleration devices.

∆tact 3 = the demonstrated time interval between activation of the second and third deceleration devices.

∆tact 4→n = the demonstrated time interval between activation of the third and fourth (and any subsequent) deceleration devices. For AFM expansion, a 1-second reaction time delay to account for in-service variations should be added to the demonstrated activation time interval between the third and fourth (and any subsequent) deceleration devices. If a command is required for another crew member to actuate a deceleration device, a 2-second delay, in lieu of the 1-second delay, should be applied for each action. For automatic deceleration devices that are approved for performance credit for AFM data expansion, established systems actuation times determined during certification testing may be used without the application of the additional time delays required by this paragraph.

AMC 25.101(i) Performance determination with worn brakes

ED Decision 2003/2/RM

It is not necessary for all the performance testing on the aircraft to be conducted with fully worn brakes. Sufficient data should be available from aircraft or dynamometer rig tests covering the range of wear and energy levels to enable correction of the flight test results to the 100% worn level. The only aircraft test that should be carried out at a specific brake wear state is the maximum kinetic energy rejected take-off test of CS 25.109(i), for which all brakes should have not more than 10% of the allowable brake wear remaining.

CS 25.103 Stall speed

ED Decision 2016/010/R

(See AMC 25.103)

(a) The reference stall speed VSR is a calibrated airspeed defined by the applicant. VSR may not be less than a 1-g stall speed. VSR is expressed as:

where –

VCLMAX = Calibrated airspeed obtained when the loadfactor-corrected lift coefficient is first a maximum during the manoeuvre prescribed in sub-paragraph (c) of this paragraph. In addition, when the manoeuvre 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 flight path at VCLMAX;

W    = Aeroplane gross weight;

S= Aerodynamic reference wing area; and

q= Dynamic pressure.

(b) VCLMAX is determined with:

(1) Engines idling, or, if that resultant thrust causes an appreciable decrease in stall speed, not more than zero thrust at the stall speed;

(2) Propeller pitch controls (if applicable) in the take-off position;

(3) The aeroplane in other respects (such as flaps, landing gear, and ice accretions) in the condition existing in the test or performance standard in which VSR is being used;

(4) The weight used when VSR is being used as a factor to determine compliance with a required performance standard;

(5) The centre of gravity position that results in the highest value of reference stall speed; and

(6) The aeroplane trimmed for straight flight at a speed selected by the applicant, but not less than 1.13 VSR and not greater than 1.3 VSR. (See AMC 25.103(b))

(c) Starting from the stabilised trim condition, apply the longitudinal control to decelerate the aeroplane so that the speed reduction does not exceed 0.5 m/s2 (one knot per second). (See AMC 25.103(b) and (c)).

(d) In addition to the requirements of sub-paragraph (a) of this paragraph, when a device that abruptly pushes the nose down at a selected angle of attack (e.g. a stick pusher) is installed, the reference stall speed, VSR, may not be less than 3,7 km/h (2 kt) or 2%, whichever is greater, above the speed at which the device operates. (See AMC 25.103(d))

[Amdt 25/3]

[Amdt 25/18]

AMC 25.103(b) Stalling speed

ED Decision 2003/2/RM

The airplane should be trimmed for hands-off flight at a speed 13 percent to 30 percent above the anticipated VSR with the engines at idle and the airplane in the configuration for which the stall speed is being determined. Then, using only the primary longitudinal control for speed reduction, a constant deceleration (entry rate) is maintained until the airplane is stalled, as defined in CS 25.201(d). Following the stall, engine thrust may be used as desired to expedite the recovery.

The analysis to determine VCLMAX should disregard any transient or dynamic increases in recorded load factor, such as might be generated by abrupt control inputs, which do not reflect the lift capability of the aeroplane. The load factor normal to the flight path should be nominally 1.0 until VCLMAX is reached.

AMC 25.103(c) Stall speed

ED Decision 2003/2/RM

The stall entry rate is defined as the mean rate of speed reduction (in m/s2 (knots CAS/second)) in the deceleration to the stall in the particular stall demonstration, from a speed 10% above that stall speed, i.e.

AMC 25.103(d) Stall speed

ED Decision 2003/2/RM

In the case where a device that abruptly pushes the nose down at a selected angle of attack (e.g. a stick pusher) operates after CLMAX, the speed at which the device operates, stated in CS 25.103(d), need not be corrected to 1g.

Test procedures should be in accordance with AMC 25.103(b) to ensure that no abnormal or unusual pilot control input is used to obtain an artificially low device activation speed.

CS 25.105 Take-off

ED Decision 2015/008/R

(a) The take-off speeds prescribed by CS 25.107, the accelerate-stop distance prescribed by CS 25.109, the take-off path prescribed by CS 25.111, the take-off distance and take-off run prescribed by CS 25.113, and the net take-off flight path prescribed by CS 25.115, must be determined in the selected configuration for take-off at each weight, altitude, and ambient temperature within the operational limits selected by the applicant -

(1) In non-icing conditions; and

(2) In icing conditions, if in the configuration used to show compliance with CS 25.121(b), and with the most critical of the “Take-off Ice” accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g):

(i) The stall speed at maximum take-off weight exceeds that in non-icing conditions by more than the greater of 5.6 km/h (3 knots) CAS or 3% of VSR; or

(ii) The degradation of the gradient of climb determined in accordance with CS 25.121(b) is greater than one-half of the applicable actual-to-net take-off flight path gradient reduction defined in CS 25.115(b).

(b) No take-off made to determine the data required by this paragraph may require exceptional piloting skill or alertness.

(c) The take-off data must be based on:

(1) Smooth, dry and wet, hard-surfaced runways; and

(2) At the option of the applicant, grooved or porous friction course wet, hardsurfaced runways.

(d) The take-off data must include, within the established operational limits of the aeroplane, the following operational correction factors:

(1) Not more than 50% of nominal wind components along the take-off path opposite to the direction of take-off, and not less than 150% of nominal wind components along the take-off path in the direction of take-off.

(2) Effective runway gradients.

[Amdt 25/3]

[Amdt 25/16]

CS 25.107 Take-off speeds

ED Decision 2016/010/R

(a) V1 must be established in relation to VEF as follows:

(1) VEF is the calibrated airspeed at which the critical engine is assumed to fail. VEF must be selected by the applicant, but may not be less than VMCG determined under CS 25.149(e).

(2) V1, in terms of calibrated airspeed, is selected by the applicant; however, V1 may not be less than VEF plus the speed gained with the critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognises and reacts to the engine failure, as indicated by the pilot’s initiation of the first action (e.g. applying brakes, reducing thrust, deploying speed brakes) to stop the aeroplane during accelerate-stop tests.

(b) V2MIN, in terms of calibrated airspeed, may not be less than –

(1) 1·13 VSR for –

(i) Two-engined and three-engined turbo-propeller powered aeroplanes; and

(ii) Turbojet powered aeroplanes without provisions for obtaining a significant reduction in the one-engineinoperative power-on stall speed;

(2) 1·08 VSR for –

(i) Turbo-propeller powered aeroplanes with more than three engines; and

(ii) Turbojet powered aeroplanes with provisions for obtaining a significant reduction in the one-engine-inoperative power-on stall speed: and

(3) 1·10 times VMC established under CS 25.149.

(c) V2, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by CS 25.121(b) but may not be less than –

(1) V2MIN;

(2) VR plus the speed increment attained (in accordance with CS 25.111(c)(2)) before reaching a height of 11 m (35 ft) above the takeoff surface; and

(3) A speed that provides the manoeuvring capability specified in CS 25.143(h).

(d) VMU is the calibrated airspeed at and above which the aeroplane can safely lift off the ground, and continue the take-off. VMU speeds must be selected by the applicant throughout the range of thrust-to-weight ratios to be certificated. These speeds may be established from free air data if these data are verified by ground take-off tests. (See AMC 25.107(d).)

(e) VR, in terms of calibrated air speed, must be selected in accordance with the conditions of sub-paragraphs (1) to (4) of this paragraph:

(1) VR may not be less than –

(i) V1;

(ii) 105% of VMC;

(iii) The speed (determined in accordance with CS 25.111(c)(2)) that allows reaching V2 before reaching a height of 11 m (35 ft) above the take-off surface; or

(iv) A speed that, if the aeroplane is rotated at its maximum practicable rate, will result in a VLOF of not less than -

(A) 110% of VMU in the allengines-operating condition, and 105% of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition; or

(B) If the VMU attitude is limited by the geometry of the aeroplane (i.e., tail contact with the runway), 108% of VMU in the all-engines-operating condition and 104% of VMU determined at the thrust-to-weight ratio corresponding to the one-engine-inoperative condition. (See AMC 25.107(e)(1)(iv).)

