GM1 ADR-DSN.B.015 Number, siting, and orientation of runways

(a)In practice the number and orientation of runways at an aerodrome should normally be such that the usability factor of the aerodrome would normally be not less than 95 % for the aeroplanes that the aerodrome is intended to serve.

(b)Many factors affect the determination of the orientation, siting, and number of runways:

(1)The wind distribution (to minimise crosswinds liable to affect runways);

(i)Wind statistics used for the calculation of the usability factor are normally available in ranges of speed and direction, and the accuracy of the results obtained depends, to a large extent, on the assumed distribution of observations within these ranges. In the absence of any sure information as to the true distribution, it is usual to assume a uniform distribution since, in relation to the most favourable runway orientations, this generally results in a slightly conservative usability factor.

(ii)The maximum mean crosswind components given in GM1 ADR-DSN.B.020, refer to normal circumstances. There are some factors which may require that a reduction of those maximum values be taken into account at a particular aerodrome. These include: A. the wide variations which may exist, in handling characteristics and maximum permissible crosswind components, among diverse types of aeroplanes (including future types) within each of the three groups given in GM1 ADR-DSN.B.020; B. prevalence and nature of gusts; C. prevalence and nature of turbulence; D. the availability of a secondary runway; E. the width of runways; F. the runway surface conditions — water, snow, and ice on the runway materially reduce the allowable crosswind component; and G. the strength of the wind associated with the limiting crosswind component.

(2)The need to facilitate the provision of approaches conforming to the approach surface specifications, ensuring that obstacles in these areas or other factors should not restrict the operation of the aeroplanes for which the runway is intended. This may relate to individual obstacles or local geography (e.g. high ground) .

(3)The need to minimise interference with areas approved for residential use and other noise-sensitive areas close to the aerodrome.

(4)The need to avoid the turbulence impacts of buildings on or close to the aerodrome.

(5)Type of operation. Attention should be paid in particular to whether the aerodrome is to be used in all meteorological conditions or only in visual meteorological conditions, and whether it is intended for use by day and night, or only by day.

(6)Topography of the aerodrome site, its approaches, and surroundings, particularly:

(i)compliance with the obstacle limitation surfaces;

(ii)current and future land use. The orientation and layout should be selected so as to protect as far as possible, the particularly sensitive areas, such as residential, school and hospital zones, from the discomfort caused by aircraft noise. Detailed information on this topic is provided in ICAO Doc 9184, Airport Planning Manual, Part 2, Land Use and Environmental Control and in ICAO Doc 9829, Guidance on the Balanced Approach to Aircraft Noise Management;

(iii)current and future runway lengths to be provided;

(iv)construction costs; and

(v)possibility of installing suitable non-visual and visual aids for approach-to-land.

(7)Air traffic in the vicinity of the aerodrome, particularly:

(i)proximity of other aerodromes or ATS routes;

(ii)traffic density; and

(iii)air traffic control and missed approach procedures.

(c)The number of runways to be provided in each direction depends on the number of aircraft movements to be catered for.

(d)Whatever the factors that determine the runway orientation, the siting, and orientation of runways at an aerodrome should where possible, be such that safety is optimised.

(e)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 in CS ADR-DSN.H.425. Further guidance on these and other factors is given in ICAO Annex 14, Attachment A, Section 1. When a new instrument runway is being located, particular attention needs to be given to areas over which aeroplanes should be required to fly when following instrument approach and missed approach procedures so as to ensure that obstacles in these areas or other factors should not restrict the operation of the aeroplanes for which the runway is intended.

(f)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 of time 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.

[Issue: ADR-DSN/3]

[Issue: ADR-DSN/4]