Draft ICAO Circular on NLA.pdf - Airports Council International

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4.1.6.7.2 A review of commonly used databases reveals that information relative to collision on
taxiing is limited as few such incidents have been recorded as serious incidents. However, the causes of such
an event could be classified as:
a) mechanical failure (hydraulic system, brake, nose gear steering);
b) surface conditions (standing water, loss of control on ice-covered surface, friction
coefficient);
c) loss of visual taxiway guidance system (markings and lights covered by snow); and
d) human factors (directional control, temporary loss of orientation, etc.).
4.1.6.7.3 Consequences of collision on taxiing are potentially major.
4.1.6.8 Risk assessment and possible mitigation measures
4.1.6.8.1 Operational experience of existing code E aeroplanes, under favourable conditions, shows
that deviations do not increase with aeroplane size. It is therefore expected that taxiway deviations by NLA
will not be significantly different from code E aeroplanes. This has yet to be confirmed by actual operational
experience with NLAs. That is why the permissible deviation of code F aeroplanes in Annex 14, Volume I,
paragraph 3.8.3 is the same as for code E aeroplanes.
4.1.6.8.2 Taxiway deviation statistics may be used to assess the collision risk between two aircraft or
between an aircraft and an object. Several taxiway deviation studies are available or in progress on different
aerodromes world-wide (JFK, ANC, AMS, LHR, CDG, FRA & SYD. Final reports are expected in 2004).
4.1.6.8.3 Possible mitigation measures for operation of NLA on taxiways which do not meet the
taxiway minimum separation distances specified in Annex 14, Volume I, Table 3-1 for code F are:
a) reduced taxiing speed;
b) provision of taxiway centre line lights;
c) provision of taxi side stripe markings (and taxiway edge lights);
d) special taxi routing for new larger aeroplanes;
e) restrictions on aircraft (wing span) allowed to use parallel taxiways during NLA
operations;
f) restrictions on vehicles using service roads adjacent to a designated new larger
aeroplane route;
g) use of “follow me” guidance; and
h) reduced spacing between taxiway centre line lights.
<strong>ICAO</strong> Version 4.1 — 15 March 2004