(2) For any given set of conditions (such as weight, configuration, and temperature), a single value of VR, obtained in accordance with this paragraph, must be used to show compliance with both the one-engine-inoperative and the all-engines-operating take-off provisions.

(3) It must be shown that the one-engine-inoperative take-off distance, using a rotation speed of 9.3 km/h (5 knots) less than VR established in accordance with sub-paragraphs (e)(1) and (2) of this paragraph, does not exceed the corresponding one-engine-inoperative take-off distance using the established VR. The take-off distances must be determined in accordance with CS 25.113(a)(1). (See AMC 25.107(e)(3).)

(4) Reasonably expected variations in service from the established take-off procedures for the operation of the aeroplane (such as over-rotation of the aeroplane and out-of-trim conditions) may not result in unsafe flight characteristics or in marked increases in the scheduled take-off distances established in accordance with CS 25.113(a). (See AMC No. 1 to CS 25.107(e)(4) and AMC No. 2 to CS 25.107(e)(4).)

(f) VLOF is the calibrated airspeed at which the aeroplane first becomes airborne.

(g) VFTO, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by CS 25.121(c), but may not be less than –

(1) 1.18 VSR; and

(2) A speed that provides the manoeuvring capability specified in CS 25.143(h).

(h) In determining the take-off speeds V1, VR, and V2 for flight in icing conditions, the values of VMCG, VMC, and VMU determined for non-icing conditions may be used.

[Amdt 25/3]

[Amdt 25/18]

AMC 25.107(d) Take-off speeds

ED Decision 2003/2/RM

1 If cases are encountered where it is not possible to obtain the actual VMU at forward centre of gravity with aeroplanes having limited elevator power (including those aeroplanes which have limited elevator power only over a portion of the take-off weight range), it will be permissible to test with a more aft centre of gravity and/or more than normal nose-up trim to obtain VMU.

1.1 When VMU is obtained in this manner, the values should be corrected to those which would have been attained at forward centre of gravity if sufficient elevator power had been available. The variation of VMU with centre of gravity may be assumed to be the same as the variation of stalling speed in free air with centre of gravity for this correction.

1.2 In such cases where VMU has been measured with a more aft centre of gravity and/or with more than normal nose-up trim, the VR selected should (in addition to complying with the requirements of CS 25.107(e)) be greater by an adequate margin than the lowest speed at which the nose wheel can be raised from the runway with centre of gravity at its most critical position and with the trim set to the normal take-off setting for the weight and centre of gravity.

NOTE: A margin of 9,3 km/h (5 kt) between the lowest nose-wheel raising speed and VR would normally be considered to be adequate.

2 Take-offs made to demonstrate VMU should be continued until the aeroplane is out of ground effect. The aeroplane pitch attitude should not be decreased after lift-off.

AMC 25.107(e)(1)(iv) Take-off speeds

ED Decision 2003/2/RM

VMU Testing for Geometry Limited Aeroplanes.

1 For aeroplanes that are geometry limited (i.e., the minimum possible VMU speeds are limited by tail contact with the runway), CS 25.107(e)(1)(iv)(B) allows the VMU to VLOF speed margins to be reduced to 108% and 104% for the all-engines-operating and one-engineinoperative conditions, respectively. The VMU demonstrated must be sound and repeatable.

2 One acceptable means for demonstrating compliance with CS 25.107(d) and 25.107(e)(1)(iv) with respect to the capability for a safe lift-off and fly-away from the geometry limited condition is to show that at the lowest thrust-to-weight ratio for the all-engines-operating condition:

2.1  During the speed range from 96 to 100% of the actual lift-off speed, the aft under-surface of the aeroplane should be in contact with the runway. Because of the dynamic nature of the test, it is recognised that contact will probably not be maintained during this entire speed range, and some judgement is necessary. It has been found acceptable for contact to exist approximately 50% of the time that the aeroplane is in this speed range.

2.2  Beyond the point of lift-off to a height of 11m (35 ft), the aeroplane’s pitch attitude should not decrease below that at the point of lift-off, nor should the speed increase more than 10%.

2.3  The horizontal distance from the start of the take-off to a height of 11 m (35 ft) should not be greater than 105% of the distance determined in accordance with CS 25.113(a)(2) without the 115% factor.

AMC 25.107(e)(3) Take-off speeds

ED Decision 2003/2/RM

In showing compliance with CS 25.107(e)(3)

a. Rotation at a speed of VR-9,3 km/h (5 kt) should be carried out using, up to the point of lift-off, the same rotation technique, in terms of control input, as that used in establishing the one-engine-inoperative distance of CS 25.113(a)(1);

b. The engine failure speed used in the VR-9,3 km/h (5 kt) demonstration should be the same as that used in the comparative take-off rotating at VR;

c. The tests should be carried out both at the lowest practical weight (such that VR-9,3 km/h (5 kt) is not less than VMCG) and at a weight approaching take-off climb limiting conditions;

d. The tail or tail skid should not contact the runway.

AMC No. 1 to CS 25.107(e)(4) Take-off speeds

ED Decision 2003/2/RM

Reasonably expected variations in service from established take-off procedures should be evaluated in respect of out-of-trim conditions during certification flight test programmes. For example, normal take-off should be made with the longitudinal control trimmed to its most adverse position within the allowable take-off trim band.

AMC No. 2 to CS 25.107(e)(4) Take-off speeds

ED Decision 2003/2/RM

1 CS 25.107(e)(4) states that there must be no marked increase in the scheduled take-off distance when reasonably expected service variations, such as over-rotation, are encountered. This can be interpreted as requiring take-off tests with all engines operating with an abuse on rotation speed.

2 The expression ‘marked increase’ in the take-off distance is defined as any amount in excess of 1% of the scheduled take-off distance. Thus the abuse test should not result in a field length more than 101% of the scheduled field length.

3 For the early rotation abuse condition with all engines operating and at a weight as near as practicable to the maximum sea-level take-off weight, it should be shown by test that when the aeroplane is rotated rapidly at a speed which is 7% or 19 km/h (10 kt), whichever is lesser, below the scheduled VR speed, no ‘marked increase’ in the scheduled field length would result.

CS 25.109 Accelerate-stop distance

ED Decision 2016/010/R

(See AMC 25.109)

(a) (See AMC 25.109(a) and (b).) The accelerate-stop distance on a dry runway is the greater of the following distances:

(1) The sum of the distances necessary to –

(i) Accelerate the aeroplane from a standing start with all engines operating to VEF for take-off from a dry runway;

(ii) Allow the aeroplane to accelerate from VEF to the highest speed reached during the rejected take-off, assuming the critical engine fails at VEF and the pilot takes the first action to reject the take-off at the V1 for take-off from a dry runway; and

(iii) Come to a full stop on a dry runway from the speed reached as prescribed in sub-paragraph (a)(1)(ii) of this paragraph; plus

(iv) A distance equivalent to 2 seconds at the V1 for take-off from a dry runway.

(2) The sum of the distances necessary to –

(i) Accelerate the aeroplane from a standing start with all engines operating to the highest speed reached during the rejected take-off, assuming the pilot takes the first action to reject the take-off at the V1 for take-off from a dry runway; and

(ii) With all engines still operating, come to a full stop on a dry runway from the speed reached as prescribed in sub-paragraph (a)(2)(i) of this paragraph; plus

(iii) A distance equivalent to 2 seconds at the V1 for take-off from a dry runway.

(b) (See AMC 25.109(a) and (b).) The accelerate-stop distance on a wet runway is the greater of the following distances:

(1) The accelerate-stop distance on a dry runway determined in accordance with sub-paragraph (a) of this paragraph; or

(2) The accelerate-stop distance determined in accordance with sub-paragraph (a) of this paragraph, except that the runway is wet and the corresponding wet runway values of VEF and V1 are used. In determining the wet runway accelerate-stop distance, the stopping force from the wheel brakes may never exceed:

(i) The wheel brakes stopping force determined in meeting the requirements of CS 25.101(i) and sub-paragraph (a) of this paragraph; and

(ii) The force resulting from the wet runway braking coefficient of friction determined in accordance with subparagraphs (c) or (d) of this paragraph, as applicable, taking into account the distribution of the normal load between braked and unbraked wheels at the most adverse centre of gravity position approved for take-off.

