Certification Specifications for Large Aeroplanes（CS-25）

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CS-25 BOOK 1

(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 subparagraphs (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 oneengine-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-enginesoperating condition and 104%

of VMU determined at the

thrust-to-weight ratio

corresponding to the oneengine-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 allengines-operating take-off provisions.

(3) It must be shown that the one-engineinoperative 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 overrotation of the aeroplane and out-of-trim

conditions) may not result in unsafe flight

characteristics or in marked increases in the

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CS-25 BOOK 1

scheduled take-off distances established in

accordance with CS 25.113(a). (See AMC No. 1

to CS25.107 (e) (4) and AMC No. 2 to CS25.107

(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 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. No.:25/3]

CS 25.109 Accelerate-stop distance

(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 subparagraph (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 subparagraph (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):

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.

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(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 subparagraph (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-toground wet runway braking coefficient of friction

is defined as (see 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.

Tyre Pressure (psi) Maximum Braking Coefficient (tyre-to-ground)

50 ( ) ( ) ( )

μt/gMAX

=−⋅+ ⋅−⋅+ ⋅0 0350

100

0 306

100

0 851

100

0 883

3 2

V V V

100 ( ) ( ) ( )

μt/gMAX

=−⋅+ ⋅−⋅+ ⋅0 0437

100

0 320

100

0 805

100

0 804

3 2

V V V

200 ( ) ( ) ( )

μt/gMAX

=−⋅+ ⋅−⋅+ ⋅0 0331

100

0 252

100

0 658

100

0 692

3 2

V V V

300 ( ) ( ) ( )

μt/gMAX

=−⋅+ ⋅−⋅+ ⋅0 0401

100

0 263

100

0 611

100

0 614

3 2

V V V

Figure 1

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Tyre Pressure(psi) Maximum Braking Coefficient (tyre-to-ground)

50 () ( ) ( ) ( ) ()

μt/gMAX

=⋅−⋅+⋅−⋅+⋅+⋅0 147

100

1 05

100

2 673

100

2 683

100

0 403

100

0 859

5 4 3 2

V V V V V

100 () ( ) ( ) ( ) ()

μt/gMAX

=⋅−⋅+⋅−⋅+⋅+⋅0 1106

100

0 813

100

2 13

100

2 20

100

0 317

100

0 807

5 4 3 2

V V V V V

200 () ( ) ( ) ( ) ()

μt/gMAX

= ⋅−⋅+⋅−⋅+⋅+ 0 0498

100

0 398

100

1 14

100

1 285

100

0 140

100

0 701

5 4 3 2

V V V V V

.

300 () ( ) ( ) ( ) ()

μt/gMAX

=⋅−⋅+⋅−⋅−⋅+⋅0 0314

100

0 247

100

0 703

100

0 779

100

0 00954

100

0 614

5 4 3 2

V V V V V

Figure 2

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CS-25 BOOK 1

(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.

CS 25.111 Take-off path

(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 takeoff 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 “Take-off Ice”

accretion defined in Appendix C, 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 “Final Take-off Ice”

accretion defined in Appendix C, 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

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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. No.:25/3]

CS 25.113 Take-off distance and takeoff run

(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 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).)

CS 25.115 Take-off flight path

(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

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CS-25 BOOK 1

CS25.111 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

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-enginesoperating

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 goaround power or thrust setting (see AMC 25.119);

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 “Landing Ice”

accretion defined in Appendix C, and with a climb

speed of VREF determined in accordance with CS

25.125(b)(2)(ii).

[Amdt. No.:25/3]

CS 25.121 Climb: one-engineinoperative

(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

“Take-off Ice” accretion defined in

Appendix C, if in the configuration of CS

25.121(b) with the “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).

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(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 the

“Final Take-off Ice” accretion defined in

Appendix C, if in the configuration of CS

25.121(b) with the “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) The 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

Approach Ice accretion defined in Appendix

C. 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 nonicing conditions by more than the greater of

5.6 km/h (3 knots) CAS or 3%.

[Amdt. No.:25/3]

CS 25.123 En-route flight paths

(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 –

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(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 enginecooling 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 twoengined 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 Appendix C, if:

(i) A speed of 1.18VSR with the

“En-route Ice ” accretion exceeds the enroute 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.

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(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. No.:25/3]

CS 25.125 Landing

(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 “Landing

Ice” accretion defined in Appendix C 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

CS25.143(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

"Landing Ice" accretion defined in

Appendix C 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 landing ice

accretion defined in appendix C.

