3.1 RUNWAYS

• 3.1.1 General
• 3.1.2 Slopes on Runways
• 3.1.3 Strength of Runways
• 3.1.4 Surface of Runways
• 3.1.5 Runway Shoulders
• 3.1.6 Runway Strips
• 3.1.7 Runway End Safety Areas

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3.1.1 General

Number and Orientation of Runways

Introductory Note - Many factors affect the determination, siting and number of runways.

One important factor is the usability factor, as determined by the wind distribution, which is specified hereunder. Another important factor is the alignment of the runway to facilitate the provision of approaches conforming to the approach surface specifications of Chapter4. In AttachmentA, Section1, information is given concerning these and other factors.

When a new instrument runway is being located, particular attention needs to be given to areas over which aeroplanes will be required to fly when following instrument approach and missed approach procedures, so as to ensure that obstacles in these areas or other factors will not restrict the operation of the aeroplanes for which the runway is intended. Guidance on the development of instrument approach procedures is given in the manual, Criteria for the Development of Instrument Procedures, TP308.

3.1.1.1 Recommendation - The number and orientation of runways at an aerodrome should be such that the usability factor of the aerodrome is not less than 95per cent for the aeroplanes that the aerodrome is intended to serve.

Choice of maximum permissible cross-wind components

3.1.1.2 Recommendation - In the application of 3.1.1.1 it should be assumed that landing or take-off of aeroplanes is, in normal circumstances, precluded when the cross-wind component exceeds:

• 37km/h (20kts) in the case of aeroplanes whose reference field length is 1500m or over, except that when poor runway braking action owing to an insufficient longitudinal coefficient of friction is experienced with some frequency, a cross-wind component not exceeding 24km/h (13kt) should be assumed;
• 24km/h (13kts) in the case of aeroplanes whose reference field length is 1200m or up to but not including 1500m; and
• 19km/h (10kts) in the case of aeroplanes whose reference field length is less than 1200m.

Note - In AttachmentA, Section1, guidance is given on factors affecting the calculation of the estimate of the usability factor and allowances which may have to be made to take account of the effect of unusual circumstances.

Data to be used

3.1.1.3 Recommendation - The selection of data to be used for the calculation of the usability factor should be based on reliable wind distribution statistics that extend over as long a period as possible, preferably of not less than five years. The observations used should be made at least eight times daily and spaced at equal intervals of time.

Note - These winds are mean winds. Reference to the need for some allowance for gusty conditions is made in AttachmentA, Section1.

Location of Threshold

3.1.1.4 Recommendation - A threshold should normally be located at the extremity of a runway unless operational considerations justify the choice of another location.

3.1.1.5 Recommendation - When it is necessary to displace a threshold, either permanently or temporarily, from its normal location, account should be taken of the various factors which may have a bearing on the location of the threshold. Where this displacement is due to an unserviceable runway condition, a cleared and graded area of at least 60m in length should be available between the unserviceable area and the displaced threshold. Additional distance should also be provided to meet the requirements of the runway end safety area as appropriate.

Actual Length of Runways

Primary runway

3.1.1.6 Recommendation - Except as provided in 3.1.1.8, the actual runway length to be provided for a primary runway should be adequate to meet the operational requirements of the aeroplanes for which the runway is intended and should be not less than the longest length determined by applying the corrections for local conditions to the operations and performance characteristics of the relevant aeroplanes.

Note1 - This specification does not necessarily mean providing for operations by the critical aeroplane at its maximum mass.

Note2 - Both take-off and landing requirements need to be considered when determining the length of runway to be provided and the need for operations to be conducted in both directions of the runway.

Note3 - Local conditions that may need to be considered include elevation, temperature, runway slope, humidity and the runway surface characteristics.

Note4 - When performance data on aeroplanes for which the runway is intended are not known, guidance on the determination of the actual length of a primary runway by application of general correction factors is given in the ICAO Aerodrome Design Manual, Part1.

Secondary runway

3.1.1.7 Recommendation - The length of a secondary runway should be determined similarly to primary runways except that it needs only to be adequate for those aeroplanes which require to use that secondary runway in addition to the other runway or runways in order to obtain a usability factor of at least 95per cent.