(c) The wet runway braking coefficient of friction for a smooth wet runway is defined as a curve of friction coefficient versus ground speed and must be computed as follows:

(1) The maximum tyre-to-ground wet runway braking coefficient of friction is defined as (see Figure 1):

Tyre Pressure (psi)

Maximum Braking Coefficient (tyre-to-ground)

50

µt/gMAX = −0⋅0350 + 0⋅306 − 0⋅851 + 0⋅883

100

µt/gMAX = −0⋅0437 + 0⋅320 − 0⋅805 + 0⋅804

200

µt/gMAX = −0⋅0331 + 0⋅252 − 0⋅658 + 0⋅692

300

µt/gMAX = −0⋅0401 + 0⋅263 − 0⋅611 + 0⋅614

Figure 1

where:

Tyre Pressure = maximum aeroplane operating tyre pressure (psi)

µt/gMAX = maximum tyre-to-ground braking coefficient

V = aeroplane true ground speed (knots); and

Linear interpolation may be used for tyre pressures other than those listed.

(2) (See AMC 25.109(c)(2) The maximum tyre-to-ground wet runway braking coefficient of friction must be adjusted to take into account the efficiency of the anti-skid system on a wet runway. Anti-skid system operation must be demonstrated by flight testing on a smooth wet runway and its efficiency must be determined. Unless a specific anti-skid system efficiency is determined from a quantitative analysis of the flight testing on a smooth wet runway, the maximum tyre-to-ground wet runway braking coefficient of friction determined in sub-paragraph (c)(1) of this paragraph must be multiplied by the efficiency value associated with the type of anti-skid system installed on the aeroplane:

Type of anti-skid system

Efficiency value

On-off

0⋅30

Quasi-modulating

0⋅50

Fully modulating

0⋅80

(d) At the option of the applicant, a higher wet runway braking coefficient of friction may be used for runway surfaces that have been grooved or treated with a porous friction course material. For grooved and porous friction course runways,

(1) 70% of the dry runway braking coefficient of friction used to determine the dry runway accelerate-stop distance; or

(2) (See AMC 25.109(d)(2).) The wet runway braking coefficient of friction defined in sub-paragraph (c) of this paragraph, except that a specific anti-skid efficiency, if determined, is appropriate for a grooved or porous friction course wet runway and the maximum tyre-to-ground wet runway braking coefficient of friction is defined as (see Figure 2):

Tyre Pressure (psi)

Maximum Braking Coefficient (tyre-to-ground)

50

µt/gMAX = 0⋅147 −1⋅05 + 2⋅673 − 2⋅683 + 0⋅403 + 0⋅859

100

µt/gMAX = 0⋅1106 − 0⋅813 + 2⋅13 − 2⋅20 + 0⋅317 + 0⋅807

200

µt/gMAX = 0⋅0498 − 0⋅398 +1⋅14 −1⋅285 + 0⋅140 + 0.701

300

µt/gMAX = 0⋅0314 − 0⋅247 + 0⋅703 − 0⋅779 − 0⋅00954 + 0⋅614

Figure 2

where:

Tyre Pressure = maximum aeroplane operating tyre pressure (psi)

µt/gMAX = maximum tyre-to-ground braking coefficient

V   = aeroplane true ground speed (knots); and Linear interpolation may be used for tyre pressures other than those listed.

(e) Except as provided in sub-paragraph (f)(1) of this paragraph, means other than wheel brakes may be used to determine the accelerate-stop distance if that means –

(1)  Is safe and reliable;

(2) Is used so that consistent results can be expected under normal operating conditions; and

(3) Is such that exceptional skill is not required to control the aeroplane.

(f) The effects of available reverse thrust –

(1) Must not be included as an additional means of deceleration when determining the accelerate-stop distance on a dry runway; and

(2) May be included as an additional means of deceleration using recommended reverse thrust procedures when determining the accelerate-stop distance on a wet runway, provided the requirements of sub-paragraph (e) of this paragraph are met. (See AMC 25.109(f).)

(g) The landing gear must remain extended throughout the accelerate-stop distance.

(h) If the accelerate-stop distance includes a stopway with surface characteristics substantially different from those of the runway, the take-off data must include operational correction factors for the accelerate-stop distance. The correction factors must account for the particular surface characteristics of the stopway and the variations in these characteristics with seasonal weather conditions (such as temperature, rain, snow and ice) within the established operational limits.

(i) A flight test demonstration of the maximum brake kinetic energy accelerate-stop distance must be conducted with not more than 10% of the allowable brake wear range remaining on each of the aeroplane wheel brakes.

[Amdt 25/18]

AMC 25.109(a) and (b) Accelerate-stop distance

ED Decision 2003/2/RM

Propeller pitch position. For the one-engine-inoperative accelerate-stop distance, the critical engine’s propeller should be in the position it would normally assume when an engine fails and the power levers are closed. For dry runway one-engine-inoperative accelerate-stop distances, the high drag ground idle position of the operating engines’ propellers (defined by a pitch setting that results in not less than zero total thrust, i.e. propeller plus jet thrust, at zero airspeed) may be used provided adequate directional control is available on a wet runway and the related operational procedures comply with CS 25.109(f) and (h). Wet runway controllability may either be demonstrated by using the guidance available in AMC 25.109(f) at the appropriate power level, or adequate control can be assumed to be available at ground idle power if reverse thrust credit is approved for determining the wet runway accelerate-stop distances. For the all-engines-operating accelerate-stop distances on a dry runway, the high drag ground idle propeller position may be used for all engines (subject to CS 25.109(f) and (h)). For criteria relating to reverse thrust credit for wet runway accelerate-stop distances, see AMC 25.109(f).

AMC 25.109(c)(2) Accelerate-stop distance: anti-skid system efficiency

ED Decision 2003/2/RM

CS 25.109(c)(2) identifies 3 categories of anti-skid system and provides for either the use of a default efficiency value appropriate to the type of system or the determination of a specific efficiency value. Paragraph 1 of this AMC gives a description of the operating characteristics of each category to enable the classification of a particular system to be determined. Paragraph 2 gives an acceptable means of compliance with the requirement for flight testing and use of default efficiency values in accordance with CS 25.109(c)(2). These values are appropriate where the tuning of the anti-skid system is largely qualitative and without detailed quantitative analysis of system performance. Where detailed data recording and analysis is used to optimise system tuning, an efficiency value somewhat higher than the default value might be obtained and determined. Typically, a value of 40% might be achieved with an On/Off system. The quasi-modulating category covers a broad range of systems with varying performance levels. The best quasi-modulating systems might achieve an efficiency up to approximately 80%. Fully modulating systems have been tuned to efficiencies greater than 80% and up to a maximum of approximately 92%, which is considered to be the maximum efficiency on a wet runway normally achievable with fully modulating digital anti-skid systems. Paragraph 3 gives an acceptable means of compliance with CS 25.109(c)(2) where the applicant elects to determine a specific efficiency value.

In Paragraph 4 of this AMC, guidance is given on the use of 2 alternative methods for calculating antiskid system efficiency from the recorded data. One method is based on the variation of brake torque throughout the stop, while the other is based on wheel speed slip ratio. Finally, Paragraph 5 gives guidance on accounting for the distribution of the normal load between braked and unbraked wheels.

1 Classification of anti-skid system types

1.1 For the purposes of determining the default anti-skid efficiency value under CS 25.109(c)(2), anti-skid systems have been grouped into three broad classifications; on/off, quasi-modulating and fully modulating. These classifications represent evolving levels of technology and performance capabilities on both dry and wet runways.

1.2 On/off systems are the simplest of the three types of anti-skid systems. For these systems, fully metered brake pressure (as commanded by the pilot) is applied until wheel locking is sensed. Brake pressure is then released to allow the wheel to spin back up. When the system senses that the wheel is accelerating back to synchronous speed (i.e. ground speed), full metered pressure is again applied. The cycle of full pressure application/complete pressure release is repeated throughout the stop (or until the wheel ceases to skid with brake pressure applied).

1.3 Quasi-modulating systems attempt to continuously regulate brake pressure as a function of wheel speed. Typically, brake pressure is released when the wheel deceleration rate exceeds a preselected value. Brake pressure is re-applied at a lower level after a length of time appropriate to the depth of skid. Brake pressure is then gradually increased until another incipient skid condition is sensed. In general, the corrective actions taken by these systems to exit the skid condition are based on a pre-programmed sequence rather than the wheel speed time history.

