Draft ICAO Circular on NLA.pdf - Airports Council International

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4.1.3.2 The runway end safety area is provided to prevent accidents/incidents due to aircraft
undershooting/overshooting the runway. <strong>ICAO</strong> Accident/Incident Reporting (ADREP) data for the 10 year
period (1987 - 1997) have shown that in the area extending to a distance of 300 m from the runway threshold,
21 per cent of the overrunning aircraft were destroyed while nearly 48 per cent sustained substantial
damages. Collision hazard after runway excursion could be classified as major to catastrophic risk. Hence
the need to provide adequate runway end safety areas, as specified in Annex 14, Volume I.
4.1.3.3 The dimensions of the Runway End Safety Area is dependent on the width of the runway.
According to the requirements in Annex 14, Volume I, this is aircraft size dependent as the minimum
requirement is 120 m (2 x 60 m runway width) for code F aircraft and 90 m (2 x 45 m runway width) for
code E aircraft. In most cases, the width of the runway end safety area is greater than the minimum required
in Annex 14, Volume I.
4.1.4 Taxiway and shoulders
4.1.4.1 Width of straight taxiway
4.1.4.1.1 Annex 14, Volume I, paragraph 3.8.1 specifies that taxiways should be provided to permit
the safe and expeditious surface movement of aircraft. Furthermore paragraph 3.8.3 recommends that the
minimum clearance between outer main wheel and taxiway edge should be at least 4.5 m for code letters D,
E, and F. Additionally, paragraph 3.8.4 specifies that the width of a straight portion of a taxiway should not
be less than:
— 23 m where code letter is E; and
— 25 m where code letter is F
4.1.4.1.2 Guidance material in the Aerodrome Design Manual (Doc 9157), Part 2 indicates in
paragraph 1.2.7 and Table 1-1 the formula for determining the width of a taxiway as follows:
Taxiway width = 2 x clearance distance from wheel to pavement edge plus max. outer main gear wheel span
for the code letter.
Using the above formula, the taxiway width for:
code E: 2 x 4.5 m + 14 m = 23 m; and
code F: 2 x 4.5 m + 16 m = 25 m.
4.1.4.2 Hazard identification and analysis
4.1.4.2.1 The hazard arises from a lateral taxiway excursion on a straight section. The taxiway should
be sufficiently wide to permit smooth traffic flow while facilitating aircraft steering control.
4.1.4.2.2 The causes of a taxiway excursion are:
a) mechanical failure (hydraulic system, brake, nose gear steering);
b) adverse surface conditions (standing water, loss of control on ice-covered surface,
friction coefficient);
<strong>ICAO</strong> Version 4.1 — 15 March 2004