Runways with stopways or clearways

3.1.1.8 Recommendation - Where a runway is associated with a stopway or clearway, an actual runway length less than that resulting from application of 3.1.1.6 or 3.1.1.7, as appropriate, may be considered satisfactory, but in such a case any combination of runway, stopway and clearway provided should permit compliance with the operational requirements for take-off and landing of the aeroplanes the runway is intended to serve.

Note - Guidance on use of stopways and clearways is given in AttachmentA, Section2.

Width of Runways

3.1.1.9 Recommendation - The width of a runway should be not less than the appropriate dimension specified in the following tabulation:

Code letter

Code number	A	B	C	D	E
1	15 m	18 m	23 m	-	-
2	23 m	23 m	30 m	-	-
3	30 m	30 m	30 m	45 m	-
4	-	-	45 m	45 m	60 m

3.1.1.10 Recommendation - The width of a precision approach runway should be not less than 30m where the code number is 1 or 2.

Note - The combinations of code numbers and letters for which widths are specified have been developed for typical aeroplane characteristics.

Separation of Parallel Runways

3.1.1.11 Standard - Where parallel runways are provided for simultaneous use under visual meteorological conditions only, the minimum distance between their centre lines shall be:

• 210m where the higher code number is 3 or 4;
• 150m where the higher code number is 2; and
• 120m where the higher code number 1.

3.1.1.12 Standard - Where parallel runways are provided for simultaneous operations under instrument meteorological conditions, the minimum separation distance between their centre lines shall be:

• 1300m for independent parallel approaches;
• 760m for dependent parallel approaches;
• 760m for independent parallel departures;
• 760m for segregated parallel operations;

except that for segregated parallel operations the specified separation distance:

1. may be decreased by 30m for each 150m that the arrival runway is staggered toward the arriving aircraft, to a minimum of 300m; and
   
2. shall be increased by 30m for each 150m that the arrival runway is staggered away from the arriving aircraft.

Note - Guidance on planning and conducting simultaneous operations on parallel or near-parallel instrument runways is contained in ICAO Circular207 - Simultaneous Operations on Parallel or Near-Parallel Instrument Runways (SOIR).

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3.1.2 Slopes on Runways

Longitudinal slopes

3.1.2.1 Standard - The slope computed by dividing the difference between the maximum and minimum elevation along the runway centre line by the runway length shall not exceed:

• 1.5per cent where the code number is 3 or 4; and
• 2.5per cent where the code number is 1 or 2.

3.1.2.2 Recommendation - The slope computed in para3.1.2.1 should be limited to 1.0per cent where the code number is 3 or 4 and 2.0per cent where the code number is 1 or 2.

3.1.2.3 Standard - Along no portion of a runway shall the longitudinal slope exceed:

• 1.25per cent where the code number is 4, except that for the first and last quarter of the length of the runway the longitudinal slope should not exceed 0.8per cent;
• 1.5per cent where the code number is 3, except that for the first and last quarter of the length of a precision approach runway categoryII or III the longitudinal slope should not exceed 0.8per cent; and
• 2per cent where the code number is 1 or 2.

Longitudinal slope changes

3.1.2.4 Recommendation - Where slope changes cannot be avoided, a slope change between two consecutive slopes should not exceed:

• 1.5per cent where the code number is 3 or 4; and
• 2per cent where the code number is 1 or 2.

Note - Guidance on slope changes before a runway is given in AttachmentA, Section3.

3.1.2.5 Recommendation - The transition from one slope to another should be accomplished by a curved surface with a rate of change not exceeding:

• 0.1per cent per 30m (minimum radius of curvature of 30000m) where the code number is 4;
• 0.2per cent per 30m (minimum radius of curvature of 15000m) where the code number is 3; and
• 0.4per cent per 30m (minimum radius of curvature of 7500m) where the code number is 1 or 2.

Sight Distance

3.1.2.6 Recommendation - Where slope changes cannot be avoided, they should be such that there will be an unobstructed line of sight from:

• any point3m above a runway to all other points3m above the runway within a distance of at least half the length of the runway where the code letter is C, D or E;
• any point2m above a runway to all other points2m above the runway within a distance of at least half the length of the runway where the code letter is B; and
• any point1.5m above a runway to all other points1.5m above the runway within a distance of at least half the length of the runway where the code letter is A.