1.4 Fully modulating systems are a further refinement of the quasi-modulating systems. The major difference between these two types of anti-skid systems is in the implementation of the skid control logic. During a skid, corrective action is based on the sensed wheel speed signal, rather than a preprogrammed response. Specifically, the amount of pressure reduction or reapplication is based on the rate at which the wheel is going into or recovering from a skid. Also, higher fidelity transducers and upgraded control systems are used, which respond more quickly.

1.5 In addition to examining the control system differences noted above, a time history of the response characteristics of the anti-skid system during a wet runway stop should be used to help identify the type of anti-skid system. Comparing the response characteristics from wet and dry runway stops can also be helpful.

Figure 1 shows an example of the response characteristics of a typical on-off system on both wet and dry runways. In general, the on-off system exhibits a cyclic behaviour of brake pressure application until a skid is sensed, followed by the complete release of brake pressure to allow the wheel to spin back up. Full metered pressure (as commanded by the pilot) is then re-applied, starting the cycle over again. The wheel speed trace exhibits deep and frequent skids (the troughs in the wheel speed trace), and the average wheel speed is significantly less than the synchronous speed (which is represented by the flat topped portions of the wheel speed trace). Note that the skids are deeper and more frequent on a wet runway than on a dry runway. For the particular example shown in Figure 1, the brake becomes torque-limited toward the end of the dry runway stop and is unable to generate enough torque to cause further skidding.

FIGURE 1. ANTI-SKID SYSTEM RESPONSE CHARACTERISTICS On-Off System

The effectiveness of quasi-modulating systems can vary significantly depending on the slipperiness of the runway and the design of the particular control system. On dry runways, these systems typically perform very well; however, on wet runways their performance is highly dependent on the design and tuning of the particular system. An example of the response characteristics of one such system is shown in Figure 2. On both dry and wet runways, brake pressure is released to the extent necessary to control skidding. As the wheel returns to the synchronous speed, brake pressure is quickly increased to a pre-determined level and then gradually ramped up to the full metered brake pressure. On a dry runway, this type of response reduces the depth and frequency of skidding compared to an on-off system. However, on a wet runway, skidding occurs at a pressure below that at which the gradual ramping of brake pressure occurs. As a result, on wet runways the particular system shown in Figure 2 operates very similarly to an on-off system.

FIGURE 2. ANTI-SKID SYSTEM RESPONSE CHARACTERISTICS Quasi-Modulating System

FIGURE 3. ANTI-SKID SYSTEM RESPONSE CHARACTERISTICS Fully Modulating System

When properly tuned, fully modulating systems are characterised by much smaller variations in brake pressure around a fairly high average value. These systems can respond quickly to developing skids and are capable of modulating brake pressure to reduce the frequency and depth of skidding. As a result, the average wheel speed remains much closer to the synchronous wheel speed. Figure 3 illustrates an example of the response characteristics of a fully modulating system on dry and wet runways.

2 Demonstration of anti-skid system operation when using the anti-skid efficiency values specified in CS 25.109(c)(2)

2.1 If the applicant elects to use one of the anti-skid efficiency values specified in CS 25.109(c)(2), a limited amount of flight testing must still be conducted to verify that the anti-skid system operates in a manner consistent with the type of anti-skid system declared by the applicant. This testing should also demonstrate that the anti-skid system has been properly tuned for operation on wet runways.

2.2 A minimum of one complete stop, or equivalent segmented stops, should be conducted on a smooth (i.e. not grooved or porous friction course) wet runway at an appropriate speed and energy to cover the critical operating mode of the anti-skid system. Since the objective of the test is to observe the operation (i.e. cycling) of the anti-skid system, this test will normally be conducted at an energy well below the maximum brake energy condition.

2.3 The section of the runway used for braking should be well soaked (i.e. not just damp), but not flooded. The runway test section should be wet enough to result in a number of cycles of anti-skid activity, but should not cause hydroplaning.

2.4 Before taxy and with cold tyres, the tyre pressure should be set to the highest value appropriate to the take-off weight for which approval is being sought.

2.5 The tyres and brakes should not be new, but need not be in the fully worn condition. They should be in a condition considered representative of typical in-service operations.

2.6 Sufficient data should be obtained to determine whether the system operates in a manner consistent with the type of anti-skid system declared by the applicant, provide evidence that full brake pressure is being applied upstream of the anti-skid valve during the flight test demonstration, determine whether the anti-skid valve is performing as intended and show that the anti-skid system has been properly tuned for a wet runway.

Typically, the following parameters should be plotted versus time:

(i) The speed of a representative number of wheels.

(ii) The hydraulic pressure at each brake (i.e. the hydraulic pressure downstream of the anti-skid valve, or the electrical input to each anti-skid valve).

(iii) The hydraulic pressure at each brake metering valve (i.e. upstream of the anti-skid valve).

2.7  A qualitative assessment of the anti-skid system response and aeroplane controllability should be made by the test pilot(s). In particular, pilot observations should confirm that:

(i) Anti-skid releases are neither excessively deep nor prolonged;

(ii) The gear is free of unusual dynamics; and

(iii) The aeroplane tracks essentially straight, even though runway seams, water puddles and wetter patches may not be uniformly distributed in location or extent.

3 Determination of a specific wet runway anti-skid system efficiency

3.1 If the applicant elects to derive the anti-skid system efficiency from flight test demonstrations, sufficient flight testing, with adequate instrumentation, must be conducted to ensure confidence in the value obtained. An anti-skid efficiency of 92% (i.e. a factor of 0·92) is considered to be the maximum efficiency on a wet runway normally achievable with fully modulating digital anti-skid systems.

3.2 A minimum of three complete stops, or equivalent segmented stops, should be conducted on a wet runway at appropriate speeds and energies to cover the critical operating modes of the anti-skid system. Since the objective of the test is to determine the efficiency of the anti-skid system, these tests will normally be conducted at energies well below the maximum brake energy condition. A sufficient range of speeds should be covered to investigate any variation of the anti-skid efficiency with speed.

3.3 The testing should be conducted on a smooth (i.e. not grooved or porous friction course) runway.

3.4 The section of the runway used for braking should be well soaked (i.e. not just damp), but not flooded. The runway test section should be wet enough to result in a number of cycles of anti-skid activity, but should not cause hydroplaning.

3.5 Before taxy and with cold tyres, the tyre pressure should be set to the highest value appropriate to the take-off weight for which approval is being sought.

3.6 The tyres and brake should not be new, but need not be in the fully worn condition. They should be in a condition considered representative of typical in-service operations.

3.7 A qualitative assessment of anti-skid system response and aeroplane controllability should be made by the test pilot(s). In particular, pilot observations should confirm that:

(i) The landing gear is free of unusual dynamics; and

(ii) The aeroplane tracks essentially straight, even though runway seams, water puddles and wetter patches may not be uniformly distributed in location or extent.

3.8  The wet runway anti-skid efficiency value should be determined as described in Paragraph 4 of this AMC. The test instrumentation and data collection should be consistent with the method used.

4 Calculation of anti-skid system efficiency

4.1 Paragraph 3 above provides guidance on the flight testing required to support the determination of a specific anti-skid system efficiency value. The following paragraphs describe 2 methods of calculating an efficiency value from the data recorded. These two methods, which yield equivalent results, are referred to as the torque method and the wheel slip method. Other methods may also be acceptable if they can be shown to give equivalent results.

4.2 Torque Method

Under the torque method, the anti-skid system efficiency is determined by comparing the energy absorbed by the brake during an actual wet runway stop to the energy that is determined by integrating, over the stopping distance, a curve defined by connecting the peaks of the instantaneous brake force curve (see figure 4). The energy absorbed by the brake during the actual wet runway stop is determined by integrating the curve of instantaneous brake force over the stopping distance.

FIGURE 4. INSTANTANEOUS BRAKE FORCE AND PEAK BRAKE FORCE

Using data obtained from the wet runway stopping tests of paragraph 3, instantaneous brake force can be calculated from the following relationship:

where:

Fb  = brake force

Tb  =  brake torque

α   =  wheel acceleration

I    =  wheel moment of inertia; and

Rtyre =  tyre radius

For brake installations where measuring brake torque directly is impractical, torque may be determined from other parameters (e.g. brake pressure) if a suitable correlation is available. Wheel acceleration is obtained from the first derivative of wheel speed. Instrumentation recording rates and data analysis techniques for wheel speed and torque data should be well matched to the anti-skid response characteristics to avoid introducing noise and other artifacts of the instrumentation system into the data.