(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. No.:25/3]

CONTROLLABILITY AND

MANOEUVRABILITY

CS 25.143 General

(a) (See AMC 25.143(a).) The aeroplane must

be safely controllable and manoeuvrable during –

(1) Take-off;

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(2) Climb;

(3) Level flight;

(4) Descent; and

(5) Landing.

(b) (See AMC 25.143(b).) It must be possible to

make a smooth transition from one flight condition to

any other flight condition without exceptional

piloting skill, alertness, or strength, and without

danger of exceeding the aeroplane limit-load factor

under any probable operating conditions, including –

(1) The sudden failure of the critical

engine. (See AMC 25.143(b)(1).)

(2) For aeroplanes with three or more

engines, the sudden failure of the second critical

engine when the aeroplane is in the en-route,

approach, or landing configuration and is trimmed

with the critical engine inoperative; and

(3) Configuration changes, including

deployment or retraction of deceleration devices.

(c) The aeroplane must be shown to be safely

controllable and manoeuvrable with the critical ice

accretion appropriate to the phase of flight defined in

appendix C, and with the critical engine inoperative

and its propeller (if applicable) in the minimum drag

position:

(1) At the minimum V2 for take-off;

(2) During an approach and go-around;

and

(3) During an approach and landing.

(d) The following table prescribes, for

conventional wheel type controls, the maximum

control forces permitted during the testing required

by sub-paragraphs (a) through (c) of this paragraph.

(See AMC 25.143(d)):

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Force, in newton (pounds),

applied to the control wheel or

rudder pedals

Pitch Roll Yaw

For short term application for

pitch and roll control – two

hands available for control

334

(75)

222

(50)

–

For short term application for

pitch and roll control – one

hand available for control

222

(50)

111

(25)

–

For short term application for

yaw control

– – 667

(150)

For long term application 44,5

(10)

22 (5) 89

(20)

(e) Approved operating procedures or

conventional operating practices must be followed

when demonstrating compliance with the control

force limitations for short term application that are

prescribed in sub-paragraph (d) of this paragraph.

The aeroplane must be in trim, or as near to being in

trim as practical, in the immediately preceding steady

flight condition. For the take-off condition, the

aeroplane must be trimmed according to the approved

operating procedures.

(f) When demonstrating compliance with the

control force limitations for long term application

that are prescribed in sub-paragraph (d) of this

paragraph, the aeroplane must be in trim, or as near

to being in trim as practical.

(g) When manoeuvring at a constant airspeed or

Mach number (up to VFC/MFC), the stick forces and

the gradient of the stick force versus manoeuvring

load factor must lie within satisfactory limits. The

stick forces must not be so great as to make excessive

demands on the pilot’s strength when manoeuvring

the aeroplane (see AMC No. 1 to CS 25.143 (g)), and

must not be so low that the aeroplane can easily be

overstressed inadvertently. Changes of gradient that

occur with changes of load factor must not cause

undue difficulty in maintaining control of the

aeroplane, and local gradients must not be so low as

to result in a danger of over-controlling. (See AMC

No. 2 to CS 25.143 (g)).

(h) (See AMC 25.143(h)). The manoeuvring

capabilities in a constant speed coordinated turn at

forward centre of gravity, as specified in the

following table, must be free of stall warning or other

characteristics that might interfere with normal

manoeuvring.

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(1)

A combination of weight, altitude and

temperature (WAT) such that the thrust or power

setting produces the minimum climb gradient

specified in CS 25.121 for the flight condition.

(2)

Airspeed approved for all-enginesoperating initial climb.

(3)

That thrust or power setting which, in

the event of failure of the critical engine and without

any crew action to adjust the thrust or power of the

remaining engines, would result in the thrust or

power specified for the take-off condition at V2, or

any lesser thrust or power setting that is used for allengines-operating initial climb procedures.

(i) When demonstrating compliance with CS

25.143 in icing conditions -

(1) Controllability must be demonstrated

with the ice accretion described in Appendix C,

that is most critical for the particular flight phase.

(2) It must be shown that a push force is

required throughout a pushover manoeuvre down

to a zero g load factor, or the lowest load factor

obtainable if limited by elevator power or other

design characteristic of the flight control system.

It must be possible to promptly recover from the

manoeuvre without exceeding a pull control force

of 222 N. (50 lbf); and

(3) Any changes in force that the pilot

must apply to the pitch control to maintain speed

with increasing sideslip angle must be steadily

increasing with no force reversals, unless the

change in control force is gradual and easily

controllable by the pilot without using exceptional

piloting skill, alertness, or strength.