Distance between slope changes

3.1.2.7 Recommendation - Undulations or appreciable changes in slopes located close together along a runway should be avoided. The distance between the points of intersection of two successive curves should not be less than:

1. the sum of the absolute numerical values of the corresponding slope changes multiplied by the appropriate value as follows:
   
   • 30000 m where the code number is 4;
   • 15000 m where the code number is 3; and
   • 5000 m where the code number is 1 or 2; or

b. 45 m;

whichever is greater.

Note - Guidance on implementing this specification is given in AttachmentA, Section3.

Transverse Slopes

3.1.2.8 Recommendation - To promote the most rapid drainage of water, the runway surface should, if practicable, be cambered except where a single crossfall from high to low in the direction of the wind most frequently associated with rain would ensure rapid drainage. The transverse slope should not exceed:

• 1.5per cent where the code letter is C, D or E; and
• 2per cent where the code letter is A or B;

nor be less than 1per cent except at runway or taxiway intersections where flatter slopes may be necessary.

3.1.2.9 Recommendation - For a cambered runway surface, the transverse slope on each side of the centre line should be symmetrical.

Note - On wet runways with cross-wind conditions the problem of aquaplaning from poor drainage is apt to be accentuated.

3.1.2.10 Recommendation - The transverse slope should be substantially the same throughout the length of a runway except at an intersection with another runway or a taxiway where an even transition should be provided taking account of the need for adequate drainage.

Note - Guidance on transverse slope is given in the ICAO Aerodrome Design Manual, Part3.

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3.1.3 Strength of Runways

3.1.3.1 Recommendation - A runway should be capable of withstanding the traffic of aeroplanes the runway is intended to serve.

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3.1.4 Surface of Runways

3.1.4.1 Standard - The surface of a runway shall be constructed without irregularities that would result in loss in friction characteristics or otherwise adversely affect the take-off or landing of an aeroplane.

Note1 - Surface irregularities may adversely affect the take-off or landing of an aeroplane by causing excessive bouncing, pitching, vibration, or other difficulties in the control of an aeroplane.

Note2 - Guidance on design tolerances and other information is given in AttachmentA, Section4. Additional guidance is included in the ICAO Aerodrome Design Manual, Part3.

3.1.4.2 Standard - The surface of a paved runway shall be so constructed as to provide good friction characteristics when the runway is wet.

3.1.4.3 Recommendation - Measurements of the friction characteristics of a new or resurfaced runway should be made with a continuous friction measuring device using self-wetting features in order to assure that the design objectives with respect to its friction characteristics have been achieved.

Note - Guidance on friction characteristics of new runway surfaces is given in the ICAO Airport Services Manual, Part2.

3.1.4.4 Recommendation - The average surface texture depth of a new surface should be not less than 1.0mm.

Note1 - This normally requires some form of special surface treatment.

Note2 - Guidance on methods used to measure surface texture is given in the ICAO Airport Services Manual, Part2.

3.1.4.5 Recommendation - When the surface is grooved or scored, the grooves or scorings should be either perpendicular to the runway centre line or parallel to non-perpendicular transverse joints, where applicable.

Note - Guidance on methods for improving the runway surface texture is given in the ICAO Aerodrome Design Manual, Part3.

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3.1.5 Runway Shoulders

General

Note - Guidance on characteristics and treatment of runway shoulders is given in AttachmentA, Section5, and in the ICAO Aerodrome Design Manual, Part2.

3.1.5.1 Recommendation - Runway shoulders should be provided for a runway where the code letter is D and the runway is intended to serve large turbo-jet aeroplanes.

Width of runway shoulders

3.1.5.2 Recommendation - The runway shoulders should extend symmetrically on each side of the runway so that the over-all width of the runway and its shoulders is not less than 60m.

Slopes on runway shoulders

3.1.5.3 Recommendation - The surface of the shoulder that abuts the runway should be flush with the surface of the runway and its transverse slope should not exceed 2.5per cent.

Strength of runway shoulders

3.1.5.4 Recommendation - A runway shoulder should be prepared or constructed so as to be capable, in the event of an aeroplane running off the runway, of supporting the aeroplane without inducing structural damage to the aeroplane and of supporting ground vehicles which may operate on the shoulder.