Since the derivative of wheel speed is used in calculating brake force, smoothing of the wheel speed data is usually necessary to give good results. The smoothing algorithm should be carefully designed as it can affect the resulting efficiency calculation. Filtering or smoothing of the brake torque or brake force data should not normally be done. If conditioning is applied, it should be done in a conservative manner (i.e. result in a lower efficiency value) and should not misrepresent actual aeroplane/system dynamics.

Both the instantaneous brake force and the peak brake force should be integrated over the stopping distance. The anti-skid efficiency value for determining the wet runway accelerate-stop distance is the ratio of the instantaneous brake force integral to the peak brake force integral:

where:

η   =  anti-skid efficiency; and

s   =  stopping distance

The stopping distance is defined as the distance travelled during the specific wet runway stopping demonstration, beginning when the full braking configuration is obtained and ending at the lowest speed at which anti-skid cycling occurs (i.e. the brakes are not torque limited), except that this speed need not be less than 19 km/h (10 kt). Any variation in the anti-skid efficiency with speed should also be investigated, which can be accomplished by determining the efficiency over segments of the total stopping distance. If significant variations are noted, this variation should be reflected in the braking force used to determine the accelerate-stop distances (either by using a variable efficiency or by using a conservative single value).

4.3  Wheel Slip Method

At brake application, the tyre begins to slip with respect to the runway surface, i.e. the wheel speed slows down with respect to the aeroplane’s ground speed. As the amount of tyre slip increases, the brake force also increases until an optimal slip is reached. If the amount of slip continues to increase past the optimal slip, the braking force will decrease.

Using the wheel slip method, the anti-skid efficiency is determined by comparing the actual wheel slip measured during a wet runway stop to the optimal slip. Since the wheel slip varies significantly during the stop, sufficient wheel and ground speed data must be obtained to determine the variation of both the actual wheel slip and the optimal wheel slip over the length of the stop. A sampling rate of at least 16 samples per second for both wheel speed and ground speed has been found to yield acceptable fidelity.

For each wheel and ground speed data point, the instantaneous anti-skid efficiency value should be determined from the relationship shown in Figure 5:

FIGURE 5. ANTI-SKID EFFICIENCY – WHEEL SLIP RELATIONSHIP

WSR = wheel slip ratio =

OPS  = optimal slip ratio; and

ηi = instantaneous anti-skid efficiency

To determine the overall anti-skid efficiency value for use in calculating the wet runway accelerate-stop distance, the instantaneous anti-skid efficiencies should be integrated with respect to distance and divided by the total stopping distance:

where:

η   =  anti-skid efficiency; and

s   =  stopping distance

The stopping distance is defined as the distance travelled during the specific wet runway stopping demonstration, beginning when the full braking configuration is obtained and ending at the lowest speed at which anti-skid cycling occurs (i.e. the brakes are not torque limited), except that this speed need not be less than 19 km/h (10 kt). Any variation in the anti-skid efficiency with speed should also be investigated, which can be accomplished by determining the efficiency over segments of the total stopping distance. If significant variations are noted, this variation should be reflected in the braking force used to determine the accelerate-stop distances (either by using a variable efficiency or by using a conservative single value).

The applicant should provide substantiation of the optimal wheel slip value(s) used to determine the anti-skid efficiency value. An acceptable method for determining the optimal slip value(s) is to compare time history plots of the brake force and wheel slip data obtained during the wet runway stopping tests. For brake installations where measuring brake force directly is impractical, brake force may be determined from other parameters (e.g. brake pressure) if a suitable correlation is available. For those skids where wheel slip continues to increase after a reduction in the brake force, the optimal slip is the value corresponding to the brake force peak. See Figure 6 for an example and note how both the actual wheel slip and the optimal wheel slip can vary during the stop.

FIGURE 6. SUBSTANTIATION OF THE OPTIMAL SLIP VALUE

4.4  For dispatch with an inoperative anti-skid system (if approved), the wet runway acceleratestop distances should be based on an efficiency no higher than that allowed by CS 25.109(c)(2) for an on-off type of anti-skid system. The safety of this type of operation should be demonstrated by flight tests conducted in accordance with Paragraph 2 of this AMC.

5  Distribution of normal load between braked and unbraked wheels

In addition to taking into account the efficiency of the anti-skid system, CS 25.109(b)(2)(ii) also requires adjusting the braking force for the effect of the distribution of the normal load between braked and unbraked wheels at the most adverse centre of gravity position approved for take-off. The stopping force due to braking is equal to the braking coefficient multiplied by the normal load (i.e. weight) on each braked wheel. The portion of the aeroplane’s weight being supported by the unbraked wheels (e.g. unbraked nose wheels) does not contribute to the stopping force generated by the brakes. This effect must be taken into account for the most adverse centre of gravity position approved for take-off, considering any centre of gravity shifts that occur due to the dynamics of the stop. The most adverse centre of gravity position is the position that results in the least load on the braked wheels.

AMC 25.109(d)(2) Accelerate-stop distance: anti-skid efficiency on grooved and porous friction course (PFC) runways.

ED Decision 2003/2/RM

Properly designed, constructed and maintained grooved and PFC runways can offer significant improvements in wet runway braking capability. A conservative level of performance credit is provided by 25.109(d) to reflect this performance improvement and to provide an incentive for installing and maintaining such surfaces.

In accordance with CS 25.105(c) and 25.109(d), applicants may optionally determine the acceleratestop distance applicable to wet grooved and PFC runways. These data would be included in the AFM in addition to the smooth runway accelerate-stop distance data. The braking coefficient for determining the accelerate-stop distance on grooved and PFC runways is defined in CS 25.109(d) as either 70% of the braking coefficient used to determine the dry runway accelerate-stop distances, or a curve based on ESDU 71026 data and derived in a manner consistent with that used for smooth runways. In either case, the brake torque limitations determined on a dry runway may not be exceeded.

Using a simple factor applied to the dry runway braking coefficient is acceptable for grooved and PFC runways because the braking coefficient’s variation with speed is much lower on these types of runways. On smooth wet runways, the braking coefficient varies significantly with speed, which makes it inappropriate to apply a simple factor to the dry runway braking coefficient. For applicants who choose to determine the grooved/PFC wet runway accelerate-stop distances in a manner consistent with that used for smooth runways, CS 25.109(d)(2) provides the maximum tyre-to-ground braking coefficient applicable to grooved and PFC runways. This maximum tyre-to-ground braking coefficient must be adjusted for the anti-skid system efficiency, either by using the value specified in CS 25.109(c)(2) appropriate to the type of anti-skid system installed, or by using a specific efficiency established by the applicant. As anti-skid system performance depends on the characteristics of the runway surface, a system that has been tuned for optimum performance on a smooth surface may not achieve the same level of efficiency on a grooved or porous friction course runway, and vice versa. Consequently, if the applicant elects to establish a specific efficiency for use with grooved or PFC surfaces, anti-skid efficiency testing should be conducted on a wet runway with such a surface, in addition to testing on a smooth runway. Means other than flight testing may be acceptable, such as using the efficiency previously determined for smooth wet runways, if that efficiency is shown to be representative of, or conservative for, grooved and PFC runways. The resulting braking force for grooved/PFC wet runways must be adjusted for the effect of the distribution of the normal load between braked and unbraked wheels. This adjustment will be similar to that used for determining the braking force for smooth runways, except that the braking dynamics should be appropriate to the braking force achieved on grooved and PFC wet runways. Due to the increased braking force on grooved and PFC wet runways, an increased download on the nose wheel and corresponding reduction in the download on the main gear is expected.

AMC 25.109(f) Accelerate-stop distance: credit for reverse thrust.

ED Decision 2003/2/RM

In accordance with CS 25.109(f), reverse thrust may not be used to determine the accelerate-stop distances for a dry runway. For wet runway accelerate-stop distances, however, CS 25.109(f) allows credit for the stopping force provided by reverse thrust, if the requirements of CS 25.109(e) are met. In addition, the procedures associated with the use of reverse thrust, which CS 25.101(f) requires the applicant to provide, must meet the requirements of CS 25.101(h). The following criteria provide acceptable means of demonstrating compliance with these requirements:

1 Procedures for using reverse thrust during a rejected take-off must be developed and demonstrated. These procedures should include all of the pilot actions necessary to obtain the recommended level of reverse thrust, maintain directional control and safe engine operating characteristics, and return the reverser(s), as applicable, to either the idle or the stowed position. These procedures need not be the same as those recommended for use during a landing stop, but must not result in additional hazards, (e.g., cause a flame out or any adverse engine operating characteristics), nor may they significantly increase flightcrew workload or training needs.