(j) For flight in icing conditions before the ice

protection system has been activated and is

performing its intended function, the following

requirements apply:

(1) If activating the ice protection system

depends on the pilot seeing a specified ice

accretion on a reference surface (not just the first

indication of icing), the requirements of CS

25.143 apply with the ice accretion defined in

appendix C, part II(e).

(2) For other means of activating the ice

protection system, it must be demonstrated in

flight with the ice accretion defined in appendix

C, part II(e) that:

(i) The aeroplane is controllable in

a pull-up manoeuvre up to 1.5 g load factor;

and

(ii) There is no pitch control force

reversal during a pushover manoeuvre down

to 0.5 g load factor.

[Amdt. No.:25/3]

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CS 25.145 Longitudinal control

(a) (See AMC 25.145(a).) It must be possible

at any point between the trim speed prescribed in CS

25.103(b)(6) and stall identification (as defined in CS

25.201(d)), to pitch the nose downward so that the

acceleration to this selected trim speed is prompt

with –

(1) The aeroplane trimmed at the trim

speed prescribed in CS 25.103(b)(6);

(2) The landing gear extended;

(3) The wing-flaps (i) retracted and (ii)

extended; and

(4) Power (i) off and (ii) at maximum

continuous power on the engines.

(b) With the landing gear extended, no change

in trim control, or exertion of more than 222 N (50

pounds) control force (representative of the

maximum short term force that can be applied readily

by one hand) may be required for the following

manoeuvres:

(1) With power off, wing-flaps retracted,

and the aeroplane trimmed at 1·3 VSR1 , extend the

CONFIGURATION SPEED MANOEUVRING BANK

ANGLE IN A

COORDINATED TURN

THRUST/POWER

SETTING

TAKE-OFF V2 30° ASYMMETRIC WAT-LIMITED

(1)

TAKE-OFF V2 + xx

(2)

40° ALL ENGINES OPERATING CLIMB

(3)

EN-ROUTE VFTO 40° ASYMMETRIC WAT-LIMITED

(1)

LANDING VREF 40° SYMMETRIC FOR –3° FLIGHT PATH

ANGLE

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wing-flaps as rapidly as possible while maintaining

the airspeed at approximately 30% above the

reference stall speed existing at each instant

throughout the manoeuvre. (See AMC 25.145(b)(1),

(b)(2) and (b)(3).)

(2) Repeat sub-paragraph (b)(1) of this

paragraph except initially extend the wing-flaps

and then retract them as rapidly as possible. (See

AMC 25.145(b)(2) and AMC 25.145(b)(1), (b)(2)

and (b)(3).)

(3) Repeat sub-paragraph (b)(2) of this

paragraph except at the go-around power or thrust

setting. (See AMC 25.145(b)(1), (b)(2) and

(b)(3).)

(4) With power off, wing-flaps retracted

and the aeroplane trimmed at 1·3 VSR1 , rapidly set

go-around power or thrust while maintaining the

same airspeed.

(5) Repeat sub-paragraph (b)(4) of this

paragraph except with wing-flaps extended.

(6) With power off, wing-flaps extended

and the aeroplane trimmed at 1·3 VSR1 obtain and

maintain airspeeds between VSW and either 1·6

VSR1 , or VFE, whichever is the lower.

(c) It must be possible, without exceptional

piloting skill, to prevent loss of altitude when

complete retraction of the high lift devices from any

position is begun during steady, straight, level flight

at 1·08 VSR1 , for propeller powered aeroplanes or

1·13 VSR1 , for turbo-jet powered aeroplanes, with –

(1) Simultaneous movement of the power

or thrust controls to the go-around power or thrust

setting;

(2) The landing gear extended; and

(3) The critical combinations of landing

weights and altitudes.

(d) Revoked

(e) (See AMC 25.145(e).) If gated high-lift

device control positions are provided, sub-paragraph

(c) of this paragraph applies to retractions of the

high-lift devices from any position from the

maximum landing position to the first gated position,

between gated positions, and from the last gated

position to the fully retracted position. The

requirements of sub-paragraph (c) of this paragraph

also apply to retractions from each approved landing

position to the control position(s) associated with the

high-lift device configuration(s) used to establish the

go-around procedure(s) from that landing position. In

addition, the first gated control position from the

maximum landing position must correspond with a

configuration of the high-lift devices used to

establish a go-around procedure from a landing

configuration. Each gated control position must

require a separate and distinct motion of the control

to pass through the gated position and must have

features to prevent inadvertent movement of the

control through the gated position. It must only be

possible to make this separate and distinct motion

once the control has reached the gated position.