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3.1.6 Runway Strips

General

3.1.6.1 Standard - A runway and any associated stopways shall be included in a strip.

Length of runway strips

3.1.6.2 Standard - A strip shall extend before the threshold and beyond the end of the runway or stopway for a distance of at least:

• 60m where the code number is 2, 3 or 4;
• 60m where the code number is 1 and the runway is an instrument one; and
• 30m where the code number is 1 and the runway is a non-instrument one.

Width of runway strips

3.1.6.3 Standard - A strip including a precision approach runway shall extend laterally to a distance of at least:

• 150m where the code number is 3 or 4; and
• 75m where the code number is 1 or 2;

on each side of the centre line of the runway and its extended centre line throughout the length of the strip.

3.1.6.4 Standard - A strip including a non-precision approach runway shall extend laterally to a distance of at least:

• 150m where the code number is 4;
• 75m where the code number is 3; and
• 45m when the code number is 1 or 2;

on each side of the centre line of the runway and its extended centre line throughout the length of the strip.

3.1.6.5 Standard - A strip including a non-instrument runway shall extend on each side of the centre line of the runway and its extended centre line throughout the length of the strip, to a distance of at least:

• 75m where the code number is 4;
• 45m where the code number is 3; and
• 30m where the code number is 1 or 2.

Objects on runway strips

Note - See 8.6 for information regarding siting and construction of equipment and installations on runway strips.

3.1.6.6 Recommendation - An object situated on a runway strip which may endanger aeroplanes should be regarded as an obstacle and should, as far as practicable, be removed.

3.1.6.7 Standard - No fixed object, other than visual aids required for air navigation purposes and satisfying the relevant frangibility requirement in Chapter5, shall be permitted on a runway strip:

1. within 60m of the runway centre line of a precision approach runway categoryI, II or III where the code number is 3 or 4; or
   
2. within 45m of the runway centre line of a precision approach runway categoryI where the code number is 1 or 2.

3.1.6.8 Standard - No mobile object shall be permitted on the part of the runway strip specified in 3.1.6.7 during the use of the runway for landing or take-off except that equipment and radio equipped personnel associated with inflight inspections of navigation and landing aids are permitted on a runway strip within graded areas while flight inspections are being carried out.

Grading of runway strips

Note - Full compliance with the graded area requirements may in many cases impose an undue burden and be economically unreasonable, particularly for aerodromes in remote and isolated areas of sparse population. In such cases, an aeronautical study will be conducted to determine if a lesser graded area can be permitted.

3.1.6.9 Standard - That portion of a strip of a precision approach runway within a distance of at least:

• 90m where the code number is 4;
• 75m where the code number is 3;
• 45m where the code number is 2; and
• 30m where the code number is 1;

from the centre line of the runway and its extended centre line shall provide a graded area for aeroplanes which the runway is intended to serve in the event of an aeroplane running off the runway.

3.1.6.10 Standard - That portion of a strip of a non-precision approach runway within a distance of at least:

• 75m where the code number is 4;
• 45m where the code number is 3; and
• 23m where the code number is 1 or 2;

from the centre line of the runway and its extended centre line shall provide a graded area for aeroplanes which the runway is intended to serve in the event of an aeroplane running off the runway.

3.1.6.11 Standard - That portion of a strip of a non-instrument runway within a distance of at least:

• 60m where the code number is 4;
• 40m where the code number is 3;
• 23m where the code number is 2; and
• 19m where the code number is 1;

from the centre line of the runway and its extended centre line shall provide a graded area for aeroplanes which the runway is intended to serve in the event of an aeroplane running off the runway.

3.1.6.12 Standard - The surface of that portion of a strip that abuts a runway, shoulder or stopway shall be flush with the surface of the runway, shoulder or stopway.

3.1.6.13 Recommendation - That portion of a strip to at least 30m before a threshold should be prepared against blast erosion in order to protect a landing aeroplane from the danger of an exposed edge and should be capable of supporting snow removal and emergency vehicles.