2 It should be demonstrated that using reverse thrust during a rejected take-off complies with the engine operating characteristics requirements of CS 25.939(a). No adverse engine operating characteristics should be exhibited. The reverse thrust procedures may specify a speed at which the reverse thrust is to be reduced to idle in order to maintain safe engine operating characteristics.

3 The time sequence for the actions necessary to obtain the recommended level of reverse thrust should be demonstrated by flight test. The time sequence used to determine the accelerate-stop distances should reflect the most critical case relative to the time needed to deploy the thrust reversers. For example, on some aeroplanes the outboard thrust reversers are locked out if an outboard engine fails. This safety feature prevents the pilot from applying asymmetric reverse thrust on the outboard engines, but it may also delay the pilot’s selection of reverse thrust on the operable reversers. In addition, if the selection of reverse thrust is the fourth or subsequent pilot action to stop the aeroplane (e.g., after manual brake application, thrust/power reduction, and spoiler deployment), a one second delay should be added to the demonstrated time to select reverse thrust. (See figure 1 of AMC 25.101(h)(3).)

4 The response times of the affected aeroplane systems to pilot inputs should be taken into account. For example, delays in system operation, such as thrust reverser interlocks that prevent the pilot from applying reverse thrust until the reverser is deployed, should be taken into account. The effects of transient response characteristics, such as reverse thrust engine spin-up, should also be included.

5 To enable a pilot of average skill to consistently obtain the recommended level of reverse thrust under typical in-service conditions, a lever position that incorporates tactile feedback (e.g., a detent or stop) should be provided. If tactile feedback is not provided, a conservative level of reverse thrust should be assumed.

6 The applicant should demonstrate that exceptional skill is not required to maintain directional control on a wet runway with a 19 km/h (ten knot) crosswind from the most adverse direction. For demonstration purposes, a wet runway may be simulated by using a castering nosewheel on a dry runway. Symmetric braking should be used during the demonstration, and both all-engines-operating and critical-engine-inoperative reverse thrust should be considered. The brakes and thrust reversers may not be modulated to maintain directional control. The reverse thrust procedures may specify a speed at which the reverse thrust is reduced to idle in order to maintain directional controllability.

7 To meet the requirements of CS 25.101(h)(2) and 25.109(e)(1) the probability of failure to provide the recommended level of reverse thrust should be no greater than 1 per 1000 selections. The effects of any system or component malfunction or failure should not create an additional hazard.

8 The number of thrust reversers used to determine the wet runway accelerate-stop distance data provided in the AFM should reflect the number of engines assumed to be operating during the rejected take-off along with any applicable system design features. The all-engines-operating accelerate-stop distances should be based on all thrust reversers operating. The one-engine-inoperative accelerate-stop distances should be based on failure of the critical engine. For example, if the outboard thrust reversers are locked out when an outboard engine fails, the one-engine-inoperative accelerate stop distances can only include reverse thrust from the inboard engine thrust reversers.

9 For the engine failure case, it should be assumed that the thrust reverser does not deploy (i.e., no reverse thrust or drag credit for deployed thrust reverser buckets on the failed engine).

10 For approval of dispatch with one or more inoperative thrust reverser(s), the associated performance information should be provided either in the Aeroplane Flight Manual or the Master Minimum Equipment List.

11 The effective stopping force provided by reverse thrust in each, or at the option of the applicant, the most critical take-off configuration, should be demonstrated by flight test. Flight test demonstrations should be conducted to substantiate the accelerate-stop distances, and should include the combined use of all the approved means for stopping the aeroplane. These demonstrations may be conducted on a dry runway.

12 For turbo-propeller powered aeroplanes, the criteria of paragraphs 1 to 11 above remain generally applicable. Additionally, the propeller of the inoperative engine should be in the position it would normally assume when an engine fails and the power lever is closed. Reverse thrust may be selected on the remaining engine(s). Unless this is achieved by a single action to retard the power lever(s) from the take-off setting without encountering a stop or lockout, it must be regarded as an additional pilot action for the purposes of assessing delay times. If this is the fourth or subsequent pilot action to stop the aeroplane, a one second delay should be added to the demonstrated time to select reverse thrust.

CS 25.111 Take-off path

ED Decision 2015/008/R

(See AMC 25.111)

(a) The take-off path extends from a standing start to a point in the take-off at which the aeroplane is 457 m (1500 ft) above the take-off surface, or at which the transition from the take-off to the en-route configuration is completed and VFTO is reached, whichever point is higher. In addition –

(1) The take-off path must be based on the procedures prescribed in CS 25.101(f);

(2) The aeroplane must be accelerated on the ground to VEF, at which point the critical engine must be made inoperative and remain inoperative for the rest of the take-off; and

(3) After reaching VEF, the aeroplane must be accelerated to V2.

(b) During the acceleration to speed V2, the nose gear may be raised off the ground at a speed not less than VR. However, landing gear retraction may not be begun until the aeroplane is airborne. (See AMC 25.111(b).)

(c) During the take-off path determination in accordance with sub-paragraphs (a) and (b) of this paragraph –

(1) The slope of the airborne part of the take-off path must be positive at each point;

(2) The aeroplane must reach V2 before it is 11 m (35 ft) above the take-off surface and must continue at a speed as close as practical to, but not less than V2 until it is 122 m (400 ft) above the take-off surface;

(3) At each point along the take-off path, starting at the point at which the aeroplane reaches 122 m (400 ft) above the take-off surface, the available gradient of climb may not be less than –

(i) 1·2% for two-engined aeroplanes;

(ii) 1·5% for three-engined aeroplanes; and

(iii) 1·7% for four-engined aeroplanes,

(4) The aeroplane configuration may not be changed, except for gear retraction and automatic propeller feathering, and no change in power or thrust that requires action by the pilot may be made, until the aeroplane is 122 m (400 ft) above the take-off surface, and

(5) If CS 25.105(a)(2) requires the take-off path to be determined for flight in icing conditions, the airborne part of the take-off must be based on the aeroplane drag:

(i) With the most critical of the “Take-off Ice” accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), from a height of 11 m (35 ft) above the take-off surface up to the point where the aeroplane is 122 m (400 ft) above the take-off surface; and

(ii) With the most critical of the “Final Take-off Ice” accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), from the point where the aeroplane is 122 m (400 ft) above the take-off surface to the end of the take-off path.

 (d) The take-off path must be determined by a continuous demonstrated take-off or by synthesis from segments. If the take-off path is determined by the segmental method –

(1) The segments must be clearly defined and must relate to the distinct changes in the configuration, power or thrust, and speed;

(2) The weight of the aeroplane, the configuration, and the power or thrust must be constant throughout each segment and must correspond to the most critical condition prevailing in the segment;

(3) The flight path must be based on the aeroplane’s performance without ground effect; and

(4) The take-off path data must be checked by continuous demonstrated take-offs up to the point at which the aeroplane is out of ground effect and its speed is stabilised, to ensure that the path is conservative to the continuous path.

The aeroplane is considered to be out of the ground effect when it reaches a height equal to its wing span.

(e) Not required for CS-25.

[Amdt 25/3]

[Amdt 25/16]

AMC 25.111 Take-off path

ED Decision 2003/2/RM

The height references in CS 25.111 should be interpreted as geometrical heights.

AMC 25.111(b) Take-off path

ED Decision 2003/2/RM

1 Rotation speed, VR, is intended to be the speed at which the pilot initiates action to raise the nose gear off the ground, during the acceleration to V2; consequently, the take-off path determination, in accordance with CS 25.111(a) and (b), should assume that pilot action to raise the nose gear off the ground will not be initiated until the speed VR has been reached.

2 The time between lift-off and the initiation of gear retraction during take-off distance demonstrations should not be less than that necessary to establish an indicated positive rate of climb plus one second. For the purposes of flight manual expansion, the average demonstrated time delay between lift-off and initiation of gear retraction may be assumed; however, this value should not be less than 3 seconds.

CS 25.113 Take-off distance and take-off run

ED Decision 2016/010/R

(See AMC 25.113)

(a) Take-off distance on a dry runway is the greater of –

(1) The horizontal distance along the take-off path from the start of the take-off to the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined under CS 25.111 for a dry runway; or

(2) 115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to the point at which the aeroplane is 11 m (35 ft) above the take-off surface, as determined by a procedure consistent with CS 25.111. (See AMC 25.113(a)(2), (b)(2) and (c)(2).)

(b) Take-off distance on a wet runway is the greater of –

(1) The take-off distance on a dry runway determined in accordance with sub-paragraph (a) of this paragraph; or

(2) The horizontal distance along the take-off path from the start of the take-off to the point at which the aeroplane is 4,6 m (15 ft) above the take-off surface, achieved in a manner consistent with the achievement of V2 before reaching 11 m (35 ft) above the take-off surface, determined under CS 25.111 for a wet runway. (See AMC 25.113(a)(2), (b)(2) and (c)(2).)

(c) If the take-off distance does not include a clearway, the take-off run is equal to the take-off distance. If the take-off distance includes a clearway –

(1) The take-off run on a dry runway is the greater of –

(i) The horizontal distance along the take-off path from the start of the takeoff to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, as determined under CS 25.111 for a dry runway; or

(ii) 115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS 25.111. (See AMC 25.113(a)(2), (b)(2) and (c)(2).)

(2) The take-off run on a wet runway is the greater of –

(i) The horizontal distance along the take-off path from the start of the takeoff to the point at which the aeroplane is 4,6 m (15 ft) above the take-off surface, achieved in a manner consistent with the achievement of V2 before reaching 11 m (35 ft) above the take-off surface, determined under CS 25.111 for a wet runway; or

(ii) 115% of the horizontal distance along the take-off path, with all engines operating, from the start of the take-off to a point equidistant between the point at which VLOF is reached and the point at which the aeroplane is 11 m (35 ft) above the take-off surface, determined by a procedure consistent with CS 25.111. (See AMC 25.113(a)(2),(b)(2) and (c)(2))

[Amdt 25/9]

[Amdt 25/18]

AMC 25.113(a)(2), (b)(2) and (c)(2) Take-off distance and take-off run

ED Decision 2003/2/RM

In establishment of the take-off distance and take-off run, with all engines operating, in accordance with CS 25.113(a), (b) and (c), the flight technique should be such that –

a. A speed of not less than V2 is achieved before reaching a height of 11 m (35 ft) above the take-off surface,

b. It is consistent with the achievement of a smooth transition to a steady initial climb speed of not less than V2 + 19 km/h (10 kt) at a height of 122 m (400 ft) above the take-off surface.

CS 25.115 Take-off flight path

ED Decision 2003/2/RM

(a) The take-off flight path must be considered to begin 11 m (35 ft) above the take-off surface at the end of the take-off distance determined in accordance with CS 25.113(a) or (b) as appropriate for the runway surface condition.

(b) The net take-off flight path data must be determined so that they represent the actual take-off flight paths (determined in accordance with CS 25.111 and with sub-paragraph (a) of this paragraph) reduced at each point by a gradient of climb equal to –

(1) 0·8% for two-engined aeroplanes;

(2) 0·9% for three-engined aeroplanes; and

(3) 1·0% for four-engined aeroplanes.

(c) The prescribed reduction in climb gradient may be applied as an equivalent reduction in acceleration along that part of the take-off flight path at which the aeroplane is accelerated in level flight.

CS 25.117 Climb: general

ED Decision 2003/2/RM

Compliance with the requirements of CS 25.119 and 25.121 must be shown at each weight, altitude, and ambient temperature within the operational limits established for the aeroplane and with the most unfavourable centre of gravity for each configuration.

CS 25.119 Landing climb: all engines operating

ED Decision 2016/010/R

(See AMC 25.119)

In the landing configuration, the steady gradient of climb may not be less than 3·2%, with the engines at the power or thrust that is available 8 seconds after initiation of movement of the power or thrust controls from the minimum flight idle to the go-around power or thrust setting; and

(a) In non-icing conditions, with a climb speed of VREF determined in accordance with CS 25.125(b)(2)(i); and

(b) In icing conditions with the  most critical of the “Landing Ice” accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), and with a climb speed of VREF determined in accordance with CS 25.125(b)(2)(i).

[Amdt 25/3]

[Amdt 25/16]

[Amdt 25/18]

AMC 25.119 Landing climb: all-engines-operating

ED Decision 2020/024/R

In establishing the thrust specified in CS 25.119, either –

a. Engine acceleration tests should be conducted using the most critical combination of the following parameters:

i. Altitude;

ii. Airspeed;

iii.  Engine bleed;

iv. Engine power off-take;

likely to be encountered during an approach to a landing airfield within the altitude range for which landing certification is sought; or

b. The thrust specified in CS 25.119 should be established as a function of these parameters.

For aeroplanes equipped with a reduced go-around (RGA) thrust or power function, the climb requirements specified in CS 25.119 are applicable with the RGA function active. During the determination of the maximum thrust or power specified in AMC 25.119 a. and b. the thrust or power controls should be moved to the RGA thrust or power setting. This is consistent with an AFM all‑engines-operating go-around procedure which recommends the use of an RGA function (see AMC 25.143(b)(4)). In exceptional circumstances such as in the presence of wind shear or of unplanned obstacles, the flight crew may elect to use go-around thrust or power that exceeds the RGA setting. However, the applicant is not required to provide AFM climb gradient performance for this situation.

If an AFM go-around procedure is approved to use thrust or power above the RGA setting, then the climb requirements of CS 25.119 will apply at the higher thrust or power setting.

[Amdt 25/3]

[Amdt 25/26]

CS 25.121 Climb: one-engine-inoperative

ED Decision 2015/008/R

(See AMC 25.121)

(a) Take-off; landing gear extended. (See AMC 25.121(a).) In the critical take-off configuration existing along the flight path (between the points at which the aeroplane reaches VLOF and at which the landing gear is fully retracted) and in the configuration used in CS 25.111 but without ground effect, the steady gradient of climb must be positive for two-engined aeroplanes, and not less than 0·3% for three-engined aeroplanes or 0·5% for fourengined aeroplanes, at VLOF and with –

(1) The critical engine inoperative and the remaining engines at the power or thrust available when retraction of the landing gear is begun in accordance with CS 25.111 unless there is a more critical power operating condition existing later along the flight path but before the point at which the landing gear is fully retracted (see AMC 25.121(a)(1)); and

(2) The weight equal to the weight existing when retraction of the landing gear is begun determined under CS 25.111.

(b) Take-off; landing gear retracted. In the take-off configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in CS 25.111 but without ground effect,

(1) the steady gradient of climb may not be less than 2·4% for two-engined aeroplanes, 2·7% for three-engined aeroplanes and 3·0% for four-engined aeroplanes, at V2 with –

(i) The critical engine inoperative, the remaining engines at the take-off power or thrust available at the time the landing gear is fully retracted, determined under CS 25.111, unless there is a more critical power operating condition existing later along the flight path but before the point where the aeroplane reaches a height of 122 m (400 ft) above the take-off surface (see AMC 25.121(b)(1)(i)) ; and

(ii) The weight equal to the weight existing when the aeroplane’s landing gear is fully retracted, determined under CS 25.111.

(2) The requirements of sub-paragraph (b)(1) of this paragraph must be met:

(i) In non-icing conditions; and

(ii) In icing conditions with the most critical of the  “Take-off Ice” accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), if in the configuration used to show compliance with CS 25.121(b) with this “Take-off Ice” accretion:

(A) The stall speed at maximum take-off weight exceeds that in non-icing conditions by more than the greater of 5.6 km/h (3 knots) CAS or 3% of VSR; or

(B) The degradation of the gradient of climb determined in accordance with CS 25.121(b) is greater than one-half of the applicable actual-to-net take-off flight path gradient reduction defined in CS 25.115(b).

(c) Final take-off. In the en-route configuration at the end of the take-off path determined in accordance with CS 25.111:

(1) the steady gradient of climb may not be less than 1·2% for two-engined aeroplanes, 1·5% for three-engined aeroplanes, and 1·7% for four-engined aeroplanes, at VFTO and with –

(i) The critical engine inoperative and the remaining engines at the available maximum continuous power or thrust; and

(ii) The weight equal to the weight existing at the end of the take-off path, determined under CS 25.111.