CS 25.147 Directional and lateral

control

(a) Directional control; general. (See AMC

25.147(a).) It must be possible, with the wings level,

to yaw into the operative engine and to safely make a

reasonably sudden change in heading of up to 15º in

the direction of the critical inoperative engine. This

must be shown at 1·3 VSR1 , for heading changes up to

15º (except that the heading change at which the

rudder pedal force is 667 N (150 lbf) need not be

exceeded), and with –

(1) The critical engine inoperative and its

propeller in the minimum drag position;

(2) The power required for level flight at

1.3 VSR1 , but not more than maximum continuous

power;

(3) The most unfavourable centre of

gravity;

(4) Landing gear retracted;

(5) Wing-flaps in the approach position;

and

(6) Maximum landing weight.

(b) Directional control; aeroplanes with four or

more engines. Aeroplanes with four or more engines

must meet the requirements of sub-paragraph (a) of

this paragraph except that –

(1) The two critical engines must be

inoperative with their propellers (if applicable) in

the minimum drag position;

(2) Reserved; and

(3) The wing-flaps must be in the most

favourable climb position.

(c) Lateral control; general. It must be possible

to make 20º banked turns, with and against the

inoperative engine, from steady flight at a speed

equal to 1·3 VSR1 , with –

(1) The critical engine inoperative and its

propeller (if applicable) in the minimum drag

position;

(2) The remaining engines at maximum

continuous power;

(3) The most unfavourable centre of

gravity;

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(4) Landing gear both retracted and

extended;

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(5) Wing-flaps in the most favourable

climb position; and

(6) Maximum take-off weight;

(d) Lateral control; roll capability. With the

critical engine inoperative, roll response must allow

normal manoeuvres. Lateral control must be

sufficient, at the speeds likely to be used with one

engine inoperative, to provide a roll rate necessary

for safety without excessive control forces or travel.

(See AMC 25.147(d).)

(e) Lateral control; aeroplanes with four or

more engines. Aeroplanes with four or more engines

must be able to make 20º banked turns, with and

against the inoperative engines, from steady flight at

a speed equal to 1·3 VSR1 , with maximum continuous

power, and with the aeroplane in the configuration

prescribed by sub-paragraph (b) of this paragraph.

(f) Lateral control; all engines operating. With

the engines operating, roll response must allow

normal manoeuvres (such as recovery from upsets

produced by gusts and the initiation of evasive

manoeuvres). There must be enough excess lateral

control in sideslips (up to sideslip angles that might

be required in normal operation), to allow a limited

amount of manoeuvring and to correct for gusts.

Lateral control must be enough at any speed up to

VFC/MFC to provide a peak roll rate necessary for

safety, without excessive control forces or travel.

(See AMC 25.147(f).)

CS 25.149 Minimum control speed

(See AMC 25.149)

(a) In establishing the minimum control speeds

required by this paragraph, the method used to

simulate critical engine failure must represent the

most critical mode of powerplant failure with respect

to controllability expected in service.

(b) VMC is the calibrated airspeed, at which,

when the critical engine is suddenly made

inoperative, it is possible to maintain control of the

aeroplane with that engine still inoperative, and

maintain straight flight with an angle of bank of not

more than 5º.

(c) VMC may not exceed 1·13 VSR with –

(1) Maximum available take-off power or

thrust on the engines;

(2) The most unfavourable centre of

gravity;

(3) The aeroplane trimmed for take-off;

(4) The maximum sea-level take-off

weight (or any lesser weight necessary to show

VMC);

(5) The aeroplane in the most critical

take-off configuration existing along the flight

path after the aeroplane becomes airborne, except

with the landing gear retracted;

(6) The aeroplane airborne and the

ground effect negligible; and

(7) If applicable, the propeller of the

inoperative engine –

(i) Windmilling;

(ii) In the most probable position

for the specific design of the propeller

control; or

(iii) Feathered, if the aeroplane has

an automatic feathering device acceptable

for showing compliance with the climb

requirements of CS 25.121.

(d) The rudder forces required to maintain

control at VMC may not exceed 667 N (150 lbf) nor

may it be necessary to reduce power or thrust of the

operative engines. During recovery, the aeroplane

may not assume any dangerous attitude or require

exceptional piloting skill, alertness, or strength to

prevent a heading change of more than 20º.