Slopes on runway strips

Longitudinal slopes

3.1.6.14 Recommendation - A longitudinal slope along that portion of a strip to be graded should not exceed:

• 1.5per cent where the code number is 4;
• 1.75per cent where the code number is 3; and
• 2per cent where the code number is 1 or 2 .

Longitudinal slope changes

3.1.6.15 Recommendation - Slope changes on that portion of a strip to be graded should be as gradual as practicable and abrupt changes or sudden reversals of slopes avoided.

3.1.6.16 Recommendation - Slope changes before the threshold of a precision approach runway should be avoided or kept to a minimum on that portion of the strip within a distance of at least 30m on each side of the extended centre line of the runway. Where slope changes cannot be avoided on this portion, the rate of change between two consecutive slopes should not exceed 2per cent per 30m.

Transverse slopes

3.1.6.17 Recommendation - Transverse slopes on that portion of a strip to be graded should be adequate to prevent the accumulation of water on the surface but should not exceed:

• 2.5per cent where the code number is 3 or 4; and
• 3per cent where the code number is 1 or 2;

except that to facilitate drainage the slope for the first 3m outward from the runway, shoulder or stopway edge should be negative as measured in the direction away from the runway and may be as great as 5per cent.

3.1.6.18 Recommendation - The transverse slopes of any portion of a strip beyond that to be graded should not exceed an upward slope of 5per cent as measured in the direction away from the runway.

Drainage ditches

3.1.6.19 Standard - Drainage ditches, shall not be located within the graded portion of the strip. Where drainage ditches are located at the edge of the graded area, they shall be contoured in order to reduce structural damage in the event an aeroplane overruns the ditch.

3.1.6.20 Recommendation - Earth displaced by contouring of ditch sides, particularly on the side nearest the runway, should not significantly alter the transverse slopes.

3.1.6.21 Recommendation - Open ditches should have a side slope of 4units of horizontal measure to 1 unit of vertical measure. Open ditches should be graded and sodded for erosion control and ease of maintenance.

Strength of runway strips

3.1.6.22 Recommendation - That portion of the runway strip that is graded in accordance with para3.1.6.9, 3.1.6.10 and 3.1.6.11 should be so prepared or constructed as to minimize hazards arising from differences in load bearing capacity to aeroplanes which the runway is intended to serve in the event of an aeroplane running off the runway.

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3.1.7 Runway End Safety Areas

General

3.1.7.1 Recommendation - A runway end safety area should be provided at each end of a runway strip where the code number is 3 or 4.

Dimensions of runway end safety areas

3.1.7.2 Recommendation - A runway end safety area should extend from the end of a runway strip for as great a distance as practicable, but at least 90m.

3.1.7.3 Recommendation - The width of a runway end safety area should be at least twice that of the associated runway.

Objects on runway end safety areas

Note - See 8.6 for information regarding siting and construction of equipment and installations on runway end safety areas.

3.1.7.4 Recommendation - An object situated on a runway end safety area which may endanger aeroplanes should be regarded as an obstacle and should, as far as practicable, be removed.

Clearing and grading of runway end safety areas

3.1.7.5 Recommendation - A runway end safety area should provide a cleared and graded area for aeroplanes which the runway is intended to serve in the event of an aeroplane undershooting or overrunning the runway.

Note - The surface of the ground in the runway end safety area does not need to be prepared to the same quality as the runway strip. See, however, 3.1.7.9

Slopes on runway end safety areas

General

3.1.7.6 Recommendation - The slopes of a runway end safety area should be such that no part of the runway end safety area penetrates the approach or take-off climb surface.

Longitudinal slopes

3.1.7.7 Recommendation - The longitudinal slopes of a runway end safety area should not exceed a downward slope of 5per cent. Longitudinal slope changes should be as gradual as practicable and abrupt changes or sudden reversals of slopes avoided.

Transverse slopes

3.1.7.8 Recommendation - The transverse slopes of a runway end safety area should not exceed an upward or downward slope of 5per cent. Transitions between differing slopes should be as gradual as practicable.

Strength of runway end safety areas

3.1.7.9 Recommendation - A runway end safety area should be so prepared or constructed as to reduce the risk of damage to an aeroplane undershooting or overrunning the runway and facilitate the movement of rescue and fire fighting vehicles.