Draft ICAO Circular on NLA.pdf - Airports Council International

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4) Weather conditions (Heavy rain, cross wind, strong/gusty winds, visibility); and
5) Human factors (crew, maintenance, balance, payload security).
b) for landing:
1) Aircraft (malfunctioning of landing gear, control surfaces, hydraulic system, brakes,
tires, nose gear steering);
2) Power plant (reverse and thrust lever linkage);
3) Surface conditions (standing water, snow, runway friction coefficient);
4) Weather conditions (Heavy rain, cross wind, strong/gusty winds,
thunderstorms/wind shear, visibility);
5) ILS localizer signal quality/interference; and
6) Human factors (hard landings, crew, maintenance).
4.1.2.2.3 An analysis of lateral runway excursion reports shows that accident mechanisms are not the
same for take-off and for landing. Mechanical failures are, for instance, a frequent accident factor for
excursion during take-off, while bad weather conditions are more often associated with landing incidents.
Engine reverse thrust system malfunction has also been a factor in a significant number of landing veer-offs
(see Appendix B).
4.1.2.2.4 Lateral runway excursion hazard could be classified as major to catastrophic risk depending
on the aircraft speed. According to the available reports, there were no code E aircraft fatal accidents due
to runway excursion alone reported from 1980 to 2000.
4.1.2.2.5 A review of this accident/incident database also revealed that only 1.3 per cent of the total
number of on-board fatalities from 1980 to 1998 occurred after lateral runway excursions. However, it should
be noted that a large percentage of excursions result in serious damage or operational implications.
4.1.2.3 Risk assessment and possible mitigation measures
4.1.2.3.1 The lateral runway excursion risk is clearly linked to specific aircraft characteristics,
performance/handling qualities, controllability in response to such events as aircraft mechanical failures,
pavement contamination and cross-wind conditions. This type of risk comes under the category for which
risk assessment is mainly based on aircraft performance and handling qualities. Aircraft type certification
is one of the key factors to be considered in order to ensure that this risk is under control.
4.1.2.3.2 For use of runways narrower than the 60 m width recommended by Annex 14, Volume I,
all factors affecting safety should be taken into account including the certification of the specific aircraft type
and local conditions 2 . The approval of the appropriate authority should be sought. Possible mitigation
2 Attention should be given to the crosswind performance of the aircraft on various runway surface conditions
<strong>ICAO</strong> Version 4.1 — 15 March 2004