(e) VMCG, the minimum control speed on the

ground, is the calibrated airspeed during the take-off

run at which, when the critical engine is suddenly

made inoperative, it is possible to maintain control of

the aeroplane using the rudder control alone (without

the use of nose-wheel steering), as limited by 667 N

of force (150 lbf), and the lateral control to the extent

of keeping the wings level to enable the take-off to

be safely continued using normal piloting skill. In the

determination of VMCG, assuming that the path of the

aeroplane accelerating with all engines operating is

along the centreline of the runway, its path from the

point at which the critical engine is made inoperative

to the point at which recovery to a direction parallel

to the centreline is completed, may not deviate more

than 9.1 m (30 ft) laterally from the centreline at any

point. VMCG must be established, with –

(1) The aeroplane in each take-off

configuration or, at the option of the applicant, in

the most critical take-off configuration;

(2) Maximum available take-off power or

thrust on the operating engines;

(3) The most unfavourable centre of

gravity;

The aeroplane trimmed for take-off; and

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(5) The most unfavourable weight in the

range of take-off weights. (See AMC 25.149(e).)

(f) (See AMC 25.149 (f)) VMCL, the minimum

control speed during approach and landing with all

engines operating, is the calibrated airspeed at which,

when the critical engine is suddenly made

inoperative, it is possible to maintain control of the

aeroplane with that engine still inoperative, and

maintain straight flight with an angle of bank of not

more than 5º. VMCL must be established with –

(1) The aeroplane in the most critical

configuration (or, at the option of the applicant,

each configuration) for approach and landing with

all engines operating;

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(2) The most unfavourable centre of

gravity;

(3) The aeroplane trimmed for approach

with all engines operating;

(4) The most unfavourable weight, or, at

the option of the applicant, as a function of

weight;

(5) For propeller aeroplanes, the propeller

of the inoperative engine in the position it

achieves without pilot action, assuming the engine

fails while at the power or thrust necessary to

maintain a 3 degree approach path angle; and

(6) Go-around power or thrust setting on

the operating engine(s).

(g) (See AMC 25.149(g)) For aeroplanes with

three or more engines, VMCL-2, the minimum control

speed during approach and landing with one critical

engine inoperative, is the calibrated airspeed at

which, when a second critical engine is suddenly

made inoperative, it is possible to maintain control of

the aeroplane with both engines still inoperative, and

maintain straight flight with an angle of bank of not

more than 5º. VMCL-2 must be established with –

(1) The aeroplane in the most critical

configuration (or, at the option of the applicant,

each configuration) for approach and landing with

one critical engine inoperative;

(2) The most unfavourable centre of

gravity;

(3) The aeroplane trimmed for approach

with one critical engine inoperative;

(4) The most unfavourable weight, or, at

the option of the applicant, as a function of

weight;

(5) For propeller aeroplanes, the propeller

of the more critical engine in the position it

achieves without pilot action, assuming the engine

fails while at the power or thrust necessary to

maintain a 3 degree approach path angle, and the

propeller of the other inoperative engine

feathered;

(6) The power or thrust on the operating

engine(s) necessary to maintain an approach path

angle of 3º when one critical engine is

inoperative; and

(7) The power or thrust on the operating

engine(s) rapidly changed, immediately after the

second critical engine is made inoperative, from

the power or thrust prescribed in sub-paragraph

(g)(6) of this paragraph to –

(i) Minimum power or thrust; and

(ii) Go-around power or thrust

setting.

(h) In demonstrations of VMCL and VMCL-2 –

(1) The rudder force may not exceed 667

N (150 lbf);

(2) The aeroplane may not exhibit

hazardous flight characteristics or require

exceptional piloting skill, alertness or strength;

(3) Lateral control must be sufficient to

roll the aeroplane, from an initial condition of

steady straight flight, through an angle of 20º in

the direction necessary to initiate a turn away

from the inoperative engine(s), in not more than 5

seconds (see AMC 25.149(h)(3)); and

(4) For propeller aeroplanes, hazardous

flight characteristics must not be exhibited due to

any propeller position achieved when the engine

fails or during any likely subsequent movements

of the engine or propeller controls (see AMC

25.149 (h)(4)).

TRIM

CS 25.161 Trim

(a) General. Each aeroplane must meet the trim

requirements of this paragraph after being trimmed,

and without further pressure upon, or movement of,

either the primary controls or their corresponding

trim controls by the pilot or the automatic pilot.

(b) Lateral and directional trim. The aeroplane

must maintain lateral and directional trim with the

most adverse lateral displacement of the centre of

gravity within the relevant operating limitations,

during normally expected conditions of operation

(including operation at any speed from 1·3 VSR1 , to

VMO/MMO).