(2) The requirements of sub-paragraph (c)(1) of this paragraph must be met:

(i) In non-icing conditions; and

(ii) In icing conditions with themost critical of the “Final Take-off Ice” accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), if in the configuration used to show compliance with CS 25.121(b) with this “Take-off Ice” accretion:

(A) The stall speed at maximum take-off weight exceeds that in non-icing conditions by more than the greater of 5.6 km/h (3 knots) CAS or 3% of VSR; or

(B) The degradation of the gradient of climb determined in accordance with CS 25.121(b) is greater than one-half of the applicable actual-to-net take-off flight path gradient reduction defined in CS 25.115(b).

(d) Approach. In a configuration corresponding to the normal all-engines-operating procedure in which VSR for this configuration does not exceed 110% of the VSR for the related all-engines-operating landing configuration:

(1) steady gradient of climb may not be less than 2·1% for two-engined aeroplanes, 2·4% for three-engined aeroplanes and 2·7% for four-engined aeroplanes, with –

(i) The critical engine inoperative, the remaining engines at the go-around power or thrust setting;

(ii) The maximum landing weight;

(iii) A climb speed established in connection with normal landing procedures, but not more than 1·4 VSR; and

(iv) Landing gear retracted.

(2) The requirements of sub-paragraph (d)(1) of this paragraph must be met:

(i) In non-icing conditions; and

(ii) In icing conditions with the most critical of the Approach Ice accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g). The climb speed selected for non-icing conditions may be used if the climb speed for icing conditions, computed in accordance with sub-paragraph (d)(1)(iii) of this paragraph, does not exceed that for non-icing conditions by more than the greater of 5.6 km/h (3 knots) CAS or 3%.

[Amdt 25/3]

[Amdt 25/16]

AMC 25.121 Climb: One-engine-inoperative

ED Decision 2003/2/RM

1 In showing compliance with CS 25.121 it is accepted that bank angles of up to 2° to 3° toward the operating engine(s) may be used.

2 The height references in CS 25.121 should be interpreted as geometrical heights.

AMC 25.121(a) Climb: One-engine-inoperative

ED Decision 2003/2/RM

The configuration of the landing gear used in showing compliance with the climb requirements of CS 25.121(a) may be that finally achieved following ‘gear down’ selection.

AMC 25.121(a)(1) Climb: One-engine-inoperative

ED Decision 2003/2/RM

A ‘power operating condition’ more critical than that existing at the time when retraction of the landing gear is begun would occur, for example, if water injection were discontinued prior to reaching the point at which the landing gear is fully retracted.

AMC 25.121(b)(1)(i) Climb: One-engine-inoperative

ED Decision 2007/010/R

A ‘power operating condition’ more critical than that existing at the time the landing gear is fully retracted would occur, for example, if water injection were discontinued prior to reaching a gross height of 122 m (400 ft).

[Amdt 25/3]

CS 25.123 En-route flight paths

ED Decision 2015/008/R

(See AMC 25.123)

(a) For the en-route configuration, the flight paths prescribed in sub-paragraphs (b) and (c) of this paragraph must be determined at each weight, altitude, and ambient temperature, within the operating limits established for the aeroplane. The variation of weight along the flight path, accounting for the progressive consumption of fuel and oil by the operating engines, may be included in the computation. The flight paths must be determined at a selected speed not less than VFTO, with –

(1) The most unfavourable centre of gravity;

(2) The critical engines inoperative;

(3) The remaining engines at the available maximum continuous power or thrust; and

(4) The means for controlling the engine-cooling air supply in the position that provides adequate cooling in the hot-day condition.

(b) The one-engine-inoperative net flight path data must represent the actual climb performance diminished by a gradient of climb of 1·1% for two-engined aeroplanes, 1·4% for three-engined aeroplanes, and 1·6% for four-engined aeroplanes.

(1) In non-icing conditions; and

(2) In icing conditions with the “En-route Ice” accretion defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), if:

(i) A speed of 1.18VSR with the most critical of the “En-route Ice ” accretion(s) exceeds the en-route speed selected in non-icing conditions by more than the greater of 5.6 km/h (3 knots) CAS or 3% of VSR, or

(ii) The degradation of the gradient of climb is greater than one-half of the applicable actual-to-net flight path reduction defined in sub-paragraph (b) of this paragraph.

(c) For three- or four-engined aeroplanes, the two-engine-inoperative net flight path data must represent the actual climb performance diminished by a gradient climb of 0·3% for three-engined aeroplanes and 0·5% for four-engined aeroplanes.

[Amdt 25/3]

[Amdt 25/16]

AMC 25.123 En-route flight paths

ED Decision 2003/2/RM

If, in showing compliance with CS 25.123, any credit is to be taken for the progressive use of fuel by the operating engines, the fuel flow rate should be assumed to be 80% of the engine specification flow rate at maximum continuous power, unless a more appropriate figure has been substantiated by flight tests.

CS 25.125 Landing

ED Decision 2016/010/R

(a) The horizontal distance necessary to land and to come to a complete stop from a point 15 m (50 ft) above the landing surface must be determined (for standard temperatures, at each weight, altitude and wind within the operational limits established by the applicant for the aeroplane):

(1) In non-icing conditions; and

(2) In icing conditions with the most critical of the  “Landing Ice” accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), if VREF for icing conditions exceeds VREF for non-icing conditions by more than 9.3 km/h (5 knots) CAS at the maximum landing weight

(b) In determining the distance in (a):

(1) The aeroplane must be in the landing configuration.

(2) A stabilised approach, with a calibrated airspeed of not less than VREF, must be maintained down to the 15 m (50 ft) height.

(i) In non-icing conditions, VREF may not be less than:

(A) 1.23 VSR0;

(B) VMCL established under CS25.149(f); and

(C) A speed that provides the manoeuvring capability specified in CS 25.143(h).

(ii) In icing conditions, VREF may not be less than:

(A) The speed determined in sub-paragraph (b)(2)(i) of this paragraph;

(B) 1.23 VSR0 with the most critical of the "Landing Ice" accretion(s) defined in Appendices C and O, as applicable, in accordance with CS 25.21(g), if that speed exceeds VREF for non-icing conditions by more than 9.3 km/h (5 knots) CAS; and

(C) A speed that provides the manoeuvring capability specified in CS 25.143(h) with the most critical of the “ Landing ice accretion(s) defined in appendices C and O, as applicable, in accordance with CS 25.21(g).

(3) Changes in configuration, power or thrust, and speed, must be made in accordance with the established procedures for service operation. (See AMC 25.125(b)(3).)

(4) The landing must be made without excessive vertical acceleration, tendency to bounce, nose over or ground loop.

(5) The landings may not require exceptional piloting skill or alertness.

(c) The landing distance must be determined on a level, smooth, dry, hard-surfaced runway. (See AMC 25.125(c).) In addition –

(1) The pressures on the wheel braking systems may not exceed those specified by the brake manufacturer;

(2) The brakes may not be used so as to cause excessive wear of brakes or tyres (see AMC 25.125(c)(2)); and

(3) Means other than wheel brakes may be used if that means –

(i)  Is safe and reliable;

(ii) Is used so that consistent results can be expected in service; and

(iii) Is such that exceptional skill is not required to control the aeroplane.

(d) Reserved.

(e) Reserved.

(f) The landing distance data must include correction factors for not more than 50% of the nominal wind components along the landing path opposite to the direction of landing, and not less than 150% of the nominal wind components along the landing path in the direction of landing.

(g) If any device is used that depends on the operation of any engine, and if the landing distance would be noticeably increased when a landing is made with that engine inoperative, the landing distance must be determined with that engine inoperative unless the use of compensating means will result in a landing distance not more than that with each engine operating.

[Amdt 25/3]

[Amdt 25/16]

[Amdt 25/18]

AMC 25.125(b)(3) Change of Configuration

ED Decision 2007/010/R

No changes in configuration, addition of thrust, or nose depression should be made after reaching 15 m (50 ft) height.

[Amdt 25/3]

AMC 25.125(c) Landing

ED Decision 2007/010/R

1 During measured landings, if the brakes can be consistently applied in a manner permitting the nose gear to touch down safely, the brakes may be applied with only the main wheels firmly on the ground. Otherwise, the brakes should not be applied until all wheels are firmly on the ground.

2 This is not intended to prevent operation in the normal way of automatic braking systems which, for instance, permit brakes to be selected on before touchdown.

[Amdt 25/3]

AMC 25.125(c)(2) Landing

ED Decision 2007/010/R

To ensure compliance with CS 25.125(c)(2), a series of six measured landings should be conducted on the same set of wheel brakes and tyres.

[Amdt 